La entrada Principios De Radiacion Con Tomografia De Haz Conico CBCT se publicó primero en Kadi México.

ESPRODEN Índice
índice
1 Introducción 5
2 Utilizacion De Los Sistemas Ct 15
2.1 Implantología. Estudio Previo
2.2 Implantología. Control Final
2.3 Periodoncia
2.4 Tecnología Aplicada
3 Ventajas De Los Sistemas Ct 19
3.1 Seguridad En El Diagnóstico
3.2 Control Del Resultado
3.3 Confianza Del Paciente
3.4 Imagen “High-Tech”
3.5 Exención De Riesgos
3.6 Servicio
3.7 Rentabilidad
3.8 Lugar De Instalación
3.9 Transmisión De Datos
4 Propuesta De Modelos 30
5
25
ESPRODEN
EXPERIENCIA CLÍNICA:
TOMOGRAFÍA COMPUTERIZADA (CBCT 3D)
En la práctica dental, ninguna modalidad ha conocido un impacto tan
rápido e importante en los tratamientos, como la CBCT.
Sin duda, esta tecnología va a cambiar la actitud de los dentistas frente
a muchos tratamientos. Los resultados tridimensionales aparecen superiores respecto a la visualización de la anatomía, para muchos aspectos del
implante preoperatorio y de la cirugía dental, así como de la previsión de
la intervención.
Esta excelente tecnología, que todavía no para de evolucionar, mejorará el
tratamiento del paciente: se reducirá el riesgo operatorio y los tratamientos
complejos, así como los implantes dentales resultarán mucho menos complicados. El desarrollo de esta tecnología va a mejorar de manera decisiva el
tratamiento del paciente, es decir, el objetivo principal de nuestra profesión.
La reciente introducción de la Tomografía Computerizada Volumétrica
(CBCT) en la profesión dental ha resuelto muchos problemas relacionados
con los escáneres CT tradicionales.
La tecnología CBCT crea imágenes tridimensionales de las estructuras
dentales a través de un Haz de Rx cónico (cone beam) que se desplaza en
torno a la cabeza del paciente en un tiempo seleccionado, 24 segundos.
Se utiliza un detector Flat-Panel para capturar cada ½ grado de proyección y obtener así una traducción computerizada tridimensional de la
región anatómica deseada.
La tecnología CBCT utiliza 10 veces menos radiación que los sistemas CT
(TAC) tradicionales, y genera imágenes 10 veces más precisas.
Introducción
1INTRODUCCIÓN
6 Implementación de Sistemas “CT”
25
ESPRODEN
Las imágenes en 3D con Haz Cónico proporcionan una clara información
anatómica, en estructura oral y maxilo facial.
CT CON HAZ CÓNICO (CONE BEAM)
Aplicación con
Tecnología de Haz
Cónico en nueva
generación
Beneficios: Menor Coste + Menor Radiación
TAC
Varios minutos Sólo de 15 a 24 segundos
CBCT
7
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ESPRODEN
Radiografía
Imagen obtenida sin movimiento de ningún elemento; Emisor-ObjetoDetector.
Tomografía
Imagen obtenida mediante el movimiento del conjunto Emisor-Detector,
estando inmóvil el Objeto.
Emisor y Detector móviles, objeto inmóvil.
Introducción
Técnica de radiografía
de mano Imagen obtenida
Emisor y Detector se mueven en direcciones opuestas Solo la zona de enfoque
aparece
8 Implementación de Sistemas “CT”
25
ESPRODEN
Existen diversos tipos de tomógrafos, dependiendo de su movimiento.
Emisor y Detector se mueven en direcciones opuestas.
TOMÓGRAFO
Tomógrafo Lineal para su uso en cráneo, permite hacer cortes:
• Sagital
• Transversal (coronal)
• Horizontal (axial)
• Especiales
Emisor y Detector se mueven en direcciones opuestas.
Lineal Circular Elipsoidal Hipocicloidal Espiral
Implementación de Sistemas “CT” 9
25
ESPRODEN
TOMOGRAFÍA: LINEAL
Situación de los Ejes o planos
Emisor y Detector se mueven en direcciones opuestas.
En sus inicios, el TAC sólo se utilizaba para el cráneo, posteriormente se
ampliaron para el resto del cuerpo.
Sagital
Parte anterior
o posterior
del paciente
Axial
(horizontal) Coronal
(transversal)
Primer TAC de Siemens
Siretom en1974.
Tiempo de adquisición
de información por corte
de 7 minutos.
Resolución de imagen
80×80 pixels.
10 Implementación de Sistemas “CT”
25
ESPRODEN
En la Radiología Digital, los diversos sensores, utilizados como Detectores, son diferentes según su uso y sus componentes son distintos:
PRIMER TAC TAC ACTUAL
Pixel Voxel
Para radiología plana;
sólo tienen dos dimensiones
Para poder generar una
imagen volumétrica, los
sensores tienen una diversa construcción; su
unidad más pequeña se
llama VOXEL
Implementación de Sistemas “CT” 11
25
ESPRODEN
Aparece Una nueva tecnología: el sistema CBCT (Tomografía Computerizada de Haz Cónico).
Sensor plano
• Escaneo en 3D en una sola rotación
• Los algoritmos de reconstrucción son complejos y necesitan tiempo
• Para objetos de diversos tamaños
• Adaptado por E-Woo tech
Diferencias entre TAC convencional y sistemas CBCT de E-WOO:
• Funcionamiento: Dósis
De 1.500 μSv a 3.000 μSv De 20 μSv a 65 μSv
TAC
1 TAC= 75 CBCT
CBCT
12 Implementación de Sistemas “CT”
25
ESPRODEN
Ejemplos:
• Panorámica convencional 15/25 μSv
• Panorámica digital 5/15 μSv
• Serie de boca 150 μSv
• Ambiente 8 μSv
• TAC 1.200/3.000 μSv
Densidad obtenida por los sistemas TAC convencional y sistemas CBCT
de E-WOO:
• Unidad de medida: Números CT o números Hounsfield
ELEMENTO UNIDADES HU
Hueso Cortical 800-1000
Hueso esponjoso 100-300
Musculo 40-50
Riñones 40-50
Agua 0
Grasa -80 a -100
Aire -1000
13
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ESPRODEN Introducción
FLAT PANEL (PANEL PLANO) VS II CCD
Numero de “bits” (escalas de grises) en la Calidad de la Imagen.
12 bits (212 = 4,096 niveles de grises) es 16 veces mayor (mejor calidad de
imagen), comparada con datos a 8 bits (28
= 256 niveles).
14 Implementación de Sistemas “CT”
25
ESPRODEN
CT DENTAL DE VATECH
¿FOV (ÁREA DE VISIÓN)?
15
25
ESPRODEN Utilización de los Sistemas CT
2.1 IMPLANTOLOGÍA. ESTUDIO PREVIO
La preparación de la cirugía implantológica es básica para el éxito de la
misma.
Se debe determinar:
1º El modelo de implante.
2º El posicionamiento adecuado del mismo.
Para ello, es imprescindible:
1º Medir las distancias precisas.
2º Comprobar la densidad ósea.
3º Determinar la situación de senos y/o canal mandibular.
El resultado será:
1. Poder comunicar al paciente el resultado del estudio.
2. Asegurar el tratamiento a seguir.
2.2 Implantología. Control final
Al finalizar la intervención, es absolutamente recomendable realizar un
control.
Se comprueba:
1º La posición definitiva del implante.
2º Las distancias al canal mandibular y/o senos, comprobando que dichas distancias sean seguras.
Se obtiene:
1º En caso de alguna anomalía, efectuar una acción correctiva precoz.
2º Una mayor satisfacción del paciente, al poder realizar una comprobación de la calidad del tratamiento.
2 UTILIZACION DE LOS SISTEMAS CT
16 Implementación de Sistemas “CT”
25
ESPRODEN
2.3 Periodoncia
Una sola exploración, mediante CT, permite una visión completa de la
arcada permitiendo la visión de:
1. Bolsas periodontales.
2. Sarro
3. Retracción de masa ósea
Además, se evitan las series de radiografías, obteniendo:
1. Menor radiación para el paciente.
2. Más seguridad en la visualización en 3D.
2.4 Tecnología aplicada
Case Western Reserve University
La tomografía computerizada CBCT es hoy en día la tecnología más innovadora que los dentistas utilizan para diagnosticar complicados problemas de salud dental.
“La incorporación, tan deseada, de la tecnología tridimensional en la
elaboración radiográfica es, por fin, una realidad. Todavía se puede mejorar, sin embargo, la tecnología CBCT es algo que va a durar mucho tiempo”. (J. Martin Palomo y Mark Hans del Departamento de Ortodoncia de la
Escuela de Medicina Dental de la Case Western Reserve University y C. H.
Kau e S. Richmond del Departamento de Salud dental y Ciencias biológicas
del College of Medicine de la Universidad de Gales).
El prototipo de visualizador CT realizado en 1967 ya ha llegado a su sexta
generación, con imágenes mejores y más enfocadas y menor exposición a
las radiaciones para los pacientes. Los escáneres de primera generación
sólo sacaban imágenes parciales. La última generación de escáneres CBCT
ofrece una variedad de imágenes para ofrecer una visión completa en tres
dimensiones de la estructura de la boca.
Ventajas de la tecnología aplicada:
1º La nueva tecnología permite elaborar una vasta gama de imágenes en
menos de un minuto (24 segundos), reduciendo al 20 % la exposición a las
radiaciones respeto a los sistemas tradicionales.
17
25
ESPRODEN Utilización de los Sistemas CT
2º La definición de las imágenes es tan elevada que es posible captar un
corazón que late.
3º La tecnología respeta las reglas elaboradas por la Asociación Dental
Americana y la Sociedad de Ortodoncia Británica para reducir la exposición
a las radiaciones.
4º La nueva tecnología permite captar imágenes tridimensionales mucho
más precisas, así que se pueden detectar con mayor facilidad anomalías
orales (quistes, dientes sepultados, etc).
5º Las imágenes mejoradas permiten análisis más eficaces de los conductos de aire y de tratamiento de las condiciones relacionadas con la apnea y con el adenoide ensanchado.
6º Las imágenes creadas por la tecnología CBCT se pueden utilizar también en la realización de nuevos implantes, cuyo empleo resulta cada vez
más importante.

19
25
ESPRODEN Ventajas de los Sistemas CT
La imagen panorámica, al ser una proyección en 2 dimensiones, no permite:
1º Efectuar mediciones precisas. Magnificación variable, posicionamiento, etc.
2º Ver la situación de las piezas en su profundidad.
3º Ver la situación del seno, relativo a la zona de implante.
4º Apreciar la densidad ósea.
5º Determinar el espesor y anatomía de la mandíbula.
3 VENTAJAS DE LOS SISTEMAS CT
La utilización del sistema
CT nos permite mayor
definición para ver:
Nervio
alveolar
Senos
maxilares
PANORÁMICO
PERIAPICAL
TOMOGRAFIA
COMPUTERIZADA
++ ++
+ +
++++ ++++
La utilización del sistema
CT nos permite mayor
definición por:
La utilización del sistema
CT nos permite mayor
definición para ver:
Distorsión
media
Máxima
distorsión
Espesor
óseo
Densidad
ósea
PANORÁMICO
PERIAPICAL
TOMOGRAFIA
COMPUTERIZADA
3.0 mm 7.5 mm – –
1.0 mm 5.5 mm – –
0.2 mm 0.5 mm ++++ ++++
20 Implementación de Sistemas “CT”
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ESPRODEN
CT para la determinación preoperatoria
del lugar apto para implantes
Dr. David C. Hatcher
La planificación de implantes necesita datos muy específicos y precisos.
Siempre se han utilizado imágenes a ese fin, pero hasta la reciente introducción de escáneres CBCT la calidad de las imágenes era baja en relación al
potencial diagnóstico, al coste del estudio y al riesgo para el paciente. El
uso de escáneres CBCT para obtener imágenes maxilofaciales se ha convertido en uno de los instrumentos más importantes en el proceso de planificación de implantes dentales.
Los escáneres CBCT son sencillos de utilizar y producen una imagen
tridimensional que puede ser elaborada con un software apto para la visualización personalizada de la anatomía. También existen protocolos para
optimizar la resolución de las imágenes.
Las imágenes anteriores se refieren a un
varón de 25 años con ausencia congénita
de bicúspide mandibular. Se están investigando las áreas más aptas para el implante. Las radiografías clínicas sugieren que
hay suficiente volumen de hueso alveolar
como para poner implantes. Sin embargo,
las imágenes tridimensionales elaboradas
por la tecnología CBCT indican que la ancha concavidad lingual podría constituir
un obstáculo importante.
21
25
ESPRODEN Ventajas de los Sistemas CT
Estas imágenes se refieren a una mujer de 17 años con ausencia congénita de incisivos laterales. La radiología intenta determinar el sitio más apto
para un implante. Se han puesto marcadores de metal para verificar lo que
pasaría en el caso de una intervención. La tecnología CBCT puede ser utilizada para determinar si la intervención planeada es la mejor en relación a
la conformación de la mandíbula.
Este es el caso de un varón de 56 años a quien le faltan los dientes números 8 y 9. Se han puesto dientes opacos para simular la posición y el tamaño
deseados. Un hueco a lo largo del eje del diente identifica la trayectoria
que va a seguir el implante.
Ese sistema se puede emplear para la radiología de planificación y para
transferir el producto planeado a la boca del paciente.
Las siguientes imágenes pertenecen a una mujer de 19 años que perdió de forma traumática los dientes del 7 al 10. Con una planificación de
tipo tradicional, las informaciones estarían limitadas al sitio del implante, sin
embargo, con la tecnología CBCT hay más información disponible, incluso
sobre la oclusión opuesta y las articulaciones temporo-mandibulares.
22 Implementación de Sistemas “CT”
25
ESPRODEN
La evaluación de estas últimas indica un problema degenerativo de la
articulación en la parte izquierda, y una dislocación debida a una fractura
en el lado derecho.
Las imágenes tridimensionales producidas por la tecnología CBCT ofrecen relevante información adicional en la planificación de implantes, lo que
resulta ideal para este fin.
El sistema CBCT es una modalidad de visualización maxilofacial que permite obtener información rentable para mejorar el conjunto de la intervención en la sustitución de dientes por implantes.
Gracias a CBCT el dentista ya puede verificar adecuadamente el sitio
para el implante.
Cuando el campo de las imágenes se extiende a la oclusión, las relaciones espaciales máxilo-mandibulares y la articulación temporo-mandibular,
la tecnología CBCT es la mejor solución. Asimismo permite detectar otros
factores que puedan constituir un riesgo para la eficacia del implante y la
seguridad del paciente.
Con el actual desarrollo de los programas informáticos relacionados con
la tecnología CBCT, hoy, ya podemos disponer de un módulo 3D.
Este modelo tridimensional permite el diagnóstico de implantes, la planificación del tratamiento, su simulación y las operaciones de cirugía sustitutiva.
23
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ESPRODEN Ventajas de los Sistemas CT
3.1 Seguridad en el diagnóstico
Una sola exploración, mediante CT, nos ofrece una visión completa de la
arcada permitiendo las siguientes apreciaciones:
1º Realizar mediciones precisas, sin distorsión, en cualquier dirección.
2º Ver perfectamente el espacio disponible para el implante.
24 Implementación de Sistemas “CT”
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ESPRODEN
3º Realizar cortes tomográficos precisos y sucesivos, prácticamente sin
limitación.
4º Alcanzar el control de toda la zona de interés.
5º Observar una zona de interés, desde cualquier ángulo.
25
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ESPRODEN Ventajas de los Sistemas CT
3.2 Control del resultado
Control final del perfecto posicionamiento del implante.
Caso en el que se tuvo que añadir hueso en el seno lateral.
3.3 Confianza del paciente
1. Recibe el máximo de información.
2. Entiende el tratamiento a efectuar.
3. Coopera en la decisión.
4. Difícilmente, tras ver las imágenes en 2D y 3D, tendrá dudas sobre
el tratamiento propuesto.
5. Tras el tratamiento, comprueba el resultado final.
6. Máxima tecnología para “su” caso específico.
26 Implementación de Sistemas “CT”
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ESPRODEN
3.4 Imagen “high-tech”
La utilización de sistemas informáticos de alto nivel, la imagen en 3D y
el diseño de la máquina, genera confianza por el uso de la más “Alta Tecnología”.
27
25
ESPRODEN Ventajas de los Sistemas CT
3.5 Exención de riesgos
1. La garantía de utilizar los mejores sistemas de Diagnóstico por la Imagen, dan como resultado la ausencia total de errores para los diagnósticos.
2. Los errores y fracasos, se minimizan.
3. Manteniendo un archivo de los estudios de CT, tanto el inicial como
el de control final, se tiene la tranquilidad de demostrar la calidad del
tratamiento.
4. Debido a la tranquilidad y confianza del paciente, es difícil llegar a una
situación de reclamación ya que ha sido co-participe en la toma de
decisiones.
3.6 Servicio
1. Tomografía Computerizada.
2. Imágenes Tridimensionales.
3. Manipulación de las imágenes por el profesional, en la propia Clínica.
4. Colaboración del paciente para seleccionar el mejor tratamiento
5. Garantía de calidad de los tratamientos
Todos estos elementos son necesarios para ofrecer el máximo de:
“CALIDAD Y SERVICIO PARA EL PACIENTE”
3.7 Rentabilidad
El uso de aparatología avanzada en las Clínicas Dentales privadas para
el Diagnóstico por la Imagen, ha ido siempre precedida de su instalación
en Centros Radiológicos, tal vez por el temor a la rentabilidad de estos
aparatos.
Siempre fue un temor infundado, ya que la rentabilidad diagnóstica de
servicio y económica es un hecho.
Los sistemas CT o TAC se utilizan desde hace muchos años en Radiología. Las Clínicas Dentales se sirven de ellos para los estudios de implantes,
aumentando sus solicitudes día a día.
28 Implementación de Sistemas “CT”
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ESPRODEN
La complejidad de los tratamientos nos obligan a dar respuesta, con
garantía de seguridad, a las exigencias y necesidades del paciente.
La incorporación de los Sistemas CT en las Clínicas Dentales, es ya un
hecho.
3.8 Lugar de instalación
El sistema puede instalarse en:
1º Centro independiente que requiere:
• Local adecuado
• Personal cualificado
• Sistema ECT 12 con FOV 12×7 cm
2º La clínica que disponga de:
• Espacio suficiente
• Sistema ECT 12 con FOV 12×7 cm
3.9 Transmisión de datos
Junto con los sistemas se sirve el Software EzImplant, permitiendo la
visualización y el tratamiento de los estudios.
Las exploraciones efectuadas se pueden enviar a las Clínicas, en diversos
formatos:
 Estudio completo con visor incorporado.
• El visor de Ezlmplant le permite tratar de forma personalizada
todo el estudio.
 Solo imágenes seleccionadas: Actualmente es el sistema más
difundido.
• En formato informático o placas radiográficas.
• En el caso de placas radiográficas, es necesario disponer de
una impresora de alta calidad.
• En formato informático, la Clínica puede ver las imágenes con
visor de Windows o programas de tratamiento de imágenes.
• No requiere personal “especializado”.
29
25
ESPRODEN Ventajas de los Sistemas CT
Una vez determinado el formato a utilizar con cada Clínica, se envía el
estudio por los siguientes medios:
 Placas:
• Entregándolo al paciente, en mano.
• Posteriormente, por mensajero.
 Imágenes seleccionadas, en formato informático:
• En CD-ROM, entregado en mano al paciente.
• En CD-ROM, posteriormente, por mensajero.
• Via e-mail, directamente a la Clínica.
• Cargándolo en un servidor ftp, la Clínica los recupera directamente.
 Estudio completo con visor Ezlmplant:
• En CD-ROM, entregado en mano al paciente.
• En CD-ROM, posteriormente, por mensajero.
30 Implementación de Sistemas “CT”
25
ESPRODEN
4 PROPUESTA DE MODELOS
MODELO PICASSO PRO
• EXPLORACIONES C.T.
• FLAT PANEL
• FOV de 12 x 7 cm
• VOXEL min. 0,1 mm.
• POSICIONAMIENTO: SENTADO
• Movimiento vertical motorizado del sillón
31
25
ESPRODEN Propuestas de Modelos
MODELO PICASSO TRIO
• EXPLORACIONES: CT + PANO + TELE
• FLAT PLANEL, PARA CT
• VOXEL: min. 0,1 mm.
• FOV DE 12 X 7 cm
• POSICIONAMIENTO: ERGUIDO
• MOVIMIENTO VERTICAL MOTORIZADO
32 Implementación de Sistemas “CT”
25
ESPRODEN
NECESIDADES PARA SU INSTALACION
Principio de operación:
• Sistema controlado por Consola PC
• Comandos de control enviados por puerto serie
• Imágenes desde sensor Flat Panel, por cable LVDS 80 pin, a Frame
Grabber
Comunicación Serie
Normalmente COM3
Comunicación Ethernet
Sólo Sensor Pano/Ceph
Puestos de Trabajo (Esay Dent / EzImplant)
80 pin LVDS
Picasso Trio, Picasso Pro
(Picasso Máster: comunicación por fibra óptica)
Consola
Software:
• Easy Dent
• EzPax
• EzImplant
• Hasp Key
Base de imágenes
Base de pacientes
Comunicación
33
25
ESPRODEN Propuestas de Modelos
Consola
Imágenes Datos del paciente
Imágen original
1º Programa de captura
2º Reconstrucción
Caracteristicas Vatech & Woo
PICASSO
TRIO
PICASSO
PRO
PICASSO
MASTER
PROYECCIONES
FOV
SENSOR
VOXEL SIZE
ROTACIÓN
IMÁGENES
POSICIONAMIENTO
VISOR PARA DRS.
PAN+CEPH+CT CT CT
12 x 7 cm 12 x 7 cm 20×15 / 20×19 cm
FLAT PANEL + CCD FLAT PANEL FLAT PANEL
Desde 0,1 mm
(Normal 0,2 mm)
360º
720 (420)
Erguido
SI SI SI
Sentado Sentado
720 (420) 720 (420)
360º 360º
Desde 0,1 mm
(Normal 0,2 mm)
Desde 0,1 mm
(Normal 0,3 mm)

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La entrada Implementacion Sistemas CT se publicó primero en Kadi México.

Pearson
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Essentials of Dental Radiography
for Dental Assistants and Hygienists
NINTH EDITION
Evelyn M. Thomson, BSDH, MS
Adjunct Assistant Professor
Gene W. Hirschfeld School of Dental Hygiene
Old Dominion University
Norfolk, Virginia
Orlen N. Johnson, BS, DDS, MS
College of Dentistry
University of Nebraska Medical Center
Lincoln, Nebraska
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ISBN-10: 0-13-801939-8
Library of Congress Cataloging-in-Publication Data
Cataloging-in-Publication data on file with the Library
of Congress.
To my husband, Hu Odom, once again your loving patience,
support, and encouragement gets me through.
—Evie
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Contents
Preface ix
Acknowledgments xi
Reviewers xii
PART I: Historical Perspective and Radiation Basics 1
Chapter 1 History of Dental Radiography 1
Chapter 2 Characteristics and Measurement
of Radiation 8
Chapter 3 The Dental X-ray Machine: Components
and Functions 20
Chapter 4 Producing Quality Radiographs 32
PART II: Biological Effects of Radiation and Radiation Protection 47
Chapter 5 Effects of Radiation Exposure 47
Chapter 6 Radiation Protection 57
PART III: Dental X-ray Image Receptors and Film Processing
Techniques 74
Chapter 7 Dental X-ray Film 74
Chapter 8 Dental X-ray Film Processing 83
Chapter 9 Digital Radiography 97
PART IV: Dental Radiographer Fundamentals 114
Chapter 10 Infection Control 114
Chapter 11 Legal and Ethical Responsibilities 131
Chapter 12 Patient Relations and Education 138
PART V: Intraoral Techniques 147
Chapter 13 Intraoral Radiographic Procedures 147
Chapter 14 The Periapical Examination—Paralleling Technique 161
Chapter 15 The Periapical Examination—Bisecting Technique 179
Chapter 16 The Bitewing Examination 196
Chapter 17 The Occlusal Examination 215
vii
PART VI: Radiographic Errors and Quality Assurance 227
Chapter 18 Identifying and Correcting Undiagnostic Radiographs 227
Chapter 19 Quality Assurance in Dental Radiography 241
Chapter 20 Safety and Environmental Responsibilities
in Dental Radiography 251
PART VII: Mounting and Viewing Dental Radiographs 264
Chapter 21 Mounting and Introduction to Interpretation 264
Chapter 22 Recognizing Normal Radiographic Anatomy 273
Chapter 23 Recognizing Deviations from Normal Radiographic
Anatomy 289
Chapter 24 The Use of Radiographs in the Detection of Dental
Caries 303
Chapter 25 The Use of Radiographs in the Evaluation of Periodontal
Diseases 314
PART VIII: Patient Management and Supplemental Techniques 325
Chapter 26 Radiographic Techniques for Children 325
Chapter 27 Managing Patients with Special Needs 340
Chapter 28 Supplemental Radiographic Techniques 350
PART IX: Extraoral Techniques 364
Chapter 29 Extraoral Radiography and Alternate Imaging
Modalities 364
Chapter 30 Panoramic Radiography 377
Answers to Study Questions 403
Glossary 407
Index 423
viii CONTENTS
Preface
The study of oral radiological principles and the practice of oral radiography techniques require an understanding of theoretical concepts and a mastery of the skills needed to apply these concepts. Essentials of
Dental Radiography for Dental Assistants and Hygienists provides the student with a clear link between
theory and practice. Straightforward and well balanced, Essentials of Dental Radiography for Dental
Assistants and Hygienists provides in-depth, comprehensive information that is appropriate for an introductory course in dental radiography, without overwhelming the student with nonessential information. It
is comprehensive to prepare students for board and licensing examinations and, at the same time, practical, with practice points, procedure boxes, and suggested lab activities that prepare students to apply theory to clinical practice and patient management.
True to its title, Essentials of Dental Radiography for Dental Assistants and Hygienists clearly
demonstrates its ability to explain concepts that both dental assistants and dental hygienists must know.
The examples and case studies used throughout the book include situations that pertain to the roles of both
dental assistants and dental hygienists as members of the oral health care team.
Essentials of Dental Radiography for Dental Assistants and Hygienists is student-friendly, beginning
each chapter with learning objectives from both the knowledge and the application levels. Each objective
is tested by study questions presented at the end of the chapter, allowing the student to assess learning outcomes. The objectives and study questions are written in the same order that the material appears in the
chapter, guiding the student through assimilation of the chapter content. Key words are listed at the beginning of each chapter and bolded within the text with their definitions, and realistic rationales for learning
the material are presented in each chapter introduction. The chapter outline provides a ready reference to
locate the topics covered. Meaningful case studies relate directly to radiological applications presented in
the chapter and challenge students to apply the knowledge learned in the reading to real-life situations
through decision-making activities.
The thirty chapters of the ninth edition are organized into nine topic sections.
• Historical Perspective and Radiation Basics
• Biological Effects of Radiation and Radiation Protection
• Dental X-ray Image Receptors and Processing Techniques
• Dental Radiographer Fundamentals
• Intraoral Techniques
• Radiographic Errors and Quality Assurance
• Mounting and Viewing Dental Radiographs
• Patient Management and Supplemental Techniques
• Extraoral Techniques
Educators can easily utilize the chapters and topic sections in any order and have the option to tailor
what material is covered in their courses. The sequencing of material for presentation in this text begins
with the basics of radiation physics, biological effects, and protection to give the student the necessary
background to operate safely, followed by a description of the radiographic equipment, film and film processing, and digital image receptors to help the student understand how radiation is utilized for diagnostic
purposes. Prior to learning radiographic techniques, the student will study the fundamentals of infection
control, legal and ethical responsibilities, and patient relations. The student will then be prepared to begin
to practice the intraoral technique skills necessary to produce diagnostic-quality periapical, bitewing, and
occlusal radiographs and learn to mount, evaluate, and interpret the images. Following the interpretation
chapters, the student will now possess the basic skills of intraoral radiography and is ready to grasp supplemental techniques and alterations of these basic skills by studying management of special patients and
extraoral and panoramic techniques.
ix
Changes made to this ninth edition represent educators’ requests for an up-to-date book that speaks
to both dental assisting and dental hygiene students, provides comprehensive information without overwhelming the student with nonessential details, and is student centered. Outstanding features of this edition include the following:
• Integration of digital imaging where appropriate throughout the text. Film-based imaging is an
established standard of care, and licensing board examinations continue to require oral health
care professionals to demonstrate a working knowledge of the use of film-based radiography.
However, digital imaging has become an integral part of oral health care practice. For this reason,
the all-encompassing term image receptor is used to allow educators the option to teach the use of
film, solid-state digital sensors, or photostimuable phosphor plate technology. Additionally the
chapter on digital imaging has been moved from the section on supplemental techniques to a
position earlier in the book to assist with integration of this technology as the student learns the
basics of radiography.
• The paralleling and bisecting techniques have been separated into their own chapters to provide distinct lessons for the student. Teaching strategies suggest that introducing two similar, but difficult,
concepts together may impede learning either technique well. Placing these two important radiographic techniques into their own chapters will allow the educator to assign one or the other in any
order and at distinctly different times in the curriculum.
• The addition of the chapter on safety and environmental responsibilities in radiography is in
response to the awareness of the ecological impact of oral health practice today. Students should be
trained in the safe handling and environmentally sound disposal of potentially hazardous materials
and chemicals used in radiography.
• Update on extraoral radiography and alternate imaging modalities. It is beyond the scope of this
book to teach extraoral maxillofacial imaging to competency, and many oral health care professionals who may be called on to utilize these techniques will most likely require additional training.
Therefore, the information on the seven common techniques was condensed to key points and
placed into a table that enhances learning without overwhelming the student. This chapter now
builds on the students’ knowledge of digital imaging with an introduction to cone beam computed
tomography (CBCT), purported to become the standard of care for periodontal implant assessment
in the future.
• Each chapter was critically evaluated to update material, add new study questions, redraw complex
illustrations, and include new images, all to enhance student comprehension.
• Each of the 30 chapters in the ninth edition continues to provide Procedure Boxes, which highlight
and simplify critical steps of radiographic procedures and serve as a handy reference when providing radiographic services in a clinical setting; Practice Points, which call student attention to possible use of theory in real-life situations, providing a “mental break” from studying theory by
illustrating how that theory is applied; and Case Studies and activities for possible lab exercises,
research outside class time, essay writing, and investigation using the Internet.
The focus of the ninth edition of Essentials of Dental Radiography for Dental Assistants and
Hygienists is on the individual responsibility of the oral radiographer and conveys to the reader the
importance of understanding what ionizing radiation is and what it is not; protecting oneself, the patient,
and the oral health care team from unnecessary radiation exposure; practicing within the scope of the
law and ethically treating all patients; producing diagnostic-quality radiographs and appropriately correcting errors that diminish radiographic quality; knowing when and how to apply supplemental techniques; and assisting in the interpretation of radiographs for the benefit of the patient.
Whereas Essentials of Dental Radiography for Dental Assistants and Hygienists is written primarily for dental assisting and dental hygiene students, practicing dental assistants, dental hygienists, and
dentists may also find this book to be a helpful reference, particularly when preparing for a relicensing
examination in another jurisdiction. Additionally, Essentials of Dental Radiography for Dental Assistants and Hygienists may be a valuable study guide for on-the-job-trained oral health care professionals
who may be seeking radiation safety certification credentials.
x PREFACE
Acknowledgments
Thank you to Dr. Orlen Johnson for his continued confidence in allowing me to coauthor this ninth edition
of Essentials of Dental Radiography for Dental Assistants and Hygienists. It is a privilege to be associated
with a textbook with this long-standing history. Thank you to everyone at Pearson for their guidance and
patience. I particularly want to express appreciation to Mark Cohen, editor-in-chief, who 14 years ago
guided my first efforts at textbook writing; Melissa Kerian, associate editor, who has worked patiently
with me on several book editions now; and John Goucher, executive editor, who has kindly encouraged
me and listened to my ideas. The quality of this edition is the direct result of the assistance and support of
the students, faculty, and staff at the Gene W. Hirschfeld School of Dental Hygiene at Old Dominion University, Norfolk, Virginia. I would like to express my special appreciation to the class of 2011 for helping
me to remember why I so enjoy teaching oral radiology.
Evie Thomson
xi
xii
Reviewers
Roberta Albano, CDA, RDH
Springfield Technical College
Springfield, Massachusetts
Dr. Robert Bennett
Texas State Technical College
Harlingen, Texas
Joanna Campbell, RDH, MA
Bergen Community College
Paramus, New Jersey
Armine Leila Derdiarian, DDS
Oxnard College
Oxnard, California
Barbara R. Ellis, RDH, MA
Monroe Community College
Rochester, New York
Mary Emmons, RDH, MSEd
Parkland College
Champaign, Illinois
Joy L. Evans, RDA, EFDA, BS
IntelliTec College
Grand Junction, Colorado
Ann Gallerie, AAS, RDA
Hudson Valley Community College
Troy, New York
Carol Anne Giaquinto, CDA, RDH, MEd
Springfield Technical College
Springfield, Massachusetts
Martha L McCaslin, MA
Dona Ana Community College
Las Cruces, New Mexico
Frances McConaughy RDH, MS
Weber State University
Ogden, Utah
Jean Magee, RDH, Med
NHTI Community College
Concord, New Hampshire
Jennifer Meyer, RDH, BSDH
Southern Illinois University
Carbondale, Illinois
Ann Prey RDH, MS
Milwaukee Area Technical College
Milwaukee, Wisconsin
Judith E. Romano, RDH, MA
Hudson Valley Community College
Troy, New York
Jennifer S. Sherry, RDH
Southern Illinois University
Carbondale, Illinois
Jane H. Slach BA
Kirkwood Community College
Cedar Rapids, Iowa
Gail Renee St. Pierre-Piper, RDH, MA
Iowa Central Community College
Fort Dodge, Iowa
Desiree Sutphen, BA
Volunteer State Community College
Gallatin, Tennessee
Victoria Viera CDA, RDA
Missouri College
Saint Louis, Missouri
Darlene Walsh, RDH, EdM
State University of New York—Orange
Middletown, New York
Janice M. Williams, BSDH, MS
Tennessee State University
Nashville, Tennessee
Essentials of Dental Radiography
for Dental Assistants and Hygienists
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OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. State when x-rays were discovered and by whom.
3. Trace the history of radiography, noting the prominent contributors.
4. List two historical developments that made dental x-ray machines safer.
5. Explain how rectangular PIDs reduce patient radiation exposure.
6. Identify the two techniques used to expose dental radiographs.
7. List five uses of dental radiographs.
8. Become aware of other imaging modalities available for use in the detection and evaluation
of oral conditions.
KEY WORDS
Bisecting technique
Computed tomography (CT)
Cone
Cone beam computed tomography (CBCT)
Cone beam volumetric imaging (CBVI)
Digital imaging
Dosage
Oral radiography
Panoramic radiography
Paralleling technique
Position indicating device (PID)
Radiograph
Radiography
Radiology
Roentgen ray
Roentgenograph
Sensor
Tomography
X-ray
X-ray film
History of Dental
Radiography
CHAPTER
1
PART I • HISTORICAL PERSPECTIVE
AND RADIATION BASICS
CHAPTER
OUTLINE
 Objectives 1
 Key Words 1
 Introduction 2
 Discovery of the
X-ray 2
 Important Scientists
and Researchers 2
 Dental X-ray
Machines 3
 Dental X-ray Film 4
 Digital Image
Receptors 4
 Dental X-ray
Techniques 5
 Advances in Dental
Radiographic
Imaging 5
 Review, Recall,
Reflect, Relate 5
 References 7
2 HISTORICAL PERSPECTIVE AND RADIATION BASICS
Introduction
Technological advancements continue to affect the way we
deliver oral health care. Although new methods for diagnosing
disease and treatment planning comprehensive care have been
introduced, dental radiographs, the images produced by x-rays,
remain the basis for many diagnostic procedures and play an
essential role in oral health care. Radiography is the making of
radiographs by exposing an image receptor, either film or digital sensor. The purpose of dental radiography is to provide the
oral health care team with radiographic images of the best possible diagnostic quality. The goal of dental radiography is to
obtain the highest quality radiographs while maintaining the
lowest possible radiation exposure risk for the patient.
Dental assistants and dental hygienists meet an important
need through their ability to produce diagnostic quality radiographs. The basis for development of the skills needed to
expose, process, mount, and evaluate radiographic images is a
thorough understanding of radiology concepts. All individuals
working with radiographic equipment should be educated and
trained in the theory of x-ray production. The concepts and theories regarding x-ray production that emerged during the early
days of x-radiation discovery are responsible for the quality
health care available today. The purpose of this chapter is to
present a historical perspective that recognizes the contributions of the early scientists and researchers who supplied us
with the fundamentals on which we practice today and advance
toward the future.
Discovery of the X-ray
Oral radiology is the study of x-rays and the techniques used to
produce radiographic images. We begin that study with the history of dental radiography and the discovery of the x-ray. The
x-ray revolutionized the methods of practicing medicine and
dentistry by making it possible to visualize internal body structures noninvasively. Professor Wilhelm Conrad Roentgen’s
(pronounced “rent’gun”; Figure 1-1) experiment in Bavaria
(Germany) on November 8, 1895, produced a tremendous
advance in science. Professor Roentgen’s curiosity was aroused
during an experiment with a vacuum tube called a Crookes tube
(named after William Crookes, an English chemist). Roentgen
observed that a fluorescent screen near the tube began to glow
when the tube was activated by passing an electric current
through it. Examining this strange phenomenon further, he
noticed that shadows could be cast on the screen by interposing
objects between it and the tube. Further experimentation
showed that such shadow images could be permanently
recorded on photographic film (Figure 1-2). For his work, Dr.
Roentgen was awarded the first Nobel Prize for physics in 1901.
In the beginning, Roentgen was uncertain of the nature of
this invisible ray that he had discovered. When he later reported
his finding at a scientific meeting, he spoke of it as an x-ray
because the symbol x represented the unknown. After his findings were reported and published, fellow scientists honored him
by calling the invisible ray the roentgen ray and the image produced on photosensitive film a roentgenograph. Because a photographic negative and an x-ray film have basic similarity and
FIGURE 1-2 This famous radiograph, purported to be
Mrs. Bertha Roentgen’s hand, was taken on December 22, 1895.
(Reprinted with permission from Radiology Centennial, Inc.,
Copyright 1993)
FIGURE 1-1 Wilhelm Conrad Roentgen (1845–1923).
(Reprinted with permission from Radiology Centennial, Inc.,
Copyright 1993)
the x-ray closely resembles the radio wave, the prefix radio- and
the suffix -graph have been combined into radiograph. The latter term is used by oral health care professionals because it is
more descriptive than x-ray and easier to pronounce than
roentgenograph.
Important Scientists and Researchers
A few weeks after Professor Roentgen announced his discovery, Dr. Otto Walkhoff, a German physicist, was the first to
expose a prototype of a dental radiograph. This was accomplished by covering a small, glass photographic plate with
CHAPTER 1 • HISTORY OF DENTAL RADIOGRAPHY 3
black paper to protect it from light and then wrapping it in a
sheath of thin rubber to prevent moisture damage during the 25
minutes that he held the film in his mouth. A similar exposure
can now be made in 1/10th of a second. The resulting radiograph was experimental and had little diagnostic value
because it was impossible to prevent film movement, but it did
prove that the x-ray would have a role in dentistry. The length
of the exposure made the experiment a dangerous one for Dr.
Walkhoff. The dangers of overexposure to radiation were not
known at that time.
We will probably never know who made the first dental
radiograph in the United States. It was either Dr. William
Herbert Rollins, a Boston dentist and physician, Dr. William
James Morton, a New York physician, or Dr. C. Edmund
Kells, a New Orleans dentist. Dr. Rollins was one of the first
to alert the profession to the need for radiation hygiene and
protection and is considered by many to be the first advocate
for the science of radiation protection. Unfortunately, his
advice was not taken seriously by many of his fellow practitioners for a long time.
Dr. Morton is known to have taken radiographs on skulls
very early. He gave a lecture on April 24, 1896, before the
New York Odontological Society calling attention to the possible usefulness of roentgen rays in dental practice. One of
Dr. Morton’s radiographs revealed an impacted tooth, which
was otherwise undetectable clinically.
Most people claim Dr. Kells took the first dental radiograph on a living subject in the United States. He was the first
to put the radiograph to practical use in dentistry.
Dr. Kells made numerous presentations to organized dental
groups and was instrumental in convincing many dentists that
they should use oral radiography as a diagnostic tool. At that
time, it was customary to send the patient to a hospital or physician’s office on those rare occasions when dental radiographs
were prescribed.
Two other dental x-ray pioneers who should be mentioned
are William David Coolidge and Howard Riley Raper. The
most significant advancement in radiology came in 1913 when
Dr. Coolidge, working for the General Electric Company, introduced the hot cathode tube. The x-ray output of the Coolidge
tube could be predetermined and accurately controlled. Professor Raper, at Indiana Dental College, wrote the first dental radiology textbook, Elementary and Dental Radiology, and
introduced bitewing radiographs in 1925.
Because x-rays are invisible, scientists and researchers working in the field of radiography were not aware that continued
exposure produced accumulations of radiation effects in the
body and, therefore, could be dangerous to both patient and
radiographer. When radiography was in its infancy, it was common practice for the dentist or dental assistant to help the patient
hold the film in place while making the exposure. These oral
health care professionals were exposed to unnecessary radiation. Frequent repetition of this practice endangered their health
and occasionally led to permanent injury or death. Fortunately,
although the hazards of prolonged exposure to radiation are not
completely understood, scientists have learned how to reduce
them drastically by proper use of fast film and digital sensors,
safer x-ray machines, and strict adherence to safety protocol.
Never hold the film packet or digital sensor in the patient’s
oral cavity during the exposure. If the patient cannot tolerate
placement of the image receptor or hold still throughout the
exposure, the patient’s parent or guardian may have to
assist or an extraoral radiograph may have to be substituted. The parent or guardian should be protected with lead
or lead equivalent barriers such as an apron or gloves when
they will be in the path of the beam.
PRACTICE POINT
Today, it can be assumed that every dental office in the
United States that offers comprehensive oral health care to
patients will have x-ray equipment. It is worth noting that initially few hospitals and only the most progressive physicians
and dentists possessed x-ray equipment. This limited use of
dental radiography can be attributed to the fact that the early
equipment was primitive and sometimes dangerous. Also,
x-rays were used for entertainment purposes by charlatans at
fairgrounds, so people often associated them with quackery.
Resistance to change, ignorance, apathy, and fear delayed the
widespread acceptance of radiography in dentistry for years.
Table 1-1 lists noteworthy scientists and researchers and
their contributions to dental radiology.
Dental X-ray Machines
Dental x-ray machines manufactured before 1920 were an
electrical hazard to oral health care professionals because of
the open, uninsulated high-voltage supply wires. In 1919,
William David Coolidge and General Electric introduced the
Victor CDX shockproof dental x-ray machine. The x-ray tube
and high-voltage transformer were placed in an oil-filled compartment that acted as a radiation shield and electrical insulator. Modern x-ray machines use this same basic construction.
Variable, high-kilovoltage machines were introduced in the
middle 1950s, allowing increased target–image receptor distances to be used, which in turn increased the use of the paralleling technique.
Within the last 30 years, major progress has been made in
restricting the size of the x-ray beam. One such development is
the replacement of the pointed cone through which x-rays pass
from the tube head toward the patient by open cylinders. When
the pointed cones were first used, it was not realized that the
x-rays were scattered through contact with the material of the
cones. Because cones were used for so many years, many still
refer to the open cylinders or rectangular tubes as cones. The
term position indicating device (PID) is more descriptive of
its function of directing the x-rays, rather than of its shape. A
further improvement has been the introduction of rectangular
4 HISTORICAL PERSPECTIVE AND RADIATION BASICS
lead-lined PIDs. This shape limits the size of the x-ray beam
that strikes the patient to the actual size of the image receptor
(Figure 1-3).
Panoramic radiography became popular in the 1960s
with the introduction of the panoramic x-ray machine.
Panoramic units are capable of exposing the entire dentition
and surrounding structures on a single image. Today, many oral
health care practices have a panoramic x-ray machine.
As digital imaging continues to develop, exciting
advances in the development of imaging systems that allow for
enhanced two- and three-dimensional images are being used in
the diagnosis and treatment of dental conditions, particularly
implant evaluation and orthodontic interventions. Medical
imaging modalities such as tomography and computed
TABLE 1-1 Noteworthy Scientists and Researchers in Dental Radiography
NAME EVENT YEAR
W. C. Roentgen Discovered x-rays 1895
C. E. Kells May have taken first dental radiograph in U.S. 1896
W. J. Morton May have taken first dental radiograph in U.S. 1896
W. H. Rollins May have taken first dental radiograph in U.S. 1896
Published “X Light Kills,” warning of x-ray dangers 1901
O. Walkhoff First to make a dental radiograph 1896
W. A. Price Suggested basics for both bisecting and paralleling techniques 1904
A. Cieszynski Applied “rule of isometry” to bisecting technique 1907
W. D. Coolidge Introduced the hot cathode tube 1913
H. R. Raper Wrote first dental x-ray textbook 1913
Introduced bitewing radiographs 1924
F. W. McCormack Developed paralleling technique 1920
G. M. Fitzgerald Designed a “long-cone” to use with the paralleling technique 1947
Francis Mouyen Developed the first digital imaging system called RadioVisioGraphy 1987
FIGURE 1-3 Comparison of circular and rectangular PIDs.
(Image courtesy of Gendex Dental Corporation)
tomography (CT scans), a method of imaging a single
selected plane of tissues has been used to assist dentists with
complex diagnosis and treatment planning since the early
1970s. Because these medical imaging modalities deliver high
radiation doses, sometimes up to 600 times more than a
panoramic radiograph, the development of cone beam volumetric imaging (CBVI) or cone beam computed tomography (CBCT) with lower radiation doses (4 to 15 times that
required for a panoramic radiograph) for dental application is
purported to become the gold standard of diagnosis for certain
dental applications in the very near future.
Dental X-ray Film
Although today it is increasingly common to see paperless dental practices equipped with computers and image receptors that
allow for the digital capture of radiographic images, film has
been the standard for producing dental radiographs since 1896.
Early dental x-ray film packets consisted of glass photographic
plates wrapped in black paper and rubber. In 1913, the Eastman
Kodak Company marketed the first hand-wrapped, moistureproof dental x-ray film packet. It was not until 1919 that the
first machine-wrapped dental x-ray film packet became commercially available (also from Kodak).
Early film had emulsion on only one side and required
long exposure times. Today, both sides of the dental x-ray film
are coated with emulsion and require only about 1/16th the
amount of exposure required 50 years ago.
Digital Image Receptors
Digital imaging systems (see Chapter 9) replace film as the
image receptor with a sensor. In 1987, Francis Mouyen, a
French dentist, introduced the use of a digital radiography
CHAPTER 1 • HISTORY OF DENTAL RADIOGRAPHY 5
system marketed for dental imaging, called RadioVisioGraphy.
The first digital sensor was bulky and had limitations. Since
that time image sensors have been improved and are now
comparable to film in dimensions of the exposed field of view
and approach film in overall radiographic quality. Their
advantages include a reduction in radiation dosage, the elimination of film and processing chemistry, and the subsequent
disposal of film packaging materials such as lead foils and
spent processing chemicals, both potentially hazardous to the
environment.
Dental X-ray Techniques
Two basic techniques are used in intraoral radiography. The
first and earliest technique is called the bisecting technique.
The second and newer technique is referred to as the
paralleling technique. The paralleling method is the technique
of choice and is taught in all dental assisting, dental hygiene,
and dental schools.
In 1904, Dr. Weston A. Price suggested the basics of both
the bisecting and paralleling techniques. As others were working on the same problems and were unaware of Price’s contributions, the credit for developing the techniques went to others.
In 1907, A. Cieszynski, a Polish engineer, applied the rule
of isometry to dental radiology and is credited for suggesting
the bisecting technique. The bisecting technique was the only
method used for many years.
The search for a less-complicated technique that would
produce better radiographs more consistently resulted in the
development of the paralleling technique by Dr. Franklin
McCormack in 1920. Dr. G. M. Fitzgerald, Dr. McCormack’s
son-in-law, designed a long “cone” PID and made the paralleling
technique more practical in 1947.
Advances in Dental Radiographic Imaging
Radiography, aided by the introduction first of transistors and
then computers, has allowed for significant radiation reduction
in modern x-ray machines. Advances in two-dimensional and
three-dimension imaging systems are predicted to move radiography away from static interpretation of pictures of images
and toward representations of real-life conditions. This introduction of a computed approach with its almost instantaneous
images is sure to benefit the quality of oral health care.
Today, an oral health care practice would find it impossible to provide patients with comprehensive dental care without dental radiographs (Figure 1-4). Many practices have
multiple intraoral dental x-ray machines (one in each operatory) and supplement these with a panoramic x-ray machine.
Although no diagnosis can be based solely on radiographic
evidence without a visual and physical examination, many
conditions might go undetected if not for radiographic examinations (Box 1-1).
The discovery of x-radiation revolutionized the practice of
preventive oral health care. Future technological advances
undoubtedly will improve both the diagnostic use and the
safety of radiography in the years ahead.
REVIEW—Chapter summary
Professor Wilhelm Conrad Roentgen’s discovery of the x-ray
on November 8, 1895, revolutionized the methods of practicing
medicine and dentistry by making it possible to visualize internal body structures noninvasively. The usefulness of the x-ray
as a diagnostic tool was recognized almost immediately as scientists and researchers contributed to its advancement. The use
of radiographs in medical and dental diagnostic procedures is
now essential.
In the early 1900s, scientists and researchers working in
the field of radiography were not aware that radiation could be
dangerous, resulting in exposure to unnecessary radiation.
Early x-ray equipment was primitive and sometimes dangerous. Today improved equipment, advanced techniques, and
educated personnel make it possible to obtain radiographs with
high diagnostic value and minimal risk of unnecessary radiation to patient or operator.
Although film has been the standard image receptor since
the discovery of the x-ray, dental practices continue to adopt
the computer and digital sensor as the method of acquiring a
dental radiographic image. Digital imaging reduces patient
FIGURE 1-4 Radiography in a modern oral health care
practice. (Image courtesy of Gendex Dental Corporation)
• To detect, confirm, and classify oral diseases and lesions
• To detect and evaluate trauma
• To evaluate growth and development
• To detect missing and supernumerary (extra) teeth
• To document the oral condition of a patient
• To educate patients about their oral health
BOX 1-1 Uses of Dental Radiographs
6 HISTORICAL PERSPECTIVE AND RADIATION BASICS
radiation dose, eliminates the need to maintain an inventory of
film and processing chemistry, and avoids disposal of the
potentially environmental hazards of lead foils and spent processing chemicals.
The two basic techniques for acquiring a dental radiographic image are the bisecting technique and the paralleling
technique.
Cone beam volumetric or computed tomography (CBVT
or CBCT) produces two- and three-dimension images for dental diagnosis. This technology may become the gold standard
for diagnosing certain dental conditions.
RECALL—Study questions
For questions 1–5, match each term with its definition.
a. Radiograph
b. Radiography
c. Radiology
d. Roentgen ray
e. X-ray
_____ 1. The study of x-radiation
_____ 2. Image or picture produced by x-rays
_____ 3. An older term given to x-radiation in honor of
its discoverer
_____ 4. The original term Roentgen applied to the
invisible ray he discovered
_____ 5. The making of radiographs by exposing and
processing x-ray film
6. Who discovered the x-ray?
a. C. Edmund Kells
b. William Rollins
c. Franklin McCormack
d. Wilhelm Conrad Roentgen
7. When were x-rays discovered?
a. 1695
b. 1795
c. 1895
d. 1995
8. Who is believed to have exposed the prototype of the
first dental x-ray film?
a. A. Cieszynski
b. Otto Walkhoff
c. Wilhelm Conrad Roentgen
d. C. Edmund Kells
9. Who is considered by many to be the first advocate
for the science of radiation protection?
a. Weston Price
b. William Morton
c. William Herbert Rollins
d. Franklin McCormack
10. Replacing the pointed “cone” position indicating device
(PID) with an open-cylinder PID reduced the radiation
dose to the patient because open-cylinder PIDs eliminate scattered x-rays through contact with the cone
material.
a. Both the statement and reason are correct and
related.
b. Both the statement and reason are correct but NOT
related.
c. The statement is correct, but the reason is NOT.
d. The statement is NOT correct, but the reason is correct.
e. NEITHER the statement NOR the reason is
correct.
11. Which imaging modality will most likely become the
gold standard for imaging certain dental conditions in
the near future?
a. Cone beam volumetric tomography
b. Computed tomography
c. Digital imaging
d. Tomography
12. Who is given credit for applying the rule of isometry to
the bisecting technique?
a. William Rollins
b. A. Cieszynski
c. G. M. Fitzgerald
d. Otto Walkhoff
13. Who is given credit for developing the paralleling
technique?
a. W. D. Coolidge
b. H. R. Raper
c. William Morton
d. Franklin McCormack
14. List five uses of dental radiographs.
a. ______________
b. ______________
c. ______________
d. ______________
e. ______________
REFLECT—Case study
Your patient today tells you that she recently watched a television documentary on the dangers of excess radiation exposure.
Based on your reading in this chapter, develop a brief conversation between you and this patient explaining how historical
developments have increased dental radiation safety to put the
patient at ease.
CHAPTER 1 • HISTORY OF DENTAL RADIOGRAPHY 7
RELATE—Laboratory application
Perform an inventory of the x-ray machine used in your facility.
Using the historical lessons learned in this chapter, identify the
parts of the x-ray machine, type of film or digital sensor used,
and the safety protocol and posted exposure factors in place.
Specifically list the following:
a. Unit manufacturer
Using the Internet, research the manufacturer’s Web
site to determine the company origin. How old is the
company? Are they a descendant of an original manufacturer? Who developed the design for the x-ray unit
produced today? Do they offer different unit designs?
What is the reason your facility chose this model?
b. Shape and length of the PID
Does the machine you are observing reduce radiation exposure? Why or why not? Why was the PID you
are observing chosen over other shapes and lengths?
c. Names of the dials on the control panel.
How does this differ from the dental x-ray machines
used in dental practices in the early 1900s? What exposure factors are inherent to the unit, and what factors
may be varied by the radiographer? What are the advantages and disadvantages to using an x-ray machine
where the exposure settings are fixed? Variable?
d. What are the recommended exposure settings for various types of radiographs? How do these differ from the
settings used by the first dentists to use x-rays in practice in the early 1900s?
e. Describe the film or digital sensor used to produce a
radiographic image.
What is the film size and speed, and how is it packaged? Does the film or sensor used in your facility
allow you to produce a quality radiograph using the
least amount of radiation possible? What is the rationale for using this film type in your facility?
f. Are the safety protocols regarding x-ray machine operation known to all operators? How is this made evident?
List the safety protocols in place in your facility.
REFERENCES
Carestream Health, Inc. (2007). Kodak dental systems: Radiation safety in dental radiography. Pub. N-414, Rochester,
NY: Author.
Horner, K., Drage, N., & Brettle, D. (2008). 21st century imaging. London: Quintessence Publishing.
Langland, O. E., Langlais, R. P., & Preece, J. W. (2002).
Principles of Dental Imaging (2nd ed.). Philadelphia:
Williams & Wilkins.
Miles, D. A. (2008). Color atlas of cone beam volumetric
imaging for dental applications. Chicago: Quintessence
Publishing.
Scarfe, W. C., Farnam, A. G., & Sukovic, P. (2006). Clinical
applications of cone-beam computed tomography in dental
practice. Journal of the Canadian Dental Association, 72,1.
White, S. C., & Pharoah, M. J. (2008). Oral radiology. Principles and interpretation (6th ed.). St. Louis: Elsevier.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Draw and label a typical atom.
3. Describe the process of ionization.
4. Differentiate between radiation and radioactivity.
5. List the properties shared by all energies of the electromagnetic spectrum.
6. Explain the relationship between wavelength and frequency.
7. Explain the inverse relationship between wavelength and penetrating power of x-rays.
8. List the properties of x-rays.
9. Identify and describe the two processes by which kinetic energy is converted to electromagnetic energy within the dental x-ray tube.
10. List and describe the four possible interactions of dental x-rays with matter.
11. Define the terms used to measure x-radiation.
12. Match the Système Internationale (SI) units of x-radiation measurement to the corresponding
traditional terms.
13. Identify three sources of naturally occurring background radiation.
Characteristics
and Measurement
of Radiation
CHAPTER
2
CHAPTER
OUTLINE
 Objectives 8
 Key Words 8
 Introduction 9
 Atomic Structure 9
 Ionization 10
 Ionizing Radiation 10
 Radioactivity 10
 Electromagnetic
Radiation 11
 Properties of
X-rays 12
 Production of
X-rays 13
 Interaction of
X-rays with
Matter 13
 Units of Radiation 15
 Background
Radiation 16
 Review, Recall,
Reflect, Relate 17
 References 18 KEY WORDS
Absorbed dose
Absorption
Alpha particle
Angstrom (Å)
Atom
Atomic number
Atomic weight
Background radiation
Beta particle
Binding energy
Characteristic radiation
Coherent scattering
Compton effect (scattering)
Coulombs per kilogram
(C/kg)
Decay
CHAPTER 2 • CHARACTERISTICS AND MEASUREMENT OF RADIATION 9
Introduction
The word radiation is attention grabbing. When news headlines incorporate words such as radiation, radioactivity, and exposure, the reader pays attention to what follows. Patients often link dental x-rays with other types of
radiation exposure they read about or see on TV. Patients
assume that oral health care professionals who are responsible for taking dental x-rays are knowledgeable regarding all
types of ionizing radiation exposures and can adequately
answer their questions. Although the study of quantum
physics is beyond the scope of this book, it is important that
dental assistants and dental hygienists understand what dental radiation is, what it can do, and what it cannot do. In this
chapter we will explore the characteristics of x-radiation and
look at where dental x-rays fit in relation to other types and
sources of radiations.
Prior to studying the production of x-rays, the radiographer should have a base knowledge of atomic structure. The
scientist understands that the world consists of matter and
energy. Matter is defined as anything that occupies space and
has mass. Things that we see and recognize are forms of matter. Energy is defined as the ability to do work and overcome
resistance. Heat, light, electricity, and x-radiation are forms
of energy. Matter and energy are closely related. Energy is
produced whenever the state of matter is altered by natural or
artificial means. The difference between water, steam, and
ice is the amount of energy associated with the molecules.
Such an energy exchange is produced within the x-ray
machine and will be discussed later.
Atomic Structure
To understand radiation, we must understand atomic structure.
Currently we know of 118 basic elements that occur either singly
or in combination in natural forms. Each element is made up of
atoms. An atom is the smallest particle of an element that still
retains the properties of the element. If any given atom is split, the
resulting components no longer retain the properties of the element. Atoms are generally combined with other atoms to form
molecules. A molecule is the smallest particle of a substance that
retains the properties of that substance. A simple molecule such
as sodium chloride (table salt) contains only two atoms, whereas a
complex molecule like DNA (deoxyribonucleic acid) may contain hundreds of atoms.
Atoms are extremely minute and are composed of three
basic building blocks: electrons, protons, and neutrons.
• Electrons have a negative charge and are constantly in
motion orbiting the nucleus.
• Protons have a postitive charge. The number of protons in
the nucleus of an element determines its atomic number.
• Neutrons have no charge.
The atom’s arrangement in some ways resembles the solar
system (Figure 2-1). The atom has a nucleus as its center or
sun, and the electrons revolve around it like planets. The protons and neutrons form the central core or nucleus of the atom.
The electrons orbit around the nucleus in paths called shells or
energy levels. Normally, the atom is electrically neutral, having
equal numbers of protons in its nucleus and electrons in orbit.
The nucleus of all atoms except hydrogen contains at
least one proton and one neutron (hydrogen in its simplest
form has only a proton). Some atoms contain a very high
number of each. The electrons and the nucleus normally
remain in the same position relative to one another. To accommodate the electrons revolving about the nucleus, the larger
atoms have several concentric orbits at various distances from
the nucleus. These are referred to as electron shells, which
some chemists call energy levels. The innermost level is
referred to as the K shell, the next as the L shell, and so on, up
to 7 shells (Figure 2-1).
KEY WORDS
Dose
Dose equivalent
Effective dose equivalent
Electromagnetic radiation
Electromagnetic spectrum
Electron
Element
Energy
Energy levels
Exposure
Frequency
Gamma rays
General/bremsstrahlung radiation
Gray (Gy)
Rad
Radiation
Radioactivity
Radiolucent
Radiopaque
Rem
Roentgen (R)
Secondary radiation
Sievert (Sv)
Soft radiation
Système Internationale (SI)
Velocity
Wavelength
Weighting factor
Hard radiation
Ion
Ion pair
Ionization
Ionizing radiation
Isotope
Kinetic energy
Microsievert (μSv)
Molecule
Neutron
Particulate radiation
Photoelectric effect
Photon
Proton
e–
Displaced electron
(negative ion)
X-ray
Remaining atom
(positive ion)
e–
+
+
e–
+ Protons Neutrons e– Electrons
FIGURE 2-2 Ionization is the formation of ion pairs. When an
atom is struck by an x-ray, an electron may be dislodged, and an ion
pair results.
10 HISTORICAL PERSPECTIVE AND RADIATION BASICS
Electrons are maintained in their orbits by the positive
attraction of the protons, known as binding energy. The binding
energy of an electron is strongest in the intermost K shell and
becomes weaker in the outer shells.
Ionization
Atoms that have gained or lost electrons are electrically unstable and are called ions. An ion is defined as a charged particle.
The formation of ions is easier to understand if we review the
normal structural arrangement of the atom. The atom normally
has the same number of protons (positive charges) in the
nucleus as it has electrons (negative charges) in the orbital levels. When one of these electrons is removed from its orbital
level in a neutral atom, the remainder of the atom loses its electrical neutrality.
An atom from which an electron has been removed has
more protons than electrons, is positively charged, and is called a
positive ion. The negatively charged electron that has been separated from the atom is a negative ion. The positively charged
atom ion and the negatively charged electron ion are called an
ion pair. Ionization is the formation of ion pairs. When an atom
is struck by an x-ray photon, an electron may be dislodged and
an ion pair created (Figure 2-2). As high-energy electrons travel
on, they push out (like charges repel) electrons from the orbits of
other atoms, creating additional ion pairs. These unstable ions
attempt to regain electrical stability by combining with another
oppositely charged ion.
Ionizing Radiation
Radiation is defined as the emission and movement of
energy through space in the form of electromagnetic radiation
(x- and gamma rays) or particulate radiation (alpha and
beta particles). Any radiation that produces ions is called
ionizing radiation. Only a portion of the radiation portrayed
on the electromagnetic spectrum, the x-rays and the gamma
and cosmic rays, are of the ionizing type. In dental radiography, our concern is limited to the changes that may occur in
the cellular structures of the tissues as the ions are produced
by the passage of x-rays through the cells. The mechanics of
biologic tissue damage are explained in Chapter 5.
Radioactivity
Radioactivity is defined as the process whereby certain unstable elements undergo spontaneous disintegration (decay) in an
effort to attain a stable nuclear state. Unstable isotopes are
radioactive and attempt to regain stability through the release of
energy, by a process known as decay. Dental x-rays do not
involve the use of radioactivity.
Scientists have learned to produce several types of radiations that are identical to natural radiations. Ultraviolet
Orbiting electrons
(negatively charged)
“K” orbit
“L” orbit
Nucleus:
Protons
(positively charged)
Neutrons
(no charge)
e– e–
e–
e– e–
e–
+
+ +
+ +
+
+ Protons Neutrons e– Electrons
FIGURE 2-1 Diagram of carbon atom. In the
neutral atom, the number of positively charged protons
in the nucleus is equal to the number of negatively
charged orbiting electrons. The innermost orbit or
energy level is the K shell, the next is the L shell, and
so on.
waves are produced artificially for sunlamps or fluorescent
lights and for numerous other uses. Another man-made radiation is the laser beam, whose potential impact on oral health
is still being explored.
Electromagnetic Radiation
Electromagnetic radiation is the movement of wavelike
energy through space as a combination of electric and magnetic
fields. Electromagnetic radiations are arranged in an orderly
CHAPTER 2 • CHARACTERISTICS AND MEASUREMENT OF RADIATION 11
fashion according to their energies in what is called the
electromagnetic spectrum (Figure 2-3). The electromagnetic
spectrum consists of an orderly arrangement of all known radiant energies. X-radiation is a part of the electromagnetic spectrum, which also includes cosmic rays, gamma rays, ultraviolet
rays, visible light, infrared, television, radar, microwave, and
radio waves. All energies of the electromagnetic spectrum share
the following properties:
• Travel at the speed of light
• Have no electrical charge
1
10,000
1
1,000
1
1,000
1
100
1
100
1
10
1
10
1
10
100
1,000
10,000
100,000
1,000,000
1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
Forms Uses
Cosmic rays
X-rays and
gamma rays
Very soft x-rays
Ultraviolet rays
Light
Infrared rays
Dental and
medical radiography
Sunlamp
Photography
Toaster
Radar
Television
Radio
Radio waves
Radiation
associated with
electric waves
Measured
in angstrom units
Measured
in meters
FIGURE 2-3 The electromagnetic
spectrum. Electromagnetic radiations are
arranged in an orderly fashion according to
their energies.
FIGURE 2-4 Differences in wavelengths
and frequencies. Only the shortest
wavelengths with extremely high frequency and
energy are used to expose dental radiographs
Wavelength is determined by the distances
between the crests. Observe that this distance is
much shorter in (B) than in (A). The photons
that comprise the dental x-ray beam are
estimated to have over 250 million such crests
per inch. Frequency is the number of crests of a
wavelength passing a given point per second.
Crest Crest
Crest Crest
Wavelength
A
B
Long wavelength
Low frequency
Low energy
Less penetrating x-ray
Short wavelength
High frequency
High energy
More penetrating x-ray
12 HISTORICAL PERSPECTIVE AND RADIATION BASICS
• Velocity refers to the speed of the wave. In a vacuum, all
electromagnetic radiations travel at the speed of light
(186,000 miles/sec or 3 × 108 m/sec).
No clear-cut separation exists between the various radiations represented on the electromagnetic spectrum; consequently, overlapping of the wavelengths is common. Each form
PRACTICE POINT
Wavelength and frequency are inversely related. When the
wavelength is long, the frequency is low, resulting in lowenergy, less penetrating x-rays (Figure 2-4). When the wavelength is short, the frequency is high, resulting in
high-energy, more penetrating x-rays.
• Have no mass or weight
• Pass through space as particles and in a wavelike motion
• Give off an electrical field at right angles to their path of
travel and a magnetic field at right angles to the electric
field
• Have energies that are measurable and different
Electromagnetic radiations display two seemingly contradictory properties. They are believed to move through space as
both a particle and a wave. Particle or quantum theory assumes
the electromagnetic radiations are particles, or quanta. These
particles are called photons. Photons are bundles of energy that
travel through space at the speed of light. Wave theory assumes
that electromagnetic radiation is propagated in the form of
waves similar to waves resulting from a disturbance in water.
Electromagnetic waves exhibit the properties of wavelength,
frequency, and velocity.
• Wavelength is the distance between two similar points on
two successive waves, as illustrated in Figure 2-4. The
symbol for wavelength is the Greek letter lambda ( ).
Wavelength may be measured in the metric system or in
angstrom (Å) units (1 Å is about 1/250,000,000 in. or
1/100,000,000 cm). The shorter the wavelength, the more
penetrating the radiation.
• Frequency is a measure of the number of waves that pass
a given point per unit of time. The symbol for frequency is
the Greek letter nu (ν). The special unit of frequency is the
hertz (Hz). One hertz equals 1 cycle per second. The
higher the frequency, the more penetrating the radiation.
l
of radiation has a range of wavelengths. This accounts for some
of the longer infrared waves being measured in meters, whereas
the shorter infrared waves are measured in angstrom units. It
therefore follows that all x-radiations are not the same wavelength. The longest of these are the Grenz rays, also called soft
radiation, that have only limited penetrating power and are
unsuitable for exposing dental radiographs. The wavelengths
used in diagnostic dental radiography range from about 0.1 to
0.5 Å and are classified as hard radiation, a term meaning
radiation with great penetrating power. Still shorter wavelengths are produced by super-voltage machines when greater
penetration is required, as in some forms of medical therapy
and industrial radiography.
Properties of X-rays
X-rays are believed to consist of minute bundles (or quanta)
of pure electromagnetic energy called photons. These have
no mass or weight, are invisible, and cannot be sensed.
Because they travel at the speed of light (186,000 miles/sec
or 3 × 108 meters/sec), these x-ray photons are often referred
to as “bullets of energy.” X-rays have the following properties. They
• Are invisible
• Travel in straight lines
• Travel at speed of light
• Have no mass or weight
• Have no charge
• Interact with matter causing ionization
• Can penetrate opaque tissues and structures
• Can affect photographic film emulsion (causing a latent
image)
• Can affect biological tissue
X-ray photons have the ability to pass through gases, liquids, and solids. The ability to penetrate materials or tissues
depends on the wavelength of the x-ray and the thickness and
density of the object. The composition of the object or the tissues determines whether the x-rays will penetrate and pass
through it or whether they will be absorbed in it. Materials that
are extremely dense and have a high atomic weight will absorb
more x-rays than thin materials with low atomic numbers. This
partially explains why dense structures such as bone and enamel
appear radiopaque (white or light gray) on the radiograph,
whereas the less dense pulp chamber, muscles, and skin appear
radiolucent (dark gray or black).
Production of X-rays
X-rays are generated inside an x-ray tube located in the tube
head of a dental x-ray machine (Chapter 3). X-rays are produced whenever high-speed electrons are abruptly stopped or
slowed down. Bodies in motion are believed to have kinetic
energy (from the Greek word kineticos, “pertaining to
motion”). In a dental x-ray tube, the kinetic energy of electrons
is converted to electromagnetic energy by the formation of general or bremsstrahlung radiation (German for “braking”) and
characteristic radiation.
• General/bremsstrahlung radiation is produced when
high-speed electrons are stopped or slowed down by the
tungsten atoms of the dental x-ray tube. Referring to
Figure 2-5, observe that the impact from both (A) and (B)
electrons produce general/bremsstrahlung. When a highspeed electron collides with the nucleus of an atom in the
target metal, as in (A), all its kinetic energy is transferred
into a single x-ray photon. In (B), a high-speed electron is
slowed down and bent off its course by the positive pull of
the nucleus. The kinetic energy lost is converted into an
x-ray. The majority of x-rays produced by dental x-ray
machines are formed by general/bremsstrahlung radiation.
• Characteristic radiation is produced when a bombarding
electron from the tube filament collides with an orbiting K
electron of the tungsten target as shown in Figure 2-5 (C).
The K-shell electron is dislodged from the atom. Another
electron in an outer shell quickly fills the void, and an
x-ray is emitted. The x-rays produced in this manner are
called characteristic x-rays. Characteristic radiation can
only be produced when the x-ray machine is operated at or
above 70 kilovolts (kVp) because a minimum force of 69
kVp is required to dislodge a K electron from a tungsten
atom. Characteristic radiation is of minor importance
because it accounts for only a very small part of the x-rays
produced in a dental x-ray machine.
Interaction of X-rays with Matter
A beam of x-rays passing through matter is weakened and
gradually disappears. Such a disappearance is referred to as
absorption of x-rays. When so defined, absorption does not
imply an occurrence such as a sponge soaking up water, but
instead refers to the process of transferring the energy of the
x-rays to the atoms of the material through which the x-ray
beam passes. The basic method of absorption is ionization.
When a beam of x-rays pass through matter, four possibilities exist:
1. No interaction. The x-ray can pass through an atom
unchanged and no interaction occurs (Figure 2-6).
• In dental radiography about 9 percent of the x-rays pass
through the patient’s tissues without interaction.
CHAPTER 2 • CHARACTERISTICS AND MEASUREMENT OF RADIATION 13
Nucleus
C
B
A
e–
e–
e–
e–
e–
e–
e–
e– e–
e–
e–
e–
e– e–
e–
e–
e– e–
FIGURE 2-5 General/bremsstrahlung and characteristic
radiation. High-speed electron (A) collides with the nucleus, and all
its kinetic energy is converted into a single x-ray. High-speed
electron (B) is slowed down and bent off its course by the positive
pull of the nucleus. The kinetic energy lost is converted into an x-ray.
The impact from both A and B electrons produce general radiation.
Characteristic radiation is produced when a high-speed electron
(C) hits and dislodges a K shell (orbiting) electron. Another electron
in an outer shell quickly fills the void, and x-ray energy is emitted.
Characteristic radiation only occurs above 70 kVp with a tungsten
target.
Scattered
x-ray
Incoming
x-ray
Nucleus
e Compton electron –
e– e–
e–
e– e–
e–
FIGURE 2-8 Compton scattering. Compton scattering is similar
to the photoelectric effect in that the incoming x-ray interacts with an
orbital electron and ejects it. But in the case of Compton interaction,
only a part of the x-ray energy is transferred to the electron, and a
new, weaker x-ray is formed and scattered in a new direction. The
new x-ray may undergo another Compton scattering or it may be
absorbed by a photoelectric effect interaction.
X-ray
Nucleus
Photoelectron
e– e–
e–
e– e–
e–
FIGURE 2-7 Photoelectric effect. The incoming x-ray gives
up all its energy to an orbital electron of the atom. The x-ray is
absorbed and simply vanishes. The electromagnetic energy of
the x-ray is imparted to the electron in the form of kinetic
energy of motion and causes the electron to fly from its orbit,
creating an ion pair. The high-speed electron (called a
photoelectron) knocks other electrons from the orbits of other
atoms forming secondary ion pairs.
14 HISTORICAL PERSPECTIVE AND RADIATION BASICS
2. Coherent scattering (unmodified scattering, also known
as Thompson scattering). When a low-energy x-ray passes
near an atom’s outer electron, it may be scattered without
loss of energy (Figure 2-6). The incoming x-ray interacts
with the electron by causing the electron to vibrate at the
same frequency as the incoming x-ray. The incoming x-ray
ceases to exist. The vibrating electron radiates another
x-ray of the same frequency and energy as the original
incoming x-ray. The new x-ray is scattered in a different
direction than the original x-ray. Essentially, the x-ray is
scattered unchanged.
• Coherent scattering accounts for about 8 percent of the
interactions of matter with the dental x-ray beam.
3. Photoelectric effect. The photoelectric effect is an all-ornothing energy loss. The x-ray imparts all its energy to an
orbital electron of some atom. This dental x-ray, because it
consisted only of energy in the first place, simply vanishes.
The electromagnetic energy of the x-ray is imparted to the
electron in the form of kinetic energy of motion and causes
the electron to fly from its orbit with considerable speed.
Thus, an ion pair is created (Figure 2-7). Remember, the
basic method of the interaction of x-rays with matter is the
formation of ion pairs. The high-speed electron (called a
photoelectron) knocks other electrons from the orbits of
other atoms (forming secondary ion pairs) until all its
energy is used up. The positive ion atom combines with a
free electron, and the absorbing material is restored to its
original condition.
• Photoelectric effect accounts for about 30 percent of the
interactions of matter with the dental x-ray beam.
4. Compton effect. The Compton effect (often called Compton scattering) is similar to the photoelectric effect in that
the dental x-ray interacts with an orbital electron and ejects
it. But in the case of Compton interaction, only a part of the
dental x-ray energy is transferred to the electron, and a new,
weaker x-ray is formed and scattered in some new direction
(Figure 2-8). This secondary radiation may travel in a
direction opposite that of the original x-ray. The new x-ray
may undergo another Compton scattering or it may be
A. X-ray
B. Original X-ray
C. New
unmodified X-ray
Nucleus
e–
e– e– e–
e– e–
FIGURE 2-6 X-rays interacting with atom. X-ray (A) passes
through an atom unchanged and no interaction occurs. Incoming
x-ray (B) interacts with the electron by causing the electron to vibrate
at the same frequency as the incoming x-ray. The incoming x-ray
ceases to exist. The vibrating electron radiates new x-ray (C) energy
with the same frequency and energy as the original incoming x-ray.
The new x-ray is scattered in a different direction than the original
x-ray.
CHAPTER 2 • CHARACTERISTICS AND MEASUREMENT OF RADIATION 15
PRACTICE POINT
“How long should you wait after exposure before entering
the room where the radiation was?”
X-rays travel at the speed of light and cease to exist
within a fraction of a second. This question is similar to asking, “How long will it take for the room to get dark after
turning off the light switch?”
Units of Radiation
The terms used to measure x-radiation are based on the ability
of the x-ray to deposit its energy in air, soft tissues, bone, or
other substances. The International Commission on Radiation
Units and Measurements (ICRU) has established standards
that clearly define radiation units and radiation quantities
(Table 2-1). The most widely accepted terms used for radiation
units of measurement come from the Système Internationale
(SI), a modern version of the metric system. The Système
Internationale (SI) units are
1. Coulombs per kilogram (C/kg)
2. Gray (Gy)
3. Sievert (Sv)
Older traditional units of radiation measurement are now
considered obsolete, although they may be observed in some
absorbed by a photoelectric effect interaction. The positive
ion atom combines with a free electron, and the absorbing
material is restored to its original condition. It is important
to remember that the Compton effect causes x-rays to be
scattered in all directions.
• Compton effect accounts for about 60 percent of the
interactions of matter with the dental x-ray beam.
A question often asked is, “Do x-rays make the material
they pass through radioactive?” The answer is no. Dental
x-rays have no effect on the nucleus of the atoms they interact
with. Therefore, equipment, walls, and patients do not become
radioactive after exposure to x-rays.
older documents, especially those dealing with health and
safety. The traditional units are
1. Roentgen (R)
2. Rad (radiation absorbed dose)
3. Rem (roentgen equivalent [in] man)
The American Dental Association requires the use of SI terminology on national board examinations, and following the
guidelines established by the National Institute of Standards
and Technology, this book will use SI units first, followed by
the traditional units in parentheses. It is important to note that
numerical amounts of radiation expressed using SI terminology
do not equal the numerical amounts of radiation expressed
using the traditional terms. For example, consider the metric
system of measurement adopted by most of the world with the
traditional units of measurement used in the United States.
Whereas the global community uses the term kilometers to
measure distance, in the United States distance is more commonly measured in miles. One kilometer does not equal 1 mile.
Instead, 1 kilometer equals approximately 0.62 miles. When
comparing measurements of radiation, it is important to
remember that SI units and traditional units, although measuring the same thing, are not equal numerically.
A “quantity” may be thought of as a description of a physical concept such as time, distance, or weight. The measure of
the quantity is a “unit” such as minutes, miles (kilometers), or
pounds (kilograms).
For practical x-ray protection measurement the following
are used:
1. Exposure
2. Absorbed dose
3. Dose equivalent
4. Effective dose equivalent
Exposure
Exposure can be defined as the measurement of ionization in
air produced by x- or gamma rays. The unit for measuring
exposure is coulombs per kilogram (C/kg) (roentgen (R)). A
coulomb is a unit of electrical charge. Therefore, the unit C/kg
measures electrical charges (ion pairs) in a kilogram of air.
Coulombs per kilogram (roentgen) only applies to x- or gamma
radiation and only measures ion pairs in air. It does not measure
the radiation absorbed by tissues or other materials. Therefore,
it is not a measurement of dose. An exposure does not become
a dose until the radiation is absorbed in the tissues.
TABLE 2-1 Radiation Measurement Terminology
QUANTITY SYSTÈME INTERNATIONAL (SI) UNIT TRADITIONAL UNIT
Exposure coulombs per kilogram (C/kg) roentgen (R)
Absorbed dose gray (Gy) rad
Dose equivalent sievert (Sv) rem
Radon & thoron
(background) (37%)
Space
(background) (5%)
Internal
(background) (5%)
Terrestrial
(background) (3%)
Computed tomography
(medical) (24%)
Nuclear medicine
(medical) (12%)
Interventional fluoroscopy
(medical) (7%)
Conventional radiography/
fluoroscopy (medical) (5%)
Consumer (2%)
Occupational (<0.1%)
Industrial (<0.1%)
FIGURE 2-9 Annual effective dose equivalent of ionizing radiations. This chart illustrates
the approximate percentage of exposure of the U.S. population to background and artificial
radiations.(Reprinted with permission of the National Council on Radiation Protection and Measurements,
http://NCRPonline.org)
Effective Dose Equivalent
To aid in making more accurate comparisons between different radiographic exposures, the effective dose equivalent is
used to compare the risk of the radiation exposure producing
a biological response. The effective dose equivalent is
expressed using the term microsievert (μSv), meaning
1/1,000,000 of a sievert. The effective dose equivalent compensates for the differences in area exposed and the tissues,
critical or less critical, that may be in the path of the x-ray
beam. For example, comparing the skin dose of a chest x-ray
(approximately 0.2 mSv) and a single periapical radiograph
(approximately 2.5 mSv) does not take into consideration
that the chest x-ray delivers its dose to a larger area and to
more tissues than the single periapical radiograph. Using the
measurement for effective dose equivalent, the chest x-ray is
approximately 80 μSv, and the effective dose equivalent for the
single periapical using F-speed film and a round PID is
approximately 1.3 μSv.
Background Radiation
Dental x-rays are artificially produced, and when grouped with
medical x-rays they account for approximately 5 percent of the
total radiation exposure to the population. In fact, the total radiation exposure to the U.S. population from all medical applications of ionizing radiation including x-rays, computed
tomography (CT scans), and nuclear medication is approximately 48 percent. Consumer products and activities such as
smoking, building materials, and combustion of fossil fuels
make up another approximately 2 percent of exposure to the
population. However, it is important to note 50 percent of total
exposure to the population comes from naturally occurring,
background sources of radiation (Figure 2-9). Background
16 HISTORICAL PERSPECTIVE AND RADIATION BASICS
Absorbed Dose
Absorbed dose is defined as the amount of energy deposited in
any form of matter (such as teeth, soft tissues, treatment chair,
and so on), by any type of radiation (alpha or beta particles,
gamma or x-rays). The unit for measuring the absorbed dose is
the gray (Gy) (rad).
One gray equals 1 joule (J; a unit of energy) per kilogram
of tissue. One gray equals 100 rads.
Dose Equivalent
Dose equivalent is a term used for radiation protection purposes to compare the biological effects of the various types of
radiation. Dose equivalent is defined as the product of the
absorbed dose times a biological-effect qualifying or
weighting factor. Because the weighting factor for x-rays is 1,
the absorbed dose and the dose equivalent are numerically
equal. The unit for measuring the dose equivalent is the sievert
(Sv) (rem). One sievert is the product of 1 Gy times a biological-effect weighting factor. Because the weighting factor for
x- and gamma radiation equals 1, the number of sieverts is
identical to the absorbed dose in grays for these radiations. One
sievert equals 100 rem.
In dental radiology, gray (rad) and sievert (rem) are equal,
and it should be pointed out that only x-rays and gamma rays
are measured in coulombs per kilogram (roentgens). Gray
(rad) and sievert (rem) are used to measure all radiations:
gamma and x-rays, alpha and beta particles, neutrons, and
high-energy protons.
When pertaining to exposures from dental radiation, smaller
multiples of these units are commonly used. For example, milligray (mGy), where the prefix milli means “one-thousandth of,”
would more likely be used to express the smaller dose of radiation used in most dental applications.
radiation is defined as ionizing radiation that is always present
in our environment. The human race has always been subjected
to exposure from natural background radiations originating
from the following sources:
• Cosmic radiations from outer space
• Terrestrial radiations from the earth and its environments
including radon gas
• Background radiations from naturally occurring
radionuclides (unstable atoms that emit radiations) that
are deposited in our bodies by inhalation and ingestion
The average natural background radiation levels for the U.S.
population is estimated to be about 3.1 mSv (millisievert) or
310 mrem (millirem) per year or about 0.9 mrem per day.
The exact amount varies according to locality, the amount of
radioactive material present, and the intensity of the cosmic
rays—this intensity varies according to altitude and latitude.
For example, persons living on the Colorado plateau receive
an increased dose of background radiation because of the
increased cosmic radiation at the higher altitude and more
terrestrial radiation from soils enriched in naturally occurring
uranium that raise the levels of terrestrial radionuclides
located there.
REVIEW—Chapter summary
The three basic building blocks of an atom are protons, neutrons, and electrons. Protons and neutrons make up the central
nucleus, which is orbited by the electrons revolving in the
energy levels. Binding energy between the positive protons and
negative electrons maintains the electrons in their orbits.
Ionization is the formation of charged particles called ions.
A positive ion and a negative ion are called an ion pair. Ionizing
radiation is defined as any radiation that produces ions.
Electromagnetic radiation is the movement of wavelike
energy through space. Electromagnetic radiation exhibits the
properties of wavelength, frequency, and velocity. Shortwavelength x-rays, called hard radiation, are very penetrating.
Long-wavelength x-rays, called soft radiation, have limited
penetrating power. The electromagnetic spectrum consists of
an orderly arrangement of all known radiant energies.
X-rays are invisible, travel in straight lines at the speed of
light, interact with matter causing ionization, affect photographic film, and affect living tissue. X-rays are produced
whenever high-speed electrons are abruptly stopped or slowed
down. They may pass through a patient with no interaction, or
they may be absorbed by the photoelectric effect or scattered by
either Compton scattering or coherent scattering.
Four x-ray measurement quantities are exposure (C/kg;
roentgen), absorbed dose (gray/Gy; rad), dose equivalent (sievert/Sv; rem), and effective dose equivalent (microsievert/μSv).
Dental and medical x-rays make up approximately 5 percent
of the total radiation exposure to the U.S. population. All medical
uses of ionizing radiations including CT scans and nuclear medicine account for 48 percent of the total ionizing radiation exposure. Background radiation consisting of cosmic radiation,
CHAPTER 2 • CHARACTERISTICS AND MEASUREMENT OF RADIATION 17
terrestrial radiations and radon gas, and naturally occurring
radionuclides that are deposited in our bodies by inhalation and
ingestion accounts for 50 percent of the total radiation exposure.
The average natural background radiation levels for the U.S.
population is estimated to be about 3.1 mSv (millisievert) or
310 mrem (millirem) per year or 0.9 mrem per day.
RECALL—Study questions
1. What term describes the smallest particle of an element
that retains the properties of that element?
a. Atom
b. Molecule
c. Photon
d. Isotope
2. Draw and label a typical atom.
3. Which of these subatomic particles carries a negative
electric charge?
a. Proton
b. Neutron
c. Nucleus
d. Electron
4. Radiant energy sufficient to remove an electron from its
orbital level of an atom is called
a. atomic.
b. electronic.
c. ionizing.
d. ultrasonic.
5. What term describes the process by which unstable
atoms undergo decay in an effort to obtain nuclear
stability?
a. Absorption
b. Radioactivity
c. Radiolucent
d. Ionization
6. Which of the following is NOT a property shared by all
energies of the electromagnetic spectrum?
a. Have energy that is measurable and different
b. Travel in a pulsating motion at the speed of sound
c. Have no electrical charge, mass, or weight
d. Emit an electrical field at right angles to the path of
travel
7. What is the distance between two similar points on two
successive waves called?
a. Wavelength
b. Frequency
c. Velocity
d. Energy level
18 HISTORICAL PERSPECTIVE AND RADIATION BASICS
8. Which of these electromagnetic radiations has the
shortest wavelength?
a. Radar
b. Ultraviolet rays
c. Infrared rays
d. X-rays
9. Which of these forms of radiation has the greatest penetrating power?
a. Visible light
b. X-rays
c. Sunlamp
d. Radio waves
10. Which of these forms of radiation is least capable of
causing ionization of body tissue cells?
a. Cosmic rays
b. Gamma rays
c. X-rays
d. Infrared light
11. List five properties of x-rays.
a. ______________
b. ______________
c. ______________
d. ______________
e. ______________
12. Radiation produced when high-speed electrons are
stopped or slowed down by the tungsten atoms of the
dental x-ray tube is called
a. general/bremsstrahlung.
b. characteristic.
c. coherent.
d. Compton.
13. What term best describes the process of transferring
x-ray energy to the atoms of the material through which
the x-ray beam passes?
a. Compton scattering
b. Photoelectric effect
c. Absorption
d. Bremsstrahlung
14. Which of these terms is the unit used to measure radiation exposure?
a. Angstrom (Å)
b. Gray (rad)
c. Sievert (rem)
d. Coulombs per kilogram (roentgen)
15. The Système Internationale (SI) unit that has replaced
the traditional unit rem is
a. gray.
b. sievert.
c. rad.
d. coulomb/kilogram.
16. Dental and medical x-rays account for what percentage
of the overall total exposure to ionizing radiation to an
individual in the United States?
a. 5
b. 10
c. 25
d. 50
17. List three sources of background radiation.
a. ______________
b. ______________
c. ______________
18. What is the average amount of background radiation
to an individual in the United States?
a. 2.2 mSv (220 millirem) per year
b. 4.2 mSv (420 millirem) per year
c. 3.1 mSv (310 millirem) per year
d. 8.2 mSv (820 millirem) per year
REFLECT—Case study
While taking a full mouth series of dental radiographs on your
patient, he begins to consider the number of radiographs that
are exposed in this operatory on a daily basis. He decides to ask
you questions such as, “How long do you have to wait after
each exposure before you can re-enter the room?” and “Are the
walls and equipment in this room becoming radioactive from
all the exposures taken in here?” Prepare a conversation with
this patient addressing these two questions based on what you
learned in this chapter on radiation physics.
RELATE—Laboratory application
Research recent media (magazine or journal articles, newspaper
reports, or the Web) for stories on radiation exposure. Select an
article for review, and critique the article for clarity and readibility. Summarize how many different types of radiation are mentioned in the article. What units of radiation measurement does
the author use? Does the article use these terms in a manner that
is appropriate for what is being measured? Consider the type of
radiation described in this article. Is it naturally occuring/background radiation or a radiation generated by an artificial or manmade source? How many key words from this chapter can you
find in the article? Anticipate what questions your patient may
have for you after reading this article.
REFERENCES
Bushberg, J. T., Seibert, J. A., Leidholdt, E. M., Jr., & Boone, J.
M. (2001). The essential physics of medical imaging (2nd
ed.). Baltimore: Lippincott Williams & Wilkins.
National Council on Radiation Protection and Measurements.
(2009). Report No 160: Ionizing radiation exposure of the
population of the United States. Bethesda, MD: Author.
Taylor, B. N., & Thompson, A. (Eds.). (2008). The international system of units. Washington, DC: National Institute
of Standards and Technology, U. S. Dept. of Commerce,
Special Publication 330.
Thompson, A., & Taylor, B. N. (2008). Guide to the SI, with
a focus on usage and unit conversions. Guide for the use
of the international system of units (SI). National Institute of Standards and Technology Special Publication
811.Gaithersburg, MD: National Institute of Standards
and Technology.
United States Nuclear Regulatory Commission, Office of Public Affairs. (2003). Fact sheet. Washington, DC: Author.
United States Nuclear Regulatory Commission. (2007, December 4). Standards for protection against radiation, Title 10,
Part 20, of the Code of Federal Regulations. Retrieved
April 11, 2010, from http://www.nrc.gov/reading-rm/doccollections/cfr/part020/part020-1201.html
White, S. C., & Pharoah, M. J. (2008). Oral radiology. Principles and interpretation (6th ed.). St. Louis, MO: Mosby
Elsevier.
CHAPTER 2 • CHARACTERISTICS AND MEASUREMENT OF RADIATION 19
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Identify the three major components of a dental x-ray machine.
3. Identify and explain the function of the five controls on the control panel.
4. State the three conditions necessary for the production of x-rays.
5. Draw and label a dental x-ray tube.
6. Identify the parts of the cathode and explain its function in the production of x-rays.
7. Identify the parts of the anode and explain its function in the production of x-rays.
8. Trace the production of x-rays from the time the exposure button is activated until x-rays are
released from the tube.
9. Demonstrate, in sequence, steps in operating the dental x-ray machine.
KEY WORDS
Alternating current (AC)
Amperage
Ampere (A)
Anode
Autotransformer
Cathode
Central ray
Collimator
Control panel
“Dead-man” exposure switch
Direct current (DC)
Electrical circuit
Electric current
Electrode
Electron cloud
Exposure button
Extension arm
Filament
Filter
Focal spot
Focusing cup
Impulse
Incandescence
Intensity
Kilovolt (kV)
Kilovolt peak (kVp)
The Dental X-ray
Machine: Components
and Functions
CHAPTER
OUTLINE
 Objectives 20
 Key Words 20
 Introduction 21
 Evolution of the
Dental X-ray
Machine 21
 Dental X-ray
Machine
Components 21
 Electricity 24
 The X-ray Tube 26
 A Summary of the
Principles of X-ray
Tube Operation 27
 The X-ray Beam 28
 Operation of the
Dental X-ray
Machine 28
 Review, Recall,
Reflect, Relate 29
 References 31
CHAPTER
3
KEY WORDS
CHAPTER 3 • THE DENTAL X-RAY MACHINE: COMPONENTS AND FUNCTIONS 21
Introduction
At the time of exposure, the radiographer who activates the exposure button is responsible for the radiation dose the patient
incurs. The role of exposing dental radiographs is an important
one for the dental assistant and dental hygienist, making it essential that these professionals understand how the x-ray machine
works to produce ionizing radiation. To operate dental x-ray
equipment safely and competently, the radiographer needs to
develop a base knowledge of the components of the dental x-ray
machine and possess an understanding of how these components
work together to produce ionizing radiation. The purpose of this
chapter is to discuss the conventional dental x-ray machine, its
components, and its functions.
Evolution of the Dental X-ray Machine
Improvements in early x-ray generating machines began to
occur after the dangers of radiation exposure became evident.
The Coolidge hot cathode vacuum tube, invented by Dr. W. D.
Coolidge in 1913, improved the previous erratic radiation output
of earlier machines. Then during the mid-1950s, variable kilovoltage machines were introduced that allow for different penetrating abilities of the x-beam. In 1966, the recessed PID was
introduced (Figure 3-1). On x-ray machines of conventional
design, the x-ray tube is located in the front section of the tube
head; on those using a recessed design, the x-ray tube is located
in the back of the tube head. This configuration allows for a
sharper image. (The role a longer x-ray tube-to-object distance
plays in producing sharp images will be discussed in Chapter 4.)
In 1974, the federal government began regulating the manufacture and installation of all dental x-ray machines. State and
local governing agencies also set guidelines on the safe installation and use of dental x-ray equipment. New technology
employing miniaturized solid-state transformers and rare-earth
materials for filtration of the x-ray beam have also contributed
to the development of a modern dental x-ray machine that is
safe, compact, easy to position, and simple to operate.
Dental X-ray Machine Components
Although dental x-ray machines vary in size and appearance, they
have similar structural components (Figure 3-2). The dental x-ray
machine typically consists of three parts:
1. The control panel, which contains the regulating devices
2. The extension arm or bracket, which enables the tube
head to be positioned
3. The tube head, which contains the x-ray tube from which
x-rays are generated
A B
FIGURE 3-1 Comparison of conventional and recessed tube position within the tube head.
(A) Conventional position with tube in front of tube head. Note how quickly the x-ray beam pattern
flares out. (B) With a recessed tube a relatively more parallel x-ray beam is produced. This will produce a
sharper radiographic image.
Kinetic energy
Line switch
Milliampere (mA)
Polychromatic
Port
Primary beam
Quality
Quantity
Tungsten
Useful beam
Volt (V)
Voltage
Voltmeter
X-ray tube
Yoke
Radiator
Step-down transformer
Step-up transformer
Target
Thermionic emission
Timer
Transformer
Tube head
22 HISTORICAL PERSPECTIVE AND RADIATION BASICS
Folding extension arm
Handle for ease of
directing the horizontal
angulation
Control panel key pad
Digital sensor in holder
Dial for reading the
vertical angulation
of tube head
Yoke rotates 360°
horizontally at this point
Open-ended position
indicating device (PID)
FIGURE 3-2 Typical wall-mounted dental x-ray machine. (Image courtesy of Progeny,
A Midmark Company)
Control Panel
The electric current enters the control panel either through a
cord plugged into a grounded outlet in the wall or through a
direct connection to a power line in the wall. The control panel
may be integrated with the extension arm and tube head for ease
of access during exposures (Figure 3-3), or it may be remote
FIGURE 3-3 Control panel integrated with tube head
support. (Image courtesy of Gendex Dental Corporation)
from the unit, mounted on a shelf or wall (Figure 3-4). One
control panel may serve two or more tube heads. In the past
dental x-ray machines were readily available with variable milliamperage and kilovoltage controls of the incoming electricity
that the operator would manually adjust (Figure 3-5). Increasingly more common are dental x-ray machines with these controls preset by the manufacturer (Figure 3-6). If the milliamperage
and the kilovoltage are preset by the manufacturer, the control
panel will indicate at what variables these units are preset. Five
major controls may be operated or will be preset on dental x-ray
machines: (1) the line switch to the electrical outlet, (2) the
milliampere selector, (3) the kilovoltage selector, (4) the timer,
and (5) the exposure button. The function of each of these is
discussed next.
LINE SWITCH The line switch on the control panel of the
dental x-ray machine may be a toggle switch that can be
flicked on or off with light finger pressure, or it may be an
ON/OFF push button or a keypad (Figure 3-5). It is generally
located on the side or face of the cabinet or control panel. In
the ON position, this switch energizes the circuits in the control panel, but not the low- or high-voltage circuits to the transformers. An indicator light turns on, indicating the machine is
operational.
MILLIAMPERE (mA) SELECTOR The milliampere measures
the amount of current passing through the wires of the circuit. The
amperage is set by turning a selector knob, depressing the marked
push button, or touching a keypad. (Figure 3-5). On a dental x-ray
machine with the amperage preset, its activation is connected
CHAPTER 3 • THE DENTAL X-RAY MACHINE: COMPONENTS AND FUNCTIONS 23
directly to the ON/OFF switch. The amperage determines the
available number of free electrons at the cathode filament and,
therefore, the amount of x-rays that will be produced.
KILOVOLT PEAK (kVp) SELECTOR The voltmeter measures the
difference in potential or voltage across the x-ray tube. A kilovolt
peak (kVp) selector in the form of a dial, push button, knob, or
keypad enables the operator to change the peak kilovoltage
(Figure 3-5). On a dental x-ray machine with the kVp preset, its
activation is connected directly to the ON/OFF switch. The kVp
determines the speed of electrons traveling toward the target on the
anode and, therefore, the penetrating ability of the x-rays produced.
FIGURE 3-4 Control panel mounted in protected area.
1 23 4 5 6 7 8 9
FIGURE 3-5 Control panel of a dental x-ray machine that
allows for manual adjustment of exposure variables. (1) Exposure
button holder, (2) main ON/OFF switch, (3) mA control, (4) x-ray
tube selector (this master control accommodates three remote tube
heads), (5) power ON light, (6) x-ray emission indicator light,
(7) timer control, (8) kVp meter, (9) kVp control. This control panel
allows the operator to choose settings of 50 kVp to 90 kVp at 15 mA,
and 50 kVp to 100 kVp at 10 mA.
TIMER The timer is set by turning the selector knob, depressing the marked push button, or touching a keypad (Figure 3-6).
The timer serves to regulate the duration of the interval that the
current will pass through the x-ray tube. Dental x-ray machines
are equipped with accurate electronic timers. Timer settings
may be in fractions of a second or impulses. There are 60 impulses
in a second. For example, a 1/10th of a second exposure lasts 6
impulses, 1/5th of a second lasts 12 impulses, and so forth.
X-ray machines with electronic digital timers are accurate to
1/100th of a second intervals and work well with digital radiography systems. The time selected determines the duration of the
exposure.
FIGURE 3-6 Operator setting the exposure time. The display
indicates 16 impulses. Note the preset milliamperage and kilovoltage
values.
24 HISTORICAL PERSPECTIVE AND RADIATION BASICS
FIGURE 3-7 Exposure button on the handle of the timer
cord. Operator is exposing a panoramic radiograph from behind
a lead-lined glass window.
EXPOSURE BUTTON Depressing the exposure button or keypad activates the x-ray production process. The exposure button
may be located on the handle of the timer cord (Figure 3-7) or at
a remote location in a protected area (Figure 3-4). If the exposure
button is located on the end of the timer cord, the cord must be
sufficiently long to enable the operator to step into an area of protection from radiation, usually at least 6 ft (1.83 m) from the
source of the x-ray beam. Because the possibility exists that the
operator may not utilize the full length of the timer cord to be
safely protected from the x-rays generated, an exposure switch
permanently mounted to the control panel or wall in a protected
area is preferred. In fact, many state regulations now require that
the exposure button be permanently mounted in a protected area.
Older x-ray machines equipped with exposure buttons on timer
cords must be modified to attach the exposure button to an
unmovable, permanent mount to meet this requirement.
All dental x-ray machines are required to be equipped with a
“dead-man” exposure switch that automatically terminates the
exposure when the operator’s finger ceases to press on the timer button. This makesit necessary to maintain firm pressure on the button
during the entire exposure. Failure to do so results in the formation
of an insufficient number of x-rays to properly expose the image
receptor (film or digital sensor). When the exposure button is activated, the operator will hear an audible beep (required by law) that
indicates x-rays are being generated. Additionally, exposure buttons installed directly on the control panel allow the operator to
observe a light indicating that x-rays are being generated.
The manufacturing trend is toward simpler and automated
controls. In addition to preset milliamperage and kilovoltage,
many dental x-ray machines now have a default timer that automatically resets itself and does not have to be altered unless a
change in the exposure time is desired. Also available are programmable preset exposure settings that the operator can select
directly from the tube head for quickly changing the settings
chairside (Figure 3-3).
Extension Arm
The folding extension arm is a support from which the tube
housing is suspended (Figure 3-2). The extension arm allows
for moving and positioning the tube head. The extension arm is
hollow to permit the passage of electrical wires from the control panel to the tube head from one or both sides at a point
where the tube head attaches to the yoke. The tube head is
attached to the extension arm by means of a yoke that can
revolve 360 degrees horizontally where it is connected. In addition, the tube head can be rotated vertically within the yoke. All
sections of the extension arm and yoke are heavily insulated to
protect the patient and the operator from electrical shock.
Tube Head (Tube Housing)
The tube head (sometimes called tube housing; Figure 3-8) is a
tightly sealed heavy metal (usually cast aluminum), lead-lined
housing that contains the dental x-ray tube, insulating oil, and
step-up and step-down transformers. The metal housing performs
several important functions:
1. Protects the x-ray tube from accidental damage
2. Increases the safety of the x-ray machine by grounding its
high-voltage components (the x-ray tube and the transformers) to prevent electrical shock
3. Prevents overheating of the x-ray tube by providing a
space filled with oil, gas, or air to absorb the heat created
during the production of x-rays
4. Lined with lead to absorb any x-rays produced that do not
contribute to the primary beam that exits through the port
in the direction of the position indicating device (PID)
Older dental x-ray machine tube heads are heavy and bulky.
The trend is toward using lighter weight materials and miniaturized solid-state components. Reducing the size and the weight
of the tube head helps make it easier for the operator to position.
Electricity
Because electricity is needed to produce dental x-rays, an
understanding of basic electrical concepts is necessary. Electricity can be defined as electrons in motion. An electric current is a movement of electrons through a conducting medium
(such as copper wire). Electric current can flow in either
direction along a wire or conductor. It can flow steadily in one
direction (direct current) or flow in pulses and change directions
(alternating current).
PRACTICE POINT
After use, the extension arm bracket should be folded into a
neutral, closed position. The tube head is finely counterbalanced in its suspension from the extension arm. This balance
can be disturbed if the tube head is left suspended for prolonged time periods with the extension arm stretched out.
This may lead to instability and tube head drifting.
CHAPTER 3 • THE DENTAL X-RAY MACHINE: COMPONENTS AND FUNCTIONS 25
Direct Current
Direct current (DC) flows continuously in one direction. The
unidirectional current is similar to that used in flashlight batteries. Direct current dental x-ray machines are well suited for use
with digital imaging (see Chapter 9).
Alternating Current
The household current used in the United States is a 110-V or
220-V, 60-cycle alternating current (AC), which changes its
direction of flow 60 times per second (Figure 3-9). The alternating current has two phases—one positive and the other negative—
and alternates between these phases.
Electrical Circuit
The path the electricity flows is called an electrical circuit. Two
electrical circuits are used in producing dental x-rays.
1. A filament circuit provides low voltage (3–8 V) to the filament of the x-ray tube to generate a source of electrons
needed for the production of x-rays.
2. A high-voltage circuit provides the high voltage (60–100
kV) necessary to accelerate the electrons from the cathode
filament to the anode target.
Transformers
A transformer is an electromagnetic device for changing the
current coming into the dental x-ray machine. Transformers are
required to decrease (step down) or increase (step up) the ordinary 110-V or 220-V current that enters the x-ray machine. The
step-down and step-up transformers are located in the tube head.
Step-down Transformer
A step-down (low-voltage) transformer decreases the voltage
from the wall outlet to approximately 5 V, just enough to heat
the filament and form an electron cloud.
Step-up Transformer
A step-up (high-voltage) transformer increases the voltage
from the wall outlet to approximately 60–100 kVp to propel the
electrons toward the target. The high-voltage current begins to
flow through the cathode–anode circuit when the exposure button on the line switch is depressed.
Autotransformer
An autotransformer, located in the control panel, is a voltage
compensator that corrects minor fluctuations in the current
flowing through the wires.
High-voltage
transformer
X-ray
Oil
Port Low-voltage
transformer
X-rays
Filter
PID
Collimator
Primary beam
Tube
head
Central ray
Focusing
cup
Electron
cloud
Tungsten
target Anode
Copper
stem
Cathode
X-ray
Filament
Window
Vacuum
Radiator
FIGURE 3-8 Dental x-ray tube head, containing x-ray tube, transformers, and oil. When an electric current is
applied to the high-voltage circuit (between the cathode and the anode), the boiled off electrons are propelled from
the cathode to the target on the anode, producing heat and x-rays. Although x-rays are emitted in all directions,
because of the 20-degree angle of the anode target most of the x-rays travel through the window toward the port
opening. These x-rays make up the primary x-ray beam. The central ray is the x-ray in the center of the primary beam.
26 HISTORICAL PERSPECTIVE AND RADIATION BASICS
A kilovolt equals 1,000 V and is abbreviated kV. The voltage
varies during an exposure, producing a polychromatic beam
(x-rays of many different energies) containing high-energy
rays and also containing soft rays that have barely enough
energy to escape from the tube. The highest voltage to which
the current in the tube rises during an exposure is called the
kilovolt peak (kVp). So if the x-ray machine controls are set at
75 kVp (75,000 V), the maximum x-ray energy that can be
produced during this exposure is 75 kVp. Dental x-ray
machines typically operate within a range of 60 kVp to 100
kVp. The setting will vary by manufacturer and is usually preset, although some x-ray machines allow the operator to choose
the setting best suited for the exposure.
The X-ray Tube
X-rays are produced when a stream of high-speed electrons are
suddenly stopped or slowed down and diverted off course.
Three conditions must exist for x-rays to be produced:
1. An available source of free electrons
2. High voltage to impart speed to the electrons
3. A target that is capable of stopping/slowing the electrons
The x-ray tube and the circuits within the machine are designed
to create these conditions. The x-ray tube, located inside the
tube head, is a glass bulb from which the air has been pumped
to create a vacuum. A cathode (the negative electrode) and an
anode (the positive electrode) are sealed within the vacuum
tube, and the two protruding arms of the electrodes permit the
passage of the current through the tube with minimum resistance.
The electrical terms amperage, the measurement of the
number of electrons moving through a wire conductor, and
voltage, the measurement of electrical force that causes electrons to flow through a conductor, will be used to describe the
x-rays generated.
Amperage
Amperage measures the number of electrons that move
through a conductor. The ampere (A) is the unit of quantity of
electric current. An increase in amperage results in an increase
in the number of electrons that is available to travel from the
cathode to anode when the tube is activated. This results in a
production of more x-rays. Only a small current is required to
generate a number of electrons necessary to produce dental
x-rays; therefore, the term milliampere (mA), denoting 1/1,000th
of an ampere, is used. Dental x-ray machines typically operate
in ranges from 4 to 15 mA. The setting will vary by manufacturer and is usually preset, although some x-ray machines
allow the operator to choose the setting best suited for the
exposure.
Voltage
Voltage or volt (V) is the electrical pressure (sometimes called
potential difference) between two electrical charges. In the
production of x-rays the voltage determines the speed of the
electrons when traveling from cathode to anode. This speed of
the electrons, in turn, determines the energy (penetrating
power) of the x-rays produced. When the voltage is increased,
the electrons travel faster and produce a harder type of radiation. Because dental x-ray machines operate at very high voltages, it is customary to express voltage in terms of kilovolts.
90
70
50
90
70
50
kVp 0
1 impulse
sec
sec
Time
1
120 1
60
x-rays x-rays
no
x-rays
no
x-rays
FIGURE 3-9 Sine wave of 60-cycle alternating current
operating at 90,000 V (90 kVp). Ordinary household electric
current is called 60-cycle alternating current because the current
changes its direction of flow 60 times a second. During the time
that the x-ray tube is producing x-rays, the cathode and the anode
each change from negative to positive 60 times per second.
The crest of the wave represents the maximum voltage when the
current is moving in one direction, while the trough of the wave
represents the maximum voltage when the current is moving in
the other direction. The total cycle takes place in 1/60 sec.
This alternation in current direction occurs every 1/120 sec (twice
during each full cycle) on x-ray machines using alternating
current, producing x-rays in a series of bursts, or impulses, rather
than in a continuous flow.
CHAPTER 3 • THE DENTAL X-RAY MACHINE: COMPONENTS AND FUNCTIONS 27
In most dental x-ray tubes, the space between the electrodes is
less than 1 in. (25.4 mm; Figure 3-10).
Cathode
The purpose of the cathode is to supply the electrons necessary
to produce x-rays. The cathode, or negative electrode, consists
of a thin, spiral filament of tungsten wire. This filament wire,
when heated to incandescence (red hot and glowing), produces
the electrons (Figure 3-11). This process is known as thermionic
emission. A familiar example of this phenomenon is the tungsten electric lightbulb. Tungsten’s high atomic number makes it
possible to liberate electrons, through thermionic emission,
from their orbital shells when the metal is heated. The released
electrons form an electron cloud around the wire. The wire filament is recessed into a molybdenum focusing cup, which
directs the electrons toward the target on the anode (Figure 3-12).
The milliamperage setting accurately controls the thermionic
emission and therefore controls the quantity of free electrons
available.
Anode
The kilovoltage imparts speed to the electrons sending them
flying across the tube from cathode to anode. The purpose of
the anode is to provide the target to stop or significantly slow the
high-velocity electrons, converting their kinetic energy into x-rays
(electromagnetic energy). The anode, or positive electrode, consists of a copper bar with a tungsten plate imbedded in the end
that faces the focusing cup of the cathode. This tungsten plate,
called the target, is set into the copper at an angle of 20 degrees
to the cathode. This angle directs most of the x-rays produced
in one direction to become the primary beam. The focal spot
is a small rectangular area on the target of the anode to which
the focusing cup directs the electron beam. In Chapter 4 we will
see that the smaller the focal spot, the sharper the radiographic
image.
In summary, when the tube is in operation, a cloud of electrons first forms around the filament wire of the cathode as the
tube warms. Then, when the high-voltage current is applied, these
electrons are attracted and electrically charged to propel toward
the focal spot on the target.
A Summary of the Principles of X-ray
Tube Operation
Before x-ray production can begin, the machine must be turned
on. If not preset by the manufacturer, the radiographer must set
the correct mA and kVp by adjusting the dials on the control
panel. The radiographer will then set the correct exposure time.
The process of x-ray production is initiated by firmly pressing
the exposure button. This permits the current to enter the filament circuit of the x-ray machine. A step-down transformer
reduces the voltage before it enters the filament circuit and heats
the filament of the cathode to incandescence, separating electrons from their atoms. The degree to which the filament is
heated depends on the milliamperage setting: The higher the
mA, the more electrons in the electron cloud. These electrons
are now in a state of excitation as they hover around the tungsten
filament recessed in the molybdenum focusing cup. After just a
FIGURE 3-10 Dental x-ray tube.
Hot
object
Electron
cloud
Electron emission from hot object
FIGURE 3-11 Cross section of a filament wire. The filament
wire in the cathode is heated to incandescence. The attached electrons
are literally boiled out of the wire and become available as a source
of free electrons necessary for x-ray production. The milliamperage
setting determines the number of electrons available to be accelerated
across to the target of the anode.
Focusing cup
(reflector)
Hot filament
− emitting
electrons
− Electron beam
FIGURE 3-12 Formation of electron beam by focusing cup.
A focusing cup, within the cathode structure into which the filament
is placed, focuses the electron beam in a similar manner as light is
focused by a flashlight reflector. When the high-voltage circuit is
activated, the free electrons are accelerated toward the focal spot on
the anode target.
28 HISTORICAL PERSPECTIVE AND RADIATION BASICS
fraction of a second time delay, the line current enters the cathode–anode high-voltage circuit. A step-up transformer then
increases the voltage to impart sufficient force to propel the free
electrons toward the focal spot on the target at the anode. These
high-velocity electrons are stopped or slowed when they collide
with the tungsten atoms in the target resulting in the production of
general radiation (bremsstrahlung) and/or characteristic radiation. (This process is explained fully in Chapter 2.) The kinetic
energy (the high-velocity electrons) is converted into approximately 1 percent x-ray energy. The other 99 percent of the
kinetic energy generated is lost as heat energy.
The metal tungsten (symbol W and atomic number 74;
also known as wolfram) is ideally suited for use in the filament
and target because it can withstand extremely high temperatures (melting point 3370°C). Because it is subjected to such
extreme heat and has low thermal conductivity, the tungsten
plate is imbedded in a core of copper. Copper is highly conductive and carries the heat generated off to the radiator, which is
just outside the tube (refer to the tube diagram in Figure 3-8).
The large mass of copper conducts the heat out of the tube into
a radiator that transfers the heat to the oil, gas, or air that surrounds the tube.
Although the target is set into the copper at an angle to
direct most of the x-rays toward the window (a thin area in the
glass tube) located at a point where the emission of x-rays is
most intense, some x-rays are emitted out in all directions within
the tube housing. These x-rays are absorbed by the glass tube,
oil, air, wires, transformers, and the tube head lining. If the tube
head is properly sealed, the port (an opening in the tube housing) is the only place through which the x-rays can escape the
tube head (Figure 3-8). The port is covered by a permanent seal
of glass, beryllium, or aluminum. The PID (position indicating
device) fits over the port and can be moved to aim the primary
beam of x-rays in the desired direction. After completion of the
predetermined exposure, the high-voltage current is automatically shut off, and x-ray production stops.
The X-ray Beam
X-rays are produced in 360-degree direction at the focal spot of
the target. However, because of the angle of the anode, a high
concentration of x-rays travels toward the port opening of the
tube head. Only a beam of radiation the size of the port seal is
allowed to exit the tube head. The other x-rays are stopped
(absorbed) by the contents and walls of the tube head. After the
beam exits through the port, the lead collimator (explained in
Chapter 6) further restricts the x-ray beam to the desired size.
The x-ray beam is cone shaped because x-rays travel in
diverging straight lines as they radiate from the focal spot. This beam
of x-rays is called the primary beam or the useful beam. The primary beam is the original useful beam of x-rays that originates
at the focal spot and emerges through the port of the tube head.
The central ray is the x-ray in the center of the primary beam.
The x-ray beam formed at the focal spot is polychromatic,
consisting of x-rays of various wavelengths. Only x-rays with
sufficient energy to penetrate oral structures are useful for
diagnostic dental radiographs. X-rays of low penetrating power
(long wavelength) add to the patient dose but not to the information recorded on the image receptor. To remove the soft xrays, a thin sheet of aluminum called a filter is placed in the
path of the x-ray beam (explained in Chapter 6).
The intensity of the x-ray beam refers to the quantity and
quality of the x-rays. Quantity refers to the number of x-rays in
the beam. Quality refers to the energy strength or penetrating
ability of the x-ray beam (see Chapter 4). Intensity is defined as
the product of the number of x-rays (quantity) and the energy
strength of the x-rays (quality) per unit of area per unit of time.
Intensity of the x-ray beam is affected by milliamperage (mA),
kilovoltage (kVp), exposure time, and distance.
Operation of the Dental X-ray Machine
The specific steps to safe and effective use of a dental x-ray
machine are outlined in the operating manual provided by
the manufacturer. All persons operating an x-ray machine
should study the manual until they are thoroughly familiar
with the operational capability and maintenance requirements of the machine. To achieve consistent results, the radiographer should follow a systematic and orderly procedure
(Procedure Box 3-1). Additionally, whenever x-ray exposures
are made on patients, it is assumed here and in all subsequent
instructions that:
• The radiographer is competent and can follow radiation
safety protocol. (Some states require anyone placing and
exposing dental radiographs to successfully complete a
training course in radiation safety and protection protocols.)
• The radiographer performs all radiographic procedures in
accordance with federal, state, and local regulations and
recommendations.
• Infection control is maintained throughout the procedure
(see Chapter 10).
• The procedure has been explained, and the patient has
given consent.
• The patient has received verbal instructions and is able to
cooperate with the procedure.
• Image receptor holding devices are utilized for all intraoral
radiographs.
PRACTICE POINT
For maximum effectiveness in exposing dental radiographs,
prepare the patient and the x-ray equipment and set the
controls on the x-ray unit prior to positioning the image
receptor in the oral cavity. Following an orderly sequence
reduces the likelihood of errors and retakes.
CHAPTER 3 • THE DENTAL X-RAY MACHINE: COMPONENTS AND FUNCTIONS 29
1. Turn power on. A light on the control panel will indicate that the machine is ready to
operate.
2. Unless preset by the manufacturer, select mA and kVp best suited for the exposure to be
made.
3. Set timer for the desired exposure time.
4. Place the image receptor into the holding device and position in the patient’s oral cavity.
5. Utilizing the extension arm and yoke, adjust the tube head by aligning the PID so that the
central beam of radiation is directed toward the center of the image receptor at the appropriate horizontal and vertical angulations.
6. Establish appropriate protected location from the tube head.
7. Depress exposure button and hold it down firmly until the exposure is completed. The audible signal and x-ray exposure indicator light will activate for the duration of the exposure.
8. Remove the image receptor and holder from the patient’s oral cavity after the exposure.
9. When the procedure is complete, fold the tube head support extension arm into the closed,
neutral position.
10. Turn off the power to the x-ray machine.
PROCEDURE 3-1
Operation of the dental x-ray machine
REVIEW—Chapter summary
All x-ray machines, regardless of size and voltage range, operate similarly and have the same components (control panel,
extension arm, and tube head) and electrical parts (x-ray tube,
low- and high-voltage circuits, and a timing device).
The control panel may be integrated with the x-ray
machine tube head support, or it may be remote from the unit,
mounted on a shelf or wall. There are five major controls, some
of which will be preset by the manufacturer or may be selected
by the operator: (1) the line switch to the electrical outlet, (2) the
milliampere selector, (3) the kilovoltage selector, (4) the timer,
and (5) the exposure button.
A folding extension arm is a support from which the tube
housing is suspended. The tube head is a tightly sealed heavy
metal housing that contains the dental x-ray tube, insulating oil,
and step-up and step-down transformers.
Three conditions must exist to produce x-rays: (1) a source
of free electrons, (2) high voltage to accelerate them, and (3) a
target to stop them. The dental x-ray tube creates these conditions. X-rays are produced only when the unit is turned on and
a firm pressure is maintained on the exposure button.
Electric current flows into the x-ray machine and proceeds
either through the step-down transformer or the step-up transformer. The step-down transformer reduces the electric current
from the wall outlet to heat up the filament inside the focusing
cup of the cathode (negative) side of the tube. Thermionic emission results in freed electrons available to make x-rays. The step-up
transformer increases the electric current to impart kinetic energy
to the freed electrons to cause them to propel across the tube to
strike the target (at the focal spot) on the anode (positive) side of
the tube.
The degree to which the filament is heated and, therefore, the
quantity of electrons made available depends on the millamperage
setting. Quantity refers to the number of x-rays in the beam. The
higher the mA, the more electrons available. The penetrating ability or quality of the resultant x-rays is determined by the kilovoltage setting. The higher the kVp, the more penetrating the x-rays.
The beam of radiation that exits the port seal of the tube
head is the primary or useful beam. The polychromatic beam
must be filtered to allow only x-rays with sufficient energy to
reach the oral structures.
The radiographer must be familiar with the operation of
the machine, and the patient must understand the procedure and
provide consent. To achieve consistent results, the radiographer
should follow a systematic and orderly procedure.
RECALL—Study questions
1. Each of the following may be located on the control
panel EXCEPT one. Which one is the EXCEPTION?
a. mA selector
b. kVp selector
c. Focusing cup
d. Line switch
30 HISTORICAL PERSPECTIVE AND RADIATION BASICS
2. Which of the following activates the x-ray production
process?
a. Exposure button
b. Milliamperage
c. Voltmeter
d. Timer selector
3. The x-ray machine component that allows the operator
to position the tube head is called the
a. timer cord.
b. control panel.
c. dead-man switch.
d. extension arm.
4. Fill in the blanks.
a. 30 impulses = _____ second.
b. 45 impulses = _____ second.
c. 1/3 second = _____ impulses.
d. 1/10 second = _____ impulses.
5. To produce a larger quantity of electrons available to
produce x-rays, increase the
a. mA (milliamperage).
b. kVp (kilovoltage).
c. PID (position indicating device).
d. DC (direct current).
6. What term describes the electrical pressure (difference
in potential) between two electrical charges?
a. Amperage
b. Voltage
c. Ionization
d. Incandescence
7. Which term best describes an x-ray beam that is composed of a variety of energy wavelengths?
a. Collimated
b. Short-scale
c. Filtered
d. Polychromatic
8. List the three conditions that must exist for x-rays to be
produced.
a. ______________________
b. ______________________
c. ______________________
9. Draw and label the parts of the dental x-ray tube.
10. The process of heating the cathode wire filament until
red hot and electrons boil off is called
a. autotransformation.
b. self-rectification.
c. thermionic emission.
d. kilovoltage peak.
11. What metal is used for the target in the x-ray tube?
a. Copper
b. Tungsten
c. Aluminum
d. Molybdenum
12. Which of these must be charged negatively during the
time that the x-ray tube is operating to produce x-rays?
a. Radiator
b. Target
c. Anode
d. Cathode
13. Which of these changes the current coming into the
x-ray machine?
a. Transformer
b. Collimator
c. Radiator
d. Rectifier
14. What percent of the kinetic energy inside the x-ray
tube is converted into x-rays?
a. 1%
b. 50%
c. 75%
d. 99%
15. What term describes the opening in the tube housing that
allows the primary beam to exit?
a. Yoke
b. Filament
c. Port
d. Focusing cup
16. Which of the following removes the low-energy, longwavelength energy from the beam?
a. Transformer
b. Collimator
c. Filter
d. Radiator
17. After depressing the exposure button the radiographer
will hear an audible beep sound indicating that the
a. x-rays are being generated.
b. kilovoltage has reached the peak.
c. cathode and anode are reversing polarity.
d. alternating current has been transformed into direct
current.
REFLECT—Case study
To help you understand the practical use of altering exposure variables on a dental x-ray machine, consider the following patients
with these characteristics:
• A 9-year-old female, height 4′ 8” and weight 85 pounds,
who has been assessed for bitewing radiographs to determine the evidence of caries.
CHAPTER 3 • THE DENTAL X-RAY MACHINE: COMPONENTS AND FUNCTIONS 31
• A 21-year-old male college football player, height 6′ 1”,
280 pounds, who has been assessed for periapical radiographs of suspected impacted third molars.
• A 58-year-old female, diagnosed with Bell’s palsy with
slight head and neck tremors, who has been assessed for a
full mouth series for the evaluation of periodontal disease.
1. Would you select an increased or decreased amount of
radiation to produce diagnostic quality radiographic
images for each of these patients?
2. Which of these three exposure variables—milliamperage,
kilovoltage, or time—control(s) the amount of radiation
produced?
3. Which exposure variable would be the best choice to
alter to increase or decrease the amount of radiation
produced for each of these patients?
4. Would you select an increased or decreased penetrating ability of the x-ray beam to produce diagnostic
quality radiographic images for each of these patients?
5. Which of the three exposure variables—milliamperage,
kilovoltage, or time—control(s) the penetrating ability of
the x-ray beam?
6. Which exposure variable would be the best choice to
alter to increase or decrease the penetrating ability of the
x-ray beam?
7. Suppose that you wanted to decrease the amount of time of
the exposure, as may be needed when patient movement is
anticipated (as in the case of patient 3), but still wanted to
produce enough radiation to achieve a diagnostic quality
radiographic image. Which variable—milliamperage or
kilovoltage—would you adjust? Would you increase or
decrease this variable?
Think of other characteristics patients may present with that
would require you to adjust these x-ray machine variables. Keep
in mind that increasing one factor may necessitate decreasing
an opposing factor. Discuss the rationale for your choices.
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual 3rd ed.). Upper Saddle River,
NJ: Pearson Prentice Hall. Chapter 1, “Introduction to Radiation Safety and Dental Radiographic Equipment”
REFERENCES
Bushberg, J. T., Seibert, J. A., Leidholdt, E. M., Jr., & Boone,
J. M. (2001). The essential physics of medical imaging
(2nd ed.). Baltimore: Lippincott Williams & Wilkins.
Carestream Health Inc. (2007). Exposure and processing for
dental film radiography. Rochester, NY: Author.
White, S. C., & Pharoah, M. J. (2008). Oral radiology. Principles and interpretation (6th ed.). St. Louis, MO: Mosby
Elsevier
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Evaluate a radiographic image identifying the basic requirements of acceptability.
3. Differentiate between radiolucent and radiopaque areas on a dental radiograph.
4. Define radiographic density and contrast.
5. List the rules for casting a shadow image.
6. Differentiate between subject contrast and film contrast.
7. List the factors that influence magnification and distortion.
8. List the geometric factors that affect image sharpness.
9. Summarize the factors affecting the radiographic image.
10. Describe how mA, kVp, and exposure time affect image density.
11. Discuss how kVp affects the image contrast.
12. Explain target–surface, object–image receptor, and target–image receptor distances.
13. Demonstrate the practical use of the inverse square law.
KEY WORDS
Contrast
Crystal
Definition
Density
Distortion
Exposure chart
Exposure factors
Exposure time
Extraoral radiography
Film contrast
Focal spot
Geometric factors
Grid
Intensifying screen
Intraoral radiography
Inverse square law
Kilovoltage peak (kVp)
Long-scale contrast
Magnification
Milliampere (mA)
Milliampere/second (mAs)
Motion
Object–image receptor distance
Penumbra
Position indicating device (PID)
Radiographic contrast
Radiolucent
Radiopaque
Producing Quality
Radiographs
CHAPTER
OUTLINE
 Objectives 32
 Key Words 32
 Introduction 33
 Terminology 33
 Shadow Casting 34
 Factors Affecting
the Radiographic
Image 35
 Effects of Varying
the Exposure
Factors 39
 Effects of
Variations in
Distances 41
 Inverse Square
Law 42
 Exposure Charts 44
 Review, Recall,
Reflect, Relate 44
 References 46
CHAPTER
4
CHAPTER 4 • PRODUCING QUALITY RADIOGRAPHS 33
Introduction
Each patient presents with a unique set of characteristics for
which a customized approach to exposure settings is needed. The
dental radiographer has an ethical responsibility to produce the
highest diagnostic quality radiographs for patients who agreed to
be exposed to ionizing radiation. To consistently produce diagnostic quality radiographs at the lowest possible radiation dose,
the dental radiographer needs to understand the interrelationships of the components of the dental x-ray machine.
There are three basic requirements for an acceptable diagnostic radiograph (Figure 4-1).
1. All parts of the structures recorded must be imaged as close
to their natural shapes and sizes as the patient’s oral
anatomy will permit. Distortion and superimposition of
structures should be kept to a minimum.
2. The area examined must be imaged completely, with enough
surrounding tissue to distinguish between the structures.
3. The radiograph should be free of errors and show proper
density, contrast, and definition.
The quality of a radiograph depends on both the physical
factors and the subjective opinion of the individual who reads it.
The purpose of this chapter is to describe the physical attributes
of a quality radiographic image and to study the factors that
affect these attributes.
Terminology
The following terms should be used when describing radiographic images: radiolucent, radiopaque, density, contrast, and
sharpness.
When a film-based dental radiograph is viewed on a light
source and digital images are viewed on a computer monitor, the
image appears black and white, with various shades of gray in
between. The terms used to describe the black and white areas
are radiolucent and radiopaque, respectively.
Radiolucent
Radiolucent refers to that portion of the image that is dark or
black (Figure 4-1). Structures that appear radiolucent permit
the passage of x-rays with little or no resistance. Soft tissues
and air spaces are examples of structures that appear
radiolucent on a radiograph.
Radiopaque
Radiopaque refers to that portion of the image that is light or
white (Figure 4-1). Structures that appear radiopaque are dense
and absorb or resist the passage of x-rays. Enamel, dentin, and
bone are examples of structures that appear radiopaque on the
radiograph.
Radiolucent and radiopaque are relative terms. For instance,
even though both enamel and dentin are radiopaque, enamel is
more radiopaque (appears lighter) than dentin.
Three visual image characteristics that directly influence
the quality of the radiographic image are density, contrast, and
sharpness.
Density
Density is the degree of darkness or image blackening
(Figure 4-2). A radiographic image that appears light is said to
have little density. A radiographic image that appears dark is said
to be more dense. The blackness results when x-rays strike sensitive crystals in the film emulsion, and subsequent processing
causes the crystals to darken. When using a digital sensor, sensitive pixels capture the radiation, and “processing” by computer
software produces darker pixels. The degree of darkening of the
radiograph is increased when the milliamperage or the exposure
time is increased and more x-rays are produced to reach the
film emulsion or digital sensor.
Radiographs need just the right amount of density to be
viewed properly. If the density is too light or too dark, the images
FIGURE 4-1 An acceptable diagnostic radiograph.
Sharpness
Short-scale contrast
Subject contrast
Target–image receptor distance
Target–object distance
Target–surface distance
A B
FIGURE 4-2 Radiographic density. Radiograph (A) is
underexposed and appears too light (less dense). Radiograph (B) is
overexposed and appears too dark (more dense).
KEY WORDS
34 HISTORICAL PERSPECTIVE AND RADIATION BASICS
of the teeth and supporting tissues cannot be visually separated
from each other. The ideal radiograph has the proper amount of
density for the interpreter to view black areas (radiolucent),
white areas (radiopaque), and gray areas.
Contrast
Contrast refers to the many shades of gray that separate the
dark and light areas (Figure 4-3). An image with good contrast
will contain black, white, and enough shades of gray to differentiate between structures and their conditions. A radiograph
that shows just a few shades is said to have short-scale or high
contrast, whereas one that shows many variations in shade is said
to possess long-scale or low contrast.
The term short-scale contrast (also called high contrast;
Figure 4-4) describes a radiograph in which the density differences between adjacent areas are large. The contrast is high
because there are fewer shades of gray and more black against
white. The gray tones indicate the differences in absorption of
the x-ray photons by the various tissues of the oral cavity or the
head and neck region. The radiograph is radiolucent (dark)
where the tissues are soft or thin and radiopaque (white) where
the tissues are hard or thick. Such radiographs result when low
(60–70) kVp is applied.
The term long-scale contrast (also called low contrast;
Figure 4-4) describes a radiograph in which the density differences between adjacent areas are small. The contrast is low and
very gradual because there are many shades of gray. Such radiographs result when high (80–100) kVp is applied.
Sharpness
Sharpness/definition is a geometric factor that refers to the
detail and clarity of the outline of the structures shown on the
radiograph. Unsharpness is generally caused by movement of
the patient, image receptor, or tube head during exposure.
Digital imaging sharpness can be affected by pixel size and
distribution and will be discussed in Chapter 9.
Shadow Casting
A radiograph is a two-dimensional image of three-dimensional
objects. Therefore, it is necessary to apply the rules for creating a
shadow image to produce a quality radiographic image. The following rules for casting a shadow image will help to reproduce
the size and shape of the objects of the oral cavity accurately.
Rules for Casting a Shadow Image
1. Small focal spot: to reduce the size of the penumbra
(partial shadow around the objects of interest) resulting in
a sharper image and slightly less magnification
2. Long target-object distance: to reduce the penumbra and
magnification
3. Short object-image receptor distance: to reduce penumbra
and magnification
4. Parallel relationship between object and image receptor: to
prevent distortion of the image
5. Perpendicular relationship between the central ray of the
x-ray beam and both the object and the image receptor: to
prevent distortion of the image
Because x-rays belong to the same electromagnetic spectrum as
light (see Chapter 2), these two energies share many of the
same characteristics. Therefore, when considering the application of shadow cast rules, it is helpful to compare the shadows
cast by light with the shadows that x-rays will cast of the structures of the oral cavity. For example, if you were outside during
the morning hours when the sun was low on the horizon, the
60 kvp
Short scale contrast
100 kvp
Long scale contrast
FIGURE 4-3 Penetrometer tests demonstrate radiographically that
a longer contrast scale results from the use of 100-kilovolt exposures.
Dental radiographs exposed at 100 kVp have long-scale contrast.
Radiographs exposed at 60 kVp have short-scale contrast. (Courtesy of
General Electric Company, Medical Systems Division)
A B
FIGURE 4-4 Radiographic contrast. Radiograph
(A), exposed at 60 kVp, has high contrast. Radiograph
(B), exposed at 90 kVp, has low contrast.
CHAPTER 4 • PRODUCING QUALITY RADIOGRAPHS 35
sun’s rays would be directed at your body at a low angle, casting a shadow that was elongated, or longer than your actual
height. If you were outside at midday, when the sun was directly
overhead, the sun’s rays would be directed at your body at a
steep angle, casting a shadow that was foreshortened, or
shorter than your actual height. At some time during the day,
the sun’s light would be cast at the precise angle to your body
that your shadow on the ground would be at the same length as
your actual height. Directing a flashlight at an object, such as
the child’s game of producing hand puppet shadows, is another
example of shadow casting. Depending on the direction of the
flashlight beam alignment and the distance the light must travel
to reach the object, accurate or distorted shadow images result.
Shadow cast rules are often referred to as the geometric
factors that contribute to the quality of the radiographic image.
Geometric factors are those factors that relate to the relationships of angles, lines, points, or surfaces. Each of the shadow
cast rules will be discussed in detail as to its role in producing
quality radiographic images.
Radiographic Contrast
Radiographic contrast defined as the visible difference
between densities depends on the following variables.
1. Subject (types of tissues being imaged). The subject contrast is the result of differences in absorption of the x-rays
by the tissues under examination. The subject to be imaged
must have contrast. A radiograph of a 1-inch-thick sheet of
plastic would show no contrast because the plastic is of
uniform thickness and composition. Patients have contrast
because human tissues vary in size, thickness, and density.
2. Kilovoltage peak (kVp). There is an inverse relationship
between kVp and contrast (Figure 4-4). In relative terms,
higher kilovoltages produce lower contrast. The blacks are
grayer, the whites are grayer, and there are many shades (or
steps) of gray in between. Lower kilovoltages produce higher
contrast. The blacks are blacker, the whites are whiter, and
there are fewer shades (or steps) of gray in between.
3. Scatter radiation. In Chapter 2 we learned that Compton
scattering occurs whenever dental x-rays interact with matter such as the tissues of the patient’s head. These scattered
x-rays add a uniform exposure to the radiograph, thereby
decreasing the contrast. For intraoral radiography (inside
the mouth), a collimator (lead diaphragm) is used to keep
the beam size as small as possible to help reduce scatter
radiation. For extraoral radiography (outside the mouth),
grids are sometimes used to absorb scattered x-rays. A grid
is a mechanical device composed of thin strips of lead
alternating with a radiolucent material (plastic). The grid is
placed between the patient and the image receptor to
absorb scattered x-rays (see Figure 29-10).
4. Film/digital sensor type. Each film has its own inherent
(built-in) contrast that may vary by manufacturer. Digital
sensor pixel size and the effects on the image contrast and
density will be discussed in detail in Chapter 9.
5. Exposure. An underexposed or an overexposed radiograph
will result in diminished or poor contrast. Accidental exposure of the film to stray radiation or other conditions such as
heat and humidity will create film fog (Chapter 18). Fog is
the formation of a thin, cloudy layer that reduces the image
contrast. A radiograph that is too light, too dark, or fogged
will not have significantly different shades of gray to provide optimal contrast.
6. Processing. Maximum film contrast can only be obtained
through meticulous film processing procedures (Chapter
8). If improper development time or temperature is used,
the radiograph will not have the ideal contrast the manufacturer built into it.
Sharpness/Definition
Sharpness, also known as definition, refers to the clarity of the
outline of the structures on the radiograph. Radiographic image
sharpness depends on the following variables (see Table 4-2).
1. Focal spot size. As explained in Chapter 3, the focal spot is
the small area on the target where bombarding electrons are
Factors Affecting the
Radiographic Image
The dental radiographer must have a working knowledge of the
factors that affect the radiographic image. Although density is
important for producing the detail and visibility of a radiograph, it is the radiographic contrast and sharpness/definition
that interpretation and diagnosis of oral conditions depend on
(Table 4-1).
PRACTICE POINT
Some clinicians prefer the short-scale contrast radiographs
that result from a low kVp setting to diagnose caries and
long-scale contrast radiographs that result from a high kVp
setting to diagnose periodontal disease. In theory, shortscale contrast images should be better at showing a radiolucency (depicting evidence of decalcification indicating
caries) against radiopaque tooth enamel, whereas longscale contrast radiographs are purported to be better at
showing subtle changes (gray areas) indicating alveolar
bone changes. However, research indicates that both shortand long-scale contrast images perform equally well in
providing the clinician with the necessary information for
interpretation and diagnosis. The ideal level of contrast is
often a matter of individual preference.
36 HISTORICAL PERSPECTIVE AND RADIATION BASICS
TABLE 4-1 Summary of Factors Influencing Radiographic Image Contrast
FACTORS VARIABLES IMAGE CONTRAST
Subject thickness (different
tissues of the body)
Region with tissues of different densities
(enamel, dentin, pulp of the tooth)
Higher contrast between these
different tissues
Region with tissues of similar densities
(supporting alveolar bone)
Lower contrast between the
different areas of bone
kVp (kilovoltage peak) High kVp Lower contrast
Low kVp Higher contrast
Scatter radiation Increased scatter radiation (large beam diameter
used for intraoral radiographs/no grid used for
extraoral radiographs)
Lower contrast
.
Decreased scatter radiation (beam diameter
narrowed with collimation for intraoral
radiographs/grid used for extraoral radiographs)
Higher contrast
Image receptor type Different manufacturers Higher or lower contrast is inherent
and depends on the manufacturer
Exposure Under- or overexposure and film fog Each will lower contrast
Processing Accurate time-temperature processing followed
Inaccurate time-temperature processing followed
Adequate contrast
Lower or poor contrast
perfectly still during the exposure. Even slight vibration of
the tube head increases the size of the focal spot (Figure 4-7).
2. Target–image receptor distance. The target–image receptor distance is the distance between the source of x-ray production (which is at the target on the anode inside the tube
head) and the image receptor. PIDs are used to establish the
target–image receptor distance. PIDs are classified as being
short or long and come in standard lengths of 8 inches
(20.5 cm), 12 inches (30 cm), and 16 inches (41 cm) for
converted into x-rays. The smaller the focal spot area, the
sharper the image appears (Figure 4-5). A large focal spot
creates more penumbra (partial shadows) and therefore loss
of image sharpness (Figure 4-6). Ideally, the focal spot
should be a point source, then no penumbra would be present.
However, a single point source would create extreme heat
and burn out the x-ray tube. Focal spot size is determined by the manufacturer of the x-ray machine. To ensure
that the focal spot remains small, the tube head must remain
TABLE 4-2 Summary of Factors Influencing Radiographic Image Sharpness
FACTORS VARIABLES IMAGE SHARPNESS
Focal spot size Small focal spot Increase sharpness
Large focal spot Decrease sharpness
Target–image receptor distance Long target–image receptor distance Increase sharpness
Short target–image receptor distance Decrease sharpness
Object–image receptor distance Short object–image receptor distance Increase sharpness
Long object–image receptor distance Decrease sharpness
Motion No movement Sharp image
Movement Fuzzy image
Screen thickness Thin screen Increase sharpness
Thick screen Decrease sharpness
Screen–film contact Close contact Increase sharpness
Poor contact Decrease sharpness
Film crystal/pixel size Small crystals/pixels Increase sharpness
Large crystals/pixels Decrease sharpness
CHAPTER 4 • PRODUCING QUALITY RADIOGRAPHS 37
intraoral projections. The shorter the target–image receptor
distance, the more divergent the x-ray beam (Figure 4-8). A
long target–image receptor distance has x-rays in the center
of the beam that are nearly parallel. Therefore, the image on
the radiograph will be sharper. Also a longer target–image
receptor distance will result in less image magnification
(explained later in this chapter).
3. Object–image receptor distance. The object–image receptor distance is the distance between the object being radiographed (the teeth) and the dental x-ray image receptor
(film or digital sensor.) The image receptor should always be
placed as close to the teeth as possible. The closer the proximity of the image receptor to the teeth, the sharper the image
and the less magnification (image enlargement). The image
will become fuzzy (more penumbra) and magnified as the
object–image receptor distance is increased (Figure 4-6).
4. Motion. Movement of the patient and/or the image receptor in addition to the tube head results in a loss of image
sharpness (Figure 4-9).
5. Screen thickness. Intensifying screens (often referred to as
screens), used in extraoral radiography, are made of crystals
that emit light when struck by x-rays. The light, in turn,
exposes the film and helps to produce the image. Intensifying screens require less radiation to produce a radiographic
image than direct exposure film, resulting in less radiation
exposure to the patient. However, the use of intensifying
screens decreases the sharpness of the radiographic image
(Figure 4-10). The thicker the screen, the less radiation
required to expose the film. However, these thicker screens
produce a less sharp radiographic image. Generally, the
radiographer should use the highest speed screen and film
combination, determined by the thickness of the phosphor
FIGURE 4-5 Using a small focal spot on the target,
a long target–image receptor distance, and a short object–image
receptor distance will result in a sharp image.
Target
Object
Image receptor
Anode
Target
Object
Image receptor
Anode
FIGURE 4-6 Large focal spot on the target and long object–image
receptor distance results in more penumbra and loss of image
sharpness.
Anode Target
FIGURE 4-7 Movement of the tube head. Motion, even slight,
of the tube head will effectively create a larger surface area of the
focal spot, resulting in penumbra.
Target
Object
Image receptor
Anode
FIGURE 4-8 Large focal spot on the target and short target–image
receptor distance results in more penumbra and loss of image sharpness.
38 HISTORICAL PERSPECTIVE AND RADIATION BASICS
to avoid loss of image sharpness and yet maintain the maximum reduction in radiation exposure. Dental x-ray film is
explained in detail in Chapter 7.
Digital sensors (Chapter 9) use pixels (short for picture
element) that capture discrete units of information that the
computer then combines into a radiographic image. The
smaller the pixel size, the sharper the resultant image.
Magnification/Enlargement
Magnification or enlargement is the increase in size of the
image on the radiograph compared to the actual size of the
object. In Chapter 3, we learned that x-rays travel in diverging
straight lines as they radiate from the focal spot of the target.
Because of these diverging x-rays, there is some magnification present in every radiograph.
Magnification is mostly influenced by the target–object
distance and the object–image receptor distance. The target–object distance is determined by the length of the PID.
When a long PID is used, the x-rays in the center of the
beam are more parallel, resulting in less image magnification (Figure 4-11). The object–image receptor distance
should be kept to a minimum. Always place the film/sensor
as close to the teeth as possible, while maintaining a parallel
relationship between the long axes of the teeth and the plane
of the image receptor, to decrease magnification.
Increasing the target–object distance and decreasing
the object–image receptor distance will minimize image
FIGURE 4-9 Blurry, unsharp image caused by movement of the
patient, the image receptor, or the tube head.
Film Film
Protective coat
Active phosphor layer
Reflecting layer
Base
Screen
X-ray
A
X-ray
B
FIGURE 4-10 Screen thickness. X-ray A strikes a
crystal far from the film and the divergent light exposes a
wide area of the film, resulting in unsharpness. X-ray B
strikes a crystal close to the film, resulting in less
divergence of the light that exposes the film and therefore
a sharper image. The thicker the screen, the less sharp the
image.
PRACTICE POINT
The tube head must remain perfectly still during exposure.
Even slight vibration of the tube head increases the size of
the focal spot, which in turn produces an unsharp image.
layer, that is consistent with good diagnostic results. Intensifying screens are explained in detail in Chapter 29.
6. Screen–film contact. The film should be in close physical
contact with the intensifying screen. Poor screen–film contact results in the wider spread of light and fuzziness
(penumbra) of the image. Intensifying screens should be
examined periodically for proper functioning. Additionally, only one film should be placed in contact with the
screen. Attempting to make a duplicate image by placing
two films into one cassette is not acceptable practice unless
using a film type made especially for this purpose.
7. Crystal/pixel size of intraoral image receptors. X-ray
film emulsion contains crystals that are struck by x-rays
when exposed and in turn will produce the radiographic
image. Image sharpness is influenced by the size of these
crystals. Similar to the crystal size of intensifying screens,
the smaller the size of the crystals within the film emulsion, the sharper the radiographic image. However, small
crystal size contributes to a slow speed film, requiring the
patient to receive a larger dose of radiation. Film manufacturers strive to produce film with the smallest sized crystals
CHAPTER 4 • PRODUCING QUALITY RADIOGRAPHS 39
magnification. Note that these two shadow cast rules for
reducing magnification also increase image sharpness.
Distortion
Distortion is the result of unequal magnification of different
parts of the same object. Distortion results when the image
receptor is not parallel to the object (Figure 4-13) and/or
when the central ray of the x-ray beam is not perpendicular to
the object and the plane of the image receptor (Figure 4-14).
To minimize image distortion, the two shadow cast rules for
placement of the image receptor and x-ray beam positioning
Object
Image receptor
Image
Target Target
8″ (20.5 cm)
16″ (41 cm)
FIGURE 4-11 Magnification. Comparison of
8-in. (20.5-cm) and 16-in. (41-cm) target-object and
target–image receptor distances. The image is
magnified (enlarged) when these distances are
shortened.
PRACTICE POINT
When positioning the PID for intraoral exposures, it is important to place the open end of the PID as close as possible to (without
touching) the skin surface of the patient’s face. Image quality is improved when the target–surface distance is increased. However,
it is important to note that increasing the distance between the target and the skin surface of the patient is determined by the
length of the PID and not by positioning the PID a greater distance away from the patient (Figure 4-12). Positioning the open end
of the PID away from the skin surface of the patient’s face will result in a larger diameter of radiation exposure and an underexposed image.
must be followed. Rules 4 and 5 state that the plane of the
image receptor must be positioned parallel to the long axes of
the teeth, and the central ray of the x-ray beam must be
aligned perpendicular to both the image receptor and the
teeth.
Effects of Varying the Exposure Factors
Density and contrast have a tremendous influence on the diagnostic quality of the radiograph. The x-ray machine exposure
settings can affect both density and contrast (Table 4-3).
FIGURE 4-12 Correct and incorrect PID positioning. Left image illustrates the correct position of
the open end of the PID as close to the patient’s skin as possible. Right image illustrates an incorrect position
of the PID. This PID position will result in a greater beam diameter of exposure to the patient and will
produce an underexposed image.
40 HISTORICAL PERSPECTIVE AND RADIATION BASICS
Variations in Exposure Time
Exposure time is the interval that the x-ray machine is fully
activated and x-rays are produced. The principal effect of
changes in exposure time is on the density of the radiograph.
Increasing the exposure time darkens the radiograph, whereas
decreasing exposure time lightens it. Opinions differ on optimum density and contrast because visual perception varies from
person to person; some practitioners may prefer lighter radiographs, wherease others may prefer darker radiographs. Of the
three controls, exposure time is easiest to change. In fact, many
x-ray machines today have preset fixed milliamperage and
kilovoltage, so that time is the only exposure factor that can be
changed by the operator.
The milliamperage, exposure time, and kilovoltage are
known as the exposure, control, or radiation factors. Whenever
one of the exposure factors is altered, one or a combination of
the other factors must be altered proportionally to maintain
radiographic density. For example, exposure time will need to be
decreased when milliamperage or kilovoltage is increased to
maintain optimal image density.
Variations in Milliamperage (mA)
The amount of electric current used in the x-ray machine is
expressed in milliamperes (mA). The mA selected by the operator, or preset by the unit manufacturer, determines the quantity
or number of x-rays that are generated within the tube. The density of the radiograph is affected whenever the milliamperage is
changed. Increasing the mA increases (darkens) the density of
the radiograph, whereas decreasing the mA decreases (lightens) the density of the radiograph.
Target
Object
Image receptor
Anode
FIGURE 4-13 Object and image receptor are not parallel,
resulting in distortion.
Target
Object B
Image receptor
Object A
Anode
FIGURE 4-14 Central ray of x-ray beam is not perpendicular
to the objects and image receptor, resulting in distortion and overlapping of object A and object B. Note that object A is magnified
larger than object B because object A is a greater distance from the
image receptor than object B.
TABLE 4-3 Effect of Varying Exposure Factors on Image Density
EXPOSURE ADJUSTMENTa IMAGE DENSITY
Increase mA Darker
Decrease mA Lighter
Increase time Darker
Decrease time Lighter
Increase kVp Darkerb
Decrease kVp Lighterb
When any exposure factor is increased, or decreased, one or more of the other exposure factors must be
adjusted to maintain optimum image density.
Varying kVp primarily affects the image contrast, but it will also (secondarily) affect the image density.
Increase kVp for less contrast and decrease kVp for more contrast.
b
a
CHAPTER 4 • PRODUCING QUALITY RADIOGRAPHS 41
Milliampere/seconds (mAs)
Because both milliamperage and exposure time are used to regulate the number of x-rays generated and have the same effect on
radiographic density, they are often combined into a common factor called milliampere/seconds (mAs). Combining the milliamperage with the exposure time is an effective way to
determine the total radiation generated.
A simple formula for determining this total is: mA multiplied by the exposure time (in seconds or impulses) equals
mAs.
PROBLEM. Consider a practical problem using this formula.
Assume the following exposure factors are in use: 10 mA, 0.6
sec, 90 kVp, and 12-in. (30-cm) target–image receptor distance.
If the mA is increased to 15, but the kVp and target–image
receptor distance remain constant, what should the new exposure time be to maintain image density?
SOLUTION. The only exposure factor that was changed is the
mA, which was increased from 10 mA to 15 mA. We need to
compensate for the increase in mA by decreasing the exposure
time.
ANSWER. The new exposure time is 0.4 sec.
When the mA is increased, the exposure time must be
decreased to produce identical radiographic image density
between the first and second radiographs. A practical use for
applying this formula would be when patient movement is
anticipated—in this case, increasing the amount of radiation
produced, so that the duration of exposure could be shortened.
Variations in Kilovoltage (kVp)
The quality of the radiation (wavelength or energy of the x-ray
photons) generated by the x-ray machine is determined by the
kilovoltage peak (kVp). The more the kVp is increased, the
shorter the wavelength and the higher the energy and penetrating
power of the x-rays produced. Kilovoltage is the only exposure
factor that directly influences the contrast of a dental radiograph.
However, increasing the kVp will also increase the number
(quantity) of x-rays produced and therefore, increase the density
of the radiograph. As the kVp of the x-ray beam is increased for
the purpose of producing a lower contrast image, the density of
the radiograph is held constant by reducing the milliampere-seconds (mAs) or exposure time. Because the exposure time is usually the easiest exposure factor to change, the following rule
applies: When increasing the kVp by 15, for example from 70
kVp to 85 kVp, decrease the exposure time by dividing by 2;
when decreasing the kVp by 15, increase the exposure time by
multiplying by 2. One exposure factor balances the other to produce a radiographic image of acceptable density.
? sec. = 0.4 sec
? sec. = 6 mAs
15 mAs
15 mA * ? sec. = 6 mAs
10 mA * 0.6 sec. = 6 mAs
mA * s = mAs
mA * s = mAs
Effects of Variations in Distances
The operator must take into account several distances to produce the ideal diagnostic quality image:
• The distance between the x-ray source (at the focal spot on
the target) and the surface of the patient’s skin
• The distance between the object to be x-rayed (usually
the teeth) and the image receptor
• The distance between the x-ray source and the recording
plane of the image receptor
Various terms are used to describe these distances. The
terms target–surface (skin), anode–surface, tube–surface, and
source–surface are synonymous, as are target–image receptor,
anode–image receptor, and source–image receptor. In this text,
the terms target–surface distance, object–image receptor distance,
target–object distance, and target–image receptor distance are
used (Figure 4-15).
Target–Surface Distance
Generally, whenever the image receptor is positioned intraorally, the length of the target–surface distance depends on the
length of the position indicating device (PID) used. All intraoral techniques require the open end of the PID be positioned to
almost touch the patient’s skin to standardize the distance used
and the image density.
Object–Image Receptor Distance
The object–image receptor distance depends largely on the
method that is employed to hold the receptor in position next to
the teeth. When the bisecting technique is used (see Chapter 15),
the image receptor is pressed against the palatal or lingual tissues
as close as the oral anatomy will permit. This results in the
object–image receptor distance being shorter in the area of the
crown where the tooth and image receptor touch than in the area
of the root, where the thickness of the bone and gingiva may
cause a divergence between the long axis of the tooth and the
image receptor (Figure 4-16). The least divergence occurs in the
mandibular molar areas. The greatest divergence is in the maxillary anterior areas, where the palatal structures may curve sharply.
With the paralleling technique, most image receptor holders
are designed so that the receptor is held parallel to the long axis
of the tooth of interest. This necessitates positioning the receptor
sufficiently into the middle of the oral cavity, away from the
teeth, to avoid impinging on the supporting bone and gingival
structures. This technique results in object–image receptor distances that are often more than 1 in. (25 mm). The paralleling
technique compensates for this increased object–image receptor
distance by recommending an increase in the target–image
receptor distance (use a longer PID) to help offset the distortion,
explained next.
Target–Image Receptor Distance
The target–image receptor distance is the sum of the
target–object and the object–image receptor distance (Figure
4-15). The quality of the radiographic image improves whenever
the target–image receptor distance is increased. Magnification
42 HISTORICAL PERSPECTIVE AND RADIATION BASICS
Inverse Square Law
The x-ray photons, traveling in straight lines, spread out (diverge)
as they radiate away from the source (target). It follows that the
intensity of the beam is reduced as this occurs (Figure 4-17). How
much the beam intensity decreases is based on the inverse square
law, which states that the intensity of radiation varies inversely as
the square of the distance from its source.
is reduced, and sharpness of detail (definition) is increased.
Increasing the target-image receptor distance reduces the fuzzy
outline (penumbra) that is seen around the radiographic
images. Therefore, positioning the image receptor far enough
from the teeth to enable it to be held parallel and using a long
12-in. (30-cm) or 16-in. (41-cm) PID will increase the quality
of the image definition. These techniques are described in
detail in Chapter 13.
The location of the x-ray tube within the tube housing can
affect the target–image receptor distance. In the conventional
dental x-ray machine, the target (located on the anode within
the tube) is situated in the tube head in front of the transformers. The attached PID length can be visibly determined. When
the tube is recessed within the tube head, located behind the
transformers, enough space is gained within the tube head so
that a long target–image receptor distance is achieved even
though a short PID is in place (see Figure 3-1).
Target Radiation
beam
Target-surface distance
Target-object distance
Target-image receptor distance
ObjectImage
receptor distance
Skin surface
covering
cheek
Object
tooth Image receptor
Central ray
FIGURE 4-15 Distances. Relationship among target, skin surface, object (tooth), and image receptor
distance.
FIGURE 4-16 Object–image receptor distance. This placement of
the image receptor places the crown of the tooth closer to the receptor
than the root.
Image
receptor
Object tooth
Skin surface
covering cheek
Anode
D
2D
D
2D
FIGURE 4-17 Inverse square law. Relationship of distance (D)
to the area covered by x-rays emitted from the x-ray tube. X-rays
emerging from the tube travel in straight lines and diverge from each
other. The areas covered by the x-rays at any two points are
proportional to each other as the square of the distances measured
from the source of radiation.
CHAPTER 4 • PRODUCING QUALITY RADIOGRAPHS 43
The inverse square law may be written as:
where:
is the original intensity
is the new intensity
is the original distance
is the new distance
The inverse square law is applied when considering the distance between the source of radiation and the image receptor,
as in the length of the PID, and when considering the distance
between the source of radiation and the operator, as in where
the operator stands to maintain radiation protection during
exposure. The distance between the source of radiation and the
image receptor will have an affect on the image quality. When
changing the PID length, a corresponding change must occur in
the exposure time to maintain image density. It is important to
understand that the intensity of the radiation decreases by the
square of the distance increased.
Consider the following problem where distance is considered as a means of operator protection.
PROBLEM. A dental radiographer stands 3 feet (0.9 m) from
the source of radiation where the measured intensity is 100 milliroentgens (mR) per minute. The radiographer then moves to a
new location 6 ft (1.8 m) from the source of radiation. What is
the radiation intensity at the new location?
SOLUTION.
Find
ANSWER. The intensity at the new location is
25 mR/min.
In this case, the radiographer’s new location is a safer place
to stand during exposure because this new location at 6 ft away
from the source of radiation receives only one-fourth the exposure of the old location at 3 ft away for the source of radiation.
Consider the following problem where distance is considered when changing the length of the PID.
I2 = 25 mR per minute
¢ 1
4
≤ 100
I2
= 4
1 ¢ 1
4
≤
100
I2
= 4
1
100
I2
= 22
12
100
I1
= 62
32
I2.
D2 = 6 ft
D1 = 3 ft
I1 = 100 mR/min
D2
D1
I2
I1
I1
I2
= 1D222
1D122
PROBLEM. A quality dental radiograph is obtained using an
8-in. (20.5-cm) PID and an exposure time of 3 impulses. The 8-
in. (20.5-cm) PID is removed from the tube head and replaced
with a 16-in. (41 cm) PID. What should the new exposure time
be to maintain image density of radiographs exposed at this
new target–image receptor distance?
We know that the radiation intensity at a distance of 16
inches (41 cm) will be less than the intensity at the old distance
of 8 inches (20.5-cm). Applying the inverse square law formula
we would see that the intensity of the radiation will have
decreased by the square of the distance, producing a radiographic image that would be less dense (lighter) than the original radiograph produced using an 8-in. (20.5-cm) PID. To
produce a radiograph of equal density using a 16-in. (41-cm)
PID, use the following modification of the inverse square law
formula to determine the new exposure setting:
where:
is the original exposure time (in impulses)
is the new exposure time (in impulses)
is the original distance
is the new distance
SOLUTION.
Find
ANSWER. The impulse setting required to maintain image
density at the new 16-in. (41-cm) source-to-image receptor
distance is 12 impulses.
Because the x-rays emerging from the tube travel in
straight lines and diverge from one another, it follows that the
intensity of the beam is reduced unless a corresponding
increase is made in one or a combination of the target–image
receptor distance exposure factors. Such changes in exposure
factors are essential to maintaining optimum image density.
Usually time is the easiest exposure factor to change. This formula is useful for obtaining the appropriate exposure time
when only the target–image receptor distance is altered.
I2 = 12 impulses
1423
I2
= 1142
4
3
I2
= 1
4
3
I2
= 12
22
3
I2
= 82
162
I2.
D2 = 16 inches
D1 = 8 inches
I1 = 3 impulses
D2
D1
I2
I1
I1
I2
= 1D122
1D222
44 HISTORICAL PERSPECTIVE AND RADIATION BASICS
exposure time and milliamperage is where
the mA is multiplied by the exposure time to determine the
millimaperage seconds. The formula for altering kilovoltage
is if increasing the kVp by 15, decrease the exposure time by
dividing by 2; if decreasing the kVp by 15, increase the exposure time by multiplying by 2.
When changing the PID length, the inverse square law is
used to adjust the exposure time to produce identical radiographic image density. This inverse square law states that the
intensity of radiation varies inversely as the square of the distance from its source. The inverse square law formula is
RECALL—Study questions
1. List the three criteria for acceptable radiographs.
a. ______________
b. ______________
c. ______________
2. Dense objects appear radiolucent because dense objects
absorb the passage of x-rays.
a. Both the statement and reason are correct and
related.
b. Both the statement and reason are correct but NOT
related.
c. The statement is correct, but the reason is NOT.
d. The statement is NOT correct, but the reason is
correct.
e. NEITHER the statement NOR the reason is correct.
3. The degree of darkening of the radiographic image is
referred to as
a. contrast.
b. definition.
c. density.
d. penumbra.
4. Which of the following describes the radiographic
image produced with a kVp exposure setting of 100?
a. Short scale
b. Long scale
c. High contrast
d. Low density
5. Image contrast is NOT affected by
a. processing procedures.
b. type of film.
c. scatter radiation.
d. milliamperage.
6. What factor has the greatest effect on image sharpness?
a. Movement
b. Filtration
c. Kilovoltage
d. Amperage
I1
I2
= 1D122
1D222
Exposure Charts mA * s = mAs,
Operators may memorize exposure factors needed for a particular technique; however, safety protocol dictates that exposure
charts, available commercially or custom made by the practice,
be posted at the x-ray unit control panel for easy reference. In
fact, in some locations regulations require that exposure charts
be posted. These charts show at a glance how much exposure
time is required for a film of any given speed or a digital sensor
when used with all possible combinations of exposure time,
milliamperage, and peak kilovoltage.
Some dental x-ray machine manufacturers have incorporated
the commonly used exposure factors into the dial of the control
panel. With these units, the operator only has to set the pointer to
the desired region to be examined, and the unit automatically sets
the required exposure factors.
REVIEW—Chapter summary
An acceptable diagnostic radiograph must show the areas of
interest—the designated teeth and surrounding bone structures—completely and with minimum distortion and maximum sharpness. When evaluating a radiographic image, the
oral health care professional should utilize appropriate scientific terminology such as density, contrast, sharpness, magnification, and distortion. The term radiolucent refers to the
dark or black portion of the image, whereas the term
radiopaque refers to the light or white portion of the image.
High-contrast images, those with black and white and few
shades of gray, are called short-scale, whereas low-contrast
images, those with grayer whites and grayer blacks with
many shades of gray, are called long-scale.
The detail and visibility of a radiograph depends on two
factors—radiographic contrast and sharpness/definition.
Radiographic contrast depends on: the subject (types of tissues
being imaged), kilovoltage peak (kVp) setting, scatter radiation, film/digital sensor type, exposure, and processing. Sharpness is determined by the geometric factors: focal spot size,
target–image receptor distance, object–image receptor distance, motion, screen thickness, and screen–film contact, and by
the crystal/pixel size of the image receptor.
To create a sharp image, the radiographer must follow the
rules for casting a shadow image: small focal spot, long
target–image receptor distance, short object–image receptor
distance, parallel relationship between object and image receptor, and perpendicular relationship between central ray of the xray beam and the object and image receptor. Image
magnification and loss of sharpness is further reduced by limiting movement of the tube head and PID, the patient, and the
image receptor during exposure.
Although not all dental x-ray units allow the operator to
manually alter all exposure factors, when available, the radiographer should take advantage of the ability to vary the
exposure factors to produce radiographs that have the desired
image qualities. When altering one exposure factor, a corresponding change must be made to another factor to produce
identical radiographic image density. The formula for altering
CHAPTER 4 • PRODUCING QUALITY RADIOGRAPHS 45
7. As crystals in the film emulsion increase in size, the
radiographic image sharpness increases because the
amount of radiation needed to expose the film at an
acceptable density decreases.
a. Both the statement and reason are correct and
related.
b. Both the statement and reason are correct but NOT
related.
c. The statement is correct, but the reason is NOT.
d. The statement is NOT correct, but the reason is correct.
e. NEITHER the statement NOR the reason is correct.
8. What term best describes a fuzzy shadow around the
outline of the radiographic image?
a. Magnification
b. Distortion
c. Detail
d. Penumbra
9. Distortion results when
a. object and image receptor are not parallel.
b. x-ray beam is perpendicular to the object and image
receptor.
c. using a short object–image receptor distance.
d. using a small focal spot.
10. The dental radiograph will appear less dense (lighter) if
one increases the
a. mA.
b. kVp.
c. exposure time.
d. target–image receptor distance.
11. The exposure factors used at an oral health care facility
are: 10 mA, 0.9 sec, 70 kVp, and 16-in. (41-cm)
target–image receptor distance. The radiographer
increases the mA to 15, but leaves the kVp and
target–image receptor distance constant. To maintain
identical image density, what should the new exposure
time be?
a. 0.3
b. 0.6
c. 1.2
d. 1.8
12. Which of the following is appropriate to increase radiographic contrast while maintaining image density?
a. Increase the kVp and increase the exposure time.
b. Increase the kVp and decrease the exposure time.
c. Decrease the kVp and increase the exposure time.
d. Decrease the kVp and decrease the exposure time.
13. Based on the inverse square law, what happens to the
intensity of the x-ray beam when the target–image
receptor distance is doubled?
a. Intensity is doubled.
b. Intensity is not affected.
c. Intensity is one-half as great.
d. Intensity is one-fourth as great.
14. A radiographer stands 4 ft (1.22 m) from the head of the
patient while exposing a dental radiograph. Her personnel
monitoring device measures the radiation dose at that
position to be 0.04 millisievert (mSv). The radiographer
decides to move to a new location 8 ft (2.44 m) from the
head of the patient. What is the dose at the new location?
a. 0.01 mSv
b. 0.02 mSv
c. 0.08 mSv
d. 0.16 mSv
15. A patient presents whose radiographs must be taken utilizing the bisecting technique. The radiographer decides
to replace the 16-in. (41-cm) PID with an 8-in. (20.5-cm)
PID to better accommodate the bisecting technique. Currently the impulse setting, with the 16-in. (41-cm) PID, is
12. To maintain image density, what will the new impulse
setting be with the 8-in. (20.5-cm) PID?
a. 3
b. 6
c. 24
d. 48
REFLECT—Case study
You have just been hired to work in a new oral health care facility. Prior to providing patient services, you are asked to help
develop exposure settings and equipment recommendations for
the practice. The equipment and image receptor manufacturers’
suggestions are as follows:
F Speed Film 8-in. (20.5-cm) PID 85 kVp
Bitewings
Impulses
Adult Child
Posterior 10 8
Anterior 6 4
Periapicals
Maxillary anterior 8 6
Maxillary premolar 12 8
Maxillary molar 14 10
Mandibular anterior 6 4
Mandibular premolar 8 6
Mandibular molar 10 8
1. You recommend that the facility replace the 8-in. (20.5-
cm) PID with a 16-in. (41-cm) PID. Develop a new exposure chart for using the new 16-in. (41-cm) PID.
2. You recommend using a kVp setting of 70 when exposing radiographs for the purpose of detecting caries.
Develop a new exposure chart for 70 kVp.
3. You recommend using a kVp setting of 100 when exposing radiographs for the purpose of evaluating supporting
bone and periodontal disease. Develop a new exposure
chart for 100 kVp.
46 HISTORICAL PERSPECTIVE AND RADIATION BASICS
REFERENCES
Carestream Health Inc. (2007). Exposure and processing for
dental film radiography. Rochester, NY: Author.
Thomson, E. M., & Tolle, S. L. (1994). A practical guide for
using radiographs in the assessment of periodontal disease,
Part I. Practical Hygiene, 3(1):11–16.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Mosby
Elsevier.
RELATE—Laboratory application
Obtain an inanimate object of varying densities that can be
exposed at different exposure variables and compare the
results. For example expose a seashell placed on a size #2 intraoral film at the following exposure settings: 7 mA, 70 kVp, 10
impulses. Expose subsequent films varying one or more of the
exposure settings and process normally. Using a view box, analyze the resultant radiographic images. Identify which settings
produced darker or lighter images, and which settings produced
low or high contrast images.
CHAPTER
5
CHAPTER
OUTLINE
 Objectives 47
 Key Words 47
 Introduction 48
 Theories of
Biological Effect
Mechanisms 48
 Cell Sensitivity to
Radiation
Exposure 49
 The Dose–
Response Curve 49
 Factors That
Determine
Radiation Injury 50
 Sequence of
Events Following
Radiation
Exposure 51
 Radiation Effects
on Tissues of the
Body 51
 Short- and LongTerm Effects
of Radiation 51
 Risk Estimates 53
 Radiation Exposure
Comparisons 53
 Review, Recall,
Reflect, Relate 54
 References 56
Effects of Radiation
Exposure
PART II • BIOLOGICAL EFFECTS
OF RADIATION AND RADIATION
PROTECTION
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Explain the difference between the direct and indirect theories of biological damage.
3. Determine the relative radiosensitivity or radioresistance of various kinds of cells in the body.
4. Explain the difference between somatic and genetic effects.
5. Explain the difference between a threshold dose–response curve and a nonthreshold
dose–response curve.
6. Identify the factors that determine radiation injuries.
7. List the sequence of events that may follow exposure to radiation.
8. Explain the difference between deterministic and stochastic effects.
9. List the possible short- and long-term effects of irradiation.
10. Identify critical tissues for dental radiography in the head and neck region.
11. Discuss the risks versus benefits of dental radiographs.
12. Utilize effective dose equivalent to make radiation exposure comparisons.
13. Adopt an ethical responsibility to follow ALARA.
KEY WORDS
Acute radiation syndrome (ARS)
ALARA (as low as reasonably achievable)
Cumulative effect
Deterministic effect
Direct theory
Dose–response curve
Genetic cells
Genetic effect
Genetic mutation
Indirect theory
Ionization
Irradiation
Irreparable injury
Latent period
Law of B and T
Lethal dose (LD)
Nonthreshold dose–response curve
Period of injury
Radiolysis of water
Radioresistant
48 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
Introduction
Patients are often concerned with the safety of dental x-ray
procedures. Such concerns are shared by oral health care professionals. The fact that ionizing radiation produces biological
damage has been known for many years. The first x-ray burn
was reported just a few months following Roentgen’s discovery
of x-rays in 1895. As early as 1902, the first case of x-rayinduced skin cancer was reported in the literature. Events such
as the 1945 bombing of Hiroshima and the 1986 Chernobyl
nuclear power plant accident continued to generate unfavorable
attitudes toward ionizing radiation and concern over the use of
x-rays in dentistry and medicine as well. Although public concern is warranted, there are also some sensational and unsubstantiated articles appearing in newspapers and magazines, on
television, and on the Internet. Much of what we know about the
effects of radiation exposure comes from data that is extrapolated from high doses and high dose rates. Studies of occupational workers exposed to chronic low levels of radiation have
shown no adverse biological effect (U.S. Nuclear Regulatory
Commission, http://www.nrc.gov). However, even the radiation
experts have not been able to determine whether or not a threshold level exists below which radiation effects would not be a risk.
Because even the experts cannot always predict a specific outcome from an amount of radiation exposure, the radiation protection community conservatively assumes that any amount of
radiation may pose a risk. The purpose of this chapter is to
explain the theories of radiation injury and to identify factors
that increase the risk of producing a biological response.
Theories of Biological Effect Mechanisms
As pointed out in Chapter 2, x-rays belong to the ionizing portion of the electromagnetic spectrum. X-rays have the ability to
detach and remove electric charges from the complex atoms that
make up the molecules of body tissues. This process, known as
ionization, creates an electrical imbalance within the normally
stable cells. Because disturbed cellular atoms or molecules
generally attempt to regain electrical stability, they often accept
the first available opposite electrical charge. In such cases, the
undesirable chemical changes become incompatible with the
surrounding body tissues. During ionization, the delicate balance of the cell structure is altered, and the cell may be damaged or destroyed.
There are two generally accepted theories on how radiation
damages biological tissues: (1) the direct theory and (2) the indirect (radiolysis of water) theory (Figure 5-1).
• Direct theory: According to the direct theory, x-ray photons collide with important cell chemicals and break them
apart by ionization, causing critical damage to large molecules. One-third of biological alterations from x-radiation
exposure result from a direct effect. However, most dental
x-ray photons probably pass through the cell with little or
no damage. A healthy cell can repair any minor damage
that might occur. Moreover, the body contains so many
cells that the destruction of a single cell or a small group of
cells will have no observable effect.
• Indirect theory (Radiolysis of water): This theory is
based on the assumption that radiation can cause chemical
damage to the cell by ionizing the water within it (Figure 5-2).
Because about 80 percent of body weight is water and
ionization can dissociate water into hydrogen and hydroxyl
radicals, the theory proposes that new chemicals such as
hydrogen peroxide could be formed under certain conditions. These chemicals act as toxins (poisons) to the body,
causing cellular dysfunction. Two-thirds of biological alterations from x-radiation exposure result from indirect effects.
Fortunately, when the water is broken down during irradiation, the ions have a strong tendency to recombine immediately to form water again instead of seeking out new
combinations, keeping cellular damage to a minimum. Under
ordinary circumstances, even when a new chemical such as
X-ray
X-ray
Direct theory Indirect theory
FIGURE 5-1 Direct theory and indirect theory. In the
direct theory, x-ray photons collide with large molecules and
break them apart by ionization. The indirect theory is based on
the assumption that radiation can cause chemical damage to the
cell by ionizing the water within it.
KEY WORDS (Continued)
Radiosensitive
Recovery period
Risk
Somatic cells
Somatic effect
Stochastic effect
Threshold dose–response curve
CHAPTER 5 • EFFECTS OF RADIATION EXPOSURE 49
hydrogen peroxide is formed, other cells that are not affected
can take over the functions of the damaged cells until recovery takes place. Only in extreme instances, where massive
irradiation has taken place, will entire body tissues be
destroyed or death result. However, it should be remembered that cellular destruction is not the only biological
effect; the potential exists for the cell to become malignant.
Cell Sensitivity to Radiation Exposure
The terms radiosensitive and radioresistant are used to
describe the degree of susceptibility of various cells and
body tissues to radiation. All cells are not equally sensitive to
radiation. The relative sensitivity of cells to radiation was
first described in 1906 by two French scientists, Bergonie
and Tribondeau, and is known as the law of B and T. The
first half of the law of B and T states that actively dividing
cells, such as red blood cells, are more sensitive than slowly
dividing cells. The cell is most susceptible to radiation injury
during mitosis (cell division). Embryonic and immature cells
are more sensitive than mature cells of the same tissue. The
second half of the law of B and T states that the more specialized a cell is, the more radioresistant it is. The exceptions to
this law are white blood cells (lymphocytes) and reproductive cells (oocytes), which do not divide and are very specialized and yet are radiosensitive.
Based on these factors, it is possible to rank various kinds
of cells in descending order of radiosensitivity:
• White blood cells (lymphocytes) High sensitivity
• Red blood cells (erythrocytes)
• Immature reproductive cells
• Epithelial cells
• Endothelial cells
• Connective tissue cells
• Bone cells
• Nerve cells
• Brain cells
• Muscle cells Low sensitivity
Additionally, a distinction should be made between irradiation of somatic cells and reproductive cells. Somatic cells are
all the cells of the body, except the reproductive cells. A
somatic effect occurs when the biological change or damage
occurs in the irradiated individual, but is not passed along to
offspring. A genetic effect describes the changes in hereditary material that do not manifest in the irradiated individual,
but in future generations.
The experts do not fully understand all these effects or
their future consequences. Scientists believe that some of
these effects are cumulative, especially if exposure is too
great and the intervals between exposures too frequent for the
body cells to repair themselves. Unless the damage is too
severe or the subject is in extremely poor health, many body
cells (somatic cells) have a recovery rate of almost 75 percent
during the first 24 hours; after that, repair continues at the
same rate.
In determining whether or not an exposure is potentially
harmful, the radiographer should consider the quantity and the
duration of the exposure and which body area is to be
irradiated. Continued exposure over prolonged periods alters
the ability of the genetic cells (eggs and sperm) to reproduce
normally. Current evidence indicates that chromosome damage is cumulative, increasing in effect by each successive additional radiation exposure, and genetic cells cannot repair
themselves. Radiation may alter the genetic material in the
reproductive cells so that mutations (abnormalities) may be
produced in future generations.
The Dose–Response Curve
Radiation doses, like doses of drugs or other biologically harmful agents, can be plotted with response or damage produced, in
an attempt to establish acceptable levels of exposure. In plotting
these two variables, a dose–response curve is produced. A
threshold dose–response curve indicates that there is a “threshold” amount of radiation, below which no biological response
would be expected; a nonthreshold dose–response curve indicates that any amount of radiation, no matter how small, has the
potential to cause a biological response. These two possibilities
are illustrated in Figure 5-3.
X-Rays
H2O
Ionization
Water Free Radicals Toxins
Recombination
H2O
H2O
H+
H+
H+
HOOOHO- Hydrogen
peroxide
H2O2
FIGURE 5-2 Indirect theory. X-rays ionize water, resulting in the formation of free radicals, which recombine to form toxins.
50 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
Unfortunately, radiobiologists have been unable to determine radiation effects at very low levels of exposure (for example, doses below 100 mSv) and cannot be certain whether or
not a threshold dose exists. (To help put 100 mSv into perpective, a full mouth series of 18 F-speed films, at 90 kVp with 16-
in. [41-cm] length PID is approximately 30 mSv skin exposure.)
Therefore, the radiation protection community takes the conservative approach and considers any amount of ionizing radiation
exposure as being nonthreshold. This assumption has been
made in the establishment of radiation protection guidelines and
in radiation control activities. The concept that every dose of
radiation produces damage and should be kept to the minimum
necessary to meet diagnostic requirements is known as the
ALARA concept, where ALARA stands for as low as reasonably achievable. ALARA is explained in detail in Chapter 6.
Factors That Determine Radiation Injury
Biological responses to low doses of radiation exposure are
often too small to be detected. The body’s defense mechanisms
and ability to repair molecular damage often result in no residual effects. In fact, the following five outcomes are possible: (1)
nothing—the cell is unaffected by the exposure; (2) the cell is
injured or damaged but repairs itself and functions at preexposure levels; (3) the cell dies, but is replaced through normal biological processes; (4) the cell is injured or damaged, repairs
itself, but now functions at a reduced level; or (5) the cell is
injured or damaged and repairs itself incorrectly or abnormally,
resulting in a biophysical change (tumor or malignacy). Determining which of these five outcomes might occur depends on
all the following.
• Total dose: The total dose of radiation depends on the
type, energy, and duration of the radiation. The greater the
dose, the more severe the probable biological effect.
• Dose rate: The rate at which the radiation is administered
or absorbed is very important in the determination of what
effects will occur. Because a considerable degree of recovery occurs from the radiation damage, a given dose will
produce less effect if it is divided (thus allowing time for
recovery between dose increments) than if it is given in a
single exposure. For instance, an exposure of 1 R/week for
100 weeks would result in less injury than a single exposure of 100 R.
• Area exposed: The amount of injury to the individual
depends on the area or volume of tissue irradiated. The larger
the area exposed, other factors being equal, the greater the
injury to the organism. Intraoral dental radiographic exposures use a very small (2.75 in. or 7 cm) beam diameter (or
less if using rectangular collimation, see Figure 6-4) to
limit the area of radiation exposure to the area of diagnostic concern.
• Variation in species: Various species have a wide range of
radiosensitivity. Lethal doses for plants and microorganisms are usually hundreds of times higher than those for
mammals.
• Individual sensitivity: Individuals vary in sensitivity
within the same species. The genetic makeup of some individuals may pre-dispose them to ionizing radiation damage.
For this reason the lethal dose (LD) for each species is
expressed in statistical terms, usually as the LD 50/30 for
that species, or the dose required to kill 50% of the individuals in a large population in a 30-day period. For humans,
the LD 50/30 is estimated to be 4.5 gray (Gy) or 450 rad
(gray and rad are units of absorbed dose; see Chapter 2).
• Variation in cell sensitivity: Within the same individual,
a wide variation in susceptibility to radiation damage
exists among different types of cells and tissues. As the
law of B and T points out, cells with a potential for rapid
division are more sensitive to radiation than those that do
not divide. Furthermore, primitive or nonspecialized cells
are more sensitive than those that are highly specialized.
Within the same cell families, then, the immature forms,
which are generally primitive and rapidly dividing, are
more radiosensitive than the older, mature cells, which
have specialized function and have ceased to divide.
• Variation in tissue sensitivity: Some tissues (organs) of
the body are more radiosensitive than others. For instance,
blood-forming organs such as the spleen and red bone marrow are more sensitive than the highly specialized heart
muscle.
Response Response
Dose Dose
A B Threshold
FIGURE 5-3 Diagram of dose–response curve. (A) A typical “threshold” curve. The
point at which the curve intersects the base line (horizontal line) is the threshold dose that is
the dose below which there is no response. If an easily observable radiation effect, such as
erythema (reddening of the skin) is taken as “response,” then this type of curve is applicable.
(B) A linear “nonthreshold” curve, in which the curve intersects the base line at its origin.
Here it is assumed that any dose, no matter how small, causes some response.
CHAPTER 5 • EFFECTS OF RADIATION EXPOSURE 51
Radiation
injury
Time (age)
Irreparable injury
FIGURE 5-4 Concept of accumulated irreparable injury.
After exposure to radiation cell recovery can take place. However,
there may be a certain amount of damage from which no recovery
occurs, and it is this irreparable injury that can give rise to later longterm effects.
• Age: Younger, more rapidly dividing cells are more radiosensitive than older, mature cells, so it follows that children may
be more susceptible to injury than adults from an equal
dose of radiation. Also, in children the distance from the
oral cavity to the reproductive and other sensitive organs is
less than for adults. Therefore the dental doses to the critical organs may be higher than they would be for an adult.
Additionally, an increase in radiation sensitivity is observed
again in old age. As the body ages, the cells may begin to
lose the ability to repair damage.
Sequence of Events Following
Radiation Exposure
The sequence of events following radiation exposure are latent
period, period of injury, and recovery period, assuming, of course,
that the dose received was nonlethal.
• Latent period: Following the initial radiation exposure,
and before the first detectable effect occurs, a time lag
called the latent period occurs. The latent period may be
very short or extremely long, depending on the initial dose
and other factors described earlier. Effects that appear
within a matter of minutes, days, or weeks are called shortterm effects, and those that appear years, decades, and even
generations later are called long-term effects. Again, this
relates to the types of cells involved and their corresponding rates of mitosis (cell division).
• Period of injury: Following the latent period, certain
effects can be observed. One of the effects seen most frequently in growing tissues exposed to radiation is the stoppage of mitosis, or cell divisions. This may be temporary
or permanent, depending on the radiation dosage. Other
effects include breaking or clumping of chromosomes,
abnormal mitosis, and formation of giant cells (multinucleated cells) associated with cancer.
• Recovery period: Following exposure to radiation, some
recovery can take place. This is particularly apparent in the
case of short-term effects. Nevertheless, there may be a
certain amount of damage from which no recovery occurs,
and it is this irreparable injury that can give rise to later
long-term effects (Figure 5-4).
Radiation Effects on Tissues of the Body
Low levels of radiation exposure do not usually produce an
observable adverse biological effect. As the dose of radiation
increases and enough cells are destroyed, the affected tissue
will begin to exhibit clinical signs of damage. The severity of
these clinical manifestations is dependent on the dose and dose
rate. For example, erythema (redness of the skin) would not be
expected from exposing the skin to sunlight for a few seconds.
However, as the time of exposure to sunlight increased, the erythema would be expected to increase proportionally. When the
severity of the change is dependent on the dose, the effect is
called a deterministic effect.
When a biological response is based on the probability of
occurrence rather than the severity of the change, it is called a
stochastic effect. The occurrence of cancer is a stochastic effect
of radiation exposure; it is an “all-or-nothing” occurrence. When
the dose of radiation is increased, the “probability” of the stochastic effect (cancer) occurring increases, but not its severity.
Short- and Long-term Effects of Radiation
The effects of radiation are classified as either short term or long
term. Short-term effects of radiation are those seen minutes,
days, or months after exposure. When a very large dose of radiation is delivered in a very short period of time, the latent period
is short. If the dose of radiation is large enough (generally over
1.0 Gy or 100 rads, whole-body), the resultant signs and symptoms that comprise these short-term effects are collectively
known as acute radiation syndrome (ARS). ARS symptoms
include erythema (redness of the skin), nausea, vomiting, diarrhea, hemorrhage, and hair loss. ARS is not a concern in dentistry because dental x-ray machines cannot produce the very
large exposures necessary to cause it.
Long-term effects of radiation are those that are seen years
after the original exposure. The latent period is much longer
(years) than that associated with the acute radiation syndrome
(hours or days). Delayed radiation effects may result from a previous acute, high exposure that the individual has survived or
from chronic low-level exposures delivered over many years.
No unique disease associated with the long-term effects of
radiation has been established. Instead, there can be a statistical
increase in the incidence of certain conditions that can have
causes other than radiation exposure such as cancer, embryological defects, low birth weights, cataracts, (somatic effects), and
genetic mutations (genetic effect). Because of the low normal
incidence of these conditions, one must observe large numbers
of exposed persons to evaluate the increases as an effect of
long-term radiation exposure.
The long-term effects observed have been somatic damage,
which may result in an increased incidence of the following.
52 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
• Cancer: Anything that is capable of causing cancer is
called a carcinogen. X-rays, like certain drugs, chemicals,
and viruses, have been shown to have carcinogenic effects.
Carcinogenic mechanisms are not clearly understood.
Moreover, cancer is probably “caused” by the simultaneous interaction of several factors, and the presence of some
of these factors without the others may not be sufficient to
cause the disease.
Some explanations for the carcinogenic action of
x-rays include the following: x-rays activate viruses
already present in cells; x-rays damage chromosomes, and
certain diseases (such as leukemia) are associated with
chromosomal injury; x-rays cause mutations in somatic
cells, which may result in uncontrolled growth of cells;
and x-rays ionize water, which results in chemical “free
radicals” that may cause cancer.
Any one or a combination of these theories may explain
how cancer is caused. X-radiation is only one of a number
of possible carcinogens involved, and the precise mechanism
is not yet understood. Much of the evidence that x-radiation
is carcinogenic comes from studies of early radiation
workers, including dentists, who were exposed to large
amounts of radiation (Figures 5-5 and 5-6).
• Embryological defects: The immature, undifferentiated,
rapidly growing cells of the embryo are highly sensitive to
radiation. The first trimester of a pregnancy when the
fetus undergoes the period of major organogenesis (formation of organs) is especially critical. High doses of radiation may cause birth abnormalities, stunting of growth,
and mental retardation. It is important to note that the dose
from a dental x-ray examination is less than 0.0003 to
0.003 milligray (0.03 to 0.3 millirad), and the use of a lead
or lead-equivalent barrier apron reduces this potential dose
to zero.
• Low birth weight: Medical (not dental) x-radiation exposure
of pregnant females has been associated with an increase
in the incidence of full-term pregnancies resulting in
below-normal-birth-weight infants. Because the reproductive
organs are not located in a critical area, exposure of necessary
dental radiographs has not been contraindicated during
pregnancy. In 2004 the American Medical Association
published research that investigated the effect on pregnancy
outcomes of radiation exposure of the pregnant female’s
hypothalamus and the pituitary and thyroid glands. This
research suggests that dental radiation exposure may be
associated with full-term low-birth-weight infants. More
research in this area may lead to altered guidelines on the
assessment of pregnant females for dental radiographs.
(Discussed further in Chapter 27.)
• Cataracts: When the lens of the eye becomes opaque, it is
called a cataract. Various agents, including x-rays, have
been known to cause cataracts. It takes at least 2 Gy (200
rads) of x-radiation to cause cataract formation. The dose to
the eye from dental radiographic procedures is in the order
of milligray (millirad). Dental x-rays have never been
reported to cause cataracts.
• Genetic mutations: The genetic material is the means by
which hereditary traits are passed from one generation to
another. In addition to x-radiation, drugs, chemicals, and
even elevated body temperatures are also capable of causing mutations. Genetic effects are especially important
because it is unknown what size dose of radiation, whether
naturally occurring or from man-made sources, may be
capable of producing a change in the genetic material of
cells.
Because the scatter radiation reaching the gonads from
dental radiography is less than 0.0001 that of the exposure
to the surface of the face (ranging from 0.0 to about 0.002
milligrays [0.2 millirad] per radiograph), the risk of genetic
mutations is extremely small. Furthermore, by using a lead
or lead-equivalent barrier apron and thyroid collar, the dose
is essentially reduced to zero.
FIGURE 5-5 Ulcerated lesion. Early carcinoma on the finger of a
dentist who admitted holding films in the patient’s oral cavity during
exposure.
FIGURE 5-6 Radiation injury on the finger of a dentist
caused by holding films in the patient’s oral cavity during
exposure. A lesion of this type would be likely to result in squamous
cell carcinoma (cancer).
CHAPTER 5 • EFFECTS OF RADIATION EXPOSURE 53
TABLE 5-1 Critical Organs and Doses for Dental Radiography
CRITICAL
ORGAN EFFECT
MINIMUM DOSE REQUIRED
TO PRODUCE EFFECT
DENTAL DOSE
FROM AN FMS
Eye cataract 2,000 mSv 0.4 mSv
Hematopoietic leukemia 50 mSv 8.0 mSv
Skin cancer 250 mSv 12.6 mSv
Thyroid gland cancer 65 mSv 0.4 mSv
Gonads sterility 4,000 to 6,000 mSv 0.005 mSv (no lead apron)
to 0.0003 mSv (lead apron)
Risk Estimates
A risk may be defined as the likelihood of injury or death from
some hazard. The primary risk from dental radiography is radiation-induced cancer and, possibly, the potential to affect pregnancy
outcomes. Otherwise, the facial and oral structures, composed
largely of bone, nerve, and muscle tissue, are fairly radioresistant
(Table 5-1).
Risk estimates vary, depending on several factors, such as
speed of film, collimation, and the technique used. In dental radiography, the most critical tissues of the head and neck are the
mandible (red bone marrow), the lens of the eye, the thyroid gland,
and possibly the hypothalamus-pituitary-thyroid combination.
The mandible contains an estimated 15 g of red bone
marrow. However, it should be noted that this is only about 1
percent of the total amount of red bone marrow in the adult
body. Although x-radiation can cause cataracts, the dental
radiation exposure to the lens of the eye during some maxillary exposures is well below the dose needed to produce
cataracts. The thyroid gland is relatively radiosensitive.
Until recently the focus has been on radiation exposure
causing cancer of the thyroid gland. A study published in the
Journal of the American Medical Association (2004) has
demonstrated a possible link between radiation exposure to the
thyroid gland and/or to the hypothalamus-pituitary-thyroid
combination of a pregnant female and low-birth-weight
infants delivered after the full 9-month term. Until more is
documented regarding this phenomenon, the focus is on
radiation-induced cancer as the primary risk from dental
radiography.
The potential risk of a full mouth dental x-ray examination
inducing cancer in a patient has been estimated to be 2.5 per
1,000,000 examinations. It should be noted that every day we
assume hundreds of risks such as climbing stairs, crossing the
street, riding a bicycle, and driving a car. Activities with a fatality risk of 1 in 1,000,000 include riding 300 miles in an automobile, traveling 1,000 miles in an airplane, or smoking 1.4
cigarettes a day (Table 5-2). People accept these risks every day
because we perceive a benefit from them.
• Risk versus benefit: Dental radiographs should be taken
only when the benefit outweighs the risk of biologic injury
to the patient. When dental radiographs are properly prescribed (see Chapter 6), exposed, and processed, the health
benefits to the patient far outweigh any risk of injury.
There have been no reports of radiation injuries caused by
normal dental procedures since safety protocols have been
adopted.
Radiation Exposure Comparisons
Patients often have questions regarding the amount of radiation
dental radiographs are adding to their accumlated lifetime exposure. The exact amount of radiation exposure produced when
taking dental radiographs varies, depending on many factors,
such as the film speed, technique used, and collimation type (circular or rectangular). Additionally, dental exposures are often
quoted as skin surface amounts rather than amounts to the more
important bone marrow and other deeper structures
The effective dose equivalent (Chapter 2) can be used to compare dental radiation exposures with days of natural background
exposure. The average effective dose equivalent from naturally
TABLE 5-2 One in One Million Fatality Risk
sRISK NATURE
Smoking 1.4 cigarettes/day Cancer
Riding 10 miles on a bicycle Accident
Travel 300 miles by auto Accident
Travel 1,000 miles by airplane Accident
PRACTICE POINT
Dental radiographs should be prescribed only when necessary. Consider the following case: If a female patient is
assessed for bitewing radiographs, and then she reveals that
she may be pregnant, would the need for the bitewing radiographs change? Would she still need the radiographs? Or
would these once-needed radiographs now be radiographs
that can wait? If radiographs can wait, they are not necessary
radiographs.
54 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
occuring background radiation to the population of the United
States is approximately (microseiverts) per day. A full
mouth series of radiographs using F-speed film and a round PID
has an effective dose equivalent of approximately
Therefore, the full mouth series is equal to approximately 2.9 days
of naturally occurring background radiation exposure (Table 5-3).
23.4 mSv.
8 mSv REVIEW—Chapter summary
Ionizing radiation has the potential to produce biological damage because x-rays can detach subatomic particles from larger
molecules and create an imbalance within a normally stable cell.
The two generally accepted theories on how radiation may cause
damage to cellular tissues are: (1) the direct theory, and (2) the
indirect theory or the radiolysis of water. Whether cell damage
from radiation is physical or chemical, it has been established
that minor damage is soon repaired by a healthy body.
The terms radiosensitive and radioresistant are used to
describe the degree of susceptibility of various cells and body
tissues to radiation. According to the law of B and T, cells that
are highly specialized and have a lesser reproductive capacity
are considered to be radioresistant, and cells that are undifferenciated and have a greater capacity for reproduction are considered to be radiosensitive.
Biological changes or damage that occur in somatic cells
will affect the irradiated individual but will not be passed along
to offspring. Biological changes or damage that do not affect
the irradiated individual but are passed to future generations are
called genetic effects.
The cumulative effect of irradiation is defined as an
amount of radiation damage from which no recovery occurs,
giving rise to later long-term effects.
The dose–response curve is a method used to plot the
dosage of radiation administered with the response produced to
establish responsible levels of radiation exposure. The conservative view that every dose of radiation potentially produces
damage and should be kept to a minimum is expressed by the
ALARA concept—as low as reasonably achievable.
TABLE 5-3 Effective Dose Equivalenta
EXAMINATION EFFECTIVE DOSE DAYS OF NATURAL EXPOSUREb
Single intraoral exposurec 1.3 MSv 0.2
Bitewing radiographs (4 films) c 5.2 MSv 0.7
Full mouth series (18 films) c 23.4 MSv 2.9
Panoramic radiograph 7 MSv 0.9
CT scan of the maxilla 240–1200 MSv 40–200
CT scan of the mandible 480–3324 MSv 80–547.5
Cone beam CT mandible 75 MSv 12.5
Cone beam CT maxilla 42 MSv 7
Chest x-ray 80 MSv 10
Upper GI 2440 MSv 305
Lower GI 4060 MSv 507.5
References: White, S. C., & Pharoah, M. (2008). Oral radiology: Principles and interpretation (6th ed.).
St. Louis, MO: Elsevier, and Horner, K., Drage, N., & Brettle, D. (2008). 21st century imaging. London:
Quintessence Publishing Co Ltd.
Fractions rounded up.
F-speed, round PID. c
b
a
PRACTICE POINT
Be careful not to tell the patient that a full mouth series is
equal to 2.9 days “in the sun.” Naturally occurring background radiation includes not only the sun, or cosmic
energy, but also terrestrial and internal sources of background radiation (see Chapter 2). Additionally, most
patients are aware that exposure to the sun’s rays is harmful
and many take precautions against putting themselves at
risk for skin damage. To compare dental x-rays to sun exposure may provoke a response from the patient to avoid dental x-rays as well.
Much about radiation effects remains to be discovered.
Future research may demonstrate that human beings are not as
sensitive to radiation damage as we now believe. But until we
have such evidence, common sense dictates improving radiographic safety techniques in every way possible.
CHAPTER 5 • EFFECTS OF RADIATION EXPOSURE 55
5. Which of these cells are most radiosensitive?
a. Brain cells
b. Nerve cells
c. White blood cells
d. Mature bone cells
6. Which of these cells are most radioresistant?
a. Endothelial cells
b. Muscle cells
c. Epithelial cells
d. Red blood cells
7. When the effect of a radiation exposure is observed in the
offspring of an irradiated person, but not in the irradiated
person, this is called the
a. somatic effect.
b. genetic effect.
c. direct effect.
d. indirect effect.
8. A dose–response curve indicating that any amount of radiation, no matter how small, has the potential to cause a biological response is called
a. stochastic
b. deterministic
c. threshold
d. nonthreshold
9. ALARA stands for ____________________.
10. List the five possible biological responses of an irradiated
cell.
a. ______________
b. ______________
c. ______________
d. ______________
e. ______________
11. Each of the following is a factor that determines radiation
injury EXCEPT one. Which one is the EXCEPTION?
a. Size of the irradiated area
b. Amount of radiation
c. Patient gender
d. Dose rate
12. According to the factors that determine radiation injury,
based on age, who is the most radiosensitive?
a. a 6-year-old
b. a 16-year-old
c. a 26-year-old
d. a 46-year-old
13. Which of the following is the correct sequence of events
following radiation exposure?
a. Period of injury, latent period, recovery period
b. Latent period, period of injury, recovery period
c. Latent period, recovery period, period of injury
d. Recovery period, latent period, period of injury
Factors that influence a biological response to irradiation
include dose amount, dose rate, area exposed, species exposed,
individual sensitivity, cell sensitivity, tissue sensitivity, and age.
Assuming that the dose received is not lethal, the sequence of
events following radiation exposure are (1) a latent period, (2) a
period of injury, and (3) a recovery period.
The term deterministic is used when referring to a tissue
response, such as erythema, whose severity is directly related to
the radiation dose. The term stochastic effect is used when
referring to a tissue response, such as cancer, that is based on
the probability of occurrence rather then the severity of the
response.
The effects of radiation exposure may be short or longterm.
Short-term effects include erythema and general discomfort.
Long-term effects may result in an increased incidence of cancer, embryological defects, poor pregnancy outcomes, cataracts,
and genetic mutations.
The potential benefits of dental radiographs outweigh the
risk. With proper radiation safety protocol, there is minimal
risk of injury caused by necessary dental radiographic procedures. The critical tissues in the head and neck are (1) the red bone
marrow in the mandible, (2) lens of the eye, and (3) thyroid gland,
but most facial tissues are fairly radioresistant.
The effective dose equivalent can be used to compare
the risks of different radiation exposures and to compare
dental radiation exposures with days of natural background
exposure.
RECALL—Study questions
1. The primary cause of biological damage from radiation is
a. ionization.
b. direct effect.
c. indirect effect.
d. genetic effect.
2. Direct injury from radiation occurs when the x-ray
photons
a. ionize water and form toxins.
b. pass through the cell.
c. strike critical cell molecules.
d. All of the above.
3. Indirect injury from radiation occurs when the x-ray
photons
a. ionize water and form toxins.
b. pass through the cell.
c. strike critical cell molecules.
d. All of the above.
4. According to the law of B and T, cells with a high
reproductive rate are described as
a. radiopaque.
b. radiolucent.
c. radioresistant.
d. radiosensitive.
56 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
14. When a biological response is based on the probability
of occurrence rather than the severity of the change, it is
called a
a. short-term effect.
b. long-term effect.
c. deterministic effect.
d. stochastic effect.
15. Which of these is considered a short-term outcome following radiation exposure?
a. Embryological defects
b. Cataracts
c. Acute radiation syndrome
d. Cancer
16. Full-term, low birth weight is possibly associated with
radiation exposure to which of the following?
a. Thyroid gland
b. Hypothalamus
c. Pituitary gland
d. All of the above
17. During exposure of an intraoral dental radiograph,
approximately how much smaller is the dose of radiation in the gonadal area than at the surface of the
face?
a. 0.10
b. 0.01
c. 0.001
d. 0.0001
18. Each of the following is in the path of the x-ray beam during exposure of an intraoral dental radiograph on an adult
patient. Which one, because of its relative radioresistancy
is NOT considered critical for dental radiography?
a. Mandible
b. Lens of the eye
c. Spinal cord
d. Thyroid gland
19. The potential risk of a full mouth dental x-ray examination inducing cancer in a patient has been estimated to be
a. 2.5 per 1,000 examinations.
b. 2.5 per 10,000 examinations.
c. 2.5 per 100,000 examinations.
d. 2.5 per 1,000,000 examinations.
20. What term best expresses comparisons between dental
radiation exposures and natural background exposure?
a. Absorbed dose
b. Effective dose equivalent
c. Accumulated dose
d. Lethal dose
REFLECT—Case study
Retaking a radiograph because of a technique or processing
error causes an increase in radiation exposure for the patient.
Discuss ways a retake radiograph affects the factors that determine radiation injury.
RELATE—Laboratory application
Calculate your radiation dose. Visit the United States Environmental
Protection Agency at http://www.epa.gov/radiation/understand/
calculate.html, where you can estimate your average annual
radiation dose. Based on the questions posed by this calculator,
what conclusions can you draw about (1) the source of radiation
exposure, (2) the region in which people live, (3) sources of
internal radiation exposure, and (4) situations and/or products
with the ability to increase your dose of radiation exposure?
REFERENCES
American Dental Association Council on Scientific Affairs.
(2006). The use of dental radiographs: Update and recommendations. Journal of the American Dental Association,
137(9), 1304–1312.
Carestream Health Inc. (2007). Kodak Dental Systems. Radiation safety in dental radiography., Rochester NY: Author.
Hujoel, P. P., Bollen, A., Noonan, C. J., & del Aguila, M. A.
(2004). Antepartum dental radiography and infant low birth
weight. JAMA, 291(16), 1987–1993.
National Council on Radiation Protection and Measurements.
(2009). Report No 160: Ionizing radiation exposure of the
population of the United States. Bethesda, MD: Author.
National Council on Radiation Protection and Measurements.
(1991). Implementation of the principle of as low as reasonably achievable (ALARA) for medical and dental personnel. NCRP report no. 107. Washington, DC: Author.
United States Nuclear Regulatory Commission. (2007,
December 4). Standards for protection against radiation,
Title 10, Part 20, of the Code of Federal Regulations.
Retrieved April 11, 2010, from http://www.nrc.gov/reading-rm/doc-collections/cfr/part020/part020-1201.html
U.S. Nuclear Regulatory Commission. (2010). Radiation protection. Retrieved April 16, 2010, from http://www.nrc.
gov/about-nrc/radiation.html
White, S. C., & Pharoah, M. J. (2008) Oral radiology: Principles
and interpretation (6th ed.). St. Louis, MO: Mosby Elsevier.
CHAPTER
Radiation Protection 6
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Adopt the ALARA concept.
3. Use the selection criteria guidelines to explain the need for prescribed radiographs.
4. Explain the roles communication, working knowledge of quality radiographs, and education
play in preventing unnecessary radiation exposure.
5. Explain the roles technique and exposure choices play in preventing unnecessary radiation
exposure.
6. Explain the function of the filter.
7. State the filtration requirements for an intraoral dental x-ray unit that operates above and
below 70 kVp.
8. Compare inherent, added, and total filtration.
9. State the federally mandated diameter of the intraoral dental x-ray beam at the patient’s
skin.
10. Explain the difference between round and rectangular collimation.
11. List the two functions of a collimator.
12. Explain how PID shape and length contribute to reducing patient radiation exposure.
13. Identify film speeds currently available for dental radiography use.
14. Explain the role image receptor holders play in reducing patient radiation exposure.
15. Advocate the use of the lead/lead equivalent thyroid collar and apron.
16. Explain the role darkroom protocol and film handling play in reducing patient radiation
exposure.
17. Summarize the radiation protection methods for the patient.
18. Explain the roles time, shielding, and distance play in protecting the radiographer from
unnecessary radiation exposure.
19. Utilize distance and location to take a position the appropriate distance and angle from the
x-ray source at the patient’s head during an exposure.
20. Describe monitoring devices used to detect radiation.
21. Summarize the radiation protection methods for the radiographer.
22. List the organizations responsible for recommending and setting exposure limits.
23. State the maximum permissible dose (MPD) for radiation workers and for the general public.
CHAPTER
OUTLINE
 Objectives 57
 Key Words 58
 Introduction 58
 ALARA 58
 Protection
Measures for the
Patient 58
 Protection
Measures for the
Radiographer 66
 Radiation
Monitoring 67
 Organizations
Responsible for
Recommending/
Setting Exposure
Limits 70
 Guidelines for
Maintaining Safe
Radiation Levels 71
 Review, Recall,
Reflect, Relate 71
 References 73
58 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
Introduction
In Chapter 5 we learned that radiation exposure in sufficient
doses may produce harmful biological changes in humans.
Although it is the consensus of radiobiologists that the dose
received from a dental x-ray exposure is not likely to be harmful, even the experts do not know what risk a small dose carries.
Therefore, it must be assumed that any dose may be capable of
potential risk. The patient has agreed to be subjected to the
risks of radiation exposure because he/she believes that the oral
health care practitioner will follow safety protocols that protect
the patient from excess exposure.
In this chapter we discuss radiation safety protocols,
including selection criteria used in prescribing dental radiographs
and methods to minimize x-ray exposure to both the dental
patient and the radiographer.
ALARA
The oral health care team has an ethical responsibility to
embrace the ALARA (as low as reasonably achievable) concept, recommended by the International Commission on Radiological Protection to minimize radiation risks. The ALARA
concept implies that “any radiation dose that can be reduced
without major difficulty, great expense, or inconvenience should
be reduced or eliminated.” ALARA is not simply a phrase, but a
culture of professional excellence. ALARA should guide practice principles. In an ideal world, the oral health care team
would like to get the diagnostic benefits of dental radiographs
with a zero dose radiation exposure to the patient. In reality, this
is not possible; all dental radiographs will result in a small but
acceptable level of risk. The best way to prevent this risk from
increasing is to keep the exposure ALARA.
Protection Measures for the Patient
Professional Judgment
The benefits of radiographs in dentistry outweigh the risks
when proper safety procedures are followed. The most
KEY WORDS
Added filtration
ALARA (as low as
reasonably achievable)
Aluminum equivalent
Area monitoring
Collimation
DIS (direct ion storage)
monitor
Dosimeter
Exposure factors
Film badge
Film/image receptor holder
Filter
Filtration
Half-value layer
Inherent filtration
Lead apron
Lead equivalent
Monitoring
MPD (maximum permissible dose)
OSL (optically stimulated
luminescence) monitor
Personnel monitoring
Personnel monitoring device
PID (position indicating device)/BID
(beam indicating device)
Primary beam
Protective barrier
Radiation leakage
Radiation worker
Retake radiograph
Scatter (secondary)
radiation
Selection criteria
Structural shielding
TLD (thermoluminescent
dosimeter)
Thyroid collar
Total filtration
important way to ensure that the patient receives a reasonably low dose of radiation is to use evidence-based
selection criteria when determining which patients need
radiographs. Guidelines developed by an expert panel of
health care professionals convened by the Public Health
Service and adopted by the American Dental Association
have been published to assist in deciding when, what type,
and how many radiographs should be taken (Table 6-1).
These guidelines allow the dentist to base the decision
regarding x-rays for the patient on expert recommendations. Although the dentist prescribes the radiographic
exam for the patient based on these guidelines, these recommendations are subject to clinical judgment and may not
apply to every patient.
Evidence-based selection criteria guidelines are applied
only after reviewing the patient’s health history and completing a clinical examination. The time frames suggested in
the guidelines are used in the absence of positive historical
findings and signs and symptoms presented by the patient.
For example, a patient who presents with a toothache would
most likely be assessed for a radiographic exam of this
symptom even if the patient had radiographs within the
suggested time frame for this patient’s category. Additionally, a radiographic examination should not wait until a
patient presents with pain or other symptom of pathology.
The time frames suggested by the selection criteria guidelines are preventive measures that are evidence-based effective. The dentist uses these guidelines to prescribe the
radiographic exam for the patient, but the dental hygienist
may use the guidelines during initial examination of the
patient to make a preliminary assessment for the recommendation of radiographic need; the dental hygienist and the
dental assistant rely on the selection criteria guidelines to
assist with explaining radiographic need to the patient. Once
the decision to expose radiographs is made, every reasonable effort must be made to minimize exposure to the patient
and to the operator and to those who may be in the area of
the x-ray machine.
CHAPTER 6 • RADIATION PROTECTION 59
• Education. Continuing education is the cornerstone of
all health care professions. Rapidly advancing technology is constantly changing the scope of oral health care
Technical Ability of the Operator
• Communication. Reduction of radiation exposure begins
with communication skills. The patient’s cooperation must
be secured to perform radiographic examinations accurately
and safely. Patient protection during a radiographic procedure should begin with clear, concise instructions. When
responsibilities are adequately defined through effective
communication, the patient understands what must be done
and can more fully cooperate with the radiographer and
avoid retake mistakes.
• Working knowledge of quality radiographs. The radiographer should understand what a quality dental radiograph
should image. Based on this knowledge, the radiographer
needs to take every precaution against retaking radiographs.
Retake radiographs are necessary when the first exposure
results in errors that compromise image quality. When a radiograph is retaken, the second exposure doubles the dose and
dose rate of radiation for the patient. The best way to avoid
retake radiographs is to develop an understanding of common technique and processing errors (see Chapter 18).
Armed with this knowledge, the radiographer can better
avoid mistakes that lead to an increase in patient radiation
exposure.
PRACTICE POINT
Not every undiagnostic radiograph must be retaken. If multiple radiographs are taken at the same time, for example,
when exposing a full mouth series or set of bitewings the
radiographer should check to see if the area of interest is
imaged on an adjacent radiograph. Sometimes a retake radiograph may be avoided if the area of interest is imaged diagnostically on an adjacent radiograph.
practice. Some of the methods and procedures learned
for the practice of oral health care just a few years ago
may be obsolete in today’s world. For example, we are
currently witnessing the possible elimination of filmbased dental radiography. With the increasing use of
computers and the advancement of digital imaging, new
technology will surely contribute to the reduction of
dental radiation exposure. The radiographer who continues to learn about and adopt these new practices will
further help decrease radiation exposure for the patient
and the radiographer.
Technique Standards
• Intraoral technique choice. The paralleling technique
should be the operator’s first choice when exposing
periapical radiographs. The paralleling technique yields
more accurate and precisely sized radiographic images
(see Chapter 14). However, consideration should also
be given to which technique, paralleling or bisecting,
will produce the best results for the patient. The more
efficient and convenient the technique, the less likely
there will be retake radiographs. The radiographer should
be skilled at both techniques and should possess the
knowledge on which to base the decision regarding
which one to use.
• Exposure factors. Operating the dental x-ray machine
includes selecting the appropriate exposure factors—
kilovoltage (kVp), milliamperage (mA), and time—for the
patient and the area to be imaged. The radiographer should
possess a working knowledge of appropriate exposure
factors to avoid overexposing the patient unnecessarily.
Underexposures can also lead to additional exposures for
the patient if a retake is necessary. A working knowledge
of the exposure factors includes the ability to adjust each
of the variables—kilovoltage (kVp), milliamperage (mA),
and time—in relation to each other. In Chapter 4, we
learned that an adjustment in one variable usually leads
to a necessary counteradjustment in another variable to
maintain exposure control. To assist in radiation safety,
exposure charts should be posted near the control panel for
easy reference.
Equipment Standards
Using proper equipment is the next step in reducing radiation
exposure to the patient. All dental x-ray machines in the
United States are safe from a radiological health point of view.
The Federal Performance Standard for Diagnostic X-Ray
Equipment became effective on August 1, 1974. The provisions
of the standard require that all x-ray equipment manufactured
after that date meet certain radiation safety requirements
including filtration, collimation, and PID (position indicating
device).
• Filtration is the absorption of the long wavelength, less
penetrating, x-rays of the polychromatic x-ray beam by
PRACTICE POINT
Completing an accurate dental history may reveal that a new
patient has recently had radiographs taken at another oral
health care practice. Every effort should be made to have a
copy of these radiographs forwarded to your practice to
avoid additional radiation exposure for the patient.
60 TABLE 6-1 Guidelines for Prescribing Dental Radiographs
TYPE OF
ENCOUNTER
CHILDREN ADOLESCENT ADULT
Primary Dentition
(prior to eruption
of first permanent
tooth)
Transitional
Dentition (after
eruption of first
permanent tooth)
Permanent
Dentition (prior
to eruption of
third molars)
Dentate
or Partially
Edentulous Edentulous
New Patient
Being evaluated
for dental disease
and dental
development
Individualized radiographic exam
consisting of selected periapical/ occlusal views and/or posterior bitewings if proximal
surfaces cannot be visualized
or probed. Patients without
evidence of disease and with
open proximal contacts may
not require a radiographic
exam at this time.
Individualized radiographic
exam consisting of posterior bitewings with
panoramic exam or posterior bitewings and
selected
periapical images.
Individualized radiographic exam consisting of posterior bitewings
with panoramic exam or posterior bitewings
and selected periapical images. A full mouth intraoral
radiographic exam is preferred when the patient has
clinical evidence of generalized dental disease or a history of extensive dental treatment.
Individualized
radiographic
exam, based on
clinical signs
and symptoms.
Recall Patient*
With clinical caries or
at increased risk for
caries**
Posterior bitewing exam at 6- to 12-month intervals if proximal
surfaces cannot be examined visually or with a probe.
Posterior bitewing exam
at 6- to 18-month intervals.
Not applicable.
Recall Patient*
With no clinical caries
and not at risk for
caries**
Posterior bitewing exam at 12- to 24-month intervals if proximal surfaces cannot be examined visually or with a probe. Posterior bitewing exam at 18- to 36-month
intervals.
Posterior bitewing exam at
24- to –
36-month intervals.
Not applicable.
Recall Patient
With periodontal
disease
Clinical judgment as to the need for and type of radiographic images for the evaluation of periodontal disease. Imaging may consist of,
but is not limited to, selected bitewing and/or periapical images of areas where periodontal disease
(other than nonspecific gingivitis) can be identified clinically.
Not applicable.
Patient
For monitoring of
growth and
development
Clinical judgment as to the need for and type of radiographic
images for the evaluation and/or monitoring of dentofacial
growth and development.
Clinical judgment as to the need for and
type of radiographic images for evaluation and/or monitoring of dentofacial
growth and development. Panoramic
or periapical exam to assess developing third molars.
Not usually indicated.
61
Patient
With other circumstances including,
but not limited to,
proposed or existing
implants, pathology,
restorative/endodontic needs, treated
periodontal disease
and caries
remineralization.
Clinical judgment as to the need for and type of radiographic images for the evaluation and/or monitoring in these circumstances.
Clinical situations for which radiographs may be indicated include but are not limited to:
A. Positive historical findings
1. Previous periodontal or endodontic treatment
2. History of pain or trauma
3. Familial history of dental anomalies
4. Postoperative evaluation of healing
5. Remineralization monitoring
6. Presence of implants or evaluation for impact placement
B. Positive clinical signs/symptoms
1. Clinical evidence of periodontal disease
2. Large or deep restorations
3. Deep carious lesions
4. Malposed or clinically impacted teeth
5. Swelling
6. Evidence of dental/facial trauma
7. Mobility of teeth
8. Sinus tract (“fistula”)
9. Clinically suspected sinus pathology
10. Growth abnormalities
11. Oral involvement in known or suspected systemic disease
12. Positive neurologic findings in the head and neck
13. Evidence of foreign objects
14. Pain and/or dysfunction of the temporomandibular joint
15. Facial asymmetry
16. Abutment teeth for fixed or removable partial prosthesis
17. Unexplained bleeding
* 18. Unexplained sensitivity of teeth
19. Unusual eruption, spacing, or migration of teeth
20. Unusual tooth morphology, calcification, or color
21. Unexplained absence of teeth
22. Clinical erosion
Factors increasing risk for caries may include but are not limited to:
1. High level of caries experience or demineralization
2. History of recurrent caries
3. High titers of cariogenic bacteria
4. Existing restoration(s) of poor quality
5. Poor oral hygiene
6. Inadequate fluoride exposure
7. Prolonged nursing (bottle or breast)
8. High-sucrose frequency diet
9. Poor family oral health
10. Developmental or acquired enamel defects
11. Developmental or acquired disability
12. Xerostomia
13. Genetic abnormality of teeth
14. Many multisurface restorations
15. Chemo/radiation therapy
16. Eating disorders
17. Drug/alcohol abuse
18. Irregular dental care
Data from U.S. Dept. of Health and Human Services: The Selection of Patients for Dental
Radiographic Examinations. Revised 2004 by the American Dental Association: Council
on Dental Benefit Program, Council on Dental Practice, Council on Scientific Affairs.
**
62 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
x-rays, but will absorb a high percentage of the lowenergy x-rays. The latter do not contribute to the radiographic image. Low-energy x-rays are harmful to the
patient because they are absorbed by the skin, increasing
the patient’s dose (Figure 6-2).
Any material the x-ray beam passes through filters the
beam. Filtration may be built into the tube head (inherent),
or it may be added.
Inherent filtration is the filtration built into the machine by
the manufacturer. This includes the glass of the x-ray tube,
the insulating oil, and the material that seals the port. All x-ray
units have some built-in filtration. Usually the inherent filtration is not sufficient to meet state and federal standards,
requiring that filtration be added.
Added filtration is the placement of aluminum discs in
the path of the x-ray beam between the port seal of the
tube head and the PID. When the inherent filtration is not
sufficient to meet safety standards, a disk of aluminum of
the appropriate thickness (usually 0.5 mm) can be
inserted between the port of the tube head and the PID.
Several manufacturers have introduced x-ray units in
which the traditional aluminum filter is replaced with
samarium, a rare-earth metal.
Total filtration is the sum of the inherent and added filtration expressed in millimeters of aluminum equivalent.
Beam filtration must comply with state and federal laws.
Present safety standards require an equivalent of 1.5 mm
aluminum for x-ray machines operating in ranges below
70 kVp and a minimum of 2.5 mm aluminum for
machines operating at or above 70 kVp.
• Collimation controls the size and shape of the useful
beam.
Collimation of the beam is accomplished by using a lead
diaphragm or washer. The lead diaphragm collimator is
placed in the path of the primary beam as it exits the tube
housing at the port (Figure 6-3). Rectangular collimation
may also be achieved through the use of external collimators
that attach to the PID (Figure 6-4.) The function of the
passage of the beam through a sheet of material called a
filter (Figure 6-1). A filter is an absorbing material (usually aluminum) placed in the path of the x-ray beam to
remove a high percentage of the soft x-rays (the longer
wavelengths) and reduce patient radiation dose.
In the dental x-ray machine, these aluminum filter
disks vary in thickness. The half-value layer (HVL) of
an x-ray beam is the thickness (measured in millimeters)
of aluminum that will reduce the intensity of the beam
by one-half. Measuring the HVL determines the penetrating quality of the x-ray beam. The HVL is more accurate than kilovoltage to describe the x-ray beam quality
and penetration. Two similar x-ray machines operating at
the same kilovoltage may not produce x-rays of the same
quality and penetration. The half-value layer is used by
radiological health personnel when determining filtration
requirements.
Filters may be sealed into the tube head or inserted
into the port where the PID attaches. Pure aluminum or
its equivalent will not hinder the passage of high-energy
Tube Collimator Filter
FIGURE 6-1 Collimator and filter. The collimator is a lead washer that restricts the size of the
x-ray beam. The filter is an aluminum disc that filters (removes) the long wavelength x-rays.
Film No filter
Aluminum filter
FIGURE 6-2 Effect of filtration on skin exposure. Aluminum
filters selectively absorb the long wavelength
x-rays.
CHAPTER 6 • RADIATION PROTECTION 63
Collimator
(lead washer)
restricts size of
primary beam
Size of
primary beam
using collimation
Image receptor
FIGURE 6-3 Effect of collimation on
primary beam. Lead collimators control
the shape and size of the primary beam.
The beam is limited to the approximate
size of the image receptor.
FIGURE 6-7 Rectangular PIDs restrict the x-ray beam to the
approximate size of a #2 intraoral image receptor. Rectangular PIDs
are available in 8, 12, and 16 inches (20.5, 30, and 41 cm). (Courtesy of
Margraf Dental Manufacturing Inc.)
2.75″
2″
15
8
”
11
4
”
#2 film
FIGURE 6-6 Although circular collimation provides a large
enough area of exposure to adequately cover a size #2 image receptor,
the patient also receives excess radiation not needed for the exposure
of this receptor.
FIGURE 6-4 External collimator attaches to the PID to reduce
the area of radiation exposure.
Collimator PID
2.75″
FIGURE 6-5 The collimator restricts the size of the primary beam
to 2.75 in. (7 cm) at the end of the PID.
collimator is to reduce the size of the x-ray beam and the
amount of scattered radiation. Collimators may have either a
round or a rectangular opening and are matched with a
round or rectangular PID. Federal regulations require that
round opening collimators restrict the x-ray beam to 2.75 in.
(7 cm) at the patient end of the PID (Figure 6-5). Rectangular collimators restrict the beam to the approximate size of
the image receptor. Figure 6-6 shows the excess radiation
the patient receives with a round collimator when exposing a
#2-sized image receptor. Rectangular collimation reduces
patient radiation exposure by up to 70 percent (Figure 6-7).
Collimation also reduces scatter radiation (sometimes
called secondary radiation). Scatter radiation is radiation
that has been deflected from its path by impact during its
passage through matter. In addition to increasing patient
radiation dose, scattered radiation decreases the quality of
the radiographic image through fogging. In summary, the
two important functions of collimation are
PRACTICE POINT
All intraoral techniques require that the end of the PID be
placed as close to the patient’s skin as possible, without
touching, during the exposure. This is necessary to establish the desired target–surface distance. Increasing the distance between the open end of the PID and the patient’s
skin will not establish the desired target–surface distance.
For example, positioning the open end of an 8-in. (20.5-
cm) PID an additional 4 inches (10.2 cm) away from the
patient’s face is not the same as using a 12-in. (30-cm) PID.
See Figure 4-12.
PRACTICE POINT
Pointed, closed-end cones, originally designed to aid in
aiming the x-ray beam at the center of the film packet,
are no longer used (Figure 6-8). Pointed cones cause the
deflection or scattering of x-rays through contact with the
material of the cones. Because these pointed cones were
used for so many years, many still refer to the PID as a
“cone.” The term position indicating device (PID) is more
descriptive of its function of directing the x-rays, rather
than of its shape.
64 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
FIGURE 6-8 Plastic closed-ended, pointed “cones” are no
longer used.
FIGURE 6-9 Round PIDs are available in 16, 12, and 8 inches
(41, 30, and 20.5 cm).
• Fast film and digital image sensors require less radiation
for exposure and are essential for exposure reduction.
In fact, after rectangular collimation, high-speed film is
the most effective equipment for reducing radiation to the
• Reduces the radiation dose to the patient by reducing the
volume of tissue exposed
• Reduces scatter radiation that causes poor contrast of the
radiograph (see Chapter 4)
• The position indicating device (PID) (or beam indicating device [BID] ) is an extension of the tube housing
and is used to direct the primary x-ray beam. The shape
of the PID indicates the shape of the collimator.
Although rectangular collimation reduces patient radiation
exposure by up to 70 percent over a round-collimated
beam, most dental x-ray machines are sold with round
PIDs attached. Rectangular PIDs can be purchased to
replace the round PIDs and reduce patient radiation
exposure (Figure 6-7).
The length of the PID also has an effect on the radiation
dose the patient receives. The length of the PID helps to
establish the desired target-surface distance. Both round
and rectangular PIDs are available in three lengths: 8 in.
(20.5 cm), 12 in. (30 cm), and 16 in. (41 cm).(See Figures 6-7
and 6-9.) The longer the PID (12-in. or 16-in. length), the
less radiation dose to the patient and the better quality radiographic image (see Figure 4-11). With a longer PID, there
is less divergence of the beam, creating a smaller diameter
of exposure (Figure 6-10).
It is important to note that the dental x-ray machine
may appear to have a short PID when it actually may be
long. Some dental x-ray machines feature a recessed PID,
where the tube is recessed back in the tubehead behind the
transformers, therefore creating a longer target–surface
distance (see Figure 3-1).
CHAPTER 6 • RADIATION PROTECTION 65
Source Source
16″
8″
2.75″
FIGURE 6-10 Target-surface distance. The longer the target-surface
distance, the more parallel the x-rays and the less tissue exposed. Note that the
beam size at the patient’s skin entrance is 2.75 in. (7 cm) for both targetsurface distances. It is the exit beam size that increases to expose a larger area
when using the shorter target-surface distance.
FIGURE 6-11 Many image receptor holding devices are available
to fit most situations. The use of a holder prevents asking patients to
put their fingers in the path of the primary beam.
the number of retakes that may result from alignment
errors. These devices also stabilize the image receptor in
the mouth and reduce the possibility of movement and of
film bending that often result when the patient uses a finger to hold the receptor in position.
• The lead apron made of at least 0.25-mm lead or leadequivalent materials is placed over the patient’s abdomen
to protect the reproductive organs and other radiosensitive tissues from potential scatter radiation during radiographic procedures (Figure 6-12). The use of a lead
apron was recommended for protecting patients during
exposure of dental radiographs many years ago when dental
x-ray machine output was less reliable and film speeds
were slower than today’s standards. Using a fast-speed film
or digital image sensor and a dental x-ray machine that is
appropriately collimated and filtered essentially eliminates
the requirement for covering the patient’s abdomen with a
lead apron. The National Council on Radiation Protection
and Measurements has determined that lead aprons do not
significantly reduce doses from intraoral dental exposures.
Nevertheless some states still have laws requiring the use of
a lead apron over the abdominal area, and patients have
come to expect it. Even if it is not legally required, the use
of a lead or lead-equivalent apron is in keeping with the
ALARA concept and remains a prudent if not essential
practice.
Lead and lead-equivalent aprons should be stored flat or
hung unbent. Folding the apron may cause the material
inside to crack. This is most likely to occur when aprons
are repeatedly folded in the same place day after day.
Cracks in the material allow radiation to penetrate and
render the apron less effective.
• Thyroid collar. Lead and lead-equivalent aprons are available with or without an attached thyroid collar (Figure 6-13).
The thyroid collar, when in place around the patient’s
neck, protects the thyroid gland and other radiosensitive
tissues in the neck region during exposure of intraoral
radiographs. Because of the direction of the dental x-ray
patient. Currently, intraoral dental x-ray film is available in
three speed groups, D, E and F. E-speed film, when compared to D-speed film, is twice as fast and therefore
requires only one-half the exposure time. F-speed film can
reduce radiation exposure 20 percent compared to E-speed
film. The American Dental Association and the American
Academy of Oral and Maxillofacial Radiology recommend the use of the fastest speed film currently available.
Digital image sensors can further reduce the amount radiation required to produce a diagnostic image and will be
discussed in Chapter 9.
• Image receptor holding devices that position the film
packet or digital sensor intraorally are recommended. The
use of a film or image receptor holder eliminates having
the patient hold the receptor in the oral cavity with the fingers (Figure 6-11). Unnecessarily exposing the patient’s
fingers is not ethical practice in keeping with ALARA. The
use of image receptor holders with external aiming devices
will assist the operator in aligning the x-ray beam, which
may afford the patient additional protection by reducing
66 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
Adult patient apron
Available with or without thyroid collar
Child patient apron
Available with or without thyroid collar Thyroid collar
Collar available separate from
apron
Radiographer apron
Used to protect
individual assisting
patient during
exposure
Panoramic cape
Full-size, covers front and back
Panoramic cape
Drapes over shoulders
FIGURE 6-12 Lead aprons and
thyroid collars are available in a wide
range of sizes. Aprons are available
with an attached thyroid collar, or the
thyroid collar may be a separate part.
FIGURE 6-13 Patient protected with lead apron with
thyroid collar in place.
PRACTICE POINT
The use of a thyroid collar is contraindicated when exposing
panoramic radiographs using rotational panoramic equipment because the collar or upper part of the apron to which
it is attached may obscure diagnostic information or interfere
with the rotation of the panoramic unit. This is one of the
reasons lead aprons are available without thyroid collars.
Optimum Film Processing
An often-overlooked step in producing diagnostic radiographs
is film processing. Processing errors increase patient radiation
exposure by resulting in retake radiographs. The patient
deserves the attention that must be paid to meticulous processing procedures and careful film handling to produce ideal diagnostic quality radiographs. Darkroom procedures should be
outlined and followed carefully (see Chapter 8).
Careful attention to chemical replenishment and following
the time–temperature method of processing produces radiographs of ideal quality and avoids retakes. There are ethical considerations to proper processing protocols as well.
In the past, it was sometimes observed that an unethical
practitioner would call for overexposing (increasing the
radiation dose to the patient) and underdeveloping the film
in an attempt to save time during certain procedures.
Another unethical practice noted in history has been to let
processing chemicals go too long between replenishment or
solution change. As the processing chemistry weakens, the
resultant images appear less dense (lighter). Unethical practitioners would increase the dose of radiation to compensate
for the weakening processing solutions. It was the patient
who bore the brunt of this practice by enduring the additional radiation burden. Patient protection techniques
should be used at all times to keep radiation exposures as
low as possible (Box 6-1).
Protection Measures for the Radiographer
All measures taken to protect the patient from radiation
also benefit the radiographer (Box 6-2). Specific radiation
protection methods for the radiographer include time,
shielding, and distance. The radiographer should spend a
minimal amount of time, protected by shielding, at the
greatest distance from the source of radiation to avoid
unnecessary exposure.
beam in this region, lead or lead-equivalent thyroid collars
are recommended for all patients, and especially for children and pregnant females and women of child-bearing
age. (This topic is discussed further in Chapter 27.)
CHAPTER 6 • RADIATION PROTECTION 67
BOX 6-1 Summary of Protection Methods for
the Patient
• Evidence-based prescribing
• Communication
• Working knowledge of quality radiographs
• Education
• Selection of technique
• Posted exposure factors
• Filtration
• Collimation
• Open-ended, 16-in. (41-cm) rectangular PID
• F-speed film/digital image receptors
• Image receptor holders
• Lead/lead-equivalent thyroid collar/apron
• Darkroom protocol
BOX 6-2 Summary of Methods to Protect the
Radiographer
• Follow all patient protection measures.
• Do not contact the tubehead during exposure.
• Avoid retakes.
• Do not hold the image receptor for the patient.
• Use a protective barrier/shield.
• Use leaded protective clothing when necessary.
• Remain 6 ft (1.82 m) away and at a 45° angle from the exiting
primary beam.
• Use radiation monitoring.
Time
When careful attention is focused on producing the highest quality radiographs, the need for retake radiographs is decreased,
which in turn decreases the time the radiographer spends near the
x-ray machine. Additionally, the dental radiographer should
avoid the pitfalls that may lure movement into the path of the primary beam. For example, a drifting tube head should never be
held during the exposure. Radiation leakage from the tube head
can expose the operator to a significant amount of radiation. If
the tube head drifts, it should be serviced to stabilize it.
If a patient must be stabilized during the procedure, as is
sometimes the case with a small child, a parent or guardian
may have to be asked to assist with the procedure. The parent
or guardian should be protected with lead, or lead-equivalent
barriers such as an apron or gloves, when they will be in the
path of the x-ray beam. The radiographer must never place
him/herself in the primary beam.
Image receptor holding devices should be used to stabilize
the receptor in the patient’s oral cavity. If placement with an
image receptor holding device is difficult to achieve, as is the
case with a patient with a small mouth, low and/or sensitive
palatal vault, or an exaggerated gag reflex, the radiographer
should experiment with other holders, smaller-sized films, or
the bisecting technique. The radiographer must not hold the
image receptor in the patient’s mouth. Additionally, another
member of the oral health care team must not be allowed to
place themselves in the path of the primary beam while the
radiographer presses the exposure button.
Shielding
Structural shielding provides the radiographer with protection
from potential scattered radiation. Safe installation of dental
x-ray machines will provide an exposure button permanently
mounted behind a protective barrier, providing protection for
the operator (see Figure 3-4). Most oral health care practices
are located in buildings that have incorporated adequate
shielding in walls such as these regularly used construction
materials: plaster, cinderblock, to 3 inches of drywall,
3/16 inch steel, or 1 millimeter of lead. Additionally, leadlined walls or windows, thick or specially constructed partitions between the rooms, or specially constructed lead screens
offer excellent protection for the operator during exposure
(see Figure 3-7.)
Distance
If a protective barrier is not present, as may be the case in an
open-bay designed practice setting, distance plays an important
role in safeguarding the radiographer during patient exposures.
The operator should always stand as far away as practical—at
least 6 ft (1.8 m)—from the head of the patient (the source of
scatter radiation) while making the exposure. The intensity of
the x-radiation diminishes the farther the x-rays travel
(Figure 6-14). In addition to distance, it is important to remain
in a position 45 degrees to the primary x-ray beam as it exits the
patient, as this is the area of minimum scatter when the patient
is seated upright. Maximum scatter is most likely to occur back
in the direction of the tube head. (Figure 6-15). If exposing
radiographs while the patient is in a supine position (lying
prone in the dental chair), the radiographer should take a position
at an angle of 135 to 180 degrees behind the patient’s head
where the least scatter radiation occurs.
All persons, whether other oral health care team members
or other patients not directly involved with the x-ray exposure,
must be protected by shielding and/or distance.
Radiation Monitoring
The only way to be sure that x-ray equipment is not emitting
too much radiation and that operators are not receiving more
than the maximum permissible dose is to use radiation measuring
devices to monitor equipment and personnel. In radiography,
monitoring is defined as periodic or continuing measurement
to determine the exposure rate in a given area or the dose
received by an operator.
Area Monitoring
Area monitoring involves making an on-site survey to measure
the output of the dental x-ray unit, to check for possible high-level
radiation areas in the operatory, and to determine if any radiation
is passing through walls. Special equipment is needed to detect
the exact amount of ionizing radiation at any given area. Numerous companies specialize in area monitoring. In some regions,
this service may be performed by qualified state inspectors.
21
/2
68 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
45° 45°
90° 90°
Radiographer Radiographer
6 feet
(1.83 meters)
6 feet
(1.83 meters)
Minimum scatter
Maximum scatter Maximum scatter
Minimum scatter
Exiting
beam
FIGURE 6-15 When structural shielding is not available, the radiographer should stand in a position
at least 6 ft (1.83 m) from the head of the patient at an angle of 45º to the exiting primary beam.
A radiographer standing here
would receive 4 times more
scatter radiation than if the…
…radiographer stood here.
3 feet
(0.9m)
6 feet
(1.83m)
FIGURE 6-14 Distance is an effective means of reducing exposure from scatter
radiation.
CHAPTER 6 • RADIATION PROTECTION 69
FIGURE 6-17 DIS radiation monitor. Sized and shaped similar
to a thumb drive, this device has a clip to allow the radiographer to
wear the monitor while working with ionizing radiation. The device
uses a USB connector to plug into a computer with Internet access.
When logged on to the manufacturer’s Web site, real-time radiation
exposure readings may be downloaded from the device. (Courtesy of
Quantum Products.)
FIGURE 6-16 OSL
radiation monitor worn by
the radiographer to monitor
radiation exposure.
(http:/www.landauerinc.com)
Personnel Monitoring
Personnel monitoring requires oral health care professionals to
wear a radiation monitoring device or dosimeter (Figures 6-16
and 6-17) such as a film badge, TLD, OSL monitor, or DIS
monitor (Table 6-2). For a fee, radiation monitoring companies
provide the measuring devices and services to the oral health care
team. After use, the devices are returned to the company or the
information recorded by the device is transmitted to the company
via the Internet. The company evaluates the information captured
by the device and provides the dental practice with a report
regarding exposure. This report compares the operator’s exposure
reading with the maximum allowable level, and the monitoring
company updates the subscriber’s records to keep the wearer
in full compliance with all federal and state safety regulations.
The reports from a radiation monitoring service provide a reliable
permanent record of accumulated doses of occupational radiation
exposure. The types of personnel monitoring devices currently on
the market are listed in Table 6-2.
The likelihood of dental radiation exposing an oral health care
professional who is following ALARA is so small that only a few
states consider dental radiation monitoring mandatory. Even so,
TABLE 6-2 Types of Personnel Monitoring Devices
TYPE HOW IT WORKS ADVANTAGES LIMITATIONS
Film badge Radiosensitive film in a plastic/metal holder lined
with filters of different materials varying in
thickness. Exposure is determined by “reading”
the processed film electronically.
Film itself provides a
permanent record of
exposures
Reliable technology
Film must be changed
and returned to the
monitoring company
monthly
TLD (thermoluminescent
dosimeter )
Contains crystals, usually lithium fluoride, that
absorb radiation. Crystals are heated after being
exposed, and the energy emitted, in the form of
visible light, is proportional to the amount of
radiation absorbed.
Extremely accurate
One-piece
construction
Badge must be returned
to the monitoring
company every
3 months
OSL monitor
(optically
stimulated
luminescence)
Absorbs radiation similar to TLD, but crystals
release energy during optical stimulation instead
of heat.
Allows multiple readouts for reanalysis
New technology
Badge can only be used
once
DIS monitor
(direct ion
storage)
Uses a miniature ion chamber to absorb radiation.
Exposure is determined through digital
processing.
Instant real-time unlimited readouts
New technology
Requires on-site reader
or computer connection to the Internet
more and more oral health care professionals are deciding to
secure monitoring devices and services for themselves and their
employees, even when not mandated by law. As a risk management tool, monitoring radiation exposure—or more likely, documenting the lack of exposure—helps to determine whether the
operator is maintaining radiation safety protocols; aids in providing the radiographer with peace of mind; and assists with risk management by providing a health record of exposure, or more likely,
the lack of exposure, for personnel.
Although personnel monitoring devices play a valuable
role, it should be noted that they are limited in their ability to be
precise at estimating very low levels of exposure. Advancing
technology in this area continue to improve the ability of
70 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
dosimeters to estimate low-dose exposures. Monitors that have
been approved by the National Voluntary Laboratory Accreditation Program (NVLAP) can be expected to be accurate.
It should be noted that personnel monitoring devices do not
“protect” the wearer from radiation.
Organizations Responsible for
Recommending/Setting Exposure Limits
As early as 1902, studies were undertaken to determine the effect
of radiation exposure on the body and to consider setting limits on
radiation exposure. The International Commission on Radiological Protection (ICRP) was formed in 1928, and in 1929 the
National Council on Radiation Protection and Measurements
(NCRP) was created in the United States. The ICRP and the
NCRP do not actually set the laws governing the use of ionizing
radiation, but their suggestions and recommendations are so
highly regarded that most all regulatory bodies use recommendations from these organizations to formulate legislation controlling
the use of radiation. The American Dental Association (ADA) and
its various committees and affiliated organizations, such as the
American Academy of Oral and Maxillofacial Radiology
(AAOMR), work closely with all organizations to ensure that oral
health care patients receive state-of-the-art treatment in radiation
safety (Table 6-3).
Maximum Permissible Dose (MPD)
The United States Nuclear Regulatory Commission has developed radiation protection guidelines referred to as the
maximum permissible dose (MPD) for the protection of radiation workers and the general public (Table 6-4). Maximum permissible dose is defined as the dose equivalent of ionizing
radiation that, in the light of present knowledge, is not expected to
cause detectable body damage to average persons at any time during their lifetime. These limits do not apply to medical or dental
radiation used for diagnostic or therapeutic purposes. Over the
years, the acceptable limits have been constantly revised downward; they are now about 700 times smaller than those originally
proposed in 1902, mainly because many aspects of tissue damage
from radiation are still not clearly understood.
Maximum limits are set higher for workers than for the
public, but the suggested limits of the maximum permissible
accumulated dose for both groups are purposely set far lower
than it is believed the human body can safely accept.
• Radiation workers. The maximum permissible dose
(MPD) for oral health care professionals is the same as for
other radiation workers. According to these guidelines,
the whole-body dose may not exceed 50 mSv (5 rem) per
year. There is no established weekly limit, but state public
health personnel usually use a weekly dose of 1.0 mSv
(0.1 rem) when inspecting dental offices.
The 50 mSv (5 rem) yearly limit for radiation workers
has two very important exceptions. It does not apply to persons under 18 years or to any female members of the oral
health care team who are known to be pregnant. Persons
under 18 years are classified as part of the general public
and can accumulate only 5 mSv (0.5 rem) per year. In the
case of pregnant women, it is recommended that exposure
to the fetus be limited to 5 mSv (0.5 rem), not to be received
at a rate greater than 0.5 mSv (0.05 rem) per month.
• General public. The general public is permitted 5 mSv
(0.5 rem) per year, or one-tenth the dose permitted radiation workers. It should be noted that the MPD has been
established for incidental or accidental exposures and
does not include doses from medical and dental diagnostic or therapeutic radiation. Necessary medical and dental
diagnostic or therapeutic radiation is not counted in the
permissible dose limits. If a patient needs radiographic
services, then that patient needs the radiographic services. An oral health care team member who requires
medical, dental diagnostic, or therapeutic radiation would
become the “patient,” and then the general public MPD
would apply.
TABLE 6-3 Radiation Protection Organizations
ORGANIZATION WEB SITE
International Commission on Radiological Units and Measurements (ICRU) www.icru.org
International Commission on Radiological Protection (ICRP) www.icrp.org
National Council on Radiation Protection and Measurements (NCRP) www.ncrp.com
U.S. Nuclear Regulatory Commission (NRC) www.nrc.gov
U.S. Environmental Protection Agency (EPA) www.epa.gov
U.S. Food and Drug Administration (FDA) www.fda.gov
U.S. Occupational Safety and Health Administration (OSHA) www.osha.gov
American Academy of Oral and Maxillofacial Radiology (AAOMR) www.aaomr.org
American Dental Association (ADA) www.ada.org
CHAPTER 6 • RADIATION PROTECTION 71
The most important step in keeping the patient’s exposure
to a minimum is the use of evidence-based selection criteria to
assess patients for radiographic need.
The technical ability of the radiographer will aid in preventing
unnecessary radiation exposure to the patient. Technical ability
includes communication, working knowledge of quality radiographs, and education. Technique standards, including the choice
of paralleling or bisecting technique, and the selection of exposure
factors also aid in preventing unnecessary radiation exposure.
Equipment standards that play important roles in reducing patient
radiation dose include filtration, collimation, and PID length.
Filtration is the absorption of long wavelength, less penetrating x-rays from the x-ray beam by passage through a sheet of
material called a filter. The half-value layer (HVL) of an x-ray
beam is the thickness (measured in millimeters) of aluminum that
will reduce the intensity of the beam by one-half. Present safety
standards require an equivalent of 1.5 mm aluminum filtration for
dental x-ray machines operating in ranges below 70 kVp and a
minimum of 2.5 mm aluminum for machines operating at or above
70 kVp. Total filtration is the sum of inherent and added filtration.
Collimation is the control of the size and shape of the useful
beam. Federal regulations require that round opening collimators
restrict the x-ray beam to 2.75 in. (7 cm) at the patient end of the
PID. Rectangular collimation reduces patient radiation dose by
70 percent over round collimation. Collimation reduces scattered
radiation that contributes to poor contrast of radiographic images.
The position indicating device (PID) is an extension of
the tube housing and is used to direct the primary x-ray
beam. The length of the PID helps to establish the desired
target–surface distance; the longer the PID, the less radiation
dose to the patient. PIDs have either a round or rectangular
shape and are available in lengths of 8 in. (20.5 cm), 12 in.
(30 cm), and 16 in. (41 cm).
Fast film requires less radiation for exposure. Film speed
groups D, E, or F are currently available for use in dental radiography. Film speed F reduces patient radiation exposure by 20 percent
over film speed E. Film speed E reduces patient radiation exposure
by 50 percent over film speed D. The use of digital image receptors
can further reduce the radiation dose to the patient.
The use of image receptor holders eliminates using the
patient’s fingers to stabilize the receptor intraorally, avoiding
unnecessary radiation exposure to the patient’s fingers.
A lead or lead-equivalent thyroid collar with apron should
be placed on all patients during intraoral x-ray exposures. The
thyroid collar is most important in protecting children and
pregnant women and women of child-bearing age.
Optimum film processing using time-temperature techniques in an adequately equipped darkroom will help avoid
retakes that lead to an increase in patient radiation exposure.
To reduce the chance of operator exposure, time spent near
the source of radiation should be reduced; structural shielding
employed; or the operator should be in a position at least 6 feet
away from the source of radiation at a 45 degree angle to the exiting primary beam.
Area and personnel radiation monitoring can be used to
measure radiation exposures. The International Commission on
Radiological Protection (ICRP) and the National Council on
Guidelines for Maintaining Safe Radiation
Levels
Radiation Safety Legislation
The Tenth Amendment gives the states the constitutional
authority to regulate health. Because many federal agencies are
involved in the development and use of atomic energy, the
federal government has preempted the control of radiation.
Certain provisions of the Constitution and Public Law 86-373
have enabled the states to assume this preempted power and
pass laws that spell out radiation safety measures to protect the
patient, the operator, or anyone (the general public) near the
source of radiation. In fact, even counties and cities have passed
ordinances to protect their citizens from radiation hazards.
Most states and a few localities require periodic inspection or
monitoring of the equipment and its surroundings.
The entry of the federal government into the regulation of
x-ray machines began in 1968 with the enactment of the Radiation Control for Health and Safety Act, which standardized the
performance of x-ray equipment. Subsequently, the ConsumerPatient Radiation Health and Safety Act of 1981 was passed,
requiring the various states to develop minimum standards for
operators of dental x-ray equipment. Several states responded to
this by enacting educational requirements for the certification of
individuals who place and expose dental radiographs.
Because the laws concerning radiation control vary from
state to state, individuals working with x-rays must be familiar
with the regulations governing the use of ionizing radiation in
their locale. Regardless of laws, failure to observe safety protocol cannot be justified ethically.
REVIEW—Chapter summary
Oral health care professionals have an ethical responsibility to
adopt the ALARA concept—as low as reasonably achievable—
which implies that any dose that can be reduced without major
difficulty, great expense, or inconvenience should be reduced or
eliminated.
TABLE 6-4 U.S. Nuclear Regulatory
Commission Occupational Dose Limits
TISSUE ANNUAL DOSE LIMIT
Whole body 50 mSv (5 rem)
Any organ 500 mSv (50 rem)
Skin 500 mSv (50 rem)
Extremity 500 mSv (50 rem)
Lens of eye 150 mSv (15 rem)
U.S. Nuclear Regulatory Commission. (2007, December
4). Standards for protection against radiation, Title 10,
Part 20, of the Code of Federal Regulations. Retrieved
April 11, 2010, from http://www.nrc.gov/reading-rm/
doc-collections/cfr/part020/part020-1201.html
72 BIOLOGICAL EFFECTS OF RADIATION AND RADIATION PROTECTION
7. Which of the following exposes the patient to less
radiation?
a. 8 in. (20.5 cm) round PID
b. 12 in. (30 cm) round PID
c. 16 in. (41 cm) round PID
d. 16 in. (41 cm) rectangular PID
8. Which of the following contributes the most to reducing
patient radiation exposure?
a. D speed film
b. E speed film
c. F speed film
9. During dental x-ray exposure, the lead/lead-equivalent
thyroid collar with apron should be placed on
a. children.
b. females.
c. males.
d. all patients.
10. Each of the following aids in reducing patient radiation exposure EXCEPT one. Which one is the
EXCEPTION?
a. Slow-speed film
b. Careful film handling
c. Darkroom protocol
d. Image receptor holders
11. If a protective barrier is not present, what is the recommended minimum distance that the operator should
stand from the source of the radiation?
a. 3 ft (0.91 m)
b. 6 ft (1.83 m)
c. 9 ft (2.74m)
d. 12 ft (3.66m)
12. Film badges, TLDs, and OSL and DIS monitors are
used to
a. protect the operator from unnecessary radiation exposure.
b. reduce the radiation exposure received by the
patient.
c. monitor radiation exposure the dental radiographer
may incur.
d. record an on-site survey of the radiation output of the
x-ray unit.
13. The annual maximum permissible whole-body dose for
oral health care personnel is
a. 0.5 mSv.
b. 5.0 mSv.
c. 50 mSv.
d. 500 mSv.
14. The annual maximum permissible whole-body dose for
the general public is
a. 0.5 mSv.
b. 5.0 mSv.
c. 50 mSv.
d. 500 mSv.
Radiation Protection and Measurements (NCRP) recommend
dose limits. Federal, state, and local agencies set regulations
governing exposure. The American Dental Association and the
American Academy of Oral and Maxillofacial Radiology work
closely with all agencies responsible for radiation safety.
The maximum permissible dose (MPD) is 50 mSv (5 rem)
per year for radiation workers and 5 mSv (0.5 rem) for the general public, radiation workers who are pregnant, and children
under 18 years of age.
RECALL—Study questions
1. Who has an ethical responsibility to adopt ALARA?
a. The dental assistant
b. The dental hygienist
c. The dentist
d. All of the above
2. Based on the selection criteria guidelines, what is the
radiographic recommendation for bitewing radiographs on an adult recall patient with no clinical
caries and no high-risk factors for caries?
a. Every 6–12 months
b. Every 12–18 months
c. Every 18–24 months
d. Every 24–36 months
3. Communication, working knowledge of a quality radiographic image, and education all aid in protecting the
patient against unnecessary radiation exposure by
a. using lower exposure factors.
b. reducing the risk of retake radiographs.
c. collimating and filtering the primary beam.
d. creating a longer target–surface distance.
4. What is the minimum total filtration that is required by
an x-ray machine that can operate in ranges above 70
kVp?
a. 1.5 mm of aluminum equivalent
b. 1.5 mm of lead equivalent
c. 2.5 mm of aluminum equivalent
d. 2.5 mm of lead equivalent
5. What is the federally mandated size of the diameter of
the primary beam at the end of the PID (at the skin of
the patient’s face)?
a. 1.75 in. (4.5 cm)
b. 2.75 in. (7 cm)
c. 3.75 in. (10 cm)
d. 4.75 in. (12 cm)
6. Radiation protection from secondary radiation may be
increased by the use of an aluminum filter and a lead
collimator because the filter regulates the size of the
tissue area that is exposed and the collimator prevents
low-energy radiation from reaching the tissue.
a. Both statement and reason are correct.
b. Both statement and reason are NOT correct.
c. The statement is correct, but the reason is NOT correct.
d. The statement is NOT correct, but the reason is correct.
CHAPTER 6 • RADIATION PROTECTION 73
15. List three radiation protection organizations.
a. ______________
b. ______________
c. ______________
REFLECT—Case Study
Use the selection criteria guidelines to make a preliminary recommendation and/or to explain to the patient why the dentist
has prescribed or has not prescribed radiographs. Consider the
following three cases:
1. A 17-year-old patient presents with a healthy oral
assessment. No active caries were clinically detected.
No periodontal pockets were noted. His record indicates that his last radiographs were bitewings taken
6 months ago. Based on the evidence-based selection
criteria guidelines, what would be the most likely recommendation for radiographs for this patient?
2. A 25-year-old female recall patient presents for her
6-month check-up. Although her homecare is good, Class
II (multisurface) restorations are present on several
molars and premolars. Her last radiographs were bitewings taken 3 years ago. Based on the evidence-based
selection criteria guidelines, what would be the most
likely recommendation for radiographs for this patient?
3. A 45-year-old male patient, new to your practice, presents with a moderate periodontal condition and evidence of generalized dental disease. He reveals that he
has not had professional oral care in several years, but is
here today to begin to “take care of his teeth.” Based on
the evidence-based selection criteria guidelines, what
would be the most likely recommendation for radiographs for this patient?
RELATE—Laboratory application
Using Box 6-1, Summary of Protection Methods for the Patient,
and Box 6-2, Summary of Methods to Protect the Radiogragher, as
a guide, perform an inventory of your facility. Make a list of all the
radiation protection methods used at your facility. Compare and
contrast these with the safety protocols you learned in this chapter.
Begin with the first patient radiation protection method
listed in Box 6-1, evidence-based prescribing. Investigate how
the dentist at your facility determines who will need radiographs. What guidelines do the dental hygienist and the dental
assistant use to help them in explaining the need for necessary
radiographs to the patient? Does your facility use guidelines
similar to the evidence-based guidelines you learned about in
this chapter? Describe them. Compare and contrast the methods
your facility uses to determine radiographic need to the guidelines you learned about in this chapter. Is your facility meeting
or exceeeding this safety method for reducing patient radiation
dose? If not, what is the rationale for not meeting this standard?
Proceed to the next item on the list in Box 6-1, Communication. Observe the communication between the oral health
care professionals at your facility prior to, during, and following
patient x-ray exposure. What are some examples of dialogue
that contributed to aiding in the protection of patients from
unnecessary radiation exposure? Was there any communication
that you think could have been added? Again, compare and
contrast the communication standards the professionals at your
facility use to decrease the likelihood of unnecessary radiation
exposure using the guidelines you learned about in this chapter.
Is your facility meeting or exceeeding this safety method for
reducing patient radiation dose? If not, what is the rationale for
not meeting this standard?
Proceed through the list of items in Box 6-1 and Box 6-2.
Use observation and interviewing techniques to thoroughly
investigate how each of these items is applied at your facility.
Based on what you learned in this chapter, determine whether
your facility is adequately applying all possible methods of
reducing radiation exposure to patients and radiographers.
REFERENCES
American Dental Association Council on Scientific Affairs.
(2001). An update on radiographic practices: Information
and recommendations. Journal of the American Dental
Association, 132, 234–238.
American Dental Association Council on Scientific Affairs.
(2006). The use of dental radiographs: Update and recommendations. Journal of the American Dental Association,
137, 1304–1312.
Carestream Health, Inc. (2007). Kodak Dental Systems: Radiation safety in dental radiography. Pub. N-414. Rochester,
NY: Author.
Health Canada. (2008). Environmental and work place health.
Technology comparison. HC Pub.: 4429. :Author.
International Commission on Radiological Protection. (1991).
1990 recommendations of ICRP. Publication 60. Stockholm: Annuals of the ICRP, 21, 1–3.
Kuroyanagi, K., Yoshihiko, H., Hisao, F., & Tadashi, S. (1998).
Distribution of scattered radiation during intraoral radiography with the patient in supine position. Oral Surgery,
Oral Medicine, Oral Pathology, 85(6), 736-741.
National Council on Radiation Protection and Measurements.
(1991). Implementation of the principle of as low as reasonably achievable (ALARA) for medical and dental personnel. NCRP Report No. 107.Washington, DC: NCRP.
National Council on Radiation Protection and Measurements.
(2003). Radiation protection in dentistry. NCRP Report
No. 145.Washington, DC: NCRP.
Public Health Service, Food and Drug Administration, American Dental Association Council on Dental Benefit Program, Council on Dental Practice, Council on Scientific
Affairs. (2004). The selection of patients for dental radiographic examinations. Washington, DC: U.S. Dept. of
Health and Human Services.
Thomson, E. M. (2006). Radiation safety update. Contemporary
Oral Hygiene, 6(3), 10–18.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. List and describe the four parts of an intraoral film.
3. Describe latent image formation.
4. List and describe the four parts of an intraoral film packet.
5. Differentiate between the tube side and the back side of an intraoral film packet.
6. Identify the intraoral film speeds currently available for dental radiographs.
7. Match the intraoral film size with customary usage.
8. Match the type of intraoral projection with radiographic need.
9. Explain the difference between intraoral and extraoral film.
10. List typical extraoral film sizes.
11. Compare and contrast duplicating film with radiographic film.
12. List the seven conditions that fog stored film.
KEY WORDS
Antihalation coating
Bitewing radiograph
Duplicating film
Emulsion
Extraoral film
Film packet
Film speed
Gelatin
Halide
Identification dot
lntensifying screen
Intraoral film
Latent image
Occlusal radiograph
Pedodontic film
Periapical radiograph
Screen film
Silver halide crystals
Solarized emulsion
Tube side
Dental X-ray Film
PART III • DENTAL X-RAY IMAGE
RECEPTORS AND FILM PROCESSING
TECHNIQUES
CHAPTER
7
CHAPTER
OUTLINE
 Objectives 74
 Key Words 74
 Introduction 75
 Composition
of Dental
X-ray Film 75
 Latent Image
Formation 75
 Types of Dental
X-ray Film 76
 Film Storage
and Protection 80
 Review, Recall,
Reflect, Relate 81
 References 82
CHAPTER 7 • DENTAL X-RAY FILM 75
Introduction
Technological advances in digital imaging may one day render
film-based radiography obsolete. Until that day, film remains
a reliable method for acquiring diagnostic images to assess
oral health and plan treatment for oral disease. Because radiation’s interaction with film is what allows for the use of
x-rays in preventive oral health care, the dental assistant and
dental hygienist should possess a working knowledge of how
radiographic film records an image. Additionally, determining
how film can best be used to provide the greatest amount of
diagnostic information while exposing the patient to the least
amount of radiation possible is key to radiation safety. The
purpose of this chapter is to explain film composition,
introduce film category types, and discuss film protection
and storage to aid the dental assistant and dental hygienist
in making appropriate decisions regarding film use and
handling.
Composition of Dental X-ray Film
The film used in dental radiography is photographic film that
has been especially adapted in size, emulsion, speed, and packaging for dental uses. Figure 7-1 illustrates the composition of
dental x-ray film.
Film Base
The purpose of the film base is to provide support for the fragile
emulsion and to provide strength for handling. Films used in
dental radiography have a thin, flexible, clear, or blue-tinted
polyester base. The blue tint enhances contrast and image quality.
The base is covered with a photographic emulsion on both
sides.
Adhesive
Each emulsion layer is attached to the base by a thin layer of
adhesive.
Emulsion
The emulsion is composed of gelatin in which crystals of silver
halide salts are suspended. The function of the gelatin is to
keep the silver halide crystals evenly suspended over the base.
The gelatin will not dissolve in cold water, but swells, exposing
the silver halide crystals to the chemicals in the developing
solution. The gelatin shrinks as it dries, leaving a smooth surface
that becomes the radiograph.
The silver halide crystals are compounds of a halogen
(either bromine or iodine) with another element. In radiography,
as well as in photography, that element is silver. Dental film emulsion is about 90 to 99 percent silver bromide and 1 to 10 percent
silver iodide. Silver halide crystals are sensitive to radiation. It is
the silver halide crystals that, when exposed to x-rays, retain the
latent image.
Protective Layer
The supercoating of gelatin to protect the emulsion from
scratching and rough handling that covers the emulsion layers
is called the protective layer.
Latent Image Formation
During radiation exposure x-rays strike and ionize some, but
not all, of the silver halide crystals, resulting in the formation
of a latent (invisible) image. Not all the radiation penetrating
the patient’s tissue will reach the film emulsion. For example,
metal restorations such as amalgam or crowns will absorb
the x-ray energy and stop the radiation from reaching the
film. It should be noted that varying amounts of radiation
will reach the film. The varying thicknesses of the objects in
the path of the beam will allow more or less radiation to pass
through and reach the film emulsion. For example, enamel
and bone will absorb, or stop, more x-rays from reaching the
film than the less dense structures such as the dentin or pulp
chambers of the teeth. When radiation does reach the emulsion, the silver halide crystals are ionized, or separated into
silver and bromide and iodide ions that store this energy as a
latent image. These energy centers store the invisible image
pattern until the processing procedure produces a visual
image (see Chapter 8).
During the developing stage of the processing procedure,
the exposed silver halide crystals—which have stored a latent
image—are changed into black specks of silver, resulting in the
black or radiolucent areas observed on a dental radiograph.
The amount of black silver specks varies depending on the
structures radiographed and whether or not those structures
allowed the x-rays to pass through and reach the film
emulsion. The less dense or thin structures permit the passage
of x-rays; thick, dense structures will not. These dense
structures will appear clear/white or radiopaque on the
radiograph as a result of the fixer step during film processing
(see Chapter 8).
Film base
Protective coating
Adhesive
Adhesive
Protective coating
Silver halide
crystals
Emulsion
Gelatin
FIGURE 7-1 Schematic cross-section drawing of
dental x-ray film. The rigid but flexible film base is coated
on both sides with an emulsion consisting of silver halide
(bromide and iodide) crystals embedded in gelatin. Each
emulsion layer is attached to the base by a thin layer of
adhesive. The emulsion layers are covered by a supercoating of
gelatin to protect the emulsion from scratching and handling.
76 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
Identification dot
on tube side of
film packet
Intraoral film
Outer package
wrapping
Lead foil
Black paper
film wrapper
FIGURE 7-4 Cross-section of a film packet.
Types of Dental X-ray Film
Depending on where the film is to be used—inside or outside
the mouth—the film is classified as intraoral or extraoral.
Intraoral Films
Intraoral films are designed for use inside the oral cavity.
The use of an intraoral film outside the oral cavity is contraindicated because of the increased dose of radiation needed
to produce an acceptable radiographic density.
FILM PACKET The film manufacturer cuts the films to the
sizes required in dentistry. Small films suitable for intraoral
(inside the mouth) radiography are made into what is called a
film packet. The terms film packet and film are often used
interchangeably. Figure 7-2 shows the front or tube side and
the back side of an intraoral film packet.
All intraoral film packets are assembled similarly. The film
is first surrounded by black, light-protective paper. Next, a thin
sheet of lead foil to shield the film from backscatter radiation is
placed on the side of the film that will be away from the radiation source. An outer wrapping of moisture-resistant paper or
plastic completes the assembly (Figures 7-3 and 7-4).
The film packet consists of:
1. Film
2. Black paper wrapping
3. Lead foil
4. Moisture-resistant outer wrapping
FIGURE 7-2 Intraoral film packets showing the front or
tube side (white, unprinted side of the film packet) (top) and the
back side (color-coded side) of the film packet (bottom).
1
2
3
2
4
1
FIGURE 7-3 Back of an open film packet. (1)
Moisture-resistant outer wrap. (2) Black paper. (3) Film.
(4) Lead foil backing.
CHAPTER 7 • DENTAL X-RAY FILM 77
PRACTICE POINT
The patient has a right to access their dental records, including radiographs. The use of double film packets produces
two original radiographs, allowing the practice to keep one
as part of the patient’s permanent record and provides a
ready copy to give to the patient when requested.
A small raised identification dot is located in one corner
of the film. The raised dot is used to determine film orientation
and is used to distinguish between radiographs of the patient’s
right and left sides (see Chapter 21).
• Black paper wrapping surrounds the film inside the
packet to protect it from light.
• Lead foil. A sheet of lead foil is located in the back of the
film packet, behind the film. The purpose of the lead foil
backing is to absorb scattered radiation. Scattered x-rays
strike the film emulsion from the back side of the film (the
side away from the tube), fogging or reducing the clarity of
the image. The lead foil is embossed with a pattern that
becomes visible on the developed radiograph in the event
that the packet is accidentally positioned backward during
the exposure.
• Moisture-resistant outer wrapping consisting of paper or
soft vinyl plastic holds the packet contents and protects the
film from light and moisture. This wrapping is either
smooth or slightly pebbly to prevent slippage. Each film
packet has two sides, a front side or tube side that faces the
tube (radiation source) and a back side that faces away
from the source of radiation (Figure 7-2).
• Tube side. The tube side is usually solid white. A small
embossed dot is evident near one of the film packet corners. The embossed dot will be used later to aid in identifying the image as either the patient’s right or left side;
however, it is important to know which corner it is
located on during the film placement step.
In intraoral radiography, the tube side of the film faces the
source of radiation. When placing the film intraorally, the tube
side will face the lingual surfaces of the teeth of interest.
• Film. Film packets contain one or two films. When a packet
containing two radiographic films is exposed, a duplicate
radiograph results at no additional radiation exposure to the
patient. One radiograph must be kept as part of the patient
record. The copy can serve as a duplicate radiograph.
Duplicate radiographs may be sent to a specialist for consultation regarding treatment, to another professional as a
referral, to a third-party payer or insurance company as
evidence for needed treatment, to document legal evidence,
or given to the patient who is moving to another location
and will seek treatment at another oral health care facility.
• Back side. The back side containing the tab for opening
the film packet is white or may be color coded (Table 7-1).
To aid in determining which is the front and the back
side of the film packet, the following information is
usually printed on the back side:
• Manufacturer’s name
• Film speed
• Number of films in the packet (one or two)
• Circle or mark indicating the location of the identifying dot
• The statement “Opposite side toward tube”
TABLE 7-1 Kodak Film Packet Color Codes
ONE-FILM
PACKET
TWO-FILM
PACKET
Ultra-speed (D) Green Gray
Insight (F) Lavender Tan
PRACTICE POINT
During intraoral film packet placement, the embossed dot
should be positioned away from the area of interest. Usually,
when taking periapical radiographs, the area of interest is
the apices of the teeth; therefore, the embossed dot should
be positioned toward the occlusal. To assist with positioning
the embossed dot out of the way, intraoral film manufacturers have packaged film so that the embossed dot can be
observed on the outer moisture-resistant wrapping.
FILM PACKAGING Intraoral film packets are packaged in
cardboard boxes or plastic trays. Depending on the size, intraoral films are packaged 25, 50, 130, or 150 to a box, the most
popular being the 130- or 150-film packages. A layer of protective foil surrounds the films inside the container to protect
against damage while being stored.
FILM EMULSION SPEEDS (SENSITIVITY) Speed refers to the
amount of radiation required to produce a radiograph of acceptable density. The faster the film speed, the less radiation
required to produce a radiograph of acceptable density. Factors
that determine film speed are
• Size of silver halide crystals. The larger the crystals, the
faster the film speed.
• Thickness of emulsion. Emulsion is coated on both
sides of the film base to increase film speed. The thicker
the emulsion, the faster the film speed.
• Special radiosensitive dyes. Manufacturers add special
dyes that help to increase the film speed.
78 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
• Size No. 3. The extra-long #3 film is called a long bitewing
film. These films usually come with a preattached bite tab.
• Size No. 4. The #4 film is the largest of the intraoral films.
Size #4 films are generally referred to as occlusal films.
TYPES OF PROJECTIONS These five film sizes are used to
expose three types of intraoral film projections: bitewing,
periapical, and occlusal.
• Bitewing radiographs(Figure 7-6) image the coronal portions
of both the maxillary (upper) and mandibular (lower) teeth
and crestal bone on the same film. Bitewing radiographs are
used to examine the surfaces of the crowns of the teeth that
touch each other and are particularly valuable in determining
the extent of proximal caries. Bitewing radiographs image a
portion of the alveolar bone crests, and vertical bitewing radiographs (see Chapter 16) provide added information regarding
the supporting periodontia. Both vertical and horizontal bitewing
radiographs may be exposed using film sizes #0, #1, or #2. Film
size #3 is especially designed to expose horizontal bitewing radiographs. Bitewing film sizes, especially the size #3 film packet,
may be purchased with an attached flap or tab on which the
patient must bite to hold the film packet in place between the
occlusal surfaces of the maxillary and mandibular teeth.
• Periapical radiographs (Figure 7-7) (from the Greek word
peri, for around and the Latin word apex for the root tip) are
used to record a detailed examination of the entire tooth,
from crown to root tip or apex. Periapical radiographs image
the supporting structures of the teeth such as the periodontal
ligament space and the surrounding bone. Periapical radiographs may be exposed using film sizes #0, #1, or #2.
• Occlusal radiographs (see Figure 17-1) image a larger area
than periapical radiographs. These projections are ideal for
recording a large area of the maxilla, mandible, and floor of
the mouth. They can reveal gross pathological lesions, root
fragments, bone and tooth fractures, and impacted or supernumerary teeth and many other conditions. Occlusal radiographs can be used to survey an edentulous (without teeth)
mouth. The size #4 film packet is especially designed as an
occlusal film. Film size #2 may also be used with the
occlusal radiographic technique, especially for young children who may not be able to tolerate the film packet placement necessary for periapical radiographs.
Extraoral Films
Extraoral films are designed for use outside the mouth. These
large films are classified as screen film. Screen film (indirectexposure film) is exposed primarily by a fluorescent type of
light given off by special emulsion-coated intensifying screens
that are positioned between the film and the x-ray source. The
intensity of the fluorescent light emitted by the intensifying
screens permits a significant reduction in the amount of radiation required to produce an image. The image produced on an
extraoral film results from exposure to this fluorescent light,
instead of directly from the x-rays.
Although the thickness of the emulsion and the addition of
radiosensitive dyes aid in increasing film speed (film sensitivity), the most important factor in increasing film speed is the
size of the silver halide crystals in the emulsion. The larger the
crystals, the faster the film speed, resulting in less radiation
exposure to produce an acceptable image. However, image
sharpness is more distinct when the crystals are small. The
larger crystals used in high-speed (fast) film result in a certain
amount of graininess that reduces the sharpness of the radiographic image. It has been determined that this slight loss of
image sharpness does not interfere with diagnosis and is tolerated because of the reduction in patient radiation exposure.
SPEED GROUPS Trademark names like Ultra-speed or
Insight are names assigned by the manufacturer and do not
indicate the actual film speed. The American National Standards Institute (ANSI) groups film speed using letters of the
alphabet: speed group A for the slowest through F for the
fastest. At the present time, F-speed is the fastest film available, and film speeds slower than D are no longer used. In
addition to labeling the film packages, film speed is printed on
the back side of each individual film packet.
Currently only D-speed, E-speed, and F-speed films are
available. Some manufacturers have stopped producing E-speed
film. Both the American Dental Association and the American
Association of Oral and Maxillofacial Radiology recommend
using the fastest speed film currently available to aid in reducing
unnecessary radiation to patients. Although F-speed film requires
less radiation to produce an acceptable image, some practitioners
have not stopped using the slower D-speed film. Faster-speed
films contain a larger crystal size that may contribute to a slight
decrease in image resolution. Some practitioners who are accustomed to viewing D-speed images resist the change. However, it
should be noted that changes in the visual acuity of today’s films
have improved the image of the faster-speed films. Additionally, it
should be noted that studies of film speed comparisons have failed
to indicate that faster-speed films are less diagnostic. The use of
high-speed film has made it possible to reduce patient exposure to
radiation to a fraction of the time formerly deemed necessary.
FILM SIZE There are five sizes of intraoral film: #0, #1, #2,
#3, and #4. The larger the number, the larger the size of the film
(Figure 7-5).
• Size No. 0. The #0 film is especially designed for small
children and is often called pedo (from the Greek word
paidos, child) or pedodontic film.
• Size No. 1. The #1 film may also be used for children.
In adults, the use of the narrow #1 film is normally limited
to exposing radiographs of the anterior teeth. Although
it images only two or three teeth, this film is ideal for
areas where the oral cavity is narrow.
• Size No. 2. The wider #2 film is generally referred to as
the standard film, or PA for periapical film. This film size
is used in probably 75 percent of all intraoral radiography.
The #2 film is commonly used on both larger children,
especially those with a mixed dentition, and adults.
CHAPTER 7 • DENTAL X-RAY FILM 79
No. 0
Size 7/8” x 1 3/8”
(22 mm x 35 mm)
No. 1
Size 15/16” x 1 9/16”
(24 mm x 40 mm)
No. 2
Size 1 1/4” x 1 5/8”
(32 mm x 41 mm)
No. 3
Size 1 1/16” x 2 1/8”
(27 mm x 54 mm)
No. 4
Size 2 1/4” x 3”
(57 mm x 76 mm)
No. 3
Available pretabbed
FIGURE 7-5 Intraoral film sizes. (Courtesy of Dentsply Rinn)
FIGURE 7-6 Bitewing radiograph. FIGURE 7-7 Periapical radiograph.
PACKAGING Larger extraoral films are generally packaged
25, 50, or 100 to a box (Figure 7-8). The films are sometimes
sandwiched between two pieces of protective paper, and the
entire group is wrapped in protective foil. Because these films are
designed for extraoral use with a cassette, discussed in detail in
Chapter 29, they require neither individual lead backing nor
moisture-resistant wrappings.
FILM SIZE Extraoral films vary in size. Different sizes can
accommodate imaging the oral cavity and various regions of
the head and neck. The most common sizes are
• used mainly for lateral views of
the jaw or the temporomandibular joint (TMJ)
• used for cephalometric profiles
and posteroanterior views of the skull
• 5 or (13 or ), used for
panoramic radiographs of the entire dentition
Duplicating Film
When a duplicate radiograph, a copy identical to an original, is
needed, oral health care practices often use two- or double-film
6 in. * 12 in. 15 cm * 30 cm
8 * 10 in. (20 * 26 cm),
5 * 7 in. (13 * 18 cm),
80 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
from radiation. Individual film packets should also be kept in a
shielded area. This is especially important while in the process
of exposing several radiographs at one time, as is the case when
exposing a set of bitewings or full mouth series on a patient.
Once a film has been exposed to radiation, the crystals within
the emulsion increase in their sensitivity. The exposed film
should be placed in a shielded area while the next film is
exposed. All exposed films should be kept safe from radiation
until processing.
Light
Care should be taken when handling intraoral film packets so as
not to tear the outer light-tight wrap. Extraoral cassettes must be
closed tightly to prevent light leaks. Safe lighting in the darkroom must be periodically examined to ensure safe light
conditions (see Chapter 19).
Heat and Humidity
To prevent fogging, film should be stored in a cool, dry place.
Ideally, all unexposed film should be stored at 50°F to 70°F
(10°C–21°C) and 30 to 50 percent relative humidity.
Chemical Fumes
Film should be stored away from the possibility of contamination
by chemical fumes. Film should not be stored in the darkroom
near processing chemicals.
Physical Pressure
Physical pressure and bending can fog film. When storing,
boxes of film must not be stacked so high as to increase the
pressure on the packets. Heavy objects should not be placed
or stored on top of film.
Shelf Life
Dental x-ray film has a limited shelf life. The expiration date
is printed on the film packaging (Figure 7-9). All intraoral
film should be stored so that the expiration date can be readily
seen and the appropriate films used first. Expired film compromises the diagnostic quality of the image and should not
be used.
FIGURE 7-8 Extraoral film packages.
and
size extraoral film packages. (Used with
permission of Eastman Kodak Company.)
8 * 10 in. (20 * 26 cm)
5 * 12-in. (13 * 30 cm), 6 * 12-in (15 * 30 cm),
intraoral packets. However, if an additional copy is needed or a
two-film packet was not used when the original radiograph was
exposed, a duplicating machine with special duplicating film
can be used.
Duplicating film is different than x-ray film and is
exposed by the action of infrared and ultraviolet light rather
than by x-rays. Only one side of the duplicating film is coated
with emulsion. The emulsion side appears dull and lighter
under safe light conditions in the darkroom where it is used.
The nonemulsion side is shiny and appears darker under safe
light conditions. To make a copy of a radiograph, the emulsion
side of the film is placed against the original radiograph with
the nonemulsion side up (see Chapter 28). When the duplicating
film is exposed to ultraviolet light from the duplicating
machine, the solarized emulsion records the copy. Solarized
emulsion is different than x-ray film emulsion in that the
image produced in response to light exposure gets darker with
less light exposure and lighter with more light exposure. The
nonemulsion side contains an antihalation coating. The dye
in the antihalation coating absorbs the ultraviolet light coming
through the film to prevent back-scattered light from reexposing
the film and creating an unsharp image.
Duplicating film, boxed in quantities of 50, 100, or 150
sheets, is available in periapical sizes and in 5 or (13 or
) and sheets.
Film Storage and Protection
All radiographic film is extremely sensitive to radiation, light,
heat, humidity, chemical fumes, and physical pressure. Additionally, film is sensitive to aging, having a shelf life determined by the manufacturer. Precautions for safely storing and
protecting films from these conditions must be followed. Film
fogging is the darkening of the finished radiograph caused by
one or more of these factors.
Radiation
Stray radiation, not intended for primary exposure, can fog film.
Film should be stored in its original packaging in an area shielded
15 * 30 cm 8 * 10 in. (20 * 26 cm)
6 * 12 in.
FIGURE 7-9 Film package showing expiration date.
CHAPTER 7 • DENTAL X-RAY FILM 81
REVIEW—Chapter summary
X-ray film serves as a radiographic image receptor. The film
used in dental radiography is photographic film that has
been especially adapted in size, emulsion, film speed, and
packaging for dental uses. All x-ray film has a polyester
base that is coated with a gelatin emulsion containing silver
halide (bromide and iodide) crystals.
During radiation exposure, the x-rays strike and ionize
some of the silver halide crystals, forming a latent image. The
image does not become visible until the film is processed.
An intraoral film packet consists of film, white-light tight
black paper wrapping, lead foil, and a moisture-resistant outer
wrapping. Intraoral film packets have a white, unprinted front
or tube side. The lead foil and the tab for opening the film
packet are on the back side.
Film speed (sensitivity) refers to the amount of radiation
required to produce a radiograph of acceptable density. Film
speed groups range from A (for the slowest) through F (for the
fastest). Currently only D-, E-, and F-speed films are available
for dental radiographs.
The five intraoral film sizes are #0, #1, #2, #3, and #4. The
three types of intraoral radiographic projections are bitewing,
for imaging proximal tooth surfaces and alveolar bone crests;
periapical, for examining the entire tooth and supporting structures; and occlusal, for surveying larger areas of the maxilla
and the mandible.
Larger extraoral films designed for use outside the mouth
are classified as screen films because fluorescent light from
intensifying screens is used to help the x-rays produce the image.
Extraoral films are used for lateral jaw exposures and cephalometric and panoramic radiographs.
Duplicating film is used in conjunction with a duplicating
machine that emits light to make copies of radiographs. Duplicating film differs from radiographic film in that the solarized
emulsion gets darker with less light exposure and lighter with
more light exposure.
X-ray film is sensitive to radiation, light, heat, humidity,
chemical fumes, physical pressure, and aging. Care must be
exercised in storing and in handling the film before, during, and
after exposure.
RECALL—Study questions
1. Which of these provides support for the fragile film
emulsion?
a. Base
b. Adhesive
c. Silver halide crystals
d. Protective coating
2. Which of these is light and x-ray sensitive?
a. Lead foil
b. Adhesive
c. Gelatin
d. Silver halide crystals
3. During x-ray exposure, crystals within the film emulsion become energized with a(n)
a. visible image.
b. slow image.
c. latent image.
d. intensified image.
4. What is the function of the lead foil in the film packet?
a. Moisture protection
b. Absorb backscatter radiation
c. Give rigidity to the packet
d. Protect against fluorescence
5. Each of the following can be found on the back side of
an intraoral film packet EXCEPT one. Which one is the
EXCEPTION?
a. Film speed
b. Film size
c. Embossed dot location
d. Number of films in packet
6. Which of these films has the greatest sensitivity to
radiation?
a. D-speed
b. E-speed
c. F-speed
7. A size #4 intraoral film packet would most likely be
used to expose a(n)
a. bitewing radiograph.
b. periapical radigraph.
c. occlusal radiograph.
d. pedodontic radiograph.
8. Which of these projections will the dentist most likely
prescribe for evaluation of a specific tooth and its surrounding structures?
a. Bitewing radiograph
b. Periapical radigraph
c. Occlusal radiograph
d. Panoramic radiograph
9. Intensifying screens will
a. reduce exposure time.
b. decrease processing time.
c. increase x-ray intensity.
d. increase image detail.
10. Which of the following is considered to be a screen
film?
a. Occlusal
b. Periapical
c. Bitewing
d. Panoramic
11. Which type of film is used to copy a radiograph?
a. Duplicating film
b. Screen film
c. Nonscreen film
d. X-ray film
82 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
RELATE—Laboratory applicaton
Obtain one each of a size #0, size #1, size #2, size #3, and size
#4 intraoral film packet. Beginning with the size #0 film
packet, consider the following. Repeat with each of the film
sizes. Write out your observations.
1. What is the film speed? How did you get the answer to
this question?
2. What information is written on the outside of the film
packet? Where is this information written: on the front
or back of the film packet?
3. How many films do you expect to find inside this
packet? How did you get the answer to this question?
4. Where is the embossed dot located? How did you find
it? What is this used for?
5. What type of projection (bitewing, periapical, or occlusal)
could be taken with this film size? Explain your answer.
6. What about this film packet’s size makes it ideal; less than
ideal; or not suited for the adult patient? A child patient?
7. For what area(s) of the oral cavity will this film packet
be best suited? Not suited?
8. Now open the film packet. List the four parts of the
packet and explain the purpose of each.
9. Next, hold the film up horizontally (parallel to the floor)
at eye level and observe it from the edge. Can you see
the film base with the emulsion coating on the top and
the bottom?
10. Next, observe the metal foil. What is the reason for the
embossed imprint?
11. When you opened the film packet, did you utilize the
black paper’s tab? The tab plays an important role in
opening a contaminated film packet aseptically. This is
discussed in detail in Chapter 10.
REFERENCE
Carestream Health, Inc. (2007). Kodak Dental Systems:
Exposure and processing for dental film radiography.
Pub. N-414. Rochester, NY.
12. X-ray films should be stored
a. away from heat and humidity.
b. near the source of radiation.
c. in the darkroom.
d. stacked in columns.
REFLECT—Case study
Utilize what you learned in this chapter about the sizes and
types of projections to make a preliminary recommendation
and/or to explain to the patient why the dentist has prescribed: (1) the type of projection; (2) the size of the film;
and/or (3) the number of films to use for each of the following three cases.
1. An adult patient with suspected carious lesions on the
proximal surfaces of posterior teeth. Additionally, this
patient is considered to have a periodontal condition for
which he is under maintenance treatment.
a. The recommended type of projection will most
likely be:
b. The size of the film(s) will most likely be:
c. The number of films to be exposed will most likely be:
2. An adult patient with a toothache in the area of the
maxillary right molar.
a. The recommended type of projection will most
likely be:
b. The size of film(s) will most likely be:
c. The number of films to be exposed will most
likely be:
3. An 8-year-old patient who, while skateboarding,
seems to have suffered a traumatic injury to the anterior teeth.
a. The recommended type of projection will most
likely be:
b. The size of film(s) will most likely be:
c. The number of films to be exposed will most
likely be:
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Explain how a latent image becomes a visible image.
3. List in sequence the steps in processing dental films.
4. List the four chemicals in the developer solution, and explain the function of each
ingredient.
5. List the four chemicals in the fixer solution, and explain the function of each
ingredient.
6. Discuss location, size, and lighting as considerations for setting up a darkroom.
7. Discuss the factors that affect safelighting.
8. Identify equipment needed for manual film processing
9. Demonstrate the steps of manual film processing.
10. Describe the role of rapid (chairside) processing.
11. Identify equipment needed for automatic film processing.
12. Demonstrate the steps of automatic film processing.
13. Compare manual and automatic processing methods stating advantages
and disadvantages of each.
14. Explain the role chemical replenishment and solution changes play in maintaining optimal
processing chemistry.
KEY WORDS
Acetic acid
Acidifier
Activator
Automatic processor
Darkroom
Daylight loader
Developer
Developing agent
Elon
Film feed slot
Film hanger
Film recovery slot
Fixer
Fixing agent
Hardening agent
Hydroquinone
Latent image
LED (light-emitting diode)
CHAPTER
8
CHAPTER
OUTLINE
 Objectives 83
 Key Words 83
 Introduction 84
 Overview of Film
Processing 84
 Film Processing
Solutions 84
 Darkroom 86
 Manual Film
Processing 88
 Rapid (Chairside)
Film Processing 91
 Automatic Film
Processing 91
 Processing
Chemical
Maintenance 93
 Review, Recall,
Reflect, Relate 94
 References 96
Dental X-ray Film
Processing
KEY WORDS (Continued)
84 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
Introduction
Film processing is a series of steps that converts the invisible
latent image on the dental x-ray film into a visible permanent
image called a radiograph. The diagnostic quality of the visible
image depends on strictly adhering to these processing steps.
Film processing may be accomplished either manually or automatically. The purpose of this chapter is to explain the fundamentals of film processing and identify the roles processing
solutions play in producing a visible image. Because most processing is accomplished in a darkroom equipped with special
lights, darkroom design and equipment will be described.
Overview of Film Processing
Processing transforms the latent (hidden) image, which is produced when the x-ray photons are absorbed by the silver halide
crystals in the emulsion, into a visible, stable image by means of
chemicals. The basic steps of processing dental x-ray film are:
1. Developing
2. Rinsing (automatic processors often omit this step)
3. Fixing
4. Washing
5. Drying
Developing
The initial step in the processing sequence is the development of
the film. The role of the developer solution is to reduce the
exposed silver halide crystals within the film emulsion to black
metallic silver. The unexposed silver halide crystals (in those
areas of the film opposite metallic or dense structures that absorb
and prevent the passage of x-rays) are unaffected at this time.
Rinsing
The purpose of the rinsing step is to remove as much of the alkaline developer as possible before placing the film in the fixer
solution. Rinsing preserves the acidity of the fixer and prolongs
its useful life.
Fixing
After brief rinsing, the film is immersed in the fixer solution. The
role of the fixer is to remove the unexposed and/or undeveloped
silver halide crystals from the film emulsion.
Washing
After the film is completely fixed, it is washed in running water
to remove any remaining traces of the chemicals.
Drying
The final step is drying the film for storage as a part of the
patient’s permanent record. Films may be air-dried at room temperature or they may be dried in a heated cabinet especially made
for this purpose.
The processed films are now called radiographs. The
images on the radiograph are made up of microscopic grains of
black metallic silver. The amount of silver deposited will vary
with the thickness of the tissues penetrated. As discussed in
Chapter 4, tissues that are not very dense, such as the pulp
chamber of the tooth, allow more radiation to reach the film
emulsion, resulting in black (radiolucent) areas on the film,
whereas dense structures such as metal restorations will block
the passage of x-rays, resulting in white (radiopaque) areas on
the film. Basically, the developer is responsible for creating
the film’s radiolucent appearance, and the fixer is responsible
for creating the film’s radiopaque appearance.
Film Processing Solutions
Dental x-ray film processing requires the use of developer
and fixer. These chemicals may be obtained in three forms
(Figure 8-1):
FIGURE 8-1 Processing chemicals. Liquid concentrate of
developer and fixer. When mixed with distilled water, each bottle
yields 1 gal (3.8 L) of solution. (Courtesy of Siemens Medical
Systems, Dental Division, Iselin, NJ)
Light-tight
Oxidation
Potassium alum
Potassium bromide
Preservative
Processing
Processing tank
Radiolucent
Radiopaque
Rapid (chairside) processing
Replenisher
Restrainer
Roller transport system
Safelight
Safelight filter
Selective reduction
Silver halide crystals
Sodium carbonate
Sodium sulfite
Sodium thiosulfate
Time–temperature
Viewbox
Wet reading
Working radiograph
CHAPTER 8 • DENTAL X-RAY FILM PROCESSING 85
• Powder
• Liquid concentrate
• Ready-to-use solutions
The powdered and liquid concentrate forms must be
mixed with water prior to using. Chemical manufacturers
usually recommend the use of distilled water when mixing
chemistry to avoid potential problems with other chemicals
that are sometimes present in tap water.
Developer
The main purpose of the developer is to convert the exposed
silver halide crystals into metallic silver grains.
There are four chemicals in the developer (Table 8-1):
1. Developing agents (also called reducing agents)
2. Preservative
3. Activator (also called alkalizer)
4. Restrainer
The developing agent reduces the exposed silver halide crystals
to metallic silver but has no effect on the unexposed crystals at
recommended time–temperatures. This is called selective reduction, meaning that only the nonmetallic elements, the halides, are
removed, and the exposed silver remains (Figure 8-2).
Developer contains two chemicals, hydroquinone and
elon. The hydroquinone works slowly but steadily to build up
density and contrast in the image. The elon works fast to bring
out the gray shades (contrast) of the image. Both chemicals are
affected by extreme temperatures. The higher the temperature,
the less time required to develop the film; therefore, regulating
the temperature of the developer is critical.
The preservative, sodium sulfite, protects the developing
agents by slowing down the rapid oxidation rate of the developer.
The activator, usually sodium carbonate, provides the
necessary alkaline medium required by the developing agents.
It also softens and swells the gelatin, allowing more of the
exposed silver halide crystals to come into contact with the
developing agents.
The restrainer, potassium bromide, restrains the developing agents from developing the unexposed silver halide
crystals and therefore inhibits the tendency of the solution to
fog the film.
Fixer
The fixer plays three roles: (1) stops further film development—
thereby establishing the image permanently on the film; (2)
removes (dissolves) the unexposed/undeveloped silver halide
crystals (those that were not exposed to x-rays); and (3) hardens (fixes) the emulsion.
There are four chemicals in the fixer (Table 8-2):
1. Fixing agent (also called a clearing agent)
2. Preservative
3. Hardening agent
4. Acidifier
The fixing (clearing) agent, ammonium thiosulfate or
sodium thiosulfate, also known as “hypo” or hyposulfate of
sodium, removes all unexposed and any remaining undeveloped
silver halide crystals from the emulsion.
The preservative, sodium sulfite (the same chemical as
used in the developer), slows the rate of oxidation and prevents
the deterioration of the hypo and the precipitation of sulfur.
A
B
C
FIGURE 8-2 Cross section of dental x-ray film emulsion.
(A) X-rays strike silver halide crystals, forming latent image sites
(shown in gray). (B) After development, crystals struck by x-rays
(latent image sites) reduced to black metallic silver. (C) Fixer
removes unexposed, undeveloped crystals, leaving the black
metallic silver.
TABLE 8-1 Composition of Developer
INGREDIENT CHEMICAL ACTION
Developing agents
(reducing agents)
Hydroquinone Reduces (converts) exposed silver halide crystals to black metallic silver.
Slowly builds up black tones and contrast.
Elon Reduces (converts) exposed silver halide crystals to black metallic silver.
Quickly builds up gray tones.
Preservative Sodium sulfite Prevents rapid oxidation of the developing agents.
Activator Sodium carbonate Activates developing agents by providing required alkalinity.
Restrainer Potassium bromide Restrains the developing agents from developing the unexposed silver halide
crystals, which produce film fog.
86 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
The hardening agent, potassium alum, shrinks and hardens the gelatin emulsion. This hardening continues until the film
is dry, thus protecting it from abrasion.
The acidifier, acetic acid, provides the acid medium to stop
further development by neutralizing the alkali of the developer.
Hardening Agents
Special hardening agents are sometimes added to the developer
used in automatic processors to facilitate the transportation of
the films through the roller systems.
Replenisher
Replenisher is a superconcentrated solution of developer or
fixer. Replenisher is added to the developer or fixer in the processing tanks to compensate for the loss of volume and strength
of the solutions due to oxidation and other causes. Processing
solutions lose their potency over time and with use. Adding
replenisher helps to maintain solution strength.
Darkroom
The purpose of the darkroom is to provide an area where x-ray
films can be safely handled and processed. A well-equipped room
with adequate safelighting aids in producing high-quality radiographic images. Films can be processed outside the darkroom
with chairside manual processing mini-darkrooms (Figure 8-3) or
with a daylight loader–equipped automatic processor
(Figure 8-4). A darkroom remains the standard in most film-based
practices, especially because safelight conditions are required to
handle larger tasks such as extraoral film cassette loading and processing. The darkroom should be located near the area where
radiographs will be exposed for convenient access and should be
large enough to meet the requirements of the practice. The darkroom should be equipped with correct lighting, be well ventilated,
and have adequate storage space for radiographic supplies.
The ability to store radiographic supplies such as extraoral
film cassettes, duplicating film, and processing chemicals and
cleaning supplies in the darkroom will add to the convenience of
maintaining the ideal darkroom. Although storing unused film
in the darkroom may seem convenient, it is not recommended.
In addition to being sensitive to radiation and white light exposure, unexposed film is sensitive to heat, humidity and chemical
fumes, all of which may be increased in the darkroom.
Lighting
X-ray film is sensitive to white light. Any white light in the
darkroom can blacken the film or cause film fog. Therefore, the
darkroom must be light-tight. A light-tight room is one that is
completely dark and excludes all light. Felt strips may have to
be installed around the door(s) to the darkroom or any other
area such as around water pipes where a light leak is discovered.
Although darkroom walls are sometimes painted black, this is
not necessary if the room is completely sealed to white light.
The following forms of illumination are desirable in the wellequipped darkroom.
TABLE 8-2 Composition of Fixer
INGREDIENT CHEMICAL ACTION
Fixing agent
(clearing agent)
Ammonium thiosulfate
or sodium thiosulfate
Removes the unexposed and any remaining undeveloped silver halide
crystals.
Preservative Sodium sulfite Slows the rate of oxidation and prevents deterioration of the fixing
agent.
Hardening agent Potassium alum Shrinks and hardens the gelatin emulsion.
Acidifier Acetic acid Stops further development by neutralizing the alkali of the developer.
FIGURE 8-3 Chair-side minidarkroom box with view-through
plastic filtered top. First cup is filled
with developer, second cup with rinse
water, third cup with fixer, and fourth
cup with wash water. A heater with a
thermostat keeps the solutions at
optimum temperature for rapid
processing. (Courtesy of Dentsply Rinn.)
CHAPTER 8 • DENTAL X-RAY FILM PROCESSING 87
FIGURE 8-4 Automatic processor with daylight loader
attachment for use outside the darkroom. (Courtesy of Air
Techniques, Inc.)
1. White ceiling light. An overhead white ceiling light that provides adequate illumination for the size of the room will
allow the clinician to perform equipment maintenance and
other tasks requiring visibility.
2. Safelight. Safelighting is achieved through the use of a filtered white lightbulb or a special LED (light-emitting
diode) bulb (Figure 8-5) that provide enough light in the
darkroom to allow the clinician to perform activities without exposing or fogging the film. Traditional safelights
consist of a 7 1/2 or 15 watt white incandescent light bulb
with a safelight filter placed over it (Figure 8-6). The safelight filter removes the short wavelengths in the blue-green
region of the visible light spectrum. The longer wavelength
red-orange light is allowed to pass through the filter to illuminate the darkroom. A variety of filters are available.
Orange or yellow filters allow for safe handling of D-speed
film, but E- and F-speed film and most extraoral films
require a red filter. The type of safelight required for film
processing can usually be found written on the film package. LED (light-emitting diode) safelights emit pure red
light and are safe for all film speeds and types.
The term “safe” light is relative. Film emulsion can be
damaged by prolonged exposure even to filtered safelight.
Film handling should be limited to 2 1/2 minutes under
safelight conditions or fogging (film darkening) may occur.
The distance between the lamp and the film is critical. The
rule is 2 1/4 watts per ft (0.3 m) and a 4-ft (1.2 m) minimum
distance from the source of light and the counter space
where the film will be handled. A summary of the factors to
be considered for safelighting are listed in Box 8-1.
3. Viewbox. A viewbox or illuminator is a light source (generally a lamp behind an opaque glass) used for viewing
radiographs. A darkroom equipped with a wall-mounted or
countertop viewbox or illuminator will allow the clinician
the opportunity for a quick reading, viewing the radiograph without leaving the darkroom. A viewbox emits
considerable white light, and care must be taken not to turn
it on when film packets are unwrapped. Additionally, if
films are undergoing the developing process in a manual
processor, the manual processor tank cover must remain on
during the use of a view box.
4. In-use Light. The darkroom door should be locked when
processing films to prevent someone from entering and inadvertently allowing white light into the darkroom. Some darkrooms are equipped with a warning light outside the
darkroom, which indicates that it is not safe to open the door.
Maintenance
Cleanliness and orderliness are essential for the production of
quality radiographs and the safety and health of the clinician
using the area. Infection control protocol for opening film packets
(see Chapter 10) must be strictly adhered to, and chemicals and
other radiographic wastes must be properly handled and disposed
(see Chapter 20). Because safelight conditions reduce visibility,
FIGURE 8-5 Safelight. LED (light-emitting diode) bulb.
BOX 8-1 Safelight Considerations
• LED safelight that emits pure red light.
• 7 1/2 or 15 watt white incandescent bulb with filter.
• Darker red filters provide safer conditions for both intra and
extraoral film handling than amber or yellow colored filters.
• Scratched or cracked filters allow white light to escape.
• 4-ft (1.2-m) minimum distance between lamp and counter
surface where film is to be handled.
• Films should not be subjected to safelight exposure over 2 1/2
minutes.
FIGURE 8-6 Safelight. A commercially available bracket-type lamp
with safelight filter shielding the short wavelength, blue-green region
of the visible light spectrum given off by the bulb. The light given off
by this filter would appear dark red.
88 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
the clinician must be skilled in the procedures to be performed.
Needed materials should be within easy reach, and the person
doing the processing should be familiar with where each item is
located. The workspace counter must be free of substances that
can contaminate films such as water, chemicals, and dust.
A utility sink large enough to accommodate cleaning the
processing equipment should be available in the darkroom. A
wastebasket should be placed in the darkroom for the disposal
of general waste items. Lead foil is separated from other film
wrappings and placed in an appropriate container for safe disposal, and the remainder of the film packet placed in a biohazard container for disposal (see Chapter 20).
Manual Film Processing
Manual processing is a method used to process films by hand in
a series of steps. Although no longer in widespread use, advantages of manual film processing are that it is reliable and not
subject to equipment malfunction. The clinician has more control over the processing procedure, including the ability to adjust
the time–temperature and the ability to read the radiographs
prior to the end of the processing procedure (wet reading). Clinicians often make use of the manual processing procedure to
“rapid” or “hot” process working films discussed at the end of
this section. The biggest disadvantage of manual processing is
the time required to produce a finished radiograph.
Equipment
Manual processing requires the use of:
• Processing tank
• Thermometer
• Timer
• Stirring paddles
• Film hangers, drying racks, and drip pans
1. Processing tank. The processing tank has two insert
tanks placed inside the master tank (Figure 8-7). The
insert tanks hold the developer and fixer solutions. Usually, the left insert tank holds the developer solution,
and the right insert tank contains the fixer solution.
However, these tanks should be labeled to prevent confusion as to which tank contains which chemical. The
master tank holds water between the insert tanks for
rinsing and washing the films.
Most tanks are made of stainless steel, which does not
react with processing chemicals. Insert tanks are large enough
to accept an extraoral film. The
capacity of an insert tank is 1 gallon (3.8 L).
The insert tanks are removable to facilitate cleaning. The
master tank is connected to the water intake and to the drain.
When in use, fresh water circulates constantly. An overflow
pipe keeps the level of the water constant when the tank is full.
Some tanks are equipped with a temperature control device, a
water-mixing valve that mixes the hot and cold water in the
pipes to any desired temperature. A close-fitting lightproof
cover completes the tank assembly.
8 * 10 in. (20 * 26 cm)
2. Thermometer. A thermometer is necessary to determine the
temperature of the developing solution for time–temperature
manual processing (Figure 8-8).
3. Timer. An accurate interval timer is necessary for time–temperature manual processing. The timer is used to indicate how
long the film is placed in the developing and fixing solutions
and in the rinse and wash water baths. The timer should have
an audible alarm to alert the radiographer to remove the films
from each of the solutions. Timers with a digital readout
should emit red light only so as not to fog the film.
4. Stirring paddles. Two stirring paddles must be available for
mixing the chemicals used for manual processing. To avoid
contamination, the developer and the fixer each need their
own stirring paddle. The paddles should be made of stainless
steel or other material that will not corrode in the processing
chemicals.
Cover Outlet and
overflow pipe
Insert
tank Processing
unit
Insert
tank
FIGURE 8-7 Processing tank with removable inserts. The central
compartment holds the rinse/wash water. Usually, the insert on the
left is filled with the developer solution, and the insert on the right is
filled with the fixer solution.
FIGURE 8-8 Floating thermometer used to record the
temperature of the developer when manual processing.
CHAPTER 8 • DENTAL X-RAY FILM PROCESSING 89
5. Film hangers, drying racks, and drip pans. A film
hanger is a stainless steel frame to which the films can be
attached. A film hanger allows the radiographer to transport the films to and from each of the processing solutions
(Figure 8-9). Various film hanger sizes are available that
accommodate from 1 to 20 films. Film hangers have an
identification tag near the curved handle on which the
patient’s name can be written. When manual processing
was the norm, films would be dried with a commercial
film dryer. Film dryers are not as readily available today.
Instead, drying racks (towel racks) can be mounted for
hanging film hangers to air dry. Drip pans are placed
underneath the drying racks to catch water from wet films.
Preparation
The key to manually processing dental radiographs is adequate
preparation.
1. Solution levels must be checked to be sure the developer
and fixer will cover the top clips of the film hanger. The
tanks are full when the solution levels are about one inch
from the top. Add fresh solution if necessary.
2. Developer and fixer must be stirred thoroughly to prevent
the heavier chemicals from settling to the bottom and to
equalize the temperature of the solution throughout the tanks.
3. The temperature of the developing solution must be
determined using a thermometer after stirring (Figure 8-8).
The ideal manual processing temperature is 68°F (20°C)
with a development time of five minutes. Lower temperatures make the chemical reaction sluggish, and higher temperatures increase film fog. Temperature variations from
the ideal may be acceptable as long as the developing time
is correspondingly adjusted. The radiographer should consult a time–temperature development chart similar to the
one in Table 8-3 to adjust developing time appropriately.
4. The film hanger should be selected and examined. The
clips need to be in proper working order. Loose clips may
cause films to fall off in the tank during the process. Extraoral film hangers have channels into which the film fits and
is secured by a hinged retaining channel over the open end
of the hanger. Film hangers should be labeled with the
patient’s name or otherwise identified.
Procedure (Procedure Box 8-1)
The manual film processing sequence consists of these five steps:
1. Develop. The film hanger with the attached films should
be immersed into the developer tank first. Gently agitating
the hanger up and down a few times—taking care not to
splash—will keep air bubbles from clinging to the film. Air
bubbles prevent the developer from contacting all areas of
the film. Safelight conditions must be maintained throughout the development step unless the light-tight cover is in
place on the processing tank.
2. Rinse. The purpose of the rinsing step is to remove as
much of the alkaline developer as possible before placing
the film into the fixer. When the timed developing step is
complete, under safelight conditions, the film hanger
should be lifted above the developing insert tank and
allowed to drain a few seconds to minimize the amount of
developer that will be removed from the tank. After gently
agitating the film hanger in the rinse water, it should be
held above the rinse water to drain for a few seconds to
prevent diluting the fixer solution with excess water.
3. Fix. The film hanger with the attached films should be
immersed into the fixer insert tank next, gently agitating
the hanger to keep air bubbles from clinging to the film.
Safelight conditions must be maintained for the first two
or three minutes of the recommended fixing time. If the
radiograph is needed immediately for a quick reading of
the image, the film may be read under white light conditions after two or three minutes of fixing. This is called a
A
B
C
FIGURE 8-9 Intraoral film hanger with 12 clips. (A) Curved
portion at the top allows the radiographer to rest the hanger on the
rim of the tank insert for the duration of the time required. (B) White
plastic identification tag on which the patient’s name can be written
in pencil and later erased. (C) Clamps with three-point positive grip
hold the film securely in place. (Courtesy of Dentsply Rinn.)
TABLE 8-3 Time–Temperature Chart
TEMPERATURE
DEVELOPMENT TIME
(MIN)
60°F (15.5°C) 9
65°F (18.3°C) 7
68°F (20°C) optimum 5
70°F (21.1°C) 4.5
75°F (23.9°C) 4
80°F (26.7°C) 3
90 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
4. Wash. Washing the film removes all remaining chemicals.
When the fixing step is complete, the film hanger should
be lifted above the fixer insert tank and allowed to drain a
few seconds to minimize the amount of fixer that will be
removed from the tank. The films should be placed in the
circulating water for 20 minutes. Leaving the films in the
water slightly longer than 20 minutes is permissible, but
leaving a film in water more than a few hours will begin to
dissolve the emulsion, and the emulsion may peel away
from the film base. The processing tank cover should
remain in place during the washing step; however, it is not
necessary to maintain safelight conditions during this step.
5. Drying. Following the wash step, the film hanger should be
lifted above the water tank and allowed to drain. Excess
PROCEDURE 8-1
Manual film processing
1. Maintain infection control (see Chapter 10).
2. Select a film hanger and label with patient information.
3. Open the light-tight cover of the manual processing tank.
4. Stir the developer and fixer solutions to ensure even concentration throughout the tank. Use a different
stirring paddle for each, developer and fixer, to prevent contamination of solutions.
5. Check the developer temperature.
6. Refer to the time–temperature recommendations of the solution manufacturer and set timer. (Optimal
time–temperature for manually processed radiographs is 68°F for five minutes.)
7. Lock the darkroom door, turn off the white light, and turn on the safelight.
8. Open the film packets (see Procedure Box 10–5) and place films on hanger.
9. Immerse the films into the developer solution and agitate film hanger for five seconds to release trapped
air bubbles.
10. Set the timer. (Time is dependent on temperature of the developer solution.)
11. Close the light-tight cover while the film is developing.
12. When the developing time is complete, under safelight conditions, open the light-tight cover and remove
film hanger with films attached from developer solution.
13. Pause a few seconds over the developer tank to allow the excess solution to drain from the films.
14. Immerse the film hanger into the water rinse and agitate for 30 seconds.
15. Pause a few seconds over the water tank to allow the excess water to drain from the films.
16. Immerse the film hanger into the fixer solution and agitate for five seconds to release trapped air bubbles.
17. Activate the timer for double the time in the developer or 10 minutes.
18. Close the light-tight cover for the first two to three minutes of fixation. (It is safe to view the films under
white light after two or three minutes of fixation for a wet reading, following which the films must be
returned to the fixer solution for completion of the fixation time for archival quality.)
19. Remove the film hanger from the fixer solution when the time is up.
20. Pause a few seconds over the fixer tank to allow the excess solution to drain from the films.
21. Immerse the films into the water wash for 20 minutes.
22. Remove the film hanger from the water wash when the time is up.
23. Place the film hanger in a commercially made film dryer or hang to air dry when the wash is complete.
24. Mount and label the dried films.
wet reading. The film can be rinsed in water for a short
interval and viewed at a viewbox. The film must be returned
to the fixer as soon as possible to complete fixation and permit further shrinking of the emulsion. If this is not done,
some of the unexposed silver halide grains may be left on
the film, giving it a fogged and discolored appearance after
it dries. Also, the emulsion may not completely harden.
The recommended fixing time is double the development time, or 10 minutes. The fixing time is not as critical
as the developing time, so films may remain in the fixer
slightly longer. When the fixing time is too short, the result
can be slow drying, poor hardening of the emulsion, a possible partial loss of detail, and darkening over time. When
the fixing time is excessively long, the image will lighten.
CHAPTER 8 • DENTAL X-RAY FILM PROCESSING 91
water may be removed by gently shaking the film hanger
over the water tank. Films may be dried in a commercial
heated drying cabinet if available or suspended from a rack
until dry.
Following the Procedure
The steps taken to secure the darkroom are equally important to
the preparation steps.
1. Once the white lights are turned on and visibility
improves, the radiographer should check to see that none
of the films have loosened from the clips and dropped on
the floor or the bottom of the tank.
2. The work area should be cleaned as needed. Any moisture
caused by dripping or accidental splashing of the water or
chemical solutions must be wiped up.
3. After dry, films should be removed from the hangers and
placed in properly identified protective envelopes or on
film mounts with identifying data (see Chapter 21).
4. Identification markings should be removed or erased from
the hangers. The hangers should be cleaned and dried as
needed.
5. At the end of the workday, turn off the water to the tank, drain
the water compartment, and turn off all lights in the darkroom. Leave the cover in place over the developer and fixer
tanks to prevent oxidation and to contain chemical fumes.
Rapid (Chairside) Film Processing
Manual processing can be used to produce a working radiograph
without a darkroom in about 30 seconds. Rapid or chair-side
processing with the use of special, faster-acting chemicals and a
compact light-tight box that acts as a miniature darkroom
(Figure 8-3) can be valuable in endodontic, oral surgery practices
and at remote sites, such as community outreach oral health projects where a darkroom is not available. A significant amount of
time can be saved, for example, when it is necessary to expose a
series of single films to check the progress in opening and cleaning out a root canal during endodontic treatment. However, rapid
processing has definite limitations and is not intended to replace
conventional processing.
Films processed in this manner are seldom suitable for filing with the patient’s permanent record. Short developing and
fixing times, combined with minimal washing, result in a substandard radiograph. Rapid processing chemistry does not produce archival (permanent) results, and the films will eventually
discolor. In the event that the film is to be retained with the permanent record, it should be refixed for 4 minutes and washed
for 20 minutes at normal conventional darkroom temperatures
and conditions. Although rapid processing fulfills the dentist’s
need to receive information quickly, it is at the expense of
image quality and longevity.
Equipment
Rapid processing requires the use of a light-tight countertop
box that has two light-tight openings, or baffles, through which
the radiographer’s hands can be passed into the working compartment when the lid is closed. A transparent plastic top
functions to filter out unsafe light while permitting the operator to see into the box to unwrap the film packet and manually
proceed through the processing steps. Four cups are set up
inside the box containing developer, rinse water, fixer, and
wash water. Developing and fixing solutions made especially
for rapid processing can be heated to 85°F (29.4°C) by a calibrated heater in the unit. Chemicals used for chairside processing are used for processing a limited number of films and then
discarded appropriately (see Chapter 20). A small film hanger
with a single clip is used to manually transfer the film from
solution to solution.
Procedure
The steps for processing films using the rapid processing
method are identical to the steps used for manual processing
(Procedure Box 8-1). The film is placed in the developer first,
then rinsed and placed in the fixer, then washed and dried. The
development time ranges from 5 to 15 seconds; the fix time is
approximately 30 seconds.
Following the Procedure
1. Turn off the heater.
2. Empty, rinse, and dry each of the cups. Dispose of the used
fixer appropriately (see Chapter 20).
3. Clean and disinfect the inside of the chairside darkroom.
Wipe off the transparent plastic top as needed.
4. Continue fixing and complete the washing and drying steps to
convert a working film to a permanent image.
Automatic Film Processing
Automatic processing is more commonly employed to process
dental x-ray film. Because of its ability to produce a large volume
of radiographs in less time (usually five minutes from developer
to dried finished radiograph), it is often preferred over manual
processing. Another advantage of an automatic processor is the
machine’s ability to regulate automatically the temperature of the
processing solutions and the time of the development process.
Automatic processing has several disadvantages, however,
including initial unit expense, possible equipment malfunction,
increased maintenance required for optimal output, and more
rapid chemical depletion than with manual processing chemistry.
Equipment
Automatic processing equipment varies in size and complexity
(Figures 8-4 and 8-10). Some processors have a limited capacity
and process only intraoral or certain sizes of extraoral films; others can handle any dental film regardless of size. Most are
intended for use in the darkroom under safelight conditions.
Automatic processors equipped with daylight loaders have a
light-tight baffle for inserting the hands while unwrapping the
film and can be used under normal white light conditions with a
filter that acts as a safelight over the film entry slots (Figure 8-4).
Most automatic processors consist of three tanks or compartments, one each for the developer, fixer, and water, and a drying
chamber (Figure 8-11). All automatic processors require water.
Some machines are connected to existing plumbing, whereas others have a self-contained water supply. A heating unit warms the
92 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
processing chemicals to the required temperature so there may be
a warming-up period before the unit is operational.
The automatic film processing sequence usually consists
of only four steps: developing, fixing, washing, and drying.
The use of a roller transport system helps “squeeze” excess
solution from the film surface, allowing the automatic processor to omit the rinsing step between developing and fixing.
Unwrapped film is fed into the film feed slot on the outside of the processor. The roller transport system moves the
film through the developer, fixer, water, and drying compartments. Motor-driven gears or belts propel the roller transport
system. The film emerges from the processor through an
opening on the outside of the processor called the film recovery slot. Most machines process a film in approximately five
minutes. Some automatic processors have a two-minute setting for producing working radiographs for a quick reading.
Preparation
To prepare the automatic processor:
1. The water supply to the automatic processor should be
turned on. If the processor uses a self-contained water
supply, the water bottles should be checked and filled as
needed.
2. The chemicals should be replenished or changed as necessary. Ensure that the tanks are filled to the levels indicated by the manufacturer.
3. The automatic processor should be turned on and
allowed to warm up according to the manufacturer’s recommendations.
4. A special cleaning film designed to remove debris from the
unit rollers should be run at the beginning of the day or if the
machine has been idle several hours.
FIGURE 8-10 Automatic processors. (Left image: Courtesy of Air Techniques, Inc.)
Film
path
Developer Fixer Wash
Drying elements
Film exit
FIGURE 8-11 Schematic illustration of automatic film processor.
Film is transported by roller assemblies through each of the processing steps.
CHAPTER 8 • DENTAL X-RAY FILM PROCESSING 93
PRACTICE POINT
In addition to being less effective, a breakdown in the
integrity of the processing chemicals will occur if chemicals
are not replenished or changed at the recommended intervals. This breakdown causes the solutions to become slick.
Slick solutions cause the films to slide or slip through the
roller transport system of the automatic processor, making it
difficult for the rollers to advance the film and resulting in
films that get stuck inside the machine.
Procedure (Procedure Box 8-2)
Unless the automatic processor is equipped with daylight loader
baffles, the processing procedure should begin under safelight
conditions. An unwrapped film is placed into the designated
feed slot on the processor. Once the film is completely inside the
automatic processing unit, safelighting is no longer necessary.
When processing multiple films, each should be placed
into alternating feed slots, one at a time, to prevent the films
from overlapping and getting stuck in the machine. Five to ten
seconds should elapse between the insertion of each film.
Inserting the films too rapidly after each other will also result
in overlapping films.
When more than one operator uses the processor, or when
processing more than one patient’s films, a method of labeling
the feed slots for film identification is necessary. Depending on
the processor model, the films will exit the processor in about
five minutes, dried and ready for mounting.
PROCEDURE 8-2
Automatic film processing
1. Maintain infection control (see Chapter 10).
2. Turn on water supply.
3. Check for replenishment of chemicals.
4. Turn on the automatic processor.
5. Set the appropriate time/temperature as indicated by the manufacturer.
6. If it is the beginning of the day, or after several hours of inactivity, run a specially manufactured cleaning
film through the processor and discard.
7. Lock the darkroom door, turn off the white light, and turn on the safelight.
8. Open the film packets (see Procedure Box 10-5) and place films into the automatic processor feed slot.
9. Allow the rollers to take the film before releasing.
10. Wait 10 seconds before placing an additional film into the same slot to avoid overlapping films.
11. Retrieve the processed films when the cycle is complete, usually about five minutes.
12. Mount and label the dried radiographs.
Following the Procedure
1. Once the white lights are turned on and visibility
improves, the radiographer should check to see that all the
films have exited the processor.
2. Unless equipped with an automatic shutoff, the unit should
be turned off or placed in stand-by mode to conserve water
that would continue to run after the films have finished
processing.
3. The work area should be cleaned as needed. Any moisture
caused by dripping or accidental splashing of chemical
solutions during replenishment must be wiped up.
4. At the end of the workday, the main power and water
supply to the unit should be turned off. Leave the cover
in place over the developer and fixer tanks to prevent
oxidation and to contain chemical fumes. Turn off all
lights in the darkroom.
Processing Chemical Maintenance
Both manual and automatic processing methods require chemical maintenance and solution replenishing and changing. Protective eyewear, mask, utility gloves, and a plastic or rubber
apron should be worn when cleaning the processing tanks or
changing the solutions.
Processing chemistry becomes weakened or lost in several ways. A small amount of developer and fixer is lost
when chemicals adhere to the film surfaces during transfer
from solution to solution. During manual processing stirring
paddles, the thermometer, and film hangers all contribute
to the loss of solution. Additionally, transfer of films
between solutions will slowly contaminate the chemicals and
weaken them.
94 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
Weakened chemistry also occurs through oxidation, the
union of a substance—in this case, the developer and fixer—
with the oxygen in the air. The developer is especially subject to
oxidation in the presence of air and loses its effectiveness very
quickly. Whenever possible, the processing tank covers should
remain in place to slow oxidation and evaporation. The cover
should be removed only when adding solutions to the proper
level; when checking the temperature of the developer, and
when inserting, removing, or changing the film hangers from
one compartment or insert to another (manual processing). Care
must be taken not to rotate the processor cover when it is
removed. Causing only a few drops of condensed developer to
fall into the fixer or vice versa will contaminate and weaken the
solutions. All chemistry must be changed periodically to avoid
diminishing quality. The useful life of the solutions depends on:
• The original quality or concentration of the solution
• The original freshness of the solution used
• The number of films that are processed
• Contamination, oxidation, and evaporation of the chemicals
Many chemical manufacturers recommend that processing
solutions be changed at least every four weeks under “normal” use.
Because normal use may be defined differently among different
practices, refer to the manufacturer recommendations to determine
reasonable intervals to change solutions. One way to maintain
solution strength in between changes is through replenishment.
Replenishment consists of removing a small amount of
developer and fixer and replacing with fresh chemistry or
chemical replenisher specifically made for this purpose. For
every 30 intraoral films processed, it is recommended that 6 to
8 ounces of developer and fixer be removed and discarded. (See
Chapter 20 for safe and environmentally sound protocols for
discarding radiographic wastes.) Fresh chemicals should be
added to raise the solution levels in the tanks to the full level.
REVIEW—Chapter summary
Film processing is a series of steps that converts the invisible
latent image on the dental x-ray film into a visible permanent
image called a radiograph. The sequence of processing steps is
developing, rinsing, fixing, washing, and drying. Developing
reduces the exposed silver halide crystals within the film emulsion to black metallic silver. Rinsing removes the alkaline
developer before the film enters the fixer solution. Fixing
removes the unexposed and/or undeveloped silver halide crystals from the film emulsion. Washing removes any remaining
traces of the chemicals. Drying preserves the film for storage as
a part of the patient’s permanent record.
Two processing chemicals are used—an alkaline developer
and a slightly acidic fixer. The four ingredients that make up the
developer are developing agents (hydroquinone and elon), a
preservative (sodium sulfite), an activator (sodium carbonate),
and a restrainer (potassium bromide). The purpose of the developing solution is to reduce the exposed silver halide crystals to
PRACTICE POINT
It is important to note that the processing chemicals used
in automatic processors differ from those used in manual
procedures. Solutions for use in automatic processors are
supersaturated, and the developer contains more hardening agents. The chemical solutions in automatic processors
are heated to temperatures much higher than those used
in manual processing—as high as 125°F (52°C) in some
units. Advanced film technology has produced film emulsions that can withstand these temperatures for the short
times required in automated processing without excessive
softening or melting.
Depending on the workload, automatic processors require
daily, weekly, or monthly cleaning. A specially made cleaning film
may be run through the processor to remove any dirt and residual
gelatin from the rollers daily or more often if the processor sits
idle for several hours (Figure 8-12). However, complete cleaning and maintenance of the roller transports and solutionholding tanks is also required. If the rollers are not kept clean,
the radiographs emerge streaked, stained, or worse, with scratched
emulsion. Most manufacturers recommend that the roller assembly
be removed and cleaned weekly, in warm, running water and special cleansers. It is important to follow the manufacturer’s instructions concerning care and maintenance.
FIGURE 8-12 Cleaning sheet or specially prepared film run
through the processor to remove any residual debris from the rollers.
Some processors automatically replenish the solutions; others
depend on the operator to keep them at the correct level.
Automatic processors require strict adherence to manufacturers’ instructions for chemical replenishment and changes and
for cleaning the unit to maintain optimal performance. Few
pieces of equipment in the oral health care practice require such
diligence and regular care.
CHAPTER 8 • DENTAL X-RAY FILM PROCESSING 95
black metallic silver. The four ingredients that make up the fixer
are a fixing agent (sodium thiosulfate), a preservative (sodium
sulfite), a hardening agent (potassium alum), and an acidifier
(acetic acid). The purpose of the fixing solution is to remove the
undeveloped silver halide crystals and harden the emulsion.
A darkroom must shut out all white light. With the exception
of automatic processors equipped with daylight loaders and
chairside rapid processing miniature darkroom boxes, all processing must be done in the darkroom under safelight conditions.
Safelighting is achieved with a red LED (light-emitting diode) or
a white incandescent lightbulb with a filter that eliminates short
wavelength, blue-green colored light. Unwrapped film should
not be exposed to safelight longer than about 21
⁄2 minutes.
Advantages of manual film processing include reliability,
no equipment to malfunction, control over the time and temperature, and the ability to produce a wet reading. The biggest
disadvantage of manual processing is the long time required
to produce a finished radiograph. Manual processing requires
a processing tank, thermometer, timer, stirring paddles, film
hangers, and drying racks. The ideal time–temperature for
manual processing is 68°F (20°C) for five minutes. Colder
developer solution requires a longer developing time; warmer
developer solution requires a shorter developing time.
A chairside miniature darkroom is utilized to produce
working radiographs by the rapid processing method. Films are
manually processed with special developer and fixer, which
produce a radiographic image in less than 1 minute. Rapid processing chemistry does not produce archival results, and the
films will eventually discolor. The advantage of rapid processing is that it fulfills the need to receive rapid information. However, image quality will be diminished.
The biggest advantage of automatic film processing is the
short time required to produce a finished radiograph. Automatic
processors equipped with daylight loader attachments can be
used to process film without a darkroom. Disadvantages
include initial unit expense, possible equipment malfunction,
increased maintenance required for optimal output, and rapid
chemical depletion. Automatic processors use a roller transport
assembly to advance the films automatically from solution to
solution, producing a finished radiograph in five minutes.
Step-by-step procedures for manual, rapid, and automatic
processing are presented in this chapter.
Oxidation over time and chemical contamination through
normal use prompt solution changes and regularly scheduled
equipment maintenance and cleaning. The useful life of the solutions is determined by the original quality or concentration of the
solution, the freshness of the solution, the number of films that are
processed, and the contamination of the chemicals. Replenishment
helps prolong the life of the processing solutions.
RECALL—Study questions
1. Which term best describes the process by which the
latent image becomes visible?
a. Reticulation
b. Reduction
c. Activation
d. Preservation
2. Which of these is the correct processing sequence?
a. Rinse, fix, wash, develop, dry
b. Fix, rinse, develop, wash, dry
c. Develop, rinse, fix, wash, dry
d. Rinse, develop, wash, fix, dry
3. The basic constituents of the developer solution are
a. reducing agent, activator, preservative, restrainer.
b. reducing agent, acidifier, preservative, restrainer.
c. clearing agent, activator, preservative, restrainer.
d. clearing agent, preservative, hardener, acidifier.
4. During which step of the processing procedure are the
exposed silver halide crystals reduced to metallic silver?
a. Developing
b. Fixing
c. Rinsing
d. Washing
5. Which ingredient removes the unexposed/undeveloped
silver halide crystals from the film emulsion?
a. Acetic acid
b. Potassium bromide
c. Sodium thiosulfate
d. Hydroquinone
6. Which ingredient causes the emulsion to soften and
swell?
a. Acidifier
b. Preservative
c. Restrainer
d. Activator
7. Which ingredient hardens the emulsion?
a. Elon
b. Potassium alum
c. Sodium carbonate
d. Sodium sulfite
8. Chemically, the developer used in an automatic processor contains more _____________ than developer used
for manual processing.
a. activator
b. acid
c. preservative
d. hardener
9. Each of the following should be considered when setting up an ideal darkroom EXCEPT one. Which one is
the EXCEPTION?
a. Black walls
b. Location
c. Lighting
d. Size
10. Which of the following colors of safelight filters is safe
for processing all film speeds?
a. Yellow
b. Green
c. Red
d. Blue
96 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
11. What is the minimum safe distance to position the safelight above the work area in the darkroom?
a. 2 ft (0.6 m)
b. 4 ft (1.2 m)
c. 6 ft (1.8 m)
d. 8 ft (2.4 m)
12. What is the appearance of the radiographic image if a
film is exposed to a safelight too long?
a. Oxidized
b. Fogged
c. Fixed
d. Attenuated
13. Which of these is considered a disadvantage of
manual processing over automatic processing?
a. Darkroom required
b. Processing time is long
c. Chemicals must be replenished
d. Temperature must be regulated
14. A thermometer is used for manual processing to determine the temperature of the
a. developer solution.
b. water.
c. fixer solution.
d. Both a and c
15. Each of the following is necessary and required for
manual processing EXCEPT one. Which one is the
EXCEPTION?
a. Thermometer
b. Timer
c. Film dryer
d. Film hanger
16. What is the ideal temperature for processing film manually?
a. 60°F (15.5°C)
b. 68°F (20°C)
c. 75°F (23.9°C)
d. 83°F (28.3°C)
17. A film may be safely exposed to white light for a wet
reading after two or three minutes of
a. developing.
b. rinsing.
c. fixing.
d. washing.
18. Each of the following is true regarding rapid film processing EXCEPT one. Which one is the EXCEPTION?
a. Uses a miniature darkroom placed on the counter in
the operatory
b. Produces archival (permanent) quality radiographs
c. May use developer that is super heated to high temperatures
d. Produces a radiographic image in about 1 or 2 minutes
19. Each of the following is an advantage of automatic processing over manual processing EXCEPT one. Which
one is the EXCEPTION?
a. Less maintenance
b. Decreased processing time
c. Increased capacity for processing
d. Self-regulation of time and temperature
20. Replenisher is added to the developing solution to compensate for
a. oxidation.
b. loss of volume.
c. loss of solution strength.
d. All of the above
21. Which processing method requires the most maintenance and the strictest adherence to regular replenishment and cleaning?
a. Manual
b. Rapid
c. Automatic
REFLECT—Case study
You work for a temporary agency that provides staffing for
oral health care practices in your area. Today your employer
has sent you to a practice organized and set up for a lefthanded practitioner. Your first patient requires a bitewing
series of radiographs. You expose the films and proceed to
the darkroom for processing. Unknown to you, this practice
has set up the manual processing tanks with the developing
solution tank on the right and the fixer tank on the left. You
are used to working with processing tanks set up with the
developing solution on the left and the fixer on the right, and
you proceed to process your films in this manner. What effect
will this have on the resultant radiographs? Why will they
look this way? Explain why the processing solutions will
produce this result. What can you do to avoid this mistake in
the future? What can this practice do to prevent this mistake
from happening again?
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson. Chapter 1, “Introduction to Radiation
Safety and Dental Radiographic Equipment”
REFERENCE
Carestream Health, Inc. (2007). Kodak Dental Systems:
Exposure and processing for dental film radiography. Pub.
N-414. Rochester, NY.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Explain the fundamental concept of digital radiography.
3. Differentiate between direct and indirect digital imaging.
4. List the equipment used in digital imaging.
5. List and describe three types of digital image receptors.
6. Discuss digital radiography’s effect on radiation exposure.
7. List and describe five software features used to enhance digital image interpretation.
8. Identify advantages and limitations of digital radiography.
KEY WORDS
Analog
Artificial intelligence
Charge-coupled device (CCD)
Complementary metal oxide
semiconductor (CMOS)
Digital image
Digital Imaging and Communications
in Medicine (DICOM)
Digital radiograph
Digital subtraction
Digitize
Direct digital imaging
Gray scale
Gray value
Indirect digital imaging
Line pair
Noise
Photostimuable
phosphor (PSP)
Pixel
Sensor
Solid state
Spatial resolution
Storage phosphor
x-coordinate
y-coordinate
Digital Radiography
CHAPTER
9
CHAPTER
OUTLINE
 Objectives 97
 Key Words 97
 Introduction 98
 Fundamental
Concepts 98
 Uses 98
 Methods
of Acquiring
a Digital Image 99
 Equipment 101
 Characteristics
of a Digital
Image 108
 Radiation
Exposure 109
 Digital Imaging
and Communications
in Medicine
(DICOM) 109
 Review, Recall,
Reflect, Relate 111
 References 113
98 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
Introduction
Digital radiographs, or filmless imaging, is rapidly becoming
an integral part of the paperless oral health care practice
(Figure 9-1). The introduction of a computer approach to
x-rays with almost instant images has the potential to improve
the quality of oral health care while reducing radiation exposure for the patient. Although the fundamentals of film-based
radiography are necessary, it is important that the dental assistant and dental hygienist have an understanding of the basic
concepts of digital radiography and be prepared to utilize digital
technology.
The purpose of this chapter is to present the fundamental
concepts of digital radiography, to introduce the types of digital
imaging currently available, and to discuss the advantages and
limitations of digital radiography.
Fundamental Concepts
The term radiography is derived from the words radiation
and photography, meaning that a radiograph is a photographic image created using radiation. Digital imaging systems used in dentistry replace film with a solid state (no
moving parts) image receptor called a sensor (Figure 9-2) or
a polyester plate covered with phosphor crystals called a
photostimuable phosphor (PSP) plate (Figure 9-3). Images
made within a computer using these image receptors no
longer need the photographic process. The term imaging has
come to replace the term radiography when referring to these
images. In radiography, we “take a radiograph,” whereas in
digital imaging we “acquire an image.” Table 9-1 lists several
terms pertaining to digital imaging that you should be familiar with.
The difference between a digital image and a film-based
radiograph is that a digital image has no physical form. Digital
images exist only as bits of information in a computer file that
tell the computer how to construct an image on a monitor or
other viewing device (Figure 9-4). Digital radiography systems
are not limited to intraoral images. Panoramic and other extraoral radiographic digital imaging systems are also available.
Uses
Digital radiography is used for the same reasons one would use
film-based radiography, including to:
• Detect, confirm, and classify oral diseases and lesions
• Detect and evaluate trauma
FIGURE 9-1 Digital intraoral radiographic system. The
radiographic image is displayed on the computer monitor within
seconds of exposure.
FIGURE 9-2 Solid-state digital sensors in sizes comparable to
film. (Courtesy of Planmeca.)
FIGURE 9-3 PSP plate digital image receptor in sizes
comparable to film. (Courtesy of Air Techniques, Inc.)
CHAPTER 9 • DIGITAL RADIOGRAPHY 99
FIGURE 9-4 An example of a digital radiographic image. (Courtesy
of Dentrix Dental Systems)
film or a digital image receptor. The significant difference
between film-based radiography and digital imaging is that the
film is replaced with a digital image receptor.
Methods of Acquiring a Digital Image
It is sometimes desirable to convert film-based radiographs to
digital images, for example, when updating to a paperless practice or to send an image electronically to another practice.
Radiographs taken with film can be digitized by scanning or by
digitally photographing the existing radiograph. A device
called a transparency adapter can be mounted in the lid of a
paper document scanner that will allow the scanner to scan
film-based radiographs (Figure 9-5). Or existing radiographs
can be placed on a viewbox and photographed with a digital
camera. Although digitizing film-based radiographs with these
methods can play a valuable role, the quality of the scanned or
photographed images will most likely be inferior to an original
digital image because the resultant image is essentially a copy.
It should be noted that some practitioners call the process of
digitizing film-based radiographs indirect digital imaging. In
this text we will refer to images obtained via a photostimuable
phosphor (PSP) plate indirect imaging. This will be explained
in the next section.
True digital images are obtained via either direct digital
imaging and indirect digital imaging.
• Evaluate growth and development
• Provide information during dental procedures such as root
canal therapy and surgery
The techniques and methods learned for exposing intra- and
extraoral radiographs are the same whether using traditional
TABLE 9-1 Terminology
TERM DEFINITION
Analog Relating to a mechanism in which data is represented by continuously variable physical quantities.
Artificial intelligence Ability of a computer to perform decision making similar to a human being.
CCD and CMOS device. metal oxide semiconductor. Solid-state detectors used
in electronic devices such as digital cameras (CCD) and memory chips of a CPU (central processing unit; CMOS).
In direct digital radiography, a CCD or CMOS (which one is used will depend on the manufacturer) sensor image
receptor converts x-rays to an electronic signal that is then reconstructed by the computer and displayed on a
monitor.
CCD = charge-coupled CMOS = complementary
Digital subtraction A process of digitally merging two images to show changes that occur over time or as the result of treatment intervention. The like images “cancel” each other out, clearly imaging the differences.
Digitize To convert analog data, such as a film-based image, into a digital form that can be processed by a computer.
Electronic noise An electrical disturbance that clutters the digital image.
Gray value The number that corresponds to the amount of radiation received by a pixel.
Gray scale Refers to the number of shades of gray visible in an image.
lp/mm Line pairs per millimeter. A term used to refer to the spatial resolution or sharpness of the image.
Pixel Short for picture element (pix, plural of picture and el, short for element). Discrete units of information that
together constitute an image.
PSP plate Indirect digital image receptor composed of a polyester plate covered with storage phosphor crystals that “store” x-ray energy as a latent image. A laser scanning device releases the stored energy
and sends it to a computer that reconstructs the image to display on a computer monitor.
PSP = photostimuable phosphor.
Spatial resolution The discernable separation of closely adjacent image details.
x- and y-coordinates Values assigned to dimensions of a pixel that tell the computer where the pixel is located.
100 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
Direct Digital Imaging
A solid state sensor, containing an electronic chip based
on either charge-coupled device (CCD) technology or
complementary metal oxide semiconductor (CMOS) technology, replaces conventional film as the image receptor.
Both CCD and CMOS technologies work equally well at
converting x-rays into an electronic signal that is sent to the
computer. The difference between the two is in the architecture of the electronic chip. The use of CCD or CMOS technology depends on the manufacturer of the digital imaging
system.
CCD and CMOS sensors are made up of a grid of x-ray
or light sensitive cells (Figure 9-6). Each cell represents one
pixel in the final image. A pixel serves as a small box or
“well” into which the electrons produced by the x-ray exposure are deposited. A pixel is the digital equivalent of a silver
halide crystal used in film-based radiography. As opposed to
film emulsion that contains a random arrangement of silver
halide crystals, pixels are arranged in a structured order in
rows and columns. Each pixel has an x-coordinate, a y-coordinate, and a gray value. The x- and y-coordinates are numbers that represent where the pixel is located (what row and
column) in the grid. When x-rays strike the sensor, the pixels
are excited in such a way that an electronic charge is produced on the surface of the sensor. The number that represents the gray value increases or decreases in proportion to
the number of x-rays striking each pixel. The sensor then
transmits the x- and y-coordinates and the gray value,
through a wire or wirelessly via radio frequency to a circuit
board inside the computer. The computer software processes
the x- and y-coordinates and a gray value number to reconstruct an image to display on the monitor.
Indirect Digital Imaging
Photostimuable phosphor (PSP) plate sensor technology,
also called a storage phosphor system, replaces conventional
film as the image receptor, but uses very different technology
than CCD and CMOS systems. PSP sensors very closely parallel film in the way they look and in the way the radiographic
image is captured as analog data and then processed (Figure 9-7).
PSP technology uses polyester plates coated with something
called a storage phosphor (europium activated barium fluorohalide). When exposed to x-rays this storage phosphor “stores”
the x-ray energy as a latent image similar to the way silver
halide crystals within film emulsion store a latent image. After
exposure the PSP plate is placed into a laser scanning device
(Figure 9-8). As the laser beam passes over the PSP plate,
energy in proportion to the amount of x-ray energy absorbed is
released. The released energy, in the form of light, is converted
to an electrical signal that is then converted into digital values.
The computer uses these digital values to reconstruct an image
on the computer monitor. The laser scanner processing step
makes PSP technology seem similar to film-based radiography
FIGURE 9-5 Digitizing film-based radiographs is accomplished
by scanning into the computer. (Courtesy of DEXIS, LLC.)
189 187 185
180 101
179 105
109
102
175 178 181 249
245
248
189 187 185 246
180 101
179 105
109
102
175 178 181 249
245
248
246
x-coordinate
y-coordinate
Gray value
FIGURE 9-6 Diagram of sensor grid. Each square represents a
pixel. Pixels store a number from 0 to 255, representing pure black at 0
to pure white at 255 that the computer will re-construct into an image.
FIGURE 9-7 PSP plate. The similar dimensions allow for the use of
a film holder to place the PSP plate. (Courtesy of Gendex Dental Systems.)
CHAPTER 9 • DIGITAL RADIOGRAPHY 101
FIGURE 9-8 PSP scanner. Operator placing the exposed PSP
sensor plates in to the laser scanning device. (Courtesy of Gendex
Dental Systems.)
in that the image receptor is exposed and then “developed”
later. Because of this additional laser scanning step, this
method of acquiring a digital image is referred to as indirect
digital imaging. After processing with the laser scanner, PSP
plates must be erased by exposing them to bright light before
using again.
Equipment
Both direct and indirect digital radiography use a dental x-ray
machine, an image receptor capable of capturing digital
information, a computer, and specialized software (Procedure
Box 9-1).
PROCEDURE 9-1
Procedure for obtaining digital images
Equipment preparation*
1. Turn on the computer. Using the keyboard or mouse, activate the computer exam window and select the
type of exam from the task bar (i.e., bitewings, periapicals, full mouth series).
2. Using the keyboard, type the patient identification information (i.e., name) and date of exam.
3. Wipe the sensor with an intermediate-level disinfectant approved by the sensor manufacturer. Place an
FDA-cleared plastic sheath over the sensor (Figures 9-9 and 9-10).
4. Place the sensor into the appropriate biteblock and attach to the holding device (Figures 9-7 and 9-11).
5. Turn on the x-ray machine and adjust exposure settings. Refer to the manufacturer’s recommendations for reducing film exposure settings by up to one-half those used for F-speed film-based
exposures.
(Continued )
*Follow the manufacturer’s instructions for your digital system. Only general guidelines concerning patient preparation and
sensor placement are included here.
102 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
PROCEDURE 9-1
Procedure for obtaining digital images (continued)
Patient preparation
1. Request that the patient remove objects from the mouth that can interfere with the procedure and remove
eyeglasses.
2. Adjust chair to a comfortable working level.
3. Adjust headrest to position patient’s head so that the occlusal plane is parallel to the floor and the midsagittal plane (midline) is perpendicular to the floor.
4. Place the lead/lead equivalent apron and thyroid collar on the patient.
5. Perform a cursory inspection of the oral cavity and note possible obstructions (tori, shallow palatal vault,
malaligned teeth) that may require an alteration of technique or placement of the sensor. Note the patient’s
occlusion to assist with aligning the sensor with the maxillary or mandibular teeth.
Exposure
1. Place the sensor intraorally into position (Figure 9-12).
2. Utilize the paralleling technique to position the sensor parallel to the long axes of the teeth of interest. Align the
tube head and PID to direct the central rays of the x-ray beam perpendicular to the sensor. Direct the central
rays to the middle (center) of the sensor to avoid conecut error (Figure 9-13).
FIGURE 9-11 Wired digital sensor being
placed into the image receptor holder.
FIGURE 9-9 Wireless sensor being covered with a disposable
plastic barrier for placement intraorally. (Courtesy of Schick
Technologies, Inc.)
FIGURE 9-10 Infection control. Wired digital
sensor being covered with a disposable plastic
barrier for placement intraorally.
CHAPTER 9 • DIGITAL RADIOGRAPHY 103
FIGURE 9-12 Sensor being placed intraorally.
PROCEDURE 9-1
Procedure for obtaining digital images (continued)
CCD (Charge-Coupled Device) or CMOS
(Complementary Metal Oxide
Semiconductor)
5. Wait for the image to appear on the computer
monitor and evaluate technique. If a technique
error has occurred that compromises diagnostic
quality and requires a retake, do the following:
a. Do not remove the sensor from the patient’s
oral cavity.
b. Request that the patient remain still, in position.
c. Observe the error and decide the corrective
action. For example, if a conecut error has
resulted in the posterior section of the image
being blank, the appropriate corrective action
would be to move the PID toward the posterior to align the central rays of the x-ray beam
to the center of the sensor.
d. Realign the PID to correct. To correct sensor
placement errors, request that the patient
open the mouth slightly, allowing you to perform the corrective action and then occlude
on the biteblock holding the sensor in this
new position.
e. Using the keyboard or mouse, activate the
retake window and make the exposure.
Repeat step 5 to produce a diagnostic quality
image.
PSP (Photostimuable Phosphor)
plate
5. Remove the sensor (plate) from the patient’s oral
cavity.
6. Remove the sensor from the holding device.
7. Remove the plastic barrier and clean and disinfect
sensor according to manufacturer’s instructions.
8. Place the plate in light-tight box until ready for
scanning (Figure 9-14) or place directly into the
laser scanner and activate (Figure 9-8).
9. Observe the image on the monitor and evaluate
technique. If a technique error has occurred that
compromises diagnostic quality, retake the exposure. You may choose to use another prepared
sensor or perform the following steps:
a. Erase the used sensor plate according to
manufacturer’s instructions.
b. Repeat the Equipment Preparation, Patient
Preparation, and Exposure steps.
10. If the image is satisfactory, remove the sensor
from the scanner and erase the used sensor plate
according to the manufacturer’s instructions. If
additional images are required, repeat the Equipment Preparation, Patient Preparation, and Exposure steps or use additional sensors.
11. Repeat steps 1 through 10 until all exposures are
acquired.
FIGURE 9-13 PID aligned with sensor held in place by
holder.
3. Using the keyboard or mouse, activate the sensor for exposure.
4. Depress the exposure button to expose the sensor.
(Continued )
X-ray Machine
Most digital x-ray systems can be used with existing dental
x-ray machines that have electronic timers capable of producing very short exposure times (Figure 9-15). Older x-ray
machines using impulse timers may need to be updated with
electronic timers for use with digital systems. An x-ray
machine adapted for digital radiography can still be used for
conventional film-based radiography. Dental x-ray machines
that are capable of producing low kilovoltage (60 kV), have low
millamperage (5 mA), and have a direct current (DC) curcuit
are ideally suited to digital radiography.
PROCEDURE 9-1
Procedure for obtaining digital images (continued)
FIGURE 9-14 Box to keep exposed PSP plates shielded
from bright light until scanned. (Courtesy of Air Techniques.)
6. If the image is satisfactory, remove the sensor
from the patient’s oral cavity. If additional images
are required, reposition the sensor for the next
exposure. (It may not be necessary to completely
remove the sensor from the patient’s oral cavity.
Depending on the cooperation of the patient,
the sensor may be positioned for the next image
without completely removing the sensor from
the oral cavity.)
7. Repeat steps 1 through 6 until all exposures are
acquired.
Following exposure
1. Remove the sensor from the holding device.
2. Remove the plastic barrier and clean and disinfect according to manufacturer’s instructions.
3. Save the patient’s exam in the archived files. Back up the file on the computer or supplemental storage
system. If required, print out a hard copy of the images.
104 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
Image Receptors
Both intra- and extraoral digital radiography use either a solid
state sensor (CCD or CMOS) or a photostimuable phosphor
(PSP) plate instead of film. CCD or CMOS intraoral sensors
may be wired, connected to the computer by a fiber optic cable
that records the generated signal or wireless. The cable may
vary in length, with popular lengths from 3 to 9 ft (1 to 3 m).
The shorter the cable, the more limited the range of motion.
Intraoral dental x-ray machines are available with a conveniently attached wired sensor (Figure 9-16). Wireless sensors
use a radio frequency to communicate with the computer and
CHAPTER 9 • DIGITAL RADIOGRAPHY 105
FIGURE 9-16 Digital radiography system with conveniently
attached sensor. (Courtesy of Planmeca.)
FIGURE 9-17 Wireless digital sensor in sizes similar to film.
(Courtesy of Schick Technologies, Inc.)
FIGURE 9-15 Digital radiography system. An existing dental xray unit being used with a digital imaging system.
are not connected by a cable (Figure 9-17). Eliminating the
wire from the sensor has potential benefits such as increased
mobility to position the sensor intraorally and increased
patient comfort from not having to occlude carefully to avoid
the wire. However, wireless sensors are usually thicker than
wired sensors, and the technology used to communicate with
the computer without being physically attached via a wire is
sensitive to other signals or noise in the area, such as from
other electronic devices being used in the vicinity. Digital
images are usually displayed on a computer monitor within
0.5 to 120 seconds after the sensor is exposed. The sensor
design is unique to the manufacturer. Sensors are available
with contoured edges and angled wire attachments (Figure 9-
18), and others have been reduced to just over 3 mm in width
(thickness), all characteristics designed to enhance patient
comfort during sensor placement intraorally.
FIGURE 9-18 Digital wired sensor. Note the contoured edges
and the angled attachment of the wire designed to facilitate placement
intraorally. (Courtesy of DEXIS, LLC.)
PRACTICE POINT
The ability to view a digital image immediately allows for
quick assessment of diagnostic quality and accurate correction of technique errors. For example, if a technique error
results in overlapping or conecut images, the operator can
make the necessary adjustments to the sensor placement or
tube head alignment without removing the sensor from the
patient’s mouth, greatly increasing the likelihood that the
corrective action will produce a quality image.
106 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
FIGURE 9-21 Computer with CRT monitor continue to
provide high quality image viewing. (Courtesy of DEXIS, LLC.)
FIGURE 9-20 Flat panel computer monitor. (Courtesy of DEXIS,
LLC.)
Intraoral PSP plates very closely resemble intraoral film
packets, and extraoral PSP plates are placed into a cassette
(without intensifying screens) in the same manner as extraoral
film (see Chapter 30). Intraoral PSP plates are thin and slightly
flexible. (Figure 9-7) Care should be taken to not bend the
plate, or damage will occur. There is no wire connection
directly to the computer. Each plate is exposed and then kept
protected from bright light until ready for the scanning step
(Figure 9-14). Each plate is then arranged in a special mount
and inserted into the laser scanner that is attached to the computer (Figure 9-8). The scanner uses a laser beam to convert the
digital signal contained as a latent image in the plate to a visible
image on a computer monitor. The scanning time can take
between 10 seconds to produce an image for a single periapical
radiograph and 5 minutes to produce a high-resolution panoramic
image. PSP plates must be erased by exposing to bright light
before they can be reused.
Both CCD and CMOS sensors and PSP plates are available
in the sizes that approximate the different sizes of an intraoral
film packet and extraoral film sizes, but PSP plates have a
greater variety of sizes available, including a size suitable for
exposing occlusal radiograph (Figure 9-3; see Chapter 17).
Computer
Digital radiography requires a computer to capture and a
monitor to view the image (Figure 9-19). The computer digitizes, processes, and stores information received from the sensor. The type and size of computer required depends on the
digital imaging software to be used. The computer must have
a large enough memory to store the images and be equipped
to support visual image displays on a monitor. Flat panel
monitors have largely replaced large cathode ray tube (CRT)
monitors (Figure 9-20). However, older CRT monitors, with
tested technology, continue to provide high-quality image
viewing (Figure 9-21). Technology has recently made available hand-held image viewers that store images, similar to a
portable hard drive. The images can then be transferred wirelessly to a nearby computer via radio waves for permanent
storage. When choosing a monitor with newer technology
such as liquid crystal display (LCD) or plasma displays, careful
FIGURE 9-19 Digital imaging system for use with a laptop
computer. (Courtesy of DEXIS, LLC.)
attention should be given to match the digital imaging system
with the monitor recommended by the manufacturer.
The computer may be connected to the Internet to allow
for electronic transfer of the images to insurance companies or
when referring to other health care specialists. Connecting a
printer to the computer will allow the operator to print out a
photo- or plain-paper copy for the patient record if desired.
Software
Manufacturers of digital radiographic systems provide software programs that when loaded onto the computer will allow
the operator to manipulate the images. Digital systems offer a
variety of features to aid in viewing and interpreting the
images. Some of the features offered by manufacturers of digital software include the following:
• Side-by-side displays of images. Allows the operator to
view and compare multiple images on the monitor at one
time. This feature is helpful when comparing current
images with images taken previously (Figure 9-20).
CHAPTER 9 • DIGITAL RADIOGRAPHY 107
• Magnification. Allows specific images to be magnified.
This feature is helpful when evaluating subtle changes
not easily detected by the unaided human eye.
• Density and contrast Changes can be made to image density and contrast without retaking the radiograph. For
example, when an image appears too light, this software
tool allows the operator to increase the image darkness.
• Measurement tools. Linear and angular measurements
can be obtained with a software “ruler” or measuring
feature. Measurement tools are useful in measuring the
length of root canals in endodontic therapy and for estimating periodontal bone levels.
• Charting. Software programs allow the operator to place
interpretive notes directly on the radiographic images
(Figures 9-22 and 9-23). An arrow or circle may be
drawn directly on an area of interest, in much the same
manner as an entry would be made on the patient’s paper
record or chart.
• Digital subtraction. This feature allows for comparison of
digitally stored images to detect changes over time or
prior to and after treatment interventions. Digital subtraction merges two radiographic images of the same area,
taken at different times. Merged together electronically,
those portions of the images that are alike (i.e., did not
change over time) will cancel each other out as they are
subtracted from each other. The portions of the images
where change occurred will stand out conspicuously. Digital subtraction eliminates distracting background information that is similar in both images and highlights the
changes (differences). Digital subtraction is an effective
method of measuring periodontal changes such as bone
loss or regeneration, assessment of implants, and healing
of periapical pathosis.
In the past, for digital subtraction to be effective, the
technique used to acquire the two images had to be closely
standardized. The positions of the sensor, the patient, and
the tube head all had to be the same for both images. This
was accomplished with fabrication of a custom biteblock
so that the patient could bite down in the same place with
each radiograph. Technological advances in software that
match gray values between subsequent images have made
digital subtraction easier to achieve.
• Artificial intelligence. Software technology continues
to find ways to improve the diagnostic yields from digital imaging. Predictions have been made that artificial
intelligence, programming a computer to make decisions regarding the diagnosis of the images acquired,
will one day be used to assist the practitioner with
reading and interpreting digital images. Possible uses for
artificial intelligence would be to develop computer
software to analyze bone around a dental implant to
determine if osseointegration (anchoring in bone)
has occurred or to analyze bone densities of the jaws
to screen for osteoporosis with a dental radiograph.
Although certainly very beneficial ideas, these uses of
artificial intelligence are still being studied.
FIGURE 9-22 Charting software allows the radiographer to
place notes directly on the image.
FIGURE 9-23 Charting software allows the radiographer to
place notes directly on the image. (Courtesy of Dentrix Dental Systems.)
PRACTICE POINT
A future possible use of artificial intelligence. Because the
computer can record more data than the human eye can
detect, in the future software features might be constructed
that alert the practitioner to subtle dental disease that may go
undetected. For example, the computer could be directed to
color all healthy enamel, with a certain level of density, yellow.
Any enamel density that falls below a certain established
healthy level could be colored purple. Therefore, when interpreting the image on the computer monitor, the practitioner
could easily identify the caries indicated by the purple areas.
108 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
FIGURE 9-26 Example of pixel size effect on the image.
FIGURE 9-25 Embossing. An example of a digital software
feature that can be used to manipulate the image to enhance
interpretation. (Courtesy of Dentrix Dental Systems.)
FIGURE 9-24 Reversing the gray scale. Digital software can change
the image’s radiopacities to radiolucencies and vice versa.
Characteristics of a Digital Image
The term digital image is used to distinguish it from an analog
image. An analog image can be compared to a painting that has
a continuous smooth blend from one color to another. A digital
image is like a mosaic, made up of many small pieces put
together to make a whole. The digital image is composed of
structurally ordered areas called pixels. Pixels, short for “picture
elements,” are tiny dots that make up a digital image. Each pixel
is a single dot in a digital image. The more pixels in an image, the
higher the resolution and the sharper the image. Studies continue
to compare different digital imaging systems and find that all
systems currently on the market produce acceptable images in
terms of spatial resolution and gray scale when compared to
intraoral film.
Spatial Resolution
The number and size of pixels determines the spatial resolution
of an image. When the number of pixels is low, the image
appears to have jagged edges and is difficult to see (Figure 9-26).
Spatial resolution is measured in terms of line pairs. A line pair
refers to the greatest number of paired lines visible in 1 millimeter (mm) of an image. For example, a resolution of 10 line
pairs/mm would mean that when 10 ruled lines are squeezed into
1 mm of an image, the individual lines can still be distinguished
from each other. The greater the spatial resolution in an image,
the sharper it looks.
Gray Scale
Gray scale refers to the number of shades of gray visible in an
image. The gray scale of a radiographic image is probably the
most important characteristic of a radiographic image. Detection and diagnosis of oral conditions depend on the gray scale
to provide the appropriate image contrast. The practitioner
most often relies on the radiograph’s contrast, its radiolucency
and radiopacity, to determine the presence or absence of disease. The ability to record subtle changes in the gray areas of
images improves diagnosis. Digital radiographic systems
claim the ability to produce up to 65,500 gray levels. However,
computer monitors can display only 256 gray levels. A number
stored for each pixel determines the number of shades of gray
• Other features. Other features of specialized software
promoted by manufacturers include reversing the gray
scale, embossing (Figures 9-24 and 9-25), and colorization, where different densities can be assigned a
different color value on the monitor. Some practitioners
find these features helpful aids to interpreting images,
whereas others view them as visual gimmicks because
these features currently do not have the power to take
the place of the dental practitioner. Interpreting digital
images with or without these features requires practice.
A practitioner must spend time developing the skills
required for interpreting digital images. Currently software cannot match the ability of a skilled practitioner
at interpreting dental disease and deviations from the
normal.
CHAPTER 9 • DIGITAL RADIOGRAPHY 109
visible (Figure 9-6). Each pixel has a number from 0 to 255,
representing pure black at 0 to pure white at 255 for a total of
256 gray levels in an image.
The human eye can distinguish only about 32 shades of
gray unaided. However, this does not necessarily mean that the
large range of gray scale captured by digital imaging systems is
wasted. When aided by the computer software features, which
can be used to enhance the gray levels, it may be possible to
detect changes that might be overlooked in film-based images.
The goal of digital imaging systems is to produce highquality diagnostic images. It is the combination of pixels,
spatial resolution, and gray scale that determines the quality
of the final image. Manufacturers are continuing to improve
the capability of digital equipment and software to aid in the
early detection of oral diseases.
PRACTICE POINT
The ability to increase or decrease digital image density will
not compensate for a severely under- or overexposed
image. For example, if the exposure setting is too low, the
resultant image will be too light. Often a light image will
not reveal such subtle changes as an early or incipient carious lesion. If the original image does not detect the radiolucency of the caries because it was underexposed (too
light), then merely darkening the image with the digital
software density control tool will not “put” the caries into
the picture. If it was not detected to begin with, the software will not reveal it.
Radiation Exposure
The advantages of digital imaging over film-based radiography
are significant (Table 9-2). One of these advantages that is often
a major benefit touted by digital imaging system manufacturers
is the reduction in radiation exposure to the patient. However,
with fast-speed intraoral film and the fast-speed extraoral film
and screen combinations (see Chapter 29) used today, the
actual radiation reduction may be 0 to 50%. Claims for up to
80% radiation reduction are most often accurate when the digital exposure is compared to slower D-speed film.
Solid-state CCD and CMOS digital imaging sensors are
more efficient at capturing x-rays than conventional dental
x-ray film and would most likely produce a bigger reduction
in exposure. For example, if a 12-impulse (0.2-second) exposure time is required for a radiograph taken with F-speed
intraoral film, the exposure time for this same image
acquired utilizing CCD or CMOS technology could possibly
be reduced to 6 impulses (0.1 second). However, the operator
should evaluate the actual result in practice and adjust the
exposure time as necessary to produce a diagnostically
acceptable image. This large of a reduction in radiation dose
may not be realized in practice with PSP plate technology, as
a low radiation exposure produces an increase in noise, an
electrical disturbance that clutters the image, at very low
exposure times. The practitioner will often increase the
exposure time to eliminate the noise. Additionally, PSP technology has the unique ability to produce an acceptable image
at longer exposure times. Overexposed PSP plates will not
alert the radiographer that too much radiation is being used
to produce the image. What this means in practice is that the
radiographer may be setting the exposure time higher than
needed.
There may be no radiation reduction realized when comparing extraoral CCD, CMOS, or PSP technology to extraoral
film-screen combinations. In fact, some extraoral systems
using PSP technology actually require an increase in radiation
exposure over film-screen radiographs.
Another important consideration when discussing radiation exposure is that studies have indicated a higher retake rate
and more exposures taken with direct digital imaging when
compared with film-based radiographs. Increased exposures
lead to increased patient radiation doses. Possible explanations
for this higher incidence of exposure with direct digital imaging include:
• The ease with which retakes can be immediately taken
without removing the sensor from the patient’s mouth.
• The real and the perceived radiation dose reduction expected
by digital imaging makes retakes seem easily justifiable.
• The recording dimensions of the sensors are smaller than a
film requiring multiple exposures of the same region.
• The size and rigidity of the sensor and the wire and plastic
infection-control barrier protruding from the oral cavity
make placement difficult, which leads to increased chance
of errors.
Although a reduction in radiation dose is an advantage of
digital imaging technologies, the International Commission on
Radiological Protection has recently indicated interest in investigating how some digital imaging systems arrive at radiation
reduction claims used in advertising. The radiographer should
critically evaluate a digital system to determine the radiation
dose reduction and be aware of the pitfalls that negate the beneficial reductions in radiation exposures.
Digital Imaging and Communications in
Medicine (DICOM)
When digital imaging began to replace film-based radiography, the medical community, where digital imaging is more
widely utilized, adopted the Digital Imaging and Communications in Medicine (DICOM) standard to allow different
digital systems to interface with each other. Exporting and
importing digital images can require complex steps and considerable computer knowledge. Without standards, system
compatibility will be an issue when digital images are transferred electronically between systems. The American Dental
Association Informatics Task Group has recommended that
the DICOM standard be used for dental imaging systems as
110 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
TABLE 9-2 Advantages and Limitations of Digital Radiography
ADVANTAGES LIMITATIONS
• Less radiation exposure
• Almost instantaneous viewing of the image
• Elimination of the photographic process and darkroom
• No generation of hazardous wastes such as used fixer and lead foils and
elimination of cost of disposal
• Elimination of darkroom processing errors
• Dark/light images may be improved with software to avoid reexposing the patient
• Images can be manipulated to enhance interpretation
• Improved grayscale resolution enhances contrast discrimination
• Software features such as charting and measuring tools assist with
interpretation and diagnosis
• Remote electronic consultation and sending of images
• Effective patient viewing that enhances discussion of treatment plan
and oral hygiene education (Figure 9-28)
• Long-term costs may be less when compared to costs associated
with purchasing film and processing chemicals
• The ease of retakes may result in excess radiation exposure
• Bulky, thicker sensor size (CCD and CMOS) and attached wire
may elicit patient complaints of discomfort or excite a gag reflex
• Plastic barrier sheaths placed over the sensor to maintain infection
control add additional bulk.
• Infection control requires careful adherence to manufacturer’s recommendations to avoid damage to the sensor. Infection control
must be maintained for computer keyboard and/or mouse
(Figure 9-27)
• Smaller overall sensor dimensions limits recording area. Additional exposures may be required to image an area entirely.
• Initial investment costs to convert from film-based radiography
• Special image receptor holders may need to be purchased
• Technology concerns, when to make the change from film-based
imaging, and what type of digital system to buy can be a difficult
decision
• Concern with reliability of digital imaging. Computer crashes, system malfunction, and computer viruses are real risks.
• Concern regarding a possible temporary inability to access the
images in the computer’s memory due to a computer glitch or
power failure that can delay patient treatment
• Archival storage (to keep patient records for the time required or
recommended by law) and backup storage (to protect files from
computer malfunction) need to be considered. Media used to store
the images will have to be updated continually to be accessible
over time.
• Learning curve required to read digital images on a computer monitor
• Viewing digital images will be restricted to the area where
the computer and monitor are located. (Although technology is
now producing portable viewers.)
• Although environmentally friendly in the short term, disposal of
broken, obsolete digital equipment is a concern.
FIGURE 9-27 Infection control. A disposable plastic barrier
protects the computer mouse.
FIGURE 9-28 Digital imaging system enhances patient
consult. (Courtesy of Gendex Dental Systems.)
CHAPTER 9 • DIGITAL RADIOGRAPHY 111
well. As manufacturers of digital imaging equipment adopt
the DICOM standard, the ease with which information can
be shared will improve. Currently manufacturers of dental
digital imaging systems are being encouraged to produce
systems that are compatible with each other.
Studies indicate that although the adoption of digital imaging by oral health care practices is increasing, it has not
replaced film-based radiography. Oral health care will most
likely continue to implement digital imaging into patient care
as improvements and standardizations of the technology continue. The oral health care practice of the near future will most
likely see a decreased use of film-based radiography.
REVIEW—Chapter summary
Digital radiography is a method of capturing a radiographic
image and displaying it on a computer screen. A solid-state
sensor or phosphor plate replaces film. Digital images have
no physical form, but exist as bits of information in a computer file. Film-based radiographs may be digitized by scanning or photographing to convert these analog images to
digital files.
Direct digital imaging replaces film with a solid-state
sensor, containing an electronic chip based on either chargecoupled device (CCD) technology or complementary metal
oxide semiconductor (CMOS) technology. Grids made up of
pixels arranged in columns and rows make up the sensor.
When x-rays strike the sensor an electronic signal is produced
and transmitted to a computer. The computer uses the x- and
y-coordinates and the gray value for each pixel to reconstruct the
image for viewing on a monitor. Indirect digital imaging
replaces film with a photostimuable phosphor (PSP) plate covered with a storage phosphor that captures the analog image
similar to the action of film. PSP sensor “stores” x-ray energy
until read later in a laser scanner.
Digital imaging requires the use of a conventional dental
x-ray unit, CCD or CMOS sensor or PSP plate, computer,
and special software. Ideal x-ray machines have an electronic
timer, low kVp, low mA, and direct current (DC). CCD and
CMOS sensors may be wired or wireless, with contoured
edges, and with angled wire attachments. PSP plates are not
attached to the computer with a wire. After exposure to
x-rays PSP plates must be kept away from bright light until
scanned. PSP plates are placed into a laser scanner that converts the digital signal to an image on a computer monitor.
PSP plates must be erased by exposing to bright light before
reusing.
All digital imaging systems require the use of a computer
with enough memory to run the special software and to store
the images generated. Consideration should be given to choosing a monitor that provides ease of reading and interpreting the
images. A printer attached to the computer will allow the operator to print hard copies of the radiographic images if desired.
Special software is required to run the digital radiographic
systems. Digital software packages allow the radiographer to
manipulate the image. Common features include the ability to
view multiple radiographic images on one screen, magnification, measuring, and charting tools. Digital subtraction is a
software process where two images are merged electronically,
canceling out like portions of the image and revealing changes.
Artificial intelligence may one day assist practitioners with
determining the presence of diseases.
The digital image is composed of pixels, short for picture
elements. Each pixel is a single dot in the digital image. The
number and size of pixels determines the spatial resolution and
the sharpness of the image. Spatial resolution is measured as
line pairs. A line pair refers to the number of paired lines visible
in 1 mm of an image. The greater the spatial resolution, the
sharper the image appears. Pixels also determine the gray scale
of the image. Each pixel has a number from 0 to 255, representing pure black at 0 to pure white at 255. The higher the gray
scale, the more likely the image is to record subtle changes in
the patient’s condition.
A major advantage of digital radiography is radiation
dose reduction, between 0 and 50% over film-based radiography. Other advantages include almost instant images, elimination of the darkroom and chemicals and hazardous wastes,
potential for improved interpretation through image manipulation, ability to transmit the images electronically, and
effective patient education. Limitations include too easily
making retakes that might lead to excess radiation exposure
and the need for digital system manufacturers to adhere to
DICOM (digital imaging and communications in medicine)
to allow transfer of images between different systems. Other
limitations include increased sensor width and decreased
recording area, initial costs to convert to digital imaging,
infection control protocols, issues with the technology
including memory storage, computer crashes, and interrupted
access to the data. There is a learning curve to gain proficiency with interpretation.
RECALL—Study questions
For questions 1 to 5, match each term with its definition.
a. analog
b. gray scale
c. line pair
d. pixel
e. spatial resolution
_____ 1. Discrete units of information that together
constitute an image.
_____ 2. The discernable separation of closely adjacent image details.
_____ 3. Refers to the number of paired lines visible in
1 mm of an image.
_____ 4. Relating to a mechanism in which data is represented by continuously variable physical
quantities.
_____ 5. Refers to the total number of shades of gray
visible in an image.
112 DENTAL X-RAY IMAGE RECEPTORS AND FILM PROCESSING TECHNIQUES
13. To maintain infection control, most manufacturers recommend that the sensor used in digital radiography be
a. packaged for steam sterilization and autoclaved.
b. disposed of after use, with biohazard wastes.
c. decontaminated with soap and water and disinfected
with a high-level disinfectant.
d. wiped with an intermediate-level disinfectant and
covered with a plastic barrier.
e. sanitized and immersed in a chemical sterilant.
14. List five features offered by digital software that can
be used to enhance the radiographic image.
a. ______________
b. ______________
c. ______________
d. ______________
e. ______________
15. The smaller the number of pixels in the image the
sharper the spatial resolution.
Each pixel stores a number representing a different
shade of gray.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
16. Digital radiography requires less radiation exposure to produce an image than film-based radiography because the
a. chemical processing steps are eliminated.
b. radiation used for digital imaging is different than
radiation used for film-based imaging.
c. image receptor (CCD or CMOS) is more sensitive to
x-rays than film.
d. computer can control the amount of radiation output
better than the radiographer.
17. Each of the following is true regarding digital radiography in comparison to film-based radiography
EXCEPT one. Which one is the EXCEPTION?
a. Provides a more legal document.
b. Less time is required to obtain a diagnostic image.
c. Eliminates film and chemical wastes.
d. Patient radiation is reduced 0 to 50 percent.
e. Software features enhance interpretation.
18. Each of the following is a disadvantage of digital radiography when compared to film-based radiography
EXCEPT one. Which one is the EXCEPTION?
a. Initial cost of setting up the system
b. Being able to magnify the image for diagnosis
c. Risk of computer crashes and lost files
d. Learning curve required to transfer interpretation
skills
e. Management of infection control
6. A digital radiographic image exists as bits of information in a computer file.
The computer converts this information into an image
that appears on the computer monitor.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
7. Digital radiography can be used for which of the following?
a. To detect caries
b. To monitor an endodontic procedure
c. To detect dental disease
d. All of the above
8. Digital radiography systems can be used for which of
the following?
a. Bitewing images
b. Periapical images
c. Panoramic images
d. All of the above
9. When a transparency scanner or digital camera is used
to convert an existing film-based radiograph to a digital
file, the process is called
a. digital radiography.
b. digital subtraction.
c. direct digital imaging.
d. digitization.
10. Each of the following is a digital image receptor
EXCEPT one. Which one is the EXCEPTION?
a. CCD
b. CMOS
c. XCP
d. PSP
11. Which of the following stores the x-ray energy until
later stimulation by a laser beam reads the electric signal and converts it into a digital image?
a. CCD
b. CMOS
c. XCP
d. PSP
12. Each of the following is necessary for digital radiography EXCEPT one. Which one is the EXCEPTION?
a. X-ray machine
b. Solid-state sensor or phosphor coated plate
c. Computer and monitor
d. Special software
e. Darkroom
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this
topic, see Thomson, E. M. (2012). Exercises in oral radiography techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson Education. Chapter 3, “Introduction to
digital imaging.”
REFERENCES
American Dental Association Council on Scientific Affairs.
(2006). The use of dental radiographs: Update and recommendations. J Am Dent Assn, 137, 1304–1312.
American Dental Association Standards Committee on Dental
Informatics. (2005). Implementation requirements for
DICOM in dentistry. Technical report no. 1023-2005.
Chicago: Author.
Farman, A. G., & Farman, T. T. (2005). A comparison of 18
different x-ray detectors currently used in dentistry. Oral
Surgery, Oral Medicine, Oral Pathology, 99, 485–489.
Francisco, E. F., Horlak, D., & Azevedo, S. (2010). The balance between safety and efficacy: Understanding the technology available that will produce high quality
radiographs while reducing patient risk to ionizing radiation. Dimensions of Dental Hygiene, 8, 26–30.
Horner, K., Drage, N., & Brettle, D. (2008). 21st century
imaging. London: Quintessence Publishing.
Palenik, C. J. (2004). Infection control for dental radiography.
Dentistry Today, 23, 52–55.
Van der Stelt, P. F. (2005). Filmless imaging: The uses of digital radiography in dental practice. Journal of the American Dental Association, 136, 1379–1387.
Van der Stelt, P. F. (2008). Better imaging: The advantages of
digital radiography. Journal of the American Dental Association, 139, 7S–13S
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis: Elsevier.
Williamson, G. F. (2005). Digital radiography in dentistry.
Journal of Practical Hygiene, 13–14.
CHAPTER 9 • DIGITAL RADIOGRAPHY 113
REFLECT—Case study
The oral health care practice where you are employed is considering purchasing a digital radiography system. Using the
Internet, search for companies that manufacture and sell dental
digital imaging products. From your research, choose two companies and compare their two products. Prepare an analysis to
help your practice decide what digital radiography system will
be the best choice. Contact the company for literature or additional information as needed to answer the following questions
about each of the products.
a. What are the names of the companies that manufacture
the products you chose to compare?
b. What are the names of the digital radiography systems
they manufacture/sell?
c. Do these digital systems have special computer requirements, or can they be used with the computer currently
in use at your practice?
d. What type of sensor does each offer? How are they
alike? How are they different?
e. What size sensors are available?
f. Are special sensor holding devices required for positioning the sensor intraorally? Where can these be purchased?
g. What are the infection control guidelines for the sensor?
Does the company make custom-sized plastic barriers
that fit the sensor?
h. Does software come with the purchase of the digital
radiography system? What features are included that
will allow the operator to enhance the image for interpretation?
i. Are the companies adhering to DICOM standards?
j. Does the company offer training for your oral health care
team to learn to operate the system? Is there training in
digital radiographic interpretation? Is there a fee for service and/or maintenance to the system after purchase?
k. Does the company offer articles or reviews of their
products by outside agencies that support their marketing claims?
l. Based on what you learned in this chapter, prepare a list
of advantages and limitations of each of these products.
m. Based on your research, which product would you recommend your practice purchase, and why?
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. State the purpose of infection control.
3. Describe the possible routes of disease transmission.
4. Identify conditions for the chain of infection and methods of breaking the chain.
5. Identify agencies responsible for recommending and regulating infection control guidelines.
6. List the personal protective equipment recommended for the dental radiographer.
7. Explain disinfection and sterilization.
8. Differentiate between semicritical and noncritical objects used during radiographic procedures.
9. Demonstrate competency in following infection control protocol prior to radiographic
procedures.
10. Demonstrate competency in following infection control protocol during radiographic
procedures.
11. Demonstrate competency in following infection control protocol after radiographic procedures.
12. Demonstrate competency in following infection control protocol for handling and processing
intraoral image receptors.
13. Demonstrate competency in following the infection control protocol when using an automatic
processor with a daylight loader attachment.
KEY WORDS
Acquired immunodeficiency
syndrome (AIDS)
Antiseptic
Asepsis
Barrier envelope
Contamination
Cross-contamination
Disinfect
Hepatitis B
Human immunodeficiency virus (HIV)
Immunization
Infection control
Intraoral dental film
Microbial aerosol
Pathogen
Personal protective equipment (PPE)
Protective barrier
Sepsis
Spatter
Standard precautions
Sterilize
Universal precautions
Infection Control
PART IV • DENTAL
RADIOGRAPHER FUNDAMENTALS
CHAPTER
10
CHAPTER
OUTLINE
 Objectives 114
 Key Words 114
 Introduction 115
 Purpose of
Infection
Control 115
 Guidelines
for Infection
Control 116
 Personal
Protective
Equipment (PPE) 117
 Handwashing 117
 Disinfection
and Sterilization
of Radiographic
Instruments
and Equipment 117
 Infection Control
Protocol for the
Radiographic
Procedure 119
 Infection Control
Protocol for
Radiographic
Processing 125
 Infection Control
for Processors
with a Daylight
Loader
Attachment 126
 Review, Recall,
Reflect, Relate 128
 References 129
CHAPTER 10 • INFECTION CONTROL 115
Introduction
The purpose of infection control procedures used in oral health
care is to prevent the transmission of disease among patients
and between patients and oral health care practitioners. Maintaining infection control throughout the radiographic procedure
can be challenging. The radiographer must possess a thorough
understanding of the recommended infection control protocols
that should be followed before, during, and after radiographic
exposures. The specific steps of these protocols require practice
to achieve competency in skilled handling of contaminated
radiographic equipment and supplies.
The purpose of this chapter is to identify infection control
terminology (Table 10-1), present the need for infection control
during radiographic procedures, and describe step-by-step
infection control procedures used in dental radiology.
Purpose of Infection Control
Infectious diseases may be transmitted from patient to oral
health care personnel, from oral health care personnel to
patient, and from patient to patient. The primary purpose
of infection control is to prevent the transmission of infectious diseases. Human beings have always lived with the
possibility of infection occurring through invasion of the
body by pathogens such as bacteria or viruses. A pathogen
is a microorganism capable of causing disease. Because of
the special risk these diseases carry, of particular concern
to the oral health care professionals are acquired immunodeficiency syndrome (AIDS), the human immunodeficiency
virus (HIV), viral hepatitis, including the highly infectious
hepatitis B virus (HBV), tuberculosis (TB), and herpesvirus
diseases.
Routes of infection transmission are
• Direct contact with pathogens in open lesions, blood,
saliva, or respiratory secretions.
• Direct contact with airborne contaminants present in
aerosols of oral and respiratory fluids.
• Indirect contact with contaminated objects or instruments.
Chain of Infection
For infection to occur, four conditions must be present
(Figure 10-1).
1. A susceptible (i.e., not immune) host
2. A disease-causing microorganism (pathogen)
3. Sufficient numbers of the pathogen to initiate infection
4. An appropriate route (portal of entry) for the pathogen to
enter the host
The purpose of infection control is to alter one of these four
conditions to prevent the transmission of disease.
Breaking the Chain of Infection
The chain of infection can be broken by:
1. Immunization of the susceptible host. The Centers for
Disease Control and Prevention (CDC) recommends that
dental personnel working with blood or blood-contaminated
substances be vaccinated for hepatitis B virus (HBV).
TABLE 10-1 Terminology
TERM DEFINITION
Antiseptic Agent used on living tissues to destroy or stop the growth of bacteria
Asepsis Absence of septic matter or freedom from infection (a means without; sepsis means infection)
Contamination Soiling by contact or mixing
‘Cross-contamination To contaminate from one place or person to another place or person
Disinfect The use of a chemical or physical procedure to reduce the disease-producing microorganisms
to an acceptable level on inanimate objects
Immunization The process of making someone immune to a disease
Infection control The prevention and reduction of disease-causing (pathogenic) microorganisms
Microbial aerosol Suspension of microorganisms that may be capable of causing disease produced during normal breathing and
speaking
Pathogen A microorganism that can cause disease (pathos means disease)
Protective barrier Any material that prevents the transmission of infective microorganisms
Sepsis Infection, or the presence of septic matter
Spatter A heavier concentration of microbial aerosols, such as visible particles from a cough or sneeze
Standard precautions A practice of care to protect persons from pathogens spread via blood or any other body fluid, excretion, or
secretion (except sweat)
Sterilize The total destruction of spores and disease-producing microorganisms, accomplished by
autoclaving or dry heat processes
Universal precautions Concept of infection control where the focus was on blood-borne pathogens. The all-inclusive “standard
precautions” has replaced this concept
116 DENTAL RADIOGRAPHER FUNDAMENTALS
BOX 10-1 The Centers for Disease Control and Prevention (CDC) Recommended
Infection-Control Practices for Oral Radiography
• Wear patient treatment gloves when exposing radiographs and handling contaminated image receptors.
• Use protective eyewear, mask, and gown as appropriate if spattering of blood or other body fluids is likely.
• Use heat-tolerant or disposable image receptor holding devices whenever possible (at a minimum, disinfect semicritical heat-sensitive
devices such as digital radiographic sensors, according to the manufacturer’s instructions).
• Clean and heat-sterilize image receptor holding devices between patients.
• Transport and handle exposed image receptors in an aseptic manner to prevent contamination of processing equipment.
• Use FDA-cleared protective barriers on digital radiographic image receptors.
Additionally, all oral health care workers should be vaccinated against influenza, measles, mumps, rubella, and tetanus.
2. Removing the pathogen. Use sterilization techniques
and/or protective barriers.
3. Reducing the sufficient numbers of pathogens. Use disinfection and sterilization techniques and/or protective barriers.
4. Blocking the portal of entry. Use personal protective
equipment (PPE) barriers such as protective clothes,
masks, eyewear, and gloves.
Guidelines for Infection Control
In the past, there may have been a tendency to use a double
standard in that certain infection control precautions were used
only if the patient was known to be infectious. It is a fact that
some patients are reluctant to admit their infectious condition.
Taking a thorough medical history and performing an oral
examination will not always identify potential infected patients.
Failure to use a single standard for all patients put everyone at
risk. Therefore, the use of standard precautions, where all
body fluids (except sweat) of all patients, whether known to
be infected or not, are assumed to be infected requires that
the necessary infection control procedures must be applied to
all patients.
The following government agencies are responsible for
developing, recommending, and/or regulating infection control
guidelines:
• Centers for Disease Control and Prevention (CDC)
Although it does not enforce regulations, the CDC is a
major influence in the development and recommendation
of guidelines for preventing disease and controlling
infection.
• Occupational Safety and Health Administration
(OHSA) Enforces regulations that protect the radiographer
from infection in the oral health care workplace.
• U.S. Food and Drug Administration (FDA) Regulates
oral health care products to ensure safe use. Although we
associate the FDA with drug testing, the products tested by
this agency include protective plastic barriers for use with
digital introral image receptors.
• U.S. Environmental Protection Agency (EPA) The EPA
is most often associated with its efforts to promote a clean
environment, but its regulation of waste products, chemicals, and disinfectants influence radiographic infection
control practices.
Each oral health care practice should have a written infection control policy that incorporates practical procedures that
are compatible with recommendations and regulations stated
by these agencies and are in accordance with state and local
regulations. The dentist (or designated personnel) has the
authority and the responsibility to see that the infection control
policy is correctly carried out. The CDC’s infection control
guidelines that directly relate to dental radiology are listed in
Box 10-1.
Proper portal
of entry
Susceptible
host
Numbers of pathogen sufficient
to cause infection
Pathogen
FIGURE 10-1 Chain of infection.
CHAPTER 10 • INFECTION CONTROL 117
Personal Protective Equipment (PPE)
Personal protective equipment or PPE (clothing, masks, eyewear, and gloves) worn by dental personnel acts as a protective
barrier (Figure 10-2). PPE prevents the transmission of infective microorganisms between oral health care practitioners and
patients.
Protective Clothing
Protective clothing, such as scrubs, gowns, and uniforms, provides protection from exposure to body fluids. Protective
clothing should be changed daily, or more frequently if soiled
or wet. Protective clothing should be removed before leaving
the treatment facility. Protective clothing should be laundered
separately with bleach to prevent contamination of other items.
Ideally, protective clothing should be laundered by a commercial biohazard laundry service that can safely remove the items
from the practice for laundering.
Masks
Although radiographic procedures are much less likely than other
dental procedures to produce spatter, protection from microbial
aerosols may be achieved through the use of a mask. Masks
should be changed when soiled or wet and between patients.
Protective Eyewear
Although radiographic procedures are much less likely than
other types of dental procedures to subject the radiographer to
physical eye accidents, the use of protective eyewear will protect against microbial aerosols and spatter. Types of protective
eyewear include glasses with side shields, goggles, and fullface shields. Protective eyewear must be washed with appropriate cleaning agents following treatment and as needed.
Gloves
Gloves must be worn at all times throughout the radiographic procedure. A variety of gloves is available for specialized uses. Sterile gloves are used for surgical procedures; medical examination
(nonsterile) gloves are used for most dental procedures, including
radiographic procedures; plastic overgloves have temporary
applications such as protecting or containing patient treatment
gloves; and utility gloves are appropriate for cleaning and disinfection. Medical examination gloves are made of latex or vinyl
material. Powdered gloves should be avoided, as the powder
residue can cause radiographic artifacts (see Chapter 18.) Gloves
should never be washed with soap or disinfected for reuse. Soap
may damage gloves in a way that would allow the flow of liquid
through undetected holes. Punctured, torn, or cut gloves should be
changed immediately. Gloves should always be changed and discarded between patients.
All unprotected surfaces not directly associated with the
procedure such as doorknobs to access the darkroom, unexposed film packets or unprotected digital sensors, or patient
records should not be touched with contaminated gloves.
Handwashing
Protective clothing, mask, and eyewear should all be in place
to prepare for handwashing prior to putting on medical examination gloves. Hands should be cleaned thoroughly before
and after treating each patient (before gloving and after removing gloves; see Procedure Box 10-1). Potentially infectious
pathogens can grow rapidly inside a warm, moist glove.
When hands are visibly dirty, they must be washed with
an antimicrobial soap and water. If hands are not visibly
soiled, an alcohol-containing preparation designed for reducing the number of viable microorganisms on the hands may be
used. All jewelry, including a watch and rings, should be
removed prior to handwashing. Long fingernails, false fingernails, and nail polish should be avoided, as these may harbor
pathogens and have the potential to puncture treatment gloves.
Handwashing is most effective when nails are cut short and
well manicured. Hands must be dried thoroughly before
putting on treatment gloves.
Disinfection and Sterilization of
Radiographic Instruments and Equipment
Prior to and following radiographic procedures, the treatment
area and the equipment must be cleaned and disinfected.
Cleaning instruments and equipment to prepare for sterilization and prior to disinfecting provides for effective infection
control. Cleaning, disinfection, and sterilization break the
chain of infection to prevent the transmission of infective
microorganisms.
Disinfection
Disinfection is the use of a chemical or physical procedure to
reduce the disease-producing microorganisms (pathogens) to
an acceptable level on inanimate objects. Spores are not necessarily destroyed. Disinfecting agents are too toxic for use on
living tissue, so are only used on clinical surfaces and on some
instruments that cannot be heat sterilized.
FIGURE 10-2 Radiographer preparing x-ray equipment.
Wearing PPE (barrier gown, protective eyewear, mask, gloves) to place
barriers to cover the x-ray tube head and PID. In the background, note
that image receptor holders have been assembled and placed on a plastic
barrier on the countertop.
118 DENTAL RADIOGRAPHER FUNDAMENTALS
FIGURE 10-3 Plastic barrier wrap covering x-ray control
panel.
PROCEDURE 10-1
Procedure for handwashing for radiographic procedures
1. Put on protective gown, eyewear, and mask.
2. Remove rings, wristwatch,* and other jewelry.
3. Wet hands with cool/tepid water and apply liquid antimicrobial soap.
4. Vigorously lather for 15 seconds; interlace fingers and thumbs, and move hands back and forth; work
lather under nails.
5. Rinse well, allowing water to run from fingertips.
6. Dry each hand thoroughly with a separate paper towel.
7. Unless equipped with a foot pedal, turn off the water by placing a clean paper towel between clean, dry
hand and the faucet.
*Wristwatch may be replaced after handwashing as long as it will remain protected under the gown or covered with the
glove during the procedure.
EPA-registered disinfectants are classified as:
• High-level disinfectant. Chemical germicides inactivate
spores and can be used to disinfect heat-sensitive semicritical dental instruments.
• Intermediate-level disinfectant. Chemical germicides
labeled as both hospital-grade disinfectants and tuberculocidals. Examples are iodophors, phenolics, and chlorinecontaining compounds. These do not destroy spores.
• Low-level disinfectant. Chemical germicides labeled as
hospital-grade disinfectants. Cannot destroy spores, tubercle bacilli, or nonlipid viruses.
Because of their corrosive and toxic properties, the CDC
discourages the use of disinfectants. Additionally, disinfectants
have the potential to affect electrical connections, so directly
spraying or saturating the x-ray control panel, dials, or exposure
button may damage the x-ray machine. Therefore, protective barriers should be used whenever practical. Plastic wrap or barriers
are commonly used to cover those surfaces most likely to be contaminated during the radiographic procedure such as the PID and
tube head, control panel, exposure switch, and counter surfaces
(Figures 10-2 and 10-3). Surfaces not covered must be cleaned
and disinfected after the radiographic procedures are completed.
Sterilization
Sterilization is the total destruction of spores and diseaseproducing microorganisms. Sterilization is usually accomplished
by autoclaving or dry heat processes. Ideally, all equipment and
instruments should be sterilized. Acceptable methods of sterilization in the oral health care facility include
• Steam under pressure (steam autoclave)
• Dry heat
• Heat/chemical vapor (chemical autoclave)
• EPA-registered high-level disinfectant
Classification of Objects Used in Radiographic
Procedures
Radiographic instruments and clinical contact surfaces are classified according to their risk of transmitting infection and to the
need to sterilize between uses (Table 10-2). All surfaces that
will be used for or contacted during the procedure must be
cleaned and disinfected or sterilized according to the object’s
classification as critical, semicritical, or noncritical.
• Critical instruments are those used to penetrate soft tissue or bone. Examples are needles, forceps, and scalers.
Critical objects must be discarded or sterilized after each
use. No critical instruments or equipment are used in
radiographic procedures.
• Semicritical instruments are those that contact oral mucosa
without penetrating soft tissue or bone, such as intraoral
dental mirrors. Radiographic image receptor holding
CHAPTER 10 • INFECTION CONTROL 119
TABLE 10-2 Risk of Transmitting Disease Classification of Objects Used in
Radiographic Procedures
CATEGORY RADIOGRAPHIC EQUIPMENT STERILIZE OR DISINFECT OR DISCARD
Critical None N/A
Semicritical Image receptor holders Sterilize or use disposable devices
Digital sensor/phosphor plate*
Panoramic biteblocks
‘Noncritical/clinical contact
surface
X-ray tube head, PID, support arms
Exposure controls**
Clean and disinfect with an appropriate
level EPA-registered disinfectant
Lead/lead-equivalent apron and thyroid collar
Countertop in operatory and darkroom
Extraoral radiographic machine parts such as chin/forehead rest, side head positioner guides; cephalostat
Some phosphor plates can be gas sterilized, but most digital radiographic sensor manufacturers recommend against sterilizing these fragile devices.
Instead, wipe with an appropriate level EPA-registered disinfectant before covering with an FDA-cleared barrier and wipe again following barrier removal
after the procedure. Consult manufacturer’s recommendations.
Liquid disinfectants may damage the electrical components of the dental x-ray control panel. Therefore, most dental x-ray equipment manufacturers
recommend covering the control panel exposure dials and exposure button with an FDA-cleared barrier. Consult manufacturer’s recommendations.
**
*
devices and the bite block of the panoramic x-ray machine
(see Chapter 30) fall into this category. Semicritical instruments must be sterilized after use or discarded. Although
most image receptor holders can be sterilized or are disposable, some devices on the market may be heat sensitive.
Although heat-sensitive semicritical instruments may be
sterilized under certain conditions with EPA-registered
chemicals classified as high-level disinfectant, using
instruments that can be heat-sterilized or that are disposable is recommended.
• Noncritical instruments and clinical contact surfaces are
those devices and surfaces of the treatment area that may
contact intact skin or may become contaminated by microbial aerosols or spatter, but do not come into contact with the
mucous membranes. Examples include the lead apron, the
PID (position indicating device), and the chin rest and head
positioner guides of extraoral radiographic equipment
such as the panoramic x-ray machine. (See Chapter 30.)
Other clinical contact surfaces that may become contaminated during the procedure include the x-ray machine tube
head, the exposure button, and the countertop. Noncritical
instruments and clinical contact surfaces can be disinfected using EPA-registered intermediate- or low-level
disinfectants.
Infection Control Protocol for the
Radiographic Procedure
Using standard precautions, infection control procedures for
radiography assume that all body fluids (except sweat) of all
patients have the potential to be infectious. Infection control
procedures for exposing radiographs can be divided into three
categories: prior to, during, and after exposure.
Infection Control Prior to the Radiographic Procedure
(Procedure Box 10-2)
PREPARE THE TREATMENT AREA All treatment area surfaces
likely to come in contact with the patient either directly or indirectly must be sterilized, or cleaned and disinfected, and/or covered with a protective barrier. All supplies, image receptors, and
holding devices should be obtained and placed for easy access
during the procedure.
Intraoral dental film inside its original packaging is not
sterile, but rather is considered “industrially clean,” which
means that it is not expected to be contaminated with pathogens.
To avoid contamination prior to use, intraoral film packets
should be dispensed just prior to use in disposable containers
such as a paper cup or small envelope. The film packets must be
handled carefully to prevent cross-contamination. Because they
are heat-sensitive, film packets cannot be sterilized, and the liquid saturation required for disinfecting is not recommended.
Another method used to prevent the transmission of microorganisms by the film packet is to use barrier envelopes. Barrier
envelopes are commercially available for film sizes #0, #1, and
#2. Film packets placed and sealed in these plastic envelopes
(Figure 10-4) are protected from contact with fluids in the oral
cavity during exposure. Film packets already sealed in barrier
plastic envelopes by the manufacturer are also available commercially. Following removal from the patient’s oral cavity, the barrier envelope is opened (Figure 10-5) and discarded appropriately.
The film packet that was sealed in the barrier envelope may now
be handled with clean hands (or new gloves) to complete the processing procedure.
DIGITAL IMAGE RECEPTORS Phosphor plates used to obtain
radiographic images digitally (see Chapter 9) must also be
sealed in plastic barrier envelops prior to use intraorally
120 DENTAL RADIOGRAPHER FUNDAMENTALS
PROCEDURE 10-2
Infection control prior to the radiographic procedure
1. Follow handwashing described in Procedure Box 10-1 or apply an antiseptic hand rub following the manufacturer’s directions for use.*
2. Put on utility gloves.
3. Clean and disinfect with appropriate disinfectant all surfaces that will come in contact either directly or
indirectly with the patient. See the following list:
a. PID
b. X-ray tube head
c. Tube head support arms and handles
d. Exposure button**
e. Control panel dials (impulse timer, kVp, and MA controls)**
f. Treatment chair, including headrest, back support, arm rests, body and back of the chair
g. Bracket table or countertop or other clinical contact surfaces that will be used during the procedure
h. Digital sensor or phosphor plates
i. Lead/lead equivalent apron/thyroid collar
4. Wash, dry, and remove utility gloves. Disinfect.
5. Wash hands with an antimicrobial soap or apply an antiseptic hand rub.*
6. Put on clean overgloves.
7. Obtain plastic barriers and cover all surfaces that will come in contact either directly or indirectly with the
patient. See the following list:
a. PID
b. X-ray tube head (Figure 10-2)
c. Tube head support arms and handles
d. Exposure button
e. Control panel dials (impulse timer, kVp, and MA controls; Figure 10-3)
f. Treatment chair including headrest, back support, arm rests, body and back of the chair
g. Bracket table or countertop or other clinical contact surface that will be used during the procedure
h. Computer keyboard and mouse (digital imaging)
i. Digital sensor or phosphor plates
j. Lead/lead equivalent apron/thyroid collar (optional)
k. Film packets (optional; Figure 10-4)
l. Digital sensors or phosphor plates
8. Obtain radiographic supplies. See the following list:
a. Image receptors (film packets/digital sensors/phosphor plates)
b. Sterile or disposable image receptor holding devices
c. Film mount (for film-based radiography)
d. Disposable paper/plastic cup
e. Paper towels
f. Miscellaneous supplies (i.e., cotton rolls, extra disposable image receptor holding devices)
9. Place the film mount under the plastic barrier on the counter work space.
CHAPTER 10 • INFECTION CONTROL 121
(Figure 10-6). The same careful handling recommended for
film packets should be followed to avoid cross-contamination.
Solid-state digital sensors cannot withstand sterilization procedures, so they must be wiped with disinfectant and covered
with a plastic barrier prior to placing intraorally (Figure 10-7).
There are many sizes and styles of plastic barriers for
phosphor plates and plastic sheaths for digital sensors
designed to protect these image receptors from contamination (see Figures 9-9 and 9-10). However, these barriers are
subject to tearing and are not always totally protective. The
use of an FDA-cleared disposable plastic barrier will help
decrease the risk of a breach in asepsis. Additionally, wiping
the sensor or phosphor plate with an appropriate level disinfectant prior to and after placement of the plastic barrier is
usually recommended (Figure 10-7). Although the manufacturer’s instructions for maintaining infection control should
FIGURE 10-4 Barrier envelope. (left) Film available from
manufacturer sealed in barrier packet ready for use. (right) Barrier
envelopes may be purchased separately.
FIGURE 10-5 Opening the barrier envelope. A steady pull is
used, allowing the film packet to drop into a clean cup.
be consulted to prevent damage to the sensor or phosphor
plate, options for substitutes for harsh chemical disinfection
and sterilants are not usually offered. Infection control techniques for digital radiography have not yet been perfected
and remain a problem to be solved through rigorous testing
as this technology evolves.
A laser scanning device (for use with phosphor plates) and
a computer keyboard and/or mouse (for use with solid state
sensors) must be operated to produce images and activate the
exposure sequence, so these should also be covered with a plastic barrier that is changed between patients (see Figure 9-28).
As digital technology advances, infection control protocols are
expected to advance as well. In fact, medical grade computer
monitors that have glass fronts that are easy to clean and can be
disinfected are becoming increasingly available for mounting
in a dental operatory in close proximity to patient treatment.
PROCEDURE 10-2
Infection control prior to the radiographic procedure (continued)
10. Place the film packets on the plastic barrier placed over the film mount.
11. Saturate a folded paper towel with disinfectant and place next to the film mount on top of the plastic barrier.
12. Prepare antimicrobial mouth rinse for patient use prior to procedure.***
*When hands are visibly dirty, they must be washed with an antimicrobial soap and water. If hands are not visibly soiled, an
alcohol-containing preparation designed for reducing the number of viable microorganisms on the hands may be used.
Refer to manufacturer’s recommendations for use.
**Exposure switches and control panel dials may be damaged by the use of a disinfectant solution. Manufacturer’s recommendations should be consulted. Saturating a paper towel with disinfectant and then carefully wiping the switches may be
an option. Infection control may also be achieved by protecting with a plastic barrier (Figure 10-3). (Foot pedal exposure
switches do not require disinfection.)
***Scientific evidence does not indicate that preprocedural mouth rinsing prevents the spread of infections. However,
antimicrobial mouth rinses (e.g., chlorhexidine gluconate, essential oils, or povidone-iodine) can reduce the number of
microorganisms the patient might release in the form of aerosols or spatter.
122 DENTAL RADIOGRAPHER FUNDAMENTALS
Protocol During the Radiographic Procedure
(Procedure Box 10-3)
PATIENT PREPARATION The patient is seated after the treatment area is prepared and supplies are readied. The patient may
be asked to rinse with an antimicrobial mouth rinse to reduce oral
microorganisms that contribute to infectious aerosols. The
patient is draped with the lead/lead-equivalent apron and thyroid
collar. Care must be taken when making adjustments to the treatment chair and headrest so as not to compromise the infection
control process. Covering the treatment chair controls with a
plastic barrier will aid in the infection control process.
Any object that may interfere with the procedure, such as
patient’s eyeglasses, dentures, etc., should be removed by the
patient and placed in an area so they do not become contaminated and do not contaminate other objects.
DURING EXPOSURES Once the procedure has begun, care
must be taken to touch only covered surfaces. The best way to
minimize contamination is to touch as few surfaces as possible.
If drawers or cabinets must be opened to retrieve additional supplies, or the radiographer must leave the treatment area during
the procedure, the patient treatment gloves should be removed
and the hands washed. New treatment gloves must be used when
restarting the procedure. Overgloves may also be used, if treatment must be interrupted. The patient treatment gloves may be
rinsed briefly with water only (do not use soap, as it will compromise the integrity of the protection), dried, and covered with
plastic overgloves. To restart the exposure procedure, the overgloves are removed.
FILM PACKETS AND PHOSPHOR PLATES Immediately after
removing the image receptor from the oral cavity it should be
swiped across a disinfectant-soaked paper towel that was prepared during setup to remove excess saliva (Figure 10-8). The
film should next be dropped into a paper cup without touching
the outside edges of the cup. The cup will serve as the transport
method of getting the contaminated film packets safely into the
darkroom. Phosphor plates should be dropped into the containment light-tight box for transport to the laser scanner (see
Figure 9-14).
If using a film packet covered with a plastic barrier, the
infection control protocol is the same as that used for phosphor
plates. Hold the image receptor over the cup designated for
containment (film packets) or the containment light-tight box
(phosphor plates) and tear open the plastic barrier (Figure 10-
5), allowing the sealed image receptor to drop into the containment receptacle untouched by gloved hands. Once all the image
receptors are exposed and opened in this manner, the containment cup of film packets can be transported to the darkroom for
processing, and the containment box of phosphor plates can be
transported to the location of the laser scanner.
DIGITAL IMAGE RECEPTORS The plastic barrier placed prior
to use will remain in place until the completion of all exposures. Excess saliva should be removed with a paper towel.
When the procedure is complete, the plastic barrier should be
carefully removed to avoid tearing and contaminating the sensor (Figure 10-9).
IMAGE RECEPTOR HOLDERS The image receptor holding
devices should be transferred from a barrier-protected surface
to the patient’s oral cavity and then back to the same covered
surface. Never place contaminated instruments on an uncovered surface.
FIGURE 10-6 Barrier envelopes for phosphor plates. (Courtesy
of Air Techniques, Inc.)
FIGURE 10-7 Using a disinfectant wipe to prepare a digital
sensor prior to placing plastic barrier.
[PROCEDURE 10-3
Infection control during the radiographic procedure
CHAPTER 10 • INFECTION CONTROL 123
1. Follow handwashing described in Procedure Box 10-1 or apply an antiseptic hand rub following the
manufacturer’s directions for use.
2. Put on patient treatment gloves.
3. Place overgloves over patient treatment gloves.
4. Place the lead/lead equivalent apron and thyroid collar on the patient.
5. Remove overgloves and place on the counter.
6. Assemble the image receptor into the appropriate holding device, place intraorally, and position the x-ray
tube head and PID.
7. Depress the exposure button, and remove the image receptor and holding device from the patient’s oral
cavity.
8. Remove the image receptor from the holding device.
9. Film or phosphor plate: swipe the image receptor across the disinfectant-soaked paper towel and drop
into the containment cup/box.*
Digital sensor: remove excess saliva with paper towel.
10. Proceed to place and expose all radiographs in this manner.
11. If additional supplies are needed that requires the operator to contact noncovered surfaces or the procedure must otherwise be interrupted:
a. Rinse treatment gloves with plain water (no soap) and dry.**
b. Place overgloves over treatment gloves.
c. To restart the procedure, remove overgloves.
*Phosphor plates and film packets sealed in plastic barrier envelopes should be opened immediately using aseptic technique.
**If the procedure must be interrupted, the treatment gloves may be removed and discarded and the hands washed. Prior to
restarting the procedure, the hands should be washed again and new treatment gloves put on.
FIGURE 10-8 Remove saliva. Radiographer is swiping the film
packet across a disinfectant-soaked paper towel prior to dropping the
film into the containment cup.
Protocol After the Radiographic Procedure
(Procedure Box 10-4)
Once the radiographic procedure is complete, patient gloves
should be removed and discarded, and hands washed with an
antimicrobial soap or an alcohol-based hand rub. The lead/lead
equivalent apron with thyroid collar can now be removed from the
patient and the cup containing the exposed films, carried to the
darkroom for processing or phosphor plates to the laser scanner.
Once the patient is dismissed, the radiographer should place
utility gloves on for cleaning and disinfecting the treatment area.
With utility gloves on, the image receptor holders are cleaned and
prepared for sterilization according to the manufacturer’s recommendations. Usually these holders can be washed with soap and
water or ultrasonic cleaned in detergent and dried and packaged in
an autoclave bag for sterilization. All disposable holders and other
disposable supplies, such as cotton rolls, should be discarded.
Dispose of all contaminated items according to local and state
regulations. Plastic barriers, including those covering the digital
sensor, should be carefully removed, making sure not to touch the
surfaces underneath. The digital sensor should be wiped with a
1. Rinse, remove, and discard patient treatment gloves and wash hands. Follow handwashing described in
Procedure Box 10-1 or apply an antiseptic hand rub following the manufacturer’s directions for use.
2. Remove lead/lead equivalent apron with thyroid collar and dismiss patient.
3. Put on utility gloves.
4. Prepare and package image receptor holders for sterilization.*
5. Sterilize image receptor holders according to manufacturer’s recommendations.
6. Discard all disposable contaminated items (i.e., disposable image receptor holders, paper towels, cotton
rolls).
7. Remove and discard all plastic barriers.
8. Clean and disinfect any uncovered surface.
9. Wipe digital sensor/phosphor plates with disinfectant.
10. Clean and disinfect lead/lead equivalent apron and thyroid collar.
11. Wash, dry and remove utility gloves. Disinfect.
12. Wash hands with antimicrobial soap. Follow handwashing described in Procedure Box 10-1 or apply an
antiseptic hand rub following the manufacturer’s directions for use.
*Refer to manufacturer’s recommendations for cleaning with soap and water or ultrasonic detergents.
PROCEDURE 10-4
Infection control after the radiographic procedure
124 DENTAL RADIOGRAPHER FUNDAMENTALS
FIGURE 10-9 Removing the plastic barrier from a
digital sensor. Removal of sticky-backed biteblocks is easier
if the image receptor holder remains in place attached to the
barrier. (A) Grasping the holder in the palm of one hand, press
on the sensor with the thumb. (B) As the sensor begins to
B move, guide it out of the plastic sheath with the other hand.
CHAPTER 10 • INFECTION CONTROL 125
disinfectant. All areas not covered should be cleaned and disinfected, including the lead/lead equivalent apron and thyroid collar.
When cleanup is complete, utility gloves should be washed with
soap and water, removed, and disinfected. The radiographer
should wash hands again after removing utility gloves.
Infection Control Protocol
for Radiographic Processing
Film-handling procedures for processing will depend on whether
or not barrier envelopes are used to protect the film packets.
Film Handling Without the Use of Barrier Envelopes
(Procedure Box 10-5)
The use of commercial plastic film barrier envelopes protects the
film packet while in the oral cavity. Once the film packet is aseptically removed from the barrier envelope, it is safe to handle with
clean, dry hands or clean treatment gloves. Although readily available, the use of protective plastic envelopes for intraoral films is not
universal. For this reason, it is important that the dental radiographer be skilled at handling film packets without barrier envelopes.
Once the film packets have been transported to the darkroom,
the operator must put on treatment gloves and proceed to open the
PROCEDURE 10-5
Infection control for processing radiographic films without barrier envelopes
1. Transport the contaminated film packets to the darkroom in the paper/plastic cup used for containment.
2. Place one paper towel on the counter work space, and place the cup with contaminated films on this
paper towel.
3. Place a second paper towel on the counter work space adjacent to the first paper towel and designate it
as the uncontaminated area.
4. Secure darkroom door.
5. Turn off white overhead light and turn on safelight.
6. Put on clean patient treatment gloves.
7. Open each film packet (Figure 10-10).
a. Peel back the outer plastic/paper wrap using the tab on the back of the packet.
b. Grasp the black paper with film sandwiched in between, and pull straight out.
c. Hold the black paper–film assembly over the designated uncontaminated paper towel and pull out slowly.
d. Allow the film to drop out onto the paper towel. Do not touch the film with contaminated patient
treatment gloves.
8. Drop the contaminated film packet outer plastic/paper wrap, black paper, and lead foil onto the contaminated paper towel.
9. Repeat steps 7 and 8 until all film packets have been opened.
10. Remove and discard patient treatment gloves and wash and dry hands.
11. With clean, dry hands, grasp by the edges and place films into the automatic processor feeder slots or
load onto manual processing film racks for processing.
12. When the films are safely in the automatic processor, or the manual processing cover is securely closed,
turn on the overhead white light.
13. Put on utility gloves.
14. Separate lead foil from film packets and discard into lead recycling waste.
15. Gather the contaminated paper towel with all waste and discard appropriately.
16. Clean and disinfect the counter work space and any other area that may have been touched during the
procedure.
17. Wash, dry, and remove utility gloves. Disinfect.
18. Wash and dry hands.*
*If hands are not visibly soiled, an alcohol-containing preparation designed for reducing the number of viable microorganisms on the hands may be used. Refer to manufacturer’s recommendations for use.
126 DENTAL RADIOGRAPHER FUNDAMENTALS
Infection Control for Processors with a
Daylight Loader
Daylight loader attachments on automatic processors have
light-tight flaps or sleeves that allow the radiographer’s hands
to slide through to access the intake slots on the front of the
processor. A processor equipped with daylight loader attachment does not require a darkroom. Daylight loader attachments require special infection control considerations
(Procedure Box 10-6). With strict adherence to proper infection control protocol, the use of daylight loaders should not
compromise infection control. The radiographer should be discouraged from shortcutting these procedures, which would
pose a health threat not only for the operator, but also for others who use the device.
The key to infection control using the daylight loader is
to open the light-filter cover when placing and removing
items (Figure 10-11). Never attempt to push items through the
light-tight baffles. After removing the light-filter cover from
the daylight loader, the cup containing the contaminated film
packets, an additional, uncontaminated cup, and unused treatment gloves should be placed inside the unit on top of a plastic or paper towel barrier. With the light-filter cover closed,
clean, dry hands can be slid through the light-tight baffles to
packets aseptically (Figure 10-10). Skill in this procedure will
help avoid dropping and potentially losing films in the darkroom’s
dim lighting. In addition, the radiographer should be able to open
all film packets, especially when processing a full mouth series, in
two minutes or less to avoid prolonged exposure of the film to
safelight. Prolonged exposure to light, even if it is called safelight,
increases the risk of film fog (see Chapter 8.) After the last film is
placed into the automatic processor or into the manual processing
tank and the cover is closed, the darkroom must be cleaned and
disinfected. Discard all materials appropriately, including the film
packets, lead foil (see Chapter 20), and any materials used as protective barriers. Clean and disinfect darkroom counter surfaces
and/or any other areas touched by gloved hands.
Film Handling with the Use of Barrier Envelopes
and Phosphor Plates
Although protected while in the oral cavity, film packets and
phosphor plates that were secured in barrier envelopes must
still be handled carefully. Once these image receptors have
been removed from the plastic barrier envelopes, they may be
handled with clean, dry hands, or with new treatment gloves.
To avoid damage, handle these image receptors by the edges.
The use of powdered gloves should be avoided because powder
residue will leave artifacts on the radiograph (see Chapter 18).
A B
C D
FIGURE 10-10 Steps for removing film from packet without touching film with contaminated gloves. (A) Open the
film packet by lifting the plastic tab. (B) Locate the folded tab of black paper and grasp with finger and thumb. (C) Gently pull on
the black paper tab, sliding the film out of the packet. (D) Allow the film to drop out onto the plastic or paper towel barrier placed
on the counter. Separate the lead foil from the rest of the packet and dispose of all materials appropriately.
PROCEDURE 10-6
Infection control for an automatic processor with a daylight loader attachment
1. Transport the contaminated film packets to the automatic processor equipped with the daylight loader
attachment.
2. Obtain a clean pair of patient treatment gloves.
3. Open the light-filter cover and line the floor of the daylight loader compartment with a clean paper towel
or plastic barrier. Designate one side as the contaminated side and the other side as uncontaminated.
4. Place the cup with the film packets on the contaminated side and a clean pair of patient treatment gloves
on the uncontaminated side inside the daylight loader.
5. Close the light-filter cover.
6. Slide clean, dry hands through the light-tight baffles.
7. Once inside, put on the pair of clean patient treatment gloves.
8. Open each film packet (Figure 10-10).
a. Peel back the outer plastic/paper wrap using the tab on the back of the packet.
b. Grasp the black paper with film sandwiched in between and pull straight out.
c. Allow the film to drop onto the paper towel or plastic barrier on the uncontaminated side of the
floor of the compartment. Do not touch the film with contaminated client gloves.
9. Drop the contaminated film packet onto the paper towel on the contaminated side of the floor of the
compartment.
10. Repeat steps 8 and 9 until all film packets have been opened.
11. Remove patient treatment gloves and place on the contaminated side of the paper towel on the floor of
the compartment.
12. With clean, dry hands, grasp by the edges and place films into the automatic processor feeder slots for
processing.
13. When the films are safely in the automatic processor, remove ungloved hands through the light-tight baffles.
14. Wash and dry hands.*
15. Put on utility gloves.
16. Open the light-filter cover and separate the lead foil from the film packets, and dispose of appropriately.
Remove the cup, contaminated film packet outer plastic/paper wrap, and paper towels or plastic barrier
and discard appropriately.
17. Clean and disinfect the inside of the compartment.
18. Wash, dry and remove utility gloves. Disinfect.
19. Wash and dry hands.*
*If hands are not visibly soiled, an alcohol-containing preparation designed for reducing the number of viable microorganisms on the hands may be used. Refer to manufacturer’s recommendations for use.
CHAPTER 10 • INFECTION CONTROL 127
128 DENTAL RADIOGRAPHER FUNDAMENTALS
semicritical or noncritical and clinical contact surfaces, and they
should be sterilized or disinfected accordingly. Specific step-bystep infection control procedures must be performed prior to,
during, and after the radiographic procedure.
Recommended step-by-step procedures for handling
image receptors with and without barrier envelopes is presented. Darkroom infection control protocol must be mastered
to prevent lost or fogged radiographs. Strict infection control
protocol must be followed when using an automatic processor
with a daylight loader.
RECALL—Study questions
1. The purpose of infection control is to prevent the transmission of disease between
a. patients.
b. patient and operator.
c. operator and patient.
d. All of the above
2. Each of the following will break the chain of infection
EXCEPT one. Which one is the EXCEPTION?
a. Use of a digital sensor
b. Use of personal protective equipment
c. Sterilizaton of radiographic equipment
d. Immunization of oral health care practitioners
3. An approach to infection control that states that the
body fluids (except sweat) of all patients should be
treated as if infected is
a. universal precautions.
b. standard precautions.
c. protective barriers.
d. cross-contaminations.
4. Which of these agencies develops and provides recommendations for adoption of infection control guidelines, but does not act as an enforcer of these
guidelines?
a. Centers for Disease Control and Prevention (CDC)
b. Occupational Safety and Health Administration
(OHSA)
c. U.S. Food and Drug Administration (FDA)
d. U.S. Environmental Protection Agency (EPA)
5. List four items of PPE (personal protective equipment)
recommended for the dental radiographer:
a. ______________
b. ______________
c. ______________
d. ______________
6. The use of a chemical or physical procedure to reduce
the disease-producing microorganisms to an acceptable
level on inanimate objects is the definition of
a. asepsis.
b. antiseptic.
c. disinfection.
d. sterilizaton.
access the unit. With hands inside, the radiographer will place
the treatment gloves on, open the film packets, separate the
lead foil, and contain all contaminated items. Once all the
film packets have been opened, the gloves are removed and
placed with the contaminated items, and the films can be
loaded in the automatic processor with clean, dry hands. The
ungloved hands are removed through the light-tight baffles,
and the light-filter cover is opened to remove the discarded
items and clean and disinfect the inside of the unit wearing
utility gloves. The key to infection control using the daylight
loader is never to slide anything through the light-tight baffles
except clean, dry hands.
Although film packets with and without plastic barrier
envelopes can be processed in an automatic processor with a
daylight loader attachment, because of the complexity of the
infection protocol for its use, using film packets with barriers is
recommended.
REVIEW—Chapter summary
The purpose of infection control is to prevent the transmission
of disease between patients and operators and between patients.
Standard precautions treat every patient as if known to be infectious. The chain of infection involves a susceptible host,
pathogens in sufficient numbers to initiate infection, and an
appropriate route for the pathogen to enter the host. The oral
health care practice should have a written infection control policy. The Centers for Disease Control and Prevention (CDC), the
Occupational Safety and Health Administration (OHSA), the
U.S. Food and Drug Administration (FDA), and the U.S. Environmental Protection Agency (EPA) each play a role in developing, recommending, and/or enforcing guidelines for
infection control.
Personal protective equipment (PPE) includes protective
clothing, masks, eyewear, and gloves that act as barriers to prevent the transmission of infective microorganisms. Hands should
be washed thoroughly before and after treating each patient.
Disinfection and sterilization breaks the chain of infection to prevent the transmission of infective microorganisms.
Radiographic equipment and instruments may be classified as
FIGURE 10-11 Daylight loader with cover opened. The
operator placed clean, dry hands through the baffles. Note that gloves
will be put on once the hands are inside the unit.
CHAPTER 10 • INFECTION CONTROL 129
7. Radiographic image receptor holders are classified as
a. critical instruments.
b. semicritical instruments.
c. noncritical instruments.
d. clinical contact surfaces.
8. The lead/lead equivalent apron and thyroid collar is
classified as a
a. critical object.
b. semicritical object.
c. noncritical object.
d. cross-contaminated object.
9. Spraying disinfectant directly on which of these should
be avoided?
a. Digital sensor
b. Lead/lead equivalent apron and thyroid collar
c. X-ray machine exposure switch
d. Bracket table or countertop
10. Each of the following may be protected with a plastic
barrier to maintain infection control during the radiographic procedure EXCEPT one. Which one is the
EXCEPTION?
a. Image receptor
b. Image receptor holder
c. Exposure button
d. PID and tube head
11. Which of the following is correct infection control for
digital image receptors such as phosphor plates and
solid state sensors?
a. Protect with a plastic barrier prior to use. Sterilize
following use.
b. Protect with a plastic barrier prior to use. Disinfect
following use.
c. Disinfect prior to use. Protect with a plastic barrier
prior to use. Sterilize following use.
d. Disinfect prior to use. Protect with a plastic barrier
prior to use. Disinfect following use.
12. Which of the following can be heat-sterilized following
use?
a. Digital sensor
b. Phosphor plate
c. Film packet
d. Image receptor holder
13. What should be done with the image receptor immediately after removing it from the patient’s mouth?
a. Remove and reapply a clean plastic barrier.
b. Remove excess saliva with a dry or disinfectantsoaked paper towel.
c. Drop it into a containment cup or box without touching the sides.
d. Rinse briefly with plain water, do not use soap.
14. Following the radiographic procedure, the patient treatment area should be cleaned and disinfected using
a. clean, dry hands.
b. patient treatment gloves.
c. plastic overgloves.
d. utility gloves.
15. Which of the following is the correct order for maintaining infection control after the radiographic procedure?
a. Remove patient treatment gloves, remove lead/lead
equivalent apron, put on utility gloves, clean and disinfect
b. Remove lead/lead equivalent apron, remove patient
treatment gloves, put on utility gloves, clean and disinfect
c. Remove lead/lead equivalent apron, clean and disinfect, remove patient treatment gloves, put on utility
gloves
d. Put on utility gloves, remove lead/lead equivalent
apron, clean and disinfect, remove patient treatment
gloves
16. Which of the following is aseptically correct after using
the tab to open an exposed, contaminated film packet
without a plastic barrier?
a. Grasp the film holding by the edges between the
index finger and thumb.
b. Remove the lead foil first to get it out of the way to
allow for easier removal of the film.
c. Pull the black paper tab to allow the film to drop out
onto a paper towel.
d. Continue peeling back the outer plastic/paper wrap
until all contents of the packet are readily accessable.
17. Which of the following is recommended for use with an
automatic processor with a daylight loader attachment?
a. Digital sensors that used plastic barrier sheaths
b. Phosphor plates that used plastic barrier envelopes
c. Film packets that used plastic barrier envelopes
d. Film packets that did not use plastic barrier envelopes
REFLECT—Case study
While exposing a full mouth series of radiographs on your
patient, you accidentally drop the image receptor holding
device on the floor. Because you still have additional exposures
to complete, you need the use of this device. Explain in detail
what infection control protocol you would follow to deal with
this dilemma.
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson Education. Chapter 8, “Infection control and
student partner practice.”
REFERENCES
American Dental Association Council on Scientific Affairs.
(2006). The use of dental radiographs: Update and recommendations. Journal of the American Dental Association,
137(9), 1304–1312.
130 DENTAL RADIOGRAPHER FUNDAMENTALS
Darby, M. L., & Walsh, M. M. (2010). Dental hygiene theory
and practice (3rd ed.). St. Louis: Saunders Elsevier.
Dietz-Bourguignon E., & Badavinac R. (2002). Safety standards and infection control for dental hygienists. Albany,
NY: Delmar, Thomson Learning.
Hokett, S. D., Honey, J. R., Ruiz, F., Baisden, M. K., & Hoen,
M. M. (2000). Assessing the effectiveness of direct digital
radiography barrier sheaths and finger cots. Journal of the
American Dental Assocication, 131, 463–467.
Huber, M. A., Holton, R. H., & Terezhalmy, G. T. (2005). Cost
analysis of hand hygiene using antimicrobial soap and
water versus an alcohol-based hand rub. Oral Surgery,
Oral Medicine, Oral Pathology, 99, 4.
Kalathingal, S. M., Moore, S., Kwon, S., Schuster, G. S.,
Shrout, M. K., & Plummer, K. (2009). An evaluation of
microbiologic contamination on phosphor plates in a dental school. Oral Surgery, Oral Medicine, Oral Pathology,
107, 279–282.
Kalathingal, S. M., Youngpeter, A., Minton, J., Shrout, M.
K., Dickinson, D., Plummer, K., & Looney, S. (2010). An
evaluation of microbiologic contamination on a phosphor
plate system: Is weekly gas sterilization enough? Oral
Surgery, Oral Medicine, Oral Pathology, 109, 457–462.
Kohn, W. G., Harte, J. A., Malvitz, D. M., Collins, A. S., Cleveland, J. L., & Eklund, K. J. (2004). Guidelines for infection
control in dental health care settings—2003. Journal of the
American Dental Association, 135, 33–47.
Negron, W., Mauriello, S. M., Peterson, C. A., & Arnold, R.
(2005). Cross-contamination of the PSP sensor in a preclinical setting. Journal of Dental Hygiene, 79(3), 1–10.
Organization for Safety, Asepsis and Prevention. (2004, January). Infection Control in Practice, 3(1), entire issue.
Retrieved from http://www.osap.org
Organization for Safety, Asepsis Prevention. (2004). OSAP
check-up: 2003 CDC guidelines. Is your infection control
program up to date? Infection Control in Practice. Dentistry’s Newsletter for Infection Control and Safety, 3(1),
1–11.
Palenik, C. J. (2004). Infection control for dental radiography.
AADMRT Newsletter Retrieved from www.aadmrt.com/
currents/palenik_fall_04_print.htm
U.S. Dept. of Health and Human Services for Disease Control
and Prevention, Centers for Disease Control and Prevention. (2003, December 19). Guidelines for infection control
in dental health-care settings. MMWR, 52(RR17), 1–61.
U.S. Dept. of Health and Human Services for Disease Control
and Prevention, Centers for Disease Control and Prevention. (2002, October 25). Guidelines for hand hygiene in
health care settings: Recommendations of the Healthcare
Infection Control Practices Advisory Committee and the
HICPAC/SHEA/APIC/IDSA Hand Hygiene Task Force.
MMWR, 51(RR16), 1–44.
Wilkins, E. M. (2009). Clinical practice of the dental hygienist
(10th ed.). Philadelphia: Lippincott Williams & Wilkins.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Discuss the federal and state regulations concerning the use of dental x-ray equipment.
3. Describe licensure requirements for exposing dental radiographs.
4. Identify specific risk management strategies for radiography.
5. Recognize negative remarks about radiographic equipment that should be avoided.
6. List the five aspects of informed consent.
7. List the radiographic items that must be documented in the patient’s record.
8. Explain what should be said to patients who refuse radiographs.
9. Identify the role professional ethics play in guiding the radiographer’s behavior.
KEY WORDS
American Dental Assistants Association
(ADAA)
American Dental Association (ADA)
American Dental Hygienists’ Association
(ADHA)
Code of Ethics
Confidentiality
Consumer-Patient Radiation Health and
Safety Act
Direct supervision
Disclosure
Ethics
Federal Performance Act of 1974
Health Insurance Portability
and Accountability Act (HIPAA)
Informed consent
Liable
Malpractice
Negligence
Risk management
Self-determination
Statute of limitations
CHAPTER
11 Legal and Ethical
Responsibilities
CHAPTER
OUTLINE
 Objectives 131
 Key Words 131
 Introduction 132
 Regulations and
Licensure 132
 Legal Aspects 132
 Ethics 135
 Goals 135
 Review, Recall,
Reflect, Relate 136
 References 137
BOX 11-1 Web Sites for Professional Organizations
132 DENTAL RADIOGRAPHER FUNDAMENTALS
Introduction
Legal and ethical issues directly relate to radiation safety. The
dental radiographer must understand and respect the law governing
the use of ionizing radiation. Additionally, the radiographer
should be aware of the dental profession’s codes of ethics that
guide decisions regarding the use of ionizing radiation. The
purpose of this chapter is to discuss regulations that apply to
dental radiography and to present the ethical use of dental
radiographs.
Regulations and Licensure
To perform radiographic services for patients safely and legally,
the dental radiographer should be aware of the laws and regulations pertaining to dental radiology. This is especially important
because laws vary from state to state and often change to meet the
changing needs of society.
Equipment Regulations
Both federal and state regulations control the manufacture and
use of x-ray equipment. The Federal Performance Act of
1974 requires that all x-ray equipment manufactured or sold in
the United States meet federal performance standards. These
standards include safety requirements for filtration, collimation,
and other x-ray machine characteristics.
In addition to federal regulations, city, county, and state
laws affect the use of dental x-ray equipment. State laws require
registration and inspection of x-ray machines. Inspections are
conducted every 2 to 4 years, and usually fees are collected for
this service. Because laws and regulations vary for each state
and are subject to change, the dental radiographer should
contact the state’s bureau of radiological health for specific
information.
Licensure Requirements
Additionally, there are laws that establish guidelines regarding
who can place and expose radiographs. In 1981, then updated in
1991, the federal Consumer-Patient Radiation Health and
Safety Act was passed and signed into law to protect patients
from unnecessary radiation. This act established minimum
standards for state certification and licensure of personnel who
administer radiation in medical and dental radiographic
procedures. The intent of the act was to minimize unnecessary
exposure to potentially hazardous radiation.
Adoption of the act’s standards was made discretionary with
each state. As a result, not all states have voluntarily established
licensure laws for personnel who place and expose dental
radiographs. Nevertheless, most state laws require that operators
of x-ray equipment be trained and certified or licensed to take
dental radiographs. Many states consider dental hygienists and
dental assistants who have passed the National Board Dental
Hygiene Examine (NBDHE) and the Dental Assisting National
Board Examination (DANB), respectively, and hold a license to
practice in the state as a Registered Dental Hygienist or Certified
Dental Assistant, respectively, to meet this requirement. However,
some states require dental hygienists and dental assistants to take
an additional examination or to fulfill continuing education
requirements annually to be certified specifically in radiation
safety or radiographic technique competency.
State laws regulating personnel who expose dental radiographs vary considerably for on-the-job trained dental assistants.
Whereas many states have a mandatory state examination or a
continuing education requirement, some states allow these uncertified dental assistants with proper training to take radiographs
under the direct supervision of a dentist without certification.
Direct supervision means the dentist is present in the office when
the radiographs are taken. Each state’s Dental Commission
controls the scope of practice for assistants and hygienists.
Because laws and regulations vary for each state and are subject
to change, the dental radiographer should contact the state’s
Dental Commission directly to learn about legal requirements for
placing and exposing dental radiographs in that state. A complete
list of state Dental Commisions can be viewed on the American
Dental Association’s Web site (www.ada.org) (Box 11-1).
Legal Aspects
To aid in ensuring that one is practicing within the scope of the
law, the dental radiographer should be familiar with all laws and
regulations pertaining to dental radiography.
Risk Management
The most important legal aspect of dental radiology is risk
management. Risk management can be defined as the policies
and procedures to be followed by the radiographer to reduce the
chances that a patient will file legal action against the dentist
and oral health care team. Malpractice actions have increased in
number and amount of awards in recent years. All members of
the oral health care team must participate to make an effective
American Dental Assistant Association (ADAA) www.dentalassistant.org
American Dental Hygienists’ Association (ADHA) www.adha.org
American Dental Association (ADA) www.ada.org
Hispanic Dental Association (HDA) www.hdassoc.org
National Dental Association (NDA) www.ndaonline.org
National Dental Assistants Association (NDAA) Link from www.ndaonline.org
National Dental Hygienists Association (NDHA) www.ndhaonline.org
CHAPTER 11 • LEGAL AND ETHICAL RESPONSIBILITIES 133
risk management program. Following standard procedures and
performing procedures correctly will help reach the goal of
providing quality care and minimizing risk. (See Box 11-2 for
a radiography mini-audit for avoiding risk.)
Specific risk management procedures that can be a good
defense when performed correctly or a liability if performed poorly
include attempting to obtain a duplicate copy of a new patient’s
radiographs before reexposing the patient to ionizing radiation;
using the best equipment currently available, including fast-speed
film, leaded aprons and thyroid collars, film-holding devices, and
collimination; and establishing a written quality assurance system
for the darkroom to include daily, weekly, and monthly evaluation.
Providing all radiographers with a radiation monitoring badge,
whether required by law or not, is also a good risk management tool
(Figure 11-1). Monitoring radiation exposure, or more precisely
the lack of exposure, will provide the practice with documentation
of safe work habits.
Patient Relations
Patient relations refers to the relationship between the patient
and the dental radiographer. It is important to make the patient
feel comfortable by establishing a relaxing and confident chairside
manner (see Chapter 12). Always explain to the patient what
and how procedures are to be performed. Answer all questions
the patient may have concerning the procedures. Good patient
relations reduces the risk of possible legal action.
Avoid negative remarks about procedures, equipment, and
the dental staff. Statements like, “The films got stuck in the
processor again” or “This tube head always drifts” should never
be made to the patient or in front of the patient. These statements
imply that you have chosen to use known defective equipment
on a patient. This is not the same as saying, “The films got stuck
in the processor. They must be retaken. However, we will not
process the new films until a thorough investigation is made to
correct the problem with the processor.” or “This tube head is
drifting. Because this is a problem, we cannot use it to take your
x-rays until it is repaired. Let’s move to another room for your
procedure.” If equipment is not working properly, it should be
repaired or serviced.
Informed Consent
Informed consent is the consent the patient gives for treatment
after being informed of the nature and purpose of all treatment
procedures.
All patients have the legal right to make choices about the
health care they receive. This is called self-determination.
Self-determination includes the right to refuse treatment. To make
FIGURE 11-1 Radiographer wearing a radiation monitoring
badge.
BOX 11-2 Radiography Safety Audit for Risk Management
• Are all radiographers legally licensed, or certified, or properly trained to work with the x-ray equipment?
• Are radiographers’ licenses, registrations, certificates, and continuing education achievements posted for public view?
• Are equipment inspection certificates posted near or on the x-ray equipment as may be required by law?
• Are accident prevention signs in place as needed (i.e., to watch head when pulling x-ray tube head away from the wall)?
• Are signs posted regarding the use of ionizing radiation as may be required by law?
• Does the radiographer wear personal protective equipment (PPE) during the procedure?
• Are all radiographers required to wear a radiation dosimeter?
• Are radiation safety rules posted near the x-ray units?
• Are exposure settings for types of projections and patients posted near the control panel?
• Is a signed informed consent from the patient secured prior to radiography procedure?
• Are adequate records kept on patient exposures (consent, assessment of need, number and type of exposures, retakes, name of
radiographer who took the radiographs)?
• Are patient radiographs kept confidential? How?
• Will patient radiographs be interpreted thoroughly and findings documented and communicated to the patient
following the appointment?
• Is x-ray equipment up to date on all required inspections?
• Is documentation on quality control tests performed on all darkroom equipment kept?
• Does the radiographer wear impervious gloves and gowns and safety goggles when handling processing chemistry?
• Is an emergency eye wash station near where processing chemistry is handled?
• Do all radiographers or handlers of chemicals know the location of the hazardous chemicals lists and material safety
data sheets? (See chapter 20)
• Is emergency spill equipment available?
134 DENTAL RADIOGRAPHER FUNDAMENTALS
a decision regarding informed consent, the patient must be
informed of the following:
• The purpose of taking radiographs
• The benefits the radiographs will supply
• The possible risks of radiation exposure
• The possible risks of refusing the radiographs
• The person who will perform the procedure
It is the responsibility of the dentist to explain the nature
and purpose of all treatment procedures. When taking radiographs,
the risks and benefits must be explained in lay terms. The
informing process is called disclosure. The patient should be
given the opportunity to ask questions prior to radiography.
Answer all questions completely in terms the patient understands. State laws vary concerning informed consent. Be sure to
become familiar with your state laws.
Liability
Liable means to be legally obligated to make good any loss or
damage that may occur. Many states have laws that require dentists to supervise the performance of dental radiographers. Both
dentists and dental radiographers are liable for procedures
performed by the dental radiographer. Therefore, it is important
to understand that even though radiographers work under the
supervision of the dentist, they are legally liable for their own
actions. In malpractice cases, both the supervising dentist and
the dental radiographer may be sued for the actions of the
radiographer.
Patient Records
A record of all aspects of dental care must be kept for every
patient. Dental radiographs are considered a part of the patient’s
record and are therefore legal documents.
DOCUMENTATION The exposure of dental radiographs should be
documented in the patient’s record. Entries in the patient’s record
should be made by the dentist or under the dentist’s supervision.
The following items must be documented in the patient’s record.
• The patient’s informed consent
• The number and type of radiographs, including retakes
• The date the radiographs are taken and the name of the
radiographer who took them
• The reason for taking the radiographs
• The interpretive and diagnostic results
CONFIDENTIALITY State laws have always governed
confidentiality to protect the patient’s privacy. On April 14,
2003, the federal government signed into law privacy standards
to protect patients’ medical records and other health information, including radiographs. Developed by the Department of
Health and Human Services (DHHS) as part of the Health
Insurance Portability and Accountability Act of 1996
(HIPAA), this federal law is designed to provide patients with
control over how their personal health information is used and
disclosed. Radiographs are confidential and should never be
shown or discussed with anyone outside the oral health care
practice without first obtaining a current, signed release from
the patient. A patient will usually be asked to sign a notice that
indicates how their radiographs may be used and their privacy
rights under this law.
OWNERSHIP The courts have ruled that radiographs are the
property of the dentist. The patient pays for the dentist’s ability
to interpret the radiographs and to arrive at a diagnosis. However, patients may have reasonable access to their radiographs.
They may request a copy of their radiographs if they decide to
change dentists or request a consultation with a dental specialist (Procedure Box 11-1). The original radiographs, however,
belong to the dentist. Because of statute of limitation laws, it is
recommended that all records (including radiographs) be
retained indefinitely.
RETENTION Dental radiographs must be retained for seven
years after the patient ceases to be a patient. Legal action that can
be brought against the dentist depend on the malpractice and limitation statues that vary from state to state. For adult patients, the
statute of limitations generally begins to run at the time of the
injury, or when the injury should have reasonably been discovered. For children, the statute of limitations does not begin until
the child reaches the age of majority (18 to 21 years old, depending on the state). If you work for a governmental entity, the statute
of limitations may be affected by certain notice statutes, which
PROCEDURE 11-1
Procedure for releasing a copy of the patient’s radiographs
1. Patient requests copy of radiographs in writing.
2. Keep the letter requesting radiographs in the patient’s record.
3. Duplicate the original radiographs or print out a paper copy of digital images.
4. Send the duplicate radiographs or paper copy of digital images by the U.S. Postal Service’s
Certified Mail.
5. Keep the postal receipt in the patient’s record.
CHAPTER 11 • LEGAL AND ETHICAL RESPONSIBILITIES 135
may greatly reduce the time in which a suit may be brought.
Because the time period is so indefinite, it is recommended that
radiographs be retained forever.
INSURANCE CLAIMS Insurance companies have the right to
request pretreatment radiographs to evaluate the dental treatment
plan for services that they will be paying for. Again, only duplicate
radiographs should be sent. The oral health care practice should
keep the originals. It may be acceptable to send digital images
electronically. The number of insurance companies that except
digital images electronically is increasing.
Malpractice Issues
Malpractice results when one is negligent. Negligence occurs
when the dental diagnosis or treatment is below the standard of
care provided by dentists in a similar locality and under similar
conditions.
NEGLIGENCE Negligence is defined as the failure to use a
reasonable amount of care when failure results in injury or
damage to another. Negligence may result from the care (or lack
of care) of either the dentist or the dental radiographer.
Statute of Limitations is the time period during which
a patient may bring a malpractice action against a dentist or
radiographer. State laws govern this time period, which begins
when the patient discovers, or should have discovered, an injury
due to negligent dental treatment.
Sometimes negligence is not discovered until years later,
when a patient changes dentists and discovers an injury has
occurred. In such cases, the statute of limitations begins years
after the negligent dental treatment occurred. An example would
be where appropriate radiographs were not taken on a patient
with periodontal disease. Years later, the patient is examined by
another dentist and is informed of the irreversible periodontal
condition that might have been prevented if detected earlier.
Besides the statute of limitations, many states have separate
malpractice laws that may limit damages or, in the case of
governmental entities, may provide limited or complete immunity
from suit, under certain circumstances. Because the laws vary
greatly from state to state, it is desirable to consult a lawyer
experienced in this area to provide training and answer questions
for the entire oral health care practice team as part of the risk
management program.
PATIENTS WHO REFUSE RADIOGRAPHS Occasionally, for a
variety of reasons, patients express opposition to the dentist’s
proposal that x-rays be taken. Often these patients believe that
such radiographs are unnecessary or that they will add to the cost
of treatment, or the patient may be fearful that dental x-ray exposure
will be hazardous to their health. When this happens, the dentist
and radiographer must carefully explain in clear terms why the
radiographs are needed to supplement the diagnosis, prognosis,
or treatment plan and therefore benefit the patient.
Frequently a patient may offer to sign a paper to assume the
responsibility for not taking radiographs. The patient must be
informed in a diplomatic manner that legally, such documents
do not release the dentist from liability and are not valid because
the patient cannot legally consent to negligent care. If the patient
still refuses the radiographs, the dentist must carefully decide
whether treatment can be provided. Usually, in such cases, the
dentist cannot treat the patient.
Ethics
In addition to the law, the ethics of a profession also guide the
behavior of the health care practitioner. Ethics is defined as a
sense of moral obligation regarding right and wrong behavior.
Professional ethics define a standard by which all members of
the profession are obligated to conform. These professional rules
of conduct are called a profession’s Code of Ethics. See
Box 11-1 for a list of Web sites where you can locate the Code
of Ethics for the American Dental Association (ADA),
American Dental Hygienists’ Association (ADHA), and
American Dental Assistants Association (ADAA). A professional Code of Ethics helps to define the rules of conduct for its
members.
Goals
Managing risk, knowing the law, and applying ethics, the dental
radiographer should strive for practice that is safe, is professional, and places the patient’s well-being first. One achieves
this by setting goals. Such goals are closely related, and all are
equally important. Goals of the dental radiographer include the
following:
• Achieve perfection with each radiograph. This is accomplished by careful attention to details. Each step in the process,
whether in image receptor placement, exposure technique, or
processing and identification, is significant.
• Perform confidently and with authority. Patients are
more likely to cooperate with someone who demonstrates
self-confidence. Communicate with patients in a respectful
manner.
• Take pride in services rendered and professional advancement. Obtain certification in radiation safety, whether or not
required by law. Improve skills and update techniques by
attending continuing education lectures and workshops,
participating in professional association meetings, and reading
professional journals and books.
• Keep radiation exposure as low as possible. Take the
time to use protective devices that minimize radiation to
the patient and follow strict protocols to protect yourself
during exposures. Maintain an environment that minimizes
the risk of harm.
• Avoid retakes. Be familiar with common errors to avoid.
Do not retake any exposure when you are not sure of the
corrective action. If the patient cannot tolerate placement
of the image receptor or cannot cooperate with the procedure, stop and get assistance, or try an acceptable alternative
procedure.
• Develop integrity, dedication, and competence that
promotes ethical behavior and high standards of care.
Provide patients with information to assist them in making
informed decisions regarding their consent to radiographic
procedures. Serve all patients without discrimination.
136 DENTAL RADIOGRAPHER FUNDAMENTALS
REVIEW—Chapter summary
The dental radiographer should be aware of the laws and
regulations pertaining to dental radiography. Both federal and
state regulations control the manufacture and use of x-ray
equipment.
State laws require that operators of x-ray equipment be
trained and certified or licensed to take dental radiographs.
Some states may require the registered dental hygienist and the
certified dental assistant to take an additional examination or a
continuing education course to be certified to take radiographs.
Other states allow an on-the-job-trained dental assistant with
proper training to place and expose radiographs under the direct
supervision of the dentist.
Risk management strategies and good patient relations
reduce the risk of possible legal actions. Informed consent allows
the patient to make decisions regarding the procedure. Disclosure
informs the patient about the radiographic procedure and answers
all questions the patient may have concerning the procedures.
Both the dentist and the dental radiographer are liable for procedures
performed by the dental radiographer.
The patient’s records, including the radiographs, are confidential. The courts have ruled that radiographs are the property
of the dentist; the patient pays only for the diagnosis. However,
patients may have access to their radiographs via copies.
When an individual ceases to be a patient, the radiographs
should be retained for at least seven years. Risk management and
the statutes of limitation suggest that radiographs be retained
indefinitely.
The patient who refuses radiographs may not legally consent
to negligent care. The professional’s code of ethics guides the
behavior of the radiographer. Goals for the dental radiographer
are presented.
RECALL—Study questions
1. Registration and inspection of x-ray machines is regulated by the
a. federal government.
b. state government.
c. local government.
d. Any of the above
2. The laws allowing individuals to place and expose dental
radiographs vary from state to state.
a. True
b. False
3. Which of the following is a risk management strategy?
a. The use of fast-speed film, film-holding devices, and
collimation
b. Monitoring the dental radiographer with radiation
dosimeters
c. Obtaining a copy of a new patient’s radiographs
from a previous dentist
d. All of the above
4. Which of these comments should be avoided when talking to the patient?
a. “We have switched to a fast-speed film.”
b. “This exposure button sticks sometimes.”
c. “You must stay still during the exposure.”
d. “I’m certified to take your radiographs.”
5. List five aspects of informed consent.
a. ______________
b. ______________
c. ______________
d. ______________
e. ______________
6. Every patient has the legal right to make choices about the
oral health care they receive. This is called
a. disclosure.
b. informed consent.
c. self-determination.
d. liability.
7. List five items regarding the radiographic procedure
that should be documented in the patient’s record.
a. _______________
b. _______________
c. _______________
d. _______________
e. _______________
8. Legally dental radiographs should be retained for an
individual who ceases to be a patient for
a. three years.
b. five years.
c. seven years.
d. nine years.
9. Both the dentist and the dental radiographer are liable
for procedures performed by the dental radiographer.
a. True
b. False
10. Failure to use a reasonable amount of care that results in
injury is termed
a. risk.
b. liability.
c. confidentiality.
d. negligence.
11. The courts have ruled that radiographs are the property of the
a. patient.
b. dentist.
c. dental radiographer.
d. state.
12. When patients express opposition to having dental radiographs taken, the radiographer should
a. ask the patient to sign a document to release the dentist of liability.
b. consult the professional code of ethics about what to
do next.
c. postpone the procedure and ask the patient to return
at a later date.
d. explain why the radiographs are needed and what the
benefits will be.
CHAPTER 11 • LEGAL AND ETHICAL RESPONSIBILITIES 137
13. A professional code of ethics
a. makes the laws that govern the use of dental radiographs.
b. establishes the time frame for taking dental radiographs.
c. helps to define the rules of conduct for its members.
d. protects the dental radiographer in cases of legal
action.
14. Each of the following is a goal of the radiographer
EXCEPT one. Which one is the EXCEPTION?
a. Increasing the demand for dental x-ray services
b. Reducing the radiation dose used during an exposure
c. Professional improvement and advancement
d. Presenting confidence to gain patient acceptance
REFLECT—Case study
Consider the following scenario.
You have been working in a practice for over a year and
have developed a friendship with another dental assistant. You
often socialize together outside work, and your children play
together. One evening during dinner, your dental assistant
friend tells you that even though she has been exposing dental
radiographs on patients since she was hired by the practice
over two years ago, she does not have the state-required radiation safety certification. She tells you that the dentist never
asked to see her certificate during the job interview. She wasn’t planning to “break the law” but the first day on the job, the
dentist explained to a patient that she would be taking the full
mouth series, and “not to worry, because she was a competent
clinician.” Your friend explains to you that it would have been
embarrassing to tell the dentist at that point that she was not
certified, so she exposed the radiographs. After that, she
thought about taking a course to prepare for the state examination, but didn’t want to get “caught” taking the exam after
she had already been placing and exposing radiographs all
this time. She hopes you will keep her confidence because
you are friends.
Reflect on this scenario and answer the following
questions.
1. How has your friend broken the law?
2. How has this behavior endangered the patient? Your
friend? Your employer?
3. Describe the legal and/or ethical situation she faces.
4. Describe the legal and/or ethical dilemma you face.
5. How could your employer have prevented this situation?
6. What aspects of the Dental Assisting or Dental Hygiene
Code of Ethics apply to this situation?
7. Take the role of your friend; what would you have done
if you were she?
RELATE—Laboratory practice
Using the computer, visit the Web sites for the board of
radiological health or the board of dentistry in all 50 states
and the District of Columbia. Compile a listing of states with
certification requirements for dental radiographers and answer
the following questions.
1. How many states require all radiographers to be certified
for performing radiographic procedures?
2. What states accept a registered dental hygienist’s or
certified dental assistant’s credentials as certification
for performing radiographic procedures?
3. Do any states require additional tests or continuing
education classes for a dental assistant or dental hygienist
to maintain radiographic certification?
4. Why do you think some states do not require certification
for those individuals who place and expose dental
radiographs?
5. What are the advantages to the oral health care practice
to hire only certified radiographers?
6. How should the public be educated on these laws governing
the certification of individuals to place and expose dental
radiographs?
REFERENCES
Bundy, A. L. (1988). Radiology and the law. Rockville, MD:
Aspen.
Darby, M. L., & Walsh, M. M. (2010). Dental hygiene theory
and practice (3rd ed.). St. Louis, MO: Elsevier.
Davison, J. A. (2000). Legal and ethical considerations for
dental hygienists and assistants. St. Louis, MO: Mosby
Elsevier.
U.S. Dept. of Health and Human Services. (n.d.). Fact sheet:
Protecting the privacy of patients’ health information.
Retrieved from www.hhs.gov/news/facts/privacy.html
Patient Relations
and Education
CHAPTER
OUTLINE
 Objectives 138
 Key Words 138
 Introduction 139
 Patient Relations 139
 Communication 140
 Patient
Education 141
 Frequently Asked
Questions 143
 Review, Recall,
Reflect, Relate 145
 References 146
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define key words.
2. Value the need for patient cooperation in producing quality radiographs.
3. List the aspects of patient relations that help to gain confidence and cooperation.
4. Explain how appearance and first impression affect patient relations.
5. Identify five areas where the radiographer’s positive attitude will foster patient confidence.
6. State examples of interpersonal skills that are used to communicate effectively.
7. Explain the relationship between verbal and nonverbal communication.
8. Give an example of a negative-sounding word that should be avoided when explaining
the radiographic procedure.
9. Explain the communication method show-tell-do and give three examples of when this
method would be effective.
10. State the two reasons patient education in radiography is valuable.
11. Respond to a patient’s concern regarding unnecessary exposure to x-rays.
12. Describe two methods by which the patient can be educated to appreciate the value of
dental radiographs.
Appearance
Attitude
Chairside manner
Communication
Empathy
Frequently asked questions (FAQs)
Interpersonal skills
Nonverbal communication
Patient education
Patient relations
Show-tell-do
Verbal communication
CHAPTER
12
KEY WORDS
CHAPTER 12 • PATIENT RELATIONS AND EDUCATION 139
The radiographer’s attitude toward his/her own technical
ability will also be conveyed to the patient. Because a demonstration of technical skill will build patient confidence, the radiographer should feel that his/her training and education provided
adequate preparation for this role. Having confidence in oneself
fosters confidence in others.
Additionally, the unique close working relationship of the
oral health care team requires that everyone work well together.
Attitudes toward an employer and coworkers also play a role in
determining the degree of successful patient management.
Patients can sense the professional’s attitude by the way he/she
walks, talks, and behaves. For example, the patient will easily
sense a disgruntled dental assistant who had to interrupt what
he/she was doing to take radiographs for a dental hygienist who
was running behind in the schedule. Maintaining a pleasant,
positive attitude will help generate the same from patients.
Interpersonal Skills
Interpersonal skills are used to communicate with others successfully. Respectfulness, courtesy, empathy, and patient,
honest, and tactful communication are examples of interpersonal skills. When explaining the need for radiographs, consider how the patient will feel. If the patient has concerns
regarding the need for x-ray exposure, respect their views.
Statements such as, “Don’t worry” and “Everything will be
okay,” may convey an attitude of apathy, or imply that the
patient’s apprehensions don’t matter. If placement of an intraoral imaging receptor during the radiographic procedure is
uncomfortable, show empathy. Empathy is defined as the
ability to share in another’s emotions or feelings. Be courteous and polite at all times even in difficult situations. However, if discomfort must be tolerated to produce the necessary
radiograph, empathetic, yet direct and tactful communication
can help bring about the desired result.
An important aspect of interpersonal skills is the radiographer’s chairside manner. Chairside manner refers to the conduct of the radiographer while working at the patient’s
chairside. The radiographer should strive to always make the
Introduction
Effective communication is essential to producing quality
radiographic images. The radiographic procedure requires
that the patient understand and cooperate with the process.
The radiographer must be able to communicate specific directions for success of the procedure. Precise patient positioning,
the sometimes difficult placement of an image sensor in the
oral cavity, and the potentially harmful nature of ionizing
radiation make clear communication and good interpersonal
skills especially important. The purpose of this chapter is to
discuss how interpersonal skills affect the radiographic
process, present guidelines for effective communication, and
investigate the role the dental assistant and the dental hygienist play in educating the patient regarding the need for dental
radiographs.
Patient Relations
Patient relations refers to the relationship between the patient
and the oral health care professional. Appearance, attitude,
interpersonal skills, and communication help gain patient confidence and cooperation, the outcome of which will be the production of quality radiographs.
Appearance
The patient’s first impression of the dental radiographer is
important. The first impression is often made based on the
radiographer’s appearance. The dental radiographer should
always maintain a professional appearance. The careful
attention given to personal hygiene and grooming such as
trimmed nails, clean hands, and fresh breath convey an
understanding of the importance of maintaining all aspects of
infection control. A clean, neat appearance builds confidence
in patients.
Attitude
Attitude is defined as the position assumed by the body in
connection with a feeling or mood. Attitude will play a significant role in gaining the patient’s trust in the radiographer’s
ability. The attitude of the radiographer toward the procedure
will be conveyed to the patient. If the radiographer feels that
the procedure is uncomfortable or unnecessary, these feelings
will be conveyed to the patient. The radiographer should not
impose his/her own feelings onto the patient. Although the
radiographer may have had a less than ideal experience with a
certain procedure, this does not necessarily mean that the
patient will experience the same discomfort. For example, the
radiographer may have experienced a gag reflex when posterior periapicals were taken on him/her. If this radiographer
approaches the patient with the attitude that posterior periapicals will excite a gag reflex, the outcome is likely to be just
that. A fresh, positive attitude with each new patient will more
likely produce a cooperative patient. This is especially true if
the patient perceives the radiographer as possessing a nonjudgmental attitude.
PRACTICE POINT
Always greet the patient by name. Address the patient using
their proper title (Miss, Mrs., Ms., Mr., Dr., etc.) and last
name. If you are uncertain of the correct pronunciation of
the patient’s name, ask the patient to pronounce it for you.
Always introduce yourself to the patient, using both your
name and title. For example: “Good morning, Ms. Washington. My name is Maria Melendez. I’m the dental assistant
who will be taking your radiographs today. Please follow me
to the x-ray room, and we will get started.”
140 DENTAL RADIOGRAPHER FUNDAMENTALS
Communication
Communication is defined as the process by which information is exchanged between two or more persons. This may be
accomplished verbally (with words) or nonverbally (without
words). Effective communication is communication that works
(Box 12-1).
HONESTY Verbal and nonverbal communication are essential
to building patient confidence. Patient questions must be
answered honestly. It is very important that the radiographic
procedure be explained honestly, including any possible discomfort anticipated, to gain cooperation and assistance. Honesty develops trust. When a patient trusts the dental
radiographer, the patient is more likely to cooperate with the
radiographic procedure.
patient feel comfortable. Working in a confident manner will
help put the patient at ease. Comments that indicate a lack of
control, such as “Oops!” must be avoided. An important consideration during the radiographic procedure is to praise the
patient for any assistance they provide. Positive reinforcement
and feedback that the procedure is going well will help foster
even more cooperation. For example, letting a patient know that
you appreciated their ability to hold the image receptor in place
long enough to make the exposure will help to motivate the
patient to continue working together with you to complete the
procedure. Likewise, showing frustration with a patient who is
having difficulty managing the the procedure will most likely
only increase the patient’s anxiety.
BOX 12-1 Guidelines for Effective
Communication
• Introduce yourself and show interest.
• Face the patient and make eye contact.
• Lean forward to demonstrate listening.
• Be honest to build trust.
• Show courtesy and respectfulness.
• Maintain a positive attitude.
• Demonstrate empathy when appropriate.
• Use clear commands.
• Make nonverbal communication in agreement with verbal
communication.
Verbal Communication
Effective use of words in verbal communication begins with
facing the patient directly and maintaining eye contact.
Because a face mask is recommended PPE (personal protective
equipment; see Chapter 10) during radiographic procedures, it
is very important that the verbal requests and commands used
to communicate specific directions during the radiographic
procedures be understood by the patient. Once the image receptor is in place, the operator needs to give explicit directions to
complete the procedure quickly. For example, once the receptor
holding device is placed in the mouth, the patient must be
requested to bite firmly and to hold completely still while the
operator leaves the area to make the exposure. The process will
be hindered and prolonged if the patient does not understand
the requests or the operator must repeat the commands.
The radiographer’s choice of words and sentence structure
are also important. Words used should be at a level the patient
can understand. For example, young children may better understand, “These are pictures of the teeth made with a special dental camera” (Box 12-2). An adult would appreciate hearing a
more professional sounding, “Here’s a radiograph showing
your periodontal condition.” However, too many highly technical words may confuse the patient and result in misunderstandings. Words that imply negative images such as “zap,” “shot,”
and “irradiate” are better avoided.
PRACTICE POINT
If it is necessary to place the image receptor into a particularly
sensitive area, encourage the patient to cooperate and praise
him/her for the willingness to tolerate the difficult placement.
Show empathy, but let the patient know that the placement
is correct and if he/she can tolerate the discomfort for the
short time required for exposure, the result will be a diagnostic quality radiograph. Avoid asking, “Does that feel okay?”
The patient will perceive this to mean that discomfort equals
incorrect positioning and will feel obligated to inform you of
any and all feelings associated with the procedure. The
patient will now be acutely aware of the feeling of the image
receptor in the mouth and continue to inform you regarding
the “feeling” of each subsequent placement, possibly making the procedure more difficult. Saying, “Are you doing okay
so far?” is a better way to let the patient know you are aware
of their efforts to cooperate.
PRACTICE POINT
Always give a command, and not a question, to request that
the patient hold still during the exposure. For example, asking the patient, “Can you hold still, please?” will most likely
cause the patient to attempt to move to answer you, defeating the purpose of your request. The command, “Hold still,
please” is less likely to prompt the patient to move.
CHAPTER 12 • PATIENT RELATIONS AND EDUCATION 141
FIGURE 12-1 Patient education The dental radiographer
educates the patient on the value of radiographs.
Nonverbal Communication
Nonverbal communication includes gestures, facial expressions,
body movement, and listening. A nod of the head indicates yes or
agreement, and a shake of the head indicates no or disagreement.
We usually use a combination of verbal and nonverbal communication. Nonverbal communication is very believable. When verbal and nonverbal communications are not in synch, it is often
the nonverbal communication that conveys the strongest message. For example, if you tell the patient that you don’t mind
that they have to stop and take a break in between each radiograph placement, but you roll your eyes or tap your foot while
waiting for them to feel ready to begin again, the patient will
probably not believe you because your actions speak louder
than your words. Facial expressions strongly convey the attitude of the radiographer. A smile by the radiographer will likely
relax the patient and reduce apprehension.
It is just as important that the radiographer practice good
listening skills. Careful attention to listening results in fewer
misunderstandings. Eye contact and attentive body posturing
communicates warmth and caring to the patient. Additionally,
the radiographer should observe the patient’s nonverbal communication. There is most likely something wrong with a patient
who is clutching the arms of the treatment chair with tears in
her eyes, even if she has not verbally communicated with you.
The use of show-tell-do as a method of combined verbal
and nonverbal communication is useful in dental radiography,
especially when barriers to communication exist such as in the
case of a language or cultural difference, a sensory impairment,
or a cognitive impairment (Boxes 12-3 and 12-4). Showing the
patient the image receptor and holder and demonstrating PID
placement prior to beginning to procedure can help alleviate
apprehension.
Patient Education
Educating patients about the importance of dental radiographs
in comprehensive oral health care depends on the radiographer’s ability to communicate (Figures 12-1 and 12-2). This
communication ability is based on the radiographer’s knowledge, education, and training in the area of dental radiology. It
is surprising how many patients do not comprehend the
BOX 12-3 Guidelines for Communicating with
the Elderly
• Use guidelines for effective communication.
• Address by the person’s title unless they instruct you otherwise.
• Avoid condescending salutations such as “Honey” and
“Dear.”
• Be aware of generational differences.
• Be aware of sensory or cognitive impairments such as hearing
loss, effects of stroke.
• Encourage the use of eyeglasses and hearing aids during the
procedure and especially when showing radiographs during
patient education.
BOX 12-2 Guidelines for Communicating
with Children
• Use guidelines for effective communication.
• Use age-level appropriate language.
• Do not talk down or use baby talk.
• Avoid threatening-sounding words.
• Expain the procedure simply and clearly.
• Use show-tell-do.
• Tell the truth whenever possible.
PRACTICE POINT
Sentence structure is important for the short, precise directions needed for radiographic procedures. For example,
requesting that the patient bite down on the image receptor holder by saying, “Close slowly please” may prompt the
patient to close before the operator says the word slowly.
Rearranging the words to say, “Slowly close please,” may
be more likely to produce the desired result.
BOX 12-4 Guidelines for Communicating with
People of Different Cultures
• Use guidelines for effective communication.
• Learn about the cultures in your community.
• Be accepting and nonjudgmental.
• Be aware that gestures may be interpreted differently.
• Be aware that touch and personal space are sometimes considered differently by different cultures.
• Speak slowly and avoid the use of slang or uncommon terms.
• Verify that the listener has understood what you said.
142 DENTAL RADIOGRAPHER FUNDAMENTALS
enormous value of a radiographic examination of their teeth
and the supporting oral structures.
Value of Patient Education
The value of patient education is twofold. First is the understanding that dental radiographs disclose pathology (disease)
that might otherwise go undetected and become an increasing
threat to the patient’s health if not treated in a timely manner.
Second is that the educated patient is more inclined to understand and accept dental treatment plans and embrace suggestions for oral health promotion and disease prevention. Such
patient acceptance helps develop a spirit of confidence and
mutual trust in the oral health care practice.
Necessity for Patient Education
Most people have heard negative reports regarding the effects
of overexposure to radiation. The dental patient, when faced
with a treatment plan recommending radiographs, will rightfully question the necessity of being exposed to x-radiation. It
is the responsibility of the entire dental team to provide the
patient with clear, concise, and satisfactory answers regarding
any questions or concerns he/she may have. Acceptance of the
dental treatment plan is more likely not only when a satisfactory explanation of need is presented, but also when the patient
is given an explanation of the ethical safeguards the practice
has adopted to reduce the risk of harm.
Identifying with the patient’s concerns is the first step to
open communication. The radiographer can verbally agree with
the patient that excess radiation exposure is a concern and that
the practice has adopted a strict radiation safety program. Patient
acceptance and confidence increase when he/she is made aware
of the many safety protocols the practice has put into place.
To begin the conversation, the patient should be told about
the evidence-based selection criteria guidelines developed by
an expert panel of health care professionals and updated in
2004 by the American Dental Association that aid the dentist
in deciding when, what type, and how many radiographs
should be taken (see Chapter 6). These evidence-based guidelines are the single biggest factor in eliminating unnecessary
radiographs.
Further, the patient should be informed that all standard
safety protocols as suggested by federal agencies, such as the
National Council on Radiation Protection and Measurements, and
the state and local laws governing inspections, calibrations, and
the use of radiological equipment are being adhered to. Many
people may not realize that x-ray equipment is strictly regulated by law.
In some locations, laws also regulate who can operate the
dental x-ray machine. Where applicable, individuals who place
and expose radiographs must be educated and trained and pass
an examination prior to being certified to place and expose dental radiographs. If the state issues a license or a certificate of
compliance to show that a radiation safety examination has been
passed, that can be offered in evidence. Many radiographers
display their certificates near the x-ray machine. Patient confidence in the radiographer increases when he/she knows that the
professional has been educated or trained and has passed a certification exam in the safety protocols governing the use of xradiation.
The patient should be assured that everyone in the office
who works with the dental x-ray machine, regardless of statemandated certification, is trained in its use and the safety
aspects of radiation. Continuing education courses in radiology
taken by the radiographer also boost patient confidence and
elevate the practice as one that values competency.
Finally, the patient and radiographer may have a discussion
about equipment specially designed to reduce radiation exposure, such as collimated position indicating devices (PIDs), thyroid collars and protective lead aprons, fast-speed film, and
modern equipment that is better constructed to prevent unnecessary radiation. The patient may not be aware of the reasoning
behind the use of these devices. Many patients assume the lead
apron is only for pregnant females and may be unaware that
utilizing a holder to position the image receptor prevents them
from having to hold the film in their mouth and unnecessarily
expose their fingers.
Methods of Patient Education
The patient can be educated on the value of radiographs
through verbal discussion, printed literature, or a combination
of the two. Backing up your verbal explanation with a printed
brochure is very effective at getting the message across. Literature may be obtained from professional organizations, commercial dental product companies, or off the Web. However,
care should be taken to use reliable sources of literature. The
radiographer should be aware of misleading sources of information, especially those readily available to patients on the
Web. The radiographer should be prepared to help the patient
separate correct information from incorrect or misleading
information.
ORAL PRESENTATION An effective method of educating the
patient is to give an oral presentation using a series of radiographs showing typical dental conditions, both normal and
abnormal. Placed in convenient mounts, the radiographs are
shown to the patient on a lighted view box or a computer
FIGURE 12-2 Incorporating digital radiographic images in
patient education.
CHAPTER 12 • PATIENT RELATIONS AND EDUCATION 143
monitor (Figures 12-1 and 12-2). The handheld viewer shown
in Figure 12-3 is well suited for an up-close chairside view of
film-based radiographs. Patients are generally able to identify
the areas that are pointed out to them on the radiographs better if the images are magnified and the brightness of the light
is controlled. A sample set of radiographs will allow the radiographer to explain the value of the use of radiographs in the
patient’s oral care plan. When viewing the patient’s own radiographs, the radiographer should remember that all members
of the oral health care team can interpret radiographs, but it is
the dentist’s responsibility to make the final interpretation and
diagnosis. The difference between interpretation and diagnosis is discussed in Chapter 21.
PRINTED LITERATURE An effective education method is to
place printed literature in the reception area or to give it to
patients before their appointment. Giving pamphlets to the
patient opens the door for two-way communication on the
advisability and necessity of regular radiographic examinations. All too often the patient is simply told that the doctor
requires radiographs and will not treat the patient unless they
are taken, or else the explanation is limited to a few short and
often unsatisfactory answers.
Literature may be obtained from one’s professional association (American Dental Association, American Dental Hygienists’
Association, American Dental Assistants Association) or can be
custom produced to meet the needs of the practice (Table 12-1).
Frequently Asked Questions
Here are some examples of frequently asked questions (FAQs)
and answers reprinted from the American Dental Association
brochure Dental X-ray Examinations: Your Dentist’s Advice and
Web site (www.ada.org/public/topics/xrays_Faq.asp) and from the
Academy of General Dentistry’s Web site (http://www.knowyour
teeth.com/infobites/abc/article/?abc=w&iid=342&aid=1373).
QUESTION: What are the benefits of dental x-rays?
ANSWER: Many diseases of the teeth and surrounding tissues
cannot be seen through a visual examination alone. An x-ray
examination may reveal
• Small areas of decay between the teeth
• Infections in the bone
• Abscesses or cysts
• Developmental abnormalities
• Some types of tumors
Finding and treating oral health problems at an early stage
can save time, money, and unnecessary discomfort. Radiographs can detect damage to oral structures not visible during
a regular exam. If you have a hidden tumor, radiographs may
even help save your life.
QUESTION: How often should x-rays be taken?
ANSWER: How often radiographs (dental x-rays) should be taken
depends on the patient’s individual health needs. It is important to
recognize that just as each patient is different from the next, so
should the scheduling of x-ray exams be individualized for each
patient. The dentist will review your history, examine your mouth,
and then decide whether you need radiographs and what type. If
you are a new patient, the dentist may recommend radiographs to
determine the present status of the hidden areas of your mouth
and to help analyze changes that may occur later.
The schedule for needing radiographs at recall visits
varies according to your age, risk for disease, and signs and
symptoms. Updated radiographs may be needed to detect new
cavities, to determine the status of gum disease, or for evaluation of growth and development. Children may need x-rays
more often than adults. This is because their teeth and jaws are
still developing and because their teeth are more likely to be
affected by tooth decay than those of adults.
FIGURE 12-3 Handheld viewer-enlarger is a helpful
adjunct to patient education.
TABLE 12-1 Web Site Resources for Patient Education Materials
SOURCE URL
American Dental Association http://www.ada.org/2760.aspx?currentTab=2
Academy of General Dentistry http://www.knowyourteeth.com/infobites/abc/article/?abc=X&iid=342&aid=1373
U.S. National Library of Medicine www.nlm.nih.gov/medlineplus/ency/article/003801.htm
Colgate http://www.colgate.com/app/Colgate/US/OC/Information/OralHealthBasics/
CheckupsDentProc/XRays/XRaysandIntraoralPictures.cvsp
WebMD Health http://www.webmd.com/oral-health/guide/dental-x-rays-when-get-them
144 DENTAL RADIOGRAPHER FUNDAMENTALS
Source
Estimated Exposure
(mSv ) *
Dental radiographs
Bitewings (4 films) 0.038
Full mouth series
(about 19 films)
0.150
Medical radiographs
Lower GI series 4.060
Upper GI series 2.440
Chest 0.080
Average radiation from outer space
in Denver, CO (per year)
0.510
Average radiation in the United
States from natural sources
(per year)
5.500
The term millisievert (mSv) is a unit of radiation measurement that
allows for comparisons between different types of radiation.
Source: Frederiksen, N. L. (1995). X-rays: What is the risk? Texas Dental
Journal, 112(2), 68–72.
*
QUESTION: Can I refuse dental x-rays and still be treated?
ANSWER: No. Treatment without necessary radiographs is
considered negligent care. Even if you signed a paper stating
that you refused radiographs and released the dentist from all
liability, you would be consenting to negligent care. You cannot, legally, consent to negligent care. (Negligent care is discussed in Chapter 11.)
QUESTION: What kind of radiographs does my dentist usually
recommend?
ANSWER: Typically, most dental patients have periapical or
bitewing radiographs taken. These require a film or digital sensor
be placed into the mouth, and the patient must stabilize it by biting
down on the holder. Bitewing radiographs can be used to determine the presence of decay in between teeth, whereas periapical
radiographs show root structure, bone levels, cysts, and abscesses.
QUESTION: My dentist has prescribed a panoramic radiograph. What is that?
ANSWER: Just as a panoramic photograph allows you to see a
broad view, a panoramic radiograph allows your dentist to see
the entire structure of your mouth in a single image. All teeth of
both the maxilla and the mandible plus the surrounding tissues
and supporting bone are imaged.
QUESTION: Why do I need both types of radiographs?
ANSWER: A periapical or bitewing radiograph shows only a few
teeth on one image. The panoramic radiograph is a comprehensive view of all of the teeth plus the surrounding supporting
structures. Both may be needed because although the panoramic
radiograph images more tissues, the periapical or bitewing radiographs provide a more detailed image, making it easier to see
decay or cavities between your teeth and early or subtle changes
in the periodontal tissues. Radiographs are not prescribed indiscriminately. Your dentist has a need for the different information
that each radiograph can provide to formulate a diagnosis.
QUESTION: How is x-ray exposure measured?
ANSWER: Special units are used to measure x-rays. When
human tissue or other materials are exposed to x-rays, some of
the energy is absorbed and some passes through without effect.
The amount of energy absorbed by the tissue is the dose. The dose
is often measured in sieverts (Sv). In modern diagnostic dental xray procedures, the exposures are usually so small that they are
expressed in “milli” units—that is, units that are equal to onethousandth of a Sv, or mSv.
QUESTION: What effects can x-rays have on the body?
ANSWER: Scientists have known for some time that exposure to
very large amounts of x-radiation is harmful. Changes can occur
in the reproductive system, altering the genetic material that
determines the health of future generations. Large amounts of
radiation can cause changes in the tissues of the body, including
the possibility of cancer.
On the other hand, diagnostic procedures involve very low
doses. With modern techniques and equipment, the amount
of radiation received in a dental exam is minuscule. Also
only a small part of the body is exposed (approximately the
region corresponding to the size of the image receptor).
Therefore, the risk of harmful effects from dental x-ray
exams is extremely small.
QUESTION: How do dental x-rays compare to other sources of
radiation?
ANSWER: We are exposed to radiation every day from various
sources, including outer space, minerals in the soil, and appliances in our homes (like smoke detectors and television
screens). Here is a sample of a comparison of radiation doses
from different sources:
QUESTION: Why do you use a lead apron?
ANSWER: Lead and other materials that simulate lead used in protective aprons and thyroid collars absorb potential scatter radiation
and protect other parts of your body from unnecessary radiation.
QUESTION: Why does the radiographer leave the room when
x-ray exposures are taken?
ANSWER: If the radiographer did not leave the room or stand
behind a barrier, he/she would be exposed many times a day to
radiation. Although the amount of radiation he/she would
receive each time is quite small, over a long period of time they
would receive a needless dose that provides no benefit to them.
QUESTION: If I am pregnant or think I may be pregnant,
should dental x-ray exams be postponed?
CHAPTER 12 • PATIENT RELATIONS AND EDUCATION 145
ANSWER: A 2004 study published in the Journal of the American Medical Association (JAMA, 291, 16) suggests that dental
radiography during pregnancy is associated with full-term,
low-birth-weight pregnancies. It is currently unclear whether
dental radiation affects the reproductive organs directly or
whether exposure to the head and neck area affects the thyroid
function and thereby indirectly affects pregnancy outcomes or
whether factors unrelated to radiation are responsible for the
low birth weight. Currently, the American Dental Association
recommends that pregnant women postpone elective dental xrays until after delivery and reinforces the importance of using
lead/lead equivalent thyroid collars in addition to abdominal
shielding (e.g., protective aprons). (Radiographs for the pregnant patient is discussed in Chapter 27.)
QUESTION: If I had radiation therapy for cancer of the head or
neck, should I avoid dental x-rays?
ANSWER: No. The dose of radiation required for dental x-rays
is extremely small compared to that used for radiation therapy.
The effects of very high doses involved in therapeutic radiation
may increase your susceptibility to diseases, such as tooth
decay. This can occur as a result of a decrease in secretions of the
salivary glands. It is especially important for you to have dental
x-ray exams as needed, to detect problems at an early stage.
(Radiographs for the cancer patient is discussed in Chapter 27.)
QUESTION: Can dental x-rays cause skin cancer?
ANSWER: There have been no recorded cases of patients developing cancer from modern diagnostic dental x-rays. In the early
days, prior to radiation safety standards, dentists who repeatedly
held the film in the patient’s mouth during exposures developed
cancer on their fingers.
QUESTION: What special precautions will you take to minimize the amount of radiation I receive?
ANSWER: There are several ways we minimize the amount of
radiation that you receive. First and foremost, only necessary
radiographs are taken. We use the fastest type of x-ray film currently available and use equipment that restricts the beam to the
area that needs to be examined. A lead/lead equivalent apron
and thyroid shield will be placed on you during the exposure,
and the films will be developed according to the manufacturer’s
recommendations to produce a high-quality image.
QUESTION: Who owns my dental radiographs?
ANSWER: The dentist owns all your dental records, including
the radiographs. You have the right of reasonable access to your
dental records, but they remain the property of the dentist.
QUESTION: Should I have my previous radiographs sent to my
new dentist?
ANSWER: Yes, if possible. These radiographs can reveal
your previous disease activity and may assist in determining
the need for a new x-ray exam. Although the dentist who
treated you in the past is considered the owner of your
records, including your x-rays, arrangements can usually be
made to have x-rays duplicated and sent to your new dentist.
You should contact your former dentist and request that this
be done.
REVIEW—Chapter summary
Effective communication is the key to producing quality radiographs. The radiographer must be a skilled communicator.
Patient relations affect the confidence level of the patient
and help the radiographer gain trust. The radiographer’s
appearance and attitude play a significant role in conveying
professionalism.
The attitude of the radiographer toward the patient, the radiographic procedure and his/her own technical ability, coworkers,
and employer will be conveyed to the patient. A positive, empathetic attitude will most likely generate a cooperative patient who
will accept treatment recommendations and embrace oral health
promotion and disease prevention. The radiographer should be
cognizant of the roles interpersonal skills and chairside manner
play in producing quality radiographs.
Honesty in verbal and nonverbal communication develops
trust. Nonverbal communication is often stronger than verbal
communication. Show-tell-do is an effective method of communication for all patients, especially when barriers to communication exist such as a language or cultural difference, a
sensory impairment, or a cognitive impairment.
Patient education is valuable in securing acceptance of treatment and in addressing concerns about the safety of the radiographic procedures. The entire oral health care team must be able
to provide the patient with complete explanations regarding the
need for radiographs. The methods of patient education include
oral presentations and the distribution of printed materials.
Examples of frequently asked questions and answers are
provided.
RECALL—Study questions
1. The key to producing quality radiographic images is
a. gaining patient trust and cooperation.
b. presenting a confident, caring image.
c. communicating effectively.
d. All of the above
2. List four aspects of patient relations that help to gain
confidence.
a. ______________
b. ______________
c. ______________
d. ______________
3. Dental radiographers with a positive attitude are more
likely to produce high-quality radiographs.
a. True
b. False
146 DENTAL RADIOGRAPHER FUNDAMENTALS
4. When a patient trusts the radiographer, the patient is more
likely to cooperate with the radiographic procedures.
a. True
b. False
5. The ability to share in the patient’s emotions and feelings is called
a. chairside manner.
b. atitude.
c. empathy.
d. verbal communication.
6. Each of the following will enhance verbal communication EXCEPT one. Which one is the EXCEPTION?
a. Face the patient.
b. Make eye contact.
c. Use clear commands.
d. Use slang words.
7. Which of the following words should be avoided when
discussing the radiographic procedure?
a. Picture
b. Zap
c. X-ray
d. Radiograph
8. The use of highly technical words may confuse the
patient and result in miscommunication.
a. True
b. False
9. The method of show-tell-do is a beneficial way of communicating with
a. someone who speaks a different language.
b. children.
c. hearing-impaired patients.
d. All of the above
10. What is the value of patient education regarding dental
radiographs?
a. Radiographer is more likely to spend less time
exposing radiographs.
b. Radiographer is more likely to develop a positive
attitude.
c. Patient is more likely to accept the treatment plan.
d. Patient is more likely to request radiographs at each
appointment.
11. Patient education in radiography is necessary to
a. increase the demand for oral health services.
b. increase acceptance of oral health care recommendations.
c. assure the patient that the radiographer is licensed.
d. meet legally required mandates for it.
12. List four things you could tell the patient in response to
his/her concerns regarding the necessity of dental x-rays
and the reduction of excess radiation exposure.
a. ______________
b. ______________
c. ______________
d. ______________
REFLECT—Case study
A new patient to your practice has just been examined by the
dentist, who has prescribed a set of vertical bitewings and a
panoramic radiograph. You escort the patient to the x-ray room
to prepare to expose the radiographs. At this time, the patient is
having second thoughts about consenting to the radiographic
surveys. She begins to question you about the procedure.
Respond to the questions listed. Write out your answers.
Together with a partner, role-play this scenario.
“Why do I need x-rays?”
“Why do I have to have bitewings and a panoramic x-ray?”
“How often should I have x-rays taken?
“Are you going to take the x-rays, or will the dentist take
them?”
“I’m a little nervous about having this done.”
“How long will it take?”
“What will you do to protect me from excessive exposure?”
RELATE—Laboratory application
Produce your own brochure for the purpose of educating
patients about the radiographic procedure. Give your brochure
a title, for example, “Dental X-Rays for Your Health,” or something similar. The narration should be simple and in language
that is professional, yet not overly technical. You may direct
your brochure to a target population. For example your
brochure may be for children or for a particular culture (e.g.,
for Spanish speakers). Include pictures of radiographs illustrating conditions that can be identified easily. Search the Web for
information and pictures to download (Table 12-1).
REFERENCES
American Dental Association. (2000). The benefits of dental
x-ray examinations. Chicago: ADA.
American Dental Association. (2000). Answers to common
questions about dental x-rays. Chicago: ADA.
Grubbs, P. A. (2003). Essentials for today’s nursing assistant.
Upper Saddle River, NJ: Prentice Hall.
Hujoel, P. P., Bollen, A. M., Noonan, C. J., & del Aguila, M. A.
(2004). Antepartum dental radiography and infant low
birth weight. JAMA, 291(16), 1987–1993.
Pulliam, J. L. (2006). The nursing assistant: Acute, sub-acute
and long-term care (4th ed.). Upper Saddle River, NJ:
Prentice Hall.
Thunthy, K. H. (1993). X-rays: Detailed answers to frequently
asked questions. Compendium of Continuing Education in
Dentistry, 14, 394–398.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Compare the three intraoral radiographic examinations.
3. Identify the two intraoral techniques.
4. List the five rules for shadow casting.
5. Determine conditions that effect the selection of image receptor size.
6. Select the type and number of image receptor required for a full mouth survey.
7. Explain horizontal and vertical angulation.
8. Explain point of entry.
9. List at least five contraindications for using the patient’s finger to hold the image
receptor during exposure.
10. Explain the basic design of image receptor positioners/holders.
11. Describe the proper patient seating position.
12. Demonstrate a systematic and orderly sequence of the exposure procedure.
KEY WORDS
Angulation
Bisecting technique
Biteblock
Bitewing radiograph
Conecut error
Film holder
Full mouth series (full mouth survey)
Horizontal angulation
Identification dot
Image receptor holder or positioner
Interproximal radiograph
Intraoral
Mean tangent
Midsaggital plane
Negative angulation
Occlusal plane
Occlusal radiograph
Paralleling technique
Periapical radiograph
Point of entry
Positive angulation
Rule of isometry
Shadow casting
Vertical angulation
Vertical bitewing radiograph
Intraoral Radiographic
Procedures
CHAPTER
13
PART V • INTRAORAL TECHNIQUES
CHAPTER
OUTLINE
\ Objectives 147
 Key Words 147
 Introduction 148
 Intraoral
Procedures 148
 Techniques 148
 Fundamentals
of Shadow
Casting 149
 The Radiographic
Examination 150
 Horizontal and
Vertical Angulation
Procedures 152
 Points of Entry 153
 Film Holders and
Image ReceptorPositioners 153
 Preparations and
Seating Positions 154
 Sequence of
Procedure 156
 Review, Recall,
Reflect, Relate 158
 References 160
148 INTRAORAL TECHNIQUES
Introduction
Intraoral radiography consists of methods of exposing dental
x-ray film, phosphor plates, or digital sensors within the oral
cavity. Producing diagnostic quality dental radiographs depends
on knowledge of and attention to:
• Positioning the patient in the chair
• Selecting a film, phosphor plate, or digital sensor of suitable size
• Determining how the image receptor is to be positioned
and held in place
• Setting the radiation exposure variables
• Aiming the position indicating device (PID)
Each of these steps have specific applications for each of the
three types of intraoral examinations and when utilizing the paralleling
or the bisecting technique. The purpose of this chapter is to introduce the
three types of intraoral examinations, explain the principles of
producing intraoral images (shadow casting), and describe the
fundamentals of image receptor holding devices to set the stage for
Chapters 13, 14, and 15, where an in-depth explanation of the
paralleling, bisecting, and bitewing techniques will follow.
Intraoral Procedures
Each of the three types of intraoral radiographic examinations
has a specific imaging objective.
1. Bitewing examination. Images the coronal portions of the
teeth and the alveolar crests of bone of both the maxilla and
mandible on a single radiograph (see Figure 7-6). The bitewing
examination, sometimes referred to as an interproximal
radiograph, is especially useful in detecting caries (dental
decay) of the proximal surfaces where adjacent teeth contact
each other in the arch. Bitewing radiographs are also used to
examine crestal bone of patients with periodontal disease.
The technique used to image bitewing radiographs is unique
to the bitewing exam. However, because of the almost parallel
relationship of the image receptor to the teeth, the bitewing
technique could be considered to be a modification of the
paralleling technique used for exposing periapical radiographs.
2. Periapical examination. The purpose of periapical radiographsis to image the apices of the teeth and the surrounding
bone (see Figure 7-7). The word periapical is derived from the
Greek word peri (meaning around) and the Latin word apex
(meaning highest point). Therefore, as the word suggests, the
periapical radiograph images the entire tooth, including the
root end and surrounding bone. The periapical radiograph
may be used to examine a single tooth or condition or may be
used in combination with other periapical and bitewing radiographs to image the entire dentition and supporting structures
(full mouth series; Figure 13-1). Conditions prompting the
exposure of a periapical radiograph include apical pathology
(abscesses), fractures, large carious lesions (Figure 13-2),
extensive periodontal involvement (Figure 13-3), examination of
developmental anomalies such as missing teeth and abnormal
eruption patterns, and any unexplained pain or bleeding.
Periapical radiographs may be taken utilizing either the
paralleling or the bisecting technique.
3. Occlusal examination. Images the entire maxillary or
mandibular arch, or a portion thereof, on a single radiograph (see Figure 17-1). Occlusal radiographs are most
often taken with a larger size #4 intraoral film, making this
examination useful in imaging large areas of pathology
that may not be adequately imaged on a smaller periapical
radiograph. Conditions that may prompt the exposure of
occlusal radiographs include cysts, fractures, impacted or
supernumerary (extra) teeth, and in locating the buccal or
lingual position of foreign objects (see Chapter 28). The
technique used to image occlusal radiographs is unique to
the occlusal exam. However, because of the image receptor
placement required, the occlusal technique could be considered a modification of the bisecting technique.
Techniques
Two basic techniques are used in intraoral radiography: paralleling and bisecting. Either technique can be modified to meet
special conditions and requirements. Although each technique
will produce diagnostic quality radiographic images if the fundamental principles of the technique are followed, paralleling is
the technique of choice because it is more likely to satisfy more
of the shadow casting requirements.
The concept of the bisecting technique (also called the
bisecting-angle or short-cone technique) originated in 1907
through the application of a geometric principle known as the
rule of isometry. This theorem states that two triangles having equal angles and a common side are equal triangles (see
Figure 15-1). The bisecting technique was the only method
used for many years. However, because many radiographers
FIGURE 13-1 Full mouth series. The 20-film
radiographic survey includes four bitewing
radiographs and eight anterior and eight posterior
periapical radiographs.
CHAPTER 13 • INTRAORAL RADIOGRAPHIC PROCEDURES 149
1
2
3
FIGURE 13-2 Periapical radiograph. Posterior periapical
radiograph showing (1) extensive caries, (2) apical pathology, and
(3) impacted third molar. Note the use of a size #2 film and the
horizontal positioning of the long dimension of the film packet for
imaging the posterior regions.
FIGURE 13-3 Periapical radiograph. Anterior periapical
radiograph showing extensive periodontal involvement. Note the use
of a size #1 film and the vertical positioning of the long dimension of
the film packet for imaging the anterior regions.
experienced difficulties and obtained unsatisfactory results,
the search for a less-complicated technique that would produce better radiographs more consistently resulted in the
development of the paralleling technique in 1920. The
paralleling technique (also called right-angle, extensioncone, or long-cone technique) is considered to be the technique of choice because better-quality radiographs are
produced with this technique. The specific steps of each of these
two techniques are discussed in detail in Chapters 14 and 15.
Fundamentals of Shadow Casting
X-rays produce an image on a film, phosphor plate, or digital
sensor in a similar manner as light casting a shadow of an object.
When a hand is placed between a nearby light source such as an
electric bulb and a flat object such as a tabletop, a shadow of the
hand is seen on the tabletop. In dental radiography, x-rays cast a
shadow of the teeth on to the image receptor.
The radiograph is essentially a shadow image. To produce
an image that represents the teeth and supporting structures
accurately, the x-ray beam must be directed at the structures and
the image receptor at certain angles. The function of the image
receptor is to record the shadow image. To produce the best
image, it is important to understand the fundamentals of shadow
casting. Shadow casting refers to five basic rules for casting a
shadow image (see Chapter 4).
1. Use the smallest possible focal spot on the target (source of
radiation).
2. The object (tooth) should be as far as practical from the target
(source of radiation).
3. The object (tooth) and the image receptor (film, phosphor
plate, or digital sensor) should be as close to each other as
possible.
4. The object (tooth) and the image receptor (film, phosphor
plate, or digital sensor) should be parallel to each other.
5. The radiation (central ray) must strike both the object (tooth)
and the image receptor (film, phosphor plate, or digital sensor)
at right angles (perpendicularly).
Neither the paralleling nor the bisecting technique completely meets all five requirements for accurate shadow casting
in all regions of the oral cavity on all patient types. With the
bisecting technique, it is often not possible to position the
image receptor parallel to the object, preventing the radiation
from striking the object and the image receptor at right angles.
With the paralleling technique, the distance between the object
and the image receptor is often greater than ideal in most
regions of the oral cavity. However, the paralleling technique is
more likely to meet most of these requirements, making the
technique less likely to produce image distortion. For this reason, the paralleling technique is the recommended technique
(Figures 13-4 and 13-5).
FIGURE 13-4 Principle of the paralleling technique.
Positioning the recording plane parallel to the long axis of the tooth
and directing the x-ray beam perpendicular to both the recording
plane and the long axis of the tooth produces an image with less
distortion. (Courtesy of Dentsply Rinn.)
150 INTRAORAL TECHNIQUES
Although the paralleling technique produces superior
diagnostic quality radiographs, not all patients present with
conditions that allow for the use of the paralleling technique. When
use of the paralleling technique is difficult, a reasonably acceptable
quality radiograph may be produced using the bisecting technique.
For this reason, the radiographer who is skilled in both paralleling
and bisecting techniques will be better prepared to produce
quality radiographs in most all situations.
The Radiographic Examination
Size, Number, and Placement of Image Receptors
The size #4 film or phosphor plate is used exclusively for
occlusal radiographs of adult patients, and the size #3 film or
phosphor plate is used exclusively for horizontal bitewing
radiographs of adult patients. Bitewing and periapical radiographs of adults, adolescents, and children can be made with
any of the three intraoral film, phosphor plates, or digital sensor
sizes (#0, #1, #2) or any combination of these sizes. The size of
the image receptor selected for use depends on:
• The age of the patient
• The size of the oral cavity
• The shape of the dental arches
• The presence or absence of unusual conditions or anatomical
limitations
• The patient’s ability to tolerate placement of the image
receptor
• The image receptor positioner or holder and technique used
The bitewing survey may consist of two to eight radiographs. A
complete set of seven or eight vertical bitewing radiographs
may be exposed for the examination of a periodontally involved
patient. This vertical bitewing set will include both posterior and
anterior bitewings. When the patient does not require anterior
bitewings, two or four posterior bitewing radiographs positioned
either vertically or horizontally are usually taken (see Figure 15-5).
When the periapical and bitewing examinations include a series
of radiographs that image all the teeth, the term full mouth
series or full mouth survey is used to describe the collection
of radiographs (Figure 13-1).
The number and size of image receptors used for a full mouth
series of bitewing and periapical radiographs varies among oral
health care practices. A minimum of 4 bitewing and 14 periapical
radiographs (Figure 13-6) make up a full mouth survey for most
adult patients. The four bitewing radiographs are used to image
the following regions:
• One radiograph each for the right and left premolar regions
• One radiograph each for the right and left molar regions
The 14 periapical radiographs are used to image the following
regions:
• One radiograph each for the maxillary and mandibular
incisor regions
• One radiograph each for the right and left maxillary and
mandibular canine regions
• One radiograph each for the right and left maxillary and
mandibular premolar regions
• One radiograph each for the right and left maxillary and
mandibular molar regions
Although most oral health care practices will use eight size
#2 image receptors for the exposure of the posterior periapicals
on an adult patient, the number and size of image receptors
used for the exposure of the anterior teeth varies. The general
rule is to use the largest image receptor that can readily be positioned to minimize the number of exposures. However, more
films or more exposures of a digital sensor may be required for
unusual conditions or for narrow arches requiring a smaller size
image receptor. A size #1 image receptor is often used instead
of the size #2 image receptor for exposures of the anterior teeth.
However, the narrow size #1 image receptor may require the use
of additional exposures to completely record the region. Three
examples of image receptor combinations for use in recording
the images for anterior periapical radiographs using the narrow
#1 size or the standard #2 size are:
• Eight anterior exposures. Five size #1 image receptors
may be used for the exposure of the maxillary anterior
teeth (Figure 13-7A). One image receptor is centered at the
midline behind the central incisors, one image receptor
each is centered behind the right and left lateral incisors,
and one image receptor each is centered behind the right
and left canines. Three size #1 image receptors are used for
the exposure of the mandibular arch, where the teeth are
smaller. One image receptor is centered behind the central
and lateral incisors, and one image receptor each is centered
behind the right and left canines.
• Eight anterior exposure. Four size #1 image receptors
may be used for the exposure of the maxillary anterior
teeth (Figure 13-7B). One image receptor each is centered
behind the right and left central and lateral incisors, and
one image receptor each is centered behind the right and
left canines. Four size #1 image receptors are used for the
exposure of the mandibular anterior teeth in much the
same way as for the maxilla. One image receptor each is
centered behind each of the right and left central and lateral incisors, and one image receptor each is centered
behind the right and left canines.
FIGURE 13-5 Principle of the bisecting technique. The x-ray
beam is directed perpendicular to the imaginary line that bisects the
angle formed by the recording plane and the long axis of the tooth.
Because the tooth is a three–dimensional object, the part of the object
farthest from the recording plane is projected in an incorrect
relationship to the parts closest to the recording plane. (Courtesy of
Dentsply Rinn.)
CHAPTER 13 • INTRAORAL RADIOGRAPHIC PROCEDURES 151
B
C
A
FIGURE 13-7 Maxillary anterior image receptor placement. (A) Five-image survey.
(B) Four-image survey. (C) Three-image survey.
• Six anterior exposures. Three size #1 or three size #2
image receptors may be used for the exposure of the maxillary anterior teeth (Figure 13-7C). One image receptor is
centered at the midline behind the central and lateral
incisors, and one image receptor each is centered behind
each of the right and left canines. The three size #1 or three
size #2 image receptors used for the exposure of the
mandibular arch are positioned in the same manner as
described earlier, where one image receptor is centered
behind the central and lateral incisors and one image
receptor each is centered behind the right and left canines.
Although the use of size #2 image receptor for anterior
periapical radiographs is acceptable, the narrower size #1
image receptor usually fits this area better. When using the
size #2 film packet or phosphor plate in the anterior region,
there is a tendency to bend the film packet or plate corners
FIGURE 13-6 Full mouth series. Drawing of 18-image full mouth survey includes 14 periapical
and 4 bitewing radiographs.
152 INTRAORAL TECHNIQUES
Horizontal and Vertical Angulation
Procedures
Angulation is defined as the procedure by which the tube head
and PID are aligned to obtain the optimum angle at which the
radiation is to be directed toward the image receptor. Angulation
is changed by rotating the tube head horizontally and vertically.
The x-ray machine is constructed with three swivel joints to support
to make it fit more comfortably. Bending the image receptor will result in a distorted image and/or radiolucent or
radiopaque creases. Some patients present with a narrow
anterior region that may make positioning the size #2 digital sensor difficult. Some practices utilize one size #2
image receptor for the exposure of the maxillary central
and lateral incisors, where the area is the widest, and use
size #1 image receptors to expose the remaining five areas.
See Table 13-1 for a list of the various combinations of standard placements of the film packet, phosphor plate, or digital sensor for each of the periapical radiographs of a full mouth series.
Orientation of the Image Receptor
With few exceptions, for exposure of the anterior regions of the
oral cavity the film packet, phosphor plate, or digital sensor is
placed with the longer dimension vertical (described as vertical
placement; Figure 13-3). For exposure of the posterior regions the
image receptor should be placed with the longer dimension horizontal (described as horizontal placement; Figure 13-2). The
white, unprinted side of the film packet (front side) must face the
source of radiation. Depending on the manufacturer, the plain side
of the phosphor plate, or side without the cord attachment of the
digital sensor, should be placed to face the source of radiation.
When placing a film packet for periapical radiographs, it is
important to make note of where the identification dot is located.
The identification dot, embossed into the film by the manufacturer, will be utilized during interpretation of the radiograph to
distinguish between the patient’s right and left sides (see
Chapter 21). There is a tendency for the embossed identification
TABLE 13-1 Standard Image Receptor Placements for Periapical Radiographs of a
Full Mouth Series
PERIAPICAL RADIOGRAPH IMAGE RECEPTOR PLACEMENT
Maxillary central incisors (size #1
or size #2)
Center the image receptor to line up behind the central and lateral incisors; if using
size #2, include the mesial halves of the canines.
Maxillary central and lateral
incisors (size #1)
Center the image receptor to line up behind the central and lateral incisors; include the
distal half of the central incisor on the opposite side and the mesial half of the canine.
Maxillary lateral incisor
(size #1)
Center the image receptor to line up behind the lateral incisor; include the distal half
of the central incisor and the mesial half of the canine.
Maxillary lateral incisor and canine
(size #1)
Center the image receptor to line up behind the lateral incisor and canine; include
the distal half of the central incisor and the mesial half of the premolar.
Maxillary canine (size #1 or
size #2)
Center the image receptor to line up behind the canine; include the distal half of the
lateral incisor and the mesial half of the first premolar.
Mandibular central incisors (size
#1 or size #2)
Center the image receptor to line up behind the central and lateral incisors; if using a
size #2 film, include the mesial halves of the canines.
Mandibular central and lateral
incisors (size #1)
Center the image receptor to line up behind the central and lateral incisors; include the
distal half of the central incisor on the opposite side and the mesial half of the canine.
Mandibular canine (size #1 or size
#2)
Center the image receptor to line up behind the canine; include the distal half of the
lateral incisor and the mesial half of the first premolar.
Maxillary and mandibular
premolar (size #2)
Align the anterior edge of the image receptor to line up behind the distal half of the
canine; include the entire first and second premolars and mesial half of the first molar.
Maxillary and mandibular molar
(size #2)
Align the anterior edge of the image receptor to line up behind the distal half of the
second premolar; include the entire first, second, and third molars.
dot to distort images, so during film packet placement it is important to position the identification dot away from the area of interest. In the case of periapical radiographs, the identification dot
should be positioned toward the incisal or occlusal edges, where
it is least likely to interfere with diagnostic information.
PRACTICE POINT
When using a film-holding device with a film slot, it is helpful to remember that “dot in the slot” will position the
embossed identification dot away from the apices of the
teeth where it could interfere with diagnosis. Dot in the slot
will position the identification dot toward the incisal or
occlusal edges for both maxillary and mandibular periapical
radiographs.
CHAPTER 13 • INTRAORAL RADIOGRAPHIC PROCEDURES 153
positive (plus) angulations. Those in which the PID is tipped
upward to direct the x-rays toward the ceiling are called
negative (minus) angulations. Positive angulation, the
positioning of the central ray (PID) downward toward the floor,
is used for exposure of bitewing radiographs and generally used
for the exposure of periapical radiographs of the maxillary arch.
Negative angulation, the positioning of the central ray
(PID) upward toward the ceiling, is generally used for the exposure of periapical radiographs of the mandibular arch. Although
the vertical angulation setting for the exposure of bitewing radiographs for the adult patient is for all regions of the oral cavity, the precise vertical angulation setting for periapical
radiographs is determined differently depending on the technique used (see Chapters 14 and 15).
Points of Entry
The image receptor must be centered within the beam of radiation to avoid conecut error, where a portion of the image is not
recorded on the radiograph. The point of entry for the central
ray should be in the middle for the image receptor. A film holder
or image receptor postioner with an external aiming device will
assist the radiographer with determining the point of entry. The
portion of the holder, or biteblock, that extends from the oral cavity can be used to estimate the center of the image receptor when
using a holder without an external indicator. The open end of the
PID should be placed as close to the patient’s skin as possible
without touching. Failure to bring the end of the PID in close to
the patient will result in an underexposed radiograph because as
the beam of radiation spreads out, less radiation is available to
strike the image receptor and produce a diagnostic quality image.
Film Holders and Image
Receptor Postioners
Film holders and holders designed to position a phosphor plate
or digital sensor are collectively called image receptor holders
or positioners. These devices are used to hold the image receptor in place to expose intraoral radiographs. When the bisecting
+10
1-2
1+2
the yoke and tube head. One of these, located at the top and center of the yoke where it attaches to the extension arm, permits
horizontal movement of the tube head to control the
anterior–posterior dimensions. The other two swivel joints are
located at either side of the yoke. These permit the tube head to
be rotated up or down in a vertical direction to control the longitudinal dimensions of the resulting image. Determining the correct direction of the central beam in the horizontal and vertical
planes requires practice.
The correct horizontal and vertical angulations are critical
to producing a quality radiograph.
Horizontal Angulation
Horizontal angulation is achieved by directing the central rays
perpendicularly (at a right angle) toward the surface of the
image receptor in a horizontal plane (Figure 13-8). To change
direction, swivel the tube head from side to side. The central ray
(PID) should be directed perpendicular to the curvature of the
arch, through the contact points of the teeth. The horizontal
angulation is established by directing the central rays perpendicularly through the mean tangent of the embrasures between
the teeth of interest. Incorrect alignment in the horizontal plane
caused by incorrect angulation toward the mesial or the distal
results in overlapping of adjacent tooth structures shown on the
radiograph. The steps to determining correct horizontal angulation are the same for both the bisecting and paralleling methods
and for exposing bitewing radiographs.
Vertical Angulation
Vertical Angulation is achieved by directing the central rays
perpendicularly (at a right angle) toward the surface of the
image receptor in a vertical plane (Figure 13-9). Vertical angulation is customarily described in degrees. On most dental x-ray
machines the vertical angles are scaled in intervals of 5 or 10
degrees on one or both sides of the yoke where the tube head is
connected. The vertical angulation of the tube head and the PID
begins at zero. In the zero position the PID is parallel to the
plane of the floor. All deviations from zero in which the PID is
tilted downward to direct the x-rays toward the floor are called
A Maxilla B Mandible
FIGURE 13-8 Horizontal angulation. Horizontal angulation is determined by directing the
x-ray beam directly through the interproximal spaces perpendicular to the mean tangent of the
teeth. The image receptor must be positioned parallel to the teeth of interest so that the central
ray will also strike the image receptor perpendicularly.
154 INTRAORAL TECHNIQUES
type of receptor (film, phosphor plate, or sensor) for which it
was designed, to achieve optimal results.
It is beneficial to have a variety of image receptor positioners
available, because one type of holder may not be suitable for all
patients, or even all areas of the same patient’s mouth. Additionally, the operator may have to alternate between the paralleling
and the bisecting technique to complete a full mouth series on a
patient.
Preparations and Seating Positions
Unit Preparation
Prior to placing the image receptor intraorally, the x-ray unit
should be turned on and the exposure settings selected. It is
helpful to place the tube head and PID in the approximate
position for the exposure to limit the time required for this
step once the image receptor has been placed into the patient’s
oral cavity.
technique was first introduced in 1907, film holders and image
receptor positioners did not yet exist. Instead, the patient was
directed to hold the film packet in the mouth using a finger or
thumb. Asking the patient to hold the film packet in this manner
has many disadvantages, and this practice is no longer acceptable (Box 13-1). Image receptor positioners and holders vary
from simple disposable biteblocks that require no sterilization to
complex devices that position the image receptor at the correct
angles for directing the x-ray beam in relation to the teeth and
image receptor (Figures 13-10 and 13-11.) Some commercially
manufactured image receptor holders are designed specifically
for use with the bisecting technique or specifically for use with
the paralleling technique. Some holders may be slightly altered
to accommodate both techniques (Figure 13-12). Other manufactures offer interchangeable biteblocks to accommodate either
technique and placement of a film packet, phosphor plate, or
digital sensor (Figure 13-13). It is important that the radiographer match the image receptor biteblock with the technique and
BOX 13-1 Contraindications for Using the Patient’s Finger to Hold the Film Packet,
Phosphor Plate, or Digital Sensor in Place
• Potential for bending the image receptor.
• Potential to move the image receptor from the
correct position.
• Increased patient instruction and cooperation required.
• Potential patient objection to placing the fingers in
the mouth.
• Radiation exposure to the patient’s fingers.
• No external aiming device to assist with aligning the x-ray beam
to the correct position.
• Potential to be viewed by the patient as unprofessional and
unsanitary.
90°
90° 80° 70° 60°
50°
40°
30°
20°
10°
10°
0°
20°
30°
40°
50°
60° 70° 80°
PID
−45°
+45°
Zero
angulation
angulation
Negative
angulation
Positive
Plane of floor
Occlusal
plane
Midsagittal
plane
FIGURE 13-9 Vertical angulation. Diagram showing
patient sitting in the recommended position upright in
dental chair with midsagittal plane perpendicular to and
occlusal plane parallel with the floor. Zero angulation is
achieved when the long axis of the PID is directed parallel
with the floor. All angulations achieved with the PID
pointed toward the floor are called positive, or plus
angulations. All angulations achieved with the PID is
pointed toward the ceiling are called negative, or minus
angulations. Generally a positive angle is used for
bitewing exposures and periapical exposures of the
maxilla, and a negative angle is used for periapical
exposures of the mandible.
1-2
1+2
CHAPTER 13 • INTRAORAL RADIOGRAPHIC PROCEDURES 155
A
B
FIGURE 13-13 Film holders. The extension arm and aiming ring
of the Rinn XCP® (Dentsply Rinn) instrument may be combined with
a (A) biteblock suitable for the paralleling technique or a
(B) biteblock suitable for the bisecting technique.
A B
FIGURE 13-10 Rinn XCP paralleling technique film
holders. Color-coded rings and biteblocks assist with assembly of
multiple parts. Note the mirror-image assembly of these posterior
periapical film holders. Assembly A is used for exposures on the
maxillary right and the mandibular left, whereas assembly B is used
for exposures on the maxillary left and on the mandibular right.
FIGURE 13-11 Rinn XCP ORA (one ring and arm)
positioning system. Color-coded pins on the metal arm match the
colored inserts on the plastic ring. When matched with the
appropriate biteblocks, it can be configured for exposures in all
regions of the oral cavity with either film or digital sensors.
FIGURE 13-12 Stabe® (Dentsply Rinn). Bite extension
required for use with the paralleling technique may be broken off for
use with the bisecting technique.
Patient Preparation
To help gain patient cooperation and confidence, it is important to explain the procedure. Include specific instructions
regarding the need for patient cooperation and be honest about
any difficulties anticipated (see Chapter 12). Perform a cursory
oral inspection and ask the patient to remove any objects from
the mouth that would interfere with the procedure, such as
removable dentures or orthodontic appliances, chewing gum,
and so on. Ask the patient to remove eyeglasses; if any metal
or thick plastic parts of the eyeglasses remain in the path of the
x-ray beam, they will be imaged onto the radiograph. Protect
the patient with the lead or lead equivalent apron and thyroid
collar barriers.
Patient Seating Position
If the image receptor holder has an external aiming device, the
patient’s head can be in any position. Without these special
holders that indicate x-ray beam positions, patients must be
seated upright with their head straight. This position is necessary for consistent results in determining the best horizontal
PRACTICE POINT
Seating the patient with the head against the headrest not
only helps position the occlusal and midsaggital planes, but
the patient is much less likely to move during the exposures
when his/her head is firmly supported by the headrest.
Additionally, Chapter 27 states that directing the patient’s
attention to the back of the head where it touches the
headrest (the occipital protuberance) can serve as a distraction technique when needed (for example, when an exaggerated gag reflex presents).
156 INTRAORAL TECHNIQUES
Plane C
A
B
O
X
Y
FIGURE 13-15 Head divided by midsagittal plane and
occlusal plane. The midsagittal plane (A–B) must be
perpendicular to the floor, and the occlusal plane (C) must be
parallel with the floor unless an image receptor with an external
aiming device is used. The lines O–X and X–Y are the lines of
orientation for the maxillary teeth, also known as the ala–tragus
line. The apices of the roots of the maxillary teeth are located
close to this line.
A B
FIGURE 13-14 Patient positioning. The patient is positioned with the head supported against the headrest with
the (A) occlusal plane parallel to the floor and the (B) midsaggital plane perpendicular to the floor.
Sequence of Procedure
A definite sequence of positioning the image receptor should
be followed to prevent omitting an area or exposing an area
twice. Develop a set routine to prevent errors and save time.
Opinions differ as to which region should be exposed first
when taking a full mouth series of periapical and bitewing radiographs. Some radiographers prefer to begin in the right maxillary molar region and continue in sequence to the left maxillary
molar region, drop down to the left mandibular molar region, and
finish in the right mandibular molar region.
Others begin with the anterior exposures, on the theory that
the image receptor placement is more comfortable here and less
likely to excite a gag reflex than when it is placed in the maxillary molar region, where the tissues may be more sensitive (see
Chapter 27). If the first few placements produce no discomfort,
the patient may become used to the feel of the image receptor
and may more readily accept it as the procedure continues.
For an experienced radiographer who can place the image
receptor skillfully and rapidly, it probably makes little difference which area is exposed first. However, the same order for
placement of the image receptor should always be followed to
make sure that all regions are exposed in an orderly and efficient
manner. The following sequence of image receptor placements
is suggested to help the student adopt a systematic routine:
• Maxillary anterior periapicals
• Mandibular anterior periapicals
• Maxillary posterior periapicals
• Mandibular posterior periapicals
• Anterior bitewings
• Posterior bitewings
Anterior image receptor placements are often more comfortable and allow the patient to become accustomed to the
and vertical angulations of the x-ray beam and points of entry.
Additionally, stabilizing the patient’s head against the headrest
is important to prevent movement during the exposure. Place
the headrest against the occipital protuberance (the back, base
of the skull) for greatest stability.
The recommended position is to seat the patient upright
and adjust the headrest so that the occlusal plane for the arch
being examined is parallel to the floor (Figure 13-14). The
midsagittal plane that divides the patient’s head into a right
and left side should be positioned perpendicular to the floor
(Figure 13-15). Although an experienced radiographer can
expose radiographs with the patient either upright or supine, the
use of predetermined head positions is recommended to standardize the procedure.
CHAPTER 13 • INTRAORAL RADIOGRAPHIC PROCEDURES 157
PROCEDURE 13-1
Procedure for exposing a full mouth series of radiographs
1. Perform infection control procedures (see Procedure Box 10-2).
2. Prepare unit. Turn on and set exposure factors.
3. Seat patient and explain the procedure.
4. Request that the patient remove objects from the mouth that can interfere with the procedure and
remove eyeglasses.
5. Adjust chair to a comfortable working level.
6. Adjust the headrest to position the patient’s head so that the occlusal plane of the arch being imaged is
parallel to the floor and the midsagittal plane (midline) is perpendicular to the floor.
7. Place the lead or lead-equivalent barrier apron and thyroid collar on the patient.
8. Perform a cursory inspection of the oral cavity and note possible obstructions (tori, shallow palatal vault,
malaligned teeth) that may require an alteration of technique or number of exposures.
9. Place the image receptor into the positioner. When using film, place such that the embossed dot will be
positioned toward the occlusal/incisal edge (“dot in the slot”). Position anterior image receptors vertically and posterior image receptors horizontally.
10. Insert the image receptor and positioner into the patient’s oral cavity and center the receptor behind the
teeth to be imaged. (See Table 14-5 for the exact placements for each of the maxillary and mandibular
periapical radiographs and Table 16-3 for placements for each of the posterior and/or anterior bitewing
radiographs in the procedure.) Visually locate the contact points of the teeth to be imaged and place the
image receptor perpendicular to the embrasures.
11. Hold the image receptor holder against the occlusal/incisal surface of the maxillary/mandibular teeth
while asking the patient to bite firmly onto the biteblock of the holder. (Use a sterilized cotton roll for
stabilization if needed.)
12. Release the image receptor postioner when the patient has closed firmly, holding it in place.
13. Set the vertical angulation:
a. For periapical radiographs: (See Table 14-5 for the recommended vertical angulation setting for the
area being imaged.)
1. Intersect the image receptor plane and the long axes of the teeth perpendicularly when utilizing
the paralleling technique. If using an image receptor positioner with an external aiming device,
align the open end of the PID with the indicator ring.
2. Intersect the imaginary bisector of the receptor plane and the long axes of the teeth perpendicularly when utilizing the bisecting technique.
b. For bitewing radiographs use degrees.
14. Determine the correct horizontal angulation by directing the central ray of the x-ray beam perpendicular
to the receptor in the horizontal plane through the contact point of the teeth of interest. (See Table 14-5
for the exact embrasure space through which to direct the central ray for each of the periapical radiographs and Table 16-3 for each of the bitewing radiographs in the procedure. Horizontal angulation is
determined the same for both paralleling and bisecting techniques and for bitewing radiographs.) If
using an image receptor positioner with an external aiming device, align the open end of the PID with
the indicator ring.
+10
procedure. The bitewing examination (see Chapter 16) is last
because the patient tolerates these fairly well, and the radiographic procedure can end pleasantly. In addition, it may be
helpful for the radiographer not to have to break the sequence
of exposing periapical radiographs by switching to a bitewing
holder and changing techniques in the middle of the procedure.
Procedure Box 13-1 summarizes the steps for exposing a full
mouth series of radiographs.
(Continued)
158 INTRAORAL TECHNIQUES
to the plane of the image receptor and the long axes of the teeth
when utilizing the paralleling technique. When utilizing the
bisecting technique, the vertical angulation is determined by
directing the central rays of the x-ray beam perpendicular to the
imaginary bisector. The vertical angulation setting for exposing
bitewings is
The point of entry is used to center the image receptor
within the beam of radiation.
Before image positioners were developed, the patient
would hold the film packet in the oral cavity with the fingers or
a thumb. With the variety of image receptor positioners currently on the market, this practice is unacceptable today. Film
holders are designed for use with the paralleling or the bisecting technique or may be modified to use with both techniques.
Unless the image receptor holder has an external aiming
device to indicate the correct angulation, care must be taken to
seat the patient so that the occlusal plane is parallel with the
floor and that the midsaggital plane is perpendicular to the floor.
An exposure sequence is recommended to avoid error and
be efficient. Anterior image receptor placements may be more
comfortable for some patients. Beginning the exposure sequence
in the anterior may assist in gaining patient cooperation with
the procedure.
RECALL—Study questions
1. Which of these is NOT an intraoral radiograph?
a. Bitewing
b. Occlusal
c. Panoramic
d. Periapical
2. Which radiograph is used most often to detect proximal
surface dental decay?
a. Bitewing
b. Occlusal
c. Panoramic
d. Periapical
+10.
PROCEDURE 13-1
Procedure for exposing a full mouth series of radiographs (continued)
15. Center the PID over the image receptor. If using an image receptor positioner with an external aiming
device, align the open end of the PID with the indicator ring. (See Table 15-4 for point of entry recommendations when utilizing the bisecting technique.)
16. Make the exposure.
17. Remove the image receptor and positioner from the patient’s oral cavity.
18. Repeat steps 9 through 17 until all radiographs in the series have been exposed.
19. Remove the lead or lead equivalent barrier apron and thyroid collar from the patient.
20. Perform infection control procedures following the exposures (see Procedure Box 10-4).
REVIEW—Chapter summary
The three types of intraoral radiographic procedures are the bitewing, periapical, and occlusal surveys. Each of these examinations
differs in purpose, and a variety of image receptor sizes may be
used to achieve the desired result.
Both the bisecting and the paralleling techniques are used
to produce a shadow image of the tooth onto the radiograph.
Although neither technique completely satisfies all the requirements for accurate shadow casting, the paralleling technique is
more likely to produce superior results. Each technique has
advantages and disadvantages. The skilled operator, within the
limits of the equipment available, must select the technique that
fits the situation.
The size and number of image receptors used for exposure
of a full mouth radiographic survey depends on several factors.
A bitewing series may consist of two to eight radiographs. A
minimum of 14 periapical radiographs are required for a full
mouth series of an adult patient—additional images may be
needed if narrow size #1 image receptors are used in the anterior regions. Exposures include the central incisor, canine, premolar, and molar areas of the right and left maxilla and
mandible. The image receptor should be positioned with the
long dimension vertical in the anterior region and horizontal in
the posterior region. The embossed identification dot present
on radiographic film should be placed toward the
incisal/occlusal edges of the teeth when positioning the film
packet for periapical radiographs.
The horizontal angulation is determined by directing the
central rays of the x-beam perpendicular to the plane of the
image receptor through the mean tangent of the embrasures
between the teeth of interest. Both paralleling and bisecting
techniques and bitewing procedures determine horizontal angulation in the same manner.
With negative vertical angulation, the PID is pointing down
toward the floor. With positive vertical angulation, the PID is
pointing up toward the ceiling. The vertical angulation is determined by directing the central rays of the x-beam perpendicular
CHAPTER 13 • INTRAORAL RADIOGRAPHIC PROCEDURES 159
3. Which intraoral technique satisfies more shadow casting principles?
a. Bisecting
b. Paralleling
4. Which intraoral technique is based on the rule of isometry?
a. Bisecting
b. Paralleling
5. Each of the following is a shadow casting principle
EXCEPT one. Which one is the EXCEPTION?
a. Object and image receptor should be perpendicular
to each other.
b. Object and image receptor should be as close as possible to each other.
c. Object should be as far as practical from the target
(source of radiation).
d. Radiation should strike the object and image receptor perpendicularly.
6. Which of these factors does NOT need to be considered
when deciding which image receptor size to use when
exposing a full mouth series?
a. Age of the patient
b. Shape of the dental arches
c. Previous accumulated exposure
d. Patient’s ability to tolerate the image receptor
7. What is the minimum image receptor requirement for
an adult full mouth series of periapical radiographs?
a. 12
b. 14
c. 16
d. 18
8. How many size #2 image receptors are required by most
health care practices for the exposure of posterior radiographs of a full mouth series?
a. 5
b. 6
c. 7
d. 8
9. Lining the image receptor up behind the right and left
central and lateral incisors to include the mesial half
of the right and left canines describes the image
receptor placement for which of the following periapical radiographs?
a. Central incisors
b. Canines
c. Premolars
d. Molars
10. Anterior periapical image receptors are placed
______________ in the oral cavity. Posterior periapical
image receptors are placed _____________ in the oral
cavity.
a. vertically; horizontally
b. horizontally; vertically
c. vertically; vertically
d. horizontally; horizontally
11. Where should the embossed identification dot be
positioned when taking periapical radiographs?
a. Toward the midline of the oral cavity
b. Toward the incisal or occlusal edge of the tooth
c. Toward the palate or floor of the mouth
d. Toward the distal or back of the arch
12. The x-ray tube head must be swiveled from side
to side to adjust the vertical angulation of the
central ray.
To avoid overlap error the central ray must be directed
perpendicular to the curvature of the arch through the
contact points of the teeth.
a. Both statements are true.
b. Both statements are false
c. The first statement is true. The second statement is
false.
d. The first statement is false. The second statement is
true.
13. At which of the following settings would the PID be
pointing to the floor?
a.
b. 0
c.
14. An incorrect point of entry will result in
a. overlapping.
b. foreshortening.
c. cutting off the root apices.
d. conecutting.
15. List five contraindications for using the patient’s finger
to hold a film packet in position during exposure.
a. ______________
b. ______________
c. ______________
d. ______________
e. ______________
16. An image receptor positioner/holder must be used
with
a. the paralleling technique.
b. the bisecting technique.
c. the bitewing technique.
d. all of the above techniques.
17. Which of the following is the correct seating position
for the patient during radiographic examinations when
an image receptor without an external aiming device is
used?
a. Occlusal plane parallel and midsaggital plane perpendicular to the floor
b. Occlusal plane perpendicular and midsaggital plane
parallel to the floor
c. Occlusal and midsaggital planes parallel to the
floor
d. Occlusal and midsaggital planes perpendicular to the
floor
+20
-30
160 INTRAORAL TECHNIQUES
2. Observe and describe the orientation of the image
receptor in each position. Give a rationale for why the
image receptor is positioned with the long dimension
vertical or horizontal in different regions of the oral
cavity.
3. If using intraoral film packets, where did you position
the embossed dot? Why?
4. Explain the order you used to position each of the radiograph.
Next practice positioning the x-ray tube head in relation
to each of the standard image receptor placements. Using the
paralleling technique, determine the horizontal angulation by
swiveling the tube head from side to side to direct the central
rays of the x-ray beam perpendicular to the image receptor
through the mean tangent of the embrasures between the
teeth of interest. Determine the vertical angulation by moving the tube head up and down in the yoke to direct the central rays of the x-ray beam perpendicular to the image
receptor.
5. List what teeth you used to determine where to horizontally direct the central rays of the x-ray beam for each of
the standard image receptor placements. Why did you
choose these teeth?
6. What error is most likely to occur if the horizontal
angulation is not correctly aligned between the embrasures of the teeth of interest?
7. Observe the degrees of vertical angulation noted on
the yoke of the x-ray tube head for each of the standard image receptor placements. Determine if using
positive or negative angulation. Write down each of
the settings.
8. Compare the vertical angulation settings you used for
each of the standard image receptor placements with
those noted in Table 15-2 Summary of Steps for Acquiring Periapical Radiographs–Bisecting Technique. Explain
the difference between the vertical angulations you used
for the paralleling technique with the vertical angulations
recommended in Table 15-2 for use with the bisecting
technique. What general statement can you make about
the differences? Why?
REFERENCES
Eastman Kodak Company. (2002). Successful intraoral radiography. Rochester, NY: Author.
Rinn Corporation. (1983). Intraoral radiography with Rinn
XCP/BAI instruments. Elgin, IL: Dentsply/Rinn Corporation.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles
and interpretation (6th ed.). St. Louis: Elsevier.
18. Which of the following is the best sequencing for
exposing a full mouth series of periapical radiographs?
a. Mandibular anteriors, maxillary anteriors, mandibular
posteriors, maxillary posteriors
b. Maxillary anteriors, mandibular anteriors, maxillary
posteriors, mandibular posteriors
c. Mandibular posteriors, maxillary posteriors, mandibular anteriors, maxillary anteriors
d. Maxillary posteriors, mandibular posteriors, maxillary anteriors, mandibular anteriors
REFLECT—Case study
The dentist has prescribed a full mouth series of periapical and
bitewing radiographs for a patient who represents with several
areas of decay and a suspected abscess. This oral health care
practice uses an 18-image full mouth series configuration. Consider the following and write out your answers:
1. Prepare a list of the specific periapical and bitewing
radiographs you intend to expose. Include what size
image receptor you will use and why, and which specific teeth must be imaged on each of the projections.
2. Which radiographic technique for exposing periapical
radiographs will you choose for this exam? Why?
3. How will your patient be seated for the exposures? Why?
4. Will you be using the patient’s finger or a holder to
position the image receptor within the oral cavity?
Explain your choice.
5. Describe how the image receptor will be positioned in
relation to the teeth and how you will be directing the
central ray of the x-ray beam for the specific technique
you plan to use.
6. Summarize the steps you would take to locate the vertical and horizontal angulations.
7. Prepare a sequence of exposures and explain your choice.
RELATE—Laboratory application
Set up a teaching manikin or skull in the radiography operatory.
Position the occlusal plane parallel to the floor and the mid-sagittal plane perpendicular to the floor. Obtain an image receptor and
holder. Using Table 13-1 Standard Image Receptor Placements
for Periapical Radiographs of a Full Mouth Series practice the
standard image receptor placements for the periapical radiographs
listed. Write out your answers to the following questions.
1. What size image receptors did you chose for each of the
radiographs? List the considerations that prompted your
decision.
The Periapical
Examination—Paralleling
Technique
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Discuss the principles of the paralleling technique.
3. List the advantages and disadvantages of the paralleling technique.
4. Identify and be able to assemble and position image receptor holders for use with the
paralleling techniques.
5. Explain the importance of achieving accurate horizontal and vertical angulation in obtaining
quality diagnostic radiographs using the paralleling technique.
6. Identify vertical angulation errors made when using the paralleling technique.
7. Demonstrate the image receptor positioning for maxillary and mandibular periapical
exposures using the paralleling technique.
KEY WORDS
Biteblock
Embrasure
External aiming device
Film holder
Image receptor holder or positioner
Indicator ring
CHAPTER
OUTLINE
 Objectives 161
 Key Words 161
 Introduction 162
 Fundamentals
of Paralleling
Technique 162
 Holding the
Periapical Image
Receptor in
Position 163
 Horizontal and
Vertical Angulation Procedures 166
 Points of Entry 166
 The Periapical
Examination:
Paralleling
Technique 166
 Review, Recall,
Reflect, Relate 177
 References 178
CHAPTER
14
162 INTRAORAL TECHNIQUES
Introduction
Because of its ability to produce superior diagnostic quality
radiographs, the paralleling technique should be the technique of choice when exposing periapical radiographs
(Table 14-1). The purpose of this chapter is to present stepby-step procedures for exposing a full mouth series of periapical radiographs using the paralleling technique.
Fundamentals of Paralleling Technique
The basic principles of the paralleling technique meet the following two shadow casting principles:
• The image receptor (film packet, phosphor plate, or digital
sensor) is placed parallel to the long axis of the object
(tooth) being radiographed.
• The central ray of the x-ray beam is directed to intersect
both the image receptor and the object (tooth) perpendicularly (Figure 14-1).
Oral structures, particularly the curvature of the palate and
the outwardly inclined anterior teeth, make it difficult to place
the image receptor parallel to the long axes of the teeth
(Figure 14-2). The paralleling technique must achieve parallelism by placing the image receptor away from the crowns of
the teeth. Parallelism is accomplished by using an image receptor positioner or film holder specifically designed to allow the
patient to stabilize the image receptor in this position away from
the crowns of the teeth. This position, however, does not meet
the shadow cast principle that states that the image receptor
(film, phosphor plate, or digital sensor) and the object (tooth)
should be as close to each other as possible. To compensate for
the increased object–image receptor distance needed to achieve
parallelism, the target–image receptor distance should also be
increased. The PID length contributes to the target–image receptor distance and satisfies the shadow cast principle that states that
the object (tooth) should be as far as practical from the target
Direction of
central beam
of x-rays
Image receptor
FIGURE 14-1 Paralleling technique. The x-ray beam is directed
perpendicular to the recording plane of the image receptor, which has
been positioned parallel to the long axis of the tooth.
Visible Axis Actual Axis
FIGURE 14-2 Visible and actual long axis of the tooth. The
root portion of the tooth should be taken into consideration to
accurately locate the long axis of the tooth.
TABLE 14-1 Advantages and Disadvantages of the Paralleling Technique
ADVANTAGES DISADVANTAGES
• Produces images with minimal dimensional distortion.
• Minimizes superimposition of adjacent structures.
• Long axis of the tooth and recording plane of the image receptor
can be visually located making it easier to direct the x-rays
appropriately.
• Many choices of image receptor holders on the market with
external aiming devices specifically designed to make paralleling simple and easy to learn.
• With appropriate image receptor holding devices, takes less time
than trying to locate the position of an imaginary bisector.
• When using a long PID (16 in./41 cm), patient radiation dose
may be reduced.
• Parallel placement of the image receptor may be difficult to
achieve on certain patients: children, adults with small mouths, low
palatal vaults, or the presence of tori, patients with sensitive oral
mucosa or an exaggerated gag reflex, edentulous regions.
• These same conditions may increase patient discomfort when the
image receptor impinges on oral tissues.
• A short PID (8 in./20.5 cm) should not be used. The longer PID
required may be more difficult to maneuver and stabilize for exposures.
CHAPTER 14 • THE PERIAPICAL EXAMINATION—PARALLELING TECHNIQUE 163
(source of radiation). Ideally, the target–image receptor distance
used with the paralleling technique is 16 in. (41 cm) or at least
12 in. (30 cm; Figure 14-3).
Holding the Periapical Image Receptor in
Position
Image receptor holders designed for use with the paralleling
technique usually have a long biteblock area for the purpose of
achieving a parallel relationship between the recording plane of
the image receptor and the long axes of the teeth and an Lshaped backing to help support the image receptor and keep it
in position (Figure 14-4). Examples of paralleling positioners
and holders are the XCP (which stands for Extension Cone
Paralleling) for use with radiographic film (Figure 14-5) and
the XCP-DS for use with digital sensors manufactured by
Dentsply Rinn (www.rinncorp.com) and the RAPD® (which
stands for Right Angle Positioning Device) manufactured by
Flow Dental (www.flowdental.com; Figure 14-6). These instruments have an external aiming device to assist the radiographer in locating the correct angles and points of entry, making
errors less likely. The external aiming device also eliminates
the need to position the patient’s head precisely.
It should be noted, however, that the extra size and weight
of the external aiming device may make placement difficult or
uncomfortable for some patients. If placement of the image
Image receptor Using 8 inch (20.5 cm)
target-image receptor
distance
Using 16 inch (41 cm)
target-image receptor
distance
Image receptor
FIGURE 14-3 Comparison of the bisecting and paralleling methods.
With the bisecting technique, the image receptor is positioned adjacent to the
tooth, making a target–image receptor distance of 8 in. (20.5 cm) acceptable.
With the paralleling technique the image receptor is positioned near the center of
the oral cavity, where it must be retained in a position parallel to the long axes of
the teeth. This increased object–image receptor distance requires a longer
(12 in./30 cm or 16 in./41 cm) target–image receptor distance to produce a quality
radiograph.
FIGURE 14-4 Paralleling image receptor holder. Anterior
biteblock . The biting plane is at a right angle (900
) with the
backing plate. The patient bites down far enough out on the
bite extension to keep the image receptor and teeth parallel.
(Courtesy of Dentsply Rinn.)
164 INTRAORAL TECHNIQUES
Aiming device (ring)
Indicator rod (arm)
Posterior
instrument
Posterior
instrument
Anterior
instrument
Bitewing
(interproximal)
instrument
Biteblock
FIGURE 14-5 Rinn XCP. Note the external aiming device to assist with
locating the correct angles and points of entry. The external aiming device eliminates
the need to position the patient’s head precisely. (Courtesy of Dentsply Rinn.)
FIGURE 14-6 Flow Dental’s RAPD®. (Courtesy of Flow Dental.)
FIGURE 14-7 Dentsply Rinn’s Uni-GripAR®. Note the
wireless digital sensor image receptor. (Courtesy of Dentsply Rinn.)
receptor is compromised and therefore not positioned correctly,
the aiming device will indicate directing the x-ray beam to the
wrong place. Manufacturers have responded to the need to help
reduce the size and weight of an external aiming device with
products such as Dentsply Rinn’s Uni-GripAR® (Figure 14-7)
and Flip Ray (Figure 14-8). These holders with positioning
arms and aiming rings are made of lightweight plastic for the
purpose of improving patient comfort.
There are several image receptor positioners on the market
that with slight modifications may be used with both the paralleling and the bisecting techniques. Examples include the
Stabe® (Dentsply Rinn www.rinncorp.com) and the SUPA®
(which stands for Single Use Positioning Aid), manufactured by
Flow Dental (www.flowdental.com; Figure 14-9). These holders
provide a long biteblock and L-shaped back support for use with
the paralleling technique. However, the manufacturers have
designed the holder with a scored groove that allows the radiographer to break off the bite extension and use the holder with the
bisecting technique as well (see Figure 13-12). The light, polystyrene single-part construction makes these holders comfortable
and easy to place for most patients. However, because these
positioners lack an external aiming ring, the radiographer must
be skilled in estimating the correct angles and points of entry to
utilize these devices. For this reason, it is important that the radiographer develop the skills necessary to evaluate image receptor
placement for correctness, regardless of the holder used.
For illustration purposes, the Rinn XCP film holder with
film packet is described and demonstrated here because its
external aiming device attachment aids in directing the central
ray at the teeth and image receptor perpendicularly. The Rinn
XCP-ORA (Figure 14-10 and see Figure 13-11) may be used
in the same manner while eliminating the need for multiple
extension arms and rings. This holder allows the operator to
insert the metal arm into color-coordinated openings in the aiming ring that match the biteblocks to accommodate placements for
exposure of periapical and bitewing radiographs in all regions of
PRACTICE POINT
When using a sterile cotton roll to aid in stabilizing the image
receptor, be sure that the cotton roll is placed on the opposite
side from the teeth of interest. If the purpose of the radiograph is to image a maxillary tooth, the cotton roll should
be placed under the biteblock so that the mandibular teeth
contact the cotton roll when the patient occludes. If the purpose of the radiograph is to image a mandibular tooth, the
cotton roll should be placed on top of the biteblock so that
the maxillary teeth contact the cotton roll when the patient
occludes. Placing the cotton roll on the biteblock on the same
side as the teeth being imaged will prevent the patient from
occluding all the way onto the biteblock and will result in cutting off the apices of the teeth on the image.
CHAPTER 14 • THE PERIAPICAL EXAMINATION—PARALLELING TECHNIQUE 165
FIGURE 14-8 Dentsply Rinn’s Flip Ray. Note the film packet
image receptor. (Courtesy of Dentsply Rinn.)
FIGURE 14-9 Flow Dental’s SUPA®. Note the film packet image
receptor. (Courtesy of Flow Dental.)
FIGURE 14-10 Dentsply Rinn’s XCP-ORA®. (Courtesy of
Dentsply Rinn.)
the oral cavity. Although the radiographer should refer to the manufacturer’s instructions for use, important key points regarding
image receptor holders with external aiming devices are:
• The patient must bite down on the biteblock as far away from
the teeth as possible, utilizing the full extent of the biteblock.
The exception to this rule is for the mandibular premolar and
molar regions, where the image receptor can be close to the
teeth and still remain parallel because of the nearly vertical
position of the mandibular premolars and the slightly inward
inclination of the mandibular molars (Figure 14-11).
• The patient must bite down on the biteblock firmly enough
to hold the image recptor in place. A sterilized cotton roll
may be placed on the opposite side of the biteblock to provide stabilization and add to patient comfort.
• The external indicator ring attachment must be slid all the
way down the metal arm of the device to be as close to the
Midsagittal plane
Molars Premolars
FIGURE 14-11 Long axes of the premolar and molar teeth.
patient’s skin as possible without touching the patient prior
to the exposure.
• The open end of the PID is aligned to the indicator ring to
achieve correct horizontal and vertical angulations and
correct point of entry.
166 INTRAORAL TECHNIQUES
Horizontal and Vertical Angulation
Procedures
Horizontal Angulation
To rely on the image receptor holder’s external aiming ring to
accurately direct the central rays of the x-ray beam perpendicularly (at a right angle) toward the surface of the image receptor
in a horizontal plane, the image receptor itself must be positioned parallel to the teeth of interest in the horizontal dimension. The image receptor must be positioned parallel to the
interproximal space or embrasure of two predetermined teeth.
The teeth selected depend on the region being radiographed.
Table 14-2 lists the embrasure through which to align the image
receptor and to direct the central ray for each projection. The
central ray must be directed appropriately to avoid overlapping
adjacent teeth on the resultant image.
Image receptor
PID
Root
apex
not
recorded
A
B
Image receptor
PID
Incisal edge
not recorded
FIGURE 14-12 Vertical angulation error–paralleling
technique. (A) Excessive vertical angulation results in incisal/occlusal
edges being cut off the image. (B) Inadequate vertical angulation
results in the apices being cut off the image.
Vertical Angulation
When utilizing the paralleling technique, the correct vertical
angulation is achieved by directing the central rays of the x-ray
beam perpendicular to the image receptor and perpendicular to
the long axes of the teeth in the vertical plane. An image receptor
holding device designed for use with the paralleling technique is
used to position the image receptor parallel to the long axes of
teeth so that directing the central rays perpendicular to the teeth
will simultaneously direct the central rays perpendicular to the
image receptor. To rely on a holder’s external aiming ring to
accurately direct the central ray perpendicularly (at a right angle)
toward the surface of the image receptor in a vertical plane, the
image receptor itself must be positioned parallel to the teeth of
interest in the vertical dimension. Incorrect vertical angulation
when utilizing the paralleling technique results in cutting off a
portion of the area of interest from the image. When the vertical
angulation is excessive (greater than perpendicular to the recording plane of the image receptor), the incisal or occlusal edges of
the teeth will most likely be cut off, and when the vertical angulation is inadequate (less than perpendicular to the recording
plane of the image receptor), the root apices of the teeth will
most likely be cut off (Figure 14-12).
Points of Entry
Point of Entry
The point of entry for directing the central ray at the image
receptor when utilizing the paralleling technique for periapical
radiographs may be located using the external aiming device of
the image receptor positioner. Without an external indicator,
care should be taken to center the image receptor within the
beam of x-radiation. Use the portion of the holder, or biteblock,
that extends from the oral cavity to estimate the center of the
image receptor. Incorrect point of entry, or not centering the
image receptor within the x-ray beam, will result in conecut
error. (see Figure 18-7 and Figure 18-8)
The Periapical Examination: Paralleling
Technique
Figures 14-13 through 14-20 illustrate the precise positions and
the required angulations for each of the periapical radiographs
in a basic 14-image full-mouth series utilizing the paralleling
technique. See Table 14-2 for a summary of the four basic steps
of the technique—placement, vertical angulation, horizontal
angulation, and point of entry.
PRACTICE POINT
If the image receptor is correctly positioned parallel to the
teeth of interest and the central ray is accurately directed
through the appropriate embrasure and overlapping of other
adjacent teeth on the image occurs, it is usually attributed to
crowded or malaligned teeth. Crowded or malaligned teeth
will most likely require additional exposures to achieve a clear
view of all proximal surfaces (see Chapter 28).
167
TABLE 14-2 Summary of Steps for Acquiring Periapical Radiographs—Paralleling Technique
PERIAPICAL RADIOGRAPH PLACEMENT VERTICAL ANGULATION* HORIZONTAL ANGULATION POINT OF ENTRY
Maxillary incisors (image receptor size #1 or size #2)
(Figure 14-13)
Center the image receptor to line
up behind the central and lateral
incisors; if using a size #2
image receptor, include the
mesial halves of the canines.
Align the image receptor parallel
to the long axes of the incisors
and parallel to the left and right
central incisor embrasure.
Direct the central ray perpendicular to the plane of the image
receptor and long axes of the
incisors.
PID will be pointing down.
Direct the central ray perpendicular to the image receptor
through the left and right central
incisor embrasure.
Center the image receptor within
the x-ray beam by directing the
central rays at the center of the
image receptor.
Maxillary canine (image receptor
#1 or size #2) (Figure 14-14)
Center the image receptor to line
up behind the canine; include
the distal half of the lateral
incisor and the mesial half of the
first premolar.
Align the image receptor parallel
to the long axes of the canines
and parallel to the mesial and
distal line angles of the canine.
Direct the central ray perpendicular to the plane of the image
receptor and long axis of the
canine.
PID will be pointing down.
Direct the central ray perpendicular to the image receptor at the
center of the canine.
Center the image receptor within
the x-ray beam by directing the
central rays at the center of the
image receptor.
Maxillary premolar (image receptor size #2) (Figure 14-15) Align the anterior edge of the image receptor to line up behind
the distal half of the canine;
include the first and second premolars and mesial half of the
first molar.
Align the image receptor parallel
to the long axes of the premolars and parallel to the first and
second premolar embrasure.
Direct the central ray perpendicular to the plane of the image
receptor and long axes of the
premolars.
PID will be pointing down.
Direct the central ray perpendicular to the image receptor
through the first and second
premolar embrasure.
Center the image receptor within
the x-ray beam by directing the
central rays at the center of the
image receptor.
Maxillary molar (image receptor
size #2) (Figure 14-16)
Align the anterior edge of the
image receptor to line up behind
the distal half of the second premolar; include the first, second,
and third molars.
Align the image receptor parallel to
the long axes of the molars and
parallel to the first and second
molar embrasure.
Direct the central ray perpendicular
to the plane of the image receptor
and long axes of the molars.
PID will be pointing down.
Direct the central ray perpendicular
to the image receptor through the
first and second molar
embrasure.
Center the image receptor within the
x-ray beam by directing the central
rays at the center of the image
receptor.
(Continued )
168TABLE 14-2 (Continued)
PERIAPICAL RADIOGRAPH PLACEMENT VERTICAL ANGULATION* HORIZONTAL ANGULATION POINT OF ENTRY
Mandibular incisors (image
receptor size #1 or #2)
(Figure 14-17)
Center the image receptor to line
up behind the central and lateral
incisors if using a size #2 image
receptor; include the mesial
halves of the canines.
Align the image receptor parallel
to the long axes of the incisors
and parallel to the left and right
central incisor embrasure.
Direct the central ray perpendicular to the plane of the image
receptor and long axes of the
incisors.
PID will be pointing up.
Direct the central ray perpendicular to the image receptor
through the left and right central
incisor embrasure.
Center the image receptor within
the x-ray beam by directing the
central rays at the center of the
image receptor.
Mandibular canine (image receptor size #1 or #2) (Figure 14-18) Center the image receptor to line up behind the canine; include
the distal half of the lateral
incisor and the mesial half of the
first premolar.
Align the image receptor parallel
to the long axes of the canines
and parallel to the mesial and
distal line angles of the canine.
Direct the central ray perpendicular to the plane of the image
receptor and long axis of the
canine.
PID will be pointing up.
Direct the central ray perpendicular to the image receptor at the
center of the canine.
Center the image receptor within
the x-ray beam by directing the
central rays at the center of the
image receptor.
Mandibular premolar (image
receptor size #2) (Figure 14-19)
Align the anterior edge of the image
receptor to line up behind the distal half of the canine; include the
first and second premolars and
mesial half of the first molar.
Align the image receptor parallel to
the long axes of the premolars
and parallel to the first and second premolar embrasure.
Direct the central ray perpendicular
to the plane of the image receptor
and long axes of the premolars.
PID will be pointing up.
Direct the central ray perpendicular
to the image receptor through the
first and second premolar embrasure.
Center the image receptor within
the x-ray beam by directing the
central rays at the center of the
image receptor.
Mandibular molar (image receptor size #2) (Figure 14-20) Align the anterior edge of the image receptor to line up behind
the distal half of the second premolar; include the first, second,
and third molars.
Align the image receptor parallel to
the long axes of the molars and
parallel to the first and second
molar embrasure.
Direct the central ray perpendicular
to the plane of the image receptor
and long axes of the molars.
PID will be pointing up.
Direct the central ray perpendicular
to the image receptor through the
first and second molar
embrasure.
Center the image receptor within
the x-ray beam by directing the
central ray at the center of the
image receptor.
*The patient must be seated in the correct position, with the occlusal plane of the arch being imaged parallel to the floor and the midsaggital plane perpendicular to the floor.
CHAPTER 14 • THE PERIAPICAL EXAMINATION—PARALLELING TECHNIQUE 169
B C
PARALLELING TECHNIQUE
Maxillary Incisors Exposure
A
FIGURE 14-13 Maxillary incisors exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in
all anterior regions, the image receptor is positioned with the long dimension vertically. Image receptor is parallel to the teeth with the biteblock
inserted to its full length to position the image receptor back toward the region of the first molars to achieve parallelism with the long axes of the
incisors. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement.
(B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Maxillary incisors radiograph.
170 INTRAORAL TECHNIQUES
FIGURE 14-14 Maxillary canine exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in all
anterior regions, the image receptor is positioned with the long dimension vertically. Image receptor is parallel to the teeth with the biteblock
inserted to its full length to position the image receptor up into the midline of the palate to take advantage of the highest point and achieve
parallelism with the long axis of the canine. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to
help stabilize the placement (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Maxillary canine
radiograph.
B C
A
PARALLELING TECHNIQUE
Maxillary Canine Exposure
CHAPTER 14 • THE PERIAPICAL EXAMINATION—PARALLELING TECHNIQUE 171
B
A
C
PARALLELING TECHNIQUE
Maxillary Premolar Exposure
FIGURE 14-15 Maxillary premolar exposure. (A) Diagrams show the relationship of image receptor and holder, teeth, and PID. As in all
posterior regions, the image receptor is positioned with the long dimension horizontally. Image receptor is parallel to the teeth with the biteblock
inserted to its full length to position the image receptor up into the midline of the palate to take advantage of the highest point and achieve
parallelism with the long axes of the premolars. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor
to help stabilize the placement. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Maxillary premolar
radiograph.
172 INTRAORAL TECHNIQUES
B
C
A
PARALLELING TECHNIQUE
Maxillary Molar Exposure
FIGURE 14-16 Maxillary molar exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in all
posterior regions, the image receptor is positioned with the long dimension horizontally. Image receptor is parallel to the teeth with the biteblock
inserted to its full length to position the image receptor up into the midline of the palate to take advantage of the highest point and achieve
parallelism with the long axes of the molars. A sterile cotton roll may be placed on the biteblock on the opposite side from the image receptor to
help stabilize the placement. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID. (C) Maxillary molar
radiograph.
CHAPTER 14 • THE PERIAPICAL EXAMINATION—PARALLELING TECHNIQUE 173
A
B C
PARALLELING TECHNIQUE
Mandibular Incisors Exposure
FIGURE 14-17 Mandibular incisors exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth and PID. As in
all anterior regions, the image receptor is positioned with the long dimension vertically. Image receptor is parallel to the teeth. A sterile cotton
roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. This will aid in forcing the
biteblock down into position when the opposing teeth occlude. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular
PID. (C) Mandibular incisors radiograph.
174 INTRAORAL TECHNIQUES
B C
A
PARALLELING TECHNIQUE
Mandibular Canine Exposure
FIGURE 14-18 Mandibular canine exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in
all anterior regions, the image receptor is positioned with the long dimension vertically. Image receptor is parallel to the teeth. A sterile cotton
roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. This will aid in forcing the
biteblock down into position when the opposing teeth occlude. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular
PID. (C) Mandibular canine radiograph.
CHAPTER 14 • THE PERIAPICAL EXAMINATION—PARALLELING TECHNIQUE 175
B
C
A
PARALLELING TECHNIQUE
Mandibular Premolar Exposure
FIGURE 14-19 Mandibular premolar exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in all
posterior regions, the image receptor is positioned with the long dimension horizontally. Image receptor is parallel to the teeth. A sterile cotton roll
may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. This will aid in forcing the biteblock
down into position when the opposing teeth occlude. (B) Patient showing position of image receptor holder and 12 in. (30 cm) circular PID.
(C) Mandibular premolar radiograph.
176 INTRAORAL TECHNIQUES
C
B
A
PARALLELING TECHNIQUE
Mandibular Molar Exposure
FIGURE 14-20 Mandibular molar exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID. As in
all posterior regions, the image receptor is positioned with the long dimension horizontally. Image receptor is parallel to the teeth. A sterile
cotton roll may be placed on the biteblock on the opposite side from the image receptor to help stabilize the placement. This will aid in forcing
the biteblock down into position when the opposing teeth occlude. (B) Patient showing position of image receptor holder and 12 in. (30 cm)
circular PID. (C) Mandibular molar radiograph.
CHAPTER 14 • THE PERIAPICAL EXAMINATION—PARALLELING TECHNIQUE 177
2. To compensate for the increased object–image receptor
distance needed to achieve parallelism, the target–image
receptor distance should be
a. increased.
b. decreased.
3. Which of the following is NOT an advantage of the paralleling technique?
a. Produces images with minimal dimensional distortion
b. Minimizes superimposition of adjacent structures
c. Satisfies more shadow casting principles
d. Easy technique for children
4. The most important reason for using a holder when utilizing the paralleling technique is to stabilize the image
receptor in a position
a. at a right angle to the teeth.
b. perpendicular to the teeth.
c. parallel to the teeth.
d. parallel to the bisector.
5. Film holders designed for use with the paralleling technique should have a
a. short biteblock and L-shaped backing.
b. long biteblock and L-shaped backing.
c. short biteblock and no backing.
d. long biteblock and no backing.
6. Which of the following is an example of a holder that
can be used with both the paralleling and the bisecting
techniques?
a. SUPA®
b. Uni-GripAR®
c. XCP
d. Flip Ray
7. Each of the following is a part of the assembled XCP®
holder EXCEPT one. Which one is the EXCEPTION?
a. Metal arm
b. Indicator ring
c. Long biteblock
d. 105-degree angled backing
8. Lining the image receptor up behind the distal half of
the canine to include the first and second premolars and
mesial half of the first molar describes the placement
for which of the following periapical radiographs?
a. Central incisors
b. Canine
c. Premolar
d. Molar
9. To determine the horizontal angulation for the maxillary molar periapical radiograph, the central rays of the
x-ray beam should be directed at the image receptor
perpendicularly through the embrasures of the
a. first and second molars.
b. second premolar and first molar.
c. first and second premolars.
d. canine and first premolar.
REVIEW—Chapter summary
The paralleling technique is the technique of choice when
exposing periapical radiographs because of its ability to produce superior diagnostic-quality radiographs. The paralleling
technique satisfies two key shadow casting principles—the
image receptor is placed parallel to the long axes of the teeth,
and the central ray of the x-ray beam is directed perpendicular
to both the recording plane of the image receptor and the long
axes of the teeth. A long PID (16 in/41 cm or 12 in/30 cm)
compensates for the increased distance between the image
receptor and the teeth required to achieve parallelism. A disadvantage of the paralleling technique is that a parallel
object–image receptor relationship may be difficult to achieve
on some patients.
Because the image receptor must be positioned farther from
the teeth to achieve parallelism, a holding device with a long
biteblock and L-shaped backing is required. Image receptor
holders are designed for use with the paralleling or the bisecting
technique or may be modified to use with both techniques. A
holder with an external aiming device will assist in determining
the correct horizontal and vertical angulations and with determining the precise point of entry. To rely on the holder’s external
aiming ring, the image receptor must be positioned parallel to the
long axes of the teeth (in the vertical dimension) and parallel to
the embrasure of two predetermined teeth (in the horizontal
dimension).
If a holder without an external aiming device is used, the
horizontal angulation is determined by directing the central ray
of the x-beam perpendicular to the recording plane of the image
receptor through the mean tangent of the embrasures between
the teeth of interest, and the vertical angulation is determined
by directing the central ray of the x-beam perpendicular to the
long axes of the teeth and perpendicular to the recording plane
of the image receptor. The point of entry is determined by
using that portion of the biteblock that extends beyond the oral
cavity to direct the central ray of the x-ray beam to the center
of the image receptor.
The four basic steps to exposing a periapical radiograph
are placement, vertical angulation, horizontal angulation, and
point of entry. Step-by-step illustrated instructions for exposing
a full mouth series of periapical radiographs utilizing the paralleling techniques are presented.
RECALL—Study questions
1. What shadow casting principle is NOT likely to be met
when utilizing the paralleling technique?
a. Radiation should strike the object (tooth) and image
receptor perpendicularly.
b. Object (tooth) should be as far as practical from the
target (source of radiation).
c. Object (tooth) and image receptor should be parallel
to each other.
d. Object (tooth) and image receptor should be as close
as possible to each other.
178 INTRAORAL TECHNIQUES
receptor holders designed for use with the paralleling technique,
answer the following questions:
1. Which technique is the new holder designed to be used
with? How can you tell?
2. How is the new holder similar to the one you have been
using? Different?
3. Which holder would it be best to know how to use?
Why?
4. What are the advantages/disadvantages of the new
holder?
5. What are the advantages/disadvantages of the holder
you have been using?
6. What is your recommendation for the practice? Should
they continue to use this holder, or should they purchase
the holder you are familiar with? Explain your answers.
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson Education. Chapter 4, “Periapical radiographs—paralleling technique.”
REFERENCES
Eastman Kodak Company. (2002). Successful intraoral radiography. Rochester, NY: Author.
Rinn Corporation. (1983). Intraoral radiography with Rinn
XCP/BAI instruments. Elgin, IL: Dentsply/Rinn Corporation.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles
and interpretation (6th ed.). St. Louis, MO: Elsevier.
10. To determine the horizontal angulation for the
mandibular premolar periapical radiograph, the central rays of the x-ray beam should be directed at the
image receptor perpendicularly through the embrasures of the
a. first and second molars.
b. second premolar and first molar.
c. first and second premolars.
d. canine and first premolar.
11. Directing the central rays perpendicular to the plane of
the image receptor and perpendicular to the long axes
of the teeth describes which step of the paralleling
technique?
a. Placement
b. Vertical angulation
c. Horizontal angulation
d. Point of entry
12. Cutting off the root apex portion of the image on a periapical radiograph results from
a. excessive horizontal angulation.
b. inadequate horizontal angulation.
c. excessive vertical angulation.
d. inadequate vertical angulation.
REFLECT—Case study
You have recently accepted a position in a general practice dental
office. This week you discovered that the image receptor holding
device for exposing a full mouth survey is the one pictured in
Figure 14-9. You have always used the film-holding device pictured in Figures 14-13 through 14-20, and the new holder is unfamiliar to you. Based on what you have learned about image
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Discuss the principles of the bisecting technique.
3. List the advantages and disadvantages of the bisecting technique.
4. Identify and be able to assemble and position image receptor holders for use with the
bisecting technique and distinguish these holders from those used with the paralleling
technique.
5. Explain the importance of achieving accurate horizontal and vertical angulation in obtaining
quality diagnostic radiographs using the bisecting technique.
6. List the recommended predetermined vertical angulation settings used with the bisecting
technqiue.
7. Identify vertical angulation errors made when using the bisecting technique.
8. Locate facial landmarks used for determining the points of entry used with the bisecting
technqiue.
9. Demonstrate image receptor positioning for maxillary and mandibular periapical exposures
using the bisecting technique.
KEY WORDS
Ala
Bisector
Biteblock
Bite extension
Elongated image
Embrasure
Film holder
Foreshortened image
Horizontal angulation
Image receptor holder or positioner
Isometric triangle
Mean tangent
Symphysis
Vertical angulation
The Periapical
Examination—Bisecting
Technique
CHAPTER
OUTLINE
 Objectives 179
 Key Words 179
 Introduction 180
 Fundamentals
of Bisecting
Technique 180
 Holding the
Periapical Image
Receptor
in Position 181
 Horizontal
and Vertical
Angulation
Procedures 182
 Points of Entry 185
 The Periapical
Examination:
Bisecting
Technique 185
 Review, Recall,
Reflect, Relate 194
 References 195
CHAPTER
15
180 INTRAORAL TECHNIQUES
Introduction
Because it satisfies fewer shadow cast principles (see
Chapter 13), the bisecting technique is less likely to produce
superior diagnostic quality radiographs. However, some situations and conditions make the use of the paralleling technique
difficult. When irregularities or obstructions of the oral tissues
and the curvature of the palate prevent a parallel image receptor
to long axes of the teeth placement, an acceptable diagnosticquality radiograph may be obtained utilizing the bisecting technique (Table 15-1). The radiographer who possesses a working
knowledge of both the paralleling and the bisecting techniques
will be prepared to meet and overcome conditions that challenge
the ability to produce diagnostic radiographs. Although the
bisecting technique is not recommended because images produced contain inherent dimensional distortion, careful attention
to the steps of the technique can produce acceptable results
when needed. The purpose of this chapter is to present step-bystep procedures for exposing a full mouth series of periapical
radiographs using the bisecting technique.
Fundamentals of Bisecting Technique
The bisecting principle is applied when the image receptor is
not, or cannot, be placed parallel to the long axes of the teeth.
This is often the case with children, with adults who have a shallow palatal vault or a large torus present, or when edentulous
regions exist. If the image receptor is not positioned parallel to
the long axes of teeth, it will not be possible to direct the central
ray appropriately perpendicular to the long axes of the teeth
simultaneously with perpendicular to the plane of the image
receptor. To cast an accurate shadow representation of a tooth
onto the image receptor, the angle formed by the long axis of the
tooth and the plane of the image receptor must be bisected. One
must first find the long axis of the tooth and then find the long
axis of the image receptor as it is placed next to the tooth. After
visualizing these two planes, one must imagine a line, called
the bisector, which bisects the angle where the long axis of the
tooth and the long axis of the image receptor plane meet. The
central ray of the x-ray beam is directed perpendicular to this
imaginary bisector (Figure 15-1).
Theoretically, two isometric triangles (triangles having
equal measurements) are formed when the central ray is directed
perpendicular to the bisector, and the image that results should
be the same size as the tooth. In practice, this does not always
happen (Figure 15-2 and see Figure 4-13). The diagnostic quality
of the image is usually compromised, with some dimensional
distortion that is inherent in the bisecting technique.
TARGET–IMAGE RECEPTOR DISTANCE Because the long
axis of the tooth and the plane of the image receptor are not
parallel, a shorter target–image receptor distance will limit
magnification and distortion. The shorter 8-in. (20.5-cm) PID
facilitates a shorter target–image receptor distance and is
generally preferred for use with the bisecting technique.
Whereas the paralleling technique is better matched with a
longer target–image receptor distance, typically a 12-in. (30-cm)
or ideally a 16-in. (41-cm) PID to compensate for the greater
object–image receptor distance, the bisecting technique
should be matched with a shorter target—image receptor distance, typically an 8-in. (20.5-cm) PID, to compensate for
the lack of parallelism between the long axis of the tooth and
the plane of the image receptor.
90° 90°
Image receptor
Direction of
central beam
of x-rays
FIGURE 15-1 Rule of isometry applied to the bisecting
technique. Line XY passes through the long axis of the tooth while
the image receptor is positioned along line XZ. The central beam of
radiation is directed perpendicularly through the apical area of the
tooth toward the bisector XW. Because triangles WXY and WXZ are
equal, the shadow image cast on the image receptor will be
approximately equal to the length of the actual tooth, provided that
the bisector line is correctly estimated.
TABLE 15-1 Advantages and Disadvantages of the Bisecting Technique
ADVANTAGES DISADVANTAGES
• Image receptor placement may be easier with certain
patients: children, adults with small mouths, low
palatal vaults, or the presence of tori, patients with sensitive oral mucosa or an exaggerated gag reflex, edentulous regions.
• A short PID (8 in/20.5 cm) may be used.
(Some operators find a short PID easier to maneuver.)
• Produces images with dimensional distortion. (Some elongation or foreshortening will occur even when the technique is performed correctly.)
• Often superimposes adjacent structures. (The necessary vertical angle increase
often causes a shadow of the zygomatic process of the maxilla to be superimposed over the molar roots in the maxillary regions.)
• Estimating the location of the imaginary bisector may be difficult.
• When using a short PID (8 in/20.5 cm), patient radiation dose may be
increased.
CHAPTER 15 • THE PERIAPICAL EXAMINATION—BISECTING TECHNIQUE 181
PRACTICE POINT
To aid in estimating the imaginary bisector, utilize the two
visible planes: the teeth and the image receptor. Looking at
the teeth, locate the long axes. Then align the x-ray beam
to intersect the long axes of the teeth perpendicularly. Study
the PID and make a mental note of this angle. Next look at
the image receptor. Note the plane of the image receptor as
it is placed against the teeth. Then shift the PID so that the
x-ray beam is aligned to intersect the plane of the image
receptor perpendicularly. Note this angle while recalling the
angle at which the x-ray beam intersected the long axes of
the teeth. If you need to, repeat this process, shifting the
PID to allow the x-ray beam to intersect the long axes of the
teeth and then the image receptor plane perpendicularly
until you can estimate a position halfway in between these
two angles. This halfway point is the imaginary bisector.
Image
Direction of receptor
central beam
of x-rays
Three-dimentional
object
Angular image
results
FIGURE 15-2 Dimensional distortion is inherent to the
bisecting technique. When the image receptor is not positioned
parallel to the object, the part of the object farthest from the image
receptor is projected in an incorrect relationship to the parts closest
to the image receptor. This occurs when a three-dimensional object,
such as the tooth, is projected onto a two-dimensional surface,
creating an angular relationship between the object and the image
receptor.
OBJECT–IMAGE RECEPTOR DISTANCE It is important to
note that when the image receptor is placed close to the teeth
in both the anterior and the posterior regions of the maxilla and
in the anterior region of the mandible, the bisecting technique
must be utilized to compensate for the lack of parallelism
between the image receptor and the long axes of the teeth.
However, the mandibular posterior region, which includes the
molars and premolars, is the exception to this generalization.
If oral conditions present that allow for placement of the image
receptor close to the teeth in these regions a parallel relationship
may indeed result, and the paralleling technique may be used
successfully (see Figure 14-11).
Holding the Periapical Image Receptor
in Position
Image receptor holders or positioners designed for use with the
bisecting technique will most likely have a short biteblock. Typically, a shorter biteblock or a holder that lacks the L-shaped support backing is considered an image receptor positioner better
suited for use with the bisecting technique. The use of holders of
this type allows the image receptor to be placed close to the lingual surface of the teeth and therefore not parallel to the long
axes of the teeth. Examples of holders designed for use with the
bisecting technique are the Snap-A-Ray® (manufactured by
Dentsply Rinn www.rinncorp.com) and the Wing-A-Ray
(manufactured by steri-shield www.steri-shield.com) both for
use with radiographic film, phosphor plates, or digital sensors;
Figure 15-3 and Figure 15-4).
As noted in Chapter 13, paralleling image receptor positioners are available that can be slightly modified for use with
the bisecting technique. The bite extension of the Stabe®
(Dentsply Rinn www.rinncorp.com) and the SUPA® (which
stands for Single Use Positioning Aid) manufactured by Flow
Dental (www.flowdental.com) that is needed for use with the
FIGURE 15-3 Snap-A-Ray® image receptor holder. The short
biteblock and 105º; angled backing indicate that this holder be paired
with the bisecting technique. Note the film packet image receptor.
(Courtesy of Dentsply Rinn.)
FIGURE 15-4 Wing-A-Ray image receptor holder. The short
biteblock and lack of L-shaped backing indicate that this holder be
paired with the bisecting technique. Note the digital sensor image receptor.
182 INTRAORAL TECHNIQUES
paralleling technique may be broken off for use with the bisecting technique (see Figure 13-12 ). Dentsply Rinn offers a biteblock with a raised platform and a 105-degree backing plate
(Figure 15-5), called the BAI® (which stands for Bisecting
Angle Instrument), for use with the positioning arm and aiming
ring of the XCP® (which stands for Extension Cone Paralleling; see Figure 13-13). Replacing the 90-degree biteblock of
the XCP® with the 105-degree biteblock of the BAI® converts
this paralleling image receptor-holder into one that can be used
with the bisecting technique.
Because of the variety of film, phosphor plate, and digital
sensor holders available currently and that continue to come to
market, it is important that the radiographer possess a working
knowledge of the bisecting technique to better match the holder
with the technique for optimal results.
For illustration purposes, the Rinn Stabe® film holder
with film packet is described and demonstrated here. Its lightweight construction and small size allow for ease in placing
the image receptor when the patient presents with conditions
that make parallel image receptor placement difficult.
Although the radiographer should refer to the manufacturer’s
instructions for use, important key points regarding this type
of image receptor holder are:
• The patient should bite down on the biteblock as close
to the teeth as necessary. This will most likely not position the image receptor parallel to the long axes of the
teeth. The exception to this rule is for the mandibular
premolar and molar regions, where the image receptor
can be close to the teeth and still remain parallel
because of the nearly vertical position of the mandibular
premolars and the slightly inward inclination of the
mandibular molars (see Figures 14-2 and 14-11).
• The patient must bite down on the biteblock firmly enough
to hold the image receptor in place. A sterilized cotton roll
may be placed on the opposite side of the biteblock to provide stabilization and add to patient comfort.
• Using the long axes of the teeth and the plane of the image
receptor, the radiographer must determine the correct
vertical angle and direct the central ray perpendicular to
the imaginary bisector, adjusting the PID accordingly. If
the patient is seated correctly with the midsaggital plane
perpendicular to the floor and the occlusal plane parallel
to the floor, predetermined vertical anglation settings may
be used.
• Using the teeth contact points and the plane of the image
receptor, the radiographer must determine the correct horizontal angle and direct the central ray perpendicular
through the embrasures of the teeth of interest adjusting
the PID accordingly.
• The radiographer must determine the correct point of entry
and direct the central ray at the apices of the teeth of interest. If the patient is seated correctly with the midsaggital
plane perpendicular to the floor and the occlusal plane parallel to the floor, predetermined anatomical landmarks
may be used through which to direct the central ray of the
x-ray beam.
To limit magnification and distortion that results from
lack of parallelism between the long axes of the teeth and
the plane of the image receptor when using the bisecting
technique, the target–image receptor distance is decreased to
an 8-in. (30-cm) PID.
Horizontal and Vertical Angulation
Procedures
Horizontal Angulation
The steps for determining correct horizontal angulation are
the same for both the bisecting and paralleling techniques.
First, the image receptor must be positioned parallel to the
interproximal space, or embrasure, of two predetermined
teeth. Then the horizontal angulation is achieved by directing
the central ray of the x-ray beam perpendicular to the mean
tangent, or curvature of the arch, through the contact points of
these teeth (Table 15-2).
Vertical Angulation
With the bisecting technique the central ray of the x-ray beam
can not be directed perpendicular to both the long axes of
the teeth and the plane of the image receptor simultaneously.
When utilizing the bisecting technique, the correct vertical
angulation is achieved by directing the central ray of the
x-ray beam perpendicular to the imaginary bisector between
the long axes of the teeth and the plane of the image receptor.
If the patient is seated with the head positioning correct, the
occlusal plane parallel to the floor, and the midsaggital
plane perpendicular to the floor, predetermined vertical
settings may be utilized to position the PID at the correct
vertical angulation (Table 15-2). It is important to check
that the occlusal plane of the arch being imaged is parallel
to the floor. Incorrect vertical angulation when utilizing
the bisecting technique results in an image that appears
elongated or foreshortened. When the vertical angulation is
excessive (greater than perpendicular to the imaginary
bisector) a foreshortened image will result, and when the
vertical angulation is inadequate (less than perpendicular
to the imaginary bisector), the result is an elongated
image (Figure 15-6). Vertical angulation error is explained
in Chapter 18.
Image receptor
Backing plate Biting platform
FIGURE 15-5 Bisecting technique image receptor holder.
Anterior biteblock of BAI®. The backing plate is at a 105º angle with
the short biteblock allowing for close placement of the image
receptor to the teeth. (Courtesy of Dentsply Rinn.)
183
TABLE 15-2 Summary of Steps for Acquiring Periapical Radiographs—Bisecting Technique
PERIAPICAL
RADIOGRAPH PLACEMENT VERTICAL ANGULATION* HORIZONTAL ANGULATION POINT OF ENTRY*
Maxillary incisors
(image receptor
size #1 or size #2)
(Figure 15-8)
Center the image receptor to line up
behind the central and lateral incisors;
if using a size #2 image receptor,
include the mesial halves of the canines.
Place the image receptor as close as
possible to the lingual surfaces of
the incisors, parallel to the left and right
central incisor embrasure.
Direct the central ray toward the imaginary bisector between the long axes of
the incisors and the plane of the image
receptor in the vertical dimension at
+40°.
Direct the central ray perpendicular
to the image receptor through the left
and right central incisor
embrasure.
Center the image receptor
within the x-ray beam by
directing the central ray at a
point near the tip of the nose.
(Figure 14-7 maxillary
point #1)
Maxillary canine
(image receptor
size #1 or size
#2) (Figure 15-9)
Center the image receptor to line up
behind the canine; include the distal half
of the lateral incisor and the mesial half
of the first premolar.
Place the image receptor as close as
possible to the lingual surface of
the canine, parallel to the mesial
and distal line angles of the canine.
Direct the central ray toward the imaginary bisector between the long axis of
the canine and the plane of the image
receptor in the vertical dimension at
+45°.
Direct the central ray perpendicular
to the image receptor at the center of the
canine.
Center the image receptor
within the x-ray beam by
directing the central ray at
the root of the canine, at the ala
of the nose. (Figure 14-7
maxillary point #2)
Maxillary premolar
(image receptor
size #2)
(Figure 15-10)
Align the anterior edge of the image
receptor to line up behind the distal half
of the canine; include the first and
second premolars and mesial half of the
first molar.
Place the image receptor as close as
possible to the lingual surfaces of
the premolars, parallel to the first
and second premolar embrasure.
Direct the central ray toward the
imaginary bisector between
the long axes of the premolars and the
plane of the image receptor
in the vertical dimension at +30°.
Direct the central ray perpendicular
to the image receptor through the first
and second premolar
embrasure.
Center the image receptor
within the x-ray beam by
directing the central ray at a
point on the ala–tragus line
directly below the pupil of the
eye. (Figure 14-7 maxillary
point #3)
Maxillary molar
(image receptor
size #2)
(Figure 15-11)
Align the anterior edge of the image
receptor to line up behind the distal half
of the second premolar; include the first,
second, and third molars.
Place the image receptor as close as
possible to the lingual surfaces of
the molars, parallel to the first and
second molar embrasure.
Direct the central ray toward the
imaginary bisector between
the long axes of the molars and
the plane of the image receptor
in the vertical dimension at +20°.
Direct the central ray perpendicular
to the image receptor through the first
and second molar embrasure.
Center the image receptor
within the x-ray beam by
directing the center ray at a
point on the ala–tragus line
directly below the outer canthus
of the eye. (Figure 14-7
maxillary
point #4)
(Continued )
184TABLE 15-2 (Continued)
PERIAPICAL
RADIOGRAPH PLACEMENT VERTICAL ANGULATION* HORIZONTAL ANGULATION POINT OF ENTRY*
Mandibular incisors
(image receptor
size #1 or #2)
(Figure 15-12)
Center the image receptor to line up
behind the central and lateral incisors;
if using a size #2 image receptor,
include the mesial halves of the
canines.
Place the image receptor as close as
possible to the lingual surfaces of
the incisors, parallel to the left and
right central incisor embrasure.
Direct the central ray toward the
imaginary bisector between the long
axes of the incisors and the
plane of the image receptor in the
vertical dimension at -15°.
Direct the central ray perpendicular
to the image receptor through
the left and right central incisor
embrasure.
Center the image receptor within the
x-ray beam by directing
the central ray at a point in the
middle of the chin (symphysis),
1 in. (2.5 cm) above the lower
border of the mandible.
(Figure 14-7 mandibular
point #1)
Mandibular canine
(image receptor
size #1 or #2)
(Figure 15-13)
Center the image receptor to line up
behind the canine; include the distal
half of the lateral incisor and the
mesial half of the first premolar.
Place the image receptor as close as
possible to the lingual surfaces of
the canine, parallel to the mesial
and distal line angles of the canine.
Direct the central ray toward the
imaginary bisector between
the long axis of the canine and
the plane of the image receptor
in the vertical dimension at -20°.
Direct the central ray perpendicular
to the image receptor at the center
of the canine.
Center the image receptor
within the x-ray beam by directing the central ray at
the center of the root of the
canine, 1 in. (2.5 cm) above the
inferior border of the mandible.
(Figure 14-7 mandibular point
#2)
Mandibular premolar
(image receptor size
#2) (Figure 15-14)
Align the anterior edge of the image
receptor to line up behind the distal
half of the canine; include the first
and second premolars and mesial
half of the first molar.
Place the image receptor as close as
possible to the lingual surfaces of
the premolars, parallel to the first
and second premolar embrasure.
Direct the central ray toward the
imaginary bisector between
the long axes of the premolar and the
plane of the image receptor
in the vertical dimension at -10°.
Direct the central ray perpendicular
to the image receptor through
the first and second premolar
embrasure.
Center the image receptor
within the x-ray beam by directing the central ray at a point on
the chin, 1 in. (2.5 cm) above the
border of the mandible, directly
inferior to the pupil of the eye.
(Figure 14-7 mandibular
point #3)
Mandibular molar
(image receptor size
#2) (Figure 15-15)
Align the anterior edge of the image
receptor to line up behind the
distal half of the second premolar;
include the first, second, and third
molars.
Place the image receptor as close as
possible to the lingual surfaces of
the molars, parallel to the first and
second molar embrasure.
Direct the central ray toward the
imaginary bisector between
the long axes of the molars and
the plane of the image receptor
in the vertical dimension at -5°.
Direct the central ray perpendicular
to the image receptor through
the first and second molar
embrasure.
Center the image receptor
within the x-ray beam by directing the central ray at a point on
the center of the
chin 1 in. (2.5 cm) above the
lower border of the mandible,
directly below the outer canthus
of the eye. (Figure 14-7
mandibular point #4)
* The patient must be seated in the correct position, with the occlusal plane of the arch being imaged parallel to the floor and the midsaggital plane perpendicular to the floor.
CHAPTER 15 • THE PERIAPICAL EXAMINATION—BISECTING TECHNIQUE 185
Points of Entry
The image receptor must be centered within the beam of x-radiation to avoid conecut error. The central ray of the x-ray beam
should be directed through the apices of the teeth of interest.
When utilizing the bisecting technique, if the patient is seated
with the correct head position, the point of entry may be estimated with the use of recommended landmarks (Table 15-2;
Figure 15-7).
The Periapical Examination: Bisecting
Technique
Figures 15-8 through 15-15 illustrate the precise image receptor
positions and the required angulations for each of the periapical
radiographs in a basic 14-film full mouth series utilizing the
bisecting technique. See Table 15-2 for a summary of the four
basic steps of the technique—placement, vertical angulation,
horizontal angulation, and point of entry.
Outer
canthus Inner canthus
Ala of nose
Tip of nose
Commissure of lips
Symphysis of chin
Tragus
of ear
4 3 2 1
4 3 2 1
FIGURE 15-7 Points of entry. Facial landmarks can provide the
radiographer with a reference for positioning the PID and directing
the central ray of the x-ray beam. The patient must be seated upright
with the midsagittal plane perpendicular to the floor and the occlusal
plane parallel to the floor to use these landmarks accurately. Note the
numbers that indicate the points of entry for each of the projections
listed in Table 15-2.
A
Image receptor
Image receptor
PID
Foreshortened
image
PID
B
Elongated
image
FIGURE 15-6 Vertical angulation error—
bisecting technique. (A) Excessive vertical
angulation results in a foreshortened image.
(B) Inadequate vertical angulation results in an
elongated image.
186 INTRAORAL TECHNIQUES
C D
Central
ray
PID
Mean tangent
A
Occlusal plane
Image receptor
Image receptor
Bisector
Long axis
of tooth Central ray PID
+40°
B
BISECTING TECHNIQUE
Maxillary Incisors Exposure
FIGURE 15-8 Maxillary incisors exposure. (A) Diagram shows horizontal angulation is directed through the central incisors embrasure
and perpendicular to the mean tangent. (B) Vertical angulation is directed perpendicular to the bisector at approximately degrees with the
PID tilted downward. (C) Patient showing position of image receptor and holder, and 8-in. (20.5-cm) circular PID. (D) Maxillary incisors
radiograph.
+40
CHAPTER 15 • THE PERIAPICAL EXAMINATION—BISECTING TECHNIQUE 187
C D
Image receptor
Central
ray
PID
Mean
tangent
A
Central ray
Occlusal plane Image receptor
Bisector
Long axis
of tooth
PID
+45°
B
BISECTING TECHNIQUE
Maxillary Canine Exposure
FIGURE 15-9 Maxillary canine exposure. (A) Diagram shows horizontal angulation is directed at the midline of the canine and
perpendicular to the mean tangent. (B) Vertical angulation is directed perpendicular to the bisector at approximately degrees with the PID
tilted downward. (C) Patient showing position of image receptor and holder, and 8-in. (20.5-cm) circular PID. (D) Maxillary canine radiograph.
+45
188 INTRAORAL TECHNIQUES
Central ray
B
Occlusal plane
Image receptor
Bisector
Long axis
of tooth
PID
+30°
Central ray PID
Image receptor
Mean
tangent
A
C
D
BISECTING TECHNIQUE
Maxillary Premolar Exposure
FIGURE 15-10 Maxillary premolar exposure. (A) Diagram shows horizontal angulation is directed through the premolars embrasure and
perpendicular to the mean tangent. (B) Vertical angulation is directed perpendicular to the bisector at approximately degrees with the PID
tilted downward. (C) Patient showing position of image receptor and holder, and 8-in. (20.5-cm) circular PID. (D) Maxillary premolar radiograph.
+30
CHAPTER 15 • THE PERIAPICAL EXAMINATION—BISECTING TECHNIQUE 189
C
D
A
PID
Image
receptor
Mean
tangent
Central ray
B
Central ray
Occlusal plane
Image receptor
Bisector
Long axis
of tooth
PID
+20°
BISECTING TECHNIQUE
Maxillary Molar Exposure
FIGURE 15-11 Maxillary molar exposure. (A) Diagram shows horizontal angulation is directed through the first and second molar
embrasure and perpendicular to the mean tangent. (B) Vertical angulation is directed perpendicular to the bisector at approximately degrees
with the PID tilted downward. (C) Patient showing position of image receptor and holder, and 8-in. (20.5-cm) circular PID. (D) Maxillary molar
radiograph.
+20
C D
B
Central ray
Occlusal plane
Image receptor
Bisector
Long axis
of tooth
PID
−15°
Image
receptor
Central
ray
PID
Mean
tangent
A
BISECTING TECHNIQUE
Mandibular Incisors Exposure
190 INTRAORAL TECHNIQUES
FIGURE 15-12 Mandibular incisors exposure. (A) Diagram shows horizontal angulation is directed through the central incisors embrasure
and perpendicular to the mean tangent. (B) Vertical angulation is directed perpendicular to the bisector at approximately degrees with the
PID tilted upward. (C) Patient showing position of image receptor and holder, and 8-in. (20.5-cm) circular PID. (D) Mandibular incisors
radiograph.
-15
CHAPTER 15 • THE PERIAPICAL EXAMINATION—BISECTING TECHNIQUE 191
C D
Image receptor
Central
ray
PID
Mean
tangent
A B
Occlusal plane
Image receptor
Bisector
Long axis
of tooth PID
−20°
Central ray
BISECTING TECHNIQUE
Mandibular Canine Exposure
FIGURE 15-13 Mandibular canine exposure. (A) Diagram shows horizontal angulation is directed at the midline of the canine and
perpendicular to the mean tangent. (B) Vertical angulation is directed perpendicular to the bisector at approximately degrees with the PID
tilted upward. (C) Patient showing position of image receptor and holder, and 8-in. (20.5-cm) circular PID. (D) Mandibular canine radiograph.
-20
192 INTRAORAL TECHNIQUES
C
D
B
Occlusal plane
Image receptor
Bisector
Long axis
of tooth
PID
−10° Central ray
A
PID
Image
receptor
Mean tangent Central ray
BISECTING TECHNIQUE
Mandibular Premolar Exposure
FIGURE 15-14 Mandibular premolar exposure. (A) Diagram shows horizontal angulation is directed through the premolar embrasure
and perpendicular to the mean tangent. (B) Vertical angulation is directed perpendicular to the bisector at approximately degrees with the
PID tilted upward. (C) Patient showing position of image receptor and holder, and 8-in. (20.5-cm) circular PID. (D) Mandibular premolar
radiograph.
-10
CHAPTER 15 • THE PERIAPICAL EXAMINATION—BISECTING TECHNIQUE 193
B
Occlusal plane
Image receptor
Bisector
Long axis
of tooth
PID
−5° Central ray
PID
Image
receptor
Mean
tangent
A
Central ray
C
D
BISECTING TECHNIQUE
Mandibular Molar Exposure
FIGURE 15-15 Mandibular molar exposure. (A) Diagram shows horizontal angulation is directed through the first and second molar
embrasure and perpendicular to the mean tangent. (B) Vertical angulation is directed perpendicular to the bisector at approximately degrees
with slight upward tilt of the PID. (C) Patient showing position of image receptor and holder, and 8-in. (20.5-cm) circular PID. (D) Mandibular
molar radiograph.
-5
194 INTRAORAL TECHNIQUES
REVIEW—Chapter summary
Meeting fewer shadow casting principles than the paralleling
technique, the bisecting technique is less likely to produce
superior diagnostic quality radiographs. The bisecting technique is based on the theory that two isometric triangles are
formed when the central ray is directed perpendicular to the
bisector. If irregularities or obstructions of the oral tissues prevent a parallel image receptor placement, the radiographer who
is skilled in the bisecting technique can produce an acceptable
diagnostic-quality radiograph when needed.
When the image receptor is positioned close to the tooth,
parallelism is not likely. The exception to this occurs in the
mandibular posterior region, where the molars and premolars
are positioned near vertical in the arch. When parallelism cannot be established, to cast an accurate shadow representation
of a tooth onto the image receptor, the angle formed by the
long axis of the tooth and the plane of the image receptor must
be bisected. The central ray of the x-ray beam is directed perpendicular to this imaginary bisector. A short target—image
receptor distance (8-in/20.5-cm PID) will limit magnification
that is inherent when parallelism is not established.
Image receptor holders designed for use with the bisecting
technique generally have a short biteblock and lack the L-shaped
back support. Holders are available that with modification can be
used with either the bisecting or the paralleling technique.
The horizontal angulation is determined by directing the
central ray of the x-beam perpendicular to the recording plane of
the image receptor through the mean tangent of the embrasures
between the teeth of interest. Both paralleling and bisecting
techniques determine horizontal angulation in the same manner.
The vertical angulation is determined by directing the central ray of the x-beam perpendicular to the imaginary bisector.
If the patient’s head position is correct, predetermined vertical
angle settings may be used.
The image receptor must be centered within the beam of
radiation. If the patient’s head position is correct, predetermined landmarks may be used to estimate the point of entry.
The four basic steps to exposing a periapical radiograph
are placement, vertical angulation, horizontal angulation, and
point of entry. Step-by-step illustrated instructions for exposing a full mouth series of periapical radiographs utilizing the
bisecting technique are presented.
RECALL—Study questions
1. The bisecting technique satisfies more shadow casting
rules than the paralleling technique.
A better image results when the shadow casting rules
are followed.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is true.
c. Both statements are true.
d. Both statements are false.
2. What shadow casting principle is most likely to be met
when utilizing the bisecting technique?
a. Object (tooth) and image receptor should be parallel
to each other.
b. Object (tooth) and image receptor should be as close
as possible to each other.
c. Object (tooth) should be as far as practical from the
target (source of radiation).
d. Radiation should strike the object (tooth) and image
receptor perpendicularly.
3. What term describes the imaginary line between the long
axis of the tooth and the plane of the image receptor?
a. Tangent
b. Median
c. Midsagittal
d. Bisector
4. When utilizing the bisecting technique, the image
receptor is placed
a. parallel to the tooth.
b. as close as possible to the tooth.
c. as close as possible to the bisector.
d. parallel to the bisector.
5. When utilizing the bisecting technique, the central ray
of the x-ray beam is directed
a. perpendicular to the bisector.
b. parallel to the bisector.
c. perpendicular to the image receptor.
d. parallel to the image receptor.
6. Which of these target–image receptor distances is recommended for use with the bisecting technique?
a. 8 in. (20.5 cm)
b. 12 in. (30 cm)
c. 16 in. (41 cm)
7. Each of the following is a disadvantage of the bisecting
technique EXCEPT one. Which one is the EXCEPTION?
a. Produces images with dimensional distortion.
b. Often superimposes adjacent structures.
c. Estimating the location of the bisector may be
difficult.
d. May not be used with children or adults with small
oral cavities.
8. Image receptor holders designed for use with the bisecting technique should have a
a. short biteblock and L-shaped backing.
b. long biteblock and L-shaped backing.
c. short biteblock and 105º backing.
d. long biteblock and 105º backing.
9. Which of the following is NOT an image receptor holder
that can be used with the bisecting technique?
a. Snap-A-Ray®
b. SUPA®
c. BAI®
d. XCP®
CHAPTER 15 • THE PERIAPICAL EXAMINATION—BISECTING TECHNIQUE 195
10. Lining the image receptor up behind the distal half of
the second premolar to include the first, second, and
third molars describes the placement for which of the
following periapical radiographs?
a. Central incisors
b. Canine
c. Premolar
d. Molar
11. To determine the horizontal angulation for the mandibular premolar periapical radiograph, the central rays of
the x-ray beam should be directed at the image receptor
perpendicularly through the embrasures of the
a. canine and first premolar.
b. first and second premolars.
c. second premolar and first molar.
d. first and second molars.
12. When utilizing the bisecting technique, the recommended vertical angle setting for the maxillary premolar periapical radiograph is
a. degrees
b. degrees
c. degrees
d. degrees
13. When utilizing the bisecting technique, the recommended
vertical angle setting for the mandibular canine periapical
radiograph is
a. degrees
b. degrees
c. degrees
d. degrees
14. With the bisecting technique, what is the effect on the
radiographic image if the vertical angulation is significantly greater than necessary?
a. Overlapping
b. Conecutting
c. Elongating
d. Foreshortening
15. Elongation results from
a. excessive horizontal angulation.
b. inadequate horizontal angulation.
c. excessive vertical angulation.
d. inadequate vertical angulation.
16. Which of the following is the suggested point of entry
for directing the central ray of the x-ray beam when
exposing the maxillary incisors radiograph using the
bisecting technique?
a. The tip of the nose
b. The ala of the nose
c. A point on the ala-tragus line below the pupil of
the eye
d. A point on the ala-tragus line below the outer canthus
of the eye
-20
-15
+20
+40
-5
-10
+30
+45
17. Which of the following points 1 in. (2.5 cm) above the
lower border of the mandible is the suggested landmark
for directing the central ray of the x-ray beam when
exposing the mandibular premolar radiograph using the
bisecting technique?
a. The middle (symphysis) of the chin
b. The center of the root of the canine
c. Directly inferior to the pupil of the eye
d. Directly inferior to the outer canthus of the eye
REFLECT—Case study
Compare the paralleling (Chapter 14) and the bisecting techniques. Include answers to the following questions in your
discussion.
1. What are the major differences between the two techniques?
2. How are the two techniques similar?
3. What are the advantages/disadvantages of each of the
two techniques?
4. When would use of the bisecting/paralleling technique
be appropriate?
5. Describe the characteristics of the image receptor holder
appropriate for use bisecting/paralleling technique.
6. How does each of the four steps for exposing periapical radiographs (placement, vertical and horizontal
angulation, and point of entry) differ between the two
techniques? How are they similar?
7. Which technique do you anticipate being easier/more
difficult to master?
8. Would you recommend that radiographers learn one
technique over the other? Why/why not?
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this
topic, see Thomson, E. M. (2012). Exercises in oral radiography techniques: A laboratory manual 3rd ed.). Upper Saddle River, NJ: Pearson Education. Chapter 5, “Periapical
radiographs—bisecting technique.”
REFERENCES
Eastman Kodak Company. (2002). Successful intraoral radiography. Rochester, NY: Author.
Rinn Corporation. (1983). Intraoral radiography with Rinn
XCP/BAI instruments. Elgin, IL: Dentsply/Rinn Corporation.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Match the bitewing examination with two ideal uses.
3. Describe the bitewing radiographic technique.
4. List the four sizes of image receptors that can be used for bitewing surveys explaining
advantages and disadvantages of each size.
5. Differentiate between horizontal and vertical bitewing radiographs.
6. Identify the type, size, and number of image receptors best suited for a child bitewing
survey.
7. Explain the effect of horizontal angulation on the resultant bitewing image.
8. Identify positive and negative vertical angulations.
9. State the recommended vertical angulation for bitewing exposures.
10. Compare methods used for holding the bitewing image receptor in position.
11. Describe the image receptor placement, horizontal and vertical angulation, and point of
entry for horizontal and vertical posterior bitewing examinations.
12. Describe the image receptor placement, horizontal and vertical angulation, and point of
entry for a vertical anterior bitewing examination.
KEY WORDS
Bitetab
Bitewing radiograph
Contact point
Embrasure
External aiming device
Film loop
Horizontal angulation
Horizontal bitewing radiograph
Interproximal radiograph
Mean tangent
Overlap
Point of entry
Proximal surface
Vertical angulation
Vertical bitewing
radiograph
The Bitewing Examination
CHAPTER
16
CHAPTER
OUTLINE
 Objectives 196
 Key Words 196
 Introduction 197
 Fundamentals
of Bitewing
Radiography 197
 The Radiographic
Examination 198
 Holding the
Bitewing Image
Receptor
in Position 202
 Horizontal
and Vertical
Angulation
Procedures 203
 The Bitewing
Technique 207
 Review, Recall,
Reflect, Relate 212
 References 214
CHAPTER 16 • THE BITEWING EXAMINATION 197
Introduction
Bitewing radiographs are probably the most frequently performed intraoral dental radiographic technique. Bitewings are
most often exposed at the time of regularly scheduled recare or
recall appointments. Bitewing radiographs image the crowns
and alveolar bone of both the maxillary and mandibular teeth
on a single radiograph. The name bitewing is descriptive. Traditionally, the bitewing film packet had a tab, or wing, that was
either attached to the packet by the manufacturer or attached by
the radiographer as a holder (Figures 16-1 and 16-2). The
patient bites on this tab to hold the image receptor in place. The
purpose of this chapter is to present step-by-step procedures for
exposing bitewing radiographs.
Fundamentals of Bitewing Radiography
Bitewing (interproximal) radiographs may be taken as a series
or in conjunction with a full mouth series of periapical radiographs
or with a panoramic radiograph. Bitewing radiographs showing
the crowns and alveolar bone crests of both the maxillary and
mandibular teeth on the same image are ideal for examining
dental caries on the proximal surfaces of the teeth (where adjacent
teeth contact each other in the arch) and periodontal bone levels
supporting the teeth (Figure 16-3). The true value of the bitewing
radiograph is that it reveals caries in the very early stages when
remineralization treatment may be possible. This is particularly
important in the premolar and molar regions, where incipient
(small) caries are often concealed by the wide bucco-lingual
diameters of these teeth. Such caries are frequently unnoticed in
a visual inspection. Bitewing radiographs do not image the entire
tooth and therefore will not reveal apical conditions or lesions.
To expose a bitewing radiograph, the image receptor is positioned near and almost parallel to the teeth of both arches when
FIGURE 16-1 Bitewing tabs and loops. (A) Loop tabs; (B) Stickon tabs; (C) Size #3 film packet with manufacturer-attached tab.
FIGURE 16-2 Bitewing loop for digital sensor.
A B
FIGURE 16-3 (A) Horizontal and (B) vertical bitewing radiographs. Bitewing radiographs
are ideal at imaging the interproximal areas of the teeth to show caries and alveolar bone crests. Note
the increased coverage of the alveolar bone imaged on the vertical bitewing radiograph.
the patient’s teeth are occluded (closed). Bitewing image receptor
placement is often closer to the teeth, and the central ray of the
x-ray beam can be directed at a more ideal angle than for periapical
radiographs (Figure 16-4). With this ideal image receptor placement, the bitewing radiograph often images decay and the height
198 INTRAORAL TECHNIQUES
are also available in size #3. (see Figure 9-3) The advantage of
these image receptors is that only one image receptor needs to
be exposed on each side of the arch to image both premolars and
all molars on one image. However, when compared with the
standard #2 image receptor, the #3 has two disadvantages. One
is that most dental arches curve so that the horizontal angle
required to clearly image the proximal surfaces of the premolars
is not the same horizontal angle required to clearly image the
proximal surfaces of the molars. There are two slightly divergent
pathways of the posterior teeth. As the central rays pass through
these divergent embrasures, it is not likely that all of the interproximal spaces will be imaged clearly without overlapping.
The other disadvantage is that the long image receptor is
narrower in the vertical dimension than size #2 and may reveal
less of the periodontal crestal bone level (Figure 16-5).
As discussed in Chapter 13, the bitewing examination
may consist of two to eight images. The posterior bitewing
examination consists of either two (one on the left and one on
the right) or four (two on the left and two on the right) images
(Figure 16-6A,B). The image receptor orientation in the oral
cavity may be such that the longer dimension is placed
horizontally or vertically. Traditionally, the image receptor
has been placed horizontally in the posterior region. This
remains the placement of choice for children. However, if
there is a need to image more of the supporting bone, as is the
case in periodontally involved patients, a vertical bitewing is
recommended.
of the alveolar bone crest better than periapical radiographs. It is
because of this improved imaging for these conditions that bitewing
radiographs are taken in conjunction with periapical radiographs
of the same area when exposing a full mouth series.
The Radiographic Examination
Size, Number, and Placement of Image Receptors
The number and size of image receptors to use depends on the
type of survey required and the size and shape of the patient’s
oral cavity (Table 16-1). Additional factors to be considered
when deciding how many and what size image receptor to
select is the length and curvature of the arches, which vary in
all individuals. A single image receptor placed on each side of
the mouth often provides adequate coverage for children, prior to
the eruption of the permanent second molars. Although an
image receptor size #0 or #1 is usually used for a child with
primary teeth, the preferred size for mixed dentition is a #2.
However, tissue sensitivity or anatomical limitations must be
taken into consideration, so size is often based on the individual
patient. The advantage to using the largest size image receptor
possible is that the amount of structures imaged, including the
developing permanent teeth, will be increased. For most adults,
four #2 image receptors (two on each side) are generally preferred.
Size #3 (extra-long) radiographic film packets with preattached tabs are especially made for taking horizontal bitewing
radiographs. Phosphor plates used for indirect digital imaging
PID
Direction of central beam
+10 degrees
Bite
tab
Image receptor
Horizontal occlusal plane
Plane of floor
FIGURE 16-4 Bitewing placement. The
bitewing image receptor placement, slightly angled to
take advantage of the height of the midline of the
palate when the patient occludes, is such that the
coronal portion of both the maxillary and the
mandibular teeth will be recorded on the image. The
close relationship between the teeth and the image
receptor and the ideal angle of the x-ray beam allow
bitewings to accurately image caries and alveolar
bone crests.
TABLE 16-1 Suggested Image Receptor Size and Number to Use for Bitewing Radiographs
IMAGE
RECEPTOR SIZE RECOMMENDED FOR USE WITH THESE PATIENTS
NUMBER AND ORIENTATION
OF IMAGE RECEPTOR
#0 Child with primary dentition 2 horizontal posterior
#1 Child with primary or mixed dentition 2 horizontal posterior
Adult for caries detection or the presence of periodontal disease 3 or 4 vertical anterior
#2 Child with mixed dentition, prior to the eruption of the
permanent second molars
2 horizontal posterior
Adolescent after the eruption of the permanent second molars 4 horizontal posterior
Adult 4 horizontal posterior
Adult with periodontal disease 4 vertical posterior
#3 Adolescent after the eruption of the permanent second molars 2 horizontal posterior
Adult 2 horizontal posterior
CHAPTER 16 • THE BITEWING EXAMINATION 199
The anterior bitewing examination consists of either three
(one just left of center, one centered behind the central incisors,
and one just right of center; Figure 16-6C) or four (two just left of
center and two just right of center) images. The image receptor
orientation in the oral cavity is usually such that the longer
dimension is placed vertically. For ease of placement, especially
when using rigid digital sensors and to avoid bending the film
packet or phosphor plate, the narrow size #1 image receptor is
recommended, especially for imaging the lateral-canine region.
However, a size #2 may be used for the central incisors when the
arch permits. Using a longer bitetab than that used for the posterior
exposures may facilitate positioning the image receptor further
lingually in the mouth to avoid contact with the lingual gingiva or
curvature of the palate when the patient occludes. This may prevent
the film or phosphor plate from bending in the middle as the tab is
pulled forward when the patient is asked to bite down and may
avoid pushing down on or causing the receptor to slant in a way
that compromises the vertical angulation. Two stick-on paper
bitetabs may be attached to lengthen the bitetab for this purpose
(Figure 16-7).
The goal of image receptor placement is to image all contacts
(mesial and distal surfaces) of all of the teeth of interest. It is
important to remember that each bitewing—molar, premolar,
canine, and incisors—has a standard recommended placement.
This means that a premolar bitewing taken at one oral health care
practice will most likely image the same teeth as a premolar bitewing
exposed in every other practice. This standardization is important
to learn.
A
B
FIGURE 16-5 Comparison of size #2 and size #3
image receptors. (A) Size #2 has a shorter horizontal
dimension, taller vertical dimension. (B) Size #3 has a
longer horizontal dimension, shorter vertical dimension.
The incisors and canine radiographs instruct the radiographer to center the teeth of interest in the middle of the image
receptor. However anatomical considerations prevent centering
the premolars and molars. Instead the radiographer should focus
on placing the anterior edge of the image receptor and allow the
receptor, once in the correct position, to capture the images of
the appropriate teeth. For example, when placing the image
receptor for a premolar horizontal or vertical bitewing radiograph, the radiographer should not try to center the first and
second premolars. Because of the curvature of the arches and
the position of the canine, this is not usually possible. The radiographer should focus on placing the anterior edge of the image
receptor so that it lines up behind the distal half of the canine,
and the rest of the teeth should be imaged correctly.
It is important to visually inspect the patient’s occlusion to
determine which canine, maxillary, or mandibular, to use to align
the image receptor for exposure of premolar bitewing radiographs.
The premolar bitewing must image the distal portion of both the
maxillary and the mandibular canines to image the mesial surface
of the first premolar, one of the teeth of interest for this projection.
The radiographer should align the anterior edge of the image
receptor behind the canine that is further forward in the mouth
(the most mesial canine).
When placing the image receptor to image a molar horizontal
or vertical bitewing radiograph, the radiographer should focus
on placing the anterior edge of the image receptor so that it lines
up behind the distal half of the second premolar. Again, a visual
inspection of the patient’s occlusion will determine whether to line
200 INTRAORAL TECHNIQUES
up the image receptor with the maxillary or the mandibular
second premolar.
Generally, in Class I and III occlusal relationships, the radiographer will choose to align the anterior edge of the image receptor
behind the distal half of the mandibular canine for a premolar
bitewing radiograph and behind the distal half of the mandibular
second premolar for a molar bitewing radiograph. When a Class II
occlusal relationship presents, the radiographer will most likely
choose to align the anterior edge of the image receptor behind the
distal half of the maxillary canine for a premolar bitewing radiograph
and behind the distal half of the maxillary second premolar for a
molar bitewing radiograph (Figure 16-8). It should be noted that
patients often present with different occlusal relationships on the
right and left sides or individual teeth that are malaligned or
missing. It is important to perform a visual inspection prior to
each placement.
It is important to also position the image receptor well into
the oral cavity, a slight distance from the lingual surfaces of the
maxillary teeth, taking advantage of the midline where the palate
is at its highest to accommodate the image receptor and facilitate
correct stabilization and vertical alignment with the x-ray beam.
According to the shadow casting principles (see Chapter 13), the
image receptor should be positioned as close to the object (tooth)
as possible. However, if the image receptor is placed too close to
the maxillary teeth, especially in the premolar and anterior
regions, the top edge of the receptor may contact the lingual
gingiva or curvature of the palate when the patient occludes,
pushing down on or causing the receptor to slant away from the
correct position (Figure 16-9). A sloping or slanting (tilted)
occlusal plane is a frequent reason for having to retake bitewing
radiographs.
FIGURE 16-7 Two stick-on bitetabs lengthen the holder for use
in the anterior region.
A
B
C
FIGURE 16-6 Horizontal and vertical bitewing series. (A) Set of two horizontal posterior bitewing radiographs.
(B) Set of four horizontal posterior bitewing radiographs. (C) Set of seven vertical bitewing radiographs, including posterior
and anterior images.
CHAPTER 16 • THE BITEWING EXAMINATION 201
A
B
C
FIGURE 16-8 Occlusal relationships. (A) Class I occlusion
demonstrating that the mandibular canine and second premolar
(shaded) are located further forward in the oral cavity. (B) Class II
occlusion demonstrating that the maxillary canine and second
premolar (shaded) are located further forward in the oral cavity.
(C) Class III occlusion demonstrating that the mandibular canine
and second premolar (shaded) are located further forward in the oral
cavity.
FIGURE 16-9 Tilted image. The slanted occlusal plane
observed on this radiograph resulted from a failure to place the
image receptor far enough lingually to avoid being pushed down
by the palate when the patient occluded onto the bitetab.
PRACTICE POINT
Although contact with the lingual gingiva or curvature of the
palate or other obstruction such as tori is the most likely
cause of a tilted or slanting occlusal plane, other causes
include (1) failure of the patient to maintain a steady pressure
occluding on the bitetab, (2) patient swallowing while the
exposure is being made, (3) incorrect or slanted placement
of the bitetab or image receptor holder. The best corrective
action is to position the image receptor far enough away
from the lingual surfaces of the maxillary teeth to avoid
premature and excessive contact with the palate. Other
corrective actions include selecting the appropriately sized
image receptor and providing the patient with specific
instructions about securely biting on the bitetab and not
swallowing during exposure.
Sequence of Placement
It is recommended to always follow a systematic order when taking
radiographs to prevent errors and for efficiency (Table 16-2).
TABLE 16-2 Recommended Sequence for Exposing
Bitewing Radiographs
BITEWING SERIES RECOMMENDED SEQUENCE
2 posterior 1st: right premolar *
2nd: left premolar
4 posterior 1st: right premolar *
2nd: right molar
3rd: left premolar
4th: left molar
7 anterior and posterior 1st: central-lateral incisors
2nd: left canine *
3rd: right canine
4th: right premolar
5th: right molar
6th: left premolar
7th: left molar
8 anterior and posterior 1st: left canine *
2nd: left central-lateral incisors
3rd: right central-lateral incisors
4th: right canine
5th: right premolar
6th: right molar
7th: left premolar
8th: left molar
Left-handed radiographers may choose to begin the exposures on the
opposite side.
*
202 INTRAORAL TECHNIQUES
Chapter 13 explained at what point to take bitewing radiographs
when exposing a full mouth series. When exposing a set of four
posterior bitewings alone, it is recommended that the premolar
bitewing on one side be exposed first, followed by the molar
bitewing on the same side. Placing the image receptor for exposure
of the premolar may be more comfortable for the patient and less
likely to excite a gag reflex, gaining the patient’s confidence for
the molar placements that may sometimes be more difficult.
Then the premolar and molar bitewing on the opposite should be
exposed. Completing both the premolar and molar bitewing radiographs on one side first will avoid shifting the tube head back
and forth across the patient.
PRACTICE POINT
When using a stick-on tab holder, follow these steps for placement (Figure 16-10).
A B
C D
FIGURE 16-10 Bitewing placement using a stick-on tab. (A) Insert the image receptor completely into the
patient’s mouth. (B) Rotate until the image receptor is in a vertical position. Inserting in this manner allows the
image receptor to move the tongue out of the way. (C) Using the index finger of one hand, hold the bitetab firmly
against the occlusal surface of the mandibular teeth while the index finger of the other hand angles the top edge of
the image receptor into the midline of the palate. (D) Instruct the patient to close so that the teeth occlude normally.
Failure to hold the tab firmly may lead to a drift lingually and distally and increase the possibility that the tongue
will move the image receptor out of the correct position.
Holding the Bitewing Image Receptor
in Position
There are many commercially made holders for stabilizing a
film packet, phosphor plate, or digital sensor for bitewing exposures.
Stick-on paper or plastic bitetabs have the most versatility
because they can be fastened to the image receptor for both
horizontal and vertical bitewings. The paper or plastic film loop
into which a film packet or digital sensor can be slid is limited
to horizontal bitewings. Bitetabs and loops are easy to use,
disposable, and readily tolerated by the patient. Bitetabs must
be attached to the white unprinted side (front) of the film packet
CHAPTER 16 • THE BITEWING EXAMINATION 203
Image receptor
holder
Image receptor
Bitewing biteblock
Positioning arm
Aiming ring
FIGURE 16-11 Bitewing image receptor holder with metal
positioning arm and plastic external aiming ring.
(Courtesy of Dentsply Rinn.)
Many holders (including the Dentsply Rinn XCP® and Flow
Dental RAPD® introduced in Chapter 14) designed for positioning
the image receptor for periapical radiographs include a bitewing
biteblock that can be used with the metal positioning arm and
plastic external aiming ring to assist with locating correct angles
and points of entry, making errors less likely (Figure 16-11). The
external aiming device also eliminates the need to position the
patient’s head precisely. Biteblock image receptor holder attachments
are available for both horizontal and vertical bitewings. It should
be noted that the plastic biteblock on some holders is wider than
paper/plastic bitetabs and loops and may prevent the patient from
biting down far enough to image the greatest amount of alveolar
bone (Figure 16-12). This is especially important when periodontal disease is suspected or present. To overcome this disadvantage,
the vertical bitewing biteblock attachment can be substituted.
Regardless of the holder used, care should be taken to
ensure that the image receptor is positioned in such a manner
that it is evenly divided between the maxillary and mandibular teeth. Once the image receptor is satisfactorily positioned,
the patient must close down on the tab or biteblock in an
edge-to-edge relationship and hold it there for the duration of
the exposure.
It is important to note that if an image receptor holder with
an external aiming device is not positioned correctly, the aiming
device will indicate directing the x-ray beam to the wrong place.
For this reason, it is important that the radiographer develop the
skills necessary to evaluate placement of the image receptor for
correctness, regardless of the holder used.
or the plain side of the phosphor plate or digital sensor (over the
plastic infection control barrier; see Chapter 10) so that this
side will face the PID (x-rays) when placed intraorally.
Generally the bitetab or loop is visible extraorally after the
patient bites down to stabilize the image receptor. This extension
of the tab serves as a guide for directing the central rays toward
the center of the image receptor. Without a significantly visible
external aiming device,some operators find it difficult to determine
the correct horizontal and vertical angulations and centering of
the image receptor within the x-ray beam.
Horizontal and Vertical Angulation
Procedures
The correct horizontal and vertical angulations are critical to
producing a quality bitewing radiograph.
Horizontal Angulation is the positioning of the central ray
(PID) in a horizontal (side-to-side) plane and is of critical importance when exposing bitewing radiographs. The horizontal angulation for bitewing exposures is the same as that used for
periapical radiographs of the same region (see Chapter 14). The
central ray (PID) should be directed perpendicular to the curvature of the arch or mean tangent, through the contact points of
the teeth (see Figure 13-8). To rely on the image receptor
holder’s external aiming ring to accurately direct the central ray
perpendicularly (at a right angle) toward the surface of the image
receptor in a horizontal plane, the image receptor itself must be
positioned parallel to the teeth of interest in the horizontal
dimension. The image receptor must be positioned parallel to the
interproximal space or embrasure of two predetermined teeth.
The teeth selected depend on the region being imaged. Table 16-3
A
B
FIGURE 16-12 Holder comparison. (A) Bitewing radiograph
taken using a disposable paper stick-on bitetab. (B) Bitewing
radiograph taken using a thicker plastic, autoclavable image receptor
holding device. Notice the wider space between the occlusal surfaces
of the maxillary and mandibular teeth.
204
TABLE 16-3 Summary of Steps for Acquiring Bitewing Radiographs
BITEWING
RADIOGRAPH PLACEMENT
VERTICAL
ANGULATION*
HORIZONTAL
ANGULATION POINT OF ENTRY*
Central incisors (vertical)
(image receptor size #1 or
size #2) (Figure 16-17)
Center the image receptor to line up behind the
central and lateral incisors; if using a size #2
image receptor, include the mesial halves of
the canines.
Align the image receptor parallel to the long axes
of the incisors and parallel to the left and right
central incisor embrasure.
+10 Direct the central ray perpendicular to the image receptor
through the left and right
central incisor embrasure.
Center the image receptor within
the x-ray beam by directing the
central ray at the center of the
image receptor at a spot on the
incisal plane between the maxillary and mandibular central
incisors.
Canine (vertical) (image
receptor size #1 or size
#2) (Figure 16-18)
Center the image receptor to line up behind the
maxillary and mandibular canines; include the
lateral incisor and the first premolar
Align the image receptor parallel to the long axes
of the canines and parallel to the mesial and
distal line angles of the canines.
+10 Direct the central ray perpendicular to the image receptor at
the center of the canine.
To minimize distal overlap of
the canine with the lingual
cusp of the first premolar
shift the PID no more than
10 degrees toward the
distal.
Center the image receptor within the
x-ray beam by directing the central ray at the center of the image
receptor at a spot on the incisal
plane between the maxillary and
mandibular canines.
Premolar (horizontal or vertical) (image receptor size
#2) (Figure 16-19)
Align the anterior edge of the image receptor to line
up behind the distal half of the maxillary or
mandibular canine. Choose the most mesially
positioned canine; include the first and second
premolars and mesial half of the first molar.
Align the image receptor parallel to the long axes
of the premolars and parallel to the first and second premolar embrasure.
+10 Direct the central ray perpendicular to the image receptor
through the first and second
premolar embrasure.
Center the image receptor within
the x-ray beam by directing the
central ray at the center of the
image receptor at a spot on the
occlusal plane between the
maxillary and mandibular second premolars.
205
Molar (horizontal or vertical) (image receptor
size #2)
(Figure 16-20)
Align the anterior edge of the image receptor to line up behind the distal half of the
maxillary or mandibular second premolar. Choose the most mesially located
second premolar; include the first, second, third molars (horizontal placement); include the first, second molars
(vertical placement)
Align the image receptor parallel to the long
axes of the molars and parallel to the first
and second molar embrasure.
+10 Direct the central ray perpendicular to the image receptor through the first and
second molar embrasure.
Center the image receptor
within the x-ray beam by
directing the central ray at
the center of the image
receptor at a spot on the
occlusal plane between the
maxillary and mandibular
first molars.
Premolar-molar (image
receptor size #3)
Align the anterior edge of image receptor to
line up behind the distal half of the maxillary or the mandibular canine. Choose the
most mesially located canine; include all
premolars and molars on the image.
+10 Direct the central ray perpendicular to the image
receptor through the second premolar and first
molar embrasure.
Center the image receptor
within the x-ray beam by
directing the central ray at
the center of the image
receptor at a spot on the
occlusal plane between the
maxillary and mandibular
second premolars.
Molar (child) (horizontal) (image receptor
size #1 or size #2)
Align the anterior edge of the image receptor
to line up behind the distal half of the
maxillary or the mandibular canine.
Choose the most mesially located canine;
include the remaining erupted teeth on the
image.
+5 to +10 Direct the central ray perpendicular to the image receptor through the first and
second primary molar
embrasure; or, if erupted,
the first and second premolar embrasure.
Center the image receptor
within the x-ray beam by
directing the central ray at
the center of the image
receptor at a spot on the
occlusal plane between the
primary maxillary and
mandibular first molars; or,
if erupted, the maxillary
and mandibular second
premolars.
*The patient must be seated in the correct position, with the occlusal plane parallel to the floor and the midsaggital plane perpendicular to the floor.
206 INTRAORAL TECHNIQUES
VERTICAL ANGULATION The correct vertical angulation for
bitewing radiographs is degrees. (A degree vertical
angulation is sometimes recommended for children. See Chapter
26.) Positioning the PID at this slightly downward position will
more likely match the vertical slant of the image receptor when
it is correctly placed into the oral cavity (Figure 16-4). Because
bitewing radiographs are placed to image both the maxillary and
the mandibular teeth on one image, consideration is given to the
+10 +5
A
B
C
FIGURE 16-13 Horizontal angulation. (A) Mesiodistal
projection of the x-ray beam shown here deviates from a right angle by
about 15º, resulting in greater overlap of the contacts in the posterior
region of the radiograph. (B) Correct horizontal projection of the x-ray
beam produces no overlapping. (C) Distomesial projection of the x-ray
beam shown here deviates from a right angle about 15º, resulting in
greater overlap of the contacts in the anterior region of the radiograph.
A
B
FIGURE 16-14 Horizontal overlap error. (A) When the PID is
directed obliquely from the mesial (mesiodistal projection of the
x-ray beam), the overlapping will be more severe in the distal or
posterior region of the image. (B) When the horizontal angulation is
directed obliquely from the distal (distomesial projection of the x-ray
beam), the overlapping will be more severe in the mesial or anterior
region of the image.
lists the embrasure to align the image receptor behind and
through which to direct the central ray for each projection. The
central ray must be directed appropriately to avoid overlapping
adjacent teeth on the resultant image (Figure 16-13). The contact points should appear open or separate from each other on
the resultant radiograph. When the horizontal angulation is
directed obliquely from the mesial, the overlapping will be more
severe in the distal or posterior region of the image; when the
horizontal angulation is directed obliquely from the distal, the
overlapping will be more severe in the mesial or anterior region
of the image (Figure 16-14). Because bitewing radiographs are
taken to reveal information about the interproximal areas of the
teeth, radiographs with overlapping error are undiagnostic.
It is important to note that even with correct horizontal
angulation, the canine bitewing will often exhibit significant
overlap of the distal portion of the canines with the mesial
portions of the first premolars. The anatomical positions of
the canines, which are anterior teeth, and the premolars,
which are posterior teeth, is such that the lingual cusp of the
first premolar is often superimposed over the distal edge of the
canine. To minimize this occurrence the horizontal angulation
should first be aligned correctly to direct the central ray of
the x-ray beam perpendicular to the image receptor at the
center of the canine and then shift the PID no more than 10
degrees toward the distal (see Chapter 28).
anatomic positions of the teeth in both arches. In the posterior
region, the maxillary teeth have a slight buccal inclination, whereas
the mandibular teeth often have a slight lingual inclination. This
anatomical relationship allows a slight degree slant to the
image receptor. Positioning the PID to match this angle will
produce the best image. In addition, adjusting the vertical angulation
of the PID to degrees will match the slight angle the image
receptor takes on when the patient closes and the palate pushes
down against the receptor in both the posterior and the anterior
regions. If using an image receptor holder with an external aiming device, it is important that the patient occludes fully on the
biteblock so that the aiming ring will direct the operator to the
correct vertical angle.
Incorrect vertical angulation results in an unequal distribution of the arches on the radiograph. A quality bitewing radiograph should image an equal portion of the maxillary and
mandibular teeth plus a portion of the supporting bone. When
the vertical angulation is excessive (greater than ), more +10°
+10
+10
CHAPTER 16 • THE BITEWING EXAMINATION 207
PRACTICE POINT
To avoid molar overlap follow these steps for placement
(Figure 16-15).
Aiming device (ring)
Aiming device (ring)
Image
receptor
Image
receptor
Biteblock
Biteblock
PID
PID
A
B
FIGURE 16-15 Avoiding molar overlap when using
a holder with external aiming device. (Courtesy of
Dentsply Rinn.) (A) Note the recommended premolar
bitewing placement positions the image receptor
slightly diagonal with the front edge of the image
receptor farther from the lingual of the teeth than the
back part. (B) Because the proximal surfaces of the
molar teeth are in a mesiodistal relationship to the
sagittal plane, it is recommended that the image
receptor be positioned perpendicularly to the
embrasures, resulting in a diagonal placement similar to
the premolar position.
Point of Entry
The point of entry for the central ray for all bitewing exposures
is on the level of the incisal or occlusal plane (near the lip line) at
a point opposite the center of the image receptor and through the
interproximal spaces of the teeth of interest (Figure 16-4). An
image receptor holder with an external aiming device will assist
with determining the accurate point of entry. Incorrect point of
entry, or not centering the image receptor within the x-ray beam,
will result in conecut error, where the portion of the image receptor that was not in the path of the x-ray beam will be clear or
blank on the resultant radiograph (see Figures 18-7 and 18-8).
The Bitewing Technique
Figures 16-17 through 16-20 illustrate the precise image
receptor positions and required angulations for each of the
horizontal and vertical bitewing radiographs discussed in this
chapter. See Table 16-3 for a summary of the four basic steps
of the technique—placement, vertical angulation, horizontal
angulation, and point of entry.
maxillary teeth and bone are imaged, cutting off a portion of
the mandibular structures. When the vertical angulation is
inadequate (less than ), more mandibular teeth and bone
are imaged, cutting off a portion of the maxillary structures
(Figure 16-16).
+10°
FIGURE 16-16 Vertical angulation error. (A) Inadequate
vertical angulation results in imaging more of the mandible.
(B) Excessive vertical angulation results in imaging more
of the maxilla.
A
B
FIGURE 16-17 Central incisors bitewing exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID.
(B) Vertical angulation is directed perpendicular to the image receptor at approximately with the PID tilted downward. Central ray is
directed at the center of the image receptor at a spot on the incisal plane between the maxillary and mandibular teeth. (C) Patient showing
position of image receptor holder and 12-in. (30-cm) circular PID. (D) Central incisor bitewing radiograph. In the anterior region, the image
receptor is positioned with the long dimension vertical.
+10°
A
Aiming device (ring)
Image
receptor
Biteblock
C D
BITEWING TECHNIQUE
Central Incisors Bitewing Exposure
PID
Image
receptor
PID
Direction of central beam
+10 degrees
Plane of floor
B
208 INTRAORAL TECHNIQUES
CHAPTER 16 • THE BITEWING EXAMINATION 209
FIGURE 16-18 Canine bitewing exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID.
(B) Vertical angulation is directed perpendicular to the image receptor at approximately with the PID tilted downward. Central ray is
directed at the center of the image receptor at a spot on the incisal plane between the maxillary and mandibular teeth. (C) Patient showing
position of image receptor holder and 12-in. (30-cm) circular PID. (D) Canine bitewing radiograph. In the anterior region, the image receptor is
positioned with the long dimension vertical.
+10°
C D
A
Aiming device (ring)
Image
receptor
Biteblock
BITEWING TECHNIQUE
Canine Bitewing Exposure
PID
Image
receptor
PID
Direction of central beam
+10 degrees
Plane of floor
B
210 INTRAORAL TECHNIQUES
C
D E
A
Aiming device (ring) Image
receptor
Bite block
BITEWING TECHNIQUE
Premolar Bitewing Exposure
PID Image
receptor
Direction of central beam
+10 degrees
Plane of floor
B
FIGURE 16-19 Premolar bitewing exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID.
(B) Vertical angulation is directed perpendicular to the image receptor at approximately degrees with the PID tilted downward. Central ray
is directed at the center of the image receptor at a spot on the occlusal plane between the maxillary and mandibular teeth. (C) Patient showing
position of image receptor holder and 12-in. (30-cm) circular PID. (D) Horizontal premolar bitewing radiograph. (E) Vertical premolar bitewing
radiograph. In the posterior region, the image receptor may be positioned with the long dimension horizontal or vertical.
+10
l be
FIGURE 16-20 Molar bitewing exposure. (A) Diagrams show the relationship of the image receptor and holder, teeth, and PID.
(B) Vertical angulation is directed perpendicular to the image receptor at approximately degrees with the PID tilted downward. Central ray
is directed at the center of the image receptor at a spot on the occlusal plane between the maxillary and mandibular teeth. (C) Patient showing
position of image receptor holder and 12-in. (30-cm) circular PID. (D) Horizontal molar bitewing radiograph. (E) Vertical molar bitewing
radiograph. In the posterior region, the image receptor may be positioned with the long dimension horizontal or vertical.
+10
CHAPTER 16 • THE BITEWING EXAMINATION 211
BITEWING TECHNIQUE
Molar Bitewing Exposure
C
D E
B
PID
Direction of central beam
+10 degrees
Plane of floor
A
Aiming device (ring) Image
receptor
PID
Bite
tab Image receptor
212 INTRAORAL TECHNIQUES
REVIEW—Chapter summary
Bitewing radiographs image the coronal portion of both maxillary
and mandibular teeth on one image receptor. Bitewing radiographs supplement and complete the full mouth survey because
of their improved ability to image incipient caries in the tooth contact areas and early resorptive changes in the alveolar bony crest.
The size and number of images to expose depend on the
type of survey required and the size and shape of the patient’s
oral cavity. The image receptor may be positioned with the long
dimension horizontally or vertically. Traditionally posterior
bitewing radiographs have been positioned horizontally. Anterior bitewing radiographs are positioned vertically. Vertical
positioning in the posterior regions image more periodontal
bone. The patient’s occlusal relationship should be used to
determine which arch the radiographer should focus on during
placement of the image receptor. Positioning the image receptor a slight distance away from the lingual surfaces of the maxillary teeth of interest will help avoid contact with the curvature
of the palate and avoid producing a sloping or slanted image
that may result in a retake. Using a systemic order of sequence
in exposing bitewing radiographs will help avoid errors.
Image receptor holders/positioners include stick-on or loop
bitetabs and instruments with external aiming devices that assist
with determining the correct horizontal and vertical angulations
and the points of entry. If a holder without an external aiming
device is used, the horizontal angulation is determined by directing the central ray of the x-beam perpendicular to the recording
plane of the image receptor through the mean tangent of the
embrasures between the teeth of interest, and the vertical angulation for all bitewing radiographs is degrees. When the
horizontal angulation is directed obliquely from the mesial,
overlapping will be more severe in the distal or posterior region
of the image; when the horizontal angulation is directed
obliquely from the distal, overlapping will be more severe in the
mesial or anterior region of the image. When the vertical angulation is excessive (greater than ), more maxillary teeth
and bone are imaged, cutting off a portion of the mandibular
structures. When the vertical angulation is inadequate (less than
) more mandibular teeth and bone are imaged, cutting off a
portion of the maxillary structures. Directing the central ray of
the x-ray beam at the level of the incisal/occlusal plane (at the
lip line) will assist with directing the central ray of the x-ray
beam to the center of the image receptor to avoid conecut error.
The four basic steps to exposing a bitewing radiograph are
placement, vertical angulation, horizontal angulation, and point
of entry. Step-by-step illustrated instructions for exposing anterior and posterior bitewing radiographs are presented.
RECALL—Study questions
1. Which of these conditions would NOT be visible on a
bitewing radiograph?
a. Proximal surface caries
b. Overhanging restoration
c. Apical abscess
d. Alveolar crest resorption
+10°
+10°
+10
2. How many standard-sized #2 image receptors are recommended for a posterior horizontal bitewing survey of
an adult patient?
a. 2
b. 4
c. 7
d. 8
3. In which of the following situations would using a size
#3 image receptor be acceptable?
a. Horizontal bitewings on a child patient who presented
a need for them
b. Horizontal bitewings on an adult patient for caries
detection
c. Horizontal bitewings on an adult patient with periodontal disease
d. Vertical bitewings on any patient who presented with
a need for them
4. In which of the following conditions would vertical
bitewing radiographs be recommended over horizontal
bitewing radiographs?
a. Child with rampant caries
b. Adolescent with suspected third molar impactions
c. Adult with malaligned teeth
d. Adult with periodontal disease
5. Which size image receptor is used, and how is it positioned for exposure of an anterior bitewing radiograph
of a small and narrow adult arch?
a. Size #3 placed vertically
b. Size #2 placed horizontally
c. Size #1 placed vertically
d. Size #0 placed horizontally
6. When taking a premolar horizontal bitewing
radiograph, the anterior edge of the image receptor
should be positioned behind the distal edge of the
maxillary canine when presented with which occlusal
relationship?
a. Class I
b. Class II
c. Class III
7. When taking a set of eight vertical bitewing radiographs, which of the following should be exposed
first?
a. Left molar bitewing
b. Left premolar bitewing
c. Right canine bitewing
d. Right premolar bitewing
8. Which of the following best fits this description: “Disposable, may be used for placing both horizontal and
vertical bitewings, and provides increased imaging of
the alveolar bone”?
a. Stick-on bitetabs
b. Manufacturer preattached bitetabs
c. Bite loops
d. Holder with external aiming device
CHAPTER 16 • THE BITEWING EXAMINATION 213
9. An error in which of these results in overlapping?
a. Placement of image receptor
b. Point of entry
c. Vertical angulation
d. Horizontal angulation
10. What is the approximate vertical angulation for adult
bitewing radiographs?
a. degrees
b. 0 degrees
c. degrees
d. degrees
11. An error in vertical angulation will result in
a. unequal distribution of the arches.
b. overlapping.
c. overexposure to the patient.
d. conecut.
12. The image receptor placement for an adult horizontal
molar bitewing is to align the receptor so that the
a. central and lateral incisors are centered.
b. canine is centered.
c. anterior portion of the receptor lines up behind the
distal half of the canine.
d. anterior portion of the receptor lines up behind the
distal half of the second premolar.
13. The image receptor placement for an adult vertical premolar bitewing is to align the receptor so that the
a. central and lateral incisors are centered.
b. canine is centered.
c. anterior portion of the receptor lines up behind the
distal half of the canine.
d. anterior portion of the receptor lines up behind the
distal half of the second premolar.
+20
+10
-10
14. Through which interproximal space should the central
ray of the x-ray beam be perpendicularly directed when
exposing a molar bitewing on a child with primary
teeth?
a. Between the central and lateral incisors
b. Between the lateral incisor and canine
c. Between the canine and first molar
d. Between the first and second molars
15. Through which interproximal space should the central
ray of the x-ray beam be perpendicularly directed when
exposing a premolar bitewing on an adolescent with
permanent teeth?
a. Between the central and lateral incisors
b. Between the lateral incisor and canine
c. Between the canine and first premolar
d. Between the first and second premolars
REFLECT—Case study
Study the dental chart and patient record that follows. Note the
dentist’s written prescription for a radiographic examination.
Decide the following:
1. What type of bitewings will most likely be exposed?
2. What size image receptor will best fit this patient?
3. How many image receptors will be required to complete the exam?
4. Write out a detailed procedure for exposing each of the
required radiographs. Include:
a. Specific image receptor placements
b. The vertical angulation required
c. How the horizontal angulation will be determined
d. What the point of entry will be
Clinically visible restoration
Clinically visible carious lesion
Clinically missing tooth
Case: New patient to your practice.
Age/Gender: 40-year-old male.
Medical History: Hypertension.
Dental History: Has had extensive dental treatment
in the past as evidenced by several
extractions and restored teeth.
Social History: Appears nervous of dental treatment.
Chief Complaint: Thinks he has “gum disease.”
Current Oral Generalized 4–6 mm pockets;
Hygiene Status: Generalized moderate gingivitis.
Initial Treatment: Take a set of bitewing radiographs.
Probe
Probe
Probe
Probe
R
R
214 INTRAORAL TECHNIQUES
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this
topic, see Thomson, E. M. (2012). Exercises in oral radiography techniques: A laboratory manual (3rd ed.). Upper Saddle River, NJ: Pearson. Chapter 2, “Bitewing radiographic
technique.”
REFERENCES
Eastman Kodak Company. (2002). Successful intraoral radiography. Rochester, NY: Author.
Rinn Corporation. (1989). Intraoral radiography with Rinn
XCP/BAI instruments. Elgin, IL: Dentsply/Rinn Corporation.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
Wilkins, E. M. (2010). Clinical practice of the dental hygienist
(10th ed.). Philadelphia: Lippincott Williams & Wilkins.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. State the purpose of the occlusal examination.
3. List the indications for occlusal radiographs.
4. Match the topographical and cross-sectional techniques with the condition to be imaged.
5. Compare the patient head positions for the topographical and the cross-sectional techniques.
6. Demonstrate the steps for the maxillary and mandibular topographical surveys.
7. Demonstrate the steps for the mandibular cross-sectional survey.
KEY WORDS
Cross-sectional technique
Occlusal radiograph
Topographical technique
The Occlusal Examination
CHAPTER
17
CHAPTER
OUTLINE
 Objectives 215
 Key Words 215
 Introduction 216
 Types of Occlusal
Examinations 216
 Fundamentals
of Occlusal
Radiographs 216
 Horizontal
and Vertical
Angulation
Procedures 217
 Points of Entry 218
 The Occlusal
Examination 219
 Review, Recall,
Reflect, Relate 225
 References 226
216 INTRAORAL TECHNIQUES
Introduction
The purpose of the occlusal examination is to view large areas
of the maxilla (upper jaw) or the mandible (lower jaw) on one
radiograph. The image receptor is placed in the mouth
between the occlusal surfaces of the maxillary and mandibular
teeth. The patient occludes (bites) lightly on the image receptor
to stabilize it.
The purpose of this chapter is to discuss the use and
explain the procedures for the occlusal examination.
Types of Occlusal Examinations
Occlusal radiographs are either topographical or cross-sectional.
Topographical Technique
The topographical technique produces an image that looks
like a large periapical radiograph (Figure 17-1). The topographical occlusal technique is similar to the bisecting technique used to produce periapical radiographs (see Chapter
15). Topographical occlusal radiographs may be exposed in
any area of the oral cavity, the anterior and posterior regions
of both the maxilla and the mandible. Topographical
occlusal radiographs are best used to image conditions of
the teeth and supporting structures when a larger area than
that imaged by a periapical radiograph is required. Topographical occlusal surveys generally yield a greater amount
of information in the alveolar crest and apical areas than
periapical radiographs.
Cross-sectional Technique
The cross-sectional technique produces an image much like
its name implies (Figure 17-1). The circular or elliptical
appearance of the teeth on the radiograph and the increased
coverage of the sublingual area (under the tongue) allow the
cross-sectional occlusal radiograph to yield more information
about the location of tori and impacted or malpositioned teeth
and calcifications of soft tissues.
Fundamentals of Occlusal Radiographs
The occlusal examination may be made alone or to supplement
periapical or bitewing radiographs. The large size #4 occlusal
image receptor is useful for recording information that cannot
be adequately recorded on the smaller periapical image receptors. Occlusal radiographs are used to:
• Locate supernumerary, unerupted, or impacted teeth (especially impacted canines and third molars)
• Locate retained roots of extracted teeth
• Detect the presence, locate, and evaluate the extent of disease and lesions (cysts, tumors, etc.)
• Locate foreign bodies in the jaws
• Reveal the presence of salivary stones (sialoliths) in the
ducts of the sublingual and submandibular glands
• Aid in evaluating fractures of the maxilla or mandible
• Show the size and shape of mandibular tori
A B
FIGURE 17-1 A comparison of topographical and cross-sectional occlusal radiographs. (A) The
topographical occlusal radiograph of the anterior mandible closely resembles a periapical radiograph.
Note how the large occlusal film images a larger portion of the region. (B) The cross-sectional occlusal
radiograph of the mandibular anterior region reveals more information about the sublingual area
(under the tongue) and conditions of the soft tissue than about the teeth and the supporting bone.
CHAPTER 17 • THE OCCLUSAL EXAMINATION 217
• Aid in examining patients with trismus who can open their
mouths only a few millimeters
• Evaluate the borders of the maxillary sinus
• Examine cleft palate patients
• Substitute for a periapical examination on young children
who may not be able to tolerate periapical image receptor
placement (see Chapter 26)
Occlusal radiographs may be taken in any region of the
oral cavity. This chapter focuses on five of the most common
standard placements:
1. Maxillary topographical (anterior)
2. Maxillary topographical (posterior)
3. Mandibular topographical (anterior)
4. Mandibular topographical (posterior)
5. Mandibular cross-sectional
Image Receptor Requirements
The large #4 film or phosphor
plate is used for occlusal radiographs on most adult patients.
Currently this larger size #4 is not available as a digital sensor. Smaller size #2 intraoral image receptors may also be
used, depending on the area to be examined. The standard #2
periapical film or sensor is frequently used with children,
either to image labiolingual or buccolingual unerupted tooth
positions or in place of periapical radiographs when needed.
Orientation of the Image Receptor
An image receptor holder is not used for occlusal radiographs.
The image receptor is held in place during the exposure by
slight pressure of the teeth of the opposite jaw.
When using a size #4 film, the packet is positioned with
the white unprinted side (front side) against the arch of interest.
When using a phosphor plate, the plain side is positioned
against the arch of interest. When imaging the mandibular arch,
the white, unprinted side of the image receptor will face the
mandible. When imaging the maxillary arch, the white,
unprinted side of the image receptor will face the maxilla. The
image receptor may be placed into the mouth with the long
dimension positioned horizontally or vertically, centered over
one small region of interest or over the entire right or left sides
of the dental arches. The position used will depend on the type
of occlusal radiograph needed and the area to be imaged.
In the correct position, the image receptor should be
placed well back into the mouth, but with at least 1/4 in.
(1/2 cm) protruding outside the mouth to avoid cutting off
part of the image. Because the embossed identification dot
(on the film packet) should be positioned away from the area
of interest, positioning it toward the anterior should leave it
outside the mouth and therefore prevent it from interfering
with the image.
Patient Positioning
Because predetermined vertical angulations and points of
entry are utilized in taking occlusal radiographs (just as
3 * 2 1/4 in. 17.7 * 5.8 cm2
they are for periapical radiographs using the bisecting technique), it is very important that the patient be seated with
the head in the correct position for the area to be imaged.
For occlusal radiographs taken on the maxilla, the patient
should be seated with the occlusal plane parallel to the
plane of the floor and the midsagittal plane perpendicular to
the plane of the floor (see Figure 13-14). The head position
for the mandibular exposures will depend on the type of
occlusal radiograph to be produced. Topographical occlusal
radiographs of the mandible may be taken with the head
positioned the same as for maxillary exposures, with the
occlusal plane parallel to the floor and the midsagittal plane
perpendicular to the floor. Mandibular cross-sectional
occlusal radiographs are taken with the patient reclined in
the chair so that the head is tipped back, positioning the
occlusal plane perpendicular to the plane of the floor
(Figure 17-2).
Exposure Factors
The exposure factors (kVp, mA, and time) used for occlusal
radiographs are usually the same as those settings used for
periapical and bitewing radiographs of the same region.
Horizontal and Vertical Angulation
Procedures
Horizontal Angulation
The correct horizontal angulation for topographical occlusal
radiographs is determined in the same manner as for periapical and bitewing radiographs; by directing the central rays at
the image receptor perpendicularly through the teeth embrasures (spaces). When exposing anterior topographical
occlusal radiographs, direct the central rays of the x-ray beam
perpendicular to the image receptor through the interproximal
embrasures of the anterior teeth. When exposing posterior
topographical occlusal radiographs, direct the central rays of
the x-ray beam perpendicular to the image receptor through
Floor
X-ray unit
Image receptor
FIGURE 17-2 Patient positioning for mandibular crosssectional occlusal radiographs. Patient reclined in the chair so
that the head is tipped back, positioning the occlusal plane
perpendicular to the plane of the floor. The central rays of the x-ray
beam are directed toward the image receptor perpendicularly.
218 INTRAORAL TECHNIQUES
Image receptor
Bisector
of angle
Central ray
Central ray
90°
B
A
90° Bisector
of angle
FIGURE 17-3 Angulation theory of topographical occlusal
radiographs. The image receptor placement for occlusal
radiographs is not parallel to the long axes of the teeth being
imaged. Based on the bisecting technique, vertical angulation for
(A) maxillary and (B) mandibular topographical radiographs is
determined by directing the central rays of the x-ray beam
perpendicular to the imaginary bisector between the plane of the
image receptor and the long axes of the teeth of interest.
the interproximal spaces or embrasures of the posterior teeth.
The horizontal angulation for the mandibular cross-sectional
is also such that the central rays will intersect the image
receptor perpendicularly. This alignment is best determined
by positioning the open end of the PID parallel to the image
receptor.
Vertical Angulation
The vertical angulation for topographical occlusal radiographs
follows the rules of the bisecting technique used for periapical
radiographs, where the central rays of the x-ray beam are
directed through the apices of the teeth perpendicularly toward
the bisector (Figure 17-3). To determine the correct vertical
angulation when taking a topographical occlusal radiograph,
the radiographer must observe the plane of the image receptor,
locate the long axes of the teeth of interest, and estimate the
imaginary bisector of these two planes. If the patient’s head is
in the correct position, the radiographer can use predetermined
vertical angulation settings (Table 17-1).
The vertical angulation for the mandibular cross-sectional occlusal radiograph of the mandible is such that the
central rays of the x-ray beam are directed toward the image
receptor perpendicularly (Figure 17-2). To achieve a perpendicular relationship between the plane of the image receptor
and the central rays of the x-ray beam, the patient’s head
position must be such that the occlusal plane is perpendicular
to the plane of the floor. In other words, the patient should be
reclined and the chin tipped upward. In this position, the vertical angulation will most likely be set at 0º, allowing the x-rays
to strike the image receptor perpendicularly.
Cross-sectional occlusal radiographs of the maxilla are
sometimes needed to assess the maxillary sinus, edentulous
ridges, or other specific needs. However, the significant amount
of bony structures located here make cross-sectional occlusal
radiographs of the maxilla difficult to image with clarity. Therefore maxillary cross-sectional occlusal radiographs are exposed
less frequently.
Points of Entry
If the patient’s head is in the correct position, predetermined
points of entry may be used (Table 17-2). Essentially, the
central rays of the x-ray beam should strike the middle of
the image receptor. The open end of the PID must be aligned
as close as possible to the patient’s skin at the correct point
of entry. Although occlusal radiographs can be made with
any length position indicating device (PID), the shorter 8-in.
(20.5-cm) length may be easier to position into the increased
vertical angulation positions required for this technique. In
addition, because of the angular relationship between the
object (teeth) and the central ray of the x-ray beam, a longer
PID length (16-in./41-cm) will likely add to the dimensional
distortion of the image.
PRACTICE POINT
When exposing an occlusal radiograph on the mandible, it may
be necessary to modify placement of the lead/lead equivalent
thyroid collar. Although it is very important to use ALARA (as
low as reasonably achievable) practices and use the lead/lead
equivalent thyroid collar to protect radiation-sensitive tissues
in the head and neck region, the thyroid collar may be in the
path of the primary beam during mandibular topographical
and/or cross-sectional techniques.
You should place the lead/lead equivalent apron and
thyroid collar on the patient in the usual manner. After
adjusting the patient’s head position and placing the image
receptor, align the PID and check to be sure that the thyroid
collar is not in the path of the x-ray beam. If the thyroid collar is in a position that will block the x-rays from reaching the
image receptor, adjust the collar position. Failure to remove
the thyroid collar from in front of the open end of the PID
will most likely result in a retake of the radiograph.
CHAPTER 17 • THE OCCLUSAL EXAMINATION 219
TABLE 17-1 Recommended Vertical Angulation
Settings for Occlusal Radiographs
OCCLUSAL
RADIOGRAPH VERTICAL ANGLE SETTING*
Maxillary topographical
(anterior)
+65°
Maxillary topographical
(posterior)
+45°
Mandibular topographical
(anterior)
-55°
Mandibular topographical
(posterior)
-45°
Mandibular cross-sectional 0°**
The patient must be seated in the correct position, with the occlusal
plane of the arch being imaged parallel to the floor and the midsaggital
plane perpendicular to the floor.
The patient must be seated in the correct position, with the occlusal
plane of the mandible perpendicular to the floor and the midsaggital
plane parallel to the floor.
**
*
TABLE 17-2 A Summary of Occlusal Radiographic Technique
OCCLUSAL
RADIOGRAPH PLACEMENT VERTICAL ANGULATION*
HORIZONTAL
ANGULATION POINT OF ENTRY*
Maxillary topographical
(anterior) (Figure 17-4)
Long dimension across the
mouth (buccal-to-buccal).
White unprinted film side
toward the maxillary
teeth.
Perpendicular to the imaginary
bisector between the long
axes of the teeth and image
receptor in the vertical
dimension, +65°.
Perpendicular to the
image receptor
through the maxillary central incisor
embrasure.
Through a point near the
bridge of the nose
toward the center of
the image receptor
Maxillary topographical
(posterior) (Figure 17-5)
Long dimension along the
midline (front-to-back).
White unprinted film
side toward the
maxillary teeth.
Perpendicular to the imaginary
bisector between the long
axes of the teeth and the
image receptor in the vertical
dimension, +45°.
Perpendicular to the
image receptor
through the
maxillary posterior
embrasures.
Through a point on the
ala–tragus line below
the outer cantus of the
eye (see Figure 15-7)
toward the center of
the image receptor
Mandibular topographical
(anterior) (Figure 17-6)
Long dimension across
the mouth (buccal-tobuccal). White unprinted
film side toward the
mandibular teeth.
Perpendicular to the imaginary
bisector between the long
axes of the teeth and the
image receptor in the vertical
dimension, -55°.
Perpendicular to the
image receptor
through the
mandibular central
incisor embrasure.
Through a point on the
middle of the chin
toward the center of
the image receptor
Mandibular topographical
(posterior) (Figure 17-7)
Long dimension along the
midline (front-to-back).
White unprinted film
side toward the
mandibular teeth.
Perpendicular to the imaginary
bisector between the long
axes of the teeth and the
image receptor in the vertical
dimension, -45°
Perpendicular to the
image receptor
through the
mandibular posterior
embrasures.
Through a point on the
inferior border of the
mandible directly
below the second
mandibular premolar
toward the center of
the image receptor
Mandibular cross-sectional
(Figure 17-8)
Long dimension across the
mouth (buccal-tobuccal). White unprinted
side toward the
mandibular teeth.
Perpendicular to the image
receptor; 0°.**
Align the open end of
the PID parallel to
the plane of the
image receptor
Through a point 2 in.
(5 cm) back from the
tip of the chin toward
the center of the
image receptor**
The patient must be seated in the correct position, with the occlusal plane of the arch being imaged parallel to the floor and the midsaggital plane
perpendicular to the floor.
The patient must be seated in the correct position, with the occlusal plane of the mandible perpendicular to the floor and the midsaggital plane
parallel to the floor.
**
*
The Occlusal Examination
Figures 17-4 through 17-8 illustrate the image receptor positions and required angulations for each of the topographical
and cross-sectional occlusal radiographs discussed in this
chapter. See Table 17-2 for a summary of the technique.
220 INTRAORAL TECHNIQUES
PID
65°
Tube head
A B
C
OCCLUSAL TECHNIQUE
Maxillary Topographical Occlusal Radiograph (Anterior)
FIGURE 17-4 Maxillary topographical occlusal radiograph (anterior). (A) Diagram showing relationship of tube head and PID to image
receptor and patient. Exposure side of the image receptor faces the maxillary arch with longer dimension buccal-to-buccal (across the arch). The
central ray is directed perpendicular in the horizontal dimension to the patient’s midsagittal plane through the maxillary central incisor embrasure.
The vertical angulation is directed approximately through a point near the bridge of the nose toward the center of the image receptor.
(B) Patient showing position of image receptor and 8-in. (20.5-cm) circular PID. (C) Anterior maxillary topographical occlusal radiograph.
+65°
CHAPTER 17 • THE OCCLUSAL EXAMINATION 221
OCCLUSAL TECHNIQUE
Maxillary Topographical Occlusal Radiograph (Posterior)
C
A B
PID
45°
Tube head
FIGURE 17-5 Maxillary topographical occlusal radiograph (posterior). (A) Diagram showing relationship of tube head and PID to
image receptor and patient. The image receptor is positioned over the left or right side, depending on the area of interest. Exposure side of the
image receptor faces the maxillary arch with longer dimension along the midline (anterior-to-posterior). The central ray is directed perpendicular
in the horizontal dimension to patient’s midsagittal plane through the maxillary posterior embrasures. The vertical angulation is directed
approximately through a point on the ala–tragus line below the outer canthus of the eye toward the center of the image receptor.
(B) Patient showing position of image receptor and 8-in. (20.5-cm) circular PID. (C) Posterior maxillary topographical occlusal radiograph.
+45°
OCCLUSAL TECHNIQUE
Mandibular Topographical Occlusal Radiograph (Anterior)
C
B
−55°
PID
Tube head
A
FIGURE 17-6 Mandibular topographical occlusal radiograph (anterior). (A) Diagram showing relationship of tube head and PID to
image receptor and patient. Exposure side of the image receptor faces the mandibular arch with longer dimension buccal-to-buccal (across the
arch). The central ray is directed perpendicular in the horizontal dimension to patient’s midsaggittal plane through the mandibular central incisor
embrasure. The vertical angulation is directed approximately through a point in the middle of the chin toward the center of the image
receptor. (B) Patient showing position of image receptor and 8-in. (20.5-cm) circular PID. (C) Anterior mandibular topographical occlusal
radiograph.
-55°
222 INTRAORAL TECHNIQUES
CHAPTER 17 • THE OCCLUSAL EXAMINATION 223
OCCLUSAL TECHNIQUE
Mandibular Topographical Occlusal Radiograph (Posterior)
C
A B
PID
−45°
Tube head
FIGURE 17-7 Mandibular topographical occlusal radiograph (posterior). (A) Diagram showing relationship of tube head and PID to
image receptor and patient. The image receptor is positioned over the left or right side, depending on the area of interest. Exposure side of the
image receptor faces the mandibular arch with longer dimension along the midline (anterior-to-posterior). The central ray is directed
perpendicular in the horizontal dimension to patient’s midsagittal plane through the mandibular posterior embrasures. The vertical angulation is
directed approximately through a point on the inferior border of the mandible directly below the second mandibular premolar toward the
center of the image receptor. (B) Patient showing position of image receptor and 8-in. (20.5-cm) circular PID. (C) Posterior mandibular
topographical occlusal radiograph.
-45°
224 INTRAORAL TECHNIQUES
OCCLUSAL TECHNIQUE
Mandibular Cross-Sectional Occlusal Radiograph
A B
PID
Tube head
C
FIGURE 17-8 Mandibular cross-sectional occlusal radiograph. (A) Diagram showing relationship of tube head and PID to image receptor
and patient. The exposure side of the image receptor faces the mandibular arch with the longer dimension buccal-to-buccal (across the arch). The
central ray is directed perpendicular in both the horizontal and vertical dimensions toward the image receptor. Positioning the open end of the PID
parallel to the image receptor achieves the required perpendicular alignment. The vertical angulation is directed approximately 0º through a point
2 in. (5 cm) back from the tip of the chin toward the center of the image receptor. (B) Patient showing position of image receptor and 8-in.
(20.5-cm) circular PID. (C) Mandibular cross-sectional occlusal radiograph.
CHAPTER 17 • THE OCCLUSAL EXAMINATION 225
REVIEW—Chapter summary
The purpose of occlusal radiographs is to image a larger area than
that produced on a periapical radiograph. The topographical
occlusal teachnique is based on a modification of the bisecting
technique used to expose periapical radiographs. The x-ray beam is
directed perpendicularly toward the image receptor in both the horizontal and vertical dimensions when exposing a cross-sectional
occlusal radiograph. Occlusal radiographs are used to view conditions of the teeth and supporting structures such as impactions,
large apical lesions, calcifications in soft tissue, and fractures.
Size #4 image receptor is used for adult examinations. If
indicated, a size #2 or smaller image receptor may be used with
the occlusal technique, especially for children. An image receptor holder is not required; the patient lightly bites down on the
image receptor to hold it in place. The image receptor may be
positioned with the long dimension horizontal or vertical with
at least 1/4 in. (1/2 cm) protruding outside the mouth.
The patient’s head should be positioned with the occlusal
plane parallel and the midsaggital plane perpendicular to the
floor when exposing maxillary and mandibular topographical
occlusal radiographs. The patient’s head should be tipped back
into a position with the occlusal plane perpendicular to the plane
of the floor and the midsaggital plane parallel to the floor when
exposing a mandibular cross-sectional occlusal radiograph.
The horizontal angulation used to produce a topographical
occlusal radiograph is determined in the same manner as for
periapical and bitewing radiographs, where the central rays of
the x-ray beam are directed perpendicularly to the image receptor through the embrasures of the teeth of interest. Aligning the
open end of the PID parallel to the image receptor will assist in
determining the correct horizontal angulation to produce a
cross-sectional occlusal radiograph. The vertical angulation used
to produce a topographical occlusal radiograph is determined in a
similar manner to the bisecting technique used to produce periapical radiographs, where the central rays of the x-ray beam are
directed perpendicularly to the bisector between the long axes of
the teeth and the plane of the image receptor. Determining the vertical angulation for exposure of a cross-sectional occlusal radiograph is assisted by positioning the open end of the PID parallel
to the plane of the image receptor. Correct points of entry position
are determined by directing the central rays of the x-ray beam at
the center of the image receptor. If the patient’s head is in correct
position, predetermined vertical angulations and points of the
entry may be used. Step-by-step illustrated instructions for exposing five of the most common occlusal radiographs are presented
RECALL—Study questions
1. Each of the following is an indication for exposing
occlusal radiographs EXCEPT one. Which one is the
EXCEPTION?
a. Evaluate periodontal disease
b. Examine sinus borders
c. Locate foreign bodies
d. Reveal sialoliths
2. Which of the following will a mandibular cross-sectional
occlusal radiograph best image?
a. Cleft palate
b. Fractured jaw
c. Large periapical cyst
d. Sublingual swelling
3. Which of these sizes is known as the occlusal image
receptor?
a. #1
b. #2
c. #3
d. #4
4. The image receptor should be placed with the long
dimension along the midline (front to back) for which
of these occlusal radiographs?
a. Maxillary topographical anterior
b. Maxillary topographical posterior
c. Mandibular topographical anterior
d. Mandibular cross-sectional
5. Where should the embossed dot be positioned when
placing an occlusal film packet intraorally?
a. Toward the apical
b. Toward the occlusal
c. Toward the anterior
d. Toward the posterior
6. The ideal patient head position when exposing a maxillary topographical occlusal radiograph is to position
the occlusal plane ______________ to the plane of
the floor and the midsaggital plane ______________
to the plane of the floor.
a. parallel; perpendicular
b. perpendicular; parallel
c. parallel; parallel
d. perpendicular; perpendicular
7. The ideal patient head position when exposing a
mandibular cross-sectional occlusal radiograph is to
position the head rest so that the chin is tipped
______________ and the occlusal plane is ________
______ to the plane of the floor.
a. down; perpendicular
b. up; perpendicular
c. down; parallel
d. up; parallel
8. Assuming that the patient’s head is in the correct position, which of the following is the correct vertical angulation setting for a maxillary anterior topographical
occlusal radiograph?
a.
b.
c. 0 degrees
d. -55 degrees
+45 degrees
+65 degrees
226 INTRAORAL TECHNIQUES
9. Assuming that the patient’s head is in the correct
position, which of the following is the correct vertical
angulation setting for a mandibular cross-sectional
occlusal radiograph?
a.
b.
c. 0 degrees
d.
10. What is the point of entry for correctly exposing a
posterior mandible topographical occlusal radiograph?
a. The middle of the chin
b. A point 2 in. (5 cm) back from the tip of the chin
c. A point on the ala–tragus line below the outer cantus
of the eye
d. A point on the inferior border of the mandible directly
below the second mandibular premolar
REFLECT—Case study
Consider the following cases. After determining the radiographic assessment for each of these three cases, write out a
detailed procedure chart that a radiographer can follow to
obtain the needed radiographs. Begin with patient positioning.
Be sure to include the steps for determining the correct placement of the image receptor, x-ray beam angles, and landmarks
for determining points of entry.
1. An adult patient presents with a sublingual swelling
indicating the possibility of a blocked salivary gland.
What type of occlusal radiograph will this patient most
likely be assessed for?
-55 degrees
+45 degrees
+65 degrees
2. An adult patient presents with severe pain in the
mandibular left posterior region, indicating the possibility
of an impacted third molar. The pain and swelling in this
region is preventing the patient from opening more than a
few millimeters. What type of occlusal radiograph will
this patient most likely be assessed for?
3. A child patient presents with trauma to the maxillary
anterior teeth after a fall off her bicycle. What type of
occlusal radiograph will this patient most likely be
assessed for?
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this
topic, see Thomson, E. M. (2012). Exercises in oral radiography techniques: A laboratory manual (3rd ed.). Upper
Saddle River, NJ: Pearson Education. Chapter 10 “Occlusal
Radiographic Technique.”
REFERENCES
Carroll, M. K. (1993). Advanced oral radiographic techniques: Part I, occlusal and lateral oblique projections
(videorecording). Jackson, MS: Health Sciences Consortium, Learning Resources, University of Mississippi
Medical Center.
Eastman Kodak Company. (2002). Successful intraoral radiography. Rochester, NY: Author.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Recognize errors caused by incorrect radiographic techniques.
3. Apply the appropriate corrective actions for technique errors.
4. Recognize errors caused by incorrect radiographic processing.
5. Apply the appropriate corrective actions for processing errors.
6. Recognize errors caused by incorrect radiographic image receptor handling.
7. Apply the appropriate corrective actions for handling errors.
8. Identify five causes of film fog.
9. Apply the appropriate actions for preventing film fog.
KEY WORDS
Artifacts
Conecut error
Dead pixel
Distomesial overlap
Double exposure
Electronic noise
Elongation
Film fog
Foreshortening
Herringbone error
Mesiodistal overlap
Overdevelopment
Overexposure
Overlapping
Static electricity
Underdevelopment
Underexposure
Identifying and Correcting
Undiagnostic Radiographs
PART VI • RADIOGRAPHIC ERRORS
AND QUALITY ASSURANCE
CHAPTER
18
CHAPTER
OUTLINE
 Objectives 227
 Key Words 227
 Introduction 228
 Recognizing
Radiographic
Errors 228
 Technique Errors 229
 Processing
Errors 235
 Handling Errors 236
 Fogged Images 237
 Review, Recall,
Reflect, Relate 238
 References 240
228 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
Introduction
Although radiographs play an important role in oral health
care, it should be remembered that exposure to radiation carries a risk. The radiographer has an ethical responsibility to
the patient to produce the highest diagnostic quality radiographs, in return for the patient’s consent to undergo the
radiographic examination. Less-than-ideal radiographic
images diminish the usefulness of the radiograph. When the
error is significant, a radiograph will have to be retaken. In
addition to increasing the patient’s radiation exposure, retake
radiographs require additional patient consent and may
reduce the patient’s confidence in the operator and in the
practice.
No radiograph should be retaken until a thorough
investigation reveals the exact cause of the error and
the appropriate corrective action is identified and can
be implemented.
It is important that the radiographer develop the skills
needed to identify radiographic errors. Identifying common
mistakes and knowing the causes will help the knowledgeable operator avoid these pitfalls. Being able to identify the
cause of an undiagnostic image will allow the radiographer
to apply the appropriate corrective action for retaking the
exposure.
The purpose of this chapter is to investigate common radiographic errors, identify probable causes of such errors, and
present the appropriate corrective actions.
Recognizing Radiographic Errors
To recognize errors that diminish the diagnostic quality of a
radiograph, the radiographer must understand what a quality
image looks like (Table 18-1). First and foremost, the radiograph must be an accurate representation of the teeth and
the supporting structures. The image should not be magnified,
elongated, foreshortened, or otherwise distorted. Image density
and contrast should be correct for ease of interpretation: not
too light, or too dark, or fogged. The radiograph should be
free of errors.
PRACTICE POINT
All errors reduce the quality of the radiograph. However, not
all errors create a need to re-expose the patient. Two examples of this are when the error does not affect the area of
interest and when the error affects only one image in a series
(bitewings or full mouth), where the area of interest can be
viewed in an adjacent radiograph. For example, a radiograph
may have a conecut error, cutting off part of the image. If
the conecut error does not affect the area of interest, a
retake would not be required. Consider this situation, where
a periapical radiograph is exposed to image a suspected apical pathology in the posterior region. If the conecut error
occurs in the anterior portion, cutting off the second premolar, but an abscess at the root apex of the first molar is adequately imaged, the radiograph would most likely not have
to be retaken.
When exposing a set of radiographs such as a vertical
bitewing or full mouth series, if an error prevents adequate
imaging of a condition, adjacent radiographs should be
observed for the possibility that the condition may be adequately revealed in another image. For example, if one radiograph in a set of bitewings is overlapped, it should be
determined if the adjacent radiograph images the area adequately. If so, a retake would most likely not be indicated.
Determining when a retake is absolutely necessary will keep
radiation exposure to a minimum.
Recognizing the cause of radiographic errors is important
in being able to take corrective action. Errors that diminish the
diagnostic quality of radiographs may be divided into three
categories:
1. Technique errors
2. Processing errors
3. Handling errors
TABLE 18-1 Characteristics of a Quality Radiograph
BITEWING RADIOGRAPH PERIAPICAL RADIOGRAPH
• Image receptor placed correctly to record area of interest • Image receptor placed correctly to record area of interest
• Equal portion of the maxilla and mandible
recorded
• Entire tooth plus at least 2 mm beyond the incisal/occlusal
edges of the crowns and beyond the root apex recorded
• Occlusal/incisal plane of the teeth is parallel to the edge of
the image receptor
• Occlusal/incisal plane of the teeth is parallel with the edge of
the image receptor
• Occlusal plane straight or slightly curved upward toward
the posterior
• Embossed dot positioned toward the incisal/occlusal
edge
• Most posterior contact point between adjacent teeth
recorded
• In a full mouth survey, each tooth should be recorded at least
once, preferably twice
CHAPTER 18 • IDENTIFYING AND CORRECTING UNDIAGNOSTIC RADIOGRAPHS 229
NOT RECORDING POSTERIOR STRUCTURES
• Probable causes: The image receptor was placed too far
forward in the patient’s oral cavity. The beginning radiographer is sometimes hesitant about placing the image
receptor far enough posterior to record diagnostic information about the third molar region. This is especially true
when the patient presents with a small oral cavity or a
hypersensitive gag reflex.
• Corrective actions: Communicate with the patient to gain
acceptance and assistance with placing the image receptor. Use tips for working with an exaggerated gag reflex.
(See Chapter 27.)
NOT RECORDING APICAL STRUCTURES (FIGURE 18-2)
• Probable causes:
1. Image receptor was not placed high enough (maxillary)
or low enough (mandibular) in the patient’s oral cavity to
image the root apices. This often occurs when the patient
does not occlude completely and securely on the image
receptor holder biteblock or tab.
2. Inadequate (not steep enough) vertical angulation will
result in less of the apical region being recorded onto
the radiograph.
• Corrective actions:
1. Ensure that the image receptor is positioned correctly
into the holding device and that the patient is biting
down all the way. Tip the image receptor in toward the
middle of the oral cavity where the midline of the
palatal vault is the highest to facilitate the patient biting
all the way down on the holder biteblock. When placing
the image receptor on the mandible, using an index finger, gently massage the sublingual area to relax and
move the tongue out of the way while positioning the
image receptor low enough to record the mandibular
teeth root apices.
2. Increase vertical angulation. If correctly directing the
central rays perpendicular to the image receptor when
using the paralleling technique (see Chapter 14) and
perpendicular to the imaginary bisector when using the
bisecting technique (see Chapter 15) does not record
enough apical structures, increase the vertical angulation slightly. An increase of no greater than 15 degrees
will still produce an acceptable radiographic image.
NOT RECORDING CORONAL STRUCTURES (FIGURE 18-3)
• Probable causes: Because this error appears to be the
opposite of not recording the apical structures, it would
seem logical to assume that the image receptor was placed
too high (maxillary) or too low (mandibular) in the
patient’s oral cavity to image the entire crowns of these
teeth. However, the use of image receptor holders will
almost always eliminate this error. When noted, the cause
is more often the result of excessive vertical angulation.
premolar
Image receptor
FIGURE 18-1 Tip for positioning the image receptor for
exposure of a premolar radiograph. Positioning the anterior edge
of the image receptor against the canine on the opposite side places
the image receptor into the correct anterior position.
It is important to note that errors in any of these categories
may produce the same or a similar result. For example, it is
possible that a dark radiographic image may have been caused
by overexposure (a technique error) or by overdevelopment (a
processing error), or by exposing the film to white light (a handling error). For the purpose of defining the more common
radiographic errors, we will discuss the errors according to
these three categories.
Technique Errors
Technique errors include mistakes made in placement of the image
receptor, positioning of the PID (vertical and horizontal angulations), and setting exposure factors. Additional technical problems
include movement of the patient, the image receptor, or the PID.
Incorrect Positioning of the Image Receptor
The most basic technique error is not imaging the correct teeth.
The radiographer must know the standard image receptor
placements for all types of projections and must possess the
skills necessary to achieve these correct placements.
NOT RECORDING ANTERIOR STRUCTURES
• Probable causes: The image receptor was placed too far
back in the patient’s oral cavity. Due to the curvature and
narrowing of the arches in the anterior region, it is sometimes difficult to place the image receptor far enough anterior without impinging on sensitive mucosa. This is
especially likely when tori are present. When using a digital sensor, the wire and/or plastic barrier may further compromise fitting the image receptor into the correct position.
• Corrective actions: To avoid placing a corner of the image
receptor uncomfortably in contact with the soft tissues lingual to the canine, position the receptor in toward the midline of the oral cavity, away from the lingual surfaces of
the teeth of interest. When positioning the image receptor
for a premolar radiograph, the anterior edge of the receptor
may be positioned to contact the canine on the opposite
side to achieve the correct position (Figure 18-1).
230 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
SLANTING OR TILTED INSTEAD OF STRAIGHT OCCLUSAL
PLANE (FIGURE 18-4)
• Probable causes: The edge of the image receptor was not
parallel with the incisal or occlusal plane of the teeth, or
the image receptor holder was not placed flush against the
occlusal surfaces. This error often results when the top
edge of the image receptor contacts the lingual gingiva or
the curvature of the palate; and when the image receptor is
placed on top of the tongue.
• Corrective actions: Straighten the image receptor by positioning away from the lingual surfaces of the teeth. Place the
image receptor in toward the midline of the palate. Utilize this
highest region of the palatal vault to stand the image receptor up parallel to the long axes of the teeth. For mandibular
1
2
FIGURE 18-3 Radiograph of mandibular molar area.
(1) Not recording the entire occlusal structures most likely
resulted from excessive (too steep) vertical angulation.
(2) Note the radiolucent artifact (horizontal line) that resulted
from bending the image receptor, in this case a film packet.
• Corrective actions: Decrease vertical angulation. If correctly
directing the central rays perpendicular to the image receptor
when using the paralleling technique (see Chapter 14) and
perpendicular to the imaginary bisector when using the
bisecting technique (see Chapter 15) does not record enough
coronal structures, decrease the vertical angulation slightly.
A decrease of no greater than 15 degrees will still produce an
acceptable radiographic image.
PRACTICE POINT
The misuse of a cotton roll to help stabilize the image receptor holder is often the cause of the root tips being cut off the
resultant radiographic image. A cotton roll is sometimes utilized to help the patient bite down on the holder’s biteblock
to secure it in place (see Chapter 14). This practice is appropriate when used correctly. Correct placement of the cotton
roll is on the opposite side of the biteblock from where the
teeth occlude. Placing the cotton roll on the same side as the
teeth will prevent the image receptor from being placed high
enough (maxillary) or low enough (mandibular) in the mouth.
1
2
3
FIGURE 18-2 Radiograph of maxillary molar area. Not recording the apical structures most likely resulted from a combination
of not placing the image receptor correctly and inadequate vertical angulation. (1) The patient did not occlude completely and securing
on the image receptor biteblock causing the image receptor to be placed too low in the mouth. (2) Inadequate (not steep enough) vertical
angulation resulted in not recording the apical structures and a stretching out of the image called elongation. (3) Overlapped contacts
results from incorrect horizontal angulation. In this example, the overlapping is more severe in the anterior (mesial) region and less severe
in the posterior (distal) region, indicating distomesial projection of the x-ray beam toward the image receptor.
CHAPTER 18 • IDENTIFYING AND CORRECTING UNDIAGNOSTIC RADIOGRAPHS 231
1
2
3 4
5
6
7
FIGURE 18-4 Radiograph of maxillary canine area. (1) Slanting
or diagonal occlusal plane caused by incorrect position of the image
receptor. (2) Foreshortened images caused by a combination of
excessive vertical angulation and incorrect image receptor position.
(3) Distortion caused by bending the image receptor. (4) Maxillary
sinus, (5) recent extraction site, (6) lamina dura, and (7) image of the
canine is distorted.
FIGURE 18-5 Reversed film packet error. These embossed patterns will be recorded on the image when the
lead foil faces the x-ray beam. Note the different patterns depending on the manufacturer and the film size.
FIGURE 18-6 Incorrect reversed film packet. An examination
through the ring of this image receptor holder assembly reveals that
the back of the film packet will be positioned incorrectly toward the
teeth and the x-ray source.
placements, slide the image receptor in between the lingual
gingiva and the lateral surface of the tongue. Ensure that the
patient is biting down securely on the biteblock of the holder.
REVERSED IMAGE ERROR (HERRINGBONE ERROR)
• Probable causes: The image receptor film packet was positioned so that the back side was facing the teeth and the radiation source. The first thing that the radiographer will notice
is that the radiograph will be significantly underexposed
(too light). However, when placed on a view box and examined closely, a pattern representing the embossed lead foil
that is in the back of a film packet can be detected. Historically film makers used a herringbone pattern, and therefore
some practitioners still call this herringbone error. Most
films currently available have a pattern resembling a tire
track or diamond pattern (Figure 18-5).
• Corrective actions: Determine the front side of the film
packet prior to placing into the image receptor holder.
When in doubt, read the printed side of the film packet
for direction. Once attached, examine the film and holder
assembly to ensure that the tube side faces toward the
teeth and the radiation source (Figure 18-6). Due to the
composition of phosphor plates and digital sensors, positioning the incorrect side of these image receptors
toward the radiation source will result in failure to produce an image.
INCORRECT POSITION OF FILM IDENTIFICATION DOT
• Probable cause: Embossed identification dot positioned in
apical area where it can interfere with diagnosis.
• Corrective actions: Pay attention when placing the film
packet into the film holding device to position the dot
toward the incisal or occlusal region, where it is less likely
to interfere with interpretation of the image. Some practitioners use the phrase “dot in the slot” to remind them to
place the edge of the film packet where the dot is located
into the slot of the film holding device. Placing the dot in
the slot of a film holder will automatically position the dot
toward the occlusal or incisal edges of the teeth and away
from the apical regions.
232 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
CONECUT ERROR (FIGURES 18-7 AND 18-8)
• Probable causes: The primary beam of radiation was not
directed toward the center of the image receptor and did
not completely expose the entire surface area of the receptor. Image receptor holders with external aiming rings help
prevent this error. However, assembling the image receptor
holding instrument incorrectly will cause the operator to
direct the central ray of the x-ray beam to the wrong place,
resulting in conecut error.
Incorrect Positioning of the Tube Head and PID
Included in this category are the errors that result from incorrect
vertical and horizontal angulations and centering of the x-ray
beam over the image receptor. We have already discussed that
incorrect vertical angulation can result in not recording the
apices or the occlusal/incisal edges of the teeth. Elongation
(images that appear stretched out) and foreshortening (images
that appear shorter than they are), with or without cutting off the
apices or the occlusal/incisal edges of the teeth, are dimensional
errors that result from incorrect vertical angulation when using
the bisecting technique. It is important to remember that it is
impossible to create images that are elongated or foreshortened
when the image receptor is positioned parallel to the teeth, as is
the case when using the paralleling technique. If elongation or
foreshortening errors result, it is important that the corrective
action be to first try to position the image receptor parallel to the
teeth of interest. Correctly positioning the image receptor parallel to the teeth will most likely prevent dimensional errors. If
parallel placement of the image receptor to the teeth is not possible, then the bisecting technique must be carefully applied to
avoid elongation and foreshortening of the image.
ELONGATION/FORESHORTENING
OF THE IMAGE (BISECTING TECHNIQUE ERROR)
• Probable causes: Insufficient vertical angulation
with the PID not positioned steep enough away from zero
degrees results in elongation (Figure 18-2). Excessive
vertical angulation with the PID positioned too steep
enough away from zero degrees results in foreshortening
(Figure 18-4).
• Corrective actions: To correct elongation, increase the
vertical angulation. To correct foreshortening, decrease the
vertical angulation. Direct the central rays perpendicular
to the imaginary bisector between the long axes of the teeth
and the plane of the image receptor (see Chapter 15).
If relying on predetermined vertical angulation settings,
check the position of the patient’s head to ensure that the
occlusal plane is parallel and that the midsaggital plane is
perpendicular to the floor.
OVERLAPPED TEETH CONTACTS (FIGURE 18-2)
• Probable causes:
1. Incorrect rotation of the tube head and PID in the horizontal plane. Superimposition of the proximal surfaces
occurs when the central ray of the x-ray beam is not
directed perpendicular through the interproximal spaces
to the image receptor. Overlapped contacts result when
the central ray of the x-ray beam is directed obliquely
toward the image receptor from the distal or from the
mesial. When the angle of the x-ray beam is directed
obliquely from mesial to distal (mesiodistal overlap), the
overlapping contacts are more severe in the posterior
part of the image. Conversely, when the angle of the x-ray
beam is directed obliquely from distal to mesial
(distomesial overlap), the overlapping contacts are more
severe in the anterior part of the image.
2. Not positioning the image receptor parallel to the interproximal spaces of the teeth of interest will prevent the
central ray of the x-ray beam from being directed perpendicular through the contacts and perpendicular to
the image receptor.
• Corrective actions:
1. Examine the image to determine where the overlap is
most severe. To correct mesiodistal overlap, rotate the
tubehead and PID to a more distomesial angle. Physically move the tubehead toward the posterior of the
patient while rotating the PID toward the anterior so
that the central ray of the x-ray beam will enter the
patient from the distal (or posterior). To correct distomesial overlap, rotate the tubehead and PID to a more
mesiodistal angle. Physically move the tubehead toward
the anterior of the patient while rotating the PID toward
the posterior so that the central ray of the x-ray beam
will enter the patient from the mesial (or anterior.). It
should be noted that there are cases when mesiodistal
and distomesial overlap cannot be distinguished from
one another. When this happens, closely examine the
teeth of interest to determine the precise contact points
through which to perpendicularly direct the central rays
of the x-ray beam.
2. Examine the teeth of interest to determine the contact
points prior to positioning the image receptor. Place
the image receptor parallel to the contact points of
interest so that the central rays of the x-ray beam will
intersect the image receptor perpendicularly through
those contacts (see Figure 28-2).
PRACTICE POINT
Use the phrase “Move toward it to fix it” when correcting
mesiodistal or distomesial overlap error. If the overlapping
appears more severe in the posterior region (mesiodistal overlap), shift the tube head toward the posterior while rotating
the PID to direct the x-ray beam from the distal. If the overlapping appears more severe in the anterior region (distomesial
overlap), shift the tube head toward the anterior while rotating the PID to direct the x-ray beam from the mesial.
CHAPTER 18 • IDENTIFYING AND CORRECTING UNDIAGNOSTIC RADIOGRAPHS 233
• Corrective actions: While maintaining correct horizontal
and vertical angulation, move the tube head up, down, posteriorly, or anteriorly, depending on which area of the
radiograph shows a clear, unexposed region. Check to see
that the image receptor holder is assembled correctly, and
direct the central ray of the x-ray beam to the center
(middle) of the receptor.
Incorrect Exposure Factors
Insufficient knowledge regarding the use of the control panel
settings and exposure button will result in less-than-ideal radiographic images.
LIGHT (THIN)/DARK IMAGES (FIGURES 18-9 AND 18-10)
• Probable causes: It has already been pointed out that underexposed images result when a film packet is positioned
reversed, or backward, in the oral cavity. The presence of an
FIGURE 18-7 Conecut error. Results when the central ray of the
x-ray beam is not directed toward the middle of the image receptor.
The white (clear) circular area was beyond the range of the x-ray
beam, and therefore received no exposure. This radiograph illustrates
conecut error that resulted from incorrect assembly of a posterior
image receptor holder.
FIGURE 18-8 Conecut error. Can also occur when using
rectangular collimation.
FIGURE 18-9 Light (thin) image. Underexposed or underdeveloped
radiograph.
FIGURE 18-10 Dark image. Overexposed or overdeveloped
radiograph.
embossed pattern or herringbone error will indicate why the
underexposure occurred. If a pattern is not noted in a light
image, an error with the selection of exposure factors should
be suspected. Insufficient exposure time in relation to milliamperage, kilovoltage, and PID length selected by the operator all result in light images, whereas excessive exposure
time in relation to these parameters results in overexposure.
Inappropriately exposing a phosphor plate to bright light
prior to the laser processing step will result in a light or faded
image. Under- or overexposure may rarely occur as a result
of equipment malfunction. Light/dark images that result
from processing errors will be discussed later in this chapter.
• Corrective actions: An exposure chart posted near the control panel for easy reference can assist with preventing
incorrect exposures. Increasing the exposure time, the milliamperage, the kilovoltage, or a combination of these factors will correct underexposures, whereas decreasing these
parameters will correct overexposures. If the PID length is
switched, then a cooresponding adjustment in the exposure
time must be made. Exposed phosphor plates should be
placed with the front side down on the counter or within a
containment box until ready for the laser processing step.
(see Chapter 9) The exposure button must be depressed for
234 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
• Corrective actions: Perform a cursory examination of the
oral cavity to check for the presence of appliances. Ask
the patient to remove any objects that may be in the path
of the primary beam. Ensure that the lead/lead equivalent
apron and thyroid collar do not block the x-rays from
reaching the image receptor.
the full cycle. The operator must watch for the red exposure
light and the audible signal to end to indicate that the exposure button may be released. If the problem persists, check
the accuracy of the timer or switch for possible malfunction.
CLEAR OR BLANK IMAGE
• Probable causes: No exposure to x-rays, that results
from failure to turn on the line switch to the x-ray
machine or to maintain firm pressure on the exposure
button during the exposure or, if using digital imaging,
exposing the back side of a phosphor plate or digital sensor. Alternate causes: electrical failure, malfunction of
the x-ray machine or processing errors (which will be
discussed later).
• Corrective actions: Turn on the x-ray machine and maintain
firm pressure on the exposure button during the entire exposure period. Watch for the red exposure light and listen for
the audible signal indicating that the exposure has occurred.
Be familiar with digital image receptors to determine the
correct exposure side.
DOUBLE IMAGE
• Probable cause: Double exposure resulting from accidentally exposing the same film or phosphor plate twice.
• Corrective actions: Maintain a systematic order to exposing
radiographs. Keep unexposed and exposed image receptors
organized.
Miscellaneous Errors in Exposure Technique
POOR DEFINITION
• Probable causes: Movement caused by the patient, slippage of the image receptor, or vibration of the tube head.
• Corrective actions: Place the patient’s head into position
against the head rest of the treatment chair and ask him/her
to hold still throughout the duration of the exposure.
Explain the procedure and gain the patient’s cooperation,
to maintain steady pressure on the image receptor holder
and not to move. Do not use the patient’s finger to stabilize
the image receptor in the oral cavity. Steady the tube head
before activating the exposure.
ARTIFACTS Artifacts are images other than anatomy or pathology that do not contribute to a diagnosis of the patient’s condition (Figures 18-11 and 18-12). Artifacts may be radiopaque or
radiolucent.
• Probable causes: The presence of foreign objects in the
oral cavity during exposure (e.g., appliances such as
removable bridges, partial or full dentures, orthodontic
retainers, patient glasses, and facial jewelry used in
piercings). There may be occasions when the lead/
lead equivalent thyroid collar could be in the path of the
x-ray beam. These metal objects will result in radiopaque
artifacts.
FIGURE 18-11 Radiopaque artifact. Partial denture left in place
during exposure.
FIGURE 18-12 Radiopaque artifact. Lead thyroid collar got
in the way of the primary beam during exposure.
CHAPTER 18 • IDENTIFYING AND CORRECTING UNDIAGNOSTIC RADIOGRAPHS 235
Processing Errors
Processing errors that result in retake radiographs also increase
patient radiation dose, add time to a busy day’s schedule, and
waste money. Processing errors occur with both manual and automatic processing. Processing errors include under- and overdevelopment, incorrectly following protocols, and failure to maintain an
ideal darkroom setting.
Development Error
LIGHT/DARK IMAGE (FIGURES 18-9 AND 18-10)
• Probable causes: Underdevelopment results when a film
is not left in the developer for the required time. Overdevelopment results when a film is left in the developer too long.
The colder the developer, the longer the time required to
produce an image of ideal density, and the warmer the
developer, the less developing time required. Images may
be too light or too dark as a result of incorrectly mixing
developer from concentrate. A weak developer mix produces
light images; a strong mix produces dark images. Light
images also result when the developer solution is old, weakened, or contaminated. A low solution level in the developer
tank of an automatic processor that does not completely
cover the rollers may also produce a light image.
• Corrective actions: When processing manually, check the
temperature of the developer and consult a time–temperature
chart before beginning processing. Ensure that the automatic
processor indicates that the solutions have warmed up and
the correct timed cycle is used. If weakened or old solutions
are suspected, change the solutions. Maintain good quality
control to replenish solutions to keep them functioning at
peak conditions and at the appropriate levels in the tanks.
Processing and Darkroom Protocol Errors
BLANK/CLEAR IMAGE
• Probable causes: It has already been discussed that no exposure to x-rays will produce a blank or clear radiograph. Film
that is accidentally placed in the fixer before being placed in
the developer will also result in a blank or clear image. If
allowed to remain in warm rinse water too long the emulsion
may dissolve also resulting in a clear image.
• Corrective actions: When processing manually, and when
filling automatic processor tanks during solution changes and
cleaning procedures, the operator must have knowledge of
which tank contains the developer and which tank contains
the fixer. Labelling the tanks prevents confusion. To prevent
the emulsion from separating from the film base, promptly
remove the film at the end of the washing period.
PARTIAL IMAGE
• Probable causes: A manual processing error—when the
level of the developer is too low to cover the entire film,
the emulsion in the section of the film that remains
above the solution level will not be developed. Once in
the fixer, the emulsion in this section will be removed
leaving a blank or clear section.
• Corrective actions: Replenish the processing solutions to
the proper level or attach the films to lower clips on the
film hanger to ensure that they will be submerged completely in the solution.
GREEN FILMS
• Probable causes: When films stick together in the developer
the solution is prevented from reaching the (green) emulsion. The most common causes include failure to separate
double film packets, placing additional films into the same
intake slot of an automatic processor too close together
resulting in overlapping of the two films, and attaching two
films to one clip used in manual processing, or allowing
films on adjacent film racks to contact each other.
• Corrective actions: The operator must be skilled at separating double film packets under safelight conditions. Use
alternating intake slots or wait 10 seconds before loading
subsequent films into the automatic processor. Carefully
handle manual film hangers and clips to avoid placing
films in contact with each other.
Chemical Contamination
BLACK/WHITE SPOTS (FIGURE 18-13)
• Probable causes: Premature contact with developing
chemicals—drops of developer or fixer that splash onto the
work area may come in contact with the undeveloped film.
Developer contamination will produce black spots. Fixer
contamination will produce white spots. Excessive wetting
of phosphor plates during the disinfecting step can damage
the plate and result in a digital image with missing information in the form of white or clear spots.
• Corrective actions: Maintain a clean and orderly darkroom and work area. Consult manufacturer recommendations to properly disinfect digital image receptors.
1
2
FIGURE 18-13 Radiograph of maxillary molar area. (1) Dark
spots caused by premature contact of film surface with developer.
(2) Uneven occlusal margin resulted because the patient did not
occlude all the way down on the image receptor biteblock.
236 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
BROWN IMAGES
• Probable cause: Insufficient or improper washing. It is
important to note that films that have not been washed
completely will appear normal immediately after drying.
Films will turn brown over a period of several weeks after
processing as the chemicals that remain on the surface of
the film erode the image.
• Corrective actions: When processing manually, rinse
films in circulating water for at least 20 minutes. Always
return a film to complete the fixing and washing steps after
a wet-reading. When processing automatically, ensure that
the main water supply to the unit is turned on and that the
water bottles of closed systems are full.
STAINS
• Probable causes: Iridescent, gray, and yellow stains can
result when processing chemicals become exhausted or contaminated.
• Corrective actions: Maintain quality control with regular
replenishment and replacing of the processing solutions.
Handling Errors
The manner in which the image receptor is handled contributes
to its ability to record a diagnostic quality image. Bending the
film produces artifacts and significantly reduces the quality of
the radiographic image. Bending a phosphor plate will damage
the surface. Exposing the image receptor to conditions such as
static electricity and the potential for scratching the emulsion
will further compromise diagnostic quality.
BLACK IMAGE
• Probable cause: Film was accidentally exposed to white
light.
• Corrective actions: Turn off all light in the darkroom except
the proper safelight before unwrapping the film packet. Lock
the door or warn others not to enter. Use an “in-use” sign to
prevent others from opening the door. When using an automatic processor, ensure that the film has completely entered
the light-protected processor before turning on the white
overhead light or removing hands from the daylight loader
baffles.
BLACK PRESSURE MARKS (BENT FILM; FIGURES 18-3
AND 18-14)
• Probable cause: Bending the film or excessive pressure to
the film emulsion can cause the emulsion to crack. Accidentally bending the film often occurs when the radiographer
is placing the film packet into the image receptor holder.
Although not recommended, a corner of the film packet is
sometimes purposely bent by the radiographer to fit comfortably into position.
• Corrective actions: Use caution when loading the film
packet into the image receptor holding device. Films should
not be bent to fit the oral cavity. Instead, use a smaller-sized
film, the occlusal technique (see Chapter 17), or an extraoral procedure (see Chapter 29).
THIN BLACK LINES, STAR-BURSTS, DOTS, LIGHTENING
PATTERN (SEE FIGURE 29-6)
• Probable causes: Static electricity may be produced when
the film is pulled out of the packet wrapping too fast. Static
electricity creates a white light spark that exposes (blackens) the film.
• Corrective actions: Follow infection control protocols for
opening film packets (see Chapter 10). Reduce the occurrence of static electricity by increasing humidity in the darkroom. Use antistatic products on protective clothing to
prevent the buildup of static electricity.
WHITE LINES OR MARKS OR BLANK IMAGE (FIGURE 18-15)
• Probable causes: The film emulsion is soft and can be
easily scratched by a sharp object such as the film clip
used for manual processing or when trying to separate
double film packets. Scratching removes the emulsion
from the base. Damaged digital sensors also result in
images with missing information in areas of dead
(damaged) pixels. Damage to the digital sensor wire
attachment can result in complete failure of the device to
record an image.
• Corrective actions: Carefully handle all types of radiographic image receptors. Avoid contacting the film with
other films or hangers. Mount dried radiographs promptly
and enclose in a protective envelope. Care should be taken
to store wired digital sensors without crimping or folding
the sensitive wire attachment.
1
2
FIGURE 18-14 Radiograph of mandibular premolar area.
(1) Purposely bending the lower left film corner to make the receptor
fit the oral cavity resulted in distortion and a pressure mark (thin
radiolucent line). (2) Long radiolucent pressure mark caused by
bending or by careless handling with excessive force.
CHAPTER 18 • IDENTIFYING AND CORRECTING UNDIAGNOSTIC RADIOGRAPHS 237
SMUDGED FILM (FIGURE 18-16)
• Probable causes: Handling the film with damp fingers or
latex treatment gloves, or with residual glove powder on
the fingers will leave black smudges.
• Corrective actions: Avoid contact with the surface of the
film. Handle all radiographs carefully and by the edges only.
Hands should be clean and free of moisture or glove powder.
BLACK PAPER STUCK TO FILM
• Probable causes: A tear or break in the outer protective
wrapping of the film packet by rough handling enables
saliva to penetrate to the emulsion. Moisture softens the
emulsion, causing the black paper to stick to the film.
• Corrective actions: Careful handling prevents a break in the
seal of the film packet. Always blot excess moisture from
the film packet after removing it from the patient’s mouth.
Fogged Images
Another cause of undiagnostic radiographs is the formation of a
thin, cloudy layer that compromises the clarity of the image. This
film fog and electronic noise (digital images) diminishes contrast
and makes it difficult and often impossible to interpret the radiograph (Figure 18-17). Fogged images are produced in many ways
and can occur before, during, or after exposure or during processing
(Box 18-1). Most fogged radiographs have a similar appearance,
making it difficult to pinpoint the cause. Careful attention to the
exposure techniques and processing method used and darkroom
and image receptor handling protocols will help reduce the occurrence of fogged images.
RADIATION FOG
• Probable cause: Not properly protecting film from stray
radiation before or after exposure.
• Preventive measures: Store film in its original package at
a safe distance from the source of x-rays. Exposing a film
increases its sensitivity; therefore, it is very important that
once a film has been exposed, it should be protected from
the causes of film fog until processed.
WHITE LIGHT FOG
• Probable causes: White light leaking into the darkroom
from around doors or plumbing pipes. White light leaking
into the film packet through a tear in the outer wrapping.
1
2
FIGURE 18-15 Radiograph of maxillary posterior area.
(1) White streak marks show where the softened emulsion has been
scratched off. (2) U-shaped radiopaque band of dense bone shows the
outline of the zygoma.
FIGURE 18-16 Radiograph of primary molar area showing
fingerprint.
FIGURE 18-17 Film fog. Film fog results in lack of image
contrast.
BOX 18-1 Causes of Film Fog
• Radiation
• Light
• Heat
• Humidity
• Chemical fumes
• Aging
238 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
• Preventive measures: Check the darkroom for white light
leaks. Handle the film packet carefully to prevent tearing the
light-tight outer wrapping.
SAFELIGHT FOG
• Probable cause: A safelight will fog film if the wattage of
the safelight bulb is stronger than recommended; the distance the safelight is located over the work space area is too
close; the filter is the incorrect type or color for the film
being used; or the filter is scratched or otherwise damaged,
allowing white light through. Even when adequate, prolonged exposure to the safelight will fog film.
• Preventive measures: Perform periodic quality control
checks on the darkroom and safelight. Follow film manufacturer’s guidelines when choosing filter color. Check the
bulb wattage, check the distance away from the work space,
and examine the filter for defects. The radiographer should
develop skills necessary to open film packets aseptically
within a two- to three-minute period to minimize the time
films are exposed to the safelight.
MISCELLANEOUS LIGHT FOG
• Probable causes: Glowing light that reaches the film such
as that from watches with fluorescent faces, indicator lights
on equipment stored in the darkroom, and cells phone carried into the darkroom in a radiographer’s pocket have the
potential to create fog. This is especially true when processing sensitive extraoral films.
• Preventive measures: Watches with fluorescent faces should
not be worn in the darkroom while processing film unless
covered with the sleeve of the operator’s protective barrier
gown or lab coat. Luminous dials of equipment located in the
darkroom that glow in unsafe light colors should be masked
with opaque tape. Cell phones should be powered off to avoid
accidental illumination by an incoming call or message.
STORAGE FOG (HEAT, HUMIDITY, AND CHEMICAL FUMES)
• Probable causes: Film fog will result when film is stored
in a warm, damp area or in the vicinity of fume-producing
chemicals.
• Preventive measures: Store film unopened, in its original
package in a cool, dry area. Many practices store film in a
refrigerator until ready to use. Film should not be stored in the
darkroom unless protected from heat, humidity, and fumeproducing processing solutions.
CHEMICAL FOG
• Probable causes: Developing films too long, at too high a
temperature, or in contaminated solutions will produce
film fog.
• Preventive measures: Develop at the recommended
time–temperature cycle. Avoid contamination of processing chemicals. Always replace the manual tank cover in the
same position, with the side over the developer remaining
over the developer and the side over the fixer remaining
over the fixer to prevent contamination of the solutions.
Thoroughly rinse films to remove developer before moving
the film hanger into the fixer.
AGED FILM FOG
• Probable causes: Film emulsion has a shelf life with an expiration date (see Figure 7-9). As film ages, it can become
fogged.
• Preventive measures: Watch the date on film boxes.
Rotate film stock so that the oldest film is used before
newer film. Do not overstock film. Thoroughly research a
supplier before purchasing film, especially when buying in
bulk or from a source found on the Internet.
DIGITAL RADIOGRAPHIC NOISE
• Probable causes: Exposure settings that are extremely low.
When switching from film-based radiography to digital
imaging, there is a tendency to set the exposure factors too
low resulting in radiographic electronic noise.
• Preventive measures: Use correct exposure settings. After
setting at manufacturer’s recommendations, evaluate the
images to determine the need for varying the settings to
eliminate radiographic noise and obtain the desired image
clarity and contrast.
REVIEW—Chapter summary
The dental radiographer should know what a quality diagnostic
radiograph should look like and be able to identify when errors
occur. No radiograph should be retaken until a thorough investigation reveals the exact cause of the error and the appropriate
corrective action is identified and can be implemented. Although
radiographic errors may be classified as technique errors, processing errors, and handling errors, undiagnostic radiographs
are traceable to many causes. Different errors can often produce similar-looking results.
Technique errors include mistakes made in placement of
the image receptor, positioning the tube head and the PID, and
choosing the correct exposure factors. Processing errors
include development mistakes, not following protocols for processing and darkroom use, and chemical contamination. Handling errors include black images, and bent, scratched, damaged,
and fogged images.
Examples of probable causes and corrective actions were
given for not recording the entire tooth and supporting structures, for creating a slanted occlusal plane, for producing herringbone error, and for incorrectly positioning the embossed
identification dot. Examples of probable causes and corrective
actions were given for elongation and foreshortening, overlapping teeth contacts, and conecut error. Examples of probable
causes and corrective actions were given for light/dark,
clear/blank, and double-exposed images and images with poor
definition, the presence of artifacts such as static electricity,
black/white spots and lines, and pressure marks. Examples of
CHAPTER 18 • IDENTIFYING AND CORRECTING UNDIAGNOSTIC RADIOGRAPHS 239
probable causes and corrective actions were given for over- and
underdevelopment; partial images; and green, brown, stained,
and fogged images. Fogged radiographs result from exposure to
stray radiation, light, heat, humidity, chemical fumes, and contamination. Film has a shelf life, and aging may produce film
fog. Electronic noise, the digital equivalent of film fog, results
when radiation exposure settings are set extremely low. Measures to prevent fogged images include controlling these causes.
RECALL—Study questions
1. What is the appropriate corrective action for a periapical
radiograph of the maxillary molar region that did not
image the third molar?
a. Position the image receptor higher in the oral cavity.
b. Position the image receptor lower in the oral cavity.
c. Move the image receptor forward in the oral cavity.
d. Move the image receptor back further in the oral
cavity.
2. Each of the following will result in not recording the
apices of the maxillary premolar teeth on a periapical radiograph EXCEPT one. Which one is the EXCEPTION?
a. Image receptor not placed high enough in relation to
the teeth.
b. Image receptor not placed in toward the midline of
the palate.
c. Patient not occluding all the way down on the image
receptor holder biteblock.
d. Vertical angulation was excessive.
3. What does herringbone error indicate?
a. Embossed dot was positioned incorrectly.
b. Lead foil was processed with the film.
c. Film packet was placed in the oral cavity backwards.
d. Temperatures of the processing chemicals were not
equal.
4. When using the bisecting technique, which of these
errors results from inadequate vertical angulation?
a. Elongation
b. Foreshortening
c. Conecut
d. Overlapping
5. What error results in overlapped contacts being more
severe between the first and second molar than between
the first and second premolar?
a. Excessive vertical angulation
b. Inadequate vertical angulation
c. Mesiodistal projection of horizontal angulation
d. Distomesial projection of horizontal angulation
6. Overlapped teeth contacts renders a bitewing radiograph undiagnostic. The overlap appears more severe
in the anterior region. What corrective action is needed?
a. Increase the vertical angulation.
b. Decrease the vertical angulation.
c. Shift the horizontal angulation toward the mesial.
d. Shift the horizontal angulation toward the distal.
7. Which of these conditions results from a failure to
direct the central ray toward the middle of the image
receptor?
a. Overlapping
b. Conecut
c. Elongation
d. Foreshortening
8. Which of these indicates an overexposed radiograph?
a. Clear image
b. Light image
c. Dark image
d. Double image
9. Each of the following will result in radiographs that are
too light EXCEPT one. Which one is the EXCEPTION?
a. Hot developer solution
b. Old, expired film
c. Underexposing
d. Underdeveloping
10. Each of the following will result in radiographs that
are blank (clear) EXCEPT one. Which one is the
EXCEPTION?
a. No exposure to x-rays
b. Placing films in the fixer first
c. Extended time in warm water rinse
d. Accidental white light exposure
11. If two films become overlapped together because they
were inserted into the automatic processor too quickly,
what is the result?
a. Green films
b. Brown films
c. Light films
d. Black films
12. Which of these indicates that a film was not properly
washed?
a. Image appears light
b. Fogging results
c. Film turns brown
d. White spots form
13. Each of the following will result in black artifacts
on the radiograph EXCEPT one. Which one is the
EXCEPTION?
a. Static electricity
b. Bent film
c. Glove powder
d. Fixer splash
14. Static electricity appears radiographically as black
a. thin lines.
b. starbursts.
c. dots.
d. Any of the above
240 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
15. Each of the following is a cause of film fog EXCEPT
one. Which one is the EXCEPTION?
a. Exposure to scatter radiation
b. Use of old, expired film
c. Double exposing the film
d. Chemical fume contamination
REFLECT—Case study
You have just finished taking a full mouth series of periapical
and bitewing radiographs. After processing and mounting the
films, you notice the following:
1. The maxillary right molar periapical radiograph did not
image the third molar.
2. The maxillary right canine periapical radiograph appears
elongated, and the image of the root tip is not recorded.
3. The teeth contacts in the right premolar bitewing radiograph are overlapped. The overlapping appears most
severe in the posterior portion of the image and less
severe in the anterior region.
4. The left molar bitewing film was bent when it was
placed into the image receptor holder.
5. The mandibular central incisors periapical radiograph
appears very light, with a hint of a diamondlike pattern
superimposed over the image of the teeth.
6. The film that should have been a left mandibular molar
periapical radiograph is blank, with no hint of an image.
7. The left maxillary premolar periapical radiograph
appears to have been double exposed.
Consider these seven radiographs with the errors noted and
answer the following questions:
a. What is the most likely cause of this error? How did you
arrive at this conclusion?
b. Could there be multiple causes for this error? What
other errors would produce this result?
c. Why do you think this error occurred?
d. What corrective action would you take when retaking
this radiograph? Be specific.
e. What are you basing your decision to reexpose the
patient on?
f. What steps or actions would you recommend to prevent
this error from occurring in the future?
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson Education. Chapter 7, “Identifying and correcting radiographic errors.”
REFERENCES
Carestream Health, Inc. (2007). Kodak Dental Systems:Exposure
and processing for dental film radiography. Pub. N-414,
Rochester, NY: Author.
Eastman Kodak Company. (2002). Successful intraoral radiography.
N-418 CAT No. 103. Rochester, NY: Author.
Thomson, E. M. (2012). Exercises in oral radiographic techniques:
A laboratory manual (3rd ed.,). Upper Saddle River,
NJ: Pearson Education.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Explain the relationship between quality assurance and quality control.
3. List the steps of a quality assurance program.
4. Explain the role a competent radiographer plays in quality assurance.
5. List the four objectives of quality control tests.
6. Make a step-wedge with cardboard and lead foil and demonstrate how to use it.
7. List two tests the radiographer can use to monitor a dental x-ray machine.
8. Explain the use of the coin test to monitor darkroom safelighting.
9. Describe how to test for light leaks in the darkroom.
10. Explain the use of a reference film to test processing chemistry.
11. Explain the use of the fresh-film test to monitor the quality of a box of film.
12. Describe quality control tests for radiographic viewing equipment.
13. Advocate the use of quality assurance to produce diagnostic-quality radiographs with minimal radiation exposure.
KEY WORDS
Coin test
Fresh-film test
Light-tight
Quality assurance
Quality control
Reference film
Step-wedge
Quality Assurance in
Dental Radiography
CHAPTER
OUTLINE
 Objectives 241
 Key Words 241
 Introduction 242
 Quality
Administration
Procedures 242
 Competency of the
Radiographer 242
 Quality Control 243
 Benefits of Quality
Assurance
Programs 248
 Review, Recall,
Reflect, Relate 248
 References 250
CHAPTER
19
242 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
Introduction
Quality assurance is defined as the planning, implementation,
and evaluation of procedures used to produce high-quality radiographs with maximum diagnostic information (yield) while
minimizing radiation exposure. Establishing a quality control
program for radiographic procedures helps to increase the quality
of radiographs produced and decrease the incidence of retake
radiographs. Quality assurance includes both quality administration procedures and quality control techniques (Table 19-1).
The purpose of this chapter is to present quality control tests
that are used to monitor operator competency, the dental x-ray
machine, the darkroom and x-ray processing systems, film and
equipment used to view the images, and documentation and
administrative maintenance.
Quality Administration Procedures
Quality administration refers to conducting a quality assurance
program in the oral health care practice. A quality assurance program
should include an assessment of current practices, where and how
the problems seem to be occurring, a written plan that identifies
who is responsible and what training the personnel need to be
able to carry out the quality control tests, record-keeping, and
periodic evaluations of the plan.
Needs Assessment
Periodically the oral health care team should review patient radiographs for quality. Problems that occur should be documented
and then periodically reviewed to look for areas where a change in
policy, maintenance schedules, or other area is noted.
Written Plan
The oral health care team should develop a written plan that
will guide quality control. The plan should include, but not be
limited to, the purpose of the quality assurance program,
assignment of authority and responsibilities, a list of equipment
that requires monitoring, a list of tests that will be performed
and at what time intervals (Table 19-2), a log of all quality
assurance test results, a log of retake radiographs, documentation of training, and evaluation interval and report.
Careful planning and thoroughly carrying out a quality assurance program increases the likelihood of producing the highest
quality radiographs while minimizing radiation exposure.
Authority and Responsibilities
Although the dentist is ultimately responsible for the overall
quality care that his/her practice provides the patient, each oral
health care team member can be given authority to carry out specific
aspects of the quality control program. Assigning authority and
clearly defining specific tasks and/or maintenance procedures
helps to ensure that the procedures are being carried out. Each
oral health care team member must be informed of how and why
the tasks are to be performed and provided with training opportunities to ensure compentency in performing in this capacity.
Monitoring and Maintenance Schedules
A monitoring schedule listing all the quality control tests, identification of the person responsible for each test, and the frequency of testing should be generated and posted. Checkoff lists
can be used to record maintenance and inspections.
Logs and Periodic Evaluation
A log should be kept of all quality control tests. Include the date,
the specific test, the results, action taken if any, and the name of
the person who conducted the test. Also, a log of all radiographs
retaken should be recorded to identify recurring problems. The
oral healthcare team should meet periodically to evaluate the logs
and the quality assurance program.
Competency of the Radiographer
Essential to a quality assurance program is the ability of the radiographer. Operator errors that result in undiagnostic radiographs
generate the need for retake radiographs. Retakes result in
unnecessary radiation exposure to the patient and lost time for
both the patient and the practice. The radiographer must be
competent not only in exposing, processing, and mounting dental
radiographs, but also in identifying when errors occur. Even
competent radiographers encounter situations where less-thanideal radiographic images result. It is important, therefore, that
TABLE 19-1 Quality Assurance Includes Both
Quality Administration and Quality Control
QUALITY ADMINISTRATION QUALITY CONTROL
Assess needs Operator competence
Develop a written plan X-ray machines
Assign authority and responsibility Darkroom
Provide training Processing equipment
Monitor maintenance schedule Processing chemistry
Document actions and keep records/log X-ray film and storage
Perform periodic evaluation Image viewing
TABLE 19-2 Suggested Time Intervals for
Performing Quality Control Tests
QUALITY CONTROL TEST SUGGESTED TIME INTERVAL
Output consistency Annually
Tube head stability Monthly
Darkroom safelighting Annually
Automatic processor Daily
Processing solutions Daily
Cassettes and screens Annually
Viewboxes Monthly
CHAPTER 19 • QUALITY ASSURANCE IN DENTAL RADIOGRAPHY 243
A B
FIGURE 19-1 Step-wedge. (A) Commercially made
step-wedge. (B) Step-wedge made from discarded sheets of lead foil
from intraoral film packets.
BOX 19-1 Quality Control Tests for Dental
X-ray Machines
1. Radiation output
2. Timer accuracy
3. Milliamperage accuracy
4. Kilovoltage accuracy
5. Focal spot size
6. Filtration (beam quality)
7. Collimation
8. Beam alignment
9. Tube head stability
the radiographer be able to recognize poor quality, identify the
cause, and apply the appropriate corrective action.
Operator errors and retakes should be recorded to identify
recurring problems. Each exposure may be recorded in a log
that can be reviewed periodically to monitor for problems and
the application of the appropriate corrective actions. This will
also help monitor the skills of the radiographer. To aid in operator competency, opportunities such as continuing education
courses or on-the-job-training can assist the radiographer in
brushing up on skills, improving in an area of deficiency,
and/or staying apprised of the newest technology and treatment
recommendations.
Quality Control
Quality control is defined as a series of tests to ensure that the
radiographic system is functioning properly and that the radiographs produced are of an acceptable level of quality. The
objectives of quality control include the following:
1. Maintain a high standard of image quality.
2. Identify problems before image quality is compromised.
3. Keep patient and occupational exposures to a minimum.
4. Reduce the occurrence of retake radiographs.
Examples of quality control measures include tests to evaluate
dental x-ray machine output; tests to evaluate safelighting of
the darkroom, processing chemistry testing and replenishing,
evaluation of safe film storage, view box inspections, calibrations
of computer monitors used to view digital images, documentation
such as records of when processing chemistry needs changing,
posted technique factors near x-ray machines, and a maintenance
log of retakes to keep track of common errors and find solutions
for avoiding them in the future.
Dental X-ray Machine Monitoring
Periodic comprehensive testing of the x-ray machine is essential
to a quality assurance program. These tests include radiation output, timer accuracy, accuracy of milliamperage and kilovoltage
settings, focal spot size, filtration (beam quality), collimation,
beam alignment, and tube head stability (Box 19-1). State and
local health departments may provide or require x-ray machine
testing as part of their registration or licensing programs. In this
case, a qualified health physicist will conduct most of these tests
prior to renewing registration or license. However, the radiographer who uses the equipment on a daily basis should also play a
role in monitoring the x-ray machine. Additionally, a working
knowledge of the quality control tests available will help the
radiographer identify when the equipment is not functioning at
peak performance.
OUTPUT CONSISTENCY TEST (PROCEDURE BOXES 19-1 AND
19-2) Radiation output may be monitored by the radiographer
using a step-wedge. A step-wedge is a device of layered metal
steps of varying thickness used to determine image density and
contrast. A step-wedge may also be used to test the strength of
the processing chemicals, which will be discussed later.
A step-wedge may be obtained commercially or be made
using several pieces of lead foil from intraoral film packets
(Figure 19-1). To perform the radiation output test, the stepwedge is placed on a size #2 intraoral image receptor on the
counter or exam chair and then exposed with set exposure factors. This film is put aside, protected from stray radiation, heat
and humidity, and other potential causes of film fog (see
Chapter 18). The process is repeated with a new film at intervals determined by the practice. For example, the first exposure
may be made in the morning, followed by a second exposure at
midday and a third exposure at the end of the day. At the end of
the desired time frame, all the exposed films are processed at
the same time and evaluated. Consistency in radiation output
will produce three radiographs with images of the step-wedge
that are identical in densities and contrast. A failed test will
produce images that are different from each other, indicating
that the radiation output varied over the course of the day
(Figure 19-2). A failed test would indicate that a qualified
health physicist should examine the x-ray machine.
TUBE HEAD STABILITY Another test the radiographer should
make regularly on the dental x-ray machine is tube head stability. A drifting tube head must not be used until the support arm
and yoke are properly adjusted to prevent movement of the tube
head during exposure. To test for drift, the radiographer should
position the tube head in various positions that will likely be
needed for radiographic exposures to evaluate stability in each
PROCEDURE 19-1
Assembling a step-wedge
1. Divide a piece of cardboard the size of a #2 x-ray film into thirds.
2. Leave the first third uncovered, and cover the remaining two-thirds with two pieces of lead backing from
a discarded film packet. Tape into place.
3. Cover the final third with four additional pieces of lead backing, taping them into place.
244 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
2 lead foils
4 lead foils Cardboard
Clear Dark gray Black
Gray Too dark Gray
Safelight,
light leaks,
age of film,
improper storage,
under development
Over exposure Under exposure,
under development
(too cold, too short,
exhausted, contaminated),
age of film
Under exposure,
under development
(too cold, too short,
exhausted, diluted,
contaminated),
age of film
Too light
Check for:
If it is:
Should appear:
FIGURE 19-2 Sketch of a step-wedge. A step-wedge is useful in making visual comparisons for
quality control.
of the positions. When not in use, the support arm should be
folded into a closed position with the PID pointing down to prevent weight stress from loosening the support arm and causing
drift (Figure 19-3).
Darkroom Monitoring
The darkroom should be evaluated for the presence of conditions
that create film fog and compromise image quality. The darkroom
should be checked to determine that it is adequately ventilated,
free from chemical fumes, within the prescribed temperature and
humidity range recommended by the film manufacturer, beyond
the reach of stray radiation, and light-tight. The key to a safe
darkroom is an appropriate safelight.
SAFELIGHT TEST As you will recall from Chapter 8, the safelight must have a bulb of the proper wattage, have a filter color
CHAPTER 19 • QUALITY ASSURANCE IN DENTAL RADIOGRAPHY 245
FIGURE 19-3 Correct position of tube head when
not in use. Extension arm folded, tube head and PID
aimed at the floor.
PROCEDURE 19-2
Procedure for x-ray machine output consistency test
1. Prepare a step-wedge or use a commercially made device (see Procedure Box 19-1).
2. Obtain three (or desired number) size #2 intraoral film packets from the same package.
3. Place two of the films in a safe place, protected from film fog–causing elements (stray
radiation, heat, humidity, chemical fumes).
4. Place one of the film packets on the counter or exam chair within reach of the x-ray tube head.
5. Place the step-wedge on top of the film packet.
6. Position the x-ray tube head over the film packet and step-wedge, and direct the central rays of the x-ray
beam perpendicularly toward the film packet. Place the open end of the PID exactly 1 in. (2.5 cm) above
the film packet. Use a ruler for accuracy.
7. Set the exposure factors to those utilized for an adult patient maxillary anterior periapcial radiograph.
8. Make the exposure.
9. Place the exposed film in a safe place, protected from film fog–causing elements (stray radiation, heat,
humidity, chemical fumes).
10. Some time after the first exposure (at the desired time interval), retrieve one of the stored size #2 intraoral film packets.
11. Repeat steps 4 through 9.
12. Some time after the first two exposures (at the desired time interval), retrieve the other stored size #2
intraoral film packet.
13. Repeat steps 4 through 9.
14. When ready, process all three of the films at the same time.
15. When processing is complete, observe all three of the films for consistency in density and constrast.
16. A failed test will show a difference in density or contrast among the three images.
17. Call a qualified health physicist to examine the x-ray machine if needed.
PROCEDURE 19-3
Coin test for safelight adequacy
1. Obtain a size #2 intraoral film packet and a coin.
2. Place the film packet on the counter or exam chair within reach of the x-ray tube head.
3. Position the x-ray tube head over the film packet. Direct the central rays of the x-ray beam perpendicularly toward the film packet. Place the open end of the PID about 12 in. (30 cm) above the film packet.
4. Set the exposure factors to the lowest possible setting.
5. Make the exposure.
6. Take the slightly exposed film and a coin to the darkroom. Turn off the overhead white light and turn on
the safelight.
7. Unwrap the film packet and place the film on the counter where you would normally process patient
films.
8. Place the coin on top of the unwrapped film.
9. Wait approximately two or three minutes.
10. Remove the coin from the film and process the film in the usual manner.
11. When processing is complete, observe the film for any outline of the coin. (The film will have an overall
gray appearance or slight fogging from the slight radiation exposure in step 5. However, you are looking
for a distinguishable outline of the coin.)
12. A failed test will show an outline of the coin.
13. Examine the safelight for correct bulb wattage, filter color, scratches or cracks, and distance away from
working area. Perform additional tests to check for possible white light leaks or the presence of other
light sources.
246 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
prompt the radiographer to check to be sure that the safelight bulb
wattage is correct and that the filter color is appropriate for the
film used. The distance away from the working area should be
checked, and the safelight filter should be visually inspected for
scratches or cracks in the filter that would allow white light to
escape.
TEST FOR LIGHT LEAKS Whether the darkroom is light-tight
can be determined by closing the door and turning off all lights,
including the safelight. Light leaks, if present, become visible
after about five minutes when the eyes become accustomed to
the dark. Possible sources of light leaks include around the
entry door or around the pipes leading into the darkroom. Drop
ceiling tiles and ventilation screens may also allow white light
to enter the darkroom. While eyes are still adjusted to the dark,
white light leaks may be marked with tape or chalk to allow the
radiographer to find them when the white overhead lights are
turned back on. Light leaks should be sealed with tape or
weather stripping.
Additional sources of inappropriate light include illuminated
dials or fluorescent objects worn or carried into the darkroom
by personnel. Illuminated dials on equipment located in the
darkroom must be red or may be masked with tape if necessary.
deemed safe for the film being processed, and be located a safe
distance from the working area where films will be unwrapped.
The coin test can be used to test the safelight for adequacy.
The coin test uses a coin and a slightly exposed film to
determine safelight adequacy (Procedure Box 19-3). Because
films that have already been exposed are more sensitive to
conditions that cause film fog, a true test of the safelight uses
a film that is preexposed to a small amount of radiation. After
the test film has been slightly exposed, it is unwrapped in the
darkroom under safelight conditions and placed on the counter
where patient films will normally be unwrapped. A coin is
placed on top of the unwrapped film for two or three minutes.
This period simulates the approximate time required to aseptically unwrap a full mouth series of films and load them into
the processor. It is assumed that while the film is on the
counter, the portion of the film that remains under the metal
coin would be protected from possible light exposure, while
the rest of the area would receive exposure if the light was
unsafe.
When the time is up, the film is processed as usual. After
processing, the film is examined. An image of the outline of the
coin would indicate a failed test, suggesting that the safelight
conditions in the darkroom are fogging the film. A failed test should
CHAPTER 19 • QUALITY ASSURANCE IN DENTAL RADIOGRAPHY 247
Fluorescent wristwatch faces should not be worn in the darkroom unless covered by the sleeve of the operator’s lab coat.
Operators who carry a cell phone in a pocket must completely
shield any light or shut off the phone to prevent accidental
illumination should there be an incoming call.
Processing System Monitoring
Processing equipment and chemistry need to be monitored, and
quality control tests should be performed on a periodic basis.
AUTOMATIC PROCESSOR The key to peak performance of an
automatic processor is maintenance. Often the unit manufacturer
will recommend daily, weekly, monthly, and quarterly maintenance and cleaning procedures to ensure quality performance. A
schedule of set maintenance procedures, and a log of when those
procedures need to be performed, should be posted with the
maintenance scheduling.
These two tests are helpful in daily monitoring of the automatic processor:
1. Begin by processing an unexposed film under safelight
conditions. The film should come out of the return chute of
the automatic processor clear (slightly blue tinted) and dry.
2. Then process a film that has been exposed to white light.
This film should come out of the return chute of the automatic processor black and dry after processing.
A failed test should prompt the operator to check the solutions,
the water supply, and film dryer. The solution levels should be
checked and must be replenished and changed on a regular basis.
The processor should maintain the correct temperature. The water
supply must be turned on and the dryer operating correctly to
produce a clear, dry film.
PROCESSING SOLUTIONS As explained in Chapter 8, chemical manufacturers recommend extending the life of processing solutions with regular replenishment and changing out
expired solutions with fresh chemicals at regular intervals.
Therefore it is important to monitor the strength of the processing solutions on a daily basis, before undiagnostic film
images result.
The developer solution is the most critical of the processing
solutions and demands careful attention. When the developer solution
deteriorates and loses strength, the underdeveloped radiographic
images lighten. Commercially available instruments are available
that can be utilized to monitor the developer. (Figure 19-4) These
devices utilize a filmstrip with several density steps for comparison
to a test film.
The radiographer may prepare a step-wedge from discarded lead foil from intraoral film packets, discussed earlier,
to monitor the developer as well (Procedure Box 19-4). Using
the step-wedge, several films are exposed at the same settings,
all at the same time. At the beginning of the day, immediately
after fresh chemistry has been prepared, one of the exposed
films is processed. This becomes the reference film, with the
ideal image density and contrast. The remaining exposed films
should be stored in a cool, dry place protected from stray radiation and other conditions that produce film fog. At the beginning
of each day, one of the previously exposed films is processed
and compared to the reference film. Each subsequent film
should match the reference film in density and contrast. A failed
test would indicate that the processing chemicals, particularly
the developer, is losing strength and needs to be changed
(Figure 19-2).
X-ray Film Monitoring
Only fresh x-ray film should be used for exposing dental radiographs. Film manufacturers use a series of quality control tests
to ensure dental x-ray film quality. Film should be properly
stored, protected, and used before the expiration date. Check
the expiration date on the x-ray film box and always use the
oldest film first.
The fresh-film test can be used to monitor the quality of
each box of film. When a new film box is opened for use, immediately process one of the films without exposing it. If the film is
fresh, it will appear clear with a slight blue tint. If the film appears
fogged, the remaining films in the box should not be used.
Equipment Used to View Radiographic
Images Monitoring
VIEWBOX If functioning properly, the viewbox should give off
a uniform, subdued light. Flickering light may indicate bulb failure.
The surface of the viewbox should be wiped clean as needed.
COMPUTER MONITOR As discussed in Chapter 9, all types
of monitors perform equally well at displaying digital radiographs for interpretation and diagnosis. Periodically performing
quality control calibrations on the monitor will keep the image
displayed at the proper resolution and gray scale. The manufacturer’s
recommendations should be followed
The location of the monitor where images are viewed should
be evaluated to ensure that bright ambient light is not producing
glare off the monitor surface that will compromise viewing the
images. With the computer turned off, take the usual operator
position in front of the monitor, either seated or standing.
Observe the monitor for reflected images indicating that the
monitor should be moved to a position that eliminates glare.
Extraoral Equipment Monitoring
CASSETTES AND INTENSIFYING SCREENS Quality control procedures include periodically examining cassettes and intensifying
FIGURE 19-4 Dental radiographic quality control device.
Available from Xray QC [formerly Dental Radiographic Devices],
www.xrayqc.com.
PROCEDURE 19-4
Reference film to monitor processing solutions
1. Prepare a step-wedge or use a commercially made device (see Procedure Box 19-1).
2. Obtain several size #2 intraoral film packets from the same package.
3. Place one of the film packets on the counter or exam chair within reach of the x-ray tube head.
4. Place the step-wedge on top of the film packet.
5. Position the x-ray tube head over the film packet and step-wedge, and direct the central rays of the x-ray
beam perpendicularly toward the film packet. Place the open end of the PID exactly 1 in. (2.5 cm) above
the film packet. Use a ruler for accuracy.
6. Set the exposure factors to those utilized for an adult patient maxillary anterior periapcial radiograph.
7. Make the exposure.
8. Place the exposed film in a safe place, protected from film fog–causing elements (stray radiation, heat,
humidity, chemical fumes).
9. Immediately repeat steps 3 through 8 with the rest of the films.
10. Following a complete solution change of the processing chemistry, process one of the exposed films. This
film is the reference film.
11. Mount the reference film on the viewbox.
12. Each day immediately after replenishing the processing chemistry, retrieve one of the stored exposed
films and process as usual.
13. Compare the film processed on this day to the reference film processed when the chemistry was
changed. Look for similar density and contrast indicating that the processing solutions are functioning at
peak levels.
14. Repeat steps 12 and 13 each day. The solutions are exhausted and need to be changed when the density and contrast of the just-processed film does not match the reference film.
248 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
screens. Extraoral cassettes should be checked for warping and
light leaks that can result in fogged radiographs. Defective cassettes should be repaired or replaced.
Intensifying screens should be examined for cleanliness
and scratches. Any specks of dirt, lint, or other material will
absorb the light given off by the screen crystals and produce
white or clear artifacts on the resultant radiographic image.
Dirty screens should be cleaned as needed with solutions recommended by the screen manufacturer. However, overuse of
chemical cleaning should be avoided. Any scratched or damaged
screen should be repaired or replaced.
Benefits of Quality Assurance Programs
Everyone benefits from a well-organized quality assurance program. The time required to assess, plan, implement, and evaluate
a quality assurance program is made up in the time saved and
the benefits gained avoiding the production of poor-quality
radiographs and retakes.
Periodic evaluation of the program will allow for flexibility
as changes in recommended protocols or new techniques come
into being. The ultimate goal of quality assurance is to produce
radiographs with the greatest amount of diagnostic yield using
the smallest amount of radiation exposure.
REVIEW—Chapter summary
Quality assurance is defined as the planning, implementation, and
evaluation of procedures used to produce high-quality radiographs
with maximum diagnostic information (yield) while minimizing
radiation exposure. Quality assurance includes both quality
administration procedures and quality control techniques.
Quality administration refers to conducting a quality assurance program in the oral health care practice. The five steps to a
quality administration program are (1) assess needs, (2) develop a
written plan, (3) assign authority and responsibilities, (4) develop
monitoring and maintenance schedules, and (5) utilize a log and
evaluations to check on the program.
The key to producing the highest quality diagnostic radiographs
with the lowest possible radiation exposure is operator competence.
Quality control is defined as a series of tests to ensure that
the radiographic system is functioning properly and that the
radiographs produced are of an acceptable level of quality.
CHAPTER 19 • QUALITY ASSURANCE IN DENTAL RADIOGRAPHY 249
These tests include the monitoring of the dental x-ray machine,
the darkroom, processing system, and x-ray film. A step-wedge
is a valuable tool that can be used in a variety of tests.
Quality control tests for monitoring dental x-ray machines
include the output consistency test and tube head stability. Quality
control tests for monitoring the darkroom include the coin test for
checking the safelight and for checking for light leaks. Quality
control tests for monitoring the processing system include monitoring the processing solutions with the use of a reference film
or a commercial device. The fresh film test is used to monitor
dental x-ray film.
Everyone, the oral health care team and the patients, benefits
from a well-organized quality assurance program.
RECALL—Study questions
1. The goal of quality assurance is to achieve maximum
diagnostic yield from each radiograph.
Quality control means using tests to ensure quality.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
2. On-the-job training and continuing education courses
contribute to radiographic competence.
Competent radiographers are key to a quality assurance
program.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
3. List the four objectives of quality control.
a. ______________
b. ______________
c. ______________
d. ______________
4. The step-wedge can be used to test each of the following
EXCEPT one. Which one is the EXCEPTION?
a. Dental x-ray machine output consistency
b. Processing chemistry strength
c. Density and contrast of the image
d. Adequacy of the safelight
5. Each of the following is a quality control test for monitoring the dental x-ray machine EXCEPT one. Which
one is the EXCEPTION?
a. Tube head stability test
b. Coin test
c. Output consistency test
d. Timer, milliamperage, and kilovoltage setting accuracy test
6. The use of the coin test will monitor darkroom safelight
conditions.
When an image of the coin appears on the radiograph,
the safelight is adequate.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
7. A film processed under ideal conditions and used to
compare subsequent radiographic images is a
a. fresh film.
b. fogged film.
c. periapical film.
d. reference film.
8. When the automatic processor is functioning properly, an unexposed film will exit the return chute
dry and
a. black.
b. clear.
c. green.
d. with the image of a coin.
9. In addition to the dentist, who is responsible for planning, implementing, and evaluating a quality assurance
plan?
a. Dental assistant
b. Dental hygienist
c. Practice manager
d. All of the above
REFLECT—Case study
The practice where you work needs to update their radiographic
quality control plan. Currently the basic plan mentions the need to
test the x-ray machine and monitor the darkroom and processing
systems. Applying what you have learned in this chapter, develop
a quality control plan for your practice. Include the following:
1. List of equipment you think the practice should be testing
2. The name of the test needed
3. Recommended time interval for performing the test
4. Name of the person assigned to perform the test
5. A description of what a failed test and a successful test
would look like
6. The action required if a failed test results
Then prepare the following documents that your practice
would use to assist the quality assurance plan:
1. A detailed, step-by-step procedure that someone could follow to perform each of the tests you have recommended
2. Forms to keep a log of the outcomes for each of the tests
you recommended
250 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson Education. Chapter 13, “Radiographic
quality assurance.”
REFERENCES
American Academy of Dental Radiology Quality Assurance
Committee. (1983). Recommendations for quality assurance
in dental radiography. Oral Surgery, 55, 421–426.
Eastman Kodak. (1998). Quality assurance in dental radiography.
Rochester, NY: Author.
National Council of Radiation Protection and Measurements.
(1988). Quality assurance for diagnostic imaging equipment:
Recommendations of the National Council on Radiation
Protection and Measurements. NCRP Report no. 99.
Bethesda, MD: NCRP Publications.
Thomson, E. M. (2012). Exercises in oral radiographic techniques. A laboratory manual, (3rd ed.). Upper Saddle
River, NJ: Pearson Education.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Identify agencies responsible for regulations regarding safe handling of hazardous radiographic products.
3. Use MSDSs to identify proper handling and disposal of chemicals and materials associated
with radiographic procedures.
4. List the requirements of the OSHA Hazard Communication Standard.
5. Identify radiographic wastes that are considered hazardous to personnel and harmful to the
environment.
6. Advocate the need for safe handling and proper disposal of radiographic chemicals and
materials.
7. Demonstrate effective use of an eyewash station.
KEY WORDS
Alkaline
Biodegradable
Caustic
Eyewash station
Hazardous waste
Material Safety and Data Sheets (MSDSs)
Neoprene gloves
Nitrile gloves
pH
PPE (personal protective equipment)
Silver thiosulphate complex
Waste stream
CHAPTER
20 Safety and Environmental
Responsibilities in Dental
Radiography
CHAPTER
OUTLINE
 Objectives 251
 Key Words 251
 Introduction 252
 Requirements for
Safety and
Environmental
Health 252
 Safe Handling of
Radiographic
Chemicals and
Materials 252
 Management of
Radiographic
Wastes 259
 Review, Recall,
Reflect, Relate 261
 References 263
252 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
Introduction
To work safely with and around ionizing radiation, dental
assistants and dental hygienists study the characteristics and
properties of x-ray energy. Competence in dental radiation
safety results from a thorough understanding of the appropriate
uses and the potential effects of x-radiation. It is equally important that oral health care professionals understand the properties
and actions of the chemicals and materials that are used in the
production of dental radiographs. Radiographic chemicals and
materials that require careful handling and special disposal
considerations include silver in radiographic film emulsions and
silver thiosulphate complexes in used fixer chemistry; the lead
used in intraoral film packets, lead aprons and thyroid collars,
and older film storage boxes; and broken or obsolete digital
imaging systems. Safe handling of these materials and other
products used in dental radiography will help prevent errors that
may lead to retake radiographs for the patient; avoid injury to the
radiographer; and reduce the potential harm to the environment.
Although the individual oral health care practice generates a
small amount of these hazardous wastes, collectively the potential
exists for a significant impact on the environment. A heightened
awareness of the impact of these wastes on our environment is
changing the way we manage their disposal.
Requirements for Safety and
Environmental Health
Two agencies responsible for recommendations and regulations
regarding safe handling of chemicals and other potentially harmful materials and for the management of hazardous wastes used
in dental radiography are:
• Occupational Safety and Health Administration (OHSA)
Introduced in Chapter 10, we learned that OHSA sets and
enforces regulations that protect the radiographer from
infection in the oral health care setting. OHSA also develops standards for workplace safety regarding the handling
of radiographic chemicals.
• U.S. Environmental Protection Agency (EPA) We learned
in Chapter 10 that the EPA plays a role in the regulation of
disinfectants used in radiographic infection control practices. The EPA’s primary responsibility is to establish and
enforce national standards that protect humans and the
environment.
OSHA requires that manufacturers of chemical products
such as developer and fixer supply Material Safety Data Sheets
(MSDSs) to the oral health care practices that purchase these
products (Figure 20-1). MSDS provide the oral health care
professional with information regarding the properties and the
potential health effects of the product. MSDSs include the
following information:
• Chemical ingredients and common name
• Potential hazards of working with the product
• An explanation of the product’s stability and reactivity
• Requirements for safe handling and storage
• Exposure controls and personal protection required when
using the product
• Disposal considerations
• Regulatory information
Dentists are required by OHSA to obtain and keep on file
an MSDS for every chemical product used in the practice. The
MSDS should be reviewed by all personnel who will work with
the product and kept for easy reference and periodic review to
ensure safe handling. All personnel should receive training and
practice with safe handling of the product and appropriate
emergency exposure responses.
Chemical product manufacturers must also provide warning
labels. Labeling products assists the radiographer in safe management of these products (Figure 20-2). Product labels should
be designed according to the OSHA Hazard Communication
Standard that states that oral health care employees have a right
to know the identities of, and the potential hazards of, the chemicals they will be working with (Box 20-1). Radiographers also
need to know what protective measures to take to prevent adverse
effects that might result when working with the product. This
information will assist the radiographer in establishing proper
work practices and in taking steps to reduce exposure and the
occurrence of work-related illnesses and injuries caused by the
products. All containers must be labeled. This includes the developer and fixer tanks, even those inside an automatic processor,
tubs used to clean the processor rollers, and any containers used
for disposing absorbent towels used to clean up a spill.
MSDSs and product labels must be obtained from the
manufacturer for all chemicals used in radiographic procedures. These include:
• Fixer
• Developer
• Disinfectants
• Cleaners used on processing equipment
Safe Handling of Radiographic Chemicals
and Materials
Safe handling and appropriate exposure emergency responses
when working with the chemicals used in radiographic procedures can be found on the MSDSs for the specific product being
used. The following are general safe handling instructions.
Because the chemical makeup of products will vary depending
on the manufacturer, the radiographer must be familiar with the
BOX 20-1 Requirements of OSHA Hazard
Communication Standard
• Develop a written hazard communication program.
• Maintain an inventory list of all hazardous chemicals present in
the oral health care facility.
• Obtain and have accessible MSDSs for all chemicals.
• Label containers of hazardous chemicals.
• Train all personnel in safe handling of the hazardous chemicals.
253
1. CHEMICAL PRODUCT AND COMPANY IDENTIFICATION
PRODUCT NAME: FORMULA 2000 PLUS COMPONENT 1
PRODUCT TYPE: Special cleaner for removal of oxidation/
reduction products from X-ray film developers
IMPORTER/
DISTRIBUTOR: Air Techniques, Inc.
1295 Walt Whitman Road
Melville, NY 11747, USA
Phone: 516-433-7676
PRIMARY EMERGENCY
CONTACT: CHEMTREC Phone: 1-800-424-9300
2.
CAS# % By Wt. Exposure Limits
COMPOSITION/INFORMATION ON INGREDIENTS
Component
1-Hydroxyethane-1, 1- 2809-21-4 1 – 5 N/A
diphosphonic acid
Thiourea 62-56-6 1 – 5 OSHA 1 mg/kg
Water 7732-18-5 60 – 95 N/A
3. HAZARD IDENTIFICATION
POTENTIAL HEALTH EFFECTS:
ROUTE(S) OF ENTRY: Skin and eye contact
HUMAN EFFECTS AND SYMPTOMS OF OVEREXPOSURE:
1-Hydroxyethane-1,1-diphosphonic acid is a severe eye irritant and a skin irritant.
Thiourea is toxic by ingestion or inhalation. It is an irritant to skin, eyes and
respiratory passages. It may cause sensitization.
CARCINOGENICITY:
NTP: Yes thiourea listed as “reasonably anticipated to be a human carcinogen”
IARC: Yes thiourea group 2B, “possibly carcinogenic to humans”
OSHA: No
California Prop. 65 thiourea listed as “Chemicals known to the State to
cause cancer”
4. FIRST AID MEASURES
SKIN: Remove contaminated clothing and shoes. Flush affected area with large
amounts of water. Do not use solvents or thinners. Get immediate medical attention.
EYES: Hold eyes open and flush for at least 15 minutes with large amounts of
water. Get immediate medical attention.
INGESTION: Do not induce vomiting. Give two glasses of water to dilute stomach
contents. Never give anything by mouth to an unconscious person. Get immediate
medical attention.
INHALATION: Remove to fresh air immediately. If breathing is difficult administer
oxygen. Get immediate medical attention.
5. FIRE FIGHTING MEASURES
FLASH POINT:. N/A
EXTINGUISHING MEDIA: Use extinguishing media suitable for surrounding fire.
SPECIAL FIRE FIGHTING PROCEDURES: Product is not flammble. However,
overheating of containers will produce toxic fumes. Use self contained breathing
apparatus and full protective clothing.
6. ACCIDENTAL RELEASE MEASURES
SPILL AND LEAK PROCEDURES: Wear appropriate personal protective equipment;
contain spills onto inert absorbent and place in suitable containers.
MATERIAL SAFETY DATA SHEET 0
3 0
0
4-EXTREME
3-HIGH
2-MODERATE
1-SLIGHT
0-INSIGNIFICANT
NFPA FIRE
HAZARD SYMBOL
FLAMMABILITY
HEALTH REACTIVITY
SEE NFPA704 F0R DETAILED EXPLANATION
SPECIAL
HAZARDS
7. HANDLING AND STORAGE
STORAGE: Store closed containers in an area away from heat. Do not store at temperatures below 5°C.
HANDLING: Use with adequate ventilation. Avoid skin and eye contact. Do not eat,
drink or smoke in application area.
8. EXPOSURE CONTROLS/PERSONAL PROTECTION
RESPIRATORY PROTECTION: If airborne concentration exceeds recommended limits,
use a NIOSH approved respirator in accordance with OSHA Respirator Protection
requirements under 29 CFR 1910.134.
SKIN PROTECTION: Clothing suitable to avoid skin contact. Use neoprene, nitrile or
natural rubber gloves. Check suitability recommendations by protective equipment
manufacturers, especially towards chemical breakthrough resistance.
EYE PROTECTION: Safety goggles with side shields.
9.
10. STABILITY AND REACTIVITY
CHEMICAL STABILITY: Stable
HAZARDOUS DECOMPOSITION PRODUCTS: Sulfur dioxide.
POLYMERIZATION: Hazardous polymerization will not occur.
INCOMPATIBILITIES: Strong acids and alkaline materials.
11. TOXICOLOGICAL INFORMATION
See Section 3 – Human Effects and Symptoms of Overexposure
12. ECOLOGICAL INFORMATION
Avoid contamination of ground water or waterways. Do not discharge into sewers.
13. DISPOSAL CONSIDERATIONS
Dispose of in accordance with Federal, State or Local regulations.
14. TRANSPORT INFORMATION
DOT SHIPPING NAME: NOT REGULATED.
15. REGULATORY INFORMATION
All components of this product are on the TSCA Inventory.
SARA Title III:
Thiourea is subject to the supplier notification requirements of Section 313 of the
Superfund Amendments and Reauthorization Act (SARA/EPCRA) and the requirements of 40 CFR Part 372.
Note: Entries under this section cover only those regulations typically addressed in
the MSDS generating process, such as TSCA, and EPCRA/SARA Title III.
16. OTHER INFORMATION
HAZCOM LABEL: DANGER! CAUSES EYE BURNS. MAY CAUSE SKIN IRRITATION.
POSSIBLE CANCER HAZARD. CONTAINS INGREDIENT THAT CAUSED CANCER IN
ANIMALS.
To the best of our knowledge, the information contained in this MSDS is accurate.
It is intended to assist the user in his evaluation of the product’s hazards, and safety
precautions to be taken in its use. The data on this MSDS relate only to the specific
material designated herein. We do not assume any liability for the use of, or
reliance on this information, nor do we guarantee its accuracy or completeness.
Printed in Germany 2009-21-01
PHYSICAL AND CHEMICAL PROPERTIES
PHYSICAL FORM: Clear Colorless Liquid
ODOR: Characteristic
PH: 1.0 – 2.0
BOILING POINT: ~212°F (100°C)
AUTOIGNITION: N/A
VAPOR PRESSURE: N/A
SOLUBILITY IN WATER:
DENSITY: 1.02 -1.04 g/cm3
Completely
FIGURE 20-1 Sample MSDS. (Courtesy of Air Techniques, Inc.) (Continued)
254
3. HAZARD IDENTIFICATION
POTENTIAL HEALTH EFFECTS:
ROUTE(S) OF ENTRY: Inhalation, skin and eye contact
HUMAN EFFECTS AND SYMPTOMS OF OVEREXPOSURE:
Sodium persulfate is a severe irritant to skin, eyes and respiratory passages. May
cause sensitization by inhalation or skin contact.
CARCINOGENICITY:
NTP: No
IARC: No
OSHA: No
4. FIRST AID MEASURES
SKIN: Remove contaminated clothing and shoes. Flush affected area with large
amounts of water. Do not use solvents or thinners. Get immediate medical attention.
EYES: Hold eyes open and flush for at least 15 minutes with large amounts of
water. Get immediate medical attention.
INGESTION: Do not induce vomiting. Give two glasses of water to dilute stomach
contents. Never give anything by mouth to an unconscious person. Get immediate
medical attention.
INHALATION: Remove to fresh air immediately. If breathing is difficult administer
oxygen. Get immediate medical attention.
5. FIRE FIGHTING MEASURES
FLASH POINT: N/A
EXTINGUISHING MEDIA: Alcohol foam, carbon dioxide, dry powder, or water
spray.
SPECIAL FIRE FIGHTING PROCEDURES: Product is not flammable. However, overheating of containers will produce toxic fumes. Use self contained breathing apparatus and full protective clothing.
6. ACCIDENTAL RELEASE MEASURES
SPILL AND LEAK PROCEDURES: Wear appropriate personal protective equipment;
collect and place in suitable containers.
MATERIAL SAFETY DATA SHEET
1. CHEMICAL PRODUCT AND COMPANY IDENTIFICATION
PRODUCT NAME:
PRODUCT TYPE:
IMPORTER/
DISTRIBUTOR:
PRIMARY EMERGENCY
CONTACT:
FORMULA 2000 PLUS COMPONENT 2
Special cleaner for removal of oxidation/
reduction products from X-ray film developers
Air Techniques, Inc.
1295 Walt Whitman Road
Melville, NY 11747, USA
Phone: 516-433-7676
CHEMTREC Phone: 1-800-424-9300
2.
45 – 55
COMPOSITION/INFORMATION ON INGREDIENTS
Component
Sodium persulfate 0.1 mg/m3 TWA ACGIH
Sodium sulfate
CAS# % By Wt. Exposure Limits
7775-27-1
45 – 55 N/A
45 – 55
7757-82-6
7. HANDLING AND STORAGE
STORAGE: Store closed containers in an area away from heat and combustible
materials.
HANDLING: Use with adequate ventilation. Avoid skin and eye contact. Do not eat,
drink or smoke in application area.
8. EXPOSURE CONTROLS/PERSONAL PROTECTION
RESPIRATORY PROTECTION: If airborne concentration exceeds recommended
limits, use a NIOSH approved respirator in accordance with OSHA Respirator
Protection requirements under 29 CFR 1910.134.
SKIN PROTECTION: Clothing suitable to avoid skin contact. Use neoprene, nitrile
or natural rubber gloves. Check suitability recommendations by protective equipment
manufacturers, especially towards chemical breakthrough resistance.
EYE PROTECTION: Safety goggles with side shields.
10. STABILITY AND REACTIVITY
CHEMICAL STABILITY: Stable.
HAZARDOUS DECOMPOSITION PRODUCTS: Oxides of Sulfur.
POLYMERIZATION: Hazardous polymerization will not occur.
INCOMPATIBILITIES: Will oxidize organic substances. Keep away from alkalis,
metals, reducing agents and combustible substances.
11. TOXICOLOGICAL INFORMATION
See Section 3 Human Effects and Symptoms of Overexposure
12. ECOLOGICAL INFORMATION
Avoid contamination of ground water or waterways. Do not discharge into sewers.
May be toxic to aquatic organisms.
13. DISPOSAL CONSIDERATIONS
Dispose of in accordance with Federal, State or Local regulations.
14. TRANSPORT INFORMATION
DOT SHIPPING NAME: NOT REGULATED.
15. REGULATORY INFORMATION
All components of this product are on the TSCA Inventory.
SARA Title III:
To the best of our knowledge this product contains no toxic chemicals subject to
the supplier notification requirements of Section 313 of the Superfund Amendments
and Reauthorization Act (SARA/EPCRA) and the requirements of 40 CFR Part 372.
Note: Entries under this section cover only those regulations typically addressed in
the MSDS generating process, such as, TSCA, and EPCRA/SARA Title III.
16. OTHER INFORMATION
HAZCOM LABEL: WARNING! CAUSES SKIN AND EYE IRRITATION. MAY
CAUSE SENSITIZATION BY INHALATION AND SKIN CONTACT.
To the best of our knowledge, the information contained in this MSDS is accurate.
It is intended to assist the user in his evaluation of the product’s hazards, and safety
precautions to be taken in its use. The data on this MSDS relate only to the specific
material designated herein. We do not assume any liability for the use of, or
reliance on this information, nor do we guarantee its accuracy or completeness.
Printed in Germany 2009-21-01
9. PHYSICAL AND CHEMICAL PROPERTIES
PHYSICAL FORM:
ODOR:
pH: N/A
AUTOIGNITION:
VAPOR PRESSURE:
SOLUBILITY IN WATER:
BULK DENSITY:
White powder
Odorless
N/A
N/A
Completely
1100 kg/m3
0
3 0
0
4-EXTREME
3-HIGH
2-MODERATE
1-SLIGHT
0-INSIGNIFICANT
NFPA FIRE
HAZARD SYMBOL
FLAMMABILITY
HEALTH REACTIVITY
SEE NFPA 704 F0R DETAILED EXPLANATION
SPECIAL
HAZARDS
FIGURE 20-1 (Continued)
CHAPTER 20 • SAFETY AND ENVIRONMENT RESPONSIBILITIES IN DENTAL RADIOGRAPHY 255
KODAK GBX Developer and
Replenisher
KODAK GBX Fixer and Replenisher
WHEN DILUTED FOR USE AS RECOMMENDED
Contains:
Water
Ammonium thiosulfate
Sodium bisulfite
CAS Reg. #
7732-18-5
7783-18-8
7631-90-5
Concentrates (not diluted solution) made by:
Eastman Kodak Company
Rochester, New York 14650
(716)722-5151
WHEN DILUTED FOR USE AS RECOMMENDED
Contains:
Water
Hydroquinone
Diethylene glycol
Potassium sulfite
CAS Reg. #
7732-18-5
123-31-9
111-46-6
10117-38-1
*Principal hazardous components.
Warning: causes skin and eye irritation. May
cause allergic skin reaction. Wash thoroughly after handling. (see MSDS)
Concentrates (not diluted solution) made by:
Eastman Kodak Company
Rochester, New York 14650
(716)722-5151
This label is for use only with
the indicated product.
TM: KODAK
This label is for use only with
the indicated product.
TM: KODAK
LOW HAZARD FOR RECOMMENDED HANDLING (see MSDS)
Attach these labels directly to the
proper chemical tanks or containers,
or on the protective cover of the
processor near the chemicals.
These labels are provided
to assist you in complying
with the U.S. Federal OSHA
Hazard Communication Standard –
29 CFR 1910. 1200
List Price $1.00 CIESSL10
FIGURE 20-2 Sample label that meets OSHA Hazard Communication Standard. (Courtesy Carestream Health.)
PRACTICE POINT
Although OSHA requires manufacturers of chemical products to provide users with an MSDS that lists the specific
chemicals found in the product, there is sometimes a reluctance to disclose a chemical when it is considered a trade
secret or special ingredient that the manufacturer considers
unique to their product. A trade secret can help the manufacturer advertise their product as better, or having an
advantage over competitors. OSHA allows leeway for ingredients considered a trade secret, provided that the secret
ingredient must be disclosed immediately on the occurrence
of an emergency. For example, if a reaction occurs following
contact with a chemical that the oral health care professional then seeks medical attention for, the product manufacturer will be contacted, and they must disclose the
identity of the chemical to the medical professional so that
appropriate treatment can occur.
specific requirements for safe handling of the specific brand of
product being used at his/her facility. The following are general
guidelines for safe handling of these chemicals and materials.
Fixer
Safe handling begins with a well-ventilated darkroom and the
use of PPE (personal protective equipment; see Chapter 10),
including protective clothing, mask, eyewear, and impervious
gloves (that do not permit liquid penetration), especially when
cleaning the processing equipment or changing or replenishing
chemistry (Box 20-2). Strong chemicals may penetrate latex
medical examination gloves that are used for patient treatment.
Nitrile or neoprene (rubber) utility gloves provide the radiographer with better protection. The radiographer should avoid
prolonged breathing of fixer chemical vapors. Under normal
conditions, fixer should not cause respiratory difficulty in most
individuals. If heated sufficiently or an accidental contact with
developer occurs, an irritating sulphur dioxide gas may be
released. Close, prolonged contact with this gas may cause some
hypersensitive or asthmatic individuals discomfort. If uncomfortable
symptoms occur, move to a well-ventilated area. If symptoms
persist, seek medical attention.
256 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
Avoid inhaling mist or vapors when pouring fixer liquid
from bottles or when mixing concentrated chemicals with
water. If fixer contacts skin, immediately wash off with soap
and water. If fixer splashes in eyes, flush immediately with
water. A sink and eyewash station should be available in the
darkroom or in close proximity to where processing equipment
and chemistry is handled (Figure 20-3). The radiographer must
know how to use the eye wash equipment so that it can be
appropriately operated in an emergency. (Procedure Box 20-1)
Regular training and practice in responding to a potential exposure can help the radiographer react quickly and appropriately
in an emergency. Minor contact with a small amount of fixer is
not likely to cause irritation, or an allergic reaction. If irritating
symptoms persist as a result of inhaling sulphur dioxide gas or
from repeated, prolonged skin or eye contact, the radiographer
should seek medical attention.
Fixer chemistry should be stored in the original container.
The container must remain unopened or tightly capped until
ready for use to prevent oxidation and the buildup of chemical
vapors in the storage area. An accidental spill should be absorbed
with a disposable towel immediately. A spill can increase the
amount of vapors released in the vicinity. The towel used to
absorb the spill should be treated as chemical waste and disposed of in the same manner as used fixer. The surface where
the spill occurred should then be cleaned thoroughly to remove
any trace of the chemical. After handling fixer containers or
after wiping up a spill, remove contaminated PPE and wash
hands before performing any other task. The impervious gloves
should be disinfected and dried before storing. Wash contaminated clothing prior to wearing again.
BOX 20-2 General Recommendations for Safe Handling of Hazardous Chemicals
• Read MSDS for the specific product being used.
• Provide training on the use of the product.
• Keep container of product tightly closed.
• Store in the original container.
• Do not store product in the same area where food or drinks are stored or consumed.
• Ensure proper labeling of product.
• Wear appropriate PPE.
• Impervious clothing or vinyl apron recommended.
• Use protective eyewear with side shields. Safety goggles recommended.
• Use nitrile or neoprene gloves.
• Avoid breathing mist or vapor.
• Avoid contact with eyes.
• Avoid prolonged or repeated contact with skin.
• Use only with adequate ventilation.
• Wash hands thoroughly after handling.
• Do not consume foods or drink or smoke where chemicals are handled.
• Dispose of container appropriately.
• Do not reuse container.
• Remove and launder clothing if contaminated.
• Periodically check PPE to ensure working condition.
FIGURE 20-3 Eyewash station. Radiographer preparing to use
the eyewash station in response to accidental contact with a
potentially hazardous chemical. Note the recognizable label on the
wall noting the location of the eyewash station.
Developer
Developer requires the same safe handling precautions as
fixer, which includes adequate ventilation and avoiding contact (Box 20-2). Developer has a high pH, meaning that it is
alkaline or caustic and very capable of burning biological tissues on contact. It is this caustic property that makes developer
an even more serious eye irritant than fixer. An accidental eye
exposure requires an immediate flushing with water at an eyewash station for a minimum of 15 minutes (Procedure Box 20-1).
If a contact lens is present, it should be removed if easy to do.
The radiographer should seek medical attention following
accidental eye contact with developer. If developer contacts
skin, immediately wash off with soap and water. Prolonged or
CHAPTER 20 • SAFETY AND ENVIRONMENT RESPONSIBILITIES IN DENTAL RADIOGRAPHY 257
*If easy to do, contact lens should be removed. Rinse fingers well. Do not use the same finger to hold open the eyelids
unless thoroughly washed of possible chemical contamination.
PROCEDURE 20-1
Use of an emergency eyewash station
1. Eyewash station
a. Must be within 25 feet of where potentially hazardous chemicals are being used.
b. Personnel must be able to get to the station within 10 seconds from where they are handling potentially hazardous chemicals.
c. Must be clearly labeled with appropriate signage that is easily recognized.
2. Remove the caps covering the eye wash faucets. Caps should be easy to remove.
3. Turn on the water flow to a rate of about 0.5 gallons per minute.
4. Water temperature should be warm, between 60 to 95 degrees.
5. Hold the eye lids open with an index finger and thumb. Do not touch the eyeballs.*
6. Maintain water contact with the eyes for the recommended rinsing time, 5 to 60 minutes, even if
uncomfortable.
7. Consult the product MSDS to determine the recommended rinsing time. Acids such as fixer are easier to
rinse away than alkalines such as developer. Truly caustic chemicals that may be used in processor cleaners may require a 60-minute rinse time.
8. Seek medical attention at completion of the recommended rinse time.
repeated skin contact may cause irritation that results in drying
or cracking and can result in depigmentation.
Accidentally mixing developer with fixer, even in minute
droplets, will result in the release of an irritating sulphur dioxide gas. If contamination occurs between developer and fixer,
both tanks should be emptied and cleaned, disposing of both
solutions appropriately. When cleaning the processing equipment or changing or replenishing chemistry, the radiographer
should take care to avoid a splash that would mix developer
and fixer (Figure 20-4). If developer is spilled, the same steps
taken to contain a fixer spill should be followed. Using a disposable towel, absorb the liquid and then thoroughly clean the
surface to remove any trace of the chemical. The towel should
be treated as chemical waste and disposed of appropriately.
Remove, disinfect, and dry the impervious gloves; remove
contaminated PPE; and wash hands before performing any
other task.
Disinfectants
The radiographer should be aware of the possible hazards of
contact with or inhaling the vapors of the disinfectants that
will be used in the radiographic process. (See Chapter 10.)
The oral health care facility should have written documentation of what chemicals are used to disinfect radiographic
equipment and clinical contact surfaces, where these are stored,
and the preparation dates to avoid using expired disinfectants.
FIGURE 20-4 Barrier placed to separate the developer and
fixer tanks when adding chemicals.
Updating the inventory at regular intervals will assist with
maintaining only effective disinfectant solutions and knowing
when to discard older chemicals. The radiographer must
use PPE (personal protective equipment; see Figure 10-2),
including protective clothing, mask, eyewear, and impervious gloves when preparing and using any level of disinfectant.
Low- or intermediate-level disinfectants are commonly used
to prepare clinical contact surfaces prior to radiographic
procedures. Although not as corrosive as high-level disinfectants
258 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
FIGURE 20-5 PPE used when cleaning processing equipment.
FIGURE 20-6 Old lead-lined storage box showing signs of flaking.
or sterilants, the same level of caution should be used when
handling any chemical. The radiographer should be familiar with
the emergency first aid requirements for the product being
used. Regular review of the MSDS and training updates,
especially if a new product has been introduced, will
prepare the radiographer for the appropriate action in an
emergency.
Contact with the disinfectant should be avoided. If eye or
skin contact should occur, flush immediately with water. If
diluting or mixing of the chemical concentrate is required prior
to use, the bottle used for this purpose must be labeled appropriately. Labels should be maintained and checked periodically
to be sure that the information remains readable. Never use or
reuse a container that was made for another product to prepare
disinfectant solutions.
Although the affects of accidental skin and eye contact or
inhaling the vapors of the disinfectant will depend on the chemical used in the product, in general, accidental exposures should
be handled in the same manner as described previously for
fixer or developer contact. If discomfort does not subside after
flushing skin or eyes with water or moving to a well-ventilated
area, the radiographer should seek medical attention.
Cleaners Used on Processing Equipment
Processing equipment, especially the rollers in the tanks of
automatic processors, require cleaning to provide optimal
radiographs. Cleaning agents used to remove residue and
oxidized chemicals from the reducing agents in developer
usually contain strong acids and corrosive agents. As with
disinfectants, the radiographer should consult the MSDS on
the product to determine the appropriate PPE (personal protective equipment) and to be prepared with the correct action
should an accidental exposure occur. Most manufacturers of
processing cleaners recommend that PPE (personal protective equipment) cover the skin, especially around the wrists
and arms. Puncturing inner safety seals to open bottles of
chemicals and mixing, pouring, and/or spraying cleaner
products all increase the risk of a splash that could lead to
accidental exposure. Most processor cleaners will cause skin
irritations and eye burns on contact. An apron made from an
impervious material such as vinyl or rubber is recommended.
Nitrile or other suitable heavy-duty utility gloves must be
used when handling these cleaners. It is recommended that
the radiographer check with the manufacturer of the gloves
to determine their ability to prevent the chemical cleaner
from breaking through the glove material. Safety goggles are
the recommended eyewear protection, especially when using
a spray bottle to apply the cleaner to rollers (Figure 20-5).
Adequate ventilation will prevent irritation to respiratory
tissues. If discomfort results, the radiographer should move
to a well-ventilated area. If symptoms persist, seek medical
attention. If there is accidental contact with skin, flush with
plenty of water. Because of the caustic nature of cleaners of
this type, accidentally splashing cleaner in the eyes requires
medical attention after flushing the eyes with water for a
minimum of 15 minutes. If cleaner contacts the radiographer’s
clothes or shoes, these should be removed and washed before
reusing.
Lead
Normal handling of intact lead foil used in intraoral film packets
and lead sealed in aprons and thyroid collars will not present a
hazard to the radiographer. In years past, lead-lined containers
or film packet dispensers were available in which to store film
safely away from stray radiation until ready for use. Improvements made to fast-speed film have made these lead-lined boxes
unnecessary. In fact these lead-lined containers should not be
used either for storage of film or any other storage or dispensing
purpose. The lead lining is subject to flaking off in a powder
form with the potential for inhalation or ingestion (Figure 20-6).
All old radiographic storage containers suspected of being made
CHAPTER 20 • SAFETY AND ENVIRONMENT RESPONSIBILITIES IN DENTAL RADIOGRAPHY 259
of lead should be appropriately discarded. (See next section on
management of radiographic wastes.) All intra- and extraoral
film should be stored in original packaging until ready for use.
Management of Radiographic Wastes
Disposal of hazardous wastes generated by the oral health care
practice is often mandated by federal law. It is important to
note that some state and local waste management regulations
are more stringent than federal regulations. In many areas, it is
against the law to discard used fixer into the municipal sewer
system or to discard lead foil at municipal landfills. The radiographer must know what laws apply in the practice area. Equally
important is the ethical responsibility to recycle or properly dispose of wastes that may be harmful to the environment.
The most common way to dispose of the hazardous materials used in dental radiography appropriately is to contract with
a waste disposal company. Many practices already employ a
waste management company to dispose of biohazard materials.
These same companies usually offer a hazardous waste service
that can manage radiographic wastes as well.
The MSDS for the product can sometimes be vague in
proper disposal of the product, often stating to “dispose of
according to state or local regulations.” Therefore is it important to know what the regulations are for the practice area.
Some of the options for proper management of radiographic
wastes are:
• Contract with a waste management company to provide
container and pick-up service.
• Contract with a lead or silver reclaiming company for
recycling.
• Establish an agreement with the supplier to “take back”
used fixer/unused radiographic film.
• Collect the used product and transport it to a designated
drop-off center in your community.
• Utilize silver recovery or reclaiming system (for used fixer).
Although it is most important to know what the laws are in
the location of the oral health care practice, the following are
general guidelines for proper management of radiographic
wastes.
Used Fixer Waste
Both developer and fixer are biodegradable, meaning that they
can be broken down into harmless products by a wastewater
treatment facility. In Chapter 7 we learned that the function of
fixer is to remove the unexposed and undeveloped silver halide
crystals from the emulsion of radiographic film. Compared to
photographic processing facilities, which also use fixer to
remove silver halides, oral health care practices generate a
very small amount of silver waste. The silver found in used
fixer of dental radiographic processors is in the form of a very
stable silver thiosulphate complex. Thus bonded, there are
virtually no free silver ions present in used fixer, prompting
experts to conclude that used fixer poses very little threat to the
environment if discharged into wastewater treatment facilities.
However, many state and local municipalities have regulations
regarding the amount and/or the concentration of used fixer
that can be discharged to a wastewater treatment facility. The
oral health care practice has several sound and environmentalfriendly options to responsibly dispose of used fixer. Collecting
used fixer for the purpose of extracting the silver ions will
conserve a resource and prevent adding this metal to the waste
stream. The easiest way for an oral health care facility to
achieve these goals is often to contract with a licensed company
that will provide containers for collection and periodic pickup
for proper disposal. It is important that the qualifications of the
contractor selected for disposal of hazardous wastes or recycling
be thoroughly investigated. If materials are disposed of
inappropriately, it is possible that the oral health care practice
would be partly liable for fines and costs incurred by faulty
handling of materials by the disposal service (Box 20-3).
An option that allows for silver recovery in-office at the
site of use is to purchase a silver recovery system. Silver recovery or reclaiming systems attach to the automatic processor
BOX 20-3 Questions to Ask of a Waste Management Service
• Are you licensed to handle hazardous wastes?
• What types of hazardous wastes do you accept?
• Do you have certifications in the management of certain materials?
• Do you provide a pickup service, or do you accept shipment of wastes at your facility?
• Will containers for collecting the wastes be supplied?
• Is your company the primary recycler?
• What will be the final destination of the materials?
• How do you track the transport of the materials from our practice to the final destination?
• What materials will be recycled? Where will these materials end up?
• Who is responsible for completing EPA or other state-required documentation?
• What is the cost of your service?
• Is there a reimbursement payment for returning silver, lead, or other precious metals (from recycled electronic equipment) for recycling?
260 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
FIGURE 20-8 Lead foil waste. Collecting lead foil from film
packets for proper disposal by a licensed waste management
contractor.
fixer and/or rinse water drain line (Figure 20-7). These systems
can be adapted for use with manual and chairside processing as
well. When attached to an automatic processor, as the processor
operates and when the fixer tank is drained for cleaning and
changing the chemistry, the used fixer is circulated through the
silver recovery unit. Silver recovery systems that use metallic
replacement technology remove the hazardous silver ions from
the used fixer before allowing the solution to go down the
drain. Once the cartridge inside the silver recovery unit is saturated with silver ions, it can be removed by a commercial waste
disposal company and replaced with a fresh cartridge.
Lead Waste
Lead foil from inside intraoral film packets should be separated
from the outer moisture-proof wrap and black paper to keep it
out of the waste stream (Figure 20-8). Many states or local
municipal landfills have regulations regarding disposal of this
heavy metal. Lead foil waste can be recovered and recycled for
another use. Other lead-containing products that are no longer
serviceable, such as damaged lead aprons or thyroid collars, or
no longer recommended, such as lead-lined film storage boxes
or dispensers (Figure 20-6), should also have the lead recovered
or recycled prior to disposing of these items into the waste
stream. Options for disposal of items containing lead are suggested in Table 20-1. As mentioned previously, when selecting a
contractor, it is important that the contractor be licensed to avoid
litigation or fines as a result of their faulty handling of materials.
Discarded Radiographs Waste
Oral health care practices are advised to keep dental radiographs
indefinitely. (See Chapter 11.) Legal issues such as malpractice
and the varying statutes of limitations between states make this
recommendation a good risk management strategy. However,
there are times when a practice may have a need to dispose of
unwanted or very old radiographs. Unused radiographic film may
occasionally need to be discarded, as is the case when it has been
damaged or contaminated by exposure conditions that cause fogging or it is past the expiration date (see Figure 7-9). Radiographs
contain silver that should be recovered or recycled prior to disposal into the waste stream. The amount of silver remaining in the
film will depend on whether it has been processed (old radiographs) or not and also on the density of the radiographic image.
Film that has been processed will have had some of the silver ions
removed during fixation, and radiographs that are more dense
(darker) will have more of the silver ions remaining on the radiograph base material. Options for proper disposal of radiographic
film include contacting the company that the product was purchased from to see if they will take back the product or contracting with a licensed waste management company.
Digital Imaging Equipment
The move away from film-based radiography to digital imaging
will reduce and may eventually eliminate many of the hazardous
wastes associated with dental radiography. However, electronic
equipment poses a whole new set of considerations for disposal
and recycling. As technology advances, older equipment
becomes obsolete. Computers, monitors, solid-state digital sensors, and phosphor plates (see Chapter 9) continue to improve,
phasing out older systems. Also, electronic failure of computer
equipment, broken sensor wires, and damaged phosphor plates
will all need to be disposed of properly. This electronic equipment contains both hazardous materials such as lead, mercury,
cadmium, and beryllium and valuable metals such as gold, palladium, platinum, and silver. Computers and monitors also contain
glass, plastic, and aluminum that are readily recycled. Proper
FIGURE 20-7 Silver reclaiming unit. Attached to the drain tube
of the automatic processor. Note the appropriately labeled bottles of
developer and fixer attached to the unit for automatic chemical
replenishment.
CHAPTER 20 • SAFETY AND ENVIRONMENT RESPONSIBILITIES IN DENTAL RADIOGRAPHY 261
TABLE 20-1 Options for Disposal of Radiographic Waste Products
Fixer 1.Collect for recycling/return to supplier for recovery of silver.
2. Treat to remove silver before discharge to municipal wastewater treatment.
3.Contract with hazardous waste disposal company.
Developer 1. Usually acceptable to discharge to municipal wastewater treatment. Check state/local regulations.
Disinfectants 1. Usually acceptable to discharge to municipal wastewater treatment. Check state/local regulations.
2.Choose disinfectants containing less-hazardous materials.
3. Use barriers to minimize the need for disinfecting.
Radiographic processor cleaners 1.Choose cleaners containing less-hazardous materials.
2. Take steps daily, such as the use of a cleaning sheet, to minimize the need for strong chemicals
(Figure 20-9).
3. Use mechanical methods (brush/sponge) instead of chemicals.
Radiographs/unused film 1.Collect for recycling/return to supplier for recovery of silver.
2.Contract with hazardous waste disposal company.
3. Send to metal reclaimer.
4. May be acceptable to discharge to municipal landfills. Check state/local regulations. However,
recovery and recycling is recommended.
Lead foils and other lead-containing
items (aprons/boxes)
1.Collect for recycling/return to supplier for recovery of lead.
2.Contract with hazardous waste disposal company.
3. Send to metal reclaimer.
Digital imaging equipment 1.Collect for recycling/return to supplier for recovery of precious metals and plastics.
2.Remanufacture and upgrade.
3. Donate usable equipment. Remove sensitive data regarding patient records before recycling/donating.
4. Visit EPA Web site eCycle: How to recycle or donate used electronics
FIGURE 20-9 Cleaning sheet. Run daily or more often, the
cleaning sheet can pick up debris from the rollers maintaining the
processor for longer intervals between cleanings with a strong chemical.
recycling and disposal of electronic equipment can preserve precious resources and keep hazardous materials out of municipal
landfills. Options for reusing older digital imaging equipment
include refurbishing and/or upgrading to accommodate new
technology or donating still usable equipment for uses that may
not require the latest technology. If disposal is required, the same
considerations regarding the qualifications of a hazardous waste
company previously discussed should be given.
The radiographer must possess a working knowledge of safe
handling and safe disposal of the chemicals and materials used in
dental radiography. It is important to be familiar with national,
state, and local laws regulating the handling and disposal of hazardous wastes. Laws and regulations guide and direct the oral
health care practice to handle radiographic chemicals and materials safely, but an ethical responsibility to the environment should
also play a role in how the oral health care practice reduces,
reuses, and recycles materials to avoid adding to the waste stream.
REVIEW—Chapter summary
Many of the chemicals and materials used in the radiographic
process are considered hazardous and require a working knowledge of safe handling and proper disposal. Two agencies responsible
for regulations that help to protect and inform the radiographer
are the Occupational Health and Safety Administration (OHSA)
and the Environmental Protection Agnecy (EPA). OSHA requires
that oral health care practices maintain Material Safety Data
Sheets (MSDSs) and product labels for all hazardous chemicals
used in the radiographic process. The hazardous chemicals used
in the radiographic process that require an MSDS include fixer,
developer, disinfectants, and cleaners used on processing
equipment.
Safe handling instructions for hazardous chemicals can be
found on the MSDSs. The radiographer should be familiar with
safe handling and effective emergency responses when working
with hazardous chemicals. General safe handling and emergency
responses were outlined and include use of PPE, impervious
262 RADIOGRAPHIC ERRORS AND QUALITY ASSURANCE
gloves, adequate ventilation, and avoiding inhalation or contact
with skin or eyes. However, because the chemical ingredients
vary among product manufacturers, the radiographer is responsible for studying the MSDS for the specific product being used.
Emergency responses to skin and eye exposures include
immediate flushing with water and seeking medical attention
for symptoms that persist. Emergency eyewash stations must be
within 25 feet or 10 seconds from where the chemical is being
handled. The radiographer should be trained in the use of the
emergency eyewash equipment.
Oral health care practices have a legal and ethical responsibility to the environment to properly dispose of hazardous radiographic chemicals and materials. Chemicals and materials that
must be given consideration for proper disposal or recycling
include used fixer (because it contains silver thiosulphate complexes), lead foils from intraoral film packets, or other sources
such as lead aprons and thyroid collars and lead-lined storage
boxes. Safe and proper disposal instructions can be found on
the product MSDS and by contacting the federal, state, and
local agencies responsible for regulation of wastes. Safe disposal options include contracting with a licensed waste disposal company, collecting the waste for recycling, and
eliminating or reducing the waste on-site. Although the shift to
digital imaging will eventually eliminate most of the hazardous
chemicals and materials associated with film-based radiography, electronic equipment will require the development of safe
disposal protocols as well.
RECALL—Study questions
1. List two agencies responsible for the development of safe
handling standards for hazardous chemicals and materials
used in the radiographic process.
a. ______________
b. ______________
2. Each of the following may be found on a Material
Safety Data Sheet (MSDS) EXCEPT one. Which one is
the EXCEPTION?
a. Chemical ingredients
b. Date of manufacture
c. Requirements for safe handling
d. Disposal considerations
3. A Material Safety Data Sheet (MSDS) would NOT
need to be obtained for which of the following?
a. Lead foils from intraoral film packets
b. Radiographic fixer
c. Radiographic developer
d. Low-level disinfectant
4. Each of the following is a requirement of the OSHA
Hazard Communication Standard EXCEPT one. Which
one is the EXCEPTION?
a. Maintain an inventory of all hazardous chemicals.
b. Provide training for all personnel who handle the
chemicals.
c. Label all containers that will hold hazardous chemicals.
d. Store all hazardous chemicals in the same central
location.
5. List radiographic wastes that are considered hazardous to personnel and harmful to the environment.
a. ______________
b. ______________
c. ______________
d. ______________
e. ______________
6. Which of the following lists of personal protective
equipment (PPE) is the best recommendation for the
dental radiographer when cleaning the processing
equipment?
a. Long-sleeve lab coat, eyeglasses, mask, latex gloves
b. Long-sleeve barrier gown, eyeglasses with side
shields, mask, vinyl gloves
c. Long-sleeve barrier gown with rubber apron, safety
goggles, mask, nitrile gloves
d. Scrubs with rubber apron, safety face shield, respirator mask, neoprene gloves
7. Each of the following will help prevent an accidental
exposure to hazardous chemicals EXCEPT one. Which
one is the EXCEPTION?
a. Store the product in the smallest container possible.
b. Be familiar with the MSDS information regarding
the product.
c. Use the chemical in a well-ventilated area.
d. Wash hands thoroughly after handling the chemical.
8. In general, what is the emergency recommendation if
fixer or developer splashes into the eyes?
a. If an irritation develops, then move to a wellventilated area.
b. Keep eyes securely closed and seek medical attention immediately.
c. Wait 5 minutes to determine the severity of the exposure. Then seek medical attention.
d. Immediately flush with a steady stream of warm
water for a minimum of 15 minutes.
9. Which of the following is NOT a requirement for an
emergency eyewash station?
a. Must be clearly labeled.
b. Water temperature must not exceed 60 degrees.
c. Must be located within 25 feet or 10 seconds of
where the chemical is handled.
d. The flow of water must be easy to activate.
10. Chemicals with what pH would be most likely to cause
severe eye irritation?
a. Low pH (acidic)
b. Neutral pH
c. High pH (alkaline)
11. Which of the following is LEAST likely to require
special consideration prior to discharging into the waste
stream?
a. Lead foils from intraoral film packets
b. Used fixer
c. Used developer
d. Digital imaging equipment
CHAPTER 20 • SAFETY AND ENVIRONMENT RESPONSIBILITIES IN DENTAL RADIOGRAPHY 263
REFLECT—Case study
Oral health care practices have a legal and an ethical responsibility to the environment to properly dispose of hazardous radiographic chemicals and materials. However, today the focus has
shifted from proper disposal and recycling to prerecycling, or
reducing the amount of waste generated in the first place. Make a
list of all the materials and resources you can think of that are
used in the radiographic process. Include the plastic barriers used
to cover equipment, the types of image receptor holders available
for use, the wash water that circulates when the automatic processor is running, etc. Then using the technique of brainstorming, list
ways to reduce the generation of waste and to conserve resources.
For example: (1) eliminate the use of image receptors made from
polystyrene and (2) purchase film from a “green”
company who has demonstrated environmentally sound operations in manufacturing their product. Combine your ideas with
your classmates and consider sharing the list in a presentation at
the next meeting of your professional association.
RELATE—Laboratory application
Assess and update the written hazard communication program
at your facility. Begin by performing a physical inventory of all
chemicals and potentially hazardous products. Make note of
where the products are stored. Is the product stored in one location, or in multiple areas throughout the facility? Are the containers labeled appropriately? List the products by their trade
name. Next, using the Internet, visit the product manufacturer’s
Web site to get an up-to-date copy of the MSDS and product
labels. Print out and organize the MSDSs into a three-ring
binder. A suggested way to organize the MSDSs is:
1Styrofoam R2;
MSDS Number Product
1 Kodak READYMATIC Dental Developer
and Replenisher
2 Kodak READYMATIC Dental Fixer
and Replenisher
3 Birex Disinfectant Wipes
4 Air Techniques Formula 2000 Plus
health care team or class where each person will review the
steps for safe handling and disposal of the product. Provide the
opportunity for everyone to practice safe protocols and simulated emergency responses to exposures.
REFERENCES
American Dental Association. (2007). Best management practices
for amalgam waste. Retrieved March 28, 2010, from http://
www.ada.org/prof/resources/topics/topics_amalrecyclers.pdf
American Dental Association Council on Scientific Affairs.
(2003). Managing silver and lead waste in dental offices.
Journal of the American Dental Association, 134, 1095–1096.
Carestream Health Inc. (2007). Kodak dental systems: Exposure and processing for dental film radiography. Pub. N414. Rochester, NY: Author.
Carestream Health Inc. (2010). Environmental health and
safety support. Health, safety and environment frequently
asked questions. Retrieved March 28, 2010, from http:/
/carestreamhealth.com/ehs-faqs.html
DePaola, L. G. (2008). Surface disinfection in the dental office.
The infection control forum. Current infection control
insights from The Richmond Institute. The Richmond Institute for Continuing Education, 6(6).
Eastman Kodak Company. (1990). Management of photographic wastes in the dental office. Pub N-414 8–90.
Rochester, NY: Author.
Eastman Kodak Company. (1994). Waste management guidelines. Pub N-414 6-94-BX revision. Rochester, NY:
Author.
Molinari, J. A., & Harte, J. A. (2009). Cottone’s practical infection control in dentistry (3rd ed.). Philadelphia: Lippincott
Williams & Wilkins.
Rockett, W. M. (2009). Revamped recycling. Simple steps
to do your part and make the dental practice a more
eco-conscious environment. Retrieved March 28, 2010,
DentalProductsReport.com.
Thomson, E. M. (2012). Exercises in oral radiographic techniques. A laboratory manual, (3rd ed.,). Upper Saddle
River, NJ: Pearson Education.
Thomson-Lakey, E. M. (1996). Developing an environmentally
sound oral health practice. Access, 10(4), 19–26.
United States Environmental Protection Agency. (n.d.). eCycling. Retrieved April 3, 2010, from http://www.epa.gov/
epawaste/conserve/materials/ecycling/index.htm
Wikipedia. (n.d.). United States Environmental Protection
Agency. Retrieved March 28, 2010, from http://en
.wikipedia.org/wiki/Epa
Print out and attach labels to all containers, including the
developer and fixer tanks inside the automatic processor and any
tubs used to wash and clean the rollers. Once organized, study
the MSDS for each of the products, or assign one or more of the
MSDSs to each member of the oral health care team or your
class to study. Then schedule a training session for your oral
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. List at least five advantages of mounting radiographs.
3. Discuss the use and importance of the identification dot.
4. Compare labial and lingual methods of film mounting.
5. Demonstrate mounting radiographs according to the suggested steps presented.
6. List at least five anatomic generalizations that aid in mounting radiographs.
7. Compare interpretation and diagnosis.
8. Describe the roles of the film mount, viewbox, and magnification in viewing radiographs.
9. List considerations for reading digital radiographic images not encountered when reading
film-based radiographs.
10. Demonstrate viewing radiographs according to the suggested steps presented.
KEY WORDS
Anatomical order
Diagnosis
Film mount
Film mounting
Identification dot
Interpretation
Labial mounting method
Lingual mounting method
Viewbox
Mounting and Introduction
to Interpretation
PART VII • MOUNTING AND VIEWING
DENTAL RADIOGRAPHS
CHAPTER
21
CHAPTER
OUTLINE
 Objectives 264
 Key Words 264
 Introduction 265
 Mounting
Radiographs 265
 Viewing the
Radiographs 268
 Using Mounted
Radiographs 270
 Review, Recall,
Reflect, Relate 270
 References 272
CHAPTER 21 • MOUNTING AND INTRODUCTION TO INTERPRETATION 265
Introduction
Mounting is an important step in the interpretation of dental
radiographs. Dental radiographs must be mounted in the correct anatomic order to allow for a thorough and systematic
interpretation. A thorough knowledge of the normal anatomy of
the teeth and jaws is needed to mount radiographs correctly.
Therefore, mounting and interpreting dental radiographs go
hand in hand.
The purpose of this chapter is to describe the step-by-step
procedures for mounting and viewing dental radiographs. To aid
in this process, basic key points regarding anatomic landmarks
will be discussed. Chapter 22 provides the detailed radiographic
interpretation of normal radiographic anatomy.
Mounting Radiographs
Film mounting is the placement of radiographs in a holder
arranged in anatomical order (Figure 21-1). The advantages of
film mounting are:
• Intraoral radiographs are easier to view and interpret in the
correct anatomical position.
• Mounting decreases the chance of error caused by confusing the patient’s right and left sides.
• Viewing films side by side allows for easy comparison
between different views.
• Less handling of individual radiographs results in fewer
scratches and fingerprint marks.
• Film mounts can mask out distracting side light, making
radiographs easier to view and interpret.
• Film mounts provide a means for labeling the radiographs
with patient’s name, date of exposure, name of the practice, etc.
• Mounted films are easy to store.
• Patient education and consultations are enhanced when
films are mounted.
• When mounted labially, radiographic findings can be easily transferred to the patient’s dental chart.
Film mounting generally refers only to intraoral films.
Large extraoral radiographs must be labeled with lead letters or
tape that identify the right and left sides and are often placed in
an envelope so the patent’s name and the date of the exposure
can be written on the outside.
Occasionally, single intraoral radiographs are not mounted,
but are placed into a small envelope and attached to the patient
record. However, it is better to mount even a single or a small
group of radiographs. A full mouth series should always be
mounted for accurate viewing. In addition, the film mount provides a place to record the patient’s name, date, and other pertinent information.
Film Mounts
Film mounts are celluloid, cardboard, or plastic holders with
frames or windows for the radiographs (Figure 21-2). Attaching the radiographs to the film mounts is called film mounting.
Film mounts are available in many sizes and with numerous
combinations of windows or frames to fit films of different
sizes. Mounts may be large enough to accommodate a fullmouth series of radiographs or hold only a few or even a single
radiograph. Standard commercially made mounts are available,
or companies will make custom mounts to suit special needs.
Black plastic or gray cardboard mounts are often preferred over
clear plastic mounts because these can block out extraneous
light from the viewbox, enhancing viewing and interpretation.
Identification Dot
An embossed identification dot near the edge of the film appears
convex or concave, depending on the side from which the film is
FIGURE 21-1 Full mouth series mounted in an opaque mount.
266 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
The second method, recommended by the American Dental
Association and the American Academy of Oral and Maxillofacial Radiology, is the labial mounting method. With the labial
method of film mounting, the radiographs are mounted so that
the embossed dot is convex. In this position, the viewer is reading
the radiograph as if standing in front of, and facing, the patient
(Figure 21-4). Therefore, what the viewer observes on the right
side of the radiograph would correspond to the patient’s left side.
Essentially, the viewer’s right is the patient’s left. This also corresponds to the order in which teeth and anatomical structures are
drawn on most dental and periodontal charts.
Film Mounting Procedure
Radiographs should be mounted immediately after processing.
Handle films by the edges to avoid smudging or scratching
them, and label the radiographs to prevent loss or mixing them
up with other patient films. An orderly sequence to the mounting procedure is suggested (Procedure Box 21-1). This is especially true for the beginner. Although the sequence for mounting
is often a matter of preference, the first step in mounting all
radiographs should be to orient the embossed dot the same way
for all the films. When mounting using the labial method, orient all the films so that the embossed dot is convex.
When mounting a full mouth series of periapical and
bitewing radiographs, it is helpful to use the film sizes and orientation in the oral cavity to help with the mounting process.
Size #1 film is often used to radiograph the anterior region.
Additionally, anterior periapical radiographs are placed in the
oral cavity with the long dimension of the film packet positioned vertically, whereas posterior periapical radiographs are
viewed. If the film packet was placed in the patient’s oral cavity
correctly, the raised portion of the identification dot (the convexity) automatically faces the x-ray tube and the source of radiation.
Therefore, when the radiograph is viewed later, the identification
dot may be relied on to determine which are the patient’s left and
right sides. Because the radiograph may be viewed from either
side, it is important that the radiographer understand the role the
identification dot plays in film orientation.
Film Mounting Methods
Because the radiograph may be viewed from either side, two
methods of film mounting have been used. The first method, now
obsolete but still used by some dentists, is the lingual method.
With the lingual mounting method, the radiographs are
mounted so that the embossed dot is concave. In this position, the
viewer is reading the radiograph as if standing behind the patient
(Figure 21-3). Therefore, what the viewer observes on the right
side of the radiograph would correspond to the patient’s right as
well. Essentially, the viewer’s right is the patient’s right. Position of
identification dot
when film is
positioned inside
the mouth
Viewer’s orientation
is looking at the teeth
from outside the mouth
FIGURE 21-4 Labial method of film mounting. When the
identification dot is viewed in the convex position, the viewer’s
orientation is in front of and facing the patient. The patient’s left is
the viewer’s right.
FIGURE 21-2 Examples of various film mounts. Film mounts
are available in a variety of sizes and film combinations.
Position of
identification dot
when film is
positioned inside
the mouth
Viewer’s orientation
is looking at the teeth
from inside the mouth
FIGURE 21-3 Lingual method of film mounting. When the
identification dot is viewed in the concave position, the viewer’s
orientation is from behind the patient. The patient’s left is the
viewer’s left.
CHAPTER 21 • MOUNTING AND INTRODUCTION TO INTERPRETATION 267
placed in the oral cavity with the long dimension of the film
packet positioned horizontally. These clues may be utilized to
help the radiographer determine where to position the films in
the mount.
To mount correctly, the radiographer must have a base knowledge in radiographic anatomy. Chapter 22 covers radiographic
PROCEDURE 21-1
Suggested sequence for mounting a full mouth series of radiographs
1. Place the films on a clean white or light-colored paper towel or tray cover on the counter in front of a viewbox.
2. Wash hands to prevent smudging the films.
3. Orient the embossed dots all the same way.
4. Separate the bitewing from the periapical radiographs.
5. Separate the anterior from the posterior periapical radiographs.
6. Separate the maxillary from the mandible periapical radiographs.
7. Orient the periapical radiographs so that the roots are pointing up for the maxilla and down for the
mandible.
8. Orient the bitewing radiographs so that the occlusal plane slants upward in the posterior, producing a slight
“smile” appearance.
9. Place the anterior periapical radiographs into the appropriate frame on the left or right side of the film
mount.
10. Place the posterior periapical radiographs into the appropriate frame on the left or right side of the film
mount.
11. Place the bitewing radiographs into the appropriate frame on the left or right side of the film mount.
12. Label the film mount with the patient’s name, date of exposure, facility name, and other pertinent information.
13. Check the mounted films to be sure they are secured in the mount and are mounted appropriately.
(Embossed dots all facing the same direction, no films upside down.)
14. Place the mounted radiographs on the viewbox for use during the patient appointment and for interpretation.
anatomy observed on intraoral radiographs, (Table 21-1). However, to aid in the mounting procedure, the following generalizations are offered:
• Roots and crowns of the maxillary anterior teeth are larger
and longer than those of the mandibular teeth.
TABLE 21-1 Anatomical Landmarks Distinguishing Maxillary Radiographs from
Mandibular Radiographs
AREA MAXILLARY ANATOMICAL LANDMARKS MANDIBULAR ANATOMICAL LANDMARKS
Incisor Incisive foramen Lingual foramen
Median palatine suture Genial tubercles
Nasal fossa Nutrient canals
Nasal septum Mental ridge
Anterior nasal spine Mental fossa
Canine Inverted Y
Lateral fossa
Premolar Maxillary sinus Mental foramen
Molar Maxillary sinus Mandibular canal
Zygomatic process of maxilla Oblique ridge
Zygoma Mylohyoid ridge
Maxillary tuberosity Submandibular fossa
Hamulus
Coronoid process of mandible
268 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
The dental hygienist and dental assistant play a valuable
role in the preliminary diagnosis, by interpreting deviations
from normal radiographic anatomy and calling these to the
attention of the dentist. The more pairs of eyes evaluating the
radiographs, the more benefit to the patient.
Viewing Equipment
A viewbox and a magnifying glass are required for optimal film
viewing (Figure 21-5). Holding radiographs up to the overhead
room light will not provide adequate conditions in which to
observe detailed, subtle changes often revealed by radiographs.
• Viewbox. Many types of viewboxes are available. The viewbox lighting must be of uniform intensity and be evenly diffused. The viewing surface should be large enough to
accommodate a full set of intraoral radiographs as well as
typical dental extraoral radiographs (i.e., panoramic radiographs). The film mount or a cardboard template should be
used to mask out distracting light around the mount. Blocking out excess sidelight reduces glare and facilitates viewing. The use of gray or black cardboard or frosted plastic
film mounts helps to reduce glare and enhances the detail of
the images. Always use subdued room lighting to allow the
eyes to adapt to the light level of the radiographs.
• Magnifying glass. Some viewboxes are equipped with a
magnifying device (Figure 21-6). Otherwise, a handheld
magnifying glass should be used to aid the radiographer.
• Computer monitor. Transferring the ability to read filmbased radiographs to the ability to read digital images on a
computer monitor requires practice for radiographers who are
new to digital imaging. Instead of utilizing a viewbox, digital
images are read directly off the computer monitor. Considerations not encountered when reading film-based radiographs
include the possibility of not being able to view an entire full
mouth series of images on one screen without switching
between views and the multiple mouse clicks that may be
needed to view images side by side, especially when viewing
radiographs taken on different days and stored in different
files on the computer. Additionally, viewing digital images
will be restricted to the area where the computer and monitor
• Canine teeth generally have the longest roots when compared to adjacent teeth.
• Maxillary molars generally have three roots. The presence of
the palatal root makes it difficult to visual three distinct roots.
• Mandibular molars generally have two divergent roots
that are distinctly observed. Bone is visible in between the
two roots.
• Most roots curve toward the distal.
• Large radiolucent areas denoting the nasal fossa or the maxillary sinus indicate that the radiograph is of a maxillary area.
• The body of the mandible has a distinct upward curve
toward the ramus in the molar area. The film should be oriented so that a slight “smile” appearance is detected.
After the last radiograph has been mounted, the entire film
mount should be carefully checked to see that:
• Identification dots all face the same direction.
• All radiographs are arranged in proper anatomical order.
• No radiographs were reversed or mounted upside down.
• The radiographs are firmly attached to the mount.
• The patient’s name and date have been recorded on the
mount.
Viewing the Radiographs
Proper viewing is essential for the interpretation of dental radiographs. One must be familiar with and understand optimal
viewing conditions and the proper sequence of viewing the
radiographs.
Interpretation versus Diagnosis
Dental radiographs are viewed by any trained professional (dentist, dental hygienist, or dental assistant) with knowledge of normal anatomic landmarks of the maxilla, mandible, and related
structures. Radiographs may be interpreted by all members of the
oral health care team, but the dentist is responsible for the final
interpretation and diagnosis. Interpretation is explanatory and
may be defined as reading the radiograph and explaining what is
observed in terms the patient understands. Items that a dental
hygienist or dental assistant may interpret are radiographic errors
such as overlapped contacts or elongated images; artifacts that
may have appeared on the radiograph such as the image of a film
holder; and normal radiographic anatomy such as the absence of
a developing permanent tooth under a primary tooth or the presence radiographically of unerupted third molars. Diagnosis is
defined as the determination of the nature and the identification
of an abnormal condition or disease. An example of interpretation would be showing the patient the image of the developing
third molar on the radiograph, whereas diagnosis would be the
dentist determining that the third molar is impacted. Referring a
patient to the dentist for evaluation of a radiolucent finding on the
proximal surface of a tooth that appears on a bitewing is interpretation. Dental hygienists and dental assistants are trained to identify this deviation from normal-appearing enamel and can point
out these deviations for further evaluation by the dentist. Telling
the patient that the radiolucency is caries and requires treatment
is diagnosis, a responsibility of the dentist.
FIGURE 21-5 Radiographer viewing radiographs.
Radiographs should be viewed in subdued room lighting, using a
viewbox and a magnifying glass. Note the black film mount that
blocks distracting light around the films.
CHAPTER 21 • MOUNTING AND INTRODUCTION TO INTERPRETATION 269
are located. Coping with overhead room lighting reflecting off
the monitor screen is another consideration the radiographer
will have to manage. Setting up the monitor in a position to
minimize reflections from overhead room lighting or ambient
lighting entering the room through windows will assist with
reducing glare that can interfere with interpretation.
The radiographer can utilize the computer software features to magnify images and enhance gray scale levels to
assist with interpretation. (See Chapter 9.)
FIGURE 21-6 Viewboxes come in many varieties. Note the attached magnifying
device on three of these viewboxes. (Courtesy of Dentsply Rinn.)
Depending on the radiographer’s training and responsibility, the individual may now proceed to make a preliminary
interpretation and discuss it with the dentist, who will make
the final diagnosis regarding any findings. A thorough examination is best accomplished when a specific sequence of
analysis is used (Procedure Box 21-2 and Figure 21-7). The
mounted radiographs must be viewed in a systematic order to
prevent errors in interpretation. All available radiographs
should be examined for a specific condition, and then the
PROCEDURE 21-2
Suggested sequence for viewing a full mouth series of radiographs
1. Place the mounted radiographs on the viewbox.
2. Dim the overhead lights and turn on the viewbox light.
3. Using a magnifying glass, begin the examination in the patient’s maxillary right posterior region (Figure 21-7).
4. Proceed horizontally to the anterior region and continue to the patient’s maxillary left posterior region.
5. Next, move down to the patient’s mandibular left posterior region.
6. Proceed horizontally to the anterior region and continue to the patient’s mandibular right posterior region.
7. Next, move up to the bitewing radiographs, starting with the right molar bitewing radiograph on the left
side of the film mount. Proceed horizontally, examining each bitewing radiograph until you finish with the
left molar bitewing radiograph on the right side of the film mount.
8. Repeat steps 3 through 7 for the following conditions:
a. Presence or absence of teeth
b. Tooth morphology and eruption patterns
c. Deviations from normal and/or suspected pathology
d. Presence, type, and condition of dental materials
e. Caries
f. Periodontal conditions and risk factors
9. Document all findings on a preliminary radiographic interpretative form.
10. Collaborate with the dentist regarding findings.
11. After confirmation and diagnosis of findings by the dentist, record findings on the patient’s permanent
record.
12. Assist the dentist in explaining findings and treatment plan to the patient using the radiographs.
270 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
(See Chapter 11.) Although radiographs often lose value after
more than six months to one year due to changes in the patient’s
oral conditions, they are valuable for comparing present with
previous conditions. The need for an orderly filing system cannot
be overstressed. Misplaced radiographs can result in inappropriate treatment being rendered, may cause risk management problems, and may have legal implications. All radiographs should be
handled with care to prevent smudging or scratching. Radiographs should be protected from heat damage by storage in
cool, well-ventilated areas.
REVIEW—Chapter summary
A thorough knowledge of normal radiographic anatomical
landmarks is needed for mounting and interpreting radiographs. Mounting films is recommended for its many advantages. Film mounts vary in size and number of frames, but all
have space for documenting information such as the patient’s
name and date of exposure. Each film has an embossed identification dot used to determine the patient’s left and right sides.
Lingual mounting places the identification dot in a concave
position, so that the patient’s left side is the viewer’s left side.
Labial mounting places the identification dot in a convex position, so that the patient’s left side is the viewer’s right side.
Labial mounting method is the recommended method.
To aid in fast and accurate mounting of radiographs, a systematic procedure should be followed. The first step in film
mounting is to orient the embossed identification dot the same
way (convex) for all radiographs. Several generalizations
regarding the teeth and oral cavity anatomy can be used to aid
in mounting radiographs correctly.
Interpretation is explanatory, as is the reading of radiographs. Diagnosis uses radiographs to determine the nature and
identification of the disease or abnormality. Dental radiographs
may be interpreted by the dentist, dental hygienist, or dental
assistant. The dentist is responsible for the final diagnosis.
Viewing radiographs is facilitated with the use of a viewbox
and magnification. Mounted radiographs must be viewed in a
systematic order to prevent errors in interpretation. Locating the
computer monitor away from the glare of ambient lighting will
assist the radiographer in viewing digital radiographic images.
Radiographs should be interpreted thoroughly during or after
the patient’s appointment. Radiographs should be accurately
labeled, used to compare present with previous conditions, and
kept indefinitely.
RECALL—Study questions
1. List four advantages of mounting intraoral radiographs.
a. ______________
b. ______________
c. ______________
d. ______________
examination process should be repeated for the next condition. For example, the radiographs may be examined first for
the presence or absence of teeth and other development anomalies. A second examination could concentrate on detecting
caries, and the third examination would look for periodontal
conditions. Interpreting these conditions is discussed in
Chapters 23, 24, and 25.
When interpreting more than one radiograph, such as a set
of bitewings or a full mouth series, the teeth and the supporting
structures are often imaged more than once. While maintaining
a systematic order of interpretation, it is helpful to compare
each area in all of the views. For example, a suspected periodontal condition may be observed on a maxillary periapical radiograph, whereas the bitewing radiograph may possibly image
the level of bone with more detail. Comparing adjacent films
will add to a thorough interpretation.
All radiographic findings must be noted in the patient’s
record after confirmation by the dentist. Although all professionals may record findings, the final interpretation and diagnosis is the responsibility of the dentist.
Using Mounted Radiographs
Radiographs should be developed and mounted as soon as possible and placed on the viewbox during the patient’s appointment for easy reference during treatment. At each subsequent
appointment the latest radiographs should be placed on the
viewbox, where they can be easily accessed as needed.
After the appointment, all radiographs should be thoroughly
interpreted during time set aside for this purpose. Unless only
one or two radiographs were taken, there may not have been
enough time during the patient’s appointment to thoroughly
review each film for all possible conditions. Once the interpretation is complete, the radiographs should be filed appropriately
and kept indefinitely as part of the patient’s permanent record.
1
14 8
7
2
15
13 12 11 10 9
16 17 18
345 6
FIGURE 21-7 Proper sequence for viewing radiographs. The
radiographer should view the radiographs in the sequence illustrated.
Start with number 1 and proceed clockwise through number 18.
CHAPTER 21 • MOUNTING AND INTRODUCTION TO INTERPRETATION 271
2. A desirable film mount should be
a. made of cardboard.
b. made of plastic.
c. translucent, to allow light to reach the film.
d. black, to block out light transmission and prevent
glare.
3. Which of these helps to determine whether the radiograph is the patient’s left or right side?
a. Slight “smile” appearance
b. Distally curved roots
c. Large crowns
d. Identification dot
4. Labial method film mounting positions the identification dot concave.
The labial method is the recommended film mounting
method.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
5. Lingual method film mounting positions the identification dot convex.
When utilizing the lingual method, the viewer’s right is
the patient’s left.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
6. Mounting is the placement of radiographs in a holder
arranged in anatomical order.
All radiographs should be handled with care to prevent
smudging or scratching.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
7. Which of the following should be done first when
mounting radiographs?
a. Orient the identification dot the same way.
b. Separate bitewing from periapical films.
c. Separate the anterior from the posterior films.
d. Orient the teeth roots to point in the correct
direction.
8. Each of the following will aid the radiographer in correctly mounting radiographs EXCEPT one. Which one
is the EXCEPTION?
a. Anterior films are positioned with the long dimension vertically.
b. Canine teeth generally have the longest roots.
c. Maxillary molars usually have three roots.
d. Roots and crowns of mandibular teeth are usually
larger than maxillary teeth.
9. Reading and explaining radiographic images is
a. diagnosing.
b. interpreting.
c. viewing.
d. mounting.
10. The final responsibility to diagnose the radiograph rests
with the
a. dental assistant.
b. dental hygienist.
c. dentist.
d. patient.
11. Viewing mounted radiographs in a systematic sequence
can help prevent errors in interpretation.
Mounted radiographs may be thoroughly viewed by
holding the mount up to overhead room lighting.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
12. Which of these is NOT a consideration when viewing
digital radiographic images?
a. Glare off the computer monitor must be managed to
enhance interpretation.
b. Radiographic images must be utilized where a computer monitor is located.
c. Multiple mouse clicks may be required to view a full
mouth series of radiographs.
d. A magnifying glass will be required for optimal
viewing and interpretation.
13. In which region is it best to begin the interpretation
process when viewing radiographs mounted using the
labial method?
a. Maxillary left posterior
b. Maxillary right posterior
c. Mandibular left posterior
d. Mandibular right posterior
272 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
14. Following diagnosis by the dentist, the radiographic
findings must be recorded on the patient’s record by the
a. dental assistant.
b. dental hygienist.
c. dentist.
d. Any of the above
REFLECT—Case study
These four radiographs have just exited the automatic processor. Based on what you learned in this chapter, correctly
“mount” each of these four radiographs by writing the corresponding number in the correct frame of the film mount.
Assuming the identification dots are all positioned convex,
label the film mount indicating the left and right sides. Then
address the following:
1. Describe how you determined which side was the left
and which side was the right.
2. List the steps you followed to mount these radiographs
correctly.
3. List three generalizations you used to mount these films.
4. List three final checks you would make to double-check
your mounting procedure.
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson. Chapter 6, “Film mounting and radiographic landmarks.”
REFERENCES
Horner, K., Drage, N., & Brettle, D. (2008). 21st century
imaging. London: Quintessence Publishing Co.
Langland, O. E., & Langlais, R. P. (2002). Principles of dental
imaging (2nd ed.). Philadelphia: Lippincott Williams &
Wilkins.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
1 2
3 4
Recognizing Normal
Radiographic Anatomy
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Provide three rationales for why it is important to recognize and identify normal anatomical
landmarks of the face and head.
3. Describe and identify the facial and cranial bones.
4. Differentiate between the lamina dura and the periodontal ligament space.
5. Describe and identify the radiographic appearance of all structures of the teeth.
6. Name significant anatomical landmarks of the maxilla and mandible.
7. Identify significant anatomy normally seen on intraoral radiographs of the maxilla and
mandible.
KEY WORDS
Alveolar bone
Alveolar process
Alveolus
Angle of mandible
Anodontia
Anterior nasal spine
Apical foramen
Cancellous bone
Cementum
Condyle
Coronoid process of the mandible
Cortical bone
Dentin
Dentition
Enamel
Exfoliation
External auditory meatus (foramen)
Frontal bone
Genial tubercles
Hamulus
Impacted teeth
Incisive (anterior palatine) foramen
Inferior border
Inverted Y
Lamina dura
Lateral fossa
Lingual foramen
Mandible
Mandibular canal
Mandibular foramen
Mandibular notch
Mastoid process
Maxilla
Maxillary sinus
Maxillary tuberosity
Median palatine suture
CHAPTER
OUTLINE
 Objectives 273
 Key Words 273
 Introduction 274
 Significant Normal
Anatomical
Landmarks 274
 Radiographic
Appearance of
the Alveolar Bone
and Tooth Area 277
 Anatomy Basics,
Intraoral
Radiographs 278
 Review, Recall,
Reflect, Relate 286
 References 288
CHAPTER
22
274 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
Introduction
Learning to read radiographic images and to recognize normal
radiographic anatomy, the radiographer begins to develop an
appreciation for precise placement of the image receptor and
accurate techniques. Before the radiographer can identify a
deviation from the normal, a solid base knowledge of what is
normal is required. The importance of learning to identify normal radiographic anatomy may be summarized as follows:
1. To evaluate the image receptor for correct positioning so that
the areas of interest and anatomical structures are clearly
visible, enhancing the diagnostic value of the radiograph
2. To assist with determining into which frame of the x-ray
mount each radiograph is to be mounted
3. To assist in interpreting radiographs and recognizing a
deviation from the normal that would require referral to the
dentist for evaluation
The purpose of this chapter is to review the anatomy of the
head and neck region and to describe these anatomical structures as they often appear on dental radiographs.
Significant Normal Anatomical Landmarks
Although most anatomical landmarks observed on intraoral
radiographs are located on the maxilla or the mandible, the
radiographer should also be able to recognize and identify the
major bones and anatomical structures of the cranium and face.
This knowledge is particularly useful when reading extraoral
radiographs such as a panoramic radiograph.
Some of the cranial and facial bones that may be imaged
on dental radiographs are illustrated in Figures 22-1 and 22-2.
These include the frontal bone; the right and left parietal
bones; the occipital bone; the right and left temporal bones;
the right and left zygomas (zygomatic bone, also called malar
bone or cheekbone); the zygomatic arch, which is made up of
Sphenoid
Zygoma (malar)
Zygomatic process
of maxilla
Maxilla
Mandible
Frontal
Parietal
Nasal
Median palatine
suture
FIGURE 22-1 Frontal view of the skull.
KEY WORDS (Continued)
Mental foramen
Mental fossa
Mental ridge
Mylohyoid ridge
Nasal bones
Nasal conchae
Nasal fossa (cavity)
Nasal septum
Nutrient canal
Nutrient foramen
Oblique ridge
Occipital bone
Periodontal ligament (PDL)
Permanent teeth
Primary teeth
Pterygoid plates
Pulp chamber
Ramus
Septum
Sphenoid bone
Styloid process
Submandibular fossa
Supernumerary teeth
Suture
Symphysis
Temporal bone
Torus mandibularis (lingual torus)
Trabeculae
Trabecular bone
Zygoma
Zygomatic arch
Zygomatic process
CHAPTER 22 • RECOGNIZING NORMAL RADIOGRAPHIC ANATOMY 275
Zygoma
Maxilla
Mandible
Frontal Parietal
Nasal
Zygomatic arch
Temporal
Styloid process
External auditory
meatus (foramen)
Mastoid process
Occipital
FIGURE 22-2 Lateral view of the skull.
the temporal process of the zygoma and the zygomatic process
of the temporal bone; the sphenoid bone; the right and left
nasal bones; the external auditory meatus (foramen); the
styloid process; the mastoid process of the temporal bone; the
right and left maxilla; and the mandible.
The teeth are located within the alveolar processes of the
maxillae and the mandible; thus most dental radiographs
include portions of these bones. The maxillae are actually two
bones, a right and left maxilla, whereas the mandible is a single
bone. Generally, but not always, the same landmarks appear on
both right and left sides.
It is helpful to consider the overall location of these features prior to learning how and where each will appear on an
intraoral radiograph. Figure 22-3 shows the nasal septum
and the anterior nasal spine. Figure 22-4 illustrates the location of the median palatine suture, the maxillary tuberosity area, and the incisive (anterior palatine) foramen. The
maxillary sinus is an empty space within the maxilla.
Figures 22-5 and 22-6 illustrate the structures of the
mandible: body; ramus; inferior border; alveolar process;
angle of the mandible; condyle; coronoid process;
mandibular notch; mandibular foramen; mental
foramen; mandibular canal, which is located within the
mandible between the mandibular foramen and the mental
foramen; mental ridge; symphysis; lingual foramen;
genial tubercles; oblique ridge; mylohyoid ridge; and the
submandibular fossa.
Some of these landmarks are visible only on larger occlusal
and extraoral radiographs. Depending on the placement of the
image receptor, patient positioning and the angle of the x-ray
beam, certain landmarks may or may not be imaged. Furthermore, the angle of the x-ray beam may distort the appearance of
the structure so that it may not always appear exactly as illustrated in this textbook. However, a working knowledge of what
structures are likely to be imaged will assist the radiographer in
achieving competence in this skill.
Nasal septum
Nasal conchae
Anterior nasal spine
FIGURE 22-3 Frontal view of the nose.
276 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
Incisive foramen
(anterior palatine foramen)
Maxillary tuberosity
Median palatine suture
FIGURE 22-4 Palatal view of maxilla.
Mandibular notch
Coronoid process
Oblique ridge
Condyle
Ramus
Angle
Body Inferior border
Alveolar process
Mental foramen
Mental ridge
Symphysis
FIGURE 22-5 Lateral view of detached mandible.
Mandibular foramen
Mylohyoid ridge
Submandibular fossa Genial tubercles
Lingual foramen
FIGURE 22-6 Lingual view of detached mandible.
CHAPTER 22 • RECOGNIZING NORMAL RADIOGRAPHIC ANATOMY 277
Radiographic Appearance of the Alveolar
Bone and Tooth Area
Before considering the appearance of these specific bones and
their features on a full mouth series of radiographs, it is important to recognize and identify the normal appearance of the
alveolar bone and the structures of the teeth. Compare the
drawing in Figure 22-7 with a radiograph of the same area
shown in Figure 22-8.
Bone
Although bones appear solid, they are solid only on the outside
and are honeycombed within. Bone is classified as cortical
bone, a compact or dense form of bone, such as what lines the
outside layers of the maxillae and the mandible, and cancellous
or spongy bone, which forms the bulk of the inner bone.
Small, interconnected trabeculae (bars or plates of bone)
form a multitude of various-sized compartments that account
for the honeycomb appearance. These trabecular bone spaces
are usually filled with fat, blood, or bone cells, which accounts
for the difference in the radiographic appearance of bone.
All bone tissues appear radiopaque. The compact or cortical outside layer appears extremely radiopaque (white), whereas
the cancellous bone varies in radiopacity (shades of gray)
according to the size and number of the trabecular spaces. The
area may even appear almost radiolucent (black) if these spaces
are very large or if the bone is thin, as is the case in the area of
the submandibular fossa.
By definition, the alveolar process is that portion of the
maxilla or mandible that surrounds and supports the teeth. It is
composed of the lamina dura and the supporting bone.
LAMINA DURA The lamina dura is the hard, cortical bone
that lines the alveolus (the tooth socket). On radiographs, the
lamina dura appears as a thin radiopaque (white) border that
outlines the shape of the alveolus (the root of the tooth). The
supporting bone is cancellous and varies in density in the different parts of the alveolar process.
PERIODONTAL LIGAMENT SPACE The teeth are attached to
the lamina dura by the fibers of the periodontal ligament
(PDL). The PDL itself is made up of soft tissues and therefore
will not be imaged on a radiograph. However, the space in
which the PDL lies is often visible as a thin radiolucent (dark)
border between the lamina dura and the roots of the teeth.
NUTRIENT CANALS Nutrient canals are thin radiolucent
lines of fairly uniform width that sometimes exhibit radiopaque
borders. They contain blood vessels and nerves that supply the
teeth, bone, and gingivae. Nutrient canals are most often visualized in the anterior of the mandible and in edentulous areas.
When nutrient canals open at the surface of the bone, they often
appear radiographically as a tiny radiolucent dot called the
nutrient foramen.
Teeth
The tooth structures are enamel, dentin, cementum, and pulp.
Enamel, the hardest body structure, covers the crown and is
very radiopaque. The underlying dentin is not as dense and
appears less radiopaque. The cementum that covers the roots is
even less dense. Because only a thin layer of cementum covers
the root, it is generally indistinguishable radiographically from
the underlying dentin (Figure 22-8). Although all three highly
calcified tooth structures vary in radiopacity in direct proportion to the thickness of each structure in the path of the x-ray
beam, for descriptive purposes enamel, dentin, and cementum
are considered radiopaque.
The tooth pulp that occupies the pulp chamber and the
root canals is the only noncalcified tooth tissue. As this soft tissue offers only minimal resistance to the passage of x-rays, it
appears radiolucent. The end of the root canal is called the
apical foramen. This foramen permits the passage of nerves
and blood vessels that nourish the tooth structures.
Enamel
Dentin
Pulp chamber
Cementum
Periodontal ligament
Pulp (root) canal
Lamina dura
Cancellous
(trabecular) bone
FIGURE 22-7 Drawing of mandibular premolar–molar area.
1 2
3
4
5 6
7
FIGURE 22-8 Radiograph of mandibular premolar area
showing (1) dentin, (2) enamel, (3) pulp chamber, (4) periodontal
ligament space, (5) lamina dura, (6) pulp (root) canal, and
(7) cancellous (trabecular) bone. Note that because only a very
thin layer of cementum covers the root, it is radiographically
indistinguishable from the underlying dentin.
278 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
DENTITION To correctly identify and interpret radiographs,
one needs to understand the dentition. Young children have 20
primary teeth that are gradually lost as they grow older. During the transition years a mixed dentition—that is, both primary
and permanent teeth—may be present. A radiograph may show
the primary teeth with partially resorbed roots, which are in a
process of exfoliation, as well as permanent teeth whose roots
are not yet fully formed, which are in the process of eruption.
This is a normal phenomenon and is often observed in radiographs of children between 6 and 12 years old (Figure 22-9).
There are 32 permanent teeth, including all four of the third
molars (wisdom teeth).
Occasionally, teeth form but are unable to erupt. These are
described as impacted teeth. Some people have one or more
extra teeth, called supernumerary teeth. Another deviation is
the congenital absence of certain teeth, described as anodontia.
These conditions occur so frequently that, although not normal,
they are not considered pathologic.
Anatomy Basics, Intraoral Radiographs
Learning to identify anatomical structures and their specific landmarks takes practice. Radiographs provide a two-dimensional
image of three-dimensional structures. When imaging the head
and neck region, multiple structures may be imaged superimposed on top of each other, adding to the difficulty of correctly
identifying these structures. The first step in becoming competent
at this skill is to understand what basic anatomy may be in the
path of the x-ray beam. This will assist the radiographer in distinguishing what will be recorded on the radiograph (Figure 22-10).
It is helpful to be aware of which structures appear
radiopaque and radiolucent. As you will recall from Chapter 4,
structures that are dense and absorb or resist the passage of xrays will appear light or white on the radiograph. Structures that
permit the passage of x-rays with little or no resistance will
appear dark or black. Bone and its dense features such as a ridge,
spine, or tubercle will appear radiopaque, whereas less dense features such as a foramen, canal, or suture will appear radiolucent.
To aid the radiographer in learning the radiographic appearance
of anatomy, it is helpful to remember that a landmark called the
oblique ridge will be a radiopaque structure, and a landmark
called the mental foramen will appear radiolucent (Table 22-1).
Just as it is helpful to follow a systematic order when mounting and interpreting films, the radiographer will benefit from
organizing the identification of anatomical landmarks into specific steps. Because memorizing the structures that make up the
head and neck region can be an overwhelming task, the following system is offered to assist the beginning radiographer in
learning to identify structures commonly imaged on intraoral
radiographs (Figure 22-11).
As illustrated by the flowchart in Figure 22-11, differentiating among which structures will most likely be imaged on
intraoral radiographs of the maxilla and which structures will
1
2
3
4
FIGURE 22-9 Radiograph of mixed dentition in mandibular
canine area showing (1) primary canine, (2) primary first molar with
partially resorbed roots, (3) permanent canine, and (4) permanent first
premolar with incomplete root formation.
FIGURE 22-10 Facial bones recorded on radiographs. Note
the position of the PID when exposing a maxillary posterior
periapical radiograph. The zygomatic arch will most likely be
recorded on this radiograph.
TABLE 22-1 Radiopaque and Radiolucent
Features
RADIOPAQUE RADIOLUCENT
• Bone • Canal
• Border (wall) • Foramen
• Process • Fossa
• Ridge • Meatus
• Spine • Sinus
• Tubercles • Space (PDL)
• Tuberosity • Suture
279
• Floor of the
sinus
• Septum
• Zygomatic
process
• Zygoma
• Zygomatic
arch
• Maxillary
tuberosity
• Pterygoid
plates
• Hamulus
• Coronoid
process
Radiopaque?
• Median
palatine
suture
• Incisive
foramen
• Nasal fossa
• Lateral fossa
Radiolucent?
• Nasal septum
• Anterior
nasal spine
• Inverted “Y”
• Soft tissue of
the nose
Radiopaque?
• Lingual
foramen
• Mental fossa
Radiolucent?
• Genial
tubercles
• Mental ridge
Radiopaque?
• Maxillary
sinus
Radiolucent?
• Mental
foramen
• Submandibular
fossa
• Mandibular
canal
Radiolucent?
• Oblique ridge
• Mylohyoid
ridge
• Inferior
border of the
mandible
• Torus
mandibularis
Radiopaque?
Anterior region? Posterior region?
Maxilla?
Anterior region? Posterior region?
Mandible?
Is this a radiograph of the …?
FIGURE 22-11 Sequence for interpreting normal radiographic anatomy.
280 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
be imaged on intraoral radiographs of the mandible will help
the radiographer organize the anatomy terms and narrow the possible choices. When beginning the interpretation process, first
determine if the intraoral radiograph you are looking at is a maxillary view or a mandibular view. See Chapter 21 for generalizations that aid in determining whether or not a radiograph is of the
maxilla or the mandible. Once the correct arch is identified,
determine whether the view is of the anterior or the posterior
region. As you will recall, in the anterior regions, the image
receptor is usually positioned with the long dimension vertically,
whereas in the posterior regions the image receptor is placed
with the long dimension positioned horizontally. Certain anatomical structures are more likely to be visible on radiographs of the
anterior region, whereas others are more likely to be visible in
the posterior region. Prior to deciding which anatomical structure
is being observed, the radiographer should determine whether or
not the structure is radiopaque or radiolucent. A radiopaque
appearance indicates a structure that is dense, eliminating structures such as a foramen or fossa or other feature that would not
present as radiopaque. Likewise, a radiolucent appearance indicates a structure that is less dense, so the terms process or ridge
would not apply to radiolucent observations.
Organizing the interpretation of normal radiographic
anatomy in this manner (Figure 22-11) will assist the beginning
radiographer by providing a framework on which to learn the
terms associated with head and neck radiography and will continue to be a basis for building on these basic interpretative
skills. A working knowledge of the radiographic appearance of
normal anatomy must be mastered to develop the skills needed
to recognize deviations from the normal such as periodontal
disease, caries, and growth and development anomalies.
In keeping with the system laid out in Figure 22-11, anatomical landmarks in this chapter are separated into the regions where
they are most likely to be observed on intraoral radiographs:
1. Maxillary anterior region
2. Maxillary posterior region
3. Mandibular anterior region
4. Mandibular posterior region
Depending on the manner in which the image receptor was
positioned, and the angle at which the exposure was made, the
expected anatomical landmark may or may not be visible.
Sometimes the landmark is visible on only the right or only the
left side. Keeping this in mind, the following descriptions offer
guidance for learning these structures.
Maxillary Anterior Region (Figures 22-12
through 22-15)
RADIOPAQUE FEATURES
1. Nasal septum. A dense cartilage structure that separates the
right nasal fossa from the left. Usually appears as a vertical
radiopaque line separating the paired radiolucencies of the
nasal cavity.
2. Anterior nasal spine. A V-shaped projection from the
floor of the nasal fossa in the midline. Usually appears as a
triangle-shaped radiopacity.
1
2
3
45 6
7
8
FIGURE 22-12 Drawing of maxillary midline area illustrating
(1) outline of nose, (2) incisive foramen (anterior palatine foramen),
(3) lateral fossa, (4) nasal fossa, (5) nasal septum, (6) border of nasal
fossa, (7) anterior nasal spine, and (8) median palatine suture.
1
2
3
45 6
7
8
FIGURE 22-13 Radiograph of maxillary midline area
showing (1) incisive (anterior palatine) foramen, indicated by an
irregularly shaped, rounded radiolucent area, (2) outline of the nose,
(3) lateral fossa, (4) nasal fossa (radiolucent), (5) nasal septum,
(6) border of nasal fossa, (7) anterior nasal spine, and (8) median
palatine suture.
CHAPTER 22 • RECOGNIZING NORMAL RADIOGRAPHIC ANATOMY 281
1
2
3
4
5
FIGURE 22-14 Drawing of maxillary canine area illustrating
(1) lateral fossa, (2) nasal fossa, (3) inverted Y (intersection of the
borders of nasal fossa and maxillary sinus), and (4) maxillary sinus.
(5) Note the dense radiopaque area caused by overlapping of the
mesial surface of the first premolar over the distal surface of the
canine. This overlapping is common in this region of the oral cavity
because of the curvature of the arch.
3
4
5
2
1
FIGURE 22-15 Radiograph of maxillary canine area showing
(1) lateral fossa, (2) nasal fossa, (3) inverted Y (intersection of the
borders of the nasal fossa and maxillary sinus), (4) maxillary sinus,
and (5) dense radiopaque area caused by overlapping of the mesial
surface of the first premolar over the distal surface of the canine. This
overlapping is common in this region of the oral cavity because of the
curvature of the arch.
3. Inverted Y. An important landmark seen in the
canine–premolar area, made up of the lateral wall of the
nasal fossa and the anterior–medial wall of the maxillary
sinus. The intersection of these two radiopaque lines often
criss-cross each other in the form of the letter Y. This Y
shape often appears upside down or turned on its side.
4. Soft tissue of the nose. Sometimes an outline of the soft
tissue of the nose may be shadowed onto anterior intraoral
radiographs (Figures 22-16 and 22-17).
RADIOLUCENT FEATURES
1. Median palatine suture. A radiolucent thin line that delineates the midline of the palate and the junction of the right
and left maxillae. Frequently seen between the central
incisors, this structure should not be mistaken for a fracture.
2. Incisive foramen (anterior palatine foramen). A round
or pear-shaped radiolucent opening that varies greatly in
size serves for the passage of nerves and blood vessels. It is
often visible near or between the apices of the central
incisors. (This foramen should not be mistaken for an
abscess, cyst, or other pathological condition.)
3. Nasal fossa (cavity). A large air space divided into two
paired radiolucencies by the radiopaque nasal septum, often
visible above the roots of the incisors. The radiolucency of
FIGURE 22-16 Soft tissue of the nose in the path of the
x-ray beam. Note that the soft tissue of the nose will be in the path
of the x-ray beam in this exposure. The resultant radiograph will most
likely show an image of the soft tissue, outlining the tip of the nose.
282 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
1
FIGURE 22-17 Soft tissue image of the nose. (1) The resultant
image of the soft tissue of the nose is often magnified to a large size.
According to the rules of shadow casting (see Chapter 4), the further
an object is from the image receptor, the more likely that object will
appear magnified. The tip of the nose is at an increased distance from
the intraoral image receptor, resulting in a magnification of the size of
the nose.
FIGURE 22-18 Drawing of maxillary premolar area
illustrating (1) border (floor) of maxillary sinus, (2) maxillary sinus,
(3) septum in maxillary sinus dividing the sinus into two
compartments, (4) zygomatic process of maxilla, (5) zygoma, and
(6) lower border of zygomatic arch.
1
2 34 5
6
FIGURE 22-19 Radiograph of maxillary premolar area
showing (1) border (floor) of maxillary sinus, (2) maxillary sinus,
(3) zygomatic process of maxilla, (4) septum in maxillary sinus
dividing the sinus into two compartments, (5) zygoma, and
(6) inferior border of the zygomatic arch.
the nasal cavities will vary in dark appearance, depending on
the angle of the x-ray beam. At times, the x-ray beam may
have to penetrate the nasal conchae, thin bony extensions
of the nasal wall, and result in a less radiolucent appearance of the nasal fossa itself. (Figure 22-3)
4. Lateral fossa. A radiolucency between the maxillary lateral incisor and the maxillary canine representing the
decreased thickness in bone in this area.
Maxillary Posterior Region (Figures 22-18
through 22-22)
RADIOPAQUE FEATURES
1. Floor or inferior border of the sinuses. A thin, dense bone
indicating the walls of the maxillary sinuses, whereas the
sinus cavities themselves are referred to as radiolucent. The
term radiopaque is used when referring to the sinus walls.
The anterior extent of the maxillary sinus is often visible on
an intraoral radiograph of the canine region as well.
2. Septum. A radiopaque wall (or partition) may be seen separating the maxillary sinus into two or more compartments.
Septa (plural) are not always visible on all patients.
3. Zygomatic process of the maxilla. Appearing as a broad
U-shaped band often seen above or superimposed over the
roots of the first and second molars.
4. Zygoma (malar or cheekbone). Extends laterally and distally from the zygomatic process of the maxilla.
5. Zygomatic arch. Is continuous with the zygoma and
extends distally. Because radiographs are a two-dimensional
picture of three-dimensional structures, it is difficult to distinguish radiographically where the zygomatic process,
zygoma, and zygomatic arch end and begin.
6. Maxillary tuberosity. The extension of the alveolar bone
behind the molars marking the posterior limits of the maxillary arch. The maxillary tuberosity is usually referred to
as radiopaque; however, depending on the size of the trabeculae located here, the radiopacity will vary.
7. Pterygoid plates of the sphenoid will usually appear only
on the most posterior intraoral radiograph. To distinguish
this structure from the maxilla, look for the posterior outline of the maxilla, distal to the maxillary tuberosity. A
radiolucent suture may be detected separating the lateral
ptyergoid plate from the maxilla, or the pterygoid plate
may appear to overlap onto the maxilla.
1
2 34 5
6
CHAPTER 22 • RECOGNIZING NORMAL RADIOGRAPHIC ANATOMY 283
FIGURE 22-20 Drawing of maxillary molar area illustrating
(1) border (floor) of maxillary sinus, (2) maxillary sinus,
(3) zygomatic process of maxilla, (4) zygoma, (5) septum in
maxillary sinus, (6) lower border of zygomatic arch, (7) hamulus
(hamular process), (8) maxillary tuberosity, and (9) coronoid process
(mandible).
1
3 4
6
7
5
8
2
FIGURE 22-21 Radiograph of maxillary molar area showing
(1) border (floor) of maxillary sinus, (2) maxillary sinus,
(3) zygomatic process of maxilla, (4) zygoma, (5) lateral pterygoid
plate, (6) lower border of zygomatic arch, (7) maxillary tuberosity,
and (8) coronoid process of the mandible.
2
3 45
1
FIGURE 22-22 Radiograph of maxillary molar area showing
(1) hamulus (hamular process), a downward projection of the medial
pterygoid plate, (2) lateral pterygoid plate, (3) coronoid process of the
mandible, (4) maxillary tuberosity, and (5) maxillary sinus.
8. Hamulus (hamular process). A downward projection of
the medial pterygoid plate. It appears as a radiopaque
pointed, sometimes hooklike, structure that serves as a
muscle attachment. The hamulus is usually observed on
only the most posterior intraoral radiographs.
9. Coronoid process of the mandible is sometimes seen as a
triangle or large pointed radiopacity superimposed over the
maxillary tuberosity. Although this structure is technically
a feature of the mandible, it is often in the path of the x-ray
beam when positioning the PID for images of the maxillary posterior region (Figure 22-23).
RADIOLUCENT FEATURES
1. Maxillary sinus. This large air chamber inside the maxilla is
visible in almost all periapical radiographs from the region
of the canines posterior to the molars. The thin, radiopaque
sinus wall can be observed outlining the radiolucent sinus.
Mandibular Anterior Region (Figures 22-24
through 22-27)
RADIOPAQUE FEATURES
1. Genial tubercles. Are made up of four small, bony crests on
the lingual surface of the mandible that serve for muscle
attachments. Generally visible as a round radiopaque “doughnut” at the midline below the apices of the central incisors.
2. Mental ridge. Located on the lateral surface of the mandible,
the mental ridge appears as a horizontal radiopaque line
extending from the premolar region to the symphysis (the
midline of the mandible where the left and right sides of bone
are fused together).
RADIOLUCENT FEATURES
1. Lingual foramen. A very small circular radiolucency in
the middle of the radiopaque genial tubercles. May not be
recorded on the radiograph because of its small size.
FIGURE 22-23 Coronoid process of the mandible may be
recorded on intraoral radiographs of the maxillary posterior
region. Note the position of the image receptor holder when
exposing a maxillary posterior periapical radiograph. The coronoid
process of the mandible will most likely be recorded on this
radiograph.
1
2 3 45
6
7
8
9
284 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
1
2
3
4
5
6
FIGURE 22-25 Radiograph of the mandibular midline area
showing (1) mental ridge, (2) nutrient canal, (3) nutrient foramen,
(4) genial tubercles surrounding the (5) lingual foramen, and
(6) inferior border of the mandible (radiopaque band of dense
cortical bone).
1
2
3
4
5
6
FIGURE 22-24 Drawing of mandibular midline area
illustrating (1) mental ridge, (2) nutrient canal, (3) nutrient foramen,
(4) genial tubercles surrounding the (5) lingual foramen, and
(6) inferior border of mandible.
1
2
FIGURE 22-26 Drawing of mandibular canine area
illustrating (1) nutrient canal, and (2) torus mandibularis (lingual
torus).
1
2
FIGURE 22-27 Radiograph of mandibular canine area
showing (1) nutrient canal, (2) torus mandibularis (lingual torus).
CHAPTER 22 • RECOGNIZING NORMAL RADIOGRAPHIC ANATOMY 285
1
6
5
2
3
4
FIGURE 22-28 Drawing of mandibular premolar area
illustrating (1) torus mandibularis, (2) oblique ridge, (3) mylohyoid
ridge, (4) submandibular fossa, (5) mandibular canal, and (6) mental
foramen.
2. Mental fossa. A depression on the labial aspect of the
mandibular incisor area, representing an accentuated thinness of the mandible. On a mandibular incisor radiograph,
the mental fossa appears as a generalized radiolucent area
around the incisor apices.
Mandibular Posterior Region (Figures 22-28
through 22-32)
RADIOPAQUE FEATURES
1. Oblique ridge. A continuation of the anterior border of the
ramus that extends downward and forward on the lateral
surface of the mandible. The oblique ridge (sometimes
called the external oblique ridge) appears as a radiopaque
horizontal line of varied width superimposed across the
molar roots.
2. Mylohyoid ridge is an irregular crest of bone for muscle
attachments on the lingual surface of the mandible in the
molar region. The mylohyoid ridge appears as a horizontal
radiopaque line parallel and always inferior to (below) the
oblique ridge. The mylohyoid ridge will most likely be
imaged apical to (below) the teeth roots.
3. Inferior border of the mandible is a heavy layer of cortical bone that is imaged only if the radiograph is deeply
depressed in the floor of the mouth or the vertical angle of
the x-ray beam is excessive. The inferior border of the
mandible will appear as a distinct, thick radiopaque border.
4. Torus mandibularis (lingual torus). This bony growth
extending out from the lingual surface of the mandible is a
frequently encountered form of benign tumor. Depending
on the size of the torus, the increased thickness in the bone
will appear as a radiopaque fuzzy cotton ball imaged over
or apical to the roots of posterior teeth.
1
2
4 3
FIGURE 22-29 Radiograph of mandibular premolar area
showing (1) submandibular fossa, (2) thin radiolucent line indicating
the periodontal ligament space, (3) thin radiopaque line representing
the lamina dura, and (4) the mental foramen.
1
FIGURE 22-30 Radiograph of mandibular premolar area
showing (1) small torus mandibularis (lingual torus).
RADIOLUCENT FEATURES
1. Mental foramen. A small opening on the lateral side of
the body of the mandible, often seen near the apices of the
premolars. This foramen should not be mistaken for an
abscess, cyst, or other pathological condition.
2. Submandibular fossa. A large irregular-shaped area
below the mylohyoid ridge and the roots of the mandibular
molars, where the bone is thin, allowing more x-rays to
penentrate this area and reach the image receptor. The submandibular fossa should not be mistaken for pathology.
3. Mandibular canal. A canal for the passage of the
mandibular nerve and blood vessels, it is outlined by two
paired, thin, barely visible, parallel radiopaque lines,
which represent thin layers of cortical bone. The mandibular canal is often imaged in the premolar–molar areas
below the apices of the teeth.
286 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
1
2
3
4
FIGURE 22-32 Radiograph of mandibular molar area
showing (1) oblique ridge, (2) mylohyoid ridge, (3) mandibular canal
(note the thin, parallel radiopaque lines representing the canal walls),
and (4) submandibular fossa.
REVIEW—Chapter summary
Knowledge of the anatomical landmarks of the face and skull
is needed to properly position the image receptor to clearly
image the area of interest, to assist in mounting intraoral
radiographs, and to develop the ability to interpret radiographs
and recognize deviations from normal.
The radiographer should be able to identify cranial and
facial bones as well as the specific landmarks and features of
the maxilla and mandible. The radiographic appearance of the
alveolar bone and the structures of the teeth were presented.
For the purpose of organizing anatomical structures for
learning, landmarks are divided into the following categories,
depending on where they would be most likely to appear: maxillary anterior region, maxillary posterior region, mandibular
anterior region, and mandibular posterior region. Anatomical
landmarks are further separated into radiopaque images or radiolucent images. A systematic procedure is helpful to the beginning radiographer in learning to identify normal radiographic
anatomy.
RECALL—Study questions
1. A competent dental hygienist and dental assistant must
be able to identify which of the following radiographically?
a. Caries
b. Periodontal abcess
c. Normal anatomy
d. Periapical pathology
2. Which of the following facial bones would most likely
appear on a periapical radiograph?
a. Occipital
b. Parietal
c. Frontal
d. Zygoma
3. Bone sometimes has a mixed radiopaque-radiolucent
appearance due to the nature of the
a. cortical plates.
b. trabeculae patterns.
c. alveolar process.
d. genial tubercles.
4. Which of the following will most likely appear as a
radiopacity outlining the tooth root?
a. PDL space
b. Lamina dura
c. Nutrient canal
d. Cementum
5. When nutrient canals open at the surface of the bone,
they often appear radiographically as
a. small radiolucent dots.
b. large radiopaque lines.
c. small radiolucent lines.
d. small radiopaque dots.
6. Which of these structures appears radiolucent?
a. Enamel
b. Cementum
c. Dentin
d. Pulp
7. A periapical radiograph of a 10-year-old will most likely
reveal developing permanent dentition.
Evidence of a congenitally missing permanent tooth is
called an impaction.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
1
2
4 3
FIGURE 22-31 Drawing of mandibular molar area illustrating
(1) oblique ridge, (2) mylohyoid ridge, (3) submandibular fossa, and
(4) mandibular canal.
CHAPTER 22 • RECOGNIZING NORMAL RADIOGRAPHIC ANATOMY 287
8. On a periapical radiograph of the maxillary molars,
which of the following structures may be recorded superimposed over the roots of the teeth?
a. Mastoid process
b. Maxillary tuberosity
c. Zygomatic process
d. Mylohyoid ridge
9. Each of these features will appear radiolucent EXCEPT
one. Which one is the EXCEPTION?
a. Foramen
b. Suture
c. Canal
d. Spine
10. Each of these features will appear radiopaque EXCEPT
one. Which one is the EXCEPTION?
a. Ridge
b. Sinus
c. Tubercles
d. Process
11. Which of the following is the best recommended sequence
for learning to identify normal radiographic anatomy?
a. 1. Determine if radiograph is of the maxilla or
mandible.
2. Determine if radiograph is of the anterior or posterior region.
3. Determine if the structure is radiopaque or radiolucent.
b. 1. Determine if radiograph is of the anterior or posterior region.
2. Determine if the structure is radiopaque or radiolucent.
3. Determine if radiograph is of the maxilla or
mandible.
c. 1. Determine if the structure is radiopaque or radiolucent.
2. Determine if radiograph is of the maxilla or
mandible.
3. Determine if radiograph is of the anterior or posterior region.
d. 1. Determine if radiograph is of the maxilla or
mandible.
2. Determine if the structure is radiopaque or radiolucent.
3. Determine if radiograph is of the anterior or posterior region.
12. Each of the following may appear on a periapical radiograph of the maxillary anterior region EXCEPT one.
Which one is the EXCEPTION?
a. Nasal septum
b. Median palatine suture
c. Maxillary tuberosity
d. Inverted Y
13. Each of the following may appear on a periapical radiograph of the maxillary posterior region EXCEPT one.
Which one is the EXCEPTION?
a. Maxillary sinus
b. Incisive foramen
c. Zygomatic arch
d. Hamulus
14. A mandible landmark feature that may be imaged on a
periapical radiograph of the maxillary posterior region
is the
a. mandibular canal.
b. submandibular fossa.
c. inferior border of the mandible.
d. coronoid process.
15. Each of the following may appear on a periapical radiograph of the mandibular anterior region EXCEPT one.
Which one is the EXCEPTION?
a. Genial tubercles
b. Mental ridge
c. Coronoid process
d. Lingual foramen
16. Each of the following may appear on a periapical radiograph of the mandibular posterior region EXCEPT
one. Which one is the EXCEPTION?
a. Mental foramen
b. Pterygoid plate
c. Mandibular canal
d. Mylohyoid ridge
17. The inverted Y landmark is composed of the intersection of which two structures?
a. Lateral wall of the nasal cavity and anterior border of
the maxillary sinus
b. Anterior border of the maxillary sinus and inferior
border of the mandible
c. Lateral wall of the nasal cavity and soft tissue
shadow of the nose
d. Inferior border of the zygomatic process and the
anterior nasal spine
REFLECT—Case study
Your colleague is viewing a full mouth series of radiographs
that he just finished mounting. As he is describing the following features, see if you can tell him the name of the anatomic
landmark.
1. A dense, vertical radiopacity separating two paired oval
radiolucencies observed in the maxillary anterior region.
2. Large, paired oval radiolucencies separated by a dense,
vertical radiopacity observed in the maxillary anterior
region.
3. A thin radiolucent line resembling a fracture observed
between the maxillary central incisors.
288 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
4. A round or pear-shaped radiolucency observed between
the maxillary central incisors.
5. A broad, U-shaped radiopacity observed superimposed
over the maxillary posterior teeth roots.
6. A radiopaque downward projection of bone that
appears pointed or hooklike observed in the far posterior region of the maxilla.
7. A large triangular-shaped radiopacity observed superimposed over the maxillary tuberosity region.
8. A large radiolucency outlined by a thin radiopaque border that is observed in almost all the periapical radiographs of the maxilla, from the canine posteriorly.
9. A very small, round radiolucency observed in the midline apical (below) the mandibular incisors.
10. A horizontal radiopaque line extending from the premolar region to the symphysis.
11. A round radiolucency that resembles an abscess observed
near the apex of the mandibular second premolar.
12. A horizontal radiopaque line observed in the mandibular
posterior region, superimposed across the molar roots.
13. Another horizontal radiopaque line observed in the
mandibular posterior region, but inferior to (below) the
line described in #12 above. This line is observed inferior to the molar roots.
14. A large, irregularly shaped radiolucency observed inferior to the line described in #13 above.
RELATE—Laboratory application
Developing the ability to recognize, identify, and describe radiographic anatomy of the head and neck region takes practice.
Using the illustrations in this chapter, compare the appearance
of the structures labeled with how they appear on a dry skull.
Looking at a skull, point out each of the landmarks in the figures. To make it easier to locate these bones or structures, turn
the skull so that it is oriented in the same direction as the illustration at which you are looking. Many structures can be seen
readily; others may only be seen from one specific direction.
REFERENCES
Farman, A. G., Nortje, C. J., & Wood, R. E. (1993). Oral and
maxillofacial diagnostic imaging. St. Louis, MO: Mosby.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Identify the radiographic appearance of dental materials.
3. Identify the radiographic appearance of developmental anomalies.
4. Identify the radiographic appearance of periapical abscesses, cysts, and granulomas.
5. Identify the radiographic appearance of external and internal tooth resorption.
6. Identify the radiographic appearance of calcifications and ossifications.
7. Identify the radiographic appearance of odontogenic tumors.
8. Identify the radiographic appearance of nonodontogenic tumors.
9. Identify the radiographic appearance of fractures.
KEY WORDS
Abscess
Amalgam
Amalgam tattoo
Ameloblastoma
Anodontia
Anomaly
Base material
Benign
Carcinoma
Composite
Condensing osteitis
Crown
Cyst
Dens in dente
Dentigerous cyst
Dilaceration
Exostosis
External resorption
Follicular (eruptive) cyst
Foreign body
Fracture line
Fusion
Gemination
Globulomaxillary cyst
Granuloma
Gutta percha
Hypercementosis
Idiopathic resorption
Incisive canal cyst
Internal resorption
Recognizing Deviations
from Normal Radiographic
Anatomy
CHAPTER
OUTLINE
 Objectives 289
 Key Words 289
 Introduction 290
 Radiographic
Appearance of
Dental Restorative
Material 290
 Radiographic
Appearance of
Developmental
Anomalies 294
 Radiographic
Appearance of
Apical Disease 296
 Radiographic
Appearance of
Tooth Resorption 297
 Radiographic
Appearance of
Calcifications and
Ossifications 299
 Radiographic
Appearance of
Odontogenic
Tumors 299
 Radiographic
Appearance of
Nonodontogenic
Tumors 300
 Radiographic
Appearance of
Trauma 301
 Review, Recall,
Reflect, Relate 301
 References 302
CHAPTER
23
290 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
Introduction
The most important skill in interpreting radiographs that a dental hygienist and dental assistant can possess is the ability to recognize deviations from normal radiographic anatomy. Although
the dentist is responsible for the final diagnosis and treatment of
dental disease, all members of the oral health care team should
be able to recognize radiographic deviations from the normal.
Patient care is enhanced when the entire team views and interprets
the radiographs.
Interpretation is a skill that requires a great deal of practice.
The beginning radiology student is often frustrated by not being
able to “see” what the expert easily identifies. To help develop
this skill, a solid working knowledge of normal radiographic
anatomy is needed. The radiographer should first identify normal radiographic anatomy, then systematically progress through a
sequence of evaluation, naming each radiopaque and radiolucent
structure observed.
The purpose of this chapter is to help build on the skills
acquired in Chapter 22 and to begin to identify common radiographic features that patients often present with (Procedure
Box 23-1). These include the radiographic appearance of restorative materials, developmental anomalies, periapical pathology
and other common pathological conditions of the teeth and the
jaws, and the effects of trauma.
Prior to the discussion of the radiographic appearance of
these materials and conditions, it should be noted that interpretation of radiographic findings is enhanced when the patient is
present, allowing the practitioner to compare the radiographic
findings with the clinical examination of the patient. Attempting to determine what a particular finding is from the radiograph alone may sometimes be difficult; for example, a
radiolucency observed in the otherwise radiopaque enamel of a
maxillary central incisor may give the appearance of caries.
However, a clinical examination of this tooth may reveal the
presence of a composite restoration, which can sometimes mimic
decay radiographically. In addition, the dentist will always use
radiographs in conjunction with the patient’s clinical examination, medical and dental histories, and physical signs and symptoms, together with other necessary diagnostic tests to make a
final diagnosis.
Radiographic Appearance of Dental
Restorative Material
It is important to observe restorative materials radiographically for the presence of recurrent decay, defective margins
that contribute to periodontal disease, and other potential
problems. Restorative materials may appear radiopaque or
radiolucent, and some can be differentiated by their relative
degree of radiopacity or radiolucency (Table 23-1). Others are
better identified by their size and contour or by their probable
location on the tooth. However, because radiographs are a
two-dimensional image of three-dimensional objects, the
image of a restoration on one surface may be superimposed
on the image of another large restoration on the same tooth,
giving the appearance of only one restoration instead of two,
or even more. Often, there is more than one type of material
superimposed. For example, the appearance of a base material
may be observed apical to a metallic restoration, or the presence of metallic retention pins may be detected apical to a
crown. In addition, it is not always possible to determine on
which tooth surface the restoration is located. A restoration
looks the same whether it is on the facial (buccal) or lingual
surface of the tooth.
KEY WORDS (Continued)
Malignant
Mesiodens
Nonodontogenic cyst
Odontogenic cyst
Odontoma
Ossification
Osteosclerosis
Overhang
Periapical cemental dysplasia (PCD)
Phleboliths
Post and core
Pulp stone
Radicular cyst
Residual cyst
Resorption
Retained root
Retention pin
Rhinoliths
Sarcoma
Sclerotic bone
Sialolith
Silver point
Supernumerary tooth
Taurodontia
Torus
Tumor
PRACTICE POINT
The rule follows that when viewing radiographs, you should
give everything you see a name. Every radiopaque and radiolucent object observed on the radiograph should be identified as an anatomical landmark. Is the observation in
question the mental foramen, the submandibular fossa, or
the periodontal ligament space? When you have exhausted
all possibilities of what a finding could be, it then becomes
a deviation from the normal, requiring the attention of the
dentist.
CHAPTER 23 • RECOGNIZING DEVIATIONS FROM NORMAL RADIOGRAPHIC ANATOMY 291
1. See Procedure Box 21-2, Suggested Sequence for Viewing a Full Mouth Series of Radiographs.
2. Examine one anatomic structure at a time. Compare each finding with its appearance in adjacent
radiographs.
3. First, examine the supporting structures (the bones of the head and neck).
a. Identify each landmark (see Chapter 22).
b. Determine whether the landmark is in the appropriate region.
c. Determine whether the landmark is of accurate size and shape.
d. Examine the trabecular spaces and cortical plate of the bones.
4. Second, examine the teeth.
a. Determine if each tooth is present or absent.
b. Examine the shape and morphology of the crowns and roots.
c. Look for developmental stages and/or abnormalities.
d. Examine the pulp chamber and root canals.
5. Third, observe any dental restorations and the presence of dental materials.
a. Check for shape and contour.
b. Check for appropriate placement.
c. Look for radiolucencies that suggest recurrent decay (see Chapter 24).
6. Fourth, examine the teeth for possible carious lesions (see Chapter 24).
7. Fifth, examine the supporting alveolar bone and the periodontal ligament space for evidence of
periodontal disease (see Chapter 25).
8. Present a preliminary interpretation for the dentist’s review.
9. Following confirmation by the dentist, document all findings on the patient’s permanent record.
PROCEDURE 23-1
Sequence for interpreting a full mouth series for deviations from normal
radiographic anatomy
TABLE 23-1 Metallic and Nonmetallic Restorations
METALLIC DENTAL MATERIALS NONMETALLIC DENTAL MATERIALS
RADIOPAQUE LESS RADIOPAQUE SOMETIMES RADIOLUCENT
Amalgam Composite Composite
Gold Porcelain Acrylic resins
Stainless steel Acrylic resins Silicate
Retention pin Silicate
Post and core Base
Silver point Cement
Orthodontic appliance Temporary filling
Implants Gutta percha
Sealants
Metallic Restorations
The images of all metallic restorations of approximately equal
density appear extremely radiopaque. Therefore, it is impossible to determine whether the material is gold, silver, or a base
metal alloy. Only by looking at the size and contour of the
restoration is it possible to make an educated guess based on
what materials are generally used in such circumstances. For
example, metal crowns will most often appear to have smooth
292 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
margins, whereas amalgam restorations have irregular margins
(Figure 23-1).
Nonmetallic Restorations
Aesthetic materials, such as composites, porcelain, silicate,
and acrylic resins (plastics), may appear radiopaque or radiolucent and may be barely visible or not detected at all. Radiolucent dental materials have a tendency to mimic decay
radiographically, so some manufacturers add radiopaque particles to their product so that the viewer will not mistake it for
caries (Figure 23-2).
Other restorative materials such as base material (calcium
hydroxide pastes; Figure 23-1) and cements (Figure 23-2) exhibit
about the same degree of radiopacity as dentin. Sealants may
appear very slightly radiopaque, or not at all.
Identification of Common Restorative Materials
• Amalgam. The most common restorative material;
appears radiopaque with irregular margins and varies in
size and shape. The amalgam radiopacity observed will
most likely not cover the entire crown of the teeth; the
less radiopaque enamel cusps are often still visible. Radiographs help to image the contours of amalgam restorations and can reveal poorly contoured margins called
overhangs (Figure 23-3).
Radiographs sometime reveal particles of amalgam in the
soft tissue. Often found in edentulous areas of the mandible,
amalgam that fractures during an extraction and falls into
the root socket or under the gingival tissue may impart a
bluish-purple color to the tissue, called an amalgam tattoo
(Figure 23-4).
• Composite. Varies in appearance from radiopaque to
radiolucent. When radiolucent, composite may mimic caries
(Figure 23-2). To help distinguish composite from caries,
look for the restoration to appear to have straight margins
and a prepared look, whereas the radiolucency of caries
appears more diffuse (see Figure 24-17). A clinical examination may be needed to determine definitively whether
caries or composite is present.
• Crown (full metal). Appears radiopaque and is distinguished from amalgam by its smooth margins. Full metal
crowns usually cover the entire crown of the tooth and will
be contoured to resemble the correct shape of the cusps of
the tooth (Figure 23-1).
1
2
3
4 5
6
7
8
FIGURE 23-1 Dental materials. (1) Amalgam. (2) Porcelainfused-to-metal crown. (3) Post and core. (4) Gutta percha. (5) Base
material. (6) Full metal crown, which is the posterior abutment of a
three-unit bridge. (7) Retention pin. (8) Metal pontic (part of the
three-unit bridge).
1
2
3
4
5
FIGURE 23-2 Comparision of radiopaque and radiolucent
appearance of composite. (1) Radiopaque composite. (2)
Radiolucent composite (or acrylic resin or silicate). (3) Porcelainfused-to-metal crowns. Overexposure (darkness) of this radiograph
makes it especially difficult to view the porcelain on the left lateral
incisor. (4) However, the overexposure made it possible to image the
cement under this crown. (5) Silver point endodontic filler.
1
2
2
FIGURE 23-3 Overhang. (1) Amalgam overhang. (2) Base
material. Note the many shapes and sizes of the amalgam
restorations.
CHAPTER 23 • RECOGNIZING DEVIATIONS FROM NORMAL RADIOGRAPHIC ANATOMY 293
• Crown (porcelain-fused-to-metal). The metal core of the
crown appears radiopaque, whereas the porcelain appears
less radiopaque. The radiopaque shape of the metal core
will be more rounded than a full metal crown and is not
contoured to resemble the correct shape of the cusps of the
tooth. Instead, the porcelain will take the shape of the
cusps (Figure 23-1).
• Crown (porcelain jacket). Appears less radiopaque than a
full metal crown because no metal is present. The porcelain
material will appear to be about the same radiopacity as
dentin.
• Crown (stainless steel). As a temporary restoration, this
metal is less dense and will allow the passage of more
x-rays, giving the material a “see-through” appearance.
These crowns are prefabricated and do not appear to fit the
tooth very well (Figure 23-5).
• Retention pin. A metal pin used to support a restoration.
Retention pins appear radiopaque in a very easy-to-identify
shape (Figures 23-1 and 23-6). Because another restorative
material such as an amalgam, composite, or crown will be
placed over the retention pin, it may not be recorded on the
radiograph. It should be noted that retention pins will only
be located in the dentin and will not be observed penetrating
the pulp. A retention pin should not be confused with a post
and core restoration, which penetrates the pulp chamber and
must be observed in conjunction with an endodontic filling
material (Figures 23-1 and 23-7). These materials are
described later.
• Base material (calcium hydroxide pastes). Base materials are used to line the cavity preparation to protect the
tooth’s pulp. Because another restorative material such as
an amalgam or composite will be placed over the base, it
may not be recorded on the radiograph. When recorded,
the base material will appear very slightly radiopaque
(Figure 23-1 and Figure 23-3).
• Endodontic fillers. Radiopacities observed within the
pulp chamber may be either silver points (Figure 23-2), a
very radiopaque metal root canal filling, or gutta percha,
a less radiopaque filling (Figures 23-1 and 23-7).
• Post and core. A metal restoration that builds up a tooth so
that it can support a crown; appears radiopaque. The core
section penetrates the pulp chamber, so the presence of
endodotic filler will be observed along with a post and
core. It should be noted that in addition to location, a post
and core restoration can be distinguished from a retention
pin by its significantly larger size (Figure 23-7).
1
FIGURE 23-4 Amalgam fragment (1) embedded in the soft
tissue, probably left after an extraction. Clinically called an
amalgam tattoo because the amalgam fragment produces a bluishpurple spot on the gingiva.
1
FIGURE 23-5 Stainless steel crown (1). Note the “see-through”
appearance.
1
2
FIGURE 23-6 Retention pins. (1) Radiopaque pins help retain
the radiolucent composite restorations. (2) Small radiopaque
amalgam restorations.
294 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
• Implant. Appears as a distinct radiopacity. The implant is
located in an area of a missing tooth (Figure 23-8).
• Orthodontic and surgical materials. Metal orthodontic
bands, wires, and brackets and surgical wires, pins, and
screws all appear as distinct radiopacities (Figures 23-9
and 23-10).
Radiographic Appearance
of Developmental Anomalies
An anomaly is defined as any deviation from normal. Dental
anomalies are numerous, so it is important that the dental hygienist and the dental assistant be skilled at identifying the more
common of these. Such anomalies include the following:
• Anodontia. Absence of the teeth (may be complete or partial). The third molars are the most common congenitally
missing teeth, followed by the premolars (Figure 23-11) and
the maxillary lateral incisors. It is important when viewing
1
2
3
FIGURE 23-7 Endodontic treatments. (1) Post and core within
the root canals. (2) Gutta percha. Endodontic filling material will also
be present when a post and core restoration is observed. (3) Amalgam
restorations.
FIGURE 23-8 Implants take the shape of the missing teeth roots.
1
FIGURE 23-9 Orthodontic appliance. (1) Note the root-end
external resorption caused by trauma of orthodontic treatment.
2
1
FIGURE 23-10 Surgical materials. (1) Surgical wire used to
treat a fractured mandible. (2) Mandibular fracture indicated by
the radiolucent line.
CHAPTER 23 • RECOGNIZING DEVIATIONS FROM NORMAL RADIOGRAPHIC ANATOMY 295
radiographs of children that the presence of the developing
permanent teeth be noted.
• Supernumerary teeth (extra teeth). It is equally important
that the presence of supernumerary teeth be detected.
(Figure 23-12) Often there is not a space for these extra teeth
to erupt into, or the radiopacities may be deformed and not
resemble normal tooth form. Complications caused by supernumerary teeth include the possibility of cyst formation and
the malposition, noneruption, or both of the normal teeth.
• Mesiodens. A supernumerary tooth located in the maxillary midline (Figure 23-13).
• Dens in dente (dens invaginatus). Literally, a tooth within
a tooth, an invagination of the enamel within the body of
the tooth. This anomaly occurs most frequently in the maxillary lateral incisor (Figure 23-14).
• Hypercementosis. Usually appears radiopaque and is
caused by excessive cementum formation. The excessive
cementum on the roots often causes a bulbous enlargement
along the root surface, with the area near the apex appearing most bulbous (Figure 23-15). Hypercementosis is
distinguished from radiopacities surrounding or near the
tooth roots by the outline of the periodontal ligament
(PDL) space. When observing hypercementosis, the PDL
contains the radiopacity and separates it from the bone.
3 2
1
FIGURE 23-11 Congenitally missing tooth. (1). Second
premolar did not develop under this primary molar. (2) Severe caries.
(3) Severe caries.
1
FIGURE 23-12 Supernumerary tooth. (1). Impacted
supernumerary premolar.
1
FIGURE 23-13 Mesiodens. (1) A small supernumerary tooth,
located in the midline between the central incisors.
1
FIGURE 23-14 Dens in dente. (1) An invagination of the enamel
within the body of the lateral incisor.
296 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
This distinction will help to avoid mistaking hypercementosis for sclerotic bone, explained later.
• Dilaceration. When the tooth root is misshapen with a
sharp bend. (Figure 23-16).
• Taurodontia. Characterized by an elongated pulp chamber
and very short roots.
• Gemination (twinning). A single tooth bud that divides and
forms two joined teeth. The presence of adjacent teeth helps
to distinguish this condition from fusion.
• Fusion. A condition where the dentin and one other dental
tissue of adjacent teeth are united (Figure 23-17). In this case,
two adjacent teeth will be involved, distinguishing fusion
from gemination.
Radiographic Appearance of Apical
Disease
Radiolucencies surrounding the apices or root tips of the teeth
indicate pathological changes in the hard (bony) tissues. These
radiolucenies cannot usually be distinguished from each other
based on the radiographic image alone. The appearance of apical pathology on a radiograph must be carefully correlated with
other assessment information before a diagnosis can be made.
The three most common periapical lesions observed on radiographs are abscess, granuloma, and cyst (Figure 23-18).
• Periapical abscess. Periapical infections usually result
from pulpal inflammation. Bacteria from caries infect
the pulp and gain access to the periapical bone by way of
the root canals. As a rule, an acute abscess (early stage
of pulpal or periapical infection) is barely discernible
1
FIGURE 23-15 Hypercementosis. (1) Overgrowth of
cementum on the roots of the molar.
2 1
FIGURE 23-16 Dilaceration. (1) A sharp bend in the root of the
second premolar. (2) Torus palatinus, a radiopaque benign
overgrowth of bone on the midline of the palate.
1
FIGURE 23-17 Fusion. (1) Two joined adjacent incisors.
1
2
FIGURE 23-18 Periapical pathology. (1) Caries on the distal
surface of the left central incisor. (2) Round radiolucent lesion that
may be a periapical abscess, a granuloma, or a cyst.
CHAPTER 23 • RECOGNIZING DEVIATIONS FROM NORMAL RADIOGRAPHIC ANATOMY 297
radiographically, becoming more radiolucent as it
becomes chronic. In fact, in the very early acute stage there
may be no radiographic evidence at all. The earliest sign
may be a break, or loss of radiopacity, in the lamina dura.
A chronic abscess may appear as a circular radiolucency
around the root apices and eventual turn into a granuloma.
• Granuloma. A mass of granulation tissue usually surrounded by a fibrous sac continuous with the periodontal
ligament space that appears attached to the root apices.
Under certain conditions, epithelial elements may proliferate to form a cyst.
• Cyst. Epithelium-lined sac filled with fluid or semisolid
material. The periapical cyst (also known as a radicular
cyst) is a cyst around the end of the tooth root. Unless the
cyst is completely removed at the time of the extraction or
surgery, it will remain and is then called a residual cyst.
Because of osmotic imbalance within a cyst, pressure is
exerted in all directions; therefore, cysts tend to be spherical
unless unequal resistance is encountered. Although usually
unilocular (made up of one compartment), cysts may also be
multilocular (made up of several compartments). Radiographically, a cyst may appear as a fairly uniform radiolucent cavity within the bone and surrounded by a well-defined
radiopaque border that resembles the lamina dura.
A dentigerous or follicular cyst (Figure 23-19) is associated with impacted or unerupted teeth—most often third molars
and supernumerary teeth—and is always associated with the
1
2
3
FIGURE 23-19 Dentigerous cyst (1) involving (2) the impacted
third molar. (3) Note the expansion and thinning of the cortical bone
of the mandible in response to the cyst. (The image receptor was
purposely placed in a vertical position instead of the usual horizontal
position to better record this condition.)
crown only of the involved tooth. If the tooth causing the cyst
continues to develop and is able to erupt, the cyst is often
destroyed by natural means (Figure 23-20).
Periapical, residual, and dentigerous cysts are categorized
as odontogenic cysts, which means of tooth origin.
Nonodontogenic cysts arise from epithelium other than that
associated with tooth formation. Two types of nonodontogenic
cysts are the incisive canal (nasopalatine) cyst (Figure 23-21),
located within the incisive canal, and the rare globulomaxillary
cyst (Figure 23-22), which arises between the maxillary lateral
incisor and the canine.
Radiographic Appearance of Tooth
Resorption
Evidence of tooth resorption is a common finding on dental
radiographs. Natural physiologic resorption, such as when the
roots of primary teeth resorb in response to the erupting permanent teeth, is considered normal (Figure 23-20). Other resorptive processes, however, are the result of infection, trauma, or
some unusual condition. Tooth resorption may be external or
internal. External resorption is most often characterized by
root-end resorption, where the roots of the teeth appear shorter
than normal (Figure 23-23). External resorption is not limited
to the root end, but can occur anywhere along the tooth root.
Other examples of external resorption include the resorption
caused by pressure from an adjacent impacted or unerupted
tooth; resorption caused by slowly growing tumors; or trauma,
such as when teeth are moved too rapidly during orthodontic
treatment (Figure 23-9). When the resorption cause is unknown,
it is called idiopathic resorption.
2
3 4
5
1
FIGURE 23-20 Follicular cyst (1) surrounds the crown of
the unerupted second premolar. (2) Incipient caries on the first
permanent molar. (3) Advanced caries on the primary second molar.
(4) Erupting second premolar. (5) Primary first molars about to be
exfoliated. Note the physiologic external resorption of the primary
roots.
298 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
Internal resorption typically appears as a radiolucent
widening of the root canal, representing the resorption process
taking place from the inside out (Figure 23-24).
Although not classified as resorption, but often undergoing a resorption process, are retained root fragments that
may be observed on radiographs of an edentulous area
(Figure 23-25). These structures may have broken off the
tooth and were left behind following extraction or remain as
the result of severe decay or trauma that broke off the crown
of the tooth, leaving behind the root. The patient did not seek
dental tratment for the condition, and the root tip remained.
Retained root tips may be clearly visible radiographically or
less so, depending on their size and degree of resorption.
FIGURE 23-21 Incisive canal cyst. Arrows outline an incisive
canal (nasopalatine) cyst in an edentulous maxilla.
FIGURE 23-22 Globulomaxillary cyst. Arrows outline a
globulomaxillary cyst between the maxillary lateral incisor and the
canine.
1
FIGURE 23-23 External resorption. (1) Idiopathic resorption of
the distal root of the first molar.
1
FIGURE 23-25 Retained root (1) fragment in an
extraction site.
1
FIGURE 23-24 Internal resorption. (1) Idiopathic resorption
noted as the widening of the pulp chamber.
CHAPTER 23 • RECOGNIZING DEVIATIONS FROM NORMAL RADIOGRAPHIC ANATOMY 299
Radiographic Appearance of Calcifications
and Ossifications
Calcifications in the dental pulp occur in the form of small nodules called pulp stones (Figure 23-26). These appear as
radiopaque ovoid structures of varied size. Pulp stones are very
common but of little significance, unless root canal therapy is
needed on the affected tooth.
Other less frequently encountered calcifications are sialoliths,
depositions of calcium salts in the salivary glands and ducts
(Figure 23-27); rhinoliths, stones within the maxillary sinuses;
and phleboliths or calcified thrombi, calcified masses that are
observed as round or oval bodies in the soft tissues of the
cheeks.
Two forms of ossification (the conversion of structures into
hardened bone) are often imaged on radiographs. Condensing
osteitis occurs when sclerotic (hardened) bone is formed as a
result of infection (Figure 23-28). The increased radiopacity
of the bone is often accompanied by an increased widening
(radiolucency) of the periodontal ligament space. Osteosclerosis
occurs when regions of abnormally dense bone form, but not as
a direct result of infection (Figure 23-29). Although the cause is
unknown, osteosclerosis commonly occurs in the interseptal
premolar area and may be associated with fragments of retained
primary roots.
1
FIGURE 23-26 Pulp stones. (1) Ovoid radiopaque calcifications
observed in the pulp chambers.
1
FIGURE 23-27 Sialolith (1) in a salivary gland. Note the
edentulous mandible.
1
FIGURE 23-28 Condensing osteitis. (1) Radiopaque, sclerotic
(hardening of) bone.
1
FIGURE 23-29 Osteosclerosis. (1) Diffuse idiopathic
osteosclerosis.
Radiographic Appearance of Odontogenic
Tumors
Odontogenic tumors result from abnormal proliferation of cells
and tissues involved in odontogenesis (the formation of the
teeth). The three types occasionally seen on radiographs are
ameloblastomas, odontomas, and periapical cemental dysplasia (PCD). Ameloblastomas have the greatest potential for
serious implications for the patient. These appear as large radiolucencies of enamel origin. Radiographically, ameloblastomas
may be monolocular (one compartment) or multilocular (many
compartments). The monolocular form closely resembles a
dentigerous cyst (Figure 23-30). The multilocular form has a
characteristic “soap bubble” appearance.
Odontomas are the most common ondontogenic tumors
(Figure 23-31). These are tumors of small misshaped teeth
whose number in each odontoma varies widely. These toothlike
structures appear radiopaque and are located within a radiolucent fibrous capsule that often resembles a cyst.
Periapical cemental dysplasia (PCD), sometimes called
cementomas, is a bone dysplasia derived from the periodontal
300 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
1
2
FIGURE 23-30 Ameloblastoma. (1) Large radiolucency.
(2) Resorption of the molar roots caused by pressure of the tumor.
1
FIGURE 23-31 Odontoma. (1) Consisting of small, misshaped
teeth located within a radiolucent fibrous capsule.
1
2
FIGURE 23-32 Periapical cemental dysplasia (PCD).
(1) Early PCD (radiolucent). (2) Late stage of development
(radiopaque). The teeth are vital.
ligaments of fully developed and erupted teeth. Early PCD is
radiolucent and appears identical to radicular cysts. In the later
stages of development, PCD appears as radiopaque masses surrounded by a radiolucent line (Figure 23-32). PCD occurs more
frequently in middle-aged females than males. The teeth are
vital, and the condition needs no treatment. Radiographic Appearance
of Nonodontogenic Tumors
The majority of tumors found in the head and neck region do
not have a characteristic radiographic appearance that enables a
diagnosis from the radiograph alone. In fact, a diagnosis of a
tumor cannot be made until the dentist, the pathologist, and the
radiologist have combined their findings. However, the oral
health care professional may be the first to detect the presence
of a lesion and make the appropriate referral.
Tumors are classed as benign (doing little or no harm) and
malignant (very dangerous or life threatening). Fortunately,
most tumors detected in the oral health care practice are benign.
Careful examination of the radiograph can often help to differentiate benign from malignant lesions.
Benign tumors may be either radiolucent or radiopaque, with
well-defined margins. Malignant tumors tend to have irregular
margins and are less distinct, blending into the adjacent bone.
Exostoses and tori are the most frequently encountered
forms of benign tumors. An exostosis is a localized overgrowth
of bone. The term torus (plural tori) is often used to describe an
exostosis that occurs near the midline of the palate (torus palatinus; Figure 23-16) and on the lingual surface of the mandible
(torus mandibularis; see Figures 22-26 and 22-27). Radiographically, both appear as an area of increased radiographic
density (radiopaque).
The two main types of oral malignancies are carcinoma
and sarcoma. Both grow rapidly and spread into adjacent tissues. Carcinomas are malignant tumors of epithelial origin, and
sarcomas are malignant tumors of connective tissue origin. The
CHAPTER 23 • RECOGNIZING DEVIATIONS FROM NORMAL RADIOGRAPHIC ANATOMY 301
radiographic appearance of these tumors is radiolucent, with
irregular and poorly defined borders. Sarcomas often have a
“patchy” appearance with no demarcation from normal surrounding bone. Radiographs are vitally important in early
detection because sarcomas produce changes in bone early in
their development.
Radiographic Appearance of Trauma
The two most common injuries observed on dental radiographs
are fractures of facial bones and teeth. Fracture lines are thin
radiolucent lines that demarcate the region of bone or tooth separation (Figure 23-10). Fractures may on occasion have a similar appearance to the nutrient canals described in Chapter 22.
Radiographs will sometimes reveal the presence of foreign
bodies. Note the broken dental instrument imaged in Figure 23-33.
REVIEW—Chapter summary
The dental hygienist and dental assistant should possess the ability to recognize deviations from the normal. Developing this skill
requires practice. Although identifying deviations from the normal radiographically is important, a diagnosis cannot be made
from the radiograph alone. Common radiographic observations
that the dental hygienist and dental assistant should be able to
identify radiographically include the appearance of restorative
materials, developmental anomalies, periapical pathology and
other pathological conditions, and the effects of trauma.
Metallic restorative materials such as amlagam, metal
crowns, retention pins, post and core, and silver points appear
radiopaque and are distinguished from each other by their size
and shape. Nonmetallic restorative materials such as composite,
porcelain, base material, and gutta percha appear less radiopaque
than metal. Composite materials, may appear slightly radiopaque
or radiolucent.
Developmental anomalies that may be recorded on radiographs
include anodontia, supernumerary teeth, mesiodens, dens in dente,
hypercementosis, dilaceration, taurodontia, gemination, and fusion.
Periapical abscesses, granulomas, and cysts all appear
radiolucent and cannot be distinguished from each other radiographically.
Radiographs may record external and internal tooth
resorption. Radiographic evidence of calcifications and ossifications include pulp stones, sialoliths, rhinoliths, phleboliths,
condensing osteitis, and osteosclerosis.
Although tumors may not be diagnosed from radiographs
alone, the presence of ameloblastomas, odontomas, periapical
cemental dysplasia (PCD), and benign and malignant tumors
may be detected radiographically.
Fractures of the tooth and bone and foreign objects may be
detected radiographically.
RECALL—Study questions
1. Amalgam and a full metal crown can be distinguished
from each other radiographically by their
a. degree of radiopacity.
b. shape and margins.
c. location in the mouth.
d. use of retention pins.
2. Which of these dental restorative materials appears
most radiopaque?
a. Amalgam
b. Porcelain
c. Silicate
d. Acrylic resin
3. Which of these dental restorative materials is most
likely to mimic decay radiographically?
a. Gold
b. Stainless steel
c. Amalgam
d. Composite
4. Dens in dente appears radiographically as a
a. Tiny tooth.
b. Large tooth.
c. Twin tooth.
d. Tooth within a tooth.
5. A sharp bend in the tooth root is called
a. taurodontia.
b. hypercementosis.
c. dilaceration.
d. exostosis.
6. Radiographically, it is not possible to accurately differentiate between a periapical abscess, a granuloma, and a cyst.
Radiographically, it is not possible to accurately differentiate between carcinoma and sarcoma.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
1
FIGURE 23-33 Foreign object. (1) Broken dental bur, which
probably lodged here when it was used during removal of the
third molar.
302 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
7. Which of these appears radiolucent on a radiograph?
a. Sialolith
b. Abscess
c. Torus
d. Odontoma
8. A large radiolucency surrounding the crown only of an
unerupted tooth is most likely what type of cyst?
a. Dentigerous
b. Radicular
c. Residual
d. Periapical
9. The evidence of resorption that appears to shorten the
tooth root is called
a. internal resorption.
b. external resorption.
c. primary resorption.
d. secondary resorption.
10. The radiographic appearance of a small ovoid radiopacity within the pulp chamber of the tooth is called a
a. rhinolith.
b. phlebolith.
c. pulp stone.
d. pulp cap.
11. Which of the following appears radiolucent in its early
stages and as a radiopaque mass in later stages?
a. Condensing osteitis
b. Periapical granuloma
c. Osteosclerosis
d. Periapical cemental dysplasia (PCD)
12. Which of the following tumors appears radiolucent
radiographically?
a. Torus palatinus
b. Odontoma
c. Sarcoma
13. Radiographic evidence of a bone fracture appears as a
radiolucent line that may resemble a
a. nutrient canal.
b. cyst.
c. tumor.
d. retained root tip.
REFLECT—Case Study
You have just accepted a position in a large oral health care
clinic at a university-based dental school, where your primary
role will be to process, mount, and prepare a preliminary interpretation of full mouth series of radiographs taken on incoming
patients. You know how valuable it is to follow a systematic
order when mounting films, so you decide to apply an orderly
system to interpreting the radiographs as well.
Design a form that will guide you and other radiographers
through the interpretive process. Your form should include the
following:
1. A place to record basic information (the patient’s name,
date the radiographs were exposed, name of the person
interpreting the radiographs, date of interpretation,
etc.).
2. A step-by-step guide for where to begin and end the
interpretive process.
3. A list of common conditions or deviations from normal
that you will be looking for. (Organize the conditions
you will be interpreting logically.)
4. Organize the conditions according to what you will
examine the radiographs for first, second, third, etc.
5. Prepare columns, rows of boxes, or whatever your
design requires as a place to record or list the condition.
6. Label the columns, rows of boxes, or whatever your
design uses, with the appropriate headings.
7. Prepare a place to document that the condition needs a
referral to the dentist.
8. Prepare your form in such a manner that other professionals may be able to utilize the form. Prepare written
instructions for utilizing the form as needed.
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson. Chapter 14, “Radiographic interpretation.”
REFERENCES
Farman, A. G., Nortje, C. J., & Wood, R. E. (1993). Oral and
maxillofacial diagnostic imaging. St. Louis, MO: Mosby.
Hatrick, C. D., Eakle, W. S., & Bird, W. F. (2010). Dental
materials: Clinical applications for dental assistants and
dental hygienists (2nd ed.). St. Louis, MO: Elsevier.
Langlais, R. P. (2003). Exercises in oral radiology and interpretation (4th ed.). Philadelphia: Saunders.
Langlais, R. P., Langland, O. E., & Nortje, C. J. (1995).
Diagnostic imaging of the jaw. Philadelphia: Williams &
Wilkins.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Explain why caries appear radiolucent on radiographs.
3. Define the role radiographs play in detecting caries.
4. Identify the ideal type of projection, technique, and exposure factors that enhance a radiograph’s ability to image caries.
5. List and describe the four categories of the caries depth grading system.
6. List the four locations of dental caries and identify their radiographic appearance.
7. Define and identify the radiographic appearance of recurrent dental caries.
8. List three conditions that resemble dental caries radiographically and discuss how to distinguish
these from caries.
KEY WORDS
Advanced caries
Arrested caries
Buccal caries
Caries
Cemental (root) caries
Cementoenamel junction (CEJ)
Cervical burnout
Dentinoenamel junction (DEJ)
Incipient (enamel) caries
Interproximal
Interproximal caries
Lingual caries
Mach band effect
Moderate caries
Nonmetalic restoration
Occlusal caries
Proximal caries
Rampant caries
Recurrent (secondary) caries
Severe caries
The Use of Radiographs
in the Detection
of Dental Caries
CHAPTER
OUTLINE
 Objectives 303
 Key Words 303
 Introduction 304
 Dental Caries 304
 Interpreting
Dental Caries 306
 Caries Depth
Grading System 306
 Classification of
the Radiographic
Appearance of
Caries 306
 Conditions
Resembling
Caries 309
 Review, Recall,
Reflect, Relate 311
 References 313
CHAPTER
24
304 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
FIGURE 24-1 Proximal surface caries found just apical to the
contact area between two adjacent teeth.
Introduction
The detection of caries (tooth decay) is probably the most common reason for exposing dental radiographs. The dental hygienist or dental assistant who is skilled in identifying normal
radiographic anatomy should be able to differentiate between the
appearance of normal tooth structures and dental caries on a
radiograph.
The purpose of this chapter is to describe the radiographic
appearance of dental caries, identify a caries depth grading system, and offer some tips that may influence caries interpretation
(Procedure Box 24-1).
Dental Caries
Description
Dental caries, or tooth decay, is a pathological process consisting of localized destruction of dental hard tissues by organic
acids produced by microorganisms. The caries process is one of
demineralization of tooth structure (enamel, dentin, cementum).
This demineralization of tooth density allows more x-rays to
pass through the tooth and darken the image. Therefore, caries
appear radiolucent on the radiograph (Figure 24-1).
Detection
Radiographs reveal carious lesions that may go undetected clinically, especially caries on the proximal surfaces (in between the
teeth; Table 24-1). To be a useful diagnostic aid, the radiographs
must be precisely exposed and meticulously processed. Improper
angulation can render a radiograph worthless for caries detection. Incorrect vertical angulation may prevent the radiograph
PROCEDURE 24-1
Radiographic interpretation for caries
1. See Procedure Box 21-2, Suggested Sequence for Viewing a Full Mouth Series of Radiographs.
2. View all surfaces of each tooth.
3. Examine the contact points and just apical to the estimated gingival margin (soft tissue will not be imaged on
the radiograph) for radiolucencies indicating proximal caries.
4. Examine the dentin just apical to the occlusal enamel for radiolucencies indicating occlusal caries.
5. Examine the dentin in the middle of the tooth for a round radiolucency indicating buccal/facial or lingual caries.
6. If there is bone loss and evidence that cementum is exposed in the oral cavity, examine the cervical region of the
tooth for an ill-defined, radiolucent crescent-shaped area below the cementoenamel junction (CEJ) indicating
cemental (root) caries.
7. Examine existing restorations for recurent decay.
8. Confirm findings and/or clarify uncertain interpretations with a clinical examination of the patient.
9. Consult the patient’s chart for confirmation or clarification of findings as needed.
10. Present a preliminary interpretation for the dentist’s review.
11. Following confirmation by the dentist, document all findings on the patient’s permanent record.
from imaging caries (Figure 24-2). The horizontal angulation is
particularly important. Overlapping of the contact areas between
the teeth will make it impossible to detect caries in these areas
(Figure 24-3).
The bitewing radiograph, described in Chapter 16, is the
radiograph of choice for the evaluation of caries due to the precise parallelism established between the tooth and the plane of
the image receptor. However, a precisely placed periapical radiograph exposed using the paralleling technique will adequately
image dental caries (Figure 24-4).
Although the exposure factors (mA, kVp, and time) used
will depend on the patient and the area to be exposed, some
CHAPTER 24 • THE USE OF RADIOGRAPHS IN THE DETECTION OF DENTAL CARIES 305
TABLE 24-1 Radiographic Appearance of Caries
GRADE SEVERITY PROXIMAL OCCLUSAL BUCCAL/LINGUAL CEMENTAL
C-1 Incipient Radiolucent notch in the enamel
only. Radiolucency is less than
halfway through the enamel.
Not evident
radiographically.
Not evident
radiographically.
Not applicable.
C-2 Moderate Radiolucent triangle with the
apex pointing toward the DEJ.
Radiolucency is more than
halfway through the enamel,
but does not invade the DEJ.
Not evident
radiographically.
Not evident
radiographically.
Not applicable.
C-3 Advanced Radiolucency takes on a double
triangle shape, first through the
enamel with the apex pointing
toward the DEJ and a second
triangle base spreading along
the DEJ with the apex pointing
toward the pulp. Radiolucency
is less than halfway through
the dentin toward the pulp.
Flat radiolucent line, often
with no or little change
detected in the enamel.
Radiolucency is less
than halfway through the
dentin toward the pulp.
Not possible to distinguish advanced
from severe. Both
appear as a round
radiolucency in the
middle of the tooth
with well-defined
borders.
Although enamel is not
involved in this type of
caries, at this stage an
ill-defined, radiolucent,
cresent-shaped area
below the cementoenamel junction (CEJ)
may be observed. Bone
loss must be evident.
C-4 Severe Radiolucency may retain a double triangle shape, or be so
severe as to appear as a large
diffuse radiolucency.
Radiolucency is more than
halfway through the
dentin toward the pulp.
Large radiolucency detected
in the dentin below the
occlusal enamel. Depending on the extent of destruction, radiolucent breaks in
the occlusal enamel may be
imaged. Radiolucency is
more than halfway through
the dentin toward the pulp.
Not possible to distinguish advanced from
severe. Both appear
as a round radiolucency in the middle
of the tooth with
well-defined
borders.
Although enamel is not
involved in this type of
caries, at this stage an
ill-defined, radiolucent,
crescent-shaped area
below the cementoenamel junction (CEJ)
may be observed. Bone
loss must be evident.
2
1
FIGURE 24-2 Vertical angulation. (1) Excessive vertical
angulation prevents viewing this proximal surface carious lesion.
(2) Proper vertical angulation shows the proximal surface caries.
Note the difference in alveolar bone crest heights between the two
radiographs indicating a change in the vertical angulation.
1
2
3
FIGURE 24-3 Horizontal angulation. (1) Incorrect horizontal
angulation causes overlapping between adjacent teeth, which prevents
viewing for interproximal caries. (2) Improved horizontal angulation,
but caries difficult to view. (3) Correct horizontal angulation clearly
images caries.
practitioners prefer to use a lower kVp to best image caries.
A low setting, such as 60 kVp (with direct current x-ray equipment), will result in a high-contrast image: black and white with
few shades of gray in between. Because caries appear radiolucent against a radiopaque enamel (or lesser radiopaque dentin),
a high-contrast image is preferred by some practitioners for
imaging carious lesions.
306 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
Interpreting Dental Caries
Dental caries is a process of decalcification and requires 40 to
50 percent loss of calcium and phosphorus before the
decreased density can be seen on a radiograph. For this reason,
the depth of penetration of a carious lesion is deeper clinically
than it appears on the radiograph. Also, because the proximal
surfaces of posterior teeth are broad, the loss of small amounts
of mineral from incipient lesions may be difficult to see on the
radiograph (Figure 24-5).
Caries Depth Grading System
Several systems are used to grade the depth of penetration of
caries. This text will use a grading system suggested by Haugejorden and Slack, 1977 (Figure 24-6). The advantage of this
system is that it allows one to accurately grade the penetration
of caries (establish a baseline) and to track the progression
FIGURE 24-4 Periapical radiograph records proximal
surface caries.
X-ray A X-ray B
FIGURE 24-5 Drawing showing ratio of caries to enamel.
X-ray A passing through a small ratio of caries to enamel, resulting
in the caries being difficult to view. X-ray B passing through a large
ratio of caries to enamel, results in the caries being easier to view.
and/or remineralization of the carious lesions at future appointments. These grades may also be called incipient, moderate,
advanced, or severe.
• C-1: Enamel caries, also called incipient caries (meaning
the first stage of existence), penetrate less than halfway
through the enamel of the tooth toward the dentinoenamel
junction (DEJ) (Figure 24-6, 1).
• C-2: Moderate caries, penetrating over halfway through
the enamel toward the dentinoenamel junction (DEJ), but
not reaching the DEJ. Moderate caries are only seen in the
enamel (Figure 24-6, 2).
• C-3: Advanced caries are of enamel and dentin at or through
the dentinoenamel junction (DEJ), but less than halfway
through the dentin toward the pulp (Figure 24-6, 3). Advanced
caries are seen in both the enamel and dentin.
• C-4: Severe caries are of enamel and dentin penetrating
over halfway through the dentin toward the pulp (Figure
24-6, 4). Severe caries are seen in both the enamel and the
dentin.
Classification of the Radiographic
Appearance of Caries
The radiographic appearance of caries may be classified according to their location on the tooth.
1 2
3
3
3
4
FIGURE 24-6 Diagram of classification of dental caries
recommended by Haugejorden and Slack. (1) C-1 caries. Less
than halfway through the enamel (incipient caries). (2) C-2 caries.
Penetrate over halfway through the enamel (moderate caries).
(3) C-3 caries. At or through the dentinoenamel junction (DEJ), but
less than halfway through the dentin toward the pulp (advanced
caries). (4) C-4 caries. Penetrate over halfway through the dentin
toward the pulp (severe caries).
CHAPTER 24 • THE USE OF RADIOGRAPHS IN THE DETECTION OF DENTAL CARIES 307
There are four locations on the tooth that caries occur:
1. Proximal (mesial and distal)
2. Occlusal
3. Buccal/lingual
4. Cemental (root surface)
Caries may be categorized as recurrent, rampant, or arrested.
Radiographs are often prescribed to detect proximal surface caries. Occlusal, buccal/lingual, and cemental caries are
more readily detected clinically than with radiographs. In fact,
early (incipient and moderate) occlusal, buccal/lingual, and
cemental caries often do not show up on radiographs, even
though these may be detected clinically. However, moderate
and severe occlusal, buccal/lingual, and cemental caries will
appear radiographically, so it is important that the radiographer
recognize these.
Proximal Caries
Interproximal means between two adjacent surfaces. On dental
radiographs, proximal surface caries, often referred to as
interproximal caries, are located on the tooth surface that
contacts the adjacent tooth. The interproximal is an area that is
almost impossible to examine clinically, making the use of
radiographs vitally important in caries detection. The tooth
surface should be examined for caries at the point of contact
and just apical to this point of contact to the gingival margin
(Figure 24-7). The location of the height of the gingival margin, which is soft tissue, is not imaged on the radiograph. So
the gingival margin location is estimated based on where the
alveolar bone crest height is imaged. Assume that the gingival
margin will be located at least 1 mm above the level of bone
imaged on the radiograph.
The shape of proximal caries begins as a radiolucent notch
on the enamel (C-1; Figure 24-6, 1). As the demineralization of
enamel progresses, caries takes on a triangular shape (like a
pyramid) with the apex pointing toward the dentinoenamel
junction (DEJ) and the base toward the outer surface of the
Free gingival
margin
bone
FIGURE 24-7 Drawing indicating the area to examine for interproximal caries. View the area where two
adjacent teeth contact, and apical down to where the gingival margin would most likely be (boxed area). Avoid
mistaking caries in the region apical to the gingival margin, where the optical illusion cervical burnout is most
likely to be appear.
tooth (C-2; Figure 24-6, 2). At the DEJ the caries spreads,
undermining normal enamel, and again takes on a triangular
shape as it penetrates toward the pulp (C-3; Figure 24-6, 3).
The base of this second triangle is along the DEJ and the apex
points toward the pulp (C-4; Figure 24-6, 4).
Occlusal Caries
Occlusal caries are located on the chewing surface of the posterior teeth. Because of the superimposition of the buccal and
lingual cusps, occlusal caries in early stages (incipient and
moderate) may not be imaged on a radiograph (Figure 24-6, 3,
and Figure 24-8), even when a clinical examination does detect
incipient or moderate occlusal caries.
After occlusal caries has reached the DEJ (advanced caries),
it may be imaged on the radiograph (Figures 24-9 and 24-10). At
the DEJ occlusal caries will appear as a flat radiolucent line.
Often no or little change is detected in the enamel radiographically at this stage. As demineralization progresses, the size of the
radiolucency increases. It is important to note that when examining radiographs for occlusal caries, the area of interest is below
FIGURE 24-8 Drawing of occlusal caries, early stage. Early
occlusal caries (C-1 and C-2) extend along the dentinoenamel
junction (DEJ) and may not be seen on the radiograph, even though
the lesion may be detected clinically.
308 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
FIGURE 24-9 Drawing of advanced occlusal caries. Advanced
(up to halfway toward the pulp) or severe occlusal caries (more than
halfway toward the pulp) will most likely be imaged radiographically.
the occlusal enamel, in the area of the dentin, and not from the
top of the tooth. The irregularity of the cusps and occlusal surface pits and fissures do not usually indicate the presence of
caries. Changes (radiolucencies) in the dentin below the occlusal
enamel are indicative of occlusal caries. As advanced caries
progress to a severe stage, changes in the occlusal enamel are
more likely to be imaged as the crown of the tooth begins to
break down.
Buccal and Lingual Caries
Buccal caries involves the buccal or facial surface of a tooth,
and lingual caries involves the lingual surface (Figure 24-11).
Buccal and lingual caries are best detected clinically. Early buccal
and lingual carious lesions are almost impossible to detect radiographically. This is due to the superimposition of the normal
tooth structures over the caries. As the demineralization becomes
severe, the caries appears as a radiolucency characterized by welldefined borders, often described as looking into a hole on the radiograph (Figure 24-12). However, because the radiograph is a
two-dimensional image of three-dimensional structures, it is
1
FIGURE 24-10 Radiograph of occlusal caries. (1) Severe
occlusal caries appearing as a large radiolucent lesion in the first
molar.
FIGURE 24-11 Drawing of buccal or lingual caries.
Advanced buccal or lingual caries have well-defined borders.
FIGURE 24-12 Radiograph of buccal or lingual caries on this
mandibular second premolar appears as a round radiolucency
(superimposed over the pulp chamber).
impossible to tell the depth of buccal or lingual caries or the relationship to the pulpal tissue.
Cemental (Root) Caries
Cemental caries (also known as root caries) develop between
the enamel border and the free margin of the gingiva on the
cemental surface (Figure 24-13). Bone loss and recession of
the gingival tissue are necessary for the caries’ process to start
on the root surfaces. Cemental caries may appear on the buccal, lingual, mesial, or distal surface of the tooth.
Radiographically, cemental caries appear as an ill-defined,
radiolucent, crescent-shaped area just below the cementoenamel junction (CEJ; Figure 24-14). Cemental caries may at
times be misinterpreted as cervical burnout (discussed later in
this chapter), an optical illusion of the radiographic image.
Cemental caries are more easily detected clinically than radiographically.
Recurrent (Secondary) Caries
Recurrent or secondary caries is decay that occurs under a
restoration or around its margins. Recurrent caries often occur
CHAPTER 24 • THE USE OF RADIOGRAPHS IN THE DETECTION OF DENTAL CARIES 309
because of poor cavity preparation, defective margins of the
restoration, or incomplete removal of the caries prior to the
placement of the restoration. Recurrent caries appears on a
radiograph as a radiolucent area beneath a restoration or apical
to the interproximal margin of a restoration (Figure 24-15).
Rampant Caries
The term rampant means growing rapidly or spreading
unchecked. Rampant caries are severe, unchecked caries that
affect multiple teeth (Figure 24-16).
Arrested Caries
The term arrested means stopped or inactive. Arrested
caries are caries that are no longer active. Carious lesions
may become arrested if there is a significant shift in the oral
environment from factors that cause caries to those that slow
down the caries’ process. Incipient enamel caries (C-1) can
FIGURE 24-13 Drawing of cemental (root) caries
illustrates involvement of only the roots of teeth. Gingival
recession and bone loss precede the demineraliztion process to
expose the root surfaces.
FIGURE 24-14 Radiograph of cemental (root) caries. The
large radiolucency on the distal surface of the distal root of the first
mandibular molar is cemental caries. Note the bone loss exposing the
root surface.
FIGURE 24-16 Radiographs of rampant caries. Multiple teeth
affected by severe cemental caries.
1
FIGURE 24-15 Radiograph of recurrent caries. (1) Radiolucent caries under the metallic restoration.
remain dormant for long periods of time. Some carious
lesions may even be reversed by remineralization. It is
important that radiographic exams continue to monitor
arrested caries.
Conditions Resembling Caries
Three conditions that resemble caries are nonmetallic restorations, cervical burnout, and mach band effect.
Nonmetallic Restorations
Nonmetallic esthetic restorations may mimic decay radiographically (Figure 24-17). Nonmetallic restorations such as
composite, silicate, and acrylic resin, discussed in Chapter 23,
may mimic decay when they appear radiolucent. To aid in distinguishing a restoration from caries, look for the restoration to
have straight borders, or a prepared look, with an overall even
310 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
radiolucency. A radiopaque base material may also be present
under the radiolucent nonmetallic restoration. Caries tend to
have more diffuse borders and an uneven radiolucency that
takes on a triangular shape, with the apex pointing toward the
DEJ or pulp. A clinical examination may be required to make a
final determination.
Cervical Burnout
Cervical burnout is an optical illusion created when the eye
must distinguish between a very light (white) area and a very
dark (black) area on the radiograph. The area of the tooth most
likely to produce this optical illusion is the cervical root, or
neck of the tooth. In this region, the concavity of the root surfaces allows greater penetration by the x-rays (Figure 24-18).
This region will appear especially dark next to radiopaque
structures. When the radiopaque enamel on one side and the
radiopaque lamina dura on the other side sandwich the radiolucent cervical of the tooth in between, the effect is an
increased darkness called cervical burnout. Cervical burnout
often appears as an irregularly shaped radiolucent area with a
fuzzy outline seen on the mesial and/or the distal surfaces of
the tooth along the cervical line (Figure 24-19). To assist in
distinguishing cervical burnout from caries, remember to
focus caries detection only in the area of the contact point of
adjacent teeth and apical to the gingival margin (Figure 24-7).
Cervical burnout appears more apical, apparently under the
gingival margin.
Mach Band Effect
Another optical illusion is a radiolucency caused by overlapping images of the teeth. When two proximal surfaces overlap
(caused either by natural overlap of misaligned teeth or by
improper horizontal angulation of the x-ray beam), the result is
a dense radiopaque area surrounded by radiolucent lines. These
radiolucent lines represent an optical illusion called the mach
band effect, resulting from the high contrast between the normal enamel and the dense overlapped enamel (Figure 24-20).
The ability of these overlapped structures to produce this optical illusion illustrates how important it is to produce radiographs that do not have angulation errors.
1
2
FIGURE 24-17 Radiograph of nonmetalic restorations and
carious lesions in anterior teeth. (1) Radiolucent nonmetallic
restorations on the mesial surface of the lateral incisor and distal
surface of the central incisor. Note that under both restorations is a
base of radiopaque material. (2) The radiolucencies on the mesial
surfaces of both central incisors are carious lesions.
1
FIGURE 24-18 Drawing of cervical burnout. (1) Thin cervical
root surface between dense crown and alveolar bone crest allows
more x-rays to pass and reach the image receptor. This cervical area
of the teeth will most likely be imaged at an increased radiolucency.
FIGURE 24-19 Radiograph demonstrating cervical burnout.
Note the radiolucent optical illusion of cervical burnout on the
mesials and distals between the enamel and restorations and the
alveolar crest of bone.
CHAPTER 24 • THE USE OF RADIOGRAPHS IN THE DETECTION OF DENTAL CARIES 311
REVIEW—Chapter summary
The detection of caries is often the most common reason for taking dental radiographs. Caries appear radiolucent because the
demineralization of the tooth allows more x-rays to pass through
to reach the image receptor. Only precisely exposed and meticulously processed radiographs are useful in detecting caries.
Detecting proximal surface caries is the main purpose of
bitewing radiographs. Carefully positioned periapical radiographs, exposed using the paralleling technique, are also valuable in detecting proximal surface caries. Some practitioners
prefer a high-contrast image (produced with a low kVp) for
detecting caries. Radiographs detect more proximal surface caries
than a clinical exam alone. A clinical exam is better at detecting
early occlusal, buccal/lingual, and cemental caries. The depth of
the caries penetration is deeper clinically than it appears on the
radiograph.
An example of a caries depth grading system is presented.
These grades may also be referred to as incipient, moderate,
advanced, and severe caries.
The radiographic appearance of caries may be classified
according to their location on the tooth: proximal, occlusal, buccal/lingual, and cemental (root surface). Three conditions that
resemble caries are nonmetallic restorations, cervical burnout,
and mach band effect.
1
2 3
4
FIGURE 24-20 Caries and optical illusions that mimic decay.
(1) Severe occlusal caries. (2) Radiolucent lines creating a mach band
effect caused by overlapped enamel. (3) Incipient distal surface caries.
(4) Cervical burnout.
RECALL—Study questions
1. Caries appear radiopaque, because more radiation is
passing through the demineralization than the surrounding tissues.
a. The first part of the statement is true, but the second
part of the statement is false.
b. The first part of the statement is false, but the second
part of the statement is true.
c. Both parts of the statement are true.
d. Both parts of the statement are false.
2. Each of the following will produce an ideal radiographic
image for detecting caries EXCEPT one. Which one is the
EXCEPTION?
a. Bitewing radiographs
b. Periapical radiographs
c. Horizontal angulation that avoids overlapping
d. Excessive vertical angulation
3. Caries in the earliest stage is called
a. incipient.
b. moderate.
c. advanced.
d. severe.
4. Radiographs are best at detecting incipient caries of
which of these locations on the tooth?
a. Occlusal
b. Proximal
c. Buccal/lingual
d. Cemental
5. The key to successfully interpretating radiographs for
proximal surface caries is to examine the contact point
between adjacent teeth and just apical to the
a. DEJ.
b. CEJ.
c. estimated gingival margin.
d. alveolar bone crest.
6. Proximal surface carious lesions appear
a. triangular.
b. square.
c. round.
d. crescent-shaped.
7. Which of the following appears radiographically as a
radiolucent notch that is less than half-way through the
enamel?
a. Incipient proximal caries
b. Moderate proximal caries
c. Advanced proximal caries
d. Severe proximal caries
312 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
8. Which of the following appears radiographically as a radiolucent double triangle that is less than halfway through
the dentin toward the pulp?
a. Incipient proximal caries
b. Moderate proximal caries
c. Advanced proximal caries
d. Severe proximal caries
9. The key to successfully interpretating radiographs for
occlusal caries is to examine
a. the occlusal surface for changes in the pits and fissures.
b. under the occlusal surface for changes in the dentin.
c. the contact point between adjacent teeth for changes
in the enamel.
d. just apical to the contact point for changes in the DEJ.
10. Which of the following appears radiographically as a
round radiolucency in the middle of the tooth with welldefined borders?
a. Proximal caries
b. Occlusal caries
c. Cemental caries
d. Buccal/lingual caries
11. Which of the following appears radiographically as an
ill-defined crescent-shaped radiolucency below the
CEJ?
a. Proximal caries
b. Occlusal caries
c. Cemental caries
d. Buccal/lingual caries
12. Caries that occur under a restoration or around its margins are called
a. recurrent caries.
b. cemental caries.
c. root caries.
d. buccal caries.
13. Each of the following may mimic caries radiographically EXCEPT one. Which one is the EXCEPTION?
a. Composite restorations
b. Stainless stain crowns
c. Cervical burnout
d. Mach banding
14. An optical illusion created by an increased radiolucency
observed at the cervical area of the tooth is called mach
banding.
The mach banding effect increases when overlap error
occurs.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
REFLECT—Case study
You are interpreting a full mouth series of radiographs on a
patient who had dental hygiene services at your facility this
morning. The completed patient’s dental examination chart is
available, but the patient has been dismissed. As you examine the
radiographs, you notice the following:
1. Incipient proximal caries on the distal of the maxillary
right first molar.
a. Describe the radiographic appearance of this lesion.
b. Indicate why you classified this lesion as incipient.
2. Moderate proximal caries on the mesial of the maxillary
left first premolar.
a. Describe the radiographic appearance of this lesion.
b. Indicate why you classified this lesion as moderate.
3. Advanced proximal caries on the mesial of the mandibular left second premolar.
a. Describe the radiographic appearance of this lesion.
b. Indicate why you classified this lesion as advanced.
4. Severe proximal caries on the distal of the mandibular
right first molar.
a. Describe the radiographic appearance of this lesion.
b. Indicate why you classified this lesion as severe.
5. Advanced occlusal caries on the maxillary right second
molar.
a. Describe the radiographic appearance of this lesion.
b. Indicate why you classified this lesion as advanced.
6. Cemental caries on the mesial of the mandibular right
first premolar.
a. Describe the radiographic appearance of this lesion.
b. Indicate why you classified this lesion as cemental.
7. The patient’s chart indicates incipient occlusal caries
detected clinically on the maxillary left first and second
molars. However, these do not seem to be evident radiographically.
a. Explain why these caries are not observed on the
radiographs.
8. The patient’s chart indicates incipient buccal caries
detected clinically on the mandibular left first molar.
However, this lesion does not seem to be evident radiographically.
a. Explain why the buccal caries is not observed on the
radiographs.
9. The radiographs reveal two radiolucencies resembling
cemental (root) caries around the cervical of the mandibular right first and second premolars. However, the
patient’s chart does not indicate that cemental caries
were detected clinically.
a. Explain the possible cause of these radiolucencies.
10. The periapical radiograph of the maxillary left molar
region is overlapped between the maxillary first and
second molars.
a. Explain why detecting caries in this area will be
compromised.
b. What optical illusion will most likely present in this
area?
c. Describe the appearance of this optical illusion.
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson. Chapter 14, “Radiographic interpretation.”
REFERENCES
Berry, H. (1983). Cervical burnout and mach band: Two shadows of doubt in radiologic interpretation of carious lesions.
Journal of the American Dental Assocication, 106, 622.
Langlais, R. P., & Kasle, M. J. (1992). Exercises in oral radiographic interpretation (3rd ed.). Philadelphia: Saunders.
Langlais, R. P., Langland, O. E., & Nortje, C. J. (1995).
Diagnostic imaging of the jaws. Philadelphia:
Williams & Wilkins.
Langlais, R. P. (2003). Exercises in oral radiology and interpretation (4th ed.). Philadelphia: Saunders.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
CHAPTER 24 • THE USE OF RADIOGRAPHS IN THE DETECTION OF DENTAL CARIES 313
CHAPTER
OUTLINE
 Objectives 314
 Key Words 314
 Introduction 315
 Radiographic
Appearance of
Periodontal
Diseases 315
 Radiographic
Examination 315
 Radiographic
Techniques 318
 Radiographic
Interpretation of
Periodontal
Diseases 320
 Review, Recall,
Reflect, Relate 323
 References 324
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. List the uses of radiographs in the assessment of periodontal diseases.
3. Differentiate between horizontal and vertical bone loss.
4. Identify three local contributing factors for periodontal disease that radiographs can help
locate.
5. Explain how imaging anatomical configurations aids in the prognosis of periodontally
involved teeth.
6. List the limitations of radiographs in the assessment of periodontal diseases.
7. Recognize the role vertical and horizontal angulations play in imaging periodontal diseases.
8. Use the appropriate radiographic techniques to best detect and evaluate periodontal diseases.
9. Describe the radiographic appearance of the normal periodontium.
10. List four American Academy of Periodontology disease classification case types, and describe
their radiographic appearance.
KEY WORDS
Alveolar (crestal) bone
Calculus
Cementoenamel junction (CEJ)
Furcation involvement
Generalized bone loss
Gingivitis
Horizontal bone loss
Interdental septa
Lamina dura
Local contributing factor
Localized bone loss
Occlusal trauma
Pathogen
Periodontal diseases
Periodontal ligament space
Periodontitis
Periodontium
Triangulation
Vertical (angular) bone loss
Vertical bitewing series
The Use of Radiographs
in the Evaluation of
Periodontal Diseases
CHAPTER
25
CHAPTER 25 • THE USE OF RADIOGRAPHS IN THE EVALUATION OF PERIODONTAL DISEASES 315
Introduction
Dental radiographs play a key role in the diagnosis, prognosis,
management and evaluation of periodontal diseases. Properly
exposed and meticulously processed radiographs are invaluable
aids in the diagnosis of periodontal diseases. To get the most diagnostic information from radiographs taken to image periodontal
status, radiographers should have an extensive knowledge of the
radiographic techniques that will produce quality images. The
purpose of this chapter is to introduce the dental radiographer to
the radiographic appearance of periodontal diseases, to outline the
radiographic examinations and techniques best suited to produce
quality radiographs for the purpose of evaluating periodontal diseases, and to describe local contributing factors for the disease
that radiographs help to identify.
Radiographic Appearance of Periodontal
Diseases
Periodontal diseases are diseases that affect both soft tissues
(gingiva) and bone around the teeth. The severity of periodontal
disease may range from a simple inflammation of the gingiva to
the destruction of supporting bone and the periodontal ligament. The most common periodontal diseases are gingivitis and
periodontitis. Gingivitis is inflammation of the gingiva and
limited to the soft tissue (gingiva). Periodontitis is also the
result of infection, but includes loss of alveolar bone.
The proper diagnosis and evaluation of periodontal diseases
must be made with a combination of radiographic and clinical
examinations.
Radiographic Examination
Uses (Box 25-1)
Radiographs, along with a thorough clinical examination, allow
the dentist and dental hygienist to evaluate and document periodontal diseases. The uses of radiographs in the assessment of
periodontal diseases include the following:
1. Imaging supporting bone. Radiographs allow the practitioner to evaluate crestal bone irregularities and interdental
septa changes (alveolar bone changes between the teeth).
Radiographs document the amount of bone remaining
rather than the amount lost. The amount of bone loss is estimated as the difference between the physiologic bone level
and the height of the remaining bone (Figure 25-1).
Radiographs also allow the practitioner to determine
the pattern of bone loss; horizontal or vertical.
Horizontal bone loss describes height loss around adjacent teeth in a region. In horizontal bone loss, both buccal
and lingual plates have been resorbed as well as the intervening interdental bone. Horizontal bone loss occurs in a
plane parallel to the cementoenamel junctions (CEJ) of
adjacent teeth (Figure 25-2). Vertical bone loss, sometimes called angular bone loss, occurs in a vertical direction where the resorption of one tooth root sharing the
interdental septum (bone between the teeth) is greater
than the other tooth (Figures 25-3, 25-4, and 25-5).
Radiographs can help the practitioner determine the distribution of bone loss: localized or generalized. Localized
bone loss occurs in local areas and involves one or only a few
teeth. Generalized bone loss occurs throughout the entire
dental arches.
A
B
FIGURE 25-1 Drawing illustrating horizontal bone loss.
(A) Normal (physiologic) level of bone (alveolar bone parallel to the
cementoenamel junction) and (B) Bone level of patient with
periodontal disease. Horizontal bone loss is the difference between
(A) and (B) (shaded area).
FIGURE 25-2 Horizontal bone loss. Arrows show bone level of
patient with periodontal disease. Note that the level of bone loss is
parallel to an imaginary line drawn between the cementoenamel
junctions of the adjacent teeth.
BOX 25-1 Periodontal Bone Changes Recorded
by Radiographs
• Crestal irregularities
• Interdental alveolar bone changes
• Pattern of bone loss (horizontal/vertical)
• Distribution of bone loss (localized/generalized)
• Severity of bone loss (slight, moderate, advanced)
• Furcation involvement
316 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
Vertical bone loss
FIGURE 25-3 Drawing illustrating vertical bone loss. Vertical
bone loss appears angular where the resorption is greater on the side
of one tooth than on the side of the adjacent tooth.
FIGURE 25-4 Vertical bone loss. Arrows show bone level of
patient with periodontal disease.
Radiographs can reveal the severity of bone loss—slight,
moderate, or advanced—and furcation involvement (bone
loss between the roots) of multirooted teeth (Figure 25-6).
2. Imaging local contributing factors. Radiographs can detect
conditions such as amalgam overhangs (see Chapter 23),
poorly contoured crown margins, and calculus deposits that
act as traps that can lead to the buildup of bacterial
pathogens that cause periodontal diseases (Figures 25-7 and
25-8). Calculus, essentially hardened plaque, appears
slightly radiopaque (about the radiopacity of dentin) and
must be significantly calcified to be recorded on radiographs.
Depending on the density and the amount of the deposit, calculus may appear as pointed or irregular projections on the
proximal root surfaces, or as a ringlike radiopacity around
the cervical neck of a tooth.
Radiographs often reveal the effects of traumatic
occlusion, another contributing factor for periodontal disease. Occlusal trauma does not cause periodontal disease,
but has been shown to hinder the body’s response to the
disease. The effects of excessive occlusal forces show up
2 1
FIGURE 25-5 Comparison of horizontal and verical bone
loss. Use the CEJ of adjacent teeth as a guideline. (1) Horizontal
bone loss. (2) Vertical bone loss.
FIGURE 25-6 Furcation involvement. Note the radiolucency in
between the roots of these multirooted teeth.
FIGURE 25-7 Local contributing factors. Calculus (arrow) and
amalgam overhang (circled) are likely to collect bacterial pathogens that
can contribute to the progression of periodontal diseases.
CHAPTER 25 • THE USE OF RADIOGRAPHS IN THE EVALUATION OF PERIODONTAL DISEASES 317
1
2
FIGURE 25-8 Calculus. (1) large deposits around the necks of
the teeth. (2) Height of alveolar bone remaining as a result of
periodontal disease.
be more likely to have a better prognosis because of the
amount of bone support.
4. Evaluating the prognosis and treatment intervention needs.
By providing information on the tooth root-to-crown ratio, and
adjacent tooth proximity, radiographs help the practitioner plan
treatment and predict outcomes.
5. Serving as a baseline and as a means for evaluating the
results of treatment. Radiographs provide documentation
on the progression of disease and provide a permanent record
of the condition of the bone throughout the course of the disease and treatment.
Limitations
1. Radiographs are a two-dimensional image of threedimensional objects. Radiographs lack the third dimension
of depth, which results in bone and tooth structures being
superimposed over each other. This will often hide bone loss
on the buccal and lingual surfaces and furcation area, especially in the posterior region of the oral cavity.
2. Changes in soft tissue not imaged. Because soft tissue is
not recorded on radiographs, gingivitis cannot be detected
radiographically. Radiographs do not add any information
regarding the location and/or depth of periodontal pockets.
3. Cannot distinguish treated versus untreated disease.
Radiographs do not indicate the presence or absence of
active disease.
4. Actual destruction more advanced clinically. Radiographs
cannot detect early signs of periodontal diseases. A significant
loss of bone density must occur before radiographic changes
are detected.
FIGURE 25-9 Triangulation. Widening of the periodontal
ligament space indicative of occlusal trauma.
FIGURE 25-10 Root length and root-to-crown ratio.
Although the bone loss observed on this radiograph is significant, the
longer than normal, dilacerated root improves the
prognosis for the canine.
on radiographs as a widening of the periodontal ligament
space (Figure 25-9), called triangulation. Triangulation is
bordered by the lamina dura and the root surface of the
tooth, with its base toward the tooth crown.
3. Imaging anatomical configurations. Radiographs can
reveal information about root morphology and lengths and
the presence of dilacerations (see Chapter 23); root shape and
width, such as multirooted teeth with ample supporting bone
in between the roots; or narrow, close, or fused roots, all of
which can help determine the treatment and predict treatment
outcomes. For example, a tooth with a shortened root as a
result of external resorption (see Chapter 23) will have a poor
prognosis, whereas a tooth with a normal or long root may
have a better prognosis (Figure 25-10). Additionally, teeth
that have ample bone surrounding widely spaced roots will
318 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
B
FIGURE 25-12 Correct and incorrect vertical angulation.
(A) Correct vertical angulation accurately records crestal bone
indicating no bone loss between the mandibular first and second
molars. (B) Incorrect vertical angulation produces a radiolucent,
cupping-out appearance of the lamina dura falsely indicating bone
loss between these same teeth. (Thomson, E. M., & Tolle, S. L. (1994).
A practical guide for using radiographs in the assessment of periodontal
diseases. Part 2: Interpretation and future advances. Journal of Practical
Hygiene, 3(2), 12. Permission from Montage Media.)
Radiographic Techniques
Bitewings, especially the vertical bitewing series of anterior
and posterior radiographs described in Chapter 16, are most
useful for examining the periodontium (Figure 25-11). The
A
B
C
FIGURE 25-11 Comparsion of bitewing and periapcial
radiographs imaging the periodontium. (A) Vertical bitewing.
(B) Horizontal bitewing. (C) Periapical.
precise parallelism established between the tooth and the plane
of the image receptor when taking bitewing radiographs makes
it possible to image the alveolar crestal bone accurately. To
achieve this same degree of accuracy when using periapical
radiographs to image the periodontium, the paralleling technique must be used. The image receptor must be placed parallel to the long axis of the teeth to ensure that the images of the
bone and teeth on the radiograph are not distorted.
To be a useful diagnostic aid, the radiographs must be
precisely exposed and meticulously processed. Incorrect
angulation can render a radiograph worthless for evaluating
periodontal disease. Excessive vertical angulation may not
reveal bone loss, whereas inadequate vertical angulation
may result in a radiographic image that falsely indicates
bone loss when there is none (Figures 25-12 and 25-13).
A
CHAPTER 25 • THE USE OF RADIOGRAPHS IN THE EVALUATION OF PERIODONTAL DISEASES 319
A B
FIGURE 25-13 Correct and incorrect vertical angulation. (A) Correct vertical angulation accurately records crestal bone
indicating bone loss mesial and distal to the maxillary first molar,. (B) Incorrect vertical angulation produces a false appearance
to the level of bone in these same areas. (Thomson, E. M., & Tolle, S. L. (1994). A practical guide for using radiographs in the assessment of
periodontal diseases. Part 2: Interpretation and future advances. Journal of Practical Hygiene, 3(2), 12. Permission from Montage Media.)
Accurate horizontal angulation is also important in evaluating periodontal disease. Incorrect horizontal angulation
results in overlapping of the contact areas between the teeth,
making it impossible to determine the condition of interdental bone (bone in between the teeth). Second, varying the
horizontal angulation slightly may actually increase the
chances of imaging interdental defects and furcation
A B
FIGURE 25-14 Example of varying horizontal angulation. (A) Correct horizontal
angulation, but image does not reveal the vertical (angular) defect on the mesial of the maxillary
first molar. (B). Slightly varied horizontal angulation of the same region now reveals the vertical
bony defect. (Thomson, E. M., & Tolle, S. L. (1994). A practical guide for using radiographs in the
assessment of periodontal diseases. Part 2: Interpretation and future advances. Journal of Practical Hygiene,
3(2), 13. Permission from Montage Media.)
involvement. For example, a bitewing series of seven radiographs (discussed in Chapter 16) and a full mouth series of
multiple periapical and bitewing radiographs (discussed in
Chapter 14) will contain images that were produced with
different horizontal angles. The varying angulations used
allow for multiple views of the condition of the periodontium (Figure 25-14).
320 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
PROCEDURE 25-1
Radiographic interpretation for periodontal disease
1. See Procedure Box 21-2, Suggested Sequence for Viewing a Full Mouth Series of Radiographs.
2. View all surfaces of each tooth.
3. Note the alveolar bone height. Use the CEJ as a reference point. Measure with a probe as needed (see
Figure 21-5).
4. Examine the periodontal ligament space, following it around the entire tooth. Note widening, triangulation.
5. Examine the furcation area of multirooted teeth.
6. Identify local contributing factors such as restoration overhangs and calculus.
7. Confirm findings and/or clarify uncertain interpretations with a clinical examination of the patient.
8. Consult the patient’s chart for confirmation or clarification of findings as needed.
9. Present a preliminary interpretation for the dentist’s review.
10. Following confirmation by the dentist, document all findings on the patient’s permanent record.
TABLE 25-1 American Academy of Periodontal Disease Classification
CLASSIFICATION RADIOGRAPHIC APPEARANCEa
Case Type I: Gingivitis Alveolar crest: Unbroken, radiopaque at a level 1.5–2.0 mm below and parallel to the CEJ
Anterior: Pointed Posterior: Flat, smooth
Case Type II: Slight Chronic Periodontitis Alveolar crest: Loss of density with slight radiolucencies evident; triangulation observed
Anterior: Blunted Posterior: Fuzzy, cupping-out appearance
Case Type III: Moderate Chronic or
Aggressive Periodontitis
Alveolar crest: Level greater than 2.0 mm below the CEJ, indicating 30–50 percent bone loss
Anterior and posterior: Horizontal and/or vertical patterns of bone loss observed
Posterior: Furcation radiolucencies evident
Case Type VI: Advanced Chronic or
Aggressive Periodontitis
Alveolar crest: Easily identified with level of bone loss greater than 50 percent
Anterior and Posterior: Evidence of tooth position changes, drifting
Source: Perry, D. A., Beemsterboer, P., & Taggart, E. J. (2007). Periodontology for the dental hygienist (3rd ed.). St. Louis, MO: Elsevier. a
Although the exposure factors (mA, kVp, and time) used
will depend on the patient and the area to be exposed, some
practitioners prefer to use a higher kVp to best image subtle
bone changes. A higher setting, such as 90 kVp, will result in
an image that has a low constrast: black and white with many
shades of gray in between. Because bone changes that accompany periodontal diseases appear as a radiolucency within the
radiopaque bone, a low-contrast image is preferred by some
practitioners for imaging these early signs of bone destruction.
Radiographic Interpretation of Periodontal
Diseases
The dental radiographer should be familiar with the radiographic appearance of the normal periodontium to be able to
identify deviations from normal that may indicate possible
periodontal diseases (Procedure Box 25-1). The American
Academy of Periodontology classifies periodontal disease
based on etiologic factors of the disease and tissue response to
treatment. Four classifications of periodontal disease are
described, based on changes in the periodontium as seen on
radiographs (Table 25-1).
Case Type I: Gingivitis
Radiographs do not image soft tissue, and therefore the radiographic appearance of the periodontium in all types and
severities of gingivitis appears the same as normal bone. The
lamina dura (dense cortical plate of the bony tooth socket)
appears as an unbroken, dense radiopaque line around the
roots of the teeth. The alveolar crest is located 1.5 to 2.0 mm
apical to the cementoenamel junctions (CEJ) of the teeth
(Figure 25-15). In the anterior region of the oral cavity, the
CHAPTER 25 • THE USE OF RADIOGRAPHS IN THE EVALUATION OF PERIODONTAL DISEASES 321
FIGURE 25-15 Drawing illustrating Case Type I: Gingivitis.
Alveolar crest located 1.5 to 2.0 mm apical to the cementoenamel
junctions (CEJ) of the teeth.
FIGURE 25-16 Case Type I: Gingivitis-anterior region. Note
the normal pointed radiopaque appearance of the lamina dura and
thin radiolucent line of the periodontal ligament space.
alveolar crest appears pointed and sharp (Figure 25-16). In the
posterior region of the oral cavity, the alveolar crest is more
flat, smooth, and parallel to an imaginary line drawn between
adjacent CEJ (Figure 25-17). The peridontal ligament space
appears as a thin radiolucent line between the lamina dura and
the root of the tooth.
Case Type II: Slight Chronic Periodontitis
Early bone loss up to 30 percent is evident (Figure 25-18).
Loss of crestal bone density that often appears as a fuzzy
cupping-out of the alveolar crest is the first radiographic
indication of periodontal disease (Figure 25-19). The alveolar crest appears blunted in the anterior region of the oral
FIGURE 25-17 Case Type I: Gingivitis-posterior region. Note
the normal radiopaque flat appearance of the lamina dura and thin
radiolucent line of the periodontal ligament space.
FIGURE 25-18 Drawing illustrating Case Type II: Slight Chronic
Periodontitis.
FIGURE 25-19 Case Type II: Slight Chronic Periodontitisposterior region. Note the slight radiolucent cupping-out of the
lamina dura, especially visible between the mandibular first and
second molars. Radiopaque calculus is visible on the proximal
surfaces of the teeth.
322 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
FIGURE 25-23 Case Type III: Moderate Chronic or
Aggressive Periodontitis-posterior region. Note the 30–50
percent bone level resorption and radiolucency in the furca of the
mandibular molars indicating furcation involvement.
FIGURE 25-24 Drawing illustrating Case Type IV: Advanced
Chronic or Aggressive Periodontitis.
FIGURE 25-20 Case Type II: Slight Chronic Periodontitisanterior region. Note the blunting of the lamina dura and slight
radiolucent widening of the periodontal ligament space. Slightly
radiopaque calculus is visible.
cavity (Figure 25-20). In the posterior region of the oral cavity triangulation, a widening of the periodontal ligament
space becomes evident at the mesial or distal surfaces of the
teeth.
Case Type III: Moderate Chronic or Aggressive
Periodontitis
Moderate bone loss (30 to 50 percent) may appear in both the
horizontal and vertical planes (Figures 25-21 and 25-22). As
the bone levels resorb, radiolucencies may appear in the furcations of multirooted teeth. (Figure 25-23).
Case Type IV: Advanced Chronic or Aggressive
Periodontitis
The advanced stage of periodontal disease (greater than 50 percent bone loss) is characterized radiographically by severe horizontal and/or vertical bone loss, evidence of furcation
FIGURE 25-21 Drawing illustrating Case Type III: Moderate
Chronic or Aggressive Periodontitis.
FIGURE 25-22 Case Type III: Moderate Chronic or Aggressive
Periodontitis-anterior region. Note the 30–50 percent bone level
resorption.
CHAPTER 25 • THE USE OF RADIOGRAPHS IN THE EVALUATION OF PERIODONTAL DISEASES 323
involvement, widened periodontal spaces, and indications of
changes in tooth position (Figures 25-24 through 25-26).
REVIEW—Chapter summary
Periodontal diseases are diseases that affect both soft tissues (gingivitis) and bone around the teeth (periodontitis).
Properly exposed and meticulously processed radiographs
play a key role in the diagnosis and evaluation of periodontal diseases.
The uses of radiographs in the evaluation and treatment
of periodontal diseases include imaging the supporting bone,
locating local contributing factors, imaging anatomical configurations, evaluating prognosis and treatment intervention
needs, and serving as a baseline for identifying and documenting the progression of the disease and the results of
treatment. Radiographs are limited in their ability to image
periodontal diseases because they are two-dimensional pictures of three-dimensional teeth and supporting bone;
changes in soft tissue are not imaged; treated disease cannot
be distinguished from untreated disease, and the actual
destruction of bone is more clinically advanced than what is
revealed on radiographs.
The ideal radiographs for imaging periodontal diseases are
bitewings, particularly vertical bitewings, or periapical radiographs exposed by the paralleling technique. Some practitioners prefer low-contrast images produced with a high kVp for
detecting subtle changes in the bone.
Radiographs are important aids in identifying changes in
the periodontium and can assist in classifying various stages
of periodontal disease. The dental hygienist and the dental
assistant should possess a working knowledge of normal radiographic appearance of the periodontium to be able to recognize deviations from normal that indicate periodontal disease.
FIGURE 25-25 Case Type IV: Advanced Chronic or
Aggressive Periodontitis-anterior region. Note the 50 percent or
greater bone level resorption.
FIGURE 25-26 Case Type IV: Advanced Chronic or
Aggressive Periodontitis-posterior region. Note the 50 percent or
greater bone level resorption and obvious furcation involvement.
RECALL—Study questions
1. Each of the following may be determined from a dental radiograph EXCEPT one. Which one is the
EXCEPTION?
a. Bone loss
b. Pocket depth
c. Furcation involvement
d. Local contributing factors
2. List four uses of radiographs in the assessment of periodontal diseases.
a. ______________
b. ______________
c. ______________
d. ______________
3. Which of the following terms describes bone loss that
occurs in a plane parallel to the cementoenamel junction of adjacent teeth?
a. Irregular
b. Vertical
c. Horizontal
d. Periapical
4. Significant bone loss that results in a radiolucency
observed in the area between the roots of multirooted
teeth is called
a. localized bone loss.
b. interdental septa.
c. local contributing factor.
d. furcation involvement.
5. Radiographs may help to locate each of the following
local contributing factors EXCEPT one. Which one is
the EXCEPTION?
a. Calculus
b. Poorly contoured crown margin
c. Deep pocket
d. Amalgam overhang
324 MOUNTING AND VIEWING DENTAL RADIOGRAPHS
6. Excessive occlusal force may result in a widening of the
periodontal ligament space.
Widening of the periodontal ligament space is called
furcation involvement.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
7. Dental radiographs are important because they document the location and depths of periodontal pockets.
Dental radiographs may serve as a baseline and as a means
for evaluating the outcomes of periodontal treatments.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
8. List four limitations of dental radiographs in the assessment of periodontal diseases.
a. ______________
b. ______________
c. ______________
d. ______________
9. Which of the following would be best for imaging a
slight, but generalized periodontal status?
a. Select periapical radiographs using the bisecting technique.
b. Select periapical radiographs using the paralleling
technique.
c. Posterior horizontal bitewing radiographs.
d. Posterior and anterior vertical bitewing radiographs.
10. Correct horizontal angulation is needed to accurately
image interdental bone levels.
Altering the horizontal angulation can reveal additional
information regarding interdental bone levels.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
11. Alveolar crests pointed in the anterior region and a
radiopaque flat, smooth lamina dura 1.5 to 2.0 mm below
the CEJ in the posterior region describes
a. Case Type I: Gingivitis
b. Case Type II: Slight Chronic Periodontitis
c. Case Type III: Moderate Chronic or Aggressive
Periodontitis
d. Case Type IV: Advanced Chronic or Aggressive
Periodontitis
12. Radiolucent changes observed on a radiograph such as
a fuzzy, cupping-out of the crestal bone and a blunted
appearance of the lamina dura in the anterior region
describes
a. Case Type I: Gingivitis
b. Case Type II: Slight Chronic Periodontitis
c. Case Type III: Moderate Chronic or Aggressive
Periodontitis
d. Case Type IV: Advanced Chronic or Aggressive
Periodontitis
REFLECT—Case study
Describe what radiographic changes in the periodontium you
would expect to observe on a seven-image series of vertical
bitewing radiographs on the following patients classified according to the American Academy of Periodontology Disease Classification:
1. Case Type I: Gingivitis
2. Case Type II: Slight Chronic Periodontitis
3. Case Type III: Moderate Chronic or Aggressive
Periodontitis
4. Case Type IV: Advanced Chronic or Aggressive
Periodontitis
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography techniques: A laboratory manual (3rd ed.). Upper Saddle River, NJ:
Pearson Education. Chapter 14, “Radiographic interpretation.”
REFERENCES
Langlais, R. P. (2003). Exercises in oral radiology and interpretation (4th ed.). Philadelphia: Saunders.
Perry, D. A., Beemsterboer, P., & Taggart, E. J. (2007).
Periodontology for the dental hygienist (3rd ed.). St. Louis,
MO: Elsevier.
Thomson, E. M., & Tolle, S. L. (1994). A practical guide for
using radiographs in the assessment of periodontal disease,
Part 2: Interpretation and Future Advances. Practical
Hygiene 3, 2.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. State the basis for prescribing dental radiographs for children.
3. List the conditions that would indicate radiographs be taken on children.
4. Identify suggested exposure intervals for the child patient.
5. List the factors that determine the number and size of image receptors to be exposed on
children.
6. List image receptor size and type suggested for use with primary dentition.
7. List image receptor size and type suggested for use with transitional (mixed primary and
permanent) dentition.
8. Identify two types of extraoral radiographs that may be acceptable substitutes for children
who cannot tolerate intraoral image receptor placement.
9. Identify adaptations or modifications in standard paralleling and bisecting techniques that
aid in radiographic procedures for children.
10. Explain the role occlusal radiographs play in imaging children.
11. Appropriately adjust standard adult exposure settings to apply to children.
12. Explain the roles that the patient management techniques show-tell-do and modeling play
in assisting the radiographer with child patient management.
13. Interpret radiographs taken on children with primary and transitional (mixed primary and
permanent) dentition.
KEY WORDS
ALARA (as low as reasonably achievable)
Anodontia
Exfoliation
Lateral jaw projection (mandibular oblique
lateral projection)
Modeling
Panoramic radiograph
Pediatric dentistry
Permanent teeth
Primary teeth
Show-tell-do
Supernumerary teeth
Transitional mixed dentition
Radiographic Techniques
for Children
CHAPTER
26
PART VIII • PATIENT MANAGEMENT
AND SUPPLEMENTAL TECHNIQUES
CHAPTER
OUTLINE
 Objectives 325
 Key Words 325
 Introduction 326
 Assessment of
Radiographic
Need 326
 Suggested Exposure
Intervals 326
 Image Receptor
Sizes and Numbers
and Types of
Projections 326
 Suggested
Radiographic
Techniques 328
 ALARA Radiation
Protection 329
 Patient
Management 329
 Interpretation 334
 Review, Recall,
Reflect, Relate 337
 References 339
326 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
Introduction
Children have the same basic needs for oral health care as do
adults. In fact, the best time to prevent dental problems is in
childhood. Children are at a higher risk for caries that progress
more rapidly than in adults. Radiographs play an important role
in both detecting disease and assessing growth and development
for the child patient.
Radiographic techniques and the types of projections used
to image the oral cavity of the child patient do not differ significantly
from those used for adult patients. However, the child patient
presents with unique characteristics such as a smaller oral cavity
and behavioral considerations that often require adaptations to
standard procedures. The purpose of this chapter is to discuss
ways the radiographer can adapt these standard techniques to
best image the child’s smaller and sometimes more sensitive
oral cavity. These adaptations, along with behavior modification
strategies can assist the radiographer in gaining the confidence
of the child patient to produce the highest quality diagnostic
images using the least amount of radiation exposure.
Assessment of Radiographic Need
The indication to expose dental radiographs on a child patient
is based on the individual needs of the patient. The evidencebased selection criteria guidelines, discussed in Chapter 6, have
categories for assessing children and adolescents as well as
adults (see Table 6-1). Indications for exposing radiographs for
the child patient include the detection of caries and periodontal
diseases; the assessment of growth and development and the
need for orthodontic intervention; the detection of congenital
dental abnormalities, such as anodontia (absence of teeth) and
supernumerary (extra) teeth; the evaluation of third molars;
the diagnosis of pathologic conditions such as an abscess or
other infection; and the assessment of the effect of trauma, such
as a fall or accident, not only for primary teeth, but for the
developing, unerupted permanent teeth as well.
Suggested Exposure Intervals
The American Academy of Pediatric Dentistry (pediatric
dentistry—pedia is Greek for child—is the branch of dentistry
that specializes in providing comprehensive preventive and therapeutic oral health care for children), and other oral health and
medical organizations, recommend that a child’s first professional
oral examination be made within 12 months following the eruption
of the first primary tooth, usually between six and twelve months
of age. Early prevention is key to preventing tooth loss and
developing good oral self-care habits. At this early age the teeth
can usually be visually inspected clinically without the need for
radiographs. Unless an accident, toothache, or other unusual
circumstance causes a need for radiographs, the selection criteria
guidelines discussed in Chapter 6 (see Table 6-1) suggest that the
first radiographic survey may not be necessary until all the primary teeth have erupted, preventing a visual inspection of the
proximal (contact) surfaces via a clinical inspection. Patients
without evidence of disease and with open interproximal contacts
may not require a radiographic exam. Once the teeth have erupted
in such a manner that the proximal surfaces can no longer be
viewed clinically, and caries are suspected, or the patient presents
with high risk factors for caries, such as poor oral self-care or
inadequate fluoride protection, radiographs may be indicated.
Image Receptor Sizes and Numbers
and Types of Projections
Once it has been determined that radiographs are needed, the
child’s age, size of the oral cavity, and cooperation level must
be considered when determining the size and number of radiographs to expose (Box 26-1). Although a size #0 or #1 intraoral
image receptor is usually used for radiographs of a child with
primary teeth, the preferred size for transitional mixed
dentition, where the child presents with a mix of both primary
and permanent teeth, is a standard size #2 image receptor. The
radiographer should use the largest size image receptor that the
child can tolerate. The amount of radiation required does not
change with different sizes of intraoral image receptors. Using
a size #2 image receptor whenever possible instead of a size #0
or size #1 will provide more information due to the coverage of
a larger area. This is particularly important when imaging
permanent teeth that are developing. The choice of image receptor
size should be individualized based on anatomical limitations
and tissue sensitivity. To aid with accurate and comfortable positioning, a smaller-size film packet should be selected rather than
bending the larger-size film, and a smaller-size digital sensor or
phosphor plate would be more likely retained in position for the
duration of the exposure.
The number of image receptors required depends on the
needs of the individual (see Table 15-1). When exposing bitewing
radiographs on a child patient prior to the eruption of the permanent second molar, two horizontal posterior bitewings, one on
each side, is recommended. Following eruption of the permanent
second molar, four horizontal (or vertical if periodontal disease is
suspected) posterior bitewings must be taken to image all proximal
contacts of the posterior teeth without overlap.
If conditions exist that require additional exposures, the following radiographic full mouth surveys are offered as suggestions.
BOX 26-1 Considerations for Choosing
the Number and Size of Image Receptor
to Expose on the Child Patient
• Oral health needs
• Willingness to cooperate
• Attention span and emotional state
• Ability to understand and follow directions
• Ability to hold still throughout the exposure
• Size of the opening to the oral cavity
• Size and shape of the teeth and the dental arches
• Sensitivity of the oral mucosa
• Operator’s ability to gain patient’s trust
• Operator’s ability to position the image receptor
• Operator’s knowledge of and skill ability to adapt standard
techniques
CHAPTER 26 • RADIOGRAPHIC TECHNIQUES FOR CHILDREN 327
FIGURE 26-1 Radiographic survey of primary dentition. One
anterior occlusal radiograph in each arch and one posterior bitewing
radiograph on each side. (Courtesy DP Gutz, DDS, University Nebraska
Medical Center, College of Dentistry, Lincoln, NE.)
FIGURE 26-2 Radiographic survey of transitional dentition. Six anterior periapical radiographs (three on the
maxilla and three on the mandible), one posterior periapical radiograph in each quadrant, and one posterior bitewing
radiograph on each side.
Primary Dentition
Small oral cavity size, tongue resistance, and gagging can be a
problem in small children aged three to six years old. Ideally, it
is advisable to expose four radiographs, one anterior occlusal
(see Chapter 17) of each arch (maxilla and mandible) and one
posterior bitewing on each side (Figure 26-1).
Transitional (Mixed Primary and Permanent) Dentition
At six years, the first permanent teeth have begun to erupt. Ideally,
the survey should include a minimum of twelve radiographs: ten
periapical and two bitewing exposures. Periapical radiographs are
exposed in each of the four molar and canine regions and in the
two incisor regions (Figure 26-2).
Between 12 and 14 years of age, all the permanent teeth
except the third molars have usually erupted. It is during this
adolescent period that growth is rapid and metabolic changes
occur that heighten the possibility of dental caries and increase
the need for preventive oral hygiene care. The full mouth survey
recommended for the adolescent is the same as that required for
the adult patient, usually fourteen periapical and four bitewing
radiographs. (See Chapters 14, 15, and 16.)
Extraoral Radiographs
The evidence-based selection criteria guidelines discussed in
Chapter 6 (see Table 6-1) indicate the value of an extraoral
technique called a panoramic radiograph (see Chapter 30) for
assessing growth and development for the child in mixed dentition
and for evaluating third molars in adolescents. Panoramic
radiographs are often prescribed to supplement intraoral exposures.
In addition, a panoramic radiograph may be an acceptable substitute when intraoral radiographs cannot be tolerated by the patient.
Panoramic radiographs do not image structures with the clarity
of intraoral radiographs and, therefore, do not reveal details such
as early carious lesions. However, these large radiographs are
ideal for imaging overall jaw development and the eruption pattern
of the teeth (Figure 26-3). The panoramic procedure is usually
well tolerated by the child patient. However, the child must be
able to hold still for the duration of the exposure (most panoramic
machines have a 15- to 20-second exposure cycle), and the child
must be able to understand and cooperate with the positioning
requirements necessary for a diagnostic image (see Chapter 30).
Although largely replaced by the availability of panoramic
machines in general practice, the lateral jaw projection (also
called a mandibular oblique lateral projection; see Chapter 29)
has been especially valuable to use with children (Figure 26-4).
The lateral jaw radiograph is used to examine the posterior region
328 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
FIGURE 26-3 Panoramic radiograph of a child with
transitional dentition. Note the overall jaw development and
eruption pattern of the teeth.
of the mandible with patients who are unable to tolerate
intraoral image receptor placement. The lateral jaw technique
is described in Chapter 28.
Suggested Radiographic Techniques
Methods for exposing radiographs on children are essentially the
same as those for adults. Although either the paralleling or bisecting technique can be used, the characteristics children present
with usually require a slight variation in the vertical angulation. A
smaller oral cavity and lowered palatal vault; the tendency toward
an exaggerated gag reflex and lack of tongue and muscle control;
and sensitive oral mucosa due to growth and the exfoliation
(shedding) of primary teeth and the eruption of permanent teeth
require that the radiographer be creative in improvising on the
basic techniques in a manner that will produce diagnostic-quality
images in the presence of these challenges.
The paralleling method is preferred for use on all patients
because of its ability to produce accurate images with little distortion. The greatest challenge of using the paralleling technique with children is placing the image receptor parallel to the
long axes of the teeth of interest. Switching to a smaller-sized
image receptor may help with this placement. Often, it is the
size and weight of the image receptor holder that the child has
FIGURE 26-4 Lateral jaw extraoral radiograph being
exposed on a child. The child holds the cassette that contains the
extraoral film against the side to be imaged. The PID directs the x-ray
beam under the chin up toward the cassette/film.
FIGURE 26-5 Modifying an image receptor holder biteblock
for use with the child patient. (Thomson, E. M. (1993). Dental
radiographs for the child patient. Dental Hygiene News, 6(4), 24, with
permission from Procter & Gamble Company.)
FIGURE 26-6 Adaptation of film holders for use with the
child patient. Using a bitewing bitetab as a periapical film holder.
(Thomson, E. M. (1993). Dental radiographs for the child patient. Dental
Hygiene News, 6(4), 24, with permission from Procter & Gamble Company.)
difficultly tolerating. Switching to a smaller, lighter image receptor holder, modifying an adult image receptor holder, or designing a custom holder may help the child patient tolerate placement
(Figures 26-5 and 26-6).
Once the image receptor is positioned, the vertical angulation
may still need to be increased slightly (no more than 10 degrees)
over the setting used for adult patients. Due to a shallow palatal
vault, the image receptor will most likely lay flatter in position.
Slightly increasing the vertical angulation over perpendicular
will help to image the root apices and the unerupted developing
permanent teeth (Figure 26-7).
The bisecting technique produces images with more distortion
and magnification than the paralleling technique, but its greatest
advantage is the ability to produce reasonably acceptable images
when parallel image receptor positioning is not possible. The
bisecting technique with its image receptor placement (see
Chapter 15) is ideal for use with the child patient.
PRACTICE POINT
Children can easily understand the directive to bite on the
image receptor as if it were a graham cracker. Occluding on
the flat positioning of a size #2 image receptor placed for an
occlusal projection is readily accepted by the child patient. It
will be up to the radiographer to have the knowledge and
skills to align the x-ray beam to produce an acceptable quality
radiograph.
CHAPTER 26 • RADIOGRAPHIC TECHNIQUES FOR CHILDREN 329
Position Indicating
Device
Position Indicating
Device
Image
receptor
Image
receptor
FIGURE 26-7 Slightly increasing the vertical angulation will
image more of the unerupted developing permanent teeth and
compensate for the child’s lower palatal vault.
FIGURE 26-8 Occlusal technique. Using a size #2 film to
expose a maxillary occlusal radiograph.
ALARA Radiation Protection
The child’s smaller size places radiation-sensitive tissues closer
to the path of the primary beam of radiation. It is imperative that
a lead/lead equivalent apron and thyroid collar be placed over all
patients, including children. Child-sized lead/lead-equivalent
protective barriers are available commercially; some are decorated with cartoon figures, making these especially childfriendly. Other ALARA (as low as reasonably achievable; see
Chapter 6) protocols that apply to adult patients also apply to
children. These include the use of fast film or digital image
receptors, x-ray beam filtration and collimating devices, and
appropriate exposure settings.
As the bone structure of a child is smaller and less dense than
that of an adult, less radiation is required to produce an acceptable
image. The amount of radiation required for most intraoral exposures
can be reduced by about one-third to one-half of that required for
the same exposure on an adult patient. Reducing the mA setting
(amount of radiation) or the exposure time by one-half of that
used for adult exposures is appropriate for children under 10 years
of age. Exposures on children between the ages of 10 and 15
years can be reduced by approximately one-third. Once the
adolescent reaches 15 or 16 years of age, the exposure settings
should be the same as for an adult patient.
Patient Management
Obtaining quality radiographs on children can be challenging.
The radiographer must be able to communicate and explain the
procedure so that the child understands what is expected. The
child must be able to follow directions and cooperate with the
procedure. The patient management skills of the radiographer
should bring out the child’s natural curiosity and eagerness to
participate.
First impressions are always important and lasting. The
child’s first experience should be pleasant and informative. Usually
it is best to greet and take the child from the reception room to
the x-ray room without the parents. The child should be a willing
participant in the process. Only in emergencies should a child
be forced to undergo dental treatment. If necessary, it is better to
postpone taking radiographs until the next visit than to cause an
unpleasant experience for the child. The child can be told that
they will “be bigger” next time and that the procedure will be
easier now that they have “practiced” for it. Planting a positive
thought is better than risking instilling a fear of dentistry.
When the child patient cannot tolerate image receptor
placement in either the parallel or the bisecting relationships,
the radiographer can often use the occlusal technique to achieve
reasonably acceptable images. Where an image receptor size
#4 is utilized for occlusal radiographs for adults, an intraoral
film size #2 or the equivalent sized digital sensor or phosphor
plate can be used with children (Figure 26-8). The flat image
receptor placement is usually readily accepted by the child
patient. The angulation used for the occlusal technique for children differs slightly from the angles used for adults (Table 26-1).
330TABLE 26-1 Recommended Techniques for the Child Patient if Radiographic Need Is Assessed
DENTITION
CATEGORY
TYPE AND
REGION
IMAGE
RECEPTOR
SIZE
NUMBER
OF IMAGE
RECEPTORS
IMAGE RECEPTOR
PLACEMENT
VERTICAL
ANGULATION
HORIZONTAL
ANGULATION POINT OF ENTRY EXPOSURE
Primary dentition (3 to
6 years
of age)
Bitewing
posterior
#0 or #1 1 on each side Align the anterior edge
of image receptor to
line up behind the distal half of the primary
maxillary or mandibular canine; choose the
most mesially located
canine
+5 to degrees +10 Direct the central rays
perpendicularly
through the primary
first and second
molar embrasure
A spot on the
occlusal plane
between the
primary maxillary
and mandibular
first molars
Reduce exposure to 1/2
the exposure
used for this
projection
on an adult
Primary dentition (3 to
6 years
of age)
Occlusal
anterior
#2 1 on each arch Place long dimension of
image receptor across
the mouth (buccal to
buccal; Figures 26-9
and 26-10)
Maxilla: Direct the central
rays perpendicular to
the imaginary bisector
approximately
degrees
Mandible: Direct the central rays perpendicular
to the imaginary bisector approximately
degrees
-30
+60
Direct the central rays
perpendicular to
patient’s
midsagittal plane
Maxilla: Through a
point at the tip of
the nose toward
the center of the
image receptor
Mandible: Through a
point in the middle
of the chin toward
the center of the
image receptor
Reduce exposure to 1/2
the exposure
used for this
projection
on an adult
Transitional
dentition
(7 to 12
years of
age)
Bitewing
posterior
Prior to
eruption
of the permanent
second
molar: #1
or #2
Prior to eruption
of the permanent second
molar: 1 on
each side
Prior to eruption
of the permanent second molar: Align the
anterior edge of image
receptor to line up
behind the distal half
of the primary or permanent maxillary or
mandibular canine;
choose the most
mesially located
canine (Figure 26-11)
Prior to eruption of the
permanent
second molar:
Direct the central
rays perpendicularly
through the primary
first and second
molar embrasure or,
if erupted, the first
and second
premolar
embrasure
A spot on the
occlusal plane
between the primary maxillary
and mandibular
first molars or, if
erupted, the first
and second premolars to center
the image receptor
within the x-ray
beam
Reduce exposure to 1/2
the exposure
used for this
projection
on an adult
331
After eruption of the
permanent
second
molar: #2
After eruption of
the permanent
second molar:
2 on each side
(1 premolar
bitewing
and 1 molar
bitewing)
After eruption of the
permanent second
molar: Use the same
criteria as for the
adult patient (see
Table 16-3)
+10 degrees After eruption of the
permanent second
molar: Use the same
criteria as for the
adult patient (see
Table 16-3)
After eruption of the
permanent second
molar: Use the
same criteria as
the adult patient
(see Table 16-3)
Reduce exposure by 1/3
to 1/2 the
exposure
used for this
projection
on an adult
Transitional
dentition
(7 to
12 years
of age)
Anterior
periapical
#0 or #1 3 on each arch
(1 centrallateral, 1 right
canine, and
1 left canine)
Maxillary central-lateral incisors: Center
the image receptor to
line up behind the primary or, if erupted,
permanent central and
lateral incisors
(Figure 26-12)
Maxillary central-lateral
incisors:
Paralleling technique—
Direct the central rays
toward the image receptor perpendicularly in
the vertical dimension.
Bisecting technique—
Direct the central rays
toward the imaginary
bisector approximately
+45 to degrees +50
Maxillary centrallateral incisors:
Direct the central
rays perpendicularly
through the maxillary left and right
primary or, if
erupted, permanent
central incisor
embrasure
Maxillary centrallateral incisors:
At the root tips of
the central incisors
to center the
image receptor
within the x-ray
beam
Reduce exposure by 1/3
to 1/2 the
exposure
used for this
projection
on an adult
Mandibular central-lateral incisors: Center
the image receptor to
line up behind the primary or, if erupted,
permanent central and
lateral incisors
(Figure 26-13)
Mandibular central-lateral incisors:
Paralleling technique—
Direct the central rays
toward the image receptor perpendicularly in
the vertical dimension.
Bisecting technique:
Direct the central rays
toward the imaginary
bisector approximately
-20 to degrees -25
Mandibular centrallateral incisors:
Direct the central
rays perpendicularly
through the
mandibular left and
right primary or, if
erupted, permanent
central incisor
embrasure
Mandibular centrallateral incisors:
At the root tips of
the central incisors
to center the
image receptor
within the x-ray
beam
(Continued)
332TABLE 26-1 (Continued)
DENTITION
CATEGORY
TYPE AND
REGION
IMAGE
RECEPTOR
SIZE
NUMBER
OF IMAGE
RECEPTORS
IMAGE RECEPTOR
PLACEMENT
VERTICAL
ANGULATION
HORIZONTAL
ANGULATION POINT OF ENTRY EXPOSURE
Maxillary canine: Center the image receptor
to line up behind the
primary or, if erupted,
permanent canine
(Figure 26-14)
Maxillary canine:
Paralleling technique—
Direct the central rays
toward the image receptor
perpendicularly in the vertical dimension.
Bisecting technique—
Direct the central rays
toward the imaginary
bisector approximately
+55 to degrees +60
Maxillary canine:
Direct the central
rays perpendicularly
at the center of the
canine
Maxillary canine: At
the root tip of the
canine to center
the image receptor
within the x-ray
beam
Mandibular canine:
Center the image
receptor to line up
behind the primary
canine, or, if erupted,
the permanent canine
(Figure 26-15)
Mandibular canine: Paralleling technique—
Direct the central rays
toward the image receptor perpendicularly in
the vertical dimension.
Bisecting technique:
Direct the central rays
toward the imaginary
bisector approximately
-25 to degrees -30
Mandibular canine:
Direct the central
rays perpendicularly
at the center of the
canine
Mandibular canine:
At the root tip of
the canine to center the image
receptor within the
x-ray beam
Transitional
dentition (7
to 12 years
of age)
Posterior
periapical
#1 or #2 Prior to eruption
of the permanent second
molar: 1 in
each quadrant
(4 molar periapicals)
Prior to eruption of the
permanent second
molars:
Maxillary molar—Align
the anterior edge of
image receptor to line
up behind the distal
half of the primary or,
if erupted, permanent
maxillary canine (Figure 26-16)
Prior to eruption of the
permanent second
molars:
Maxillary molar:
Paralleling technique—
Direct the central rays
toward the image receptor perpendicularly in
the vertical dimension
Bisecting technique—
Direct the central rays
toward the imaginary
bisector approximately
+30 to degrees +55
Prior to eruption of the
permanent second
molars:
Maxillary molar:
Direct the central
rays perpendicularly
through the primary
first and second
molar embrasure or,
if erupted, the first
and second premolar
embrasure
Prior to eruption of
the permanent
second molars:
Maxillary molar: At
the root tip of the
primary first
molar, or if
erupted, the root
tip of first premolar to center the
image receptor
within the x-ray
beam
Reduce exposure by 1/3
to 1/2 the
exposure
used for this
projection
on an adult
333
Mandibular molar—Align
the anterior edge of
image receptor to line
up behind the distal half
of the primary or, if
erupted, permanent
mandibular canine
(Figure 26-17)
Mandibular molar:
Paralleling technique:
Direct the central
rays toward the
image receptor perpendicularly in the
vertical dimension
Bisecting technique:
Direct the central
rays toward the
imaginary bisector
approximately
to degrees -20
-15
Mandibular molar:
Direct the central
rays perpendicularly through the
primary first and
second molar
embrasure or, if
erupted, the first
and second premolar embrasure
Mandibular
molar: At
the root tip
of the primary first
molar, or if
erupted, the
root tip of
first premolar to center
the image
receptor
within the
x-ray beam
After eruption of the second permanent molar:
2 in each quadrant (4
premolar and 4 molar
periapicals)
After eruption of the second permanent molar:
Use the same criteria as
the adult patient (see
Table 13-1)
After eruption of the
second permanent
molar: Use the same
criteria as the adult
patient (see
Table 13-1)
After eruption of the
second permanent
molar: Use the
same criteria as the
adult patient (see
Table 13-1)
334 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
Most children react favorably to the authority of a confident, capable operator. Occasionally, a stubborn or frightened
child proves difficult to manage. If such a child does not
respond to firmness, a parent or older brother or sister may
accompany the child into the x-ray room. In fact, if the child is
too small to understand instructions or unable to hold the image
receptor in place, a parent or accompanying adult may have to
assist with holding the image receptor while it is being
exposed. The parent or guardian should be protected with
lead/lead equivalent barriers such as an apron or gloves when
they are in the path of the x-ray beam. The radiographer must
never hold the image receptor in the mouth of a patient during
exposure.
Show-Tell-Do
The use of Show-tell-do (see Chapter 12) is especially useful
with children. Children, and adults, can be naturally fearful
of the unknown. Orienting the child patient to the radiographic equipment will help to alleviate fear and pique
curiosity. The child can be given a film packet to feel and to
handle. It may be unwrapped so that the child can see the
film. Showing the child different image receptor sizes and
then choosing the size that is “just right” for the child’s
mouth may assist with cooperation during placement intraorally. If an image receptor holder is to be used, the child can
be allowed to examine and handle it. The entire procedure
should be carefully explained and rehearsed. The terms used
to describe the radiographic equipment should be on the level
the patient understands. Young children can be told that the
x-ray tube head is the “camera” used to take special x-ray
pictures of the teeth.
Modeling
Modeling, where the child is given the opportunity to observe
the procedure being performed on another patient, is another
successful tool the radiographer may apply to alleviate fear of
the unknown and gain cooperation. The child may observe an
older sibling or parent undergoing the procedure. Of course,
care should be taken to not subject the child to unnecessary
radiation exposure. The child can accompany the radiographer
to the protected location of the exposure button and assist in the
exposure by watching for, and confirming, that the red exposure
indicator lights up.
Communication
Honest communication and good interpersonal skills that are utilized
to gain procedure acceptance and cooperation from the adult can
also be applied to the child patient (see Chapter 12). Praising the
child for his/her cooperation and successful completion of each
step of the procedure will encourage more of the same behavior.
A young child’s attention span can be short, so repeated praise
and instructions given again with each exposure is often necessary.
Young children can be get fidgety and restless, so when the child
is ready, image receptor placement and exposures should be made
as rapidly as possible.
Giving the child a job to do, such as listening for the “beep”
sound to be sure that the x-ray machine worked will allow the
patient to be a willing participant in the process. Giving the child
a sense of control over the procedure will often boost cooperation.
However, the radiographer should be careful about which procedures to maintain authority over. Allowing the patient to hold and
examine the image receptor holder device is reasonable; giving
the child patient permission to place the holder intraorally where
he/she wants to may lead to less cooperation.
Many strategies that apply to managing patients with special needs, presented in Chapter 27, will apply to the child
patient as well. The easiest and most comfortable exposures,
usually radiographs of the maxillary anterior teeth, can be
exposed first to gain the child’s confidence and to get the
child accustomed to having the image receptor in the mouth.
Distraction techniques such as telling the child a story during
the procedure; asking the child to take a deep breath and hold
it while you count down from five to zero, allowing time to
make the exposure; and palpating the tissues with an index
finger to massage and desensitize sensitive mucosa and familiarize the patient with where the image receptor will be placed
are strategies that help make the radiographic experience a
comfortable one.
Interpretation
The radiographer must possess a working knowledge of eruption
patterns and tooth morphology to read radiographs that record
primary and developing permanent teeth. Figure 26-9 through
Figure 26-17 illustrates the teeth and structures most likely to
be recorded on radiographs of children with primary and transitional (mixed primary and permanent) dentition.
1
2
3 4
5
7 6
FIGURE 26-9 Maxillary anterior occlusal radiograph of
primary dentition exposed with size #2 film. (1) Primary canine.
(2) Unerupted permanent lateral incisor. (3) Unerupted permanent
central incisors—note that root formation has not started yet. (4) Thin
radiolucent line indicating the median palatine suture. (5) Partially
resorbed root of primary central incisor. (6) Primary central incisors.
(7) Primary lateral incisor.
CHAPTER 26 • RADIOGRAPHIC TECHNIQUES FOR CHILDREN 335
1
2
3
4
FIGURE 26-10 Mandibular anterior occlusal radiograph
of primary dentition exposed with size #2 film. (1) Alveolar bone.
(2) Partially erupted permanent central incisors. (3) Primary teeth.
(4) Unerupted permanent lateral incisors.
1
2
4
4
3
FIGURE 26-11 Posterior bitewing radiograph of transitional
(mixed primary and permanent) dentition (1) Primary maxillary
canine, first and second molars. (2) Primary mandibular canine, first
and second molars. (3) Permanent maxillary and mandibular molars.
(4) Note that this small size film does not adequately image the area
of the developing premolars.
1
2
3
4
FIGURE 26-12 Maxillary central-lateral incisors periapical
radiograph of transitional (mixed primary and permanent)
dentition (1) Primary lateral incisor. (2) Unerupted permanent
central incisors. (3) Roots of primary central incisors showing signs
of physiological resorption. (4) Primary central incisors.
1
2
3
4
FIGURE 26-13 Mandibular central-lateral incisors
periapical radiograph of transitional (mixed primary and
permanent) dentition (1) Unerupted permanent lateral incisor. (2)
Caries on mesial surface of primary lateral incisor. (3) Permanent
central incisors. (4) Large open apex on all permanent teeth,
indicating that root formation is still in progress. Root formation is
generally not complete until about two or three years following tooth
eruption.
336 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
1
2 3
4
5
FIGURE 26-14 Maxillary canine periapical radiograph
of transitional (mixed primary and permanent) dentition
(1) Primary canine. (2) Unerupted first premolar. (3) Unerupted
permanent canine still in a follicle as indicated by radiolucency
surrounding the crown. (4) Permanent central incisor. (5) Permanent
lateral incisor, which appears to be tipped distally and overlapping
with deciduous canine.
1
6
2
3
4
5
FIGURE 26-15 Mandibular canine periapical radiograph
of transitional (mixed primary and permanent) dentition
(1) Primary lateral incisor. (2) Radiolucent areas on mesial and distal
of primary canine. A visual examination is needed to determine if this
indicates caries or restorative materials that mimic caries
radiographically (see Chapter 21). (3) Primary first molar.
(4) Unerupted first premolar. (5) Unerupted permanent canine.
(6) Unerupted permanent lateral incisor.
1
2 3
4
6 5
FIGURE 26-16 Maxillary molar periapical radiograph
of transitional (mixed primary and permanent) dentition
(1) Permanent first molar. (2) Unerupted second premolar.
(3) Unerupted first premolar. (4) Primary canine. (5) Primary first
molar (note that the roots are almost completely resorbed).
(6) Primary second molar.
1
2
3
4
5
FIGURE 26-17 Mandibular molar periapical radiograph
of transitional (mixed primary and permanent) dentition
(1) Unerupted first premolar. (2) Primary first molar with partial
resorption of distal root. (3) Primary second molar. (4) Permanent
first molar. (5) Unerupted second premolar.
CHAPTER 26 • RADIOGRAPHIC TECHNIQUES FOR CHILDREN 337
Sample illustrations are provided to assist with learning to
interpret radiographs of children with primary and transitional
(mixed primary and permenant) dentition.
RECALL—Study questions
1. List five conditions that would indicate the need for
dental radiographs on the child patient.
a. ______________
b. ______________
c. ______________
d. ______________
e. ______________
2. Under which of these conditions would dental radiographs most likely NOT need to be exposed?
a. When the child presents with poor self-care and suspected caries.
b. When the child is under 12 years of age.
c. When the proximal surfaces of the teeth are visible
clinically.
d. When the child has accidentally fallen, but there is
no apparent damage to the primary teeth.
3. According to the evidence-based selection criteria
guidelines listed in Table 6-1, which of these intervals is
recommended for posterior bitewing radiographs on a
10-year-old child recall patient who presents with good
self-care and no evidence of clinical caries?
a. 6–12 months
b. 12–24 months
c. 18–36 months
d. 24–36 months
4. Each of the following need to be considered when deciding what size image receptor to use on a child EXCEPT
one. Which one is the EXCEPTION?
a. Cooperation level
b. Size of the dental arches
c. Size of the mouth opening
d. Amount of plaque present
5. Which image receptor size would be the easiest to position for a bitewing radiograph on a 5-year-old patient?
a. #0
b. #1
c. #2
d. #4
6. Which of the following is the best reason to use the largest
size intraoral image receptor that the child will tolerate?
a. So that a lesser number of image receptors will have
to be exposed
b. To be able to use the paralleling technique
c. So that the radiation exposure can be reduced
d. To image an increased amount of the tissues
REVIEW—Chapter summary
Children have the same basic needs for oral health care as do
adults. Radiographic techniques and the types of projections
used to image the oral cavity of the child patient do not differ
significantly from those used for adult patients. The child
patient presents with unique characteristics, such as a smaller
oral cavity and special behavioral considerations that often
require adaptation to standard procedures.
Radiographs for the child patient may be indicated for the
detection of congenital dental abnormalities, to assess growth
and development, and to detect and diagnose diseases and the
effect of trauma. Selection criteria guidelines suggest that radiographs on children may not be necessary until all the primary
teeth have erupted unless an emergency or suspected pathology
exists. Once teeth have erupted in such a manner that the proximal surfaces of the teeth cannot be examined clinically for
caries, radiographs may need to be exposed.
The number and size of image receptor used for radiographs for the child patient will depend on the child’s age, size
of the oral cavity, and cooperation level. Image receptor size #0
or #1 is usually used for bitewing radiographs for patients with
primary dentition, prior to the eruption of the first permanent
molars. Image receptor size #2 is usually used for patients with
a transitional (mixed primary and permanent) dentition.
Occlusal radiographs may be substituted for periapicals on
children if necessary. After the eruption of the permanent second molars, the bitewing and full mouth surveys recommended
for the child patient are the same as those recommended for an
adult patient.
Evidence-based selection criteria recommend panoramic
radiographs for the assessment of growth and development.
Panoramic or lateral jaw (mandibular oblique lateral) extraoral
radiographs may sometimes be acceptable substitutes for intraoral radiographs for the child patient who cannot tolerate intraoral image receptor placement.
As with the adult patient, the paralleling method is the
technique of choice for use with children; however, image
receptor placement may be easier with the bisecting method.
Because the bone structure of a child is smaller and less
dense than that of an adult, less radiation is required to produce an acceptable image. Exposure settings for radiographs
on children under 10 years of age can be reduced by one-half
of that used for adult exposures. Exposure settings for radiographs on children 10 to 15 years of age can be reduced by
one-third of that used for adult exposures. Adolescents 15 or
16 years of age and older require the same exposure settings
as an adult patient.
Show-tell-do and modeling are valuable patient management tools that can aid the radiographer in taking quality radiographic images. Orienting the child patient to the radiographic
equipment will help alleviate fear of the unknown. Good communication and demonstration of authority are imperative
when interacting with children. Most children react favorably
to the authority of a confident, capable operator.
338 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
7. Which of the following is the suggested number and
size of projections to use for a 3-year-old patient with
primary dentition?
a. Two bitewing and two occlusal radiographs
b. Two bitewing and two periapical radiographs
c. Two bitewing and four periapical radiographs
d. Four bitewing and 10 periapical radiographs
8. Which of the following is the suggested number and
size of projections to use for a 10-year-old patient
with transitional (mixed primary and permanent)
dentition?
a. Two bitewing and eight periapical radiographs
b. Two bitewing and 10 periapical radiographs
c. Four bitewing and 10 periapical radiographs
d. Four bitewing and 14 periapical radiographs
9. Which of the following is the suggested number and
size of projections to use for a 15-year-old patient with
permanent dentition?
a. Two bitewings and six periapical radiographs
b. Four bitewing and eight periapical radiographs
c. Four bitewing and 10 periapical radiographs
d. Four bitewing and 14 periapical radiographs
10. When a child patient cannot tolerate intraoral placement
of the image receptor for exposure of a periapical radiograph, which of the following may sometimes be an
acceptable substitute?
a. Bitewing
b. Panoramic
c. Lateral jaw
d. Both b and c
11. If well tolerated, which of the following techniques
will provide the best-quality images on the child
patient?
a. Panoramic
b. Occlusal
c. Paralleling
d. Bisecting
12. What slight change in angulation is usually required
when using the bisecting technique on a child
patient?
a. Increase the vertical angulation
b. Decrease the vertical angulation
c. Direct the horizontal angulation mesiodistally
d. Direct the horizontal angulation distomesially
13. Which of the following image receptors is recommended for an occlusal radiograph on an 8-year-old
patient?
a. #0
b. #2
c. #3
d. #4
14. The exposure settings for children under the age of 10
years should be
a. reduced by one-half the exposure used for adults.
b. reduced by one-third the exposure used for adults.
c. three-fourths the exposure used for adults.
d. the same exposure as used for adults.
15. The exposure settings for children between the ages of
10 and 15 years should be
a. reduced by one-half the exposure used for adults.
b. reduced by one-third the exposure used for adults.
c. three-fourths the exposure used for adults.
d. the same exposure as used for adults.
16. The exposure settings for children over the age of 16
years should be
a. reduced by one-half the exposure used for adults.
b. reduced by one-third the exposure used for adults.
c. three-fourths the exposure used for adults.
d. the same exposure as used for adults.
17. Allowing the child patient to observe a sibling or parent undergoing the radiographic procedure may help to
alleviate fear of the unknown and promote cooperation.
This patient management strategy is called modeling.
a. The first statement is true. The second statement is false.
b. The first statement is false. The second statement is true.
c. Both statements are true.
d. Both statements are false.
18. When taking a series of periapical radiographs on an
11-year-old patient, placing and exposing which of the
following first will most likely aid in gaining the
patient’s confidence and cooperation?
a. Mandibular molar
b. Mandibular canine
c. Maxillary molar
d. Maxillary central-lateral incisors
REFLECT—Case study
The public health clinic where you have volunteered to work
one day a week has just received funding to begin providing
oral health care services to children. Currently the exposure
times for radiographic projections posted near the x-ray unit
control panels list only the following impulse times for adults.
Based on what you learned in this chapter, design an exposure
setting chart that lists the impulse timer settings that would be
appropriate for children. Design your chart to include children of all ages: under age 10 and between the ages of 10 and
15. Current settings for adult patients are as follows:
Film speed: F
PID length: 12 in. (30.5 cm)
mA: 7
kVp: 70
CHAPTER 26 • RADIOGRAPHIC TECHNIQUES FOR CHILDREN 339
RELATE—Laboratory application
Observe the exposure charts that are used in your clinical facility. Write down the settings that are being recommended for use
with adults and with children. How many categories of settings
did you find? Are there parameters given for the settings? That
is, are age, size of the patient, or dentition parameters listed to
base the settings on? Compare and calculate the difference
between the adult and child settings used at your facility. Do the
differences match the recommendations presented in this chapter? What is the basis for the recommended settings at your
facility? That is, why were they selected? After analyzing the
settings and comparing them to the recommendations in this
chapter, write a brief summary that would explain the use of different settings to a concerned parent.
REFERENCES
American Academy of Pediatric Dentistry. (2005). Guideline
on prescribing dental radiographs for infants, children,
adolescents, and persons with special health care needs.
Pediatric Dentistry, 27(reference manual), 185–186.
Eastman Kodak Company. (2002). Successful intraoral
radiography. N-418 CAT No. 103. Rochester, NY:
Author.
Pinkham, J., Casamassimo, P., Fields, H. W., McTigue, D. J.,
& Nowak, A. J. (2005). Pediatric dentistry: Infancy
through adolescence (4th ed.). St. Louis, MO: Elsevier
Saunders.
Thomson, E. M. (1993). Dental radiographs for the child
patient. Dental Hygiene News, 6, 19–20, 24.
Thomson, E. M. (2008). Panoramic radiographs and the
pediatric patient. Part 1. Dimensions of Dental Hygiene,
6(2), 26–29.
White, S. C., & Pharoah, M. J. (2004). Oral radiology:
Principles and interpretation (6th ed.). St. Louis, MO:
Elsevier.
Impulses
Bitewings Adult Child (under 10 yrs) Child (10–15 yrs)
Posterior 20 — —
Anterior 16 — —
Periapicals
Maxillary anterior 18 — —
Maxillary premolar 22 — —
Maxillary molar 24 — —
Mandibular anterior 16 — —
Mandibular premolar 18 — —
Mandibular molar 20 — —
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define key words.
2. Discuss five actions for managing the apprehensive patient.
3. Identify the areas of the oral cavity that are most likely to initiate the gag reflex.
4. List the two stimuli that commonly initiate the gag reflex.
5. Describe five methods to reduce psychogenic stimuli to control the gag reflex.
6. Describe four methods to reduce tactile stimuli to control the gag reflex.
7. Discuss ways to manage radiographic procedures for the older adult patient.
8. Discuss ways to manage radiographic procedures for the patient with motor disorders and
conditions of involuntary movement.
9. Discuss ways to manage radiographic procedures for the patient with disabilities.
10. Explain necessary radiographs for the cancer patient.
11. Explain necessary radiographs for the pregnant patient.
12. Value the need for cultural sensitivity.
KEY WORDS
Angular cheilitis
Apprehensive
Cultural barriers
Disability
Gag reflex
Hypersensitive gag reflex
Speech reading
Managing Patients
with Special Needs
CHAPTER
OUTLINE
 Objectives 340
 Key Words 340
 Introduction 341
 The Apprehensive
Patient 342
 A Hypersensitive
Gag Reflex 342
 Aging 344
 Motor Disorders
and Conditions
of Involuntary
Movement 344
 Disabilities 345
 Cancer 346
 Pregnancy 346
 The Culturally
Sensitive
Radiographer 346
 Review, Recall,
Reflect, Relate 347
 References 349
CHAPTER
27
CHAPTER 27 • MANAGING PATIENTS WITH SPECIAL NEEDS 341
TABLE 27-1 Conditions Prompting Alterations to Radiographic Procedures
CONDITION ANTICIPATED PROBLEM MANAGEMENT STRATEGY
Apprehensive Ability to tolerate placement of the
image receptor
Develop a rapport
Project confidence
Maintain authority
Be organized
Reassure patient
Hypersensitive
gag reflex
Ability to tolerate placement of the
image receptor
Do not suggest gagging
Empathize
Use the power of suggestion
Apply distraction techniques
Give the patient breathing instructions
Reduce tactile stimuli
• Begin exposures in the anterior regions
• Place image receptor firmly and expertly
• Confuse the senses
• Utilize special products
Substitute extraoral radiographs as needed
Aging Angular cheilitis (soft tissue cracking of lips)
Decreased muscle function
Unsteadiness, tremors
Dementia (reduced attentiveness to
instructions)
Smaller image receptor; lighter-weight image receptor holder; use
of edge cushion products
Set exposure to increase radiation and decrease exposure time
Utilize caregiver as assistant to stabilize image receptor and/or
patient
Substitute extraoral radiographs
Motor disorders and
conditions of
involuntary movement
Ability to remain still throughout the exposure Set exposure to increase radiation and decrease exposure time
Utilize caregiver as assistant to stabilize image
receptor and/or patient
Wheelchair-bound Positioning patient within the range of the
x-ray unit extension arm and tube head
Transfer the patient to the dental chair when possible
Visual impairment Ability to communicate instructions to gain
patient cooperation
Ability to prevent apprehension of the unknown
Patient personal eyewear may be in the path of
the central ray
Explain each step of the procedure
Use touch to explain equipment and procedures
Announce when exiting and entering the room and explain why
Allow the patient to wear their familiar eyewear whenever possible;
explain the need to remove glasses; allow the patient to
remove glasses
Hearing impairment Ability to understand and follow directions Be creative in finding alternate methods of communication
Cancer Patient hesitant to undergo dental radiographic
procedure
Explain the use of evidence-based selection criteria
Pregnancy Patient hesitant to undergo dental radiographic
procedure
Explain the use of evidence-based selection criteria
Discuss necessary and elective radiographic procedures
Explain the need for, and use lead/lead equivalent thyroid collar
Culturally diverse Language, beliefs, traditions and familiar
influences can be barriers to care
Exhibit an accepting, nonjudgmental attitude
Make an effort to understand the culture
Introduction
Each patient presents with unique characteristics. In addition to
oral manifestations, the dental radiographer should be familiar
with possible medical, physical, psychological, emotional, and
cultural conditions that may require additional knowledge and
skills to successfully produce diagnostic quality radiographs
while practicing ALARA (as low as reasonably achievable; see
Chapter 6).
The purpose of this chapter is to present some of these
conditions that the radiographer must manage to produce
quality radiographs. Recommendations based on current
research for exposure of special conditions will be presented
(Table 27-1).
342 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
The Apprehensive Patient
Apprehensive means to be anxious or fearful about the future.
Apprehensive patients may consider the radiographic procedure
to be unpleasant. These patients may have had a negative experience with a past procedure, which causes them to project those
negative feelings onto the current radiographer. Therefore, it is
important that the apprehensive patient’s contact with the dental
radiographer be pleasant and reassuring.
It is equally important that the radiographer not project
his/her own negative feelings or experiences onto the patient. If
the radiographer has personal views regarding the experience
as uncomfortable or not necessary, he/she must not assume that
the patient shares in those views. Most patients are not apprehensive about radiographic procedures, and the radiographer
should not say or do anything that would prompt the patient to
become anxious.
To reduce a patient’s apprehension, the dental radiographer
should
• Develop a rapport. Take the time to explain the procedure
and allow the patient to ask questions. A conversation that
demonstrates attentive listening and empathy can help relax
the patient.
• Project confidence. A skilled radiographer who demonstrates confidence will gain the patient’s trust and cooperation. A patient’s apprehension is increased when the operator
appears unsure of him/herself.
• Maintain authority. The radiographer should maintain
control over the procedure. Be gentle, but firm. The patient
who trusts in the radiographer’s ability will be less anxious. For example, if placement of an intraoral image
receptor is uncomfortable, and the radiographer allows the
patient to tell the radiographer how it should be placed,
instead of alleviating patient apprehensiveness, the operator may actually increase it. The patient may now feel
responsible for directing the procedure and may become
increasingly anxious that the radiographs may not come
out right.
• Be organized. Progress through the procedure rapidly and
accurately. For example, expose the easier maxillary anterior projections first, and then progress to the more difficult
posterior areas.
• Reassure the patient. Compliment apprehensive patients
on their cooperation. Thank them for their cooperation, even
when the procedure may have been uncomfortable.
A Hypersensitive Gag Reflex
The gag reflex is a protective mechanism that serves to clear
the airway of obstruction. The receptors for the gag reflex are
located in the soft palate and lateral posterior third of the
tongue. Two reactions occur prior to the gag reflex. The first is
a cessation of respiration, and the second is a contraction of the
muscles of the abdomen and the throat.
All patients have gag reflexes, but some are more sensitive
than others. A hypersensitive gag reflex is probably the most
troublesome problem the dental radiographer may encounter.
Two stimuli that must be diminished or eliminated to reduce
gagging are
1. Psychogenic stimuli. Originating in the mind; may result
from the suggestion of gagging or as a result of a past experience of gagging.
2. Tactile stimuli. Originating from touch; a physical reaction
to a feeling of the airway being blocked.
Reducing Psychogenic Stimuli
To help avoid a hypersensitive gag reflex that originates in the
patient’s mind, the radiographer should apply all the suggested
behaviors just explained for alleviating patient apprehensiveness. If the patient reports a past experience with gagging during
the radiographic procedure, or you suspect that a gagging reflex
will occur, the following suggestions may help to prevent its
occurrence:
• Do not suggest gagging. The dental radiographer should
not ask the question, “Are you a gagger?” The power of suggestion is a strong psychogenic stimulus and can initiate the
gag reflex. Unless the patient brings it up, do not mention it.
• Empathize. If the patient brings up the subject of gagging,
do not dismiss their concern as “all in the mind.” Instead,
empathize with their response and explain that some tricks
and techniques have been shown to help avoid stimulating
the gag reflex and that you will individualize these to help
them control their gag reflex.
• Use the power of suggestion. When applying these tricks
and techniques, explain them to the patient. Letting the
patient know that you are altering treatment to help them
manage the gag reflex will increase the likelihood of success. The gagging patient will often be embarrassed by their
involuntary reaction and most are willing to accept any
methods you offer to help them regain control.
• Apply distraction techniques. There are many ways to
divert the patient’s attention away from the oral cavity. This
can be done by maintaining an engaging dialogue or telling
the patient to think of something pleasant, such as their
favorite vacation. However, if the gag reflex has been identified, it may be better to tell the patient that you are going
to give him/her a distraction task to perform. For example,
the patient may be instructed to bite hard on the image
receptor holder’s biteblock; raise an arm or clench a fist; or
press the head back against the head rest of the treatment
chair. Anything that helps to divert the patient’s attention
from the oral cavity may lessen the likelihood of initiating
the gag reflex (Figure 27-1).
• Give the patient breathing instructions. A gag reflex is
often stimulated by a sense of not being able to breathe.
Explain this to the patient and together, plan a breathing
exercise that the patient can concentrate on during placement of the image receptor. For example, the patient may be
coached to breathe deeply through the nose or the mouth; to
hum a familiar song; or to hold the breath while counting to
10 slowly, by which time the radiographer should have completed the exposure.
CHAPTER 27 • MANAGING PATIENTS WITH SPECIAL NEEDS 343
Reducing Tactile Stimuli
Some patients have an accentuated gag reflex because of
hypersensitive pharyngeal tissues. Chronic sinus problems
and postnasal drip can contribute to gagging as mucus and
saliva accumulate into the nasopharygeal area. The dental
radiographer can reduce tactile stimuli by use of the following
techniques.
• Begin exposures in the anterior regions first. Anterior
image receptor placements are less likely to initiate the
gag reflex. Positioning the image receptor in the maxillary
molar region is more likely to initiate the gag reflex.
When exposing a series of bitewing radiographs, expose
the premolar radiograph before the molar. It is often easier
to prevent a gag reflex than to subdue it once excited.
Placing the image receptor in the anterior regions first
allows the patient to get used to the procedure, builds
acceptance, and will usually permit the radiographer to
proceed successfully to the more difficult posterior placements. Additionally, fears from psychic stimuli are most
likely to have been forgotten by the time the maxillary
molar exposure is made.
• Place the image receptor firmly and expertly. For all
projections, carry the image receptor into the mouth parallel with the plane of occlusion. When in proper position,
rotate into place against the appropriate structures. Retain
in position without movement. Avoid sliding the image
receptor across sensitive oral mucosa (soft tissue lining of
the oral cavity).
• Use the bisecting technique. (See Chapter 15.) Because a
gag reflex is sometimes excited by placement of the image
receptor, using the bisecting technique may help prevent
gagging. Placing the image receptor close to the lingual
surface of the teeth and therefore not parallel to the long
axes of the teeth may be less likely to stimulate a gag reflex
on some patients.
• Confuse the senses. Stimulating the oral mucosa with
digital palpation (rubbing with the finger) serves two purposes. When the radiographer places a finger in the area to
simulate for the patient where the image receptor will be
placed, the patient can experience what the actual placement will feel like. Second, palpation helps to massage
and desensitize the soft tissue to make placement of the
image receptor feel less foreign. Another technique that
helps confuse the senses and lower the risk of gagging is
to instruct the patient to rinse with cold water, ice cubes,
or an antimicrobial oral rinse product just prior to image
receptor placement. Placing table salt on the middle or tip
of the patient’s tongue has been shown to be effective at
reducing the gag reflex. When introducing any of these
agents, care must be taken to first be sure that there are no
contraindications for their use. For example, the patient’s
teeth may be sensitive to cold; and the hypertensive
patient (the patient with high blood pressure) may be on a
salt-restricted diet.
• Use special products. A different image receptor holder
may be successful at avoiding or managing a patient with a
hypersensitive gag reflex. Different patients may find different image receptor holders more comfortable than others. Additionally, some products on the market, such as film
packet edge protectors and plastic barriers for digital sensors, reduce the edge sharpness that some patients report
stimulating a gag reflex (Figures 27-2 and 27-3).
Extreme Cases of the Gag Reflex
Occasionally, the radiographer will encounter a patient with a
hypersensitive gag reflex that cannot be managed. The radiographer may be able to substitute a smaller-sized image receptor,
such as a #1 or #0 for the standard #2 size. The radiographer
should take as many intraoral radiographs as possible and then
supplement these with extraoral radiographs.
In rare cases the dentist may prescribe the use of a topical
anesthetic to numb the areas causing the patient to gag. However,
some patients experience an increased anxiety as the result of
this numbing sensation, especially in the soft palate and oral pharyngeal area. Additionally, the risks and contraindications of the
topical anesthetic must be considered.
FIGURE 27-2 Edge protectors. Applying a commercial product
to reduce the edge sharpness of the film packet.
FIGURE 27-1 Distraction techniques. To help control a gag
reflex, this patient has been given an exercise to bend and straighten her
index finger. She has been instructed to keep a steady motion while
continuing to watch her finger.
344 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
FIGURE 27-3 Edge protectors. Film is available with
commercially applied edge softeners.
Aging
Normal changes in the body due to aging do not necessarily
mean that all older adult patients will present with unique conditions that require alterations in the radiographic procedure.
However, the dental radiographer should be aware of an
increased incidence of conditions and diseases such as angular
cheilitis (fissuring and cracking of the soft tissue at the corners
of the mouth), missing teeth (see Chapter 28), hearing impairment, arthritis, stroke, and physical impairment that are seen
increasingly with aging. Soft tissue changes in the lips may
prevent accurate image receptor placement. Muscle function
that diminishes with aging, resulting in unsteadiness and
tremor, may present a barrier to holding still during exposures.
Residual effects of stroke, such as paralysis, may involve the
ability to move the tongue. Alzheimer’s disease—which often
results in inattentiveness to instructions, loss of coordination,
and other motor abnormalities, including exaggerated
reflexes—should be taken into consideration when planning to
expose radiographs.
It is important to communicate with the older adult patient
to ensure that they can follow instructions for a successful outcome to the radiographic procedure. Some of the alterations
suggested earlier for managing the gag reflex will aid image
receptor placement for the older adult patient. These include
using a smaller, lighter-weight image receptor holder, using a
smaller image receptor, and applying a commercial product that
reduces image receptor edge sharpness.
To assist with possible patient movement that occurs as the
result of slight tremors or unsteadiness, the exposure settings may
be manipulated to provide the appropriate amount of radiation in
the shortest period of time. This is discussed in detail in the next
section. If the patient cannot hold still, a caregiver or family member may need to help steady the patient. The assistant must be
offered protective barriers such as lead/lead-equivalent gloves,
aprons, or shields. The dental radiographer must never hold the
image receptor in the patient’s mouth during the x-ray exposure.
Extraoral radiographs may prove to be an acceptable substitute if the patient’s head can be stabilized throughout the duration of the exposure. Head stabilization may be possible with
certain panoramic x-ray machines that have secure head positioner guides. It is important to note that in later stages of osteoporosis, the loss of stature and spinal deformity that creates a
stooping posture will often make the use of the panoramic procedure difficult (see Chapter 30).
Motor Disorders and Conditions
of Involuntary Movement
Many conditions present with unsteadiness and tremor that
require careful consideration prior to exposing radiographs. In
addition to the considerations listed earlier, patients who present with Parkinson’s disease, Bell’s palsy, cerebral palsy, multiple sclerosis, and myasthenia gravis (a neuromuscular disease
characterized by weakened muscles, especially of the face and
oral cavity) require careful assessment as to their ability to
undergo a radiographic examination. If the possibility of movement during the exposure is identified, the exposure settings—
the milliamperage (mA) and the exposure time—may be adjusted
to decrease the time required for exposure by increasing the
amount of radiation generated. As you will recall in Chapter 3,
the mA setting controls the amount of radiation generated. By
increasing the mA, the x-ray machine will generate more radiation. With this increase in radiation, the exposure time may be
decreased (Table 27-2). The guidelines to adjust these settings
are explained in Chapter 3.
Disabilities
A disability is defined as a physical or mental impairment that
substantially limits one or more of an individual’s major life
activities. The dental radiographer must be prepared to accommodate patients with disabilities. When treating a patient with a
disability
• Talk directly to the patient. Do not ask the patient’s caregiver questions that should be directed to the patient. For
TABLE 27-2 Suggested Exposure Times When
Changing the mA Setting* for Adult Patients
REGION TO BE
RADIOGRAPHED
IMPULSE SETTING
7 mA 10 mA 15 mA
Maxillary anterior periapical 14 10 7
Maxillary posterior periapical 20 14 9
Mandibular anterior periapical 12 8 6
Mandibular posterior periapical 16 11 8
Anterior bitewing 12 8 6
Posterior bitewing 16 11 8
*F-speed film; 12 in. (20 cm) PID; 70 kVp.
CHAPTER 27 • MANAGING PATIENTS WITH SPECIAL NEEDS 345
example, do not say to the caregiver, “Can he (or she) stand
up?” Instead, speak directly to the patient and say, “Can
you stand up?”
• Offer assistance to disabled patients. Ask the patient how
you can best assist them.
• Do not ask personal questions about the patient’s disability.
The Patient Who uses a Wheelchair
The difficulty encountered with the patient who uses a wheelchair is getting the patient into position close enough to the xray unit (Figure 27-4). Care should be taken to be sure that the
extension arm can support the tube head in position without
drifting. Unless the patient is in a total-support wheelchair, it
may be best to transfer the patient to the dental chair.
Patients can be transferred from the wheelchair to the dental
chair by use of the following techniques:
• Patients who can temporarily support their weight are
transferred to the dental chair by placing the wheelchair
alongside the dental chair. Set the brakes of the wheelchair
and elevate the dental chair to the height of the wheelchair. Move the dental chair arm from between the chairs.
Have the patient move or slide sideways into the dental
chair with the caregiver and radiographer assisting.
• If the patient is unable to support their weight, the
immobile patient may be transferred to the dental chair by
radiographer and caregiver. With one taking a position
behind the patient and the other facing the patient, the radiographer and caregiver may lift the patient from the wheelchair into the dental chair.
The Patient with a Visual Impairment
The visually impaired or blind patient requires special consideration during the radiographic procedure. The radiographer must
communicate using clear verbal explanations of each step of the
procedure before performing it. When taking multiple exposures,
it is important to maintain verbal contact to reorient the patient
each time you must exit and reenter the oral cavity. Using touch,
the radiographer can demonstrate placement of the image receptor and the feel of the receptor holder prior to its placement to
help eliminate the feeling of anxiety when facing the unknown.
The personal eyewear worn by the patient with a visual
impairment may have to be temporarily removed if the glasses
will be positioned within the primary beam. Explain the need
for this to the patient. Allow the patient to remove his/her own
glasses. Immediately following the exposures, allow the patient
to resume wearing their personal eyewear.
Maintain communication with the blind patient. Explain why
you are leaving the room when you go to the darkroom to process
the films. Immediately announce your return to the operatory by
speaking directly to the patient.
FIGURE 27-4 Panoramic unit that can accommodate
wheelchair-bound patients. (Courtesy of Planmeca.)
PRACTICE POINT
Never gesture to another person in the presence of a patient
who is blind. Blind persons are sensitive to gesture communication and may feel you are “talking behind their back.”
The Patient with a Hearing Impairment
Communication is vitally important to the success of all radiographic procedures. The radiographer must give the patient
explicit detailed instructions before, during, and at the end of each
placement and exposure. The production of quality radiographs
depends on the patient’s ability to understand and follow these
instructions. Communication with the hearing-impaired patient
requires that the radiographer be aware of what method of communication works best for the patient. The radiographer should
always ask a hearing-impaired or deaf patient how he/she prefers
to communicate. Several options are
• Use written instructions.
• Ask a relative or caregiver to act as an interpreter.
• Use gestures.
If the patient can use speech reading (reading lips), face
the patient and speak slowly and clearly, allowing the patient
to read your facial expressions and gestures. Because a face
mask is recommended as PPE (personal protective equipment;
see Chapter 10) during radiographic procedures, it is important
that the patient and the radiographer agree on the meaning of
certain gestures before beginning the procedure. In fact, the
346 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
A B
FIGURE 27-5 Example of signing. The radiographer is letting this hearing-impaired patient know that she is
doing a good job cooperating with the radiographic procedure. (A) Right hand on chin. (B) Drops to left hand open
palm. Communicating “Good patient.”
may lead to altered guidelines on dental radiographs for
pregnant females. The American Dental Association (ADA)
currently recommends that necessary dental radiographs that
help the dentist diagnose and treat oral disease still be
exposed on pregnant females; and that elective dental x-rays
be postponed for the pregnant female until after delivery. The
ADA strongly recommends the use of lead/lead-equivalent
thyroid collars in conjuction with lead apron barriers for all
patients, and especially for pregnant females and women of
child-bearing age.
hearing-impaired patient will appreciate the radiographer who
takes the time to learn a few of the gestures or sign language
he/she uses to communicate (Figure 27-5).
If the patient uses a hearing aid, it may have to be removed
prior to the panoramic radiographic procedure (see Chapter 30).
Explain the upcoming radiographic procedures before asking
the patient to remove the hearing aid because communication
will be diminished when it is removed.
Cancer
There is often a concern whenever the necessity arises to expose
dental radiographs on any patient who is currently receiving or
has recently undergone radiation therapy. The patient is often
reluctant to receive additional radiation, no matter how minimal,
and the dentist may be hesitant to prescribe dental radiographs.
Likewise, the radiographer making the exposure may feel apprehensive about the procedure.
The patient should be told that the concerns for radiation
safety are shared. Although the patient may already have received
large therapeutic doses of radiation, this is not a contraindication to exposing dental radiographs, provided that they are
determined to be necessary to make an oral diagnosis. The additional radiation that the patient would receive is minimal, and
its use is justified if the patient benefits.
Pregnancy
Prior to a research report published by the American Medical
Association (AMA) in 2004, the potential effects of dental
radiation exposure centered on the possibility of exposure to
the developing fetus. Then JAMA (Journal of the American
Medical Association) published research that investigated the
effect on pregnancy outcomes of radiation exposure of the
hypothalamus and the pituitary and thyroid glands that suggests that dental radiation exposure is associated with fullterm low-birth-weight infants. More research in this area
The Culturally Sensitive Radiographer
The diversity of culture in today’s global society means that the
radiographer is more and more likely to find him/herself performing radiographic examinations on patients of a variety of racial,
ethnic, and cultural backgrounds. Educating these patients regarding the role radiographs play in the diagnosis and treatment of
oral diseases requires that the radiographer be aware of possible
cultural barriers, such as language, beliefs, traditions, and familiar influences.
Because good communication is the foundation on which
quality radiographs are produced, the radiographer should strive
to develop a better understanding of the cultures most likely to be
encountered in the community where the oral health care practice
is located. To assist in developing cultural sensitivity the radiographer should take into consideration the patient’s
• Communication style. Is eye contact considered respectful or a sign of rudeness? Does the patient consider discussing the oral cavity personal and private? Is the patient
comfortable having a family member translate personal or
sensitive information?
• Comfortable personal space zone. Does touch convey
acceptance, or is it offensive? Is the patient uncomfortable
being treated by a professional of the opposite gender?
Does the patient wear certain articles of clothing or spiritual
CHAPTER 27 • MANAGING PATIENTS WITH SPECIAL NEEDS 347
PRACTICE POINT
Do not confuse the terms “elective” and “unnecessary.” The
evidence-based selection guidelines (see Chapter 6) used by
dentists to help with the decision to expose radiographs on all
types of patients prevent the exposure of unnecessary radiographs. Unnecessary radiographs should never be exposed
on any patient. When considering radiographs for the pregnant female, the ADA recommends that elective dental x-rays
be postponed until after delivery. Although the ADA Council
on Scientific Affairs publication, “The use of dental radiographics: update and recommendations” (Journal of the
American Dental Assocication, 137(9), 1304–1312, 2006)
does not define “elective” radiographs, this example is
offered to help differentiate elective from unnecessary.
• Pregnant patient A presents for dental hygiene services
after a one-year time frame. Bitewing radiographs were
last taken three years ago. After the assessment it is
determined that the patient has periodontal disease.
According to the evidence-based selection criteria guidelines (see Table 6-1), this patient should be treatment
planned for a set of vertical bitewing radiographs. These
radiographs have been determined to be necessary to
diagnose and treat this oral condition.
• Pregnant patient B presents for a dental consultation to
replace a removal partial denture with a fixed bridge. To
determine the health of the teeth and the periodontium
that will support the bridge, periapical radiographs are
necessary. However, the dentist would most likely assess
this dental treatment and the need for radiographs as
elective at this time and recommend postponement until
after delivery.
jewelry that they would be uncomfortable removing for the
radiographic procedure?
• Gestures and body language. Does the hand gesture you
use mean the same thing to the patient in his/her culture?
Are there hand gestures that you need to use to convey
instructions regarding the radiographic procedure considered obscene in another culture?
The dental radiographer who presents an accepting, nonjudgmental attitude when presented with diverse cultures is more
likely to gain the trust and cooperation of the patient.
with the patient, project confidence, maintain authority, be
organized, and reassure the patient throughout the procedure.
A hypersensitive gag reflex is probably the most troublesome problem the radiographer encounters. Psychogenic and
tactile stimuli must be diminished or eliminated to reduce
gagging.
The elderly sometimes present with conditions that require
management to produce quality radiographs. Motor disorders and
conditions of involuntary movement may be managed by increasing the amount of radiation (mA) and decreasing the exposure
time (impulses).
A disability is a physical or mental impairment that substantially limits one or more of an individual’s major life activities. The dental radiographer must be prepared to accommodate
patients with disabilities.
Patients who have received radiation therapy should be reassured that necessary dental radiographs are justified if the patient
benefits. The American Dental Association currently recommends that necessary dental radiographs that help the dentist
diagnose and treat oral disease be exposed on pregnant females;
and that elective dental x-rays be postponed for the pregnant
female until after delivery.
The dental radiographer who presents an accepting, nonjudgmental attitude when presented with diverse cultures is more
likely to gain the trust and cooperation of the patient.
RECALL—Study questions
1. List five actions for managing the apprehensive
patient.
a. ______________
b. ______________
c. ______________
d. ______________
e. ______________
2. A hypersensitive gag reflex that results from a physical
reaction to a feeling of the airway being blocked is called
a psychogenic stimulus.
Eliminating psychogenic and tactile stimuli will assist
with managing a hypersensitive gag reflex.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
3. Dental radiographers who demonstrate confidence can
lead to improved patient cooperation.
A patient who is told that gagging is “all in their mind”
will experience fewer gagging problems.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
REVIEW—Chapter summary
The dental radiographer must be competent in altering procedures to meet the needs of individual patients. To help manage
apprehension, the dental radiographer should develop a rapport
348 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
4. Each of the following suggestions help the radiographer
avoid exciting a hypersensitive gag reflex EXCEPT
one. Which one is the EXCEPTION?
a. Ask the patient to breathe through the nose.
b. Ask the patient to rinse the mouth with ice water
prior to placement of the image receptor.
c. Ask the patient if they have ever gagged during x-ray
exposures.
d. Ask the patient to press their head against the headrest during the procedure.
5. Placement of the image receptor in which of these following regions is most likely to initiate a gag reflex?
a. Maxillary premolar
b. Maxillary molar
c. Mandibular premolar
d. Mandibular molar
6. The patient is less likely to gag
a. the longer the image receptor stays in the mouth.
b. if they concentrate on the image receptor placement.
c. when the image receptor is slid into position over the
oral mucosa.
d. while performing a breathing exercise during image
receptor placement.
7. Older adults who present with soft tissue degeneration
that makes placement of the image receptor uncomfortable may benefit from each of the following EXCEPT
one. Which one is the EXCEPTION?
a. Increasing the exposure time
b. Using a smaller-sized image receptor
c. Using a lighter-weight image receptor holder
d. Applying an edge protector to the image receptor
8. To compensate for slight movement that results from
Parkinson’s disease tremors, the radiographer can adjust
the exposure settings to
a. decrease the mA and decrease the impulses.
b. increase the mA and increase the impulses.
c. decrease the mA and increase the impulses.
d. increase the mA and decrease the impulses.
9. When performing radiographic services for the patient
with a disability, the radiographer should
a. remove the patient’s eyewear for them prior to exposures.
b. offer to assist the patient in the manner that they want.
c. communicate with the caregiver instead of talking
directly to the patient.
d. ask personal questions about the patient’s disability.
10. Unnecessary radiographs may be taken on the cancer
patient, but only elective radiographs may be taken on
the pregnant female.
a. The first part of the statement is true, the second part
of the statement is false.
b. The first part of the statement is false, the second
part of the statement is true.
c. Both parts of the statement are true.
d. Both parts of the statement are false.
11. It is ethical practice to take unnecessary radiographs on
a. the older adult.
b. the pregnant female.
c. the cancer patient.
d. no one.
12. The dental radiographer should consider each of the following to develop sensitivity for the culturally diverse
patient EXCEPT one. Which one is the EXCEPTION?
a. Lowered mental capacities
b. Personal space zone
c. Communication style
d. Culturally different meanings to hand gestures
REFLECT—Case study
You have just greeted your patient in the reception area, introduced yourself, and asked her to follow you to the operatory,
where you will be taking a full mouth series of radiographs.
Once seated, you notice that the patient appears apprehensive.
As you get ready to begin the procedure, you engage her in a
conversation to assess why she appears so nervous. The patient
eventually tells you that her last experience taking radiographs
could not be completed because she experienced a gagging
problem. She states that she was so embarrassed by it that she
never went back to that practice.
1. Explain how you would respond to this patient. Include
how you would develop a rapport, project confidence,
and maintain authority.
2. Prepare a conversation with this patient where your
responses reassure her about your ability to perform the
procedure; how the procedure today can be different
than her past experience; and what techniques you have
to help her control the gag reflex.
3. Answer the following questions:
a. Why should you not tell this patient that gagging is
all in her mind?
b. What area of the oral cavity should you try placing
the image receptor first, and why?
c. What is the purpose of thanking and praising the
patient for her cooperation with the procedure?
d. What is the difference between psychogenic and tactile stimuli? Give an example of each.
e. What is the purpose of asking the patient to do
breathing exercises during radiographic exposures?
f. What is the purpose of rinsing with ice water or placing salt on the tongue?
g. If you use any of these tricks and techniques, why is
it best to tell the patient what trick you are planning
to use?
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
CHAPTER 27 • MANAGING PATIENTS WITH SPECIAL NEEDS 349
River, NJ: Pearson Education. Chapter 9, “Patient Management
and student partner practice.”
REFERENCES
American Dental Association. (2004, April 28). Statement on
ante partum dental radiography and infant low birth
weight. JAMA. Retrieved from www.da.org/public/media/
releases/0404_release03.asp
American Dental Association Council on Scientific Affairs.
(2006). The use of dental radiographs: Update and recommendations. Journal of the American Dental Association,
137, 1304–1312.
Darby, M. L., & Walsh, M. M. (2009). Dental hygiene theory
and practice (3rd ed.). St. Louis, MO: Elsevier.
Hujoel, P. P., Bollen, A., Noonan, C. J., & del Aguila, M. A.
(2004). Ante partum dental radiography and infant low birth
weight. JAMA, 291, 16–1993.
Khan, F. M. (2009). The physics of radiation therapy (4th ed.).
Philadelphia: Lippincott Williams & Wilkins.
Langland, O. E., Langlais, R. P., & Preece, J. (2002). Principles
of dental imaging (2nd ed.). Philadelphia: Lippincott
Williams & Wilkins.
White, S. C., & Pharoah, M. J. (2008). Oral radiology:
Principles and interpretation (6th ed.). St. Louis, MO:
Elsevier.
Wilkins, E. M. (2010). Clinical practice of the dental
hygienist (10th ed.). Philadelphia: Lippincott Williams
& Wilkins.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. Demonstrate the ability to adapt standard techniques when necessary.
3. Demonstrate appropriate adaptations in image receptor placement to avoid overlap.
4. Explain the need to alter vertical angulation in the presence of a shallow palatal vault.
5. Demonstrate knowledge of setting the exposure time based on patient characteristics.
6. Demonstrate the ability to place an intraoral image receptor in the presence of large
maxillary or mandibular tori.
7. Discuss the procedures for image receptor placement in patients with edentulous areas.
8. Discuss the procedures for image receptor placement during endodontic procedures.
9. List three methods of localization.
10. Utilize the buccal-object rule to identify the location of a foreign object.
11. Describe the difference between a standard molar periapical radiograph and
a disto-oblique periapical radiograph.
12. List four reasons to duplicate radiographs.
13. Demonstrate the step-by-step procedures for duplicating radiographs.
KEY WORDS
Buccal-object rule
Disto-oblique periapical radiographs
Duplicate radiograph
Duplicating film
Edentulous
Endodontic therapy
Film duplicator
Hemostat
Localization
Root canal treatment
SLOB rule
Tori
Torus mandibularis
Torus palatinus
Tube shift method
Working radiograph
Supplemental
Radiographic Techniques
CHAPTER
28
CHAPTER
OUTLINE
 Objectives 350
 Key Words 350
 Introduction 351
 Acceptable
Variations in
Technique 351
 Anatomical
Variations 353
 Endodontic
Techniques 356
 Methods of
Localization 357
 Disto-oblique
Periapical
Radiographs 357
 Film Duplicating
Procedure 360
 Review, Recall,
Reflect, Relate 361
 References 363
CHAPTER 28 • SUPPLEMENTAL RADIOGRAPHIC TECHNIQUES 351
Conventional molar
image receptor placement
Modified image receptor
placement
FIGURE 28-2 Image receptor position to avoid molar overlap.
The anterior portion of the image receptor is placed a greater distance
away from the lingual surfaces of the teeth.
Introduction
It is important that the dental radiographer possess a working
knowledge of radiographic theory and techniques to produce
diagnostic quality radiographs. However, each patient presents
with unique characteristics, some of which may require that the
dental radiographer have the knowledge and skills to adapt
these ideal procedures to best suit the circumstances. What sets
the skilled radiographer apart from the average is the ability to
alter techniques and still produce diagnostic images.
The purpose of this chapter is to provide specific information on acceptable alterations of the ideal skills you have learned
in this book.
Acceptable Variations in Technique
Anatomical limitations, such as rotation of the teeth, variations in
the height of the palate, the presence of unerupted third molars,
or excessive root lengths, may require that the radiographer
apply acceptable variations in the radiographic technique. Such
changes may occur in the horizontal or vertical angulations or in
placement of the image receptor. Although image receptor holders with external aiming devices assist the radiographer in producing diagnostic radiographs some conditions may affect the
ideal placement of these holders. If the image receptor holder
cannot be placed precisely, the radiographer may be aligning the
x-ray beam to the wrong place. The radiographer who possesses
the skills necessary to evaluate image receptor placement for correctness may still produce a diagnostic quality radiograph by
aligning the angles and points of entry to the image receptor
itself, instead of relying on the external aiming device alone. The
external aiming device on an image receptor holder is an indicator, but does not have to be the absolute “dictator” on where to
line up the x-ray beam (Figure 28-1). The radiographer who can
judge the accuracy of the image receptor placement can compensate when positioning is less than ideal.
Avoiding Overlap
MOLARS Because the interproximal surfaces of the molars
are in a mesiodistal relationship to the patient’s sagittal plane,
conventional image receptor placement parallel to the buccal
surfaces may result in overlapping of the contact areas and closure of the embrasure spaces. To assist with avoiding the occurrence of overlap error, the image receptor should be positioned
perpendicularly to the embrasures. To achieve this position, the
image receptor should be placed slightly diagonal, with the
front edge of the receptor a greater distance from the lingual
surfaces of the teeth than the back edge (Figure 28-2).
CANINE-PREMOLAR The canine periapical and bitewing
radiographs will almost always exhibit overlap between the distal
of the canine and the mesial of the premolar. This overlap
occurs because the curve of the arches in this region superimposes
the lingual cusp of the premolar onto the distal edge of the
canine. To help minimize this overlap, the horizontal angulation
can be adjusted slightly to direct the central rays of the x-ray
beam to intersect the image receptor from the distal. Shifting
the PID slightly toward the posterior will help separate these
two teeth on the resultant image (Figure 28-3).
Because the mesial portion of the premolar will often overlap
the distal portion of the canine on canine periapical and bitewing
radiographs, it is important that the distal portion of the canine
be imaged clearly when exposing premolar periapical and bitewing
radiographs when taking a series of radographs.
Malaligned or Crowded Teeth
When teeth are malaligned or crowded, it may be necessary to
take additional radiographs at various horizontal angles to image
every interproximal area clearly, with no overlap (Figure 28-4).
The image receptor should be positioned perpendicularly to the
embrasures of each tooth as necessary.
Altering Vertical Angulation
Absolute parallelism between the image receptor and the long
axes of the teeth is sometimes difficult to achieve. If the deviation
from parallel does not exceed 15 degrees, the radiograph is generally acceptable (Figure 28-5). When the patient presents with a
shallow palate that prevents the image receptor from being
placed parallel to the teeth, the root apices may not be recorded
on the radiograph. Increasing the vertical angulation by up to 15
degrees over what is indicated will image more of the apical
region (see Figure 26-6 and Figure 28-7). It is important to
FIGURE 28-1 Indicator ring not a dictator. The radiographer
has chosen to increase the vertical angulation to increase the
periapical coverage on the resultant image.
352 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
1st radiograph
2nd radiograph
FIGURE 28-4 Different horizontal angluation is required
when teeth are malaligned.
FIGURE 28-5 Shallow palate. The tissue edge of the image
receptor is shown tipped away from the teeth. When the lack of
parallelism is less than 15 degrees, the resultant radiograph will
generally be acceptable.
A
C
B
FIGURE 28-3 Minimize canine and
premolar overlap. (A) The curve of the
arches in this region superimposes the
lingual cusp of the premolar onto the distal
edge of the canine. (B) Shifting the
horizontal angulation slightly to direct the
x-ray beam to intersect the image receptor
from the distal will help avoid overlap of
these two teeth. (C) Note the elimination of
overlap error in the radiograph on the right.
PID
Plane of the
image receptor
Long axis
of tooth
CHAPTER 28 • SUPPLEMENTAL RADIOGRAPHIC TECHNIQUES 353
FIGURE 28-6 Increased vertical angulation recorded more of
the apical region imaging this supernumerary (extra) impacted
premolar, while cutting off a portion of the occlusal region of the teeth.
PID
Maxillary torus
FIGURE 28-7 Maxillary torus. Image receptor placed on the far
side of the torus away from the teeth.
Mandibular torus
PID
Tongue
FIGURE 28-8 Mandibular torus. Image receptor placed between
the torus and the tongue.
remember that varying the vertical angulation must be slight, no
more than 15 degrees, or noticeable distortion will result.
Exposure Factors
Bone and tissue density vary with the age and physical structure of the patient. In most patients the bone structures are thinner in the mandibular incisor region and denser in the maxillary
molar region, making it desirable to alter the exposure time or
milliamperage to produce radiographs of ideal density. Making
changes in the exposure settings customizes the radiation dose
the patient receives. We learned in Chapter 26 that the exposure
settings for a child patient, whose bone structures are less
dense, should be less than the setting for an adult patient. In
addition, patients who present with edentulous regions would
require less radiation for those areas with missing teeth. Exposure recommendations depend on the characteristics of the
patient and the film speed and the type of x-ray equipment in
use. Because these exposure recommendations vary widely,
recommended settings for all patients and all regions of the oral
cavity should be posted next to the x-ray unit control panel for
easy reference.
Anatomical Variations
The dental radiographer should be familiar with anatomical
variations patients may present with. In addition to a shallow
palate, patients may present with bony outgrowths on the palate
and the lingual surfaces of the mandible, called tori.
Tori
Tori (torus, singular) are commonly seen in the oral cavity. A
maxillary torus, called torus palatinus, is a benign outgrowth
of bone along the midline of the hard palate. A mandibular
torus, called torus mandibularis or lingual torus, is a benign
outgrowth of bone along the lingual aspect of the mandible in
the canine-premolar area.
A large torus palatinus or torus mandibularis may interfere
with placement of the image recpetor. Care should be taken when
placing the image receptor in the presence of tori. In addition to
its intrusion into the oral cavity, the oral mucosa covering the
tori can be thin and sensitive. The edge of the image receptor
should not be placed directly on top of the tori, as this would
result in only a partial image of the roots of the teeth. Instead,
the image receptor should be placed on the far side of the torus
(Figure 28-7). When placing the image receptor in the presence
of mandibular tori, place the image receptor between the torus
and the tongue (Figure 28-8). This recommended placement
may prove difficult when bitewing tab holders are used. Positioning the image receptor away from the teeth requires that the
patient bite on the very end of the bitewing tab. To aid with
proper placement in such cases, the bite tab would need to be
lengthened (see Figure 16-7).
The Edentulous Patient
Preventive radiography is often beneficial to the fully and partially edentulous patient because the normal appearance of the
dental ridges may conceal problems underneath. Radiographs
benefit the edentulous patient for the following reasons:
• To detect the presence of retained roots, impacted teeth,
foreign bodies, cysts, and other pathological lesions.
• To establish the position of the mental foramen before constructing dentures.
• To establish the position of the mandibular canal before
implant surgery.
• To determine the condition and extent of alveolar bone
present.
Periapical radiographs may be taken of edentulous areas
using either the paralleling or the bisecting technique with minor
modifications. Normally, the teeth serve as landmarks to guide
354 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
then directed horizontally and vertically toward the center of the
image receptor perpendicular to the mean tangent of the facial
side of the ridge and to the plane of the image receptor.
If parallel placement of the image receptor remains difficult
in an edentulous area, it is better to try using the bisecting technique than to risk taking a poor-quality radiograph that would
need to be retaken. When using the bisecting technique, the
image receptor is placed against the lingual surface of the edentulous ridge. The vertical angulation is determined by bisecting
the angle formed between the recording plane of the image
receptor and an imaginary line through the ridge that substitutes for the long axes of the teeth (Figure 28-11). This position
often results in some dimensional distortion. However, acceptable radiographs can still be produced.
Because the edentulous region is less dense, the amount of
radiation needed to produce an acceptable radiographic image
A
B
Image
receptor
Polystyrene
block
Polystyrene
block
Holder
Holder
Holder
Holder
Image
receptor
Image
receptor
Image
receptor
Cotton
roll
Cotton roll
Cotton roll
Cotton
roll
FIGURE 28-9 Partially edentulous mouth. Cotton rolls or polystyrene blocks can be used to substitute
for missing teeth to help hold the image receptor holder in place. (A) Edentulous mandibular anterior region.
(B) Edentulous maxillary posterior region.
placement of the image receptor. Because these landmarks are
not present in the edentulous patient, one must estimate the best
positions. Additionally, visualizing and establishing horizontal
and vertical planes is more difficult, particularly when the
bisecting technique is used. However, in the totally edentulous
patient a fair amount of leeway in horizontal angulation is permissible because the absence of teeth eliminates the problem of
overlapping tooth images. The focus of interest is no longer the
teeth but the bone structure of the edentulous ridge.
Because it produces the best diagnostic images, the paralleling technique should be the radiographer’s first choice. Radiographic detail is improved and dimensional distortion is
minimized when the image receptor holder can be properly supported with cotton rolls or polystyrene blocks to position the
image receptor parallel to the long axis of the edentulous ridge
(Figures 28-9 and 28-10). The central rays of the x-ray beam are
CHAPTER 28 • SUPPLEMENTAL RADIOGRAPHIC TECHNIQUES 355
A
Image receptor
Holder
Polystyrene
block
Cotton roll
B
Image
receptor
Holder
Polystyrene
block
Cotton roll
FIGURE 28-10 Totally edentulous mouth. When all teeth are missing, cotton rolls,
polystyrene blocks, or a combination of both can be used as substitutes for the crowns of the
teeth. These will allow the patient to bite and stabilize the image receptor holder. The
thickness of the cotton rolls or blocks will determine the amount of edentulous ridge recorded.
(A) Maxillary anterior region. (B) Mandibular posterior region.
A
B
Bisector
Bisector
Long axis of
maxillary ridge
Long axis of
mandibular ridge
Vertical direction
of central beam
Vertical direction
of central beam
Tongue
Image receptor
Image receptor
FIGURE 28-11 Illustration of the bisecting technique for an edentulous patient. The
central ray is directed perpendicular to the bisector, an imaginary line estimated to be halfway
between the plane of the image receptor and a line drawn vertically through the ridge to substitute
for the long axes of the teeth. (A) Maxillary edentulous ridge, (B) Mandibular edentulous ridge.
356 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
FIGURE 28-12 Endodontic film holder. (Courtesy of
Dentsply Rinn.)
FIGURE 28-13 Modifying a film holder for use in
endodontic therapy. Removing a portion of this disposable
polystyrene image receptor holder will allow the endodontic
materials placed in the tooth to remain in place during the exposure.
FIGURE 28-14 Rinn Snap-A-Ray image receptor holder.
FIGURE 28-15 Hemostat as a film holder for endodontic
procedures eliminates the need to occlude on on a biteblock.
is less. Exposure settings for edentulous regions should be reduced
by about one-fifth less than the exposure required for an area
where teeth are present.
Endodontic Techniques
Endodontic therapy involves the treatment of the tooth by
removing the nerves and tissues of the pulp cavity and replacing
them with filling material. Successful endodontic therapy or
root canal treatment depends on the use of radiographs. A
series of radiographs on the same tooth is needed to evaluate
various stages of endodontic treatment. The initial radiograph
is exposed to determine the preoperative condition and to
make a diagnosis. Additional radiographs are made as the
work progresses to determine the length of the root; the position
of a reamer, broach, or file in the canal; or the position of the
sealer and point or points (the tooth may have several canals).
And finally, a posttreatment radiograph is needed to make
sure that the canal or canals are closed satisfactorily.
Once again, the paralleling technique is the technique of
choice. Standard periapical radiographic procedures can be
applied in endodontic radiographic exposures; however, there
are some differences. The materials used in endodontic treatment—such as a rubber dam, reamers, broaches, files, or silver
or gutta-percha points—often hinder placement of the image
receptor. The presence of these materials, which must be left in
place during radiographic exposures, makes it impossible for
the patient to bite down on the biteblock of an image receptor
holder to hold it in place. Avoiding distortion and magnification
of the image is a major concern in endodontic treatment
because the length of each canal must be accurately measured.
Therefore the paralleling technique, which consistently produces the least distortion, should be used whenever possible.
Although preoperative and postoperative radiographs are made
in the usual manner, some technique modifications are required
for the working radiographs that are exposed with the rubber
dam and instruments in place.
The ideal image receptor holder is one specifically designed
for exposure of working radiographs (Figure 28-12). Other types
of holders may be modified to accommodate retention of the
image receptor during endodontic therapy (Figure 28-13). However, it may become necessary to use methods of image receptor retention that rely on visual alignment of the PID. Image
receptor holders such as the Rinn Snap-A-Ray (Figure 28-14)
or the employment of a dental instrumental called a hemostat
(Figure 28-15) or a tongue depressor as a custom-made holder
will allow the patient to help stabilize the image receptor in the
correct position (Figure 28-16).
When imaging multirooted teeth, such as the maxillary premolars and molars, the buccal and lingual root canals will often
CHAPTER 28 • SUPPLEMENTAL RADIOGRAPHIC TECHNIQUES 357
Hemostat
Image receptor
Long axis of the tooth
Endodontic files
PID
FIGURE 28-16 Hemostat facilitates holding the image
receptor in a parallel position to the long axis of the tooth.
appear superimposed. The ability to separate the buccal and lingual
roots on the image increases the radiograph’s value during
endodontic procedures. The radiographer can accomplish this
through the use of tube head shifting called localization.
Methods of Localization
Radiographs are a two-dimensional picture of three-dimensional objects. To get that third dimension from a radiographic image, the dental radiographer should be skilled in
reading the images. Localization methods help the radiographer determine whether a structure such as a root canal or a
foreign object embedded within the maxilla or mandible is in
front of (facial or buccal) or behind (lingual) the teeth. There
are three methods of localization.
Definitive Evaluation Method
The definitive method of localization is based on the shadow
casting principles explained in Chapter 4. The principle that an
object positioned farther away from the image receptor will be
magnified and less clearly imaged is applied with the definitive
method. Because intraoral image receptor placement positions
the receptor close to the lingual surface of the teeth, those objects
on the lingual are more likely to appear distinctly defined on the
resultant radiograph. Those objects positioned more toward the
buccal or facial surface will be farther away from the image
receptor and therefore are more likely to appear magnified and
less clearly imaged on the resultant radiograph (Figure 28-17).
Although true in principle, the definitive method of localization
is not consistantly reliable.
Right-angle Method
Once identified on a periapical radiograph, a better way to determine whether or not a foreign object or structure, such as an
impacted tooth, is located on the buccal or the lingual is to take
an occlusal radiograph. A cross-sectional occlusal radiograph,
described in Chapter 17, places the image receptor at a right
angle to the tooth. In this position the occlusal radiograph will
image the object clearly on the buccal or lingual (Figure 28-18).
Tube Shift Method (Buccal-object Rule)
The tube shift method, also called the buccal-object rule, is the
most versatile method of localization. To apply the tube shift
method, two radiographs are needed. The two radiographs must
have been exposed using either a different horizontal or a different
vertical angulation. If a full mouth series of periapicals or a
complete set of bitewing radiographs, or a combination of both,
are available and the object in question is imaged in more than
one radiograph, it is possible to apply the tube shift method
when reading the radiographs to determine the buccal or lingual
location of the object.
The principle behind the tube shift method is that if the
structure or object in question appears to have moved in the
same direction as the horizontal (Figure 28-19) or vertical
(Figure 28-20) shift of the tube, then the structure or object is
located on the lingual. Conversely, if the move is in the opposite direction of the shift of the tube, the structure or object is
located on the buccal or facial. The tube shift method is
summarized as the SLOB Rule, which stands for same on
lingual–opposite on buccal.
Disto-oblique Periapical Radiographs
Shifting the tube (the PID and tube head) has another useful application. Disto-oblique periapical radiographs utilize a tube shift
to help image posterior objects such as impacted third molars,
especially when the patient cannot tolerate posterior image receptor placement. Standard vertical and horizontal angulation utilized when exposing periapicals may be altered slightly (no more
than 15 degrees) to project posterior objects forward or anteriorly
onto the image receptor (Procedure Box 28-1).
FIGURE 28-17 Definitive method of localization. Note the
barely visible supernumerary (extra) root on this first molar.
Applying the definitive method of localization, it is most likely a
buccal root. The buccal position would place this root a greater
distance away from the image receptor, resulting in its magnified and
less distinctly defined appearance.
358
A
B
C
PID
PID
PID
FIGURE 28-19 Horizontal tube shift. (A) In the original
radiograph, buccal and lingual objects are superimposed. (B) When
the tube head is moved distally, the buccal object appears to move
mesially, whereas the lingual object appears to move distally. (C)
When the tube head is moved mesially, the buccal object appears to
move distally, whereas the lingual object appears to move mesially.
A
B
C
PID
PID
PID
FIGURE 28-20 Vertical tube shift. (A) In the original
radiograph, buccal and lingual objects are superimposed. (B) When
the tube head is moved superiorly, the buccal object appears to move
inferiorally, whereas the lingual object appears to move superiorly.
(C) When the tube head is moved inferiorly, the buccal object appears
to move superiorly, whereas the lingual object appears to have moved
inferiorally.
A B
FIGURE 28-18 Right angle method of localization. (A) A foreign object appears in the periodontal pocket between the
second premolar and the first molar. It is impossible to tell from this periapical radiograph whether the object is located toward
the buccal or the lingual. (B) The occlusal radiograph, placed at a right angle position to the tooth, clearly images the object on
the buccal side of the pocket.
CHAPTER 28 • SUPPLEMENTAL RADIOGRAPHIC TECHNIQUES 359
PROCEDURE 28-1
Disto-oblique periapical radiographs
1. Perform infection control procedures (see Procedure 10-2).
2. Prepare unit, patient, and supplies needed according to the procedure for exposing periapical radiographs (see Procedure 13-1).
3. Place the image receptor into the holding device. (If using film, place such that the embossed dot will be
positioned toward the occlusal/incisal edge–dot in the slot).
Maxillary Disto-oblique Periapical Radiographs
1. Position the image receptor and align the horizontal and vertical angulations for a standard maxillary
molar periapical radiograph.
2. From this standard alignment, shift the tubehead and PID to direct the central rays of the x-ray beam to
intersect the image receptor obliquely from the distal by 10 degrees.
3. Increase the vertical angulation by 5 degrees.
4. Check that the image receptor is centered in the middle of the x-ray beam.
5. Increase the recommended exposure setting for the standard periapical radiograph to the next higher
impulse or timer setting.
Mandibular Periapical Radiograph
1. Position the image receptor and align the horizontal and vertical angulations for a standard mandibular
molar periapical radiograph.
2. From this standard alignment shift the tube to direct the central rays of the x-ray beam to intersect the
image receptor obliquely from the distal by 10 degrees.
3. Check that the image receptor is centered in the middle of the x-ray beam.
4. No change is made to the standard vertical angulation.
5. No change is made to the standard recommended exposure setting.
FIGURE 28-21 Disto-oblique periapical technique. The
horizontal angulation is shifted 10 degrees from the distal, and the
vertical angulation is increased 5 degrees.
For example, if an impacted third molar is positioned so far
posterior in the oral cavity that the standard image receptor
placement is not likely to record it, the PID and tube head can
be moved to project the impacted tooth forward onto the image
receptor (Figure 28-21). By directing the x-ray beam mesially,
the posterior object will be projected anteriorly. Because the
central rays will intersect the plane of the image receptor at an
oblique angle, there will be slight overlap and distortion of the
image (Figure 28-22). However, the focus of disto-oblique
periapical radiographs is on recording an object or structure
that may not be in standard periapical radiographs, so this distortion is tolerated.
The maxillary disto-oblique periapical radiograph requires
three changes to the standard maxillary molar periapical
radiograph. The first and most important step is to shift the
horizontal angulation so that the posterior object will be projected forward. Second is to increase the vertical angulation.
360 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
Most impactions, or foreign objects in the posterior region of
the maxilla, will be located farther superior than the erupted
teeth. As discussed at the beginning of this chapter, increasing
the vertical angulation will increase the periapical coverage
of the image. And finally, the exposure setting for a maxillary
disto-oblique radiograph must be increased to the next higher
timer setting. The oblique angle of the x-ray beam will
require a longer passage through the patient’s tissues. The
increased vertical angulation will most likely direct the x-ray
beam through the zygomatic arch. These two changes, in the
horizontal and the vertical angulations, necessitate more
radiation to produce adequate radiographic image density.
The mandibular disto-oblique periapical radiograph
requires only the change to the horizontal angulation, to project the impaction or object forward. Most impactions of the
posterior mandible will be located at the level of, or higher
than, the erupted teeth so no change is required in the vertical
angulation. There are no thick bony structures, like the
zygoma, to penetrate, so the exposure time does not have to be
increased.
Film Duplicating Procedure
Original radiographs should remain a part of the patient’s permanent record, so there are times when a duplicate radiograph
is needed. These include copies for third-party payment (insurance companies), when referring the patient to a specialist,
when the patient changes dentists or moves, for consultations
with other professionals, for publications in professional journals or for use in professional study clubs, to accompany biopsies of pathological conditions, and for evidence in legal cases.
A duplicate radiograph is an identical copy of the original
radiograph and may be obtained through the use of two-film
intraoral film packets. If a double film packet is not available
or the film is an extraoral film, the use of a film duplicator will
produce a copy of the original radiograph. Radiographs can be
duplicated as often as necessary without additional patient
exposure.
Equipment
Duplicating radiographs requires duplicating film and a
duplicator.
DUPLICATING FILM Duplicating film is available in sheet
form in a variety of sizes. The film is emulsion-coated on one
side only. Under a safelight, the emulsion side looks dull or
lighter, whereas the side without the emulsion coating looks
shiny or darker (see Chapter 7). It is possible to duplicate either
a single radiograph or a full mouth series at a single printing.
FILM DUPLICATOR A film duplicator is a device that provides a diffused light source (usually ultraviolet) that evenly
exposes the duplicating film. There are different size film
duplicator models available commercially (Figure 28-23).
Large duplicators accommodate all film sizes, whereas
small duplicators may be used only for #2 film and smaller
(Figure 28-24).
PROCEDURES FOR FILM DUPLICATION Flm duplicators come
with manufacturer’s instructions for use. All duplication must be
done in the darkroom under a safelight (Procedure Box 28-2).
FIGURE 28-23 Radiograph duplicating machines. Contain a
built-in ultraviolet fluorescent light source and a timer to permit
variations in density. These x-ray film duplicators accommodate
duplication of multiple films at a time, with room for a full mouth
series, or a panoramic radiograph. (Courtesy of Densply Rinn.)
FIGURE 28-24 Small radiograph duplicator accommodates
film sizes #0, #1, and #2.
FIGURE 28-22 Comparision of standard and disto-oblique
periapical radiographs. (A) Standard periapical radiograph images
a portion of the impacted third molar. (B) Disto-oblique periapical
radiograph images more of the impacted third molar. Note that
shifting the tube horizontally causes overlap error, and shifting the
tube head vertically causes the crowns to be cut off the the image.
PROCEDURE 28-2
Film duplication
CHAPTER 28 • SUPPLEMENTAL RADIOGRAPHIC TECHNIQUES 361
1. Select radiographs for duplication (referrals, third-party payment, consultations).
2. Prepare duplicator. Raise cover and wipe glass surface with glass cleaner if necessary.
3. Place duplicator mode switch in the VIEW position to turn on the view box as necessary to arrange original
radiographs into position for duplicating.
4. Remove the original radiographs from the film mounts prior to duplication. (Leaving the original radiographs
in the film mount will prevent close contact between the originals and the duplicating film, resulting in the
fuzzy appearance of the duplicate radiograph.)
5. Place original radiographs on the duplicator glass surface with the embossed dots concave (dimple). Placing the “down dot” on the duplicator surface will allow for close contact between the original radiographs
and the duplicating films.
6. Place the radiographs near the L or R on the duplicator glass surface to identify the left or right sides
respectively on the duplicate images.
7. Turn the duplicator mode switch to the DUPLICATE position to turn off the view box light. Be sure to turn
off this view box light prior to opening the box of duplicating film.
8. Set the timer to the desired exposure time. See the manufacturer’s recommendations. If a darker duplicate
is desired, decrease the exposure time; if a lighter duplicate is desired, increase the exposure time. (Increasing and decreasing the exposure time from the duplicator light has the opposite effect on the resulting
image than increasing and decreasing the x-ray exposure.)
9. Obtain a box of duplicating film.
10. Under safelight conditions, remove a sheet of duplicating film from the box. When duplicating individual
films, use scissors to cut duplicating film to the approximate size needed.
11. Place the duplicating film emulsion (light) side down on top of the originals.
12. Close the duplicator cover and secure the latch tightly. (Failure to secure the latch will result in a loss of contact between the originals and the duplicating film, resulting in the fuzzy appearance of the duplicate image.)
13. Depress the exposure button to activate exposure.
14. When the indicator light goes off at the end of exposure cycle, unlatch and raise the cover, remove the
duplicating film, and process the duplicating film either automatically or manually.
15. Remount the original radiographs and return to the patient’s permanent record.
16. Clean the darkroom and replace materials.
17. When the duplicate film exits the processor, label it with the patient’s name, date, and any other information necessary. Ensure that the right and left sides of the image are identified appropriately.
REVIEW—Chapter summary
Anatomical conditions such as malaligned or crowded teeth, a
shallow palatal vault, the presence of tori, and endentulous
regions may require alterations in radiographic technique. A
skilled radiographer can apply acceptable variations in aligning
the horizontal and vertical angulations and still produce diagnostic quality radiographs. The radiographer should possess the
skills necessary to evaluate image receptor placement for correctness, align horizontal and vertical angluations, and determine points of entry when using an image receptor holder with
and without an external aiming device.
Exposure times should be adjusted based on the patient’s
characteristics and the area of the oral cavity to be imaged.
Edentulous regions require one-fifth the dose of radiation
required in regions with teeth present. The paralleling technique is preferred, however, periapical radiographs may be
exposed in edentulous regions using the paralleling or the
bisecting technique. Cotton rolls and/or polystyrene blocks
may be used to help stabilize the image receptor to a position
parallel to the edentulous ridge.
362 PATIENT MANAGEMENT AND SUPPLEMENTAL TECHNIQUES
Image receptor holders are available commercially or may
be altered by the radiographer to produce working radiographs
during endodontic therapy.
Localization methods add a third dimension to two-dimensional radiographs. Definitive method is the least reliable
method of localization. The right angle method of localization
uses a periapical radiograph and a cross-sectional occlusal
radiograph. With the tube shift method of localization, the
object in question is located on the lingual if it moves in the
same direction as the horizontal or vertical shift of the tube
and on the buccal if it moves in the opposite direction as the
horizontal or vertical shift of the tube. The tube shift method,
or buccal object rule, is summarized as the SLOB (same on
lingual–opposite on buccal) rule.
Disto-oblique periapical radiographs are useful when the
patient cannot tolerate posterior placement of the image receptor. Disto-oblique periapical radiographs allow the radiographer to shift the PID and tube head to project posterior objects
and structures anteriorly onto the image receptor.
Copies of radiographs are used to send to insurance companies or to another oral health care practice; for use in referrals, consultations with other professionals, or publication in
professional journals; or when needed in litigation. Duplicate
radiographs are made using a commercially made duplicator
and special duplicating film.
RECALL—Study questions
1. To help avoid molar overlap, the radiographer should
place the image receptor
a. parallel to the buccal surfaces of the molars.
b. perpendicular to the buccal surfaces of the molars.
c. parallel to the molar embrasures.
d. perpendicular to the molar embrasures.
2. To minimize canine-premolar overlap, the radiographer
should direct the x-ray beam toward the image receptor
slightly obliquely from the
a. mesial.
b. distal.
c. occlusal.
d. apical.
3. To compensate for a shallow palatal vault, the vertical
angulation may be adjusted to
a. increase by up to15 degrees.
b. decrease by up to 15 degrees.
c. increase by up to 25 degrees.
d. decrease by up to 25 degrees.
4. Which area of the oral cavity would require the highest
exposure setting?
a. Maxillary anterior region
b. Maxillary posterior region
c. Mandibular anterior region
d. Mandibular posterior region
5. The presence of a large mandibular torus may make
which of these difficult?
a. Aligning the correct horizontal angulation
b. Determining the accurate vertical angulation
c. Placing the image receptor precisely
d. Directing the central ray of the x-ray beam at the
center of the image receptor
6. The best image receptor placement for a patient with a
torus palatinus is
a. between the torus and the tongue.
b. on the top of the torus.
c. near the front of the torus.
d. behind the torus.
7. The paralleling technique is the best technique for
imaging edentulous areas.
The bisecting technique is the best technique when
imaging endodontic treatment.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
8. Which of the following radiographs would be the least
beneficial for the totally edentulous patient?
a. Bitewing
b. Periapical
c. Panoramic
d. Occlusal
9. The exposure setting for edentulous regions should be
decreased from the exposure time for the same region
with teeth by
a. one-half.
b. one-third.
c. one-fourth.
d. one-fifth.
10. Which of the following would be the BEST image
receptor holder for exposing working radiographs during a root canal procedure?
a. Rinn XCP
b. Rinn Snap-A-Ray
c. Commercially made endodontic holder
d. Polystyrene block
11. Localization adds which of the following dimensions to
two-dimensional radiographs?
a. Anterior-posterior
b. Buccal-lingual
c. Mesial-distal
d. Inferior-superior
12. Which of the following methods of localization utilizes
a cross-sectional occlusal radiograph?
a. Definitive method
b. Right-angle method
c. Tube shift method
d. Buccal-object rule
R
R
CHAPTER 28 • SUPPLEMENTAL RADIOGRAPHIC TECHNIQUES 363
13. If the tube shifts to the mesial and the object in question
shifts to the distal, the object is located on the lingual.
This is an example of the definitive method of localization.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
14. When exposing a disto-oblique periapical radiograph of
the maxilla, which of the following changes should be
made to the standard periapical radiograph?
a. 5-degree shift in the vertical angulation
b. 10-degree shift in the horizontal angulation
c. An increase in the time/implulse setting
d. All of the above
15. To project an impacted mandibular third molar anteriorly onto the image receptor, a mandibular disto-oblique
periapical radiograph requires a
a. 5-degree shift in the vertical angulation.
b. 10-degree shift in the horizontal angulation.
c. An increase in the time/implulse setting.
d. All of the above.
16. List four reasons to duplicate radiographs.
a. ______________
b. ______________
c. ______________
d. ______________
REFLECT—Case study
A patient has presented at your practice today for a consult
regarding extensive dental work. This patient has several areas
of missing teeth and has expressed an interest in dentures. The
dentist has prescribed a full mouth series of radiographs, and
you are preparing to take the exposures. After performing a cursory exam of the patient’s oral cavity, you note the following:
Several missing and/or broken down teeth
Malaligned and crowded teeth
Partially erupted third molars
Large torus palatinus and bilateral torus mandibularis
A shallow palatal vault
Consider the following and write out your answers:
1. Describe the alterations in technique you will apply to
obtain radiographs in the edentulous areas.
2. Describe the alterations in technique you will apply to
avoid overlap error in the areas of malaligned and
crowded teeth.
3. Identify and describe the technique you will use to best
image the partially erupted third molars.
4. Describe the problems you anticipate facing with the
presence of large tori and a shallow palatal vault.
5. Identify alterations in techniques that will help you
overcome these obstacles.
6. If broken root tips or other foreign objects are identified
on the radiographs, describe how the interpretation of
these can reveal whether or not the objects in question
are located on the buccal or the lingual.
7. Describe other methods of localization that can aid in
making this determination.
8. Identify reasons why this patient’s radiographs may
need to be duplicated.
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson Education. Chapter 11, “Supplemental
Radiographic Techniques and Tips”
REFERENCES
Del Rio, C. E., Canales, M. L., & Preece, J. W. (1982).
Radiographic technique for endodontics. San Antonio:
University of Texas Health Science Center.
Rinn Corporation. (1983). Intraoral radiography with Rinn
XCP/BAS instruments. Elgin, IL: Dentsply/Rinn
Corporation.
Thomson, E. M. (2010). Exercises in oral radiography techniques: A laboratory manual (3rd ed.). Upper Saddle
River, NJ: Pearson Education.
OBJECTIVES
Following successful completion of this chapter you should be able to:
1. Define the key words.
2. Describe the purpose and use of extraoral radiographs.
3. List seven extraoral radiographs that contribute to the treatment of dental patients.
4. Explain the need for proper extraoral film handling.
5. Explain the role intensifying screens play in producing a radiographic image.
6. Match blue- and green-light sensitive film with the appropriate intensifying screen.
7. Explain the role of the extraoral film cassette.
8. Describe how extraoral radiographs are labeled.
9. Explain the need for proper care and cleaning of cassettes and intensifying screens.
10. Explain the role grids play in extraoral radiography.
11. Explain tomography and describe its role in oral health care.
12. Explain cone beam computed tomography and describe its role in oral health care.
KEY WORDS
Ankylosis
Artifacts
Calcium tungstate
Cassette
Cephalostat
Computed tomography (CT)
Cone beam computed tomography (CBCT)
Cone beam volumetric imaging (CBVI)
Grid
Intensifying screens
Lateral cephalometric radiograph
(lateral skull)
Lateral jaw radiograph (mandibular
oblique lateral)
Maxillofacial
Occult disease
Panoramic radiograph
Phosphors
Pixel (picture element)
Posteroanterior (PA) cephalometric
radiograph
Rare-earth phosphors
Reverse Towne radiograph
Screen film
Extraoral Radiography
and Alternate Imaging
Modalities
PART IX • EXTRAORAL TECHNIQUES
CHAPTER
29
CHAPTER
OUTLINE
 Objectives 364
 Key Words 364
 Introduction 365
 Purpose and Use
of Extraoral
Imaging
Modalities 365
 Extraoral
Radiographs
Useful in Oral
Health Care 365
 Extraoral Image
Receptors 366
 Grids 371
 Exposure Factors 371
 Tomography,
Computed
Tomography,
Cone Beam
Computed
Tomography 372
 Review, Recall,
Reflect, Relate 374
 References 376
KEY WORDS
CHAPTER 29 • EXTRAORAL RADIOGRAPHY AND ALTERNATE IMAGING MODALITIES 365
Submentovertex radiograph
Temporomandibular disorder (TMD)
Temporomandibular joint (TMJ)
Tomograph
Tomography
Transcranial radiograph (TMJ)
Voxel (volume element)
Waters radiograph
Introduction
Extraoral radiographs and alternate imaging modalities such as
computed tomography record large areas of the dental arches,
supporting facial structures, and skull using image receptors
that are positioned outside the mouth. Most of these extraoral
imaging techniques require special equipment not readily
available in the general practice dental office (Figure 29-1).
Even though dental assistants and hygienists may not routinely
perform these services, a base knowledge in types of extraoral
radiographs and alternate imaging modalities; an understanding
of what conditions will most likely benefit from which type of
examination; and the ability to recognize the different images
are valuable skills. Patients may need to be referred to an oral
surgeon or to a medical imaging center for examination of a
condition affecting the maxillofacial region. The dental assistant
and dental hygienist may be called on to educate the patient
regarding the procedure or may need to assist with scheduling
the patient’s appointment for the referral. Oral radiographers
should be able to communicate professionally with other health
care professionals.
The purpose of this chapter is to provide an overview of the
types of extraoral radiographs that contribute to the treatment of
dental patients and identify the equipment and image receptors
required and to introduce cutting-edge alternate imaging modalities
that have developed from digital and computer technological
advances.
Figure 29-1 A combination panoramic and cephalometric
dental x-ray unit. (Courtesy of Planmeca.)
Purpose and Use of Extraoral Imaging
Modalities
The purpose of extraoral imaging modalities is to examine structures of the oral cavity and the maxillofacial region that includes
the maxilla and mandible, the facial bones and sinuses, and the
temporomandibular joint. Extraoral radiographs are used to
• Examine large areas of the dental arches and skull
• Study growth and development of bone and teeth
• Detect fractures and evaluate trauma
• Detect pathological lesions and diseases of the jaws
• Detect and evaluate impacted teeth
• Evaluate temporomandibular disorder (TMD)
• Plan treatment for dental implants and prosthetic appliances
Extraoral radiographs may also be substituted for intraoral
radiographs when patients cannot or will not open the mouth.
Handicapped patients or patients with trismus or TMD may not
be able to tolerate the placement of intraoral image receptor.
Extraoral radiographs can be used alone or in conjunction with
intraoral radiographs. For example, it is common to expose both
a panoramic radiograph (see Chapter 30) and intraoral bitewing
radiographs on the same patient.
The general practitioner is most likely to limit the use of
extraoral radiographs to panoramic imaging, discussed in detail in
Chapter 30. The practitioner who specializes in dental implants
will increasingly rely on cone beam computed tomography,
introduced later in this chapter. Othodontists, prosthodontists,
and oral surgeons are more frequent users of extraoral imaging
modalities for diagnosing and treating conditions of the oral cavity
and head and facial regions.
• Orthodontists use facial profile radiographs, produced with
cephalostat headplates (“cephalometric,” meaning measuring
the head) to record, measure, and compare changes in growth
and development of the bones and the teeth.
• Prosthodontists use facial profile radiographs to record the
contour of the lips and face and the relationship of the teeth
before removal to help in constructing prosthetic appliances
that look natural (Figure 29-2).
• Oral surgeons use extraoral radiographs extensively to evaluate trauma, to determine the location and extent of fractures;
to locate impacted teeth, abnormalities, and malignancies;
and to evaluate injuries to the temporomandibular joint.
Extraoral Radiographs Useful in Oral
Health Care
There are many techniques for exposing radiographs of the oral
cavity and the maxillofacial region. It is not within the scope of
this book to describe every available technique. The seven
366 EXTRAORAL TECHNIQUES
projections presented in Table 29-1 are the most common extraoral radiographs in which the x-ray source and the image receptor
remain still and in position during exposure. The panoramic
radiograph, which requires movement of the x-ray source and
the image receptor during exposure, is discussed in Chapter 30.
Extraoral Image Receptors
Traditional Film
To produce a diagnostic quality radiograph while maintaining a
low radiation dose for the patient, extraoral screen film (see
Chapter 7) must be used in conjunction with a pair of intensifying
screens housed within a light-tight cassette. Because they are
extremely light sensitive and not packaged in a protective sealed
wrapper like intraoral films, extraoral films must be carefully
loaded into a cassette under darkroom safelight illumination
(Figure 29-3 and Procedure Box 29-1).
Extraoral films are generally packaged 25, 50, or 100 to a
box, so care should be taken to ensure that overhead white light
is turned off when removing the box cover. Darkroom safelight
filter color and bulb wattage must be appropriate for use with
extraoral film (see Chapter 8). Because extraoral film is more
sensitive than intraoral film, filters that are safe for intraoral film
handling may not be safe for extraoral film handling. The type of
safelight required for extraoral film can usually be found written
on the film package or by checking with the manufacturer.
Extraoral films should be removed from the box with clean,
dry hands. Latex or vinyl treatment gloves should be avoided.
Treatment gloves and plastic overgloves increase the risk of generating static electricity. A static charge results in a white light spark
that will expose the film, leaving radiolucent artifacts (black lines
or smudges) on the resultant image (Figure 29-6). Glove powder
residue on films will also cause radiolucent artifacts.
Handle films by the edges only. Remove each sheet of film
from the box slowly to avoid generating static electricity that
will create artifacts on the films inside the box as well as the
FIGURE 29-3 Loading film into a flexible cassette under
safelight conditions.
FIGURE 29-2 Cephalometric
radiograph produced with a filter
placed between the tube and patient to
remove some of the x-rays to record
outlines of the soft tissue profile.
TABLE 29-1 Extraoral Radiographs of the Maxillofacial Region
TYPE OF
RADIOGRAPH AREA OF INTEREST PURPOSE POSITIONING
Lateral jaw
(mandibular oblique
lateral)
Body or ramus of
mandible; coronoid
process; condyle
To examine posterior region of the
mandible, third molars, especially
when panoramic machine not
available; when children or
patients who have fractures or
swelling are unable to tolerate
placement or hold intraoral image
receptor in place
Lateral
cephalometric (lateral skull)
Entire skull from the
side (lateral); sinus
cavities
Prior to orthodontic intervention, at
various stages of treatment, on completion of treatment; to evaluate
growth/development, trauma,
pathology, developmental abnormalities; can reveal facial soft tissue
profile when a filter is placed
between the tube and patient to
remove some of the x-rays; to establish pre-/posttreatment records
Posteroanteri
or (PA)
cephalometric
(posterior
skull)
Entire skull in the posteroanterior plane;
orbit; frontal sinus
To examine facial growth/development, disease, trauma, developmental abnormalities. Used to
supplement lateral survey because
the right and left sides of the facial
structures are not superimposed on
each other
Waters Middle third of the
face to include
zygoma, coronoid
process, sinuses
To evaluate maxillary, frontal, ethmoid
sinuses
CHAPTER 29 • EXTRAORAL RADIOGRAPHY AND ALTERNATE IMAGING MODALITIES 367
Central
ray
X-ray
beam
Image receptor
Central
ray
X-ray
beam
Image receptor
Image
receptor
Tip of nose from image receptor 3
4
”
Central
ray
X-ray
beam
Sagittal plane
Central ray
Image
receptor
(Continued)
368 EXTRAORAL TECHNIQUES
one being removed. Try to place the film into the cassette without sliding it across the intensifying screens, again to prevent a
static discharge. Film should be loaded into the cassette just
prior to use. Storing film inside cassettes may increase the likelihood of generating artifacts. Only one film should be loaded
into the cassette at a time unless special film made for exposing
two films at once is used.
Intensifying Screens
Intensifying screens transfer x-ray energy into visible light.
This visible light, in turn, exposes the film. The image produced
on an extraoral film results from exposure to this fluorescent
light instead of directly from the x-rays. As the name implies,
intensifying screens “intensify” the effect of x-rays on film. The
use of intensifying screens allows the amount of radiation
required to expose the film to be reduced and therefore reduces
the amount of radiation the patient is exposed to.
Intensifying screens work in pairs. An intensifying screen is
a smooth cardboard or plastic sheet coated with minute fluorescent
crystals mixed into a suitable binding medium. Intensifying
screens are based on the principle that crystals of certain salts—
calcium tungstate, barium strontium sulfate, or rare-earth
phosphors [lanthanum (La) and gadolinium (Gd)]—will
fluoresce and emit energy in the form of blue or green light when
they absorb x-rays. Each of these fluorescent crystals, also called
phosphors, gives off blue or green light that varies in intensity
TABLE 29-1 (Continued)
TYPE OF
RADIOGRAPH AREA OF INTEREST PURPOSE POSITIONING
Reverse Towne Condyles To examine fractures of the condylar
neck
Submentovertex
Base of the skull;
condyles; sphenoid
sinus; zygoma
To evaluate the position/orientation of
the condyles; fractures of the zygomatic arch
Transcranial Head of condyle; glenoid fossa; temporal
bone; temporomandibular joint in
open, closed and at
rest positions
Aids in diagnosing ankylosis (a stiffening of the temporomandibular
joint); malignancies, fractures, and
tissue changes caused by arthritis
[[C ch29unfig07]][[E ch29unfig07]] Mouth open,
head tipped down
Image
receptor
Central
ray
X-ray
beam
Floor
Frankfort line
Image
receptor
X-ray
beam
Central
ray
Image receptor
Central ray
25°
Sagittal plane
1. Obtain the cassette and box of film. Ensure that the film sensitivity matches the intensifying screens used.
2. Open the cassette and inspect to ensure that the hinge and snaps are working. Examine the intensifying screens
for debris or scratches. Clean with solution recommended by the manufacturer if necessary.
3. Turn off overhead white light and turn on safelight.
4. Open the package containing the film and slowly pull out one film.
5. Handle the film by the edges only with clean, dry hands. Place film inside cassette (rigid) (Figure 29-4). When loading film into a flexible plastic sleeve cassette, pull the screens part way out of the cassette to separate the pair. Slowly
slide the film between the folded screens (Figure 29-5). Make sure that the film is seated all the way down to the
fold in the screen.
6. Close the cassette and ensure that the hinge is secured (rigid). Close the snaps or Velcro® closures on the flexible
cassette. When the cassette is not tightly closed, the film and screen contact is not tight, and it causes the radiograph to be blurry.
7. Replace the cover on the film box to protect from white light.
8. Turn on the overhead white light and exit the darkroom.
CHAPTER 29 • EXTRAORAL RADIOGRAPHY AND ALTERNATE IMAGING MODALITIES 369
FIGURE 29-4 Loading a rigid cassette. FIGURE 29-5 Film is placed between the
intensifying screens.
FIGURE 29-6 Static electricity artifacts. Blank area on a panoramic film showing static electricity artifacts.
PROCEDURE 29-1
Loading an extraoral cassette
370 EXTRAORAL TECHNIQUES
according to the x-rays in that part of the image. Screen film is
more sensitive to this type of fluorescent light than to radiation.
When the film is sandwiched tightly between a pair of two
intensifying screens, the x-rays cause the crystals on the screens
to fluoresce and return the emitted light to the film emulsion to
produce the radiographic image (Figure 29-7).
Rare earth screens emit green light when energized by x-rays
and must be paired with green-light–sensitive film. Calcium
tungstate screens give off a blue to violet fluorescent light and
must be paired with blue-light–sensitive film. Inappropriately
interchanging green- or blue-light–sensitive films between calcium tungstate and rare earth screens produces undiagnostic
radiographic images.
The use of intensifying screens decreases the amount of radiation required to produce an image. However, the sharpness of
the radiographic image also is reduced over the images produced
on intraoral films. The sensitivity and image sharpness of different types of intensifying screens varies and depends on the:
• Size of the crystals. The larger the crystal size, the less
radiation required to produce an image. Larger crystals
produce a less sharp image.
• Thickness of the emulsion. The thicker the emulsion, the
faster the speed of the screen, requiring less radiation to produce an image. Thicker emulsion results in a less sharp image.
• Type of phosphor used. Rare earth screens produce a
latent image on the film with less radiation exposure than
calcium tungstate screens.
Although varying speeds of screens are available, the
American Dental Association and the American Association of
Oral and Maxillofacial Radiology recommend that the fastest
speed screen–film combination be used to reduce the amount of
radiation exposure to the patient. While reducing the radiation
required to produce an image, a large crystal size and a thick
emulsion will produce a less sharp radiographic image. The slight
reduction in image clarity produced by fast speed screen–film
combinations is considered acceptable to reduce the radiation
dose to the patient.
Cassettes
The purpose of the cassette is to hold the intensifying screens
in close contact with the film and to protect the film from white
light exposure. Cassettes are available in a variety of shapes
and sizes, depending on the intended use. Cassettes are available as a rigid box or case that may be flat or curved. Rigid
cassettes are usually or
A typical rigid cassette has a front and back
cover joined together with a hinge (Figure 29-8). The front
cover is constructed of plastic to permit the passage of the x-ray
120 * 25 cm2.
5 * 7 in. 113 * 18 cm2 8 * 10 in.
Cassette front (plastic)
X-ray film
Screen support
Screen support
Front screen (fluorescent coating)
Back screen (fluorescent coating)
Cassette back (metal)
Felt padding
Screen
Screen
Film
A
B
C
FIGURE 29-7 Cross-section of cassette showing the effect of x-ray and
fluorescent light on the film. X-ray A strikes a crystal in the screen behind the
film, producing light that then forms latent images in the silver halide crystal of the
film. X-ray B strikes a silver halide crystal in the film, forming a latent image.
X-ray C strikes a crystal in the screen in front of the film, producing light, which
then forms latent images in the silver halide crystals of the film.
FIGURE 29-8 The back side of three rigid cassettes
of various sizes.
CHAPTER 29 • EXTRAORAL RADIOGRAPHY AND ALTERNATE IMAGING MODALITIES 371
beam and must be positioned so that it faces the patient. The
back cover is constructed of heavy metal to absorb remnant
x-rays. A pair of intensifying screens lines the inside of the
front and back covers of the cassette.
Flexible plastic sleeve cassettes are most often used for
exposing panoramic radiographs (see Figure 30-11). Flexible
cassettes measure 5 or and are
composed of a plastic sleeve with intensifying screens inside.
The paired intensifying screens are usually joined together at one
end, so that a film may be inserted in between (Figure 29-5).
Snaps or Velcro® closures seal the cassette to prevent white
light from leaking in.
Film Identification
Extraoral films do not have the embossed identification dot that
intraoral films have to aid in identifying the left and right sides of
the image. Extraoral films are best identified by fastening an
identification letter or plate to one of the corners of the front of
the cassette. Special lettering sets, made of lead, are available for
this purpose. The letters R (for right) and L (for left) can be placed
on the front of the cassette prior to exposure. These identifications become visible on the processed radiograph. Identification
plates can be used to record the patient’s name and date of exposure directly onto the radiograph. Commercial film identification
imprinters are available that permanently image pertinent data on
the processed radiograph (Figure 29-9).
Care of Cassettes and Intensifying Screens
Extraoral cassettes and intensifying screens should be
inspected periodically. Rigid and flexible cassette hinges and
snaps should be checked to ensure light tightness to prevent
film fog. Cassettes should be checked for warping to ensure
close screen–film contact. Poor screen–film contact results in
an image of reduced sharpness (blurry image). Defective cassettes should be repaired or replaced.
Intensifying screens should be examined for cleanliness
and scratches. Debris present on the screens will block the light
given off by the crystals and result in radiopaque artifacts on the
resultant radiographic image. Screens may be carefully cleaned
6 * 12 in. 113 or 15 * 30 cm2
as needed with solutions recommended by the manufacturer.
However, overuse of chemical cleaning may cause scratches and
should be avoided. A scratched or damaged screen will not produce the light needed to expose the film and will result in
radiopaque artifacts.
Grids
Grids are sometimes used in extraoral radiography to absorb
scattered x-rays that contribute to film fog that reduces image
contrast (Figure 29-10). Radiation that strikes the patient’s tissues has the potential to be deflected back toward the film,
reexposing it. A grid is a mechanical device composed of thin
strips of lead alternating with a radiolucent material (usually
plastic). The grid is placed between the patient and the film to
absorb scattered x-rays and reduce film fog to improve image
contrast. However, the use of a grid requires an increased dose
of radiation, usually double the dose of radiation required when
not using a grid. The use of a grid with its increased radiation
dose to the patient must be carefully weighed against the diagnostic benefits. For example, when exposing radiographs to
assess growth and development, a grid may be contraindicated.
However, when evaluating the extent of a tumor, the increased
image contrast obtained by using a grid may be justified.
Exposure Factors
The exposure factors for extraoral techniques vary considerably.
The settings depend largely on the intensifying screen–film
combination, which plays a similar role to intraoral film speed
in determining appropriate exposure settings and the use of digital extraoral radiographic equipment. The patient’s size and tissue density and the target–image receptor distance also must be
considered. Refer to the x-ray equipment and film and screen
manufacturers’ recommendations to determine appropriate mA,
kVp, and impulse settings.
FIGURE 29-9 Film identification printer for imprinting
permanent identification information on the radiographic image.
Film
X-ray
beam
Grid
radiolucent material
lead strips
FIGURE 29-10 Grid used to absorb back scattered radiation
is placed between the patient and the film to absorb scattered x-rays
to reduce film fog.
372 EXTRAORAL TECHNIQUES
Tomography, Computed Tomography,
Cone Beam Computed Tomography
Radiographs are taken with a stationary x-ray source and
image receptor. Structures such as the teeth and the supporting bone that lie along the same path travelled by the x-ray
beam will be superimposed on the radiograph, limiting radiographs to distinctly separate structures. In addition, there
are oral conditions, such as the need for an orthodontic evaluation or implant dentistry when the diagnosis and treatment
planning would be enhanced by three-dimensional imaging.
Tomography is a special radiographic technique that uses
simultaneous movement of the x-ray source and the image
receptor to record images of structures located within a
selected plane of tissue, while blurring structures outside the
selected plane. Tomography produces images by utilizing a
narrow beam of x-rays to image a curved layer or slice of tissue. Tomography has been a valuable tool in imaging the
temporomandibular joint (TMJ) (Figure 29-11). Panoramic
radiography, discussed in Chapter 30, is also based on
tomography. In fact, panoramic x-ray machines are available
with multiple functions, allowing the operator to produce not
only panoramic radiographs, but TMJ tomographs as well
(Figure 29-12).
With digital technological advances, modern-day tomography now uses complex computer systems and multiple image
receptors to produce enhanced two-dimensional and threedimensional images out of the slices of tissue recorded with no
superimposed blurring of the structures that lie outside the
selected plane. A familiar medical use of this technology is a CT
scan or computed tomography. Patients undergoing a CT scan
of the maxillofacial region lie on a table with the head positioned inside the scanner (Figure 29-13). The scanner emits a
narrow, fan-shaped x-ray beam that rotates 360 degrees around
the patient’s head while up to 2,000 image receptors receive the
data. The table supporting the patient moves as the x-rays focus
on each new layer or slice of tissue. Most CT systems have
imaging software programs for dental implant treatment planning. These programs translate the data received by the image
receptors into workable cases the practitioner can use to formulate decisions regarding implant size, orientation, and placement.
FIGURE 29-11 Serial radiographs produced by tomography of the
temporomandibular joint showing the head of the condyle in the glenoid
fossa with the mouth closed, in the at-rest position, and with the mouth open.
(Courtesy of McCormack Dental X-ray Laboratory.)
FIGURE 29-12 A combination panoramic and TMJ
tomography imaging dental x-ray unit. (Courtesy of Planmeca.)
CHAPTER 29 • EXTRAORAL RADIOGRAPHY AND ALTERNATE IMAGING MODALITIES 373
Computed tomography is a highly regarded, accurate method
of choice for imaging bone height, density, and the shape and
contours of the edentulous ridges prior to dental implant
surgery. However, the radiation dose to the patient from computed tomography is high, so this method of imaging must be
balanced with the benefits it will provide. Although the actual
radiation dose to the patient depends on many factors, the
effective dose from a CT scan of the maxilla is estimated to be
between 240 and and between 480 and for
a scan of the mandible. You will recall from Chapter 5 that the
effective dose from a panoramic radiograph is approximately
(See Table 5-3.)
In the desire to use computed tomography technology
for dental applications while limiting the radiation dose to
the patient, CT scanners are now available that are dedicated
for maxillofacial use. Cone beam computed tomography
(CBCT), also called cone beam volumetric imaging (CBVI),
provides accurate, multiplanar images with no superimposed
blurring with lower radiation doses (approximately for
a scan of the maxilla and for a scan of the mandible).
The technology of these lower-dose CT scanners is specifically
targeted at imaging the maxillofacial region for oral health care
applications. In fact, some machines allow the operator to
switch from CBCT or CBVI mode to panoramic radiography,
making this technology increasingly accessible for adoption by
the oral health care practice (Figure 29-14).
The patient position for exposure is seated or standing
upright, similar to the positioning for producing a panoramic
radiograph. The cone-shaped x-ray beam is collimated to
control radiation exposure to record only a limited region
around the dental arches in one rotation around the head,
reducing the radiation dose over CT scans. Whereas digital
sensors used in intraoral radiography use pixels to produce
the image (see Chapter 9), CBCT utilize voxels. A pixel, or
picture element, is essentially a square with two sides.
A voxel, or volume element, adds a third side to this square,
making a cubed area for capturing more data. The computer
software then converts this data into an image that can be
75 mSv
42 mSv
7 mSv.
1200 mSv 3324 mSv
FIGURE 29-13 CT scanner.
FIGURE 29-14 Cone beam volumetric imaging machine.
Designed for the oral health care practice, can also produce panoramic
radiographs. (Courtesy of Gendex Dental Systems/Imaging Sciences Intl.)
read on a computer monitor. The images can be interpreted
and studied from not only the sagittal plane, as film-based
and digital radiographic images are, but also from the coronal and axial planes and as a three-dimension reconstructed
image (Figure 29-15).
At this point in time, CBCT has not been widely taught or
practiced by oral health care professionals and is considered
new technology for dental applications, although widely accepted
in the medical community. Currently most patients who would
benefit from this technology can be referred to a medical
imaging center for the procedure. An expert dental or medical
professional at these centers would be responsible for interpreting the images and providing a report or summary to the
referring dentist. When the CBCT scanning equipment is
available in an oral health care practice, it is usually a specialty
practice such as an orthodontist, periodontist, or specialist in
dental implantology. Even in these practices, unless he or she
has been trained and is comfortable making the final diagnosis, the dentist will often have the images interpreted by a medical expert, especially because these images are likely to reveal
information beyond the teeth and oral cavity. Although the
dentist may be an expert at determining conditions of the teeth
and the supporting structures, conditions beyond the oral cavity such as the oral and nasal airways, paranasal sinuses, and
other tissues outside the maxillofacial region must be examined for potential occult diseases (diseases that were not
apparent clinically).
Cone beam computed tomography will continue to play
an increasingly valuable role in oral health care treatment,
especially as technology finds ways to reduce the radiation
dose to the patient. Some experts in the field of dentistry predict that CBCT will become the standard of care in implant
dentistry in the near future.
374 EXTRAORAL TECHNIQUES
must be paired with green-light–sensitive film. Calcium tungstate
screens emit blue light and must be paired with blue-light–sensitive film. The use of fast-speed screen–film combinations is
recommended to produce acceptable images at a reduced radiation dose to the patient.
Special lettering sets or commercial film imprinters are
used to label and identify extraoral film. Cassettes hold the
intensifying screens in close contact with the film in a lighttight rigid case or a flexible plastic sleeve. Cassettes and intensifying screens should be examined periodically to ensure
optimum performance. Dirty or scratched screens will result in
radiopaque artifacts that compromise diagnosis.
Grids are devices used to absorb scatter radiation that
would fog the film and compromise image contrast. The use of
grids requires increased radiation exposure and so they are not
usually recommended unless a fine detail contrasting image is
required for accurate diagnosis.
Exposure settings for extraoral techniques depend on the
intensifying screen–film combination used, the patient’s size
and tissue density, and the target–image receptor distance.
Radiographs are produced with a stationary x-ray source and
image receptor. Tomography employs a simultaneously moving
x-ray source and image receptor to produce an image within a
selected plane while blurring objects outside the selected layer.
Computed tomography (CT) utilizes complex digital x-ray systems and multiple image receptors to produce images within a
slice of tissue without blurred superimposition of objects outside
the layer of interest. CT scans provide accurate images of bone
REVIEW—Chapter summary
Extraoral radiographs image large areas of the head and facial
regions. Extraoral radiographs are useful in examination of
large areas of the dental arches and skull; to study growth and
development of bone and teeth; in the detection of fractures,
pathological lesions, and diseases of the jaws; in assessment of
impacted teeth; in evaluation of temporomandibular disorders
(TMD); and in treatment planning for dental implants and prosthetics. Orthodontists, prosthodontists, and oral surgeons are
major users of extraoral imaging modalities.
The purpose of exposing the following extraoral radiographs was presented: lateral jaw, lateral cephalometric, posteroanterior (PA) cephalometric, Waters, Reverse Towne,
submentovertex, and transcranial.
Extraoral screen film is used in conjunction with a pair of
intensifying screens housed in a light-tight cassette. Extraoral
film is more sensitive than intraoral film. Careful handling is
needed to avoid static electricity and glove powder artifacts.
Intensifying screens transfer x-ray energy into visible light that
in turn exposes screen film to produce an image. Intensifying
screens intensify the effect of x-rays on the film, resulting in a
reduced dose of radiation required to produce an image. Faster
speed intensifying screens have larger sized fluorescent crystals
(phosphors) and thicker emulsion, but produce a slightly less
sharp image. Rare earth phosphor screens are faster than calcium tungstate screens. Rare earth screens emit green light and
FIGURE 29-15 Image produced by CBCT and reconstructed software. Note the images produced
from different planes and the reconstructed 3D image of the teeth in the arches. (Courtesy of Planmeca.)
CHAPTER 29 • EXTRAORAL RADIOGRAPHY AND ALTERNATE IMAGING MODALITIES 375
height, density, and shape and contours of edentulous ridges prior
to dental implant surgery. Radiation doses from computed tomography are significantly higher than extraoral radiography.
Cone beam computed tomography (CBCT), also called
cone beam volumetric imaging (CBVI), focused on maxillofacial imaging with oral health care applications provides accurate, multiplanar images with no superimposed blurring with
lower radiation doses than CT scans. Some CBCT machines
can produce panoramic radiographs. The practitioner must be
skilled in interpreting images obtained by CBCT, which uses
voxels to reconstruct data received by the image receptor that
can be interpreted and studied from the sagittal, coronal, and
axial planes. CBCT technology will continue to increase in
value as an imaging modality in oral health care treatment.
RECALL—Study questions
1. For which of these purposes are extraoral radiographs
least suitable?
a. Detection of interproximal caries
b. Locating impacted teeth
c. Viewing the sinuses
d. Determining the extent of a fracture
2. Which of these radiographs is most frequently prescribed by the orthodontist?
a. Transcranial
b. Lateral cephalometric
c. Waters
d. Reverse Towne
3. The general practitioner is most likely to use which of
these extraoral radiographs?
a. Posteroanterior cephalometric
b. Reverse Towne
c. Panoramic
d. Submentovertex
4. Which of these radiographs would best image the maxillary sinus?
a. Transcranial
b. Waters
c. Periapical
d. Posteroanterior cephalometric
5. What size film is generally used to produce a cephalometric radiograph?
a.
b.
c.
d.
6. Black artifacts on extraoral radiographs may result from
each of the following EXCEPT one. Which one is the
EXCEPTION?
a. Static electricity
b. Glove powder residue
c. Rapidly removing films from the packaging
d. Scratched intensifying screens
6 * 12 in. 115 * 30 mm2
5 * 12 in. 113 * 30 cm2
8 * 10 in. 120 * 25 cm2
5 * 7 in. 113 * 18 cm2
7. Intensifying screens will
a. increase x-ray intensity.
b. increase image detail.
c. reduce exposure time.
d. decrease processing time.
8. What term describes the crystals used in the emulsion
of intensifying screens?
a. Phosphors
b. Halides
c. Sulfates
d. Bromides
9. Fast intensifying screens have ______________ sized
crystals and ______________ thickness of emulsion.
a. large; decreased
b. large; increased
c. small; decreased
d. small; increased
10. Rare-earth intensifying screens require less radiation to
produce a quality image.
Rare-earth intensifying screens emit blue light when
energized by x-radiation.
a. The first statement is correct. The second statement
is incorrect.
b. The first statement is incorrect. The second statement is correct.
c. Both statements are correct.
d. Both statements are incorrect.
11. Which of these is NOT a way to identify extraoral
radiographs?
a. Embossed identification dot
b. Commercial identification printer
c. Lead letters “R” and “L”
d. Lead plates affixed to the cassette
12. Unsharp (blurry) images result from which of the
following?
a. Film and screens not in close contact
b. Faulty (not tight) hinge on rigid cassette
c. Not closing the cassette tightly
d. All of the above
13. Which of the following is used to help reduce film fog
during exposure of extraoral radiographs?
a. Voxel
b. Cephalostat
c. Grid
d. Phosphors
14. Which of the following is true regarding tomography
when compared to extraoral radiography?
a. Requires less radiation to produce an image of the
maxillofacial region.
b. Utilizes a moving x-ray source and moving image
receptor.
c. Superimposes structures in the path of the x-ray
beam on the image.
d. Less likely to exhibit film fog.
376 EXTRAORAL TECHNIQUES
15. Cone beam computed tomography plays a valuable role
in which of the following?
a. Assessing growth and development of the orthodontic patient.
b. Imaging the height and contour of edentulous ridges.
c. Treatment planning for dental implants
d. All of the above.
REFLECT—Case study
Consider the following patients and conditions. Which of the
seven extraoral radiographs described in this chapter might be
the best recommendation for these cases? (Note: Radiographs
of the skull are difficult to interpret due to the numerous structures that exist in a very small area. These structures often
appear superimposed over each other, requiring multiple views
to obtain a good diagnosis. Therefore, in some of these cases,
although there is usually a best answer, there may be more than
one correct answer.)
1. A 20-year-old patient presents with pain and swelling
from an impacted third molar. The patient can open
only 10 mm. No panoramic unit is available. What is an
alternate extraoral projection type that can be used to
assist with diagnosis for this patient?
2. A 13-year-old patient presents for an orthodontic consultation. Occlusal (teeth) and facial disharmonies (soft
tissue relationships) need to be assessed prior to treatment intervention.
3. A difficult extraction case presents with a severely
decayed maxillary molar. During the extraction procedure, the root tip fractures and is possibly lost in the
sinus cavity.
4. A medically compromised patient suffered a seizure
and fell. A fractured mandibular condyle is suspected.
5. A 69-year-old patient presents with a history of degenerative joint disease that may be affecting the temporal
mandibular joint. An examination for the purpose of
diagnosing ankylosis (a stiffening of the TMJ) is
planned.
6. A patient presents for extraction of several badly
decayed teeth, following which the prosthodontist will
construct a maxillary full denture and a mandibular partial denture.
RELATE—Laboratory application
Because intensifying screens fluoresce visible light when energized by x-radiation, you can perform this experiment to confirm what types of intensifying screens are available for use at
your facility:
Open the cassette to expose the intensifying screens and
place on the counter or operatory chair, face up. No film is
needed. Place the tube head of the intraoral dental x-ray machine
directly over the opened cassette and aim the PID so that x-rays
will strike the exposed intensifying screens. Set the exposure
timer to the maximum setting, a full second, for example. Stand
at least six feet away from the tube head at a 90- to 135-degree
angle (see Figure 6-15) or remain behind a barrier that allows
visual contact with the screens during the exposure (see Figure 3-
7). Depress the exposure button and observe the intensifying
screens. Make note of the color, either blue or green, of the light
emitted during exposure. Match the color observed with what
you learned about calcium tungstate and rare-earth screens.
Next, perform an inventory on the extraoral films available for use at your facility. Does the film, either bluelight–sensitive or green-light–sensitive, match the screens? Use
the information learned in this chapter to explain why this is
important.
REFERENCES
Chau, A. C. M., & Fung K. (2009). Comparison of radiation
dose for implant imaging using conventional spiral
tomography, computed tomography, and cone-beam computed tomography. Oral Surgery, Oral Medicine, Oral
Pathology, Oral Radiology, and Endodontology, 107,
559–565.
Farman, A. G., Nortje, C. J., & Wood, R. E. (1993). Oral and
maxillofacial diagnostic imaging. St. Louis, MO: Mosby.
Horner, K., Drage, N., & Brettle, D. (2008). 21st century
imaging. London: Quintessence Publishing Co.
Miles, D. A. (2008). Color atlas of cone beam volumetric
imaging for dental applications. Chicago: Quintessence
Publishing Co.
White, S. C., & Pharoah, M. J. (2004).Oral radiology: Principles and interpretation (5th ed.). St. Louis, MO: Elsevier.
OBJECTIVES
Following successful completion of this chapter, you should be able to:
1. Define the key words.
2. List uses of panoramic radiography.
3. Compare the advantages and limitations of panoramic versus intraoral radiographs.
4. Explain how the panoramic technique relates to the principles of tomography.
5. Identify the three dimensions of the focal trough.
6. List the components of a panoramic x-ray machine.
7. Explain how to use each of the head positioner guides found on a panoramic x-ray machine.
8. Identify the planes used to position the dental arches correctly within the focal trough.
9. Explain the use of a cape-style lead/lead equivalent barrier or the use of an apron without
an attached thyroid collar.
10. List patient preparation errors and describe how these will affect the appearance of the
panoramic radiograph.
11. Match the patient-positioning errors with the characteristic affect on the appearance of the
panoramic radiograph.
12. List exposure and image receptor handling errors and describe how these will affect the
appearance of the panoramic radiograph.
13. List and identify the anatomic landmarks of the maxilla and surrounding tissues as viewed
on a panoramic radiograph.
14. List and identify the anatomic landmarks of the mandible and surrounding tissues as viewed
on a panoramic radiograph.
15. List and identify soft tissue images as viewed on a panoramic radiograph.
16. List and identify three air space images as viewed on a panoramic radiograph.
17. List and identify machine part artifacts as viewed on a panoramic radiograph.
18. List and identify ghost image artifacts as viewed on a panoramic radiograph.
19. Identify in sequence the basic steps in the panoramic radiographic procedure.
Panoramic Radiography
CHAPTER
30
CHAPTER
OUTLINE
 Objectives 377
 Key Words 378
 Introduction 378
 Purpose and Use 378
 Advantages and
Limitations 378
 Fundamentals
of Panoramic
Radiography 379
 Concept of the
Focal Trough 381
 Components of
the Panoramic
X-Ray Machine 382
 Importance of
Correct Patient
Positioning 386
 Panoramic
Imaging Errors 386
 Normal
Panoramic
Anatomical
Landmarks 392
 Images of
Machine Parts
Viewed on the
Panoramic
Radiograph 397
 Ghost Images
Viewed on the
Panoramic
Radiograph 397
 Review, Recall,
Reflect, Relate 398
 References 401
378 EXTRAORAL TECHNIQUES
Introduction
The panoramic radiograph is probably the most common
extraoral projection used in general oral health care practice.
Panoramic radiography refers to a technique for producing a
broad view image of the entire dentition of both the maxilla and
mandible with the surrounding alveolar bone, the sinuses, and
the temporomandibular joints on a single radiograph (Figure 30-1).
The purpose of this chapter is to explain the fundamental concepts of panoramic radiography and to interpret normal anatomy
and other structures that will be recorded on these images.
Purpose and Use
The term panoramic means “wide view.” Panoramic radiography
is descriptive of the wide view of the maxilla and mandible
produced on a single radiograph. Panoramic radiographs play a
valuable role in:
• Examining large areas of the face and jaws
• Locating impacted teeth or retained root tips
• Evaluating trauma, lesions, and diseases of the jaws
• Assessing growth and development
Panoramic image quality, especially with the introduction of
digital imaging, continues to improve, suggesting that panoramic
radiographs may also aid in the evaluation of large caries and
moderate periodontal diseases. However, panoramic imagery is
not as sharp and detailed as the images produced by intraoral
radiographs. When specific conditions or diseases are suspected,
intraoral radiographs are often prescribed in conjunction with
panoramic radiographs (see Table 6-1).
Advantages and Limitations
The greatest advantage of panoramic radiographs is that they
image a greater area and provide an increased amount of diagnostic information when compared to a full mouth series of
individual radiographs with a reduced amount of radiation dose
to the patient (Box 30-1).In addition, the broad image produced
by a panoramic radiograph is easy for patients to understand,
aiding in the explanation of the diagnosis and the proposed
treatment plan in a manner that is clear and understandable.
Panoramic procedures are relatively easy to perform, requiring
less time than a full mouth series. The simple procedure
demands less patient cooperation, and because the image receptor is not placed intraorally, there is less discomfort, making the
panoramic procedure an acceptable substitute, under certain
conditions, for patients who cannot tolerate intraoral procedures. Because of the relative ease with which a panoramic radiograph may be obtained, there may be a tendency to overuse this
diagnostic tool. It is important to note that research on the use of
panoramic radiographs cautions against using panoramic
images as a screening film for occult disease (diseases that may
exist without signs or symptoms).
FIGURE 30-1 Panoramic radiograph. Provides a broad view of the dental arches.
Note, however, the inherent image distortion as the panoramic view broadens the arches.
(Courtesy of Gendex Dental Systems/Imaging Sciences Intl.)
KEY WORDS
Ala
Ala–tragus line
Cassette holder
Focal trough (layer)
Frankfort plane
Ghost image
Glossopharyngeal air space
Head positioner guides
Midsagittal plane
Nasopharyngeal air space
Negative shadows
Occult disease
Palatoglossal air space
Panoramic
Panoramic radiography
Rotational center
Tomography
Tragus
CHAPTER 30 • PANORAMIC RADIOGRAPHY 379
The greatest limitation of panoramic radiographs is image
quality. Magnification, distortion, and poor definition are inherent
with panoramic techniques. Ghost images, negative shadows,
and other artifacts can make interpreting panoramic images
difficult. Further compromising the ability to obtain quality
images is the difficulty associated with positioning the patient
within the focal trough (area of image sharpness). Manufacturers
design panoramic x-ray machines to be able to image the average
patient. However, it may be difficult to record all structures
with relative clarity when a patient’s dental arches do not fall
into this average range.
Fundamentals of Panoramic Radiography
Panoramic radiography is based on the principle of tomography.
As discussed in Chapter 29, tomography is a special radiographic
technique used to record images of structures located within a
selected plane of tissue, while blurring structures outside the
selected plane. During panoramic imaging as during tomography,
the x-ray source and image receptor move in relationship to each
other. Panoramic x-ray machines operate with the patient positioned between the x-ray tube head and the cassette that holds the
image receptor. The exposure is made as the tube head and
cassette rotate slowly around the patient’s head during the operational cycle (usually about 15 to 20 seconds). The cassette with
image receptor and the x-ray tube head move in directions opposite
each other while the patient stands or is seated in a stationary
position (Figure 30-2). The x-ray tube head moves around the
back of the patient while the cassette with image receptor moves
BOX 30-1 Advantages and Limitations of Panoramic Radiographs
Advantages
• Increased coverage of supporting structures of the oral cavity.
• Reduced patient radiation dose over a film-based intraoral full mouth series of radiographs.
• Can be performed in less time than the exposure of a full mouth series of radiographs.
• Simple procedure to perform.
• May be performed on patients who cannot, or will not tolerate placement of an intraoral image receptor.
• Requires minimal patient instruction and cooperation.
• Infection control protocol minimized.
• Mounting time is eliminated.
• Aids in explaining treatment plan to patients.
Limitations
• Increased image distortion. The amount of vertical and horizontal distortion is not constant—it varies from one part of the radiograph
to another
• Reduced image sharpness.
• Increased occurrence of overlapping of the proximal contact areas, especially in the premolar region.
• Focal trough size and shape limits imaging only those structures that “fit” into the image layer. Teeth with labial or lingual tilting may
not image well.
• The size and shape of the focal trough is predetermined by the manufacturer, therefore not all patients’ arches will be recorded equally well.
• Superimposition of structures (e.g., the spinal column) may make interpretation difficult.
• Soft tissue shadows present on the resulting image may mimic pathology.
• Ghost images present on the resulting image may hide pathology.
• Not useful in detecting incipient carious lesions or early periodontal changes.
• Simple procedure may be overused inappropriately.
• Length of exposure time may limit its use on young children and other patients who cannot remain still throughout the exposure cycle.
• Cost of panoramic machine is significant.
FIGURE 30-2 Panoramic x-ray machine. Radiographer
positions the patient between the image receptor and the x-ray tube
head of this digital panoramic dental x-ray machine.
380 EXTRAORAL TECHNIQUES
around the front. The x-ray beam strikes the patient’s tissues from
the back of the head.
Through the use of a series of rotational points or centers
(differing according to the unit manufacturer), the x-ray beam
is directed toward the moving image receptor to record a select
plane of dental anatomy (Figure 30-3). The rotational center,
which is defined as the axis on which the x-ray tube head and
the cassette rotate, is the functional focus of the projection.
Most panoramic machines available today utilize a continuous
moving rotational center to refocus the x-ray beam during
movement to produce an image (Figure 30-4). This type of
rotational center will keep the inherent horizontal and vertical
magnification of the image relatively constant. All panoramic
images have between 10 and 30 percent image magnification,
depending on where the structures are located in relationship to
the center of the slice of tissue being focused on. It is desirable
to keep the inherent magnification even throughout the image.
The elliptical pattern made by the rotational center in
Figure 30-4 very closely matches the arc of the teeth and jaws
and is likely to keep image magnification relatively constant.
Unlike the concentric or rectangular beam of x-radiation of
intraoral radiography, the x-rays emerge from a narrow vertical
slit opening in the tube head and are constricted to form a narrow
band. This narrow opening collimates (constricts) the x-ray
beam so that a limited amount of tissue is irradiated. The narrow
vertical beam of radiation then passes through the patient and
through a secondary collimator vertical slit in the cassette holder
to expose the image receptor that is moving or rotating in the
opposite direction (Figure 30-5).
Moving x-ray source
Rotational center
Moving image receptor
FIGURE 30-3 Panoramic radiography. The moving x-ray source
passes through the center of rotation in a horizontal plane toward the
path of the moving image receptor. As the beam scans the object (the
dental arches), a continuous image is recorded on the moving image
receptor.
Moving rotational
center
FIGURE 30-4 Moving rotational center allows the x-ray beam
to continuously focus as the tube head and the image receptor
simultaneously move.
A
B
FIGURE 30-5 Slit collimator (A) and slit opening (B) to the
image receptor.
CHAPTER 30 • PANORAMIC RADIOGRAPHY 381
Concept of the Focal Trough
The focal trough or focal layer is where the dental arches
should be positioned to achieve the sharpest image. The focal
trough is that area between the x-ray source and the image
receptor that will be imaged distinctly on the panoramic radiograph (Figure 30-6). Objects located at various distances from
the center of the focal trough become less sharp the farther
away they are located.
C
left right
Tube head
Image receptor
B
left right
Tube head
A
left right Tube head
Image receptor
Image receptor
FIGURE 30-6 Plane of focus within the focal trough. The x-ray beam is focused on imaging the structures that are positioned
closest to the image receptor. As the tube head and image receptor rotate, the x-ray beam is refocused to image the next section of
anatomy. (A) Illustrated here is one moment in the continuous exposure. At this precise moment, the tube head is positioned on the
right side, allowing the x-ray beam to penetrate the right side, then continue on to penetrate the left side and carry the images of the
structures penetrated to the receptor. At this moment the right side is farther from the image receptor than the left side. At this moment
in the exposure sequence, the left side will be recorded on the image, while the right side will be blurred out as a ghost image. (B) As
the tube head and image receptor rotate, the x-ray beam now penetrates the back of head (and the cervical vertebrae), then continues on
to penetrate the anterior teeth. Because the anterior teeth at this moment are closer to the image receptor, the cervical vertebrae will
most likely appear magnified and blurred out as a ghost image, while the anterior teeth will be more distinctly recorded onto the image.
(C) As the tube head and image receptor continue to rotate to the opposite side, the x-ray beam now penetrates the left side first,
blurring it out of the image. The right side is now closer to the image receptor, so it will be imaged more clearly.
382 EXTRAORAL TECHNIQUES
FIGURE 30-7 Diagram of the focal trough.
The panoramic x-ray machine’s moving center rotation system
results in a focal trough that is wider in the posterior regions
and narrower in the anterior regions, making it imperative that
the anterior teeth be positioned precisely to be imaged correctly.
It is important to note that a mistake in positioning the arches in
the anterior region of the focal trough by as little as 3 or 4 mm
will make a significant difference in the degree of magnification
on the resultant radiograph.
Components of the Panoramic
X-Ray Machine
Although considerable differences exist in the size and configuration of panoramic x-ray machines, the operational procedures are
similar and relatively simple (Procedure Box 30-1). Many machines
require that the patient stand during the exposure; others operate
with the patient seated. The machine’s design will determine
whether the patient is positioned to face the radiographer and
away from the machine or to face the machine with their back to
the radiographer. Film-based panoramic radiographs require the
use of either a rigid or flexible cassette with intensifying screens
(Figure 30-8; see Chapter 29); phosphor plates utilize a rigid or
flexible cassette without intensifying screens (Figure 30-9); and
the image receptor, usually a CCD (see Chapter 9), is built into
digital panoramic x-ray machines (Figure 30-10).
All panoramic x-ray machines have four basic components:
1. Rotational x-ray tube head
2. Cassette holder (for film or phosphor plate) or digital image
receptor
3. Head positioner guides
4. Exposure control panel
The x-ray tube used in panoramic x-ray machines generates
electrons to produce x-ray energy similar to x-ray units used for
intraoral exposures. The panoramic tube head is in a fixed vertical
position with the short PID pointing up slightly, about negative
8 degrees. Film-based panoramic machines require that the film
be loaded into a cassette that is then attached to the cassette
holder so that it will rotate in relation with the tube head. Each
machine manufacturer provides specific instructions for attaching the cassette to the unit (Figure 30-11).
FIGURE 30-8 Film-based panoramic x-ray machine.
FIGURE 30-9 Phosphor plates used for indirect digital
panoramic x-ray machine. (Courtesy of Air Techniques.)
The focal trough is three-dimensional, and its actual shape
varies depending on the equipment used (Figure 30-7). The
three-dimensions of the focal trough are (1) anterior–posterior,
(2) lateral or left–right, and (3) superior–inferior or up–down.
CHAPTER 30 • PANORAMIC RADIOGRAPHY 383
PROCEDURE 30-1
Panoramic radiographic procedure*
Cassette and film preparation
1. Examine cassette for proper function. Check hinge for wear. Check for light-tight seal.
2. Examine intensifying screens (if film-based) or phosphor plates for quality. Check for scratches and need
of cleaning.
3. Obtain a box of extraoral film. Ensure that the film sensitivity matches the screen type used (see Chapter 29). The
image receptor is built in to digital panoramic machines and will already be in place.
4. Turn off white overhead light and turn on safelight. (Ensure that safelight color filter recommended
by the film manufacturer is in use.)
5. Remove the cover from the box of film and carefully, with clean, dry hands, remove one film from the
box. Remove slowly to avoid generating static electricity.
6. Handling the film by the edges only, load into the cassette. (When using a flexible cassette, ensure that
the film is inserted between the screens and is seated all the way down to the fold). Close tightly, securing the hinge (rigid cassette) or snaps (flexible cassette). Replace the cover on the box of film prior to
turning on overhead white light and leaving the darkroom.
Unit preparation
1. Clean and disinfect with appropriate disinfectant all surfaces that will come in contact either directly or
indirectly with the patient, such as the:
a. Forehead rest
b. Chin rest
c. Side head positioner guides
d. Patient support handles
e. Chair (sit-down units)
2. Select sterile or disposable biteblock or cotton roll.
3. Attach the cassette onto the cassette holder of the unit according to the manufacturer’s instructions. Ensure that
the cassette is placed so that the exposure will begin at the appropriate edge of the film.
4. Turn on the machine. Raise or lower the overhead assembly to the approximate height of the patient,
and move to the patient-entry position or move out of the way (if necessary) so that the way is clear for
the patient to get into position.
Patient preparation
1. Inform patient of the need for the panoramic radiograph. Explain the procedure, answer patient concerns/questions regarding the procedure, and obtain patient’s consent.
2. Request that the patient remove eyeglasses, necklaces, hair barrettes, facial jewelry (tongue, lip piercing
adornments), removable dental appliances and any other material that may interfere with the radiographic
procedure such as chewing gum or a thick hooded sweatshirt.
3. Place the lead/lead-equivalent cape or apron without a thyroid collar over the patient. Ensure that the
lead apron will not impede the rotation of the cassette or image receptor holder.
*The procedures for taking panoramic radiographs are similar on most panoramic machines. As the complexity of the
controls and head holder adjustments varies from unit to unit, the radiographer should read the manufacturer’s
instructions carefully before attempting to operate an unfamiliar machine.
(Continued)
384 EXTRAORAL TECHNIQUES
PROCEDURE 30-1
Panoramic radiographic procedure* (continued)
Patient positioning
1. To position the arches into the focal trough’s anterior/posterior dimension, instruct the patient to bite on
the bite guide with the anterior teeth occluding edge to edge, or to place the chin completely forward
into the chin rest or against the forehead rest. If available, align the laser light beam at the interproximal
space recommended by the machine manufacturer.
2. To position the arches into the focal trough’s lateral (right–left) dimension, close the head positioner
guides or instruct the patient to view reflection in the mirror (on some units) and align the midsaggital
plane perpendicular to the floor. Utilize unit light beams if available.
3. To position the arches into the focal trough’s superior–inferior dimension, adjust the patient’s chin up or
down until the Frankfort plane is parallel to the floor or until the ala–tragus line is approximately positive
5 degrees to the floor. (Some panoramic x-ray units have indicator lines scribed on the head positioner
guides or projected as a beam of light from the unit to align either the Frankfort plane or the ala–tragus line
to obtain correct superior–inferior patient positioning in the focal trough.)
Exposure
1. Select the appropriate kVp and mA for the patient. Refer to posted exposure settings or use the manufacturer’s recommendations.
2. Instruct the patient to place the tongue up against the hard palate and to close the lips around the bite
guide or cotton roll. (Asking the patient to swallow or suck in the cheeks will assist with correct placement of the tongue and lips.)
3. Instruct the patient to remain still throughout the exposure cycle.
4. Take a position behind a protective barrier or an adequate distance away from the x-ray source and
depress the exposure button for the duration of the cycle. You should be able to watch the procedure
during the exposure from a protected location (see Figure 3-7) to ensure that the patient does not move
and that the rotation of the unit continues unhindered. If patient movement occurs or the unit contacts
the patient or protective barrier cape, release the exposure button to stop the process. The cassette
should be removed from the unit and the procedure should start over, beginning with a new film.
5. When the exposure cycle is complete, move the overhead assembly to the patient-exit position or move
out of the way (if necessary) so that the way is clear for the patient to be released. Remove the protective barrier cape. Return glasses, earrings, appliances, or other personal belongings to the patient.
6. Return the head positioner and overhead assembly to the closed position and turn off the machine.
Discard the disposable bite guide or prepare autoclavable bite guide for sterilization. Clean and disinfect
with appropriate disinfectant all surfaces that came in contact either directly or indirectly with the
patient. (See Step 1.)
Processing
1. Remove the cassette from the cassette holder.
2. Proceed to the darkroom. Turn off the overhead white light and turn on the safelight. Open the cassette
and remove the film from between the intensifying screens. Handle the film with clean, dry hands by the
edges only. Use care to avoid sliding the film across the screens in such a manner that would generate
static electricity or scratch the screens or the film.
3. Manually or automatically process the film according to the manufacturer’s instructions.**
**Prior to processing, a film identification printer may be utilized to permanently label the film with the patient’s name,
the date of exposure and other information (see Figure 29-9).
CHAPTER 30 • PANORAMIC RADIOGRAPHY 385
FIGURE 30-10 Digital panoramic x-ray machine. (Courtesy of
Gendex Dental Systems/Imaging Sciences Intl.)
Because the focal trough is determined and set by the
machine manufacturer, head positioner guides will assist the
radiographer in positioning the patient correctly. Most
panoramic machines are equipped with a biteblock or forehead
rest that allows the radiographer to correctly determine how
far forward or back the patient should be positioned, side
positioner guides or a mirror for determining the correct
side-to-side or right–left or lateral alignment, and a chin rest
FIGURE 30-11 Radiographer preparing to attach flexible
cassette to the cassette holder carriage. Note the markings on the
outside of the cassette that indicate the correct direction for attaching
the cassette to the unit.
to correctly locate how far up or down the arches should be
positioned (Figure 30-12). Some panoramic machines have
beams of light that when turned on to shine on the patient’s face
will guide the operator to find each of these three dimensions
(Figure 30-13).
The exposure control panel will usually allow the radiographer to select the mA and kVp as recommended by the manufacturer (Figure 30-14). The size of the patient and density of
the tissues to be imaged will determine what settings are used.
FIGURE 30-12 Head positioner guides. A biteblock aids the
radiographer in locating the correct forward and back dimension of
the focal trough; side positioner guides aid with locating the correct
left and right dimension; and a chin rest aids with locating the correct
up and down dimension. Note the cape-style lead/lead equivalent
apron without a thyroid collar for use with panoramic exposures.
FIGURE 30-13 Head positioner guides. Beams of light shine
on the patient’s face to aid the radiographer in positioning the arches
in the focal trough. (Courtesy of Gendex Dental Corporation.)
386 EXTRAORAL TECHNIQUES
trough, the radiographer must be able to determine the location
of three facial landmarks. (1) The midsaggital plane (see
Figure 13-13) that divides the patient’s head into a right and left
side must be positioned perpendicular to the floor for the correct
lateral (left–right) position. (2) The ala–tragus line—an imaginary plane or line from the ala (a winglike projection at the side of
the nose) to the tragus (the cartilaginous portion in front of the
acoustic meatus of the ear)—must be positioned approximately 5
degrees down toward the floor. (3) When the ala–tragus line is
positioned correctly, the Frankfort plane—an imaginary plane or
line from the orbital ridge (under the eye) to the acoustic meatus
of the ear—will be parallel to the floor. Some panoramic machines
utilize guides that aid the radiographer in locating the ala–tragus
line, whereas others focus on the Frankfort plane. The radiographer should be able to utilize either landmark (Figure 30-16).
When the arches are correctly positioned within the focal
trough, all teeth and supporting structures are recorded and
there is less unequal magnification and unsharpness over all
parts of the radiographic image (Figure 30-17). If the patient
has been positioned incorrectly, the resultant radiographic
image will exhibit unique errors that are characteristic of the
positioning mistake made. It is important that the radiographer
be able to identify the causes of common panoramic image
errors to be able to apply the appropriate corrective actions.
Patients should be protected with a lead/lead equivalent
barrier when undergoing the panoramic exam. The thyroid collar
must be removed from the apron for use during a panoramic
exposure. Due to the position of the tube head and PID, the
thyroid collar would get in the way of the primary beam and
block the radiation from reaching the tissues. Lead/lead
equivalent aprons are available without a thyroid collar, and
there are cape-style aprons made especially for panoramic use
(see Figures 6-12 and 30-12).
Panoramic Imaging Errors
Panoramic imaging errors may result from incorrectly
preparing the patient for the procedure; incorrectly positioning the patient and dental arches in the focal trough; and
incorrectly handling, exposing, and processing the image
FIGURE 30-15 Aligning the correct anterior–posterior
position with the light beam guide illuminated over the
interproximal space of the canine and the premolar.
The kVp controls the penetrating ability of the beam, so it is
often adjusted up when exposing larger patients or denser tissues
and adjusted down when exposing children and edentulous
patients. The exposure time is preset by the manufacturer and
varies from 15 to 20 seconds to complete the cycle. To activate
the exposure, the radiographer must depress the exposure button
and hold for the duration of the cycle.
Importance of Correct Patient Positioning
Positioning the patient’s head and dental arches within the focal
trough is necessary for producing diagnostic images. Correct
positioning will vary, depending on whether the area of interest is
in the region of the temporomandibular joints, the sinuses, or the
teeth and their supporting structures. Because the focal trough is
predetermined by the panoramic machine manufacturer, the radiographer must refer to the manufacturer’s instructions when
positioning the patient. Each manufacturer provides an instruction manual that must be carefully read and followed. It is the
radiographer’s responsibility to position the patient’s dental
arches in relation to the focal trough to avoid images that are
magnified, diminished, or blurred.
As discussed previously, most panoramic x-ray machines
have guides such as a head positioner, chin rest, or beams of
light that shine on the patient’s face to aid the radiographer in
positioning the patient within the focal trough (Figures 30-12
and 30-13). Because the focal trough or area of image sharpness is three dimensional (Figure 30-7), the patient’s dental
arches must be positioned in the correct: anterior–posterior
(forward or back) position; lateral (left or right) position; and
superior–inferior (up or down) position. Directing the patient to
occlude the anterior teeth in the correct position on the biteblock of the panoramic machine will align the correct anterior–posterior position. Some panoramic x-ray machines have a
light beam guide, that when illuminated can be used to align
with a specific tooth or interproximal space as determined by
the manufacturer. For example, Figure 30-15 illustrates a vertical positioning light that has been aligned with the interproximal space of the canine and the premolar. To correctly align the
dental arches within the other two dimensions of the focal
FIGURE 30-14 The radiographer uses the control panel
to set the exposure.
CHAPTER 30 • PANORAMIC RADIOGRAPHY 387
Orbital ridge
Ala of nose
Tragus
of ear
B Frankfort plane
Ala–tragus line
A
FIGURE 30-16 Landmarks used to position the patient. (A) When the
ala–tragus line is positioned 5 degrees down, (B) the Frankfort plane will be in a
position parallel to the floor.
A B
FIGURE 30-17 Correct positioning. The arches are positioned
correctly within the focal trough in all three dimensions: (A) Anterior–
posterior and left–right; and (B) superior–inferior (up-down).
receptor. The radiographer should possess a working knowledge of the characteristic appearance of errors made in these
steps to avoid producing undiagnostic radiographic images and
to better implement appropriate corrective actions.
Patient Preparation Errors
It is important to remember that the x-ray beam rotates around the
patient from behind. Any objects made of metal or other dense
material located here, such as a necklace, earrings, or hair adornments will be in the path of the primary beam and result in
radiopaque artifacts. These items, along with the patient’s glasses,
dental appliances, patient napkin chain, oral piercings and other
facial jewelry, must be removed prior to exposure. As already
discussed, the thyroid collar must be removed from the lead/lead
equivalent apron for panoramic exposures. There are occasions
when the clothing the patient is wearing may interfere with the
rotation of the tube head. Thickly padded shoulders of clothing
and hooded sweatshirts need to be assessed to ensure that they
won’t impede the movement of the cassette and tube head during
the rotational cycle.
Patient understanding of the procedure and cooperation
are necessary to produce quality images. The patient must
hold still, in position, throughout the exposure. The patient
should be requested to rest the tongue against the palate and
close the lips around the bite guide. The open air space
between the tongue and the roof of the mouth (palatoglossal
PRACTICE POINT
When asked to place the tongue against the roof of the
mouth to reduce the radiolucency caused by the palatoglossal air space, the patient will sometimes incorrectly touch
only the tip of the tongue to the palate. To assist with placing the entire dorsal surface of the tongue flat against the
palate, ask the patient to swallow and note the position of
the tongue. Another method used to get the tongue into
the correct position is to ask the patient to suck in the
cheeks, which automatically raises the tongue into a position flat against the palate. This directive works especially
well when communicating with the child patient.
A B
FIGURE 30-18 Positioning of lips on the biteblock. (A) The lips incorrectly open on the
biteblock. (B) The lips correctly positioned closed around the biteblock.
magnified and widened. Depending on the angle that the
patient is tipped, the condyles can appear higher on one side
than the other.
If the patient’s chin is tipped too low (Frankfort plane
angled downward and ala–tragus line angled downward greater
than 5 degrees), the resultant image will appear as an exaggerated smile (Figure 30-21). The mandibular condyles slant
inward and the nasopharyngeal air space appears larger and
darker, reducing the quality of the image. The appearance of a
reversed smile (frown) results when the patient’s chin is raised
too high (Figure 30-21). Tipping the chin up causes the bottom
of the nasal cavity and the hard palate to widen into a
radiopaque band that obscures the apices of the maxillary teeth.
Tipping the chin up or down will also cause the anterior teeth to
be positioned outside the focal trough, often resulting in the
appearance of root resorption.
If the patient is not standing or sitting up straight, or is
slumped over, the radiation (which strikes the patient from
behind) is attenuated by the compressed vertabrae, resulting
in a wide radiopacity superimposed over the anterior teeth
(Figure 30-22).
Exposure and Film Handling Errors
Careful attention to exposure settings and film handling will
avoid errors that result in undiagnostic radiographs. Consideration should be given to the following. Exposure settings should
be posted near the control panel to avoid over- or underexposures. Extraoral film requires careful handling to avoid static
electricity artifacts (see Figure 29-6). Darkroom safelighting
must be appropriate for light-sensitive extraoral film. Cassettes
should be inspected to ensure a tight contact between film and
intensifying screens. Blurry images result when the film and
screens are not in tight contact. Intensifying screens must be
free of scratches that would result in a loss of image and
radiopaque artifacts.
Careful loading of flexible plastic sleeve cassettes must
ensure that the film is seated all the way down at the fold in
388 EXTRAORAL TECHNIQUES
air space) will create a large radiolucency on the image that
will obscure the root apices of the maxillary teeth. Raising
the flat, dorsal surface of the tongue to the palate utilizes the
soft tissue image of the tongue to “fill in” this airspace and
create a more even density to the image. Closing the lips
together around the biteblock will avoid recording an image
of the lip line across the anterior teeth. Open lips will
create an image that can mimic caries of the anterior teeth
(Figure 30-18).
Positioning Errors
Positioning the patient too far forward in the focal trough
results in all of the anterior teeth appearing blurred and narrowed in width (Figure 30-19). Consequently, when the
patient is too far back toward the tube head, the anterior teeth
will appear blurred and magnified (Figure 30-19). Most
panoramic machines have a relatively narrow focal trough in
the anterior region, requiring precision in locating the forward
and backward dimension of image sharpness. Panoramic
machines will have a forehead rest or may require the patient
to bite on a biteblock to position the arches correctly in this
dimension. When using a biteblock the radiographer should
request that the patient bring both maxillary and mandibular
central incisors into an edge-to-edge position on the biteblock. When using a machine with laser light beams, follow
the manufacturer’s recommendation for aiming the lateral or
vertical beam of light at a predetermined interproximal space.
If the midsaggital plane is not positioned perpendicular to
the floor, the patient’s head will be rotated, turned, or tipped to
the left or to the right. This rotation of the dental arches will
cause the anatomy of condyles, sinus, and teeth on the side
closer to the image receptor to appear narrowed, whereas these
anatomical landmarks on the side closer to the x-ray tube head
will appear magnified and widened (Figure 30-20). When the
patient is positioned too far to the left, the anatomy and teeth on
the right appear magnified and widened. When the patient is
positioned too far to the right, the anatomy on the left appears
CHAPTER 30 • PANORAMIC RADIOGRAPHY 389
A B
D
E
C
ANTERIOR-POSTERIOR POSITIONING
FIGURE 30-19 Incorrect positioning. (A) Arches too far forward, causing the anterior teeth to be positioned outside and forward from the
center of the focal trough. (B) Arches too far backward, causing the anterior teeth to be positioned outside and backward from the center of the
focal trough. (C) Patient positioned too far forward. Note the incorrect position of the laser light beam. Compare with the correct position in
Figure 30-15. (D) Radiographic image resulting from positioning the arches too far forward. Note the blurred and magnified anterior teeth and the
prominent imaging of the spinal column on both sides. (E) Radiographic image resulting from positioning the arches too far backward. Note the
widened and magnified anterior teeth.
390 EXTRAORAL TECHNIQUES
A
receptor
Image
position
Patient’s left
side
Image
receptor
position
Patient’s right
side
Image
receptor
position
Image
receptor
position
Tube
head
Patient’s right
side
B
receptor
Image
position
Image
receptor
position
Image
receptor
position
Image
receptor
position
Patient’s left
side
Tube
head
C
D
LATERAL (LEFT-RIGHT) POSITIONING
FIGURE 30-20 Incorrect positioning: patient’s head is rotated. Midsaggital plane rotated to position the (A) left side of the arches closer
to the image receptor and right side farther away from the x-ray tube head or (B) right side closer to the image receptor and left side farther
away from the x-ray tube head. Diminution is apparent on the side malpositioned closer to the image receptor and magnification is apparent on
the side malpositioned farther away from the x-ray tube head. (C) Patient positioned with the midsaggital plane rotated to the left.
(D) Radiographic image resulting from a position rotated to the left. Note the arches, condyles, sinus, and teeth on the left appear narrowed,
and these anatomical landmarks and teeth on the right appear widened and magnified. Note the higher position of the left condyle.
CHAPTER 30 • PANORAMIC RADIOGRAPHY 391
F
A B C D
E
SUPERIOR-INFERIOR (UP-DOWN) POSITIONING
FIGURE 30-21 Incorrect positioning. (A) Patient’s chin too low. The root apices of the mandibular anterior teeth slant out of
the focal trough. (B) Frankfort plane/ala–tragus line incorrectly aligned to position the chin too low. (C) Patient’s chin too high. The root
apices of the maxillary anterior teeth slant out of the focal trough. (D) Frankfort plane/ala–tragus line incorrectly aligned to position the chin
too high. (E) Radiograph with the characteristic exaggerated “smile” appearance. (F) Radiograph with the characteristic exaggerated “frown”
appearance.
392 EXTRAORAL TECHNIQUES
A
B
CDE
ACHIEVING CORRECT POSTURE POSITIONING
FIGURE 30-22 Incorrect patient positioning (A) Patient not standing up straight. Compare with the correct straight posture illustrated in
Figures 30-12 and 30-13. (B) Radiograph with wide radiopacity representing the compressed vertebrae superimposed over the anterior teeth. (C)
Normal hand position on machine handles. (D) Altered hand position with arms crossed, left hand holding the right handle and right hand
holding the left handle. (E) Altered hand position with arms crossed, left hand holding the right handle with palm facing up and right hand
holding the left handle with palm facing up.
CHAPTER 30 • PANORAMIC RADIOGRAPHY 393
PRACTICE POINT
When standing straight is compromised due to the patient’s
stature or build/size, direct the patient to hold on to the
handles of the machine with the arms crossed. Holding on
to the right handle with the left hand and to the left handle
with the right hand will bring the patient’s shoulders in and
usually out of the way of the machine rotation. For patients
with a very short neck, or short distance between the shoulders and chin, crossing the arms and holding on to the handles with the palms up will further round the shoulders in
and out of the way during the rotational cycle of the exposure (Figure 30-22).
the pair of intensifying screens. Failure to correctly load the
film into the cassette will result in a loss of part of the image.
All panoramic machines have special instructions on
how to load the film cassette onto the rotational arm of the
unit. The manufacturer’s instructions must be followed to
avoid positioning the film so that only a portion gets exposed
(see Figure 29-6).
Normal Panoramic Anatomical Landmarks
The principles of panoramic radiography result in the formation of a unique image. The superimposition of anatomical
structures and the broadening of the arches produces unusual
anatomical relationships in the panoramic image not seen in
intraoral radiographs. In the panoramic radiograph, the
mandible and maxilla as well as the spine are imaged as if they
were split vertically in half down the midsagittal plane, with
each half folded outward. The split cervical spine appears
twice, beyond the mandibular rami at the extreme right and left
edges of the radiograph. Many structures will appear broadened and wider in the same way that a map of the world flattens
and broadens the images of a globe.
To develop the skills needed to recognize normal anatomic
structures viewed on the panoramic radiograph, the radiographer should build on his/her knowledge of how normal
anatomy appears on intraoral radiographs and transfer this
knowledge to the panoramic image. For example, when viewing the maxillary posterior area on a panoramic image, the radiographer can visualize a periapical radiograph taken in this
same area. Because the radiographer would be able to identify
anatomical landmarks most likely to be imaged here (e.g., the
zygomatic arch and maxillary sinus) on an intraoral radiograph,
he/she can expect to see these landmarks here on the panoramic
image as well. Of course the panoramic radiograph will image
more structures of the maxillofacial regions than intraoral radiographs. The structures listed here are those anatomical landmarks that commonly appear on the panoramic image.
PRACTICE POINT
The panoramic radiograph records more structures of the
maxillofacial region than the dentition and the surrounding
supporting bone. Although the oral health care professional is primarily concerned with the oral cavity, panoramic
radiographs must be interpreted by the dentist for all deviations from normal anatomy. Research has indicated that it
is possible to identify carotid arterial plaques on some
panoramic radiographs. This serious medical condition
known as carotid artery stenosis can lead to a stroke, called
a cerebrovascular accident (CVA). When suspected carotid
artery calcifications are recorded on a panoramic radiograph, the dentist must immediately refer the patient to a
physician for further evaluation.
Anatomic Landmarks of the Maxilla and Surrounding
Tissues (Figures 30-23 and 30-24)
Mastoid process of the temporal bone is located posterior
and inferior to the temporomandibular joint (TMJ), appears
as a rounded radiopacity.
Styloid process appears as a long, narrow radiopaque spine
that extends downward, from the inferior surface of the temporal bone, just anterior to the mastoid process.
External auditory meatus (external acoustic meatus), a
round opening in the temporal bone located anterior and
superior to the mastoid process, appears as a round
radiolucency.
Glenoid fossa (mandibular fossa) is a concave, depressed
area of the temporal bone located anterior to the external
auditory meatus. The head of the mandibular condyle rests
in the glenoid fossa. This landmark appears as a concavity
superior to the mandibular condyle.
Articular eminence appears as a rounded projection of the
temporal bone just anterior to the glenoid fossa.
Lateral pterygoid plate appears as a radiopaque winglike
bony projection of the sphenoid bone located posterior to
the maxillary tuberosity.
Maxillary tuberosity appears as a radiopaque rounded
prominence distal to the third molar region.
Infraorbital foramen, a small round opening in the maxilla, appears as a round radiolucency inferior to the border of
the orbit.
Orbit, the bony cavity of the eye socket, appears as a large
round radiolucency with radiopaque borders superior to the
maxillary sinuses. Often, only the inferior border of the orbit
is visible as a radiopaque line.
394 EXTRAORAL TECHNIQUES
1
3
4
5
6
7
8
9
10 11
12
13
14
15
16
17 18
19
2
FIGURE 30-23 Drawing of panoramic radiograph showing the maxilla and surrounding
normal anatomic landmarks. (1) Mastoid process, (2) styloid process, (3) external auditory meatus,
(4) glenoid fossa, (5) articular eminence, (6) lateral pterygoid plate, (7) maxillary tuberosity, (8) infraorbital
foramen, (9) orbit of the eye, (10) incisive canal, (11) incisive foramen, (12) anterior nasal spine, (13) nasal
cavity, (14) nasal septum, (15) hard palate, (16) maxillary sinus, (17) zygomatic process of the zygoma,
(18) zygoma, and (19) hamulus.
1
2
3 4 5 6 7 8 9 10 11 12
13
FIGURE 30-24 Panoramic
radiograph showing the maxilla
and surrounding normal anatomic
landmarks. (1) Mastoid process,
(2) external auditory meatus,
(3) glenoid fossa, (4) articular eminence,
(5) maxillary tuberosity, (6) orbit of the
eye, (7) nasal cavity, (8) nasal septum,
(9) incisive canal, (10) incisive foramen,
(11) hard palate, (12) maxillary sinus,
and (13) chin rest (machine part artifact).
Incisive canal (nasopalatine canal) is a Y-shaped passageway that extends from the floor of the nose to the hard palate
lingual to the central incisors. This landmark appears as a
tunnel-like radiolucency with radiopaque borders located
between the maxillary central incisors.
Incisive foramen (nasopalatine foramen), an opening in
bone located in the anterior midline of the hard palate
directly posterior to the maxillary central incisors, appears
as a round or oval radiolucency between the roots of the
maxillary central incisors.
Anterior nasal spine, a pointed bony projection of the maxilla located at the most anterior point of the floor of the nasal
cavity, appears as a V-shaped radiopacity located at the intersection of the floor of the nasal cavity and the nasal septum.
Nasal cavity (nasal fossa), a pear-shaped compartment of
bone located superior to the maxilla, appears as a large radiolucency above the maxillary incisors.
Nasal septum, a vertical bony wall that separates the right
and left nasal fossae, appears as a vertical radiopacity that
divides the nasal cavity into two parts.
Hard palate, a bony wall that separates the oral cavity from
the nasal cavity, appears as a horizontal thick radiopaque
band superior to the maxillary teeth.
CHAPTER 30 • PANORAMIC RADIOGRAPHY 395
Maxillary sinus consists of two paired cavities that appear
radiolucent, located within the maxilla apical to the maxillary posterior teeth.
Zygomatic process of the maxilla is a bony process of the
maxilla that extends laterally to articulate with the zygoma
and appears as a J- or U-shaped radiopacity located apically
to the maxillary first molar.
Zygoma is the cheekbone that articulates with the zygomatic process of the maxilla. This structure appears as a
thick radiopaque band that extends posteriorly from the
zygomatic process of the maxilla.
Hamulus (hamular process) appears as a very small
radiopaque hooklike process of bone that extends downward
and slightly backward from the medial pterygoid plate of the
sphenoid bone.
Anatomic Landmarks of the Mandible and
Surrounding Tissues (Figures 30-25 and 30-26)
Mandibular condyle appears as a radiopaque rounded bony
process extending from the posterior superior border of the
ramus of the mandible that articulates with the glenoid fossa
of the temporal bone.
Mandibular notch appears as a concavity of bone located
posterior to the coronoid process on the superior border of
the ramus of the mandible.
Coronoid process appears as a large radiopaque triangular
prominence of bone located on the anterior superior ramus
of the mandible.
Mandibular foramen, an ovoid opening in the bone on the
lingual aspect of the ramus of the mandible, appears as a
round radiolucency located in the center of the ramus of the
mandible.
Lingula (meaning “little tongue”) is a small tongueshaped projection of bone located anterior and adjacent
to the mandibular foramen. This landmark appears as a
small radiopacity anterior to the mandibular foramen.
Mandibular canal, a long tunnel-like passageway
extending from the mandibular foramen on the medial
aspect of the ramus of the mandible to the mental foramen on the lateral aspect of the body of the mandible,
appears as a radiolucent tube outlined by two thin
radiopaque lines representing the walls of the canal.
Mental foramen, an opening through which the mental
nerve and related blood vessels emerge on the lateral
aspect of the body of the mandible, appears as a small
round radiolucent area near the roots of the mandibular
premolars.
Mental ridge, appears as a thick radiopaque band representing the prominence of bone located on the external
surface of the mandible and extends anteriorly from the
premolar area to the midline.
Mental fossa appears as a radiolucent depressed area
of bone in the region of the roots of the mandibular
incisor teeth.
Lingual foramen, a very small round opening located in
the center of the genial tubercles on the lingual side of
midline of the mandible, appears as a small round radiolucency located inferior to the apices of the mandibular
incisor teeth.
Genial tubercles The genial tubercles, four small projections of bone located on the lingual surface of the
midline of the mandible, appear as a radiopaque donutshaped circle surrounding the lingual foramen.
1
3
4
5
6 8 9
10
11 12
13
15
14
16
17
2
7
FIGURE 30-25 Drawing of panoramic radiograph showing the mandible and surrounding normal
anatomic landmarks. (1) Mandibular condyle, (2) mandibular notch, (3) coronoid process, (4) mandibular
foramen, (5) lingula, (6) submandibular fossa, (7) mandibular canal, (8) mental foramen, (9) mental ridge,
(10) mental fossa, (11) lingual foramen, (12) genial tubercles, (13) inferior border of the mandible,
(14) mylohyoid ridge, (15) oblique ridge, (16) angle of the mandible, (17) cervical vertabrae.
396 EXTRAORAL TECHNIQUES
1
4
5
2 3
7
8 9 10
11 12 13 14 16 17
15
6
FIGURE 30-26 Panoramic
radiograph showing the mandible
and surrounding normal anatomic
landmarks. (1) Mandibular condyle,
(2) mandibular notch, (3) coronoid
process, (4) mandibular foramen,
(5) lingula, (6) submandibular fossa,
(7) mandibular canal, (8) mental
foramen, (9) mental ridge, (10) mental
fossa, (11) lingual foramen, (12) genial
tubercles, (13) inferior border of the
mandible, (14) mylohyoid ridge,
(15) oblique ridge, (16) angle of the
mandible, (17) cervical vertabrae.
Inferior border of the mandible, composed of the thick
cortical bone that outlines the lower border of the mandible,
appears as a dense radiopaque band.
Mylohyoid ridge, a ridge of bone running diagonally downward and forward on the lingual aspect of the ramus of the
mandible to near the apices of the molar roots, appears as a
dense radiopaque band.
Submandibular fossa, a concavity in the mandible where
the salivary glands are located, appears as a diffuse radiolucenct area below the mylohyoid ridge and the roots of the
mandibular molars.
Oblique ridge, a diagonal ridge of bone on the lateral aspect
of the mandible that runs downward and forward from the
anterior border of the ramus to the level of the cervical portion of the molar and premolar roots, appears as a dense
radiopaque band.
Angle of the mandible is the area at the posterior and inferior corners of the mandible, where the body of the mandible
meets and joins the ascending ramus of the mandible.
Cervical spine radiopaque vertebrae appear beyond the
rami of the mandible at the extreme right and left edges of
the radiograph.
Soft Tissue Images Viewed on the Panoramic
Radiograph (Figures 30-27 and 30-28)
The panoramic radiograph is unique in that some soft tissue
structures (e.g., tongue, soft palate, lipline, and ear) attenuate the beam of radiation enough to become visible on the
radiograph.
1 1
3
4
4
2 2
FIGURE 30-27 Drawing of panoramic radiograph showing soft tissue images. (1) Tongue,
(2) soft palate, (3) lipline, and (4) ear.
CHAPTER 30 • PANORAMIC RADIOGRAPHY 397
Tongue, when positioned correctly, resting on the palate,
allows the soft tissue image of the tongue to be minimally
visible. When visible, the radiopaque dorsal side of the
tongue appears superimposed over the ramus. Remember
that the panoramic view of the tongue will be broadened and
much wider than it appears clinically.
Soft palate, located posterior to the hard palate, separating
the oral cavity from the nasal cavity, appears as a diagonal
radiopaque structure above and posterior to the maxillary
tuberosity.
Lipline image can be avoided if the patient is instructed to
close the lips together around the bite guide (Figure 30-18).
When imaged, the outline of the patient’s lips appears as a
radiopacity superimposed over the anterior teeth.
Ear appears radiopaque and superimposed over the styloid
process, anterior and inferior to the mastoid process.
Air Space Images Viewed on the Panoramic
Radiograph (Figures 30-29 and 30-30)
Air does not attenuate the beam of radiation as much as hard or
soft tissue. For this reason, air spaces appear radiolucent
(black) on a panoramic radiograph. Air spaces that may be
recorded include the palatoglossal, nasopharyngeal, and glos12 3
FIGURE 30-28 Panoramic radiograph
showing soft tissue images. (1) Tongue,
(2) soft palate, and (3) ear.
sopharyngeal air spaces. The radiolucencies produced by these
landmarks often are so dark that they may obscure other structures, compromising the diagnostic ability of the panoramic
radiograph. Careful positioning of the patient into the focal
trough will help minimize the appearance of these negative
shadows. The term negative shadow implies to these radiolucencies because they are shadows of “nothing.”
Palatoglossal air space appears as a radiolucency between
the palate and the tongue. When the patient is instructed to rest the
tongue against the hard palate, the palatoglossal air space negative
shadow is minimized. If the tongue is not correctly positioned
against the palate during exposure, the radiolucency appears
superimposed on or above the apices of the maxillary teeth.
Nasopharyngeal air space is the radiolulcency located
posterior to the nasal cavity. The negative shadow it creates on
the image often appears as a radiolucent diagonal streak
located superior to the radiopaque soft palate. This negative
shadow is emphasized when the patient’s chin is incorrectly
tipped down.
Glossopharyngeal air space is the portion of the pharynx
located posterior to the tongue and oral cavity (the oropharyngeal region). The negative shadow it creates on the image
appears as a vertical radiolucent band superimposed over the
ramus of the mandible.
1 1
3 3
2 2
FIGURE 30-29 Drawing of
panoramic radiograph showing air
space images. (1) Palatoglossal air
space, (2) nasopharyngeal air space,
and (3) glossopharyngeal air space.
398 EXTRAORAL TECHNIQUES
Images of Machine Parts Viewed on
the Panoramic Radiograph (Figures 30-31
and 30-32)
The chin rest, side head positioner guides, and biteblock are
often recorded on a panoramic radiograph. Care should be taken
to identify these artifacts so that they are not confused with normal anatomical landmarks or the presence of disease.
Ghost Images Viewed on the Panoramic
Radiograph (Figures 30-33 and 30-34)
The rotation of the panoramic tube head and the use of a focal
trough to isolate slices or layers of the image creates ghost
images on the resultant panoramic radiograph. Ghost images
are mirror or second images of structures that are penetrated
by the x-ray beam twice. Consider that when the x-ray tube
1 23
FIGURE 30-30 Panoramic radiograph
showing air space images. (1) Palatoglossal
air space, (2) nasopharyngeal air space, and
(3) glossopharyngeal air space.
1
3 3
2 2
FIGURE 30-31 Drawing of
panoramic radiograph showing
images of machine parts.
(1) Biteblock, (2) chin rest, (3) side
positioner guides.
1 2 2
FIGURE 30-32 Panoramic radiograph
showing images of machine parts.
(1) Biteblock, (2) side positioner guides.
CHAPTER 30 • PANORAMIC RADIOGRAPHY 399
head is on the patient’s right side, the x-ray beam penetrates
the right side first. Because this right side is closer to the
x-ray source and farther from the image receptor, the structures here are blurred almost completely out of the image. The
beam continues through the patient to the left side, which is at
that moment closer to the image receptor and inside the focal
trough (Figure 30-6). As the tube head rotates around the back
of the patient, the x-ray beam enters the back of the head and
“refocuses” on imaging the anterior teeth. Because the anterior teeth at that moment are closer to the image receptor, and
in the focal layer, they are being imaged onto the radiograph
and the back of the skull is being blurred out. As the beam
continues around the patient to the left side, the blurring out
and refocusing continues along the predetermined focal layer.
In principle those structures outside the focal trough will not
be imaged on the radiograph. However, a magnified, unsharp
image called a ghost image often appears. For example, when
viewing a panoramic image of the patient’s right mandible, a
ghost image of the left mandible can be observed superimposed over the actual right mandible, as a mirror image
(Figures 30-33 and 30-34). Ghost images appear on the opposite side of the image than the actual structure and will often
appear larger (more magnified) and higher (due to the slight
negative vertical angulation of the PID). Being aware of ghost
images will assist the radiographer in interpreting panoramic
radiographs.
REVIEW—Chapter summary
Panoramic radiography produces a broad view image of both the
maxilla and the mandible on a single radiograph. Panoramic
radiographs are valuable in examining large areas of the maxillofacial region; locating impacted teeth or retained root tips; evaluating trauma, lesions, and diseases of the jaws; and assessing
growth and development.
The greatest advantage of the panoramic radiograph
is that it can image a large region of structures and provide
an increased amount of diagnostic information when compared to a full mouth series of intraoral radiographs. The
greatest limitation of the panoramic radiograph is the image
magnification and distortion that make interpreting the image
difficult.
Panoramic imagery is based on tomography where a slice
or layer of tissue is imaged with relative clarity, while blurring out other structures not of interest. During the panoramic
2 2
1
FIGURE 30-33 Drawing of
panoramic radiograph showing
ghost images. (1) Ghost image of
the spinal column (cervical vertebrae),
(2) ghost image of the opposite side
mandible.
2
2
1
FIGURE 30-34 Panoramic radiograph
showing ghost images. (1) Ghost image of the
spinal column (cervical vertebrae), (2) ghost
image of the opposite side mandible.
400 EXTRAORAL TECHNIQUES
exposure, the image receptor and x-ray tube head move
slowly (about 15–20 seconds cycle) in opposite directions of
each other around the patient’s head. The patient remains still
during the exposure, either in a standing or seated position
(depending on the machine type). Through the use of a series
of rotational points or centers, the x-ray beam is directed
toward the moving cassette to record a select plane of dental
anatomy. The rotational center is defined as the axis on which
the tube head and the cassette rotate. Most modern panoramic
machines use a moving-center rotation.
The focal trough is the area between the x-ray source and
the image receptor where structures will be imaged clearly on
the radiograph. Structures positioned outside the focal trough
will be blurred out of the image. The focal trough is threedimensional, and the size and shape is determined by the
machine manufacturer. Each manufacturer provides instructions and head positioner guides to assit the radiographer in
positioning the patient within the focal trough.
All panoramic units have (1) a rotational x-ray tube
head; (2) a cassette holder for film or phosphor plate or a
built-in digital sensor; (3) head positioner guides; and (4) an
exposure control panel. The PID is collimated to a narrow slit
opening, allowing the x-ray beam to fan out to expose a narrow slice of tissue as the tube head rotates around the
patient’s head. The x-ray beam penetrates the patient from
the back of the head.
Positioning the patient’s head within the focal trough
is key to producing a diagnostic image. Most panoramic
units have a forehead rest, chin rest, or biteblock to aid
the radiographer in positioning the arches in the correct
anterior–posterior dimension; side head positioner guides, a
mirror, or beams of light that shine on the patient’s face to
determine the correct left–right dimension; and a chin rest or
light beams to aid in locating the ala–tragus line or Frankfort
plane to determine the correct superior–inferior dimension of
the focal trough.
Artifacts that compromise diagnostic quality result when
metal or dense material objects, such as a necklace, earrings,
oral piercings, and other facial jewelry, are not removed prior to
exposure. The patient must be instructed to rest the tongue
against the palate and to close the lips around the biteblock
during the exposure to minimize the appearance of these structures on the radiograph. Accurate exposure settings and careful
film handling will avoid errors that result in undiagnostic radiographs.
Positioning errors result in characteristic image appearances. Positioning the arches too far forward in the focal
trough produces blurred and narrowed anterior teeth; positioning the arches too far back in the focal trough produces
blurred and widened anterior teeth. Positioning the arches too
far to the lateral (tipping or turning the head to the right or
left) results in narrowed teeth on the side closer to the image
receptor and magnified teeth on the side closer to the x-ray
tube head. Positioning the patient’s chin too far down results
in an image with an exaggerated “smile.” Positioning the
patient’s chin too far up results in an image with an exaggerated “frown.”
The skilled radiographer should be able to identify normal radiographic anatomy of the maxilla and the mandible,
including soft tissue images and air spaces that appear on a
panoramic radiograph. The radiographer should be able to
distinguish normal radiographic anatomy from artifacts such
as machine parts and ghost images that appear on the radiograph.
RECALL—Review questions
1. A panoramic radiograph is valuable when diagnosing
each of the following EXCEPT one. Which one is the
EXCEPTION?
a. A cyst
b. An impacted molar
c. Recurrent caries
d. A supernumerary tooth
2. Which of these is an advantage of a panoramic radiograph when compared to an intraoral radiograph?
a. A larger region is recorded.
b. The image is magnified.
c. Distortion is eliminated.
d. Definition is improved.
3. Which of these is a limitation of a panoramic radiograph when compared to an intraoral radiograph?
a. Larger radiation dose to the patient.
b. Increased time required for exposure.
c. Superimposition of structures may make interpretation difficult.
d. Requires an increase in patient instruction and cooperation with the procedure.
4. What is the term given to the technique where a slice of
tissue is exposed distinctly, whereas structures outside
the designated area are blurred out of the image?
a. Ghost image
b. Artifact
c. Focal trough
d. Tomography
5. All panoramic radiographs have 10 to 30 percent
magnification.
It is desirable to keep the magnification less in the anterior region and greater in the posterior region.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
6. The panoramic PID is collimated to what shape?
a. Round
b. Rectangular
c. Narrow slit
CHAPTER 30 • PANORAMIC RADIOGRAPHY 401
7. What term is given to the area where structures will be
imaged with relative clarity, whereas structures outside
this area are blurred out of the image?
a. Ghost image
b. Artifact
c. Focal trough
d. Tomography
8. Each of the following is a component of the panoramic
x-ray machine EXCEPT one. Which one is the
EXCEPTION?
a. Rotational x-ray tube head
b. Cassette holder or built-in digital sensor
c. Head positioner guides
d. Variable exposure timer
9. Which dimension of the focal trough does the biteblock
of the panoramic x-ray machine assist the operator with
positioning?
a. Anterior–posterior
b. Lateral (left–right)
c. Superior–inferior
10. Which of the following planes is used to position the
patient correctly within the superior–inferior (up–down)
dimension?
a. Ala–tragus line
b. Frankfort plane
c. Midsaggital plane
d. Both (a) and (b)
11. Which of the following positioning errors results in
anterior teeth that are blurry and narrowed in size?
a. Too far forward in the focal trough
b. Too far backward in the focal trough
c. Too far to the left in the focal trough
d. Too far to the right in the focal trough
12. When the dental arches are rotated to the left, the teeth
on the right side will be positioned closer to the image
receptor.
The teeth closer to the image receptor will appear blurry
and magnified.
a. The first statement is true. The second statement is
false.
b. The first statement is false. The second statement is
true.
c. Both statements are true.
d. Both statements are false.
13. Which of the following positioning errors results in an
exaggerated “smile” appearance of the arches?
a. Midsaggital plane tipped to the left
b. Midsaggital plane tipped to the right
c. Chin tipped too far up
d. Chin tipped too far down
14. The appearance of a large radiolucency that obscures
the maxillary teeth apices results when
a. the lips are not closed around the biteblock during
exposure.
b. the tongue is not resting on the palate during exposure.
c. the lead thyroid collar gets in the way of the primary
beam.
d. facial jewelry (e.g., oral piercing) is not removed
prior to exposure.
15. Which of the following appears radiolucent on a
panoramic radiograph?
a. Nasal cavity
b. Nasal septum
c. Nasal spine
d. Hard palate
16. Which of the following appears radiopaque on the
panoramic radiograph?
a. External auditory meatus
b. Zygomatic process of the maxilla
c. Mental fossa
d. Mandibular foramen
17. Which of the following could be called a negative
shadow?
a. Tongue
b. Ghost image
c. Glossopharyngeal air space
d. Biteblock
18. List three air spaces that may be recorded on panoramic
radiographs.
a. ______________
b. ______________
c. ______________
19. List three machine parts that may be recorded on
panoramic radiographs.
a. ______________
b. ______________
c. ______________
20. What is the term given to a structure that is recorded a second time, with less sharpness, and on the opposite side?
a. Ghost image
b. Focal trough
c. Split image
d. Tomograph
REFLECT—Case study
You have to expose a panoramic radiograph on the following
patients today. Each of these patients presents with a characteristic that will make positioning the patient for the procedure a
challenge. Carefully review each of the patient descriptions and
answer the following questions:
1. What patient positioning step do you anticipate having
a problem with?
2. What error is most likely to occur?
3. What will the image look like?
4. How can you prevent this error from occurring or minimize the result on the image?
5. Write out the specific steps you plan to take to produce
a diagnostic quality image.
Case A
A hyperactive 10-year-old child who seems to be having difficulty paying attention to your directions.
Case B
A young adult with multiple facial piercings, including a
tongue ring and several earrings.
Case C
A young woman with fashionable hair extensions gathered into
a large ponytail.
Case D
A middle-aged man who wears partial dentures that when
removed reveal missing anterior teeth.
Case E
An older woman with osteoporosis who exhibits a pronounced
stooped posture as a result of collapsed vertebrae.
RELATE—Laboratory application
For a comprehensive laboratory practice exercise on this topic,
see Thomson, E. M. (2012). Exercises in oral radiography
techniques: A laboratory manual 3rd ed.). Upper Saddle River,
NJ: Pearson. Chapter 12, “Panoramic radiographic technique.”
REFERENCES
Eastman Kodak. (2000). Successful Panoramic Radiography.
Rochester, NY: Eastman Kodak.
Farman, A. G., Nortje, C. J., & Wood, R. E. (1993). Oral and
maxillofacial diagnostic imaging. St. Louis, MO: Mosby.
Ferrús-Torres, E., Gargallo-Albiol, J., Berini-Aytés, L., &
Gay-Escoda, C. (2009). Diagnostic predictability of digital versus conventional panoramic radiographs in the
presurgical evaluation of impacted mandibular third
molars. International Journal of Oral Maxillofacial
Surgery, 38, 1184–1187.
Horner, K., Drage, N., & Brettle, D. (2008). 21st century
imaging. London: Quintessence Publishing Co.
Langland, O. E., Langlais, R. P., McDavid, W. D., et al.
(1989). Panoramic radiology (2nd ed.). Philadelphia: Lea
& Febiger.
Rushton, V. E., Horner, K., & Worthington, H. V. (1999). The
quality of panoramic radiographs in a sample of general
dental practices. British Dental Journal, 26, 186(12),
630-633.
Rushton, V. E., & Rout, J. (2006). Panoramic radiography.
London: Quintessence Publishing Co.
Serman, N., Horrell, B. M., & Singer, S. (2003). High-quality
panoramic radiographs. Tips and tricks. Dentistry Today,
22(1), 70–73.
Thomson, E. M. (2009). Focusing on the image. How to produce error-free radiographic images for the pediatric
patient. Dimensions of Dental Hygiene, 7(2), 24–26, 27.
White, S. C., & Pharoah, M. J. (2008). Oral radiology: Principles and interpretation (6th ed.). St. Louis, MO: Elsevier.
402 EXTRAORAL TECHNIQUES
403
Answers to Study Questions
Chapter 1
1. c
2. a
3. d
4. e
5. b
6. d
7. c
8. b
9. c
10. a
11. a
12. b
13. d
14. Use Box 1-1 to list uses
Chapter 2
1. a
2. Use chapter information and Figure 2-1
to draw diagram
3. d
4. c
5. b
6. b
7. a
8. d
9. b
10. d
11. Use chapter information to list
properties
12. a
13. c
14. d
15. b
16. a
17. Use chapter information to list sources
18. c
Chapter 3
1. c
2. a
3. d
4. 0.5, 0.75, 20, 6
5. a
6. b
7. d
8. Use chapter information to list
conditions
9. Use chapter information and Figure 3-8
to draw and label diagram
10. c
11. b
12. d
13. a
14. a
15. c
16. c
17. a
Chapter 4
1. Use chapter information to list
criteria
2. d
3. c
4. b
5. d
6. a
7. d
8. d
9. a
10. d
11. b
12. c
13. d
14. a
15. a
Chapter 5
1. a
2. c
3. a
4. d
5. c
6. b
7. b
8. d
9. As low as reasonably achievable
10. Use chapter information to
list responses
11. c
12. a
13. b
14. d
15. c
16. d
17. d
18. c
19. d
20. b
Chapter 6
1. d
2. d
3. b
4. c
5. b
6. c
7. d
8. c
9. d
10. a
11. b
12. c
13. c
14. b
15. Use Table 6-3 to list
organizations.
Chapter 7
1. a
2. d
3. c
4. b
5. b
6. c
7. c
8. b
9. a
10. d
11. a
12. a
Chapter 8
1. b
2. c
3. a
4. a
5. c
6. d
7. b
8. d
9. a
10. c
11. b
12. b
13. b
14. a
15. c
16. b
17. c
18. b
19. a
20. d
21. c
Chapter 9
1. d
2. e
3. c
4. a
5. b
6. c
7. d
8. d
9. d
10. c
11. d
12. e
13. d
14. Use chapter information to list
features
15. c
16. c
17. a
18. b
404 ANSWERS TO STUDY QUESTIONS
Chapter 10
1. d
2. a
3. b
4. a
5. Use chapter information to list items
6. c
7. b
8. c
9. c
10. b
11. d
12. d
13. b
14. d
15. a
16. c
17. c
Chapter 11
1. d
2. a
3. d
4. b
5. Use chapter information to list aspects
6. c
7. Use chapter information to list items
8. c
9. a
10. d
11. b
12. d
13. c
14. a
Chapter 12
1. d
2. Use chapter information to list aspects
3. a
4. a
5. c
6. d
7. b
8. a
9. d
10. c
11. b
12. Use chapter information to complete list.
Chapter 13
1. c
2. a
3. b
4. a
5. a
6. c
7. b
8. d
9. a
10. a
11. b
12. d
13. c
14. d
15. Use chapter information to list
contraindications
16. d
17. a
18. b
Chapter 14
1. d
2. a
3. d
4. c
5. b
6. a
7. d
8. c
9. a
10. c
11. b
12. d
Chapter 15
1. b
2. b
3. d
4. b
5. a
6. a
7. d
8. c
9. d
10. d
11. b
12. b
13. d
14. d
15. d
16. a
17. c
Chapter 16
1. c
2. b
3. b
4. d
5. c
6. b
7. c
8. a
9. d
10. c
11. a
12. d
13. c
14. d
15. d
Chapter 17
1. a
2. d
3. d
4. b
5. c
6. a
7. b
8. a
9. c
10. d
Chapter 18
1. d
2. d
3. c
4. a
5. c
6. c
7. b
8. c
9. a
10. d
11. a
12. c
13. d
14. d
15. c
Chapter 19
1. c
2. c
3. Use chapter information to list objectives
4. d
5. b
6. a
7. d
8. b
9. d
Chapter 20
1. Use chapter information to list agencies
2. b
3. a
4. d
5. Use chapter information to list wastes
6. c
7. a
8. d
9. b
10. c
11. c
Chapter 21
1. Use chapter information to list
advantages
2. d
3. d
4. b
5. d
6. c
7. a
8. d
9. b
10. c
11. a
12. d
13. b
14. d
ANSWERS TO STUDY QUESTIONS 405
Chapter 22
1. c
2. d
3. b
4. b
5. a
6. d
7. a
8. c
9. d
10. b
11. a
12. c
13. b
14. d
15. c
16. b
17. a
Chapter 23
1. b
2. a
3. d
4. d
5. c
6. c
7. b
8. a
9. b
10. c
11. d
12. c
13. a
Chapter 24
1. b
2. d
3. a
4. b
5. c
6. a
7. a
8. c
9. b
10. d
11. c
12. a
13. b
14. b
Chapter 25
1. b
2. Use Box 25-1 to list uses
3. c
4. d
5. c
6. a
7. b
8. Use chapter information to list
limitations
9. d
10. c
11. a
12. b
Chapter 26
1. Use chapter information to list
conditions
2. c
3. b
4. d
5. a
6. d
7. a
8. b
9. d
10. d
11. c
12. a
13. b
14. a
15. b
16. d
17. c
18. d
Chapter 27
1. Use chapter information to list
actions
2. b
3. a
4. c
5. b
6. d
7. a
8. d
9. b
10. d
11. d
12. a
Chapter 28
1. d
2. b
3. a
4. b
5. c
6. d
7. a
8. a
9. d
10. c
11. b
12. b
13. d
14. d
15. b
16. Use chapter information to list reasons.
Chapter 29
1. a
2. b
3. c
4. b
5. b
6. d
7. c
8. a
9. b
10. a
11. a
12. d
13. c
14. b
15. d
Chapter 30
1. c
2. a
3. c
4. d
5. a
6. c
7. c
8. d
9. a
10. d
11. a
12. d
13. d
14. b
15. a
16. b
17. c
18. Use chapter information to list air
spaces
19. Use chapter information to list machine
parts
20. a
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407
Glossary
Abscess: A localized pus formation often accompanied by swelling
and pain. When involving an infected tooth, an abscess is usually
located near the apex of the roots. May be chronic or acute. Appears
radiolucent when large enough to be visible on a radiograph.
Absorbed dose: The amount of energy deposited in any form of
matter, such as teeth, soft tissues, treatment chair, air, and so forth,
by any type of radiation (alpha or beta particles, x- or gamma rays,
etc.). The units for measuring the absorbed dose are the gray (Gy)
and the rad (radiation absorbed dose).
Absorption: The process through which radiation imparts some or
all of its energy to any material through which it passes.
Acetic acid: A chemical in the fixer solution that provides the acid
medium to stop further development by neutralizing the alkali of
the developer.
Acidifier: A chemical (acetic acid) in the fixer solution that neutralizes the alkali in the developer solution and stops further action of
the developer.
Acquired immune deficiency syndrome (AIDS): The end stage
of an infection with the human immunodeficiency virus (HIV).
A complex disease that interferes with the body’s immune system.
Activator: A chemical (usually sodium carbonate) in the developer
solution that causes the emulsion on the radiographic film to swell.
Initiates the reducing action of the developing agents. Sodium carbonate makes the developer alkaline.
Acute radiation syndrome: Symptoms of the short-term radiation
effects after a massive dose of ionizing radiation.
Added filtration: Added to the inherent filtration built into the
x-ray machine. Added filtration is in the form of thin disks of pure
aluminum, which can be inserted between the x-ray tube and the
lead collimator when the inherent filtration is not sufficient to meet
modern radiation safety requirements.
Advanced caries: A classification of proximal surface caries. Category where caries has progressed all the way through the enamel, to
or through the dentinoenamel junction (DEJ) but less than halfway
through the dentin toward the pulp
AIDS: See Acquired immune deficiency syndrome..
Ala: The wing of the nose. The depression at which the nostril connects
with the cheek. Used as a facial landmark in dental radiography.
ALARA: As low as reasonably achievable. Adopted as a culture and
attitude by professionals who work with ionizing radiation to minimize radiation exposure and risks.
Ala–tragus line: An imaginary plane or line from the ala of the nose
(a winglike projection at the side of the nose) to the tragus of the
ear (the cartilaginous projection in front of the acoustic meatus of
the ear). Important in determining the correct position of the
patient’s head.
Alkaline: Having a pH greater than 7. Less than 7 is acidic, 7 is neutral.
Alpha particle: A common form of particulate (corpuscular) radiation. Alpha particles contain two protons and two neutrons and are
positively charged.
Alternating current (AC): A flow of electrons in one direction, followed by a flow in the opposite direction.
Aluminum equivalent: The thickness of aluminum affording the
same degree of attenuation, under specified conditions, as the material in question.
Alveolar (crestal) bone: That portion of the maxillary or mandibular bone that immediately surrounds and supports the roots of the
dentition.
Alveolar process: The most coronal portion of the alveolar bone.
Appears radiopaque when visible on a radiograph.
Alveolus: In dentistry, that part of the alveolar bone that forms the
bony socket in which the roots of the tooth are held in position by
fibers of the periodontal ligament.
Amalgam: Metallic restorative material.
Amalgam tattoo: The bluish-purple color of the gingival tissue
caused by fragments of amalgam under the tissue.
Ameloblastoma: An odontogenic tumor of enamel origin that does
not undergo differentiation to the point of enamel formation.
American Dental Assistants Association (ADAA): Professional
organization for the purpose of promoting the dental assisting profession in ways that enhance the delivery of quality oral health care
to the public.
American Dental Association (ADA): Professional organization
of dentists committed to the public’s oral health through professional advancement, research, education, and the development of
standards of care.
American Dental Hygienists’ Association (ADHA): Professional
organization for the purpose of advancing the art and science of
dental hygiene by ensuring access to quality oral health care and
increasing awareness of the cost-effective benefits of prevention.
Amperage: The strength of an electric current measured in amperes.
Ampere (A): The unit of intensity of an electric current produced by
1 volt acting through a resistance of 1 ohm.
Analog: Relating to the mechanism in which data is represented by
continuously variable physical quantities.
Anatomical order: The order in which the teeth are arranged in the
dental arches.
Angle of mandible: The area at the posterior and inferior corners
of the mandible, where the body of the mandible meets and joins
the ascending ramus of the mandible.
Angstrom: A unit of measurement that describes the wavelengths of
certain high-frequency radiation. One angstrom unit (AU or Å)
measures 1/100,000,000 of a centimeter. Most wavelengths used in
dentistry vary from about 0.1 AU to a maximum of 1.0 AU.
Angular chelitis: Fissuring and ulcerations at the corners of the
mouth.
Angulation: The direction in which the central ray and the PID of
the x-ray machine are directed toward the teeth and the image
receptor. See Horizontal angulation, Negative angulation, Positive
angulation, and Vertical angulation.
Ankylosis: A stiffening of a joint, such as the TMJ, caused by a
fibrous or bony union. In dentistry the term can also apply to a
union of the tooth to the alveolus caused by mineralization and
hardening of the fibers of the periodontal ligament.
Anode: The positive electrode (terminal) in the x-ray tube. Tungsten
block, normally set at a 20-degree angle facing the cathode, imbedded in the copper portion of the terminal.
Anodontia: A congenital absence of teeth. Any tooth in the dental
arch may fail to develop. The teeth most frequently absent are the
third molars, the premolars, and the maxillary lateral incisors.
Anomaly: A deviation from the normal.
Anterior nasal spine: V-shaped projection from the floor of the
nasal fossa in the midline. Appears as a triangle-shaped radiopacity.
Antihalation coating: A dye added to the nonemulsion side of
duplicating film to prevent backscattered ultraviolet light from
coming through the films and creating an unsharp image.
Antiseptic: Refers to agents used on living tissues to destroy or stop
the growth of bacteria.
Apical foramen: The opening to the pulp canal at the apex (terminal
end) of the root of the tooth. A three-rooted tooth would have three
apical foramina.
Appearance: Outward impression of self that the radiographer presents to the patient.
Apprehensive: To be anxious or fearful about the future.
Area monitoring: The routine monitoring of the level of radiation
in an area such as a room, building, space around radiation-emitting equipment, or outdoor space.
Arrested caries: Caries that are no longer progressing.
Artifacts: Images other than anatomy or pathology that do not contribute to a diagnosis of the patient’s condition.
Artificial intelligence: Ability of a computer to perform decision
making similar to a human being.
Asepsis: The absence of septic matter, or freedom from infection.
Atom: The smallest particle of an element that has the properties of
that element. Atoms are extremely minute and are composed of a
number of subatomic particles. See Proton, Electron, and Neutron.
Atomic number (also called Z number): The total number of
protons in the nucleus of an atom.
Atomic weight (also called A number or mass number): The
total number of protons and neutrons in the nucleus of an atom.
Attitude: The position assumed by the body in connection with a
feeling or mood.
Automatic processor: A machine that develops, fixes, washes, and
dries radiographic film.
Autotransformer: A special single-coil transformer that corrects
fluctuations in the current flowing through the x-ray machine.
Background radiation: Ionizing radiation that is always present.
Consists of cosmic rays from outer space, naturally occurring radiation from the earth, and radiation from radioactive materials.
Barrier envelope: Plastic sheaths used to seal intraoral film packets, phosphor plates, and digital sensors to protect from contact
with fluids in the oral cavity during exposure.
Base material: A thick layer of cement used as a cavity preparation
under a restoration. Base material often appears slightly more
radiopaque than dentin.
Beam indicating device (BID): See Positioning indicating device
(PID).
408 GLOSSARY
Benign: Noncancerous. Not usually an immediate threat to overall
health.
Beta particle: A form of particulate radiation. High-speed negative
electrons.
BID: Beam indicating device. See Positioning indicating device (PID).
Binding energy: The internal energy within the atom that holds its
components together.
Biodegradable: Capable of being broken down into harmless
products by living organisms such as those found in a wastewater
treatment facility.
Bisecting technique (bisecting-angle or short-cone technique): An exposure technique in which the central beam of
radiation is directed perpendicular to an imaginary line that
bisects the angle formed by the recording plane of the image
receptor and the long axes of the teeth.
Bisector: The imaginary line that bisects the angle formed by the
image receptor and teeth. See Bisecting technique.
Biteblock: A plastic or polystyrene device that functions to hold the
image receptor in position while it is being exposed. The patient
occludes and holds the image receptor in place by biting on the
biteblock.
Bite extension: That portion of the biteblock that allows the patient
to occlude in such a way that image receptor will be positioned parallel to the long axes of the teeth.
Bitetab: An extension, made out of heavy paper or plastic, that is
attached at the center of the image receptor and on which the patient
bites to stabilize the image receptor during a bitewing exposure.
Bitewing radiograph: An intraoral radiograph that shows the
crowns of both the upper and lower teeth.
Bremsstrahlung radiation: See General radiation.
Buccal caries: Caries that involves the buccal surface of a tooth.
Buccal-object rule: Principle that structures portrayed in two or
more radiographs exposed at different angles will appear to shift
positions.
Calcium tungstate: Barium strontium sulfate salt crystals that are
used in intensifying screens. When x-rays are absorbed, the crystals fluoresce and emit energy in the form of blue light.
Calculus: Calcified microbial plaque.
Cancellous bone: See Trabecular bone.
Canthus: The angle at either end of the slit that separates the eyelids.
The inner canthus is nearest the nose. The outer canthus is farthest
from the nose.
Carcinoma: Malignant growth of epithelial cells. A form of cancer.
Caries: Disease of the calcified tissues of the teeth. The inorganic
portion is demineralized and the organic tissues are destroyed.
Cassette: A rigid or flexible extraoral film or phosphor plate (indirect
digital technology) holder. Cassettes contain a pair of intensifying
screens.
Cassette holder: That part of a panoramic x-ray machine where the
cassette is positioned for exposure.
Cathode: The negative electrode (terminal) in the x-ray tube. The
cathode consists of a tungsten filament wire that is set in a molybdenum focusing cup that directs the cathode stream toward the target
on the anode.
Caustic: Capable of burning biological tissues.
Cemental (root) caries: Caries that develops on the roots of teeth
between the enamel border and the free margin of the gingiva.
Cementoenamel junction (CEJ): The area where the enamel
covering of the tooth crown meets the cementum covering of the
tooth root.
Cementum: One of the four basic tooth structures. The thin layer of
dense tissue that covers the root of a tooth. Because the cementum
layer is thin, it is generally radiographically indistinguishable from
dentin. When the condition of hypercementosis presents, the overgrowth of cementum will appear radiopaque and bulbous.
Central ray: The central portion of the primary beam of radiation.
Cephalostat: A device used to stabilize the patient’s head in a plane
that is parallel to the image receptor and at right angles to the central rays of the x-ray beam. Ear rods that can be placed into the
openings of the acoustic meatus of the ear help to accomplish this.
Cervical burnout: A radiolucency often observed on the mesial and
distal root surfaces near the cementoenamel junction. The radiolucent appearance is caused by the concave shape of the root at the
cervical line and may be mistaken for caries.
Chairside manner: Refers to the conduct of the dental radiographer
while working at the patient’s chairside.
Chairside processing: See Rapid processing
Characteristic radiation: A form of radiation originating from an
atom following removal of an electron or excitation of the atom.
The wavelength of the emitted radiation is specific for the element
and the particular energy levels involved.
Charge-coupled device (CCD): A CCD is a solid-state detector
used in many electronic devices such as video cameras and fax
machines. A CCD is used as the image receptor found in digital
sensors. Converts x-rays to electrons that are sent to a computer via
a wire, or wirelessly via radio frequency.
Code of ethics: A professional organization’s principles to assist
members in achieving a high standard of ethical practice.
Coherent scattering: Radiation that is scattered when a low-energy
x-ray passes near an atom’s outer electron. Approximately 8 percent of interactions of matter with the dental x-ray beam are the
result of coherent scattering.
Coin test: Quality control test used to determine the adequacy of
safelighting in the darkroom.
Collimation: The restriction of the useful beam to an appropriate
size. Intraoral beam diameter is collimated to 2 3/4 in. (7 cm) at the
skin surface.
Collimator: A diaphragm, usually lead, designed to restrict the
dimensions of the useful beam.
Communication: The process by which information is exchanged
between two or more persons.
Complementary metal oxide semiconductor (CMOS): A solidstate integrated circuit similar to the CCD. Used in digital radiography as an image receptor in the intraoral sensor. Converts x-rays to
electrons that are sent to a computer via a wire, or wirelessly via
radio frequency.
Composite (composite resin): Tooth-colored material used for
restorations.
GLOSSARY 409
Compton effect (Compton scattering): An attenuation (absorption) process for x- and gamma radiation in which a photon interacts
with an orbital electron or an atom to form a displaced electron and
a scattered photon (x-ray) of reduced energy.
Computed tomography (CT): Radiographic imaging technique
that images an isolated “slice” of tissue while blurring out other
structures.
Condensing osteitis: Term used to describe the formation of compact sclerotic bone. Such areas of hardened bone are frequently
seen on dental radiographs and appear more radiopaque than the
surrounding bone areas. Such areas are generally irregular in shape
or location.
Condyle: A rounded knob or projection on a bone, usually where
that bone articulates (joins) with another bone. The condyle of the
mandible articulates with the glenoid fossa (depression) of the temporal bone.
Cone: Older term used to describe the positioning indicating device
(PlD) or beam indicating device (BID).
Cone beam computed tomography (CBCT): Computed tomography (CT) scanning that is designed specifically for maxillofacial
use. Patient radiation dose is significantly less when compared
with conventional CT exposure of the maxillofacial region.
Cone beam volumetric imaging (CBVI): See Cone beam computed tomography (CBCT).
Conecut error: A term used to describe a technique error in which
the central beam is not directed toward the center of the image
receptor, resulting in a blank area in that part of the radiograph that
was not reached by the radiation.
Confidentiality: Private information, such as dental records, that is
protected by law from being shared with nonprivileged individuals.
Consumer-Patient Health Act: Action that sought to establish
minimum standards for personnel who administer radiation in
medical and dental radiographic procedures. Passed and signed
into law to protect patients from unnecessary radiation.
Contact point: The area of a tooth surface that touches another
tooth. This generally refers to the mesial surface of one tooth making contact with the distal surface of the tooth adjacent to it in the
dental arch. The spot where the teeth actually touch is the contact
point, and the area between the contact point and the gingiva (gum)
is called the embrasure.
Contamination: The soiling by contact or mixing.
Contrast: The visual differences between shades ranging from
black to white in adjacent areas of the radiograph. A radiograph
that shows few shades has a short-scale or high contrast. A radiograph that shows many variations in shade has a long-scale or
low contrast. High kilovoltage produces a radiograph with longscale contrast. Low kilovoltage produces a radiograph with shortscale contrast. Digital software can be used to adjust the contrast of
digital images.
Control panel: That portion of the x-ray machine that houses the
major controls. Includes the line switch, timer, milliamperage and
kilovoltage selectors, and the exposure button.
Coronoid process of the mandible: The pointed, anterior process
on the upper border of the mandible.
Cortical bone: The solid, outer portion of the dense, compact bone.
Appears very radiopaque on radiographs.
Coulombs per kilogram (C/kg): Système Internationale unit for
measuring exposure. A coulomb is a unit of electrical charge (equal
to electrons). The unit C/kg measures electrical charges
(ion pairs) in a kilogram of air.
Cross-contamination: To contaminate from one place or person to
another place or person.
Cross-sectional technique: An occlusal radiographic technique in
which the central ray is directed perpendicular to the image receptor.
Crown: That portion of the tooth covered with enamel. “Clinical
crown” refers to the entire portion of a tooth that is visible in the
oral cavity. May also refer to a metallic or porcelain or combination
of metal and porcelain restoration.
Crystal: Term used to refer to the silver halide combinations that are
present in the film emulsion. Larger crystals require less radiation
exposure to produce an image. However, larger crystal size may
result in slightly less image resolution.
Cultural barriers: When language, beliefs, traditions, and familiar
influences become obstacles to the patient achieving optimal oral
health.
Cumulative effect: The theory that radiation-exposed tissues accrue
damage and may function at a diminished capacity with each
repeated exposure.
Cyst: An epithelium-lined sac containing fluid or other fibrous or
solid materials that appear radiolucent. Common cysts observed
on dental radiographs are dentigerous, follicular, radicular (apical
or periapical), and residual.
Darkroom: A light-tight room with special safelighting where x-ray
film is handled and processed.
Daylight loader: A light-shielded compartment attached to an automatic processor so films can be unwrapped in a room with white
light.
“Dead-man” switch: A switch so constructed that a circuit-closing
contact can only be maintained by continuous pressure by the
operator.
Dead pixel: Term given to a damaged pixel that does not respond to
x-radiation exposure. A dead pixel will not record radiographic
information.
Decay: The radioactive disintegration of the nucleus of an unstable
atom by the emission of particles, photons of energy, or both.
Definition: Sharpness and clarity of the outline of the structures in a
radiographic image. Poor definition is generally caused by movement of the patient, image receptor, or the tube head during exposure.
Dens in dente: A developmental anomaly in which the enamel
invaginates within the body of the tooth.
Density: The overall darkening or blackening of the radiographic
image. Increasing or decreasing the milliamperage and exposure
time (milliampere/second) affects density. Digital software can be
used to adjust the density of digital images.
Dentigerous cyst: A cyst derived from the enamel organ and
always associated with the crown of a tooth.
Dentin: One of the four basic tooth structures. The chief tissue of the
tooth that surrounds the pulp. Dentin is covered by enamel on the
crown of the tooth and by cementum on the root. Appears slightly
less radiopaque than enamel.
Dentinoenamel junction (DEJ): The junction between the dentin
and enamel of a tooth.
6.25 * 1018
410 GLOSSARY
Dentition: Teeth. The term dentulous refers to areas of the jaws
having teeth.
Deterministic (nonstochastic): Observable adverse biological
effects caused by radiation exposure. The severity of change in
tissues depends on the radiation dose.
Developer: The chemical solution used in film processing that
makes the latent image visible.
Developing agent: Elon and hydroquinone, substances that reduce
the halides in the film emulsion to metallic silver. Elon brings out
the details, and hydroquinone brings out the contrast in the film.
Diagnosis: The art of differentiating and determining the nature of a
problem or disease.
Digital image: Radiographic image that exists as bits of information
in a computer file. Special computer software constructs an image
on a monitor for viewing.
Digital imaging: A method of producing a filmless radiographic
image using a sensor (instead of film) and transmitting the electronic information directly into a computer, which serves to
acquire, process, store, retrieve, and display the radiographic
image. The terms digital imaging and digital radiography are often
used interchangeably.
Digital Imaging and Communications in Medicine (DICOM):
A joint committee formed in 1983 by the American College of
Radiology and the National Electrical Manufacturers Association
to create a standard method for electronic transmissions of digital
images, the goal of which is to achieve compatibility and ease
exchange of electronic information between digital image systems.
Digital radiograph: See Digital image.
Digital subtraction: Using a computer to superimpose two standardized radiographic images, causing the like areas of the image
to “cancel” each other out, leaving only the changes visible.
Digitize: To convert an image into a digital form that can be
processed by a computer.
Dilaceration: A sharp bend in the tooth root.
Direct current (DC): Electric current that flows continuously in one
direction. Similar to current produced in batteries. Ideal for use
with digital imaging.
Direct digital imaging: A method of directly obtaining a digital
image by exposing an intraoral sensor to x-rays to produce an
image that can be viewed on a computer monitor.
Direct supervision: Means the dentist is present in the office when
the radiographs are taken on patients.
Direct theory: States that cell damage results when ionizing radiation directly hits critical areas within the cell.
DIS (direct ion storage) monitor: A personnel radiation monitoring device that uses a miniature ion chamber to absorb radiation.
Exposure is determined through digital processing.
Disability: A physical or mental impairment that substantially limits
one or more of an individual’s major life activities.
Disclosure: The process of informing the patient about the risks and
benefits of a treatment procedure.
Disinfect: Chemical applications that reduce disease-producing
microorganisms to an acceptable level.
Distomesial overlap: When the projection angle of the x-ray beam
is directed from distal to mesial, resulting in overlapping error.
Disto-oblique periapical radiographs: Periapical radiographs
that utilize a tube shift to help image posterior objects such as
impacted third molars. Shifting the tube to the distal, causing the
x-rays to be directed from the distal aspect, will project the posterior object forward onto the image receptor.
Distortion: The variation in the true size and shape of the object
being radiographed.
Dosage: The radiation absorbed in a specified area of the body measured in grays (Gy) or rads.
Dose: The amount of absorbed radiation in grays or rads at any given
point. Dose may refer to absorbed dose, depth of the dose, entrance
dose, or surface dose.
Dose equivalent: Compares the biological effects of various types
of radiation. Dose equivalent is defined as the product of the
absorbed dose times a biological effect qualifying factor. Because
the qualifying factor for x-rays is one, the absorbed dose and the
dose equivalent are equal. The units for measuring the dose equivalent are the sievert (Sv) and the rem.
Dose-response curve: Graph produced when radiation dose and
the resultant biological response are plotted.
Dosimeter: A radiation measuring device.
Double exposure: Using the same image receptor to expose two
radiographs. Results in an overexposed, double-image error.
Duplicate radiograph: A copy made of a radiograph. Useful in
referrals, consultations, and for submitting to insurance companies
for payment of dental treatment.
Duplicating film: A photographic film similar to x-ray film. Duplicating film is exposed by the action of infrared and ultraviolet light
rather than by x-rays. Used to duplicate x-ray films in a contactprinter-type x-ray duplicating unit.
Edentulous: Without teeth. Areas of the jaws with no teeth.
Effective dose equivalent: Aids in making more accurate comparisons between different radiographic exposures. Compensates
for the differences in area exposed and the tissues that may be in
the path of the x-ray beam. Measured in microsieverts
Electric current: The flow of electrons through a conductor.
Electrical circuit: A path of electrical current.
Electrode: Either of two terminals of an electric source. In the x-ray
tube, either the anode or the cathode.
Electromagnetic radiation: Forms of energy propelled by wave
motion as photons. This is a combination of electric and magnetic
energy. Has no charge, mass, or weight and travels at the speed of
light. Differs in wavelength, frequency, and properties. For convenience, electromagnetic radiations are arranged in diagrammatic
form as the electromagnetic spectrum.
Electromagnetic spectrum: Types of electromagnetic energies
arranged in diagrammatic form on a chart. Include radio and television waves, infrared waves, visible light, ultraviolet waves, x-rays,
gamma rays, and cosmic radiations. The longer wavelengths are
measured in meters and the shorter ones in centimeters or angstroms.
Electron: A small, negatively charged particle of the atom containing
much energy and little mass.
Electron cloud: A mass of free electrons that hovers around the
filament wire of the cathode when it is heated to incandescence.
The number of free electrons increases as the milliamperage is
increased.
1mSv2.
GLOSSARY 411
Electronic noise: The digital equivalent to film fog. An electrical
disturbance that clutters the digital image reducing image clarity
and contrast.
Element: In chemistry, a simple substance that cannot be decomposed by chemical means.
Elon: Developer reducing agent that converts exposed silver halide
crystals to black metallic silver. Builds up gray tones in the image.
Elongated image : Refers to a distortion of the radiographic image
in which the tooth structures appear longer than the anatomical
size. Often caused by insufficient vertical angulation of the central
beam.
Elongation: See Elongated image.
Embrasure: The space between the sloping proximal surfaces of the
teeth. The space may diverge facially, lingually, occlusally, or apically. The interdental papillae normally fill most of the apical
embrasures.
Empathy: The ability to share in another’s emotions or feelings.
Emulsion: The gelatinous coating on radiographic film containing
silver halide crystals.
Enamel: One of the four basic tooth structures. The dense, hard substance that covers the dentin of the crown of the teeth. Appears very
radiopaque on the radiograph.
Endodontic therapy: The treatment of the tooth by removing the
nerves and tissues of the pulp cavity and replacing them with filling
material.
Energy: The ability to do work and overcome resistance.
Energy levels (electron shells or orbits): A term used in chemistry and physics to denote spherical levels containing the electrons
of the atom.
Ethics: A sense of moral obligation regarding right and wrong behavior.
Exfoliation: Shedding of primary teeth.
Exostosis: A bony growth projecting outward from the surface of a
bone or tooth. Occasionally encountered on the palate or the lingual surface of the mandible as tori.
Exposure: A measure of ionization produced in air by x- or gamma
radiation. The units of exposure are coulombs per kilogram (C/kg)
and the roentgen (R).
Exposure button: Keypad or switch that activates the x-ray production process.
Exposure chart: A chart listing the exposure factors (milliamperage,
exposure time, and kilovoltage) for each radiographic procedure.
Exposure factors: Settings for milliamperage (mA), exposure time,
and kilovoltage (kVp).
Exposure time: The time interval, expressed in seconds or impulses,
that x-rays are produced.
Extension arm: Flexible arm from which the tube head of the x-ray
machine is suspended.
External aiming device (indicator ring): An indicating component of some image receptor holders that is used to aid in aligning
the x-ray beam to the image receptor.
External auditory meatus (foramen): An opening in the temporal bone located superior and anterior to the mastoid process.
External resorption: Tooth structure lost through a resorptive
process. Characterized by tooth roots that appear shorter than
normal, but can also occur anywhere along the tooth root. Resorption
of the roots of primary teeth in response to the erupting permanent
teeth is considered normal. Pathologic external resorption may be
associated with an impacted or unerupted tooth, a tumor, or trauma.
Often the cause is idiopathic (unknown).
Extraoral film: Designed for use outside the mouth.
Extraoral radiography: Radiographic examinations made of the head
and facial region using image receptors positioned outside the mouth.
Extraoral film requires the use of a cassette and intensifying screens.
Eyewash station: Sink with faucets designed for the purpose of
flushing the eyes with copious amounts of water in an accidental
chemical contamination.
FAQs: Stands for frequently asked questions.
Federal Performance Act of 1974: Requires that all x-ray equipment manufactured or sold in the United States meet federal performance standards.
Filament: The spiral tungsten coil in the focusing cup of the cathode
of the x-ray tube.
Film badge: A monitoring device containing a special type of film
which, when properly developed and interpreted, gives a measurement of the exposure received during the time the badge was worn.
Film contrast: See Contrast.
Film duplicator: A device that provides a diffused light source (usually ultraviolet) that evenly exposes the duplicating film.
Film feed slot: Opening in an automatic film processor where the
film is inserted for processing.
Film fog: An overall darkening of the radiograph caused by old or
contaminated processing solutions, exposure to chemical fumes,
faulty safelight, or scatter radiation.
Film hanger: A stainless steel hanger equipped with clips used to
hold films during manual processing.
Film holder/Image receptor holder: Device used to hold and stabilize an intraoral film packet or digital sensor or phosphor plate in
the mouth.
Film loop (bitewing loop): Cardboard or plastic loop used as an
image receptor holder in bitewing radiography. The patient bites
on the tab portion to hold the image receptor in position during
exposure.
Film mount: Plastic or cardboard holder with frames or windows
that display films for viewing.
Film mounting: The placement of dental radiographs in a film
mount for viewing and interpretation.
Film packet: Intraoral film packaged in a moisture-proof outer plastic or paper wrap. May contain one or two films, wrapped in dark
protective paper on either side, and a thin sheet of lead foil on the
back side of the film(s).
Film recovery slot: Opening in an automatic film processing unit
where the finished radiograph exits at the completion of the processing cycle.
Film speed: The sensitivity of the film to radiation exposure. Fastfilm speed requires less radiation to produce an image. Slow film
speed requires more radiation to produce an image.
Filter: Absorbing material, usually aluminum, placed in the path of
the beam of radiation to remove a high percentage of the low
energy (longer wavelength) x-rays.
412 GLOSSARY
Filtration: The use of absorbers for selectively absorbing or screening
out low-energy x-rays from the primary beam. See Added filtration,
Inherent filtration, and Total filtration.
Fixer: A solution of chemicals that stops the action of the developer
and makes the image permanently visible.
Fixing agent: Sodium thiosulfate, also known as “hypo” or hyposulfite of sodium. It is one of several chemical ingredients in the fixer
solution and functions to remove all unexposed and any remaining
undeveloped silver bromide grains from the emulsion.
Focal spot: Small area on the target on the anode toward which the
electrons from the focusing cup of the cathode are directed. X-rays
originate at the focal spot.
Focal trough: That area between the x-ray source and the image
receptor that will be imaged distinctly on the panoramic radiograph. The size and shape of the focal trough vary with each
panoramic x-ray machine.
Focusing cup: A curved device around the cathode wire filament
that is designed to focus the free electrons toward the tungsten target of the anode.
Follicular (eruptive) cyst: A cyst associated with the enamel follicle.
Foreign body: Any object or material not normally found in the area.
Foreshortened image: Distortion of the radiographic image in
which the tooth structures appear shorter than their actual anatomical size. Most often caused by excessive vertical angulation of the
central beam.
Foreshortening: See Foreshortened image.
Fracture line: A break in a bone or a tooth. Appears radiolucent
radiographically.
Frankfort plane: An imaginary plane or line from the orbital ridge
(under the eye) to the acoustic meatus of the ear.
Frequency: The number of crests of a wavelength passing a given
point per second.
Fresh film test: Quality control test used to monitor the quality of
each new box of film.
Frontal bone: Cranial bone that forms the forehead.
Full mouth series (survey): The complete radiographic examination of the arches in which all teeth are imaged at least once, usually
consists of 14 to 22 periapical and bitewing radiographs.
Furcation involvement: Bone loss between the roots of multirooted teeth.
Fusion: A condition where the dentin and one other dental tissue of
adjacent teeth are united.
Gag reflex: A protective mechanism that serves to clear the airway
of obstruction.
Gamma rays: A form of electromagnetic radiation with properties
identical to x-rays. Usually produced spontaneously in the form of
emission from radioactive substances.
Gelatin: Component of the film emulsion in which the halide crystals are suspended.
Gemination: A single tooth bud that divides and forms two teeth.
General radiation: Also called bremsstrahlung (which means
“braking” in German) radiation. The stopping or slowing of the
electrons of the cathode stream as they collide with the nuclei of
the target atoms.
Generalized bone loss: Bone loss that occurs throughout the dental
arches.
Genetic cells: The cells contained within the testes and ovaries, containing the genes.
Genetic effect: Radiation effect that is passed on to future generations.
Genetic mutation: Change in the genetic material of a cell that
passes from one generation to another.
Genial tubercles: Anatomical landmark situated near the midline
on the lingual surface of the mandible about halfway between the
alveolar crest and the inferior border of the mandible. Appear radiographically as a small doughnut-shaped, radiopaque ring. The
lingual foramen is located in the center of this ring.
Geometric factors: Factors that relate to the relationships of angles,
lines, points, or surfaces that contribute to the quality of radiographic
image definition.
Ghost image: Mirror or second image of a structure that is penetrated twice by the x-ray beam observed on panoramic radiographs.
Gingivitis: Inflammation of the gingiva.
Globulomaxillary cyst: Type of nonodontogenic cyst arising between
the maxillary lateral incisor and the canine.
Glossopharyngeal air space: Open space posterior to the tongue
that continues into the oral-pharyngeal (throat) region. Appears as
a radiolucent negative shadow on a panoramic radiograph.
Granuloma: A tumor or neoplasm made up of granulation tissue.
Often follows an abscess. Usually round or oval and surrounded by
a fibrous capsule. Appears radiolucent on a radiograph.
Gray (Gy): Système Internationale unit for measuring absorbed dose.
One Gy equals 100 rads; 1,000 milligrays equals 1 Gy.
Gray scale: Refers to the total number of shades of gray visible in an
image.
Gray value: Number that corresponds to the amount of radiation
received by a pixel within a digital sensor. The computer uses this
value to determine the shade of gray displayed on the computer
monitor.
Grid: A device used in extraoral radiography to prevent scatter radiation from fogging the image.
Gutta percha: Endodontic filling material.
Halide: Part of a halogen compound such as bromine and iodine that
together with silver make up radiographic film emulsion.
Half-value layer (HVL): Thickness of a specified material that,
when introduced into the path of a given beam of radiation, reduces
the exposure rate by half.
Hamulus (hamular process): A very small hooklike process of bone
that extends downward and slightly backward from the sphenoid
bone. Appears radiopaque and can occasionally be seen posterior to
the maxillary tuberosity.
Hard radiation: Rays of high energy and extremely short wavelengths. Essential for dental radiography.
Hardening agent (hardener): Potassium alum, one of the chemicals of the fixing solution. Functions to shrink and harden the wet
emulsion.
Hazardous waste: Waste materials that present a threat to community health or the environment.
Head positioner guides: Device used on panoramic and cephalometric x-ray machines to stabilize the patient’s head in the correct
position.
GLOSSARY 413
Health Insurance Portability and Accountability Act of 1996
(HIPAA): Federal law designed to provide patients with more
control over how their personal health information is used and disclosed. A patient will usually be asked to sign a notice that indicates how their radiographs may be used and their privacy rights
under this law.
Hemostat: A clamplike dental instrumental. Can be used as forceps
to grasp a film packet.
Hepatitis B (HBV): Form of viral hepatitis. May be transferred
between patient and oral health care professionals via contact with
blood. Hepatitis B vaccine in a series of three doses is recommended to achieve immunity.
Herringbone error (also called tire-track pattern): Image produced on a radiograph when the film packet is placed in the mouth
backwards. The embossed pattern in the lead foil produces this
image when the x-ray beam passes through the reversed film
packet.
HIV: See Human immunodeficiency virus.
Horizontal angulation: Direction of the central beam in a horizontal plane. Incorrect horizontal angulation results in overlapping the
proximal structures.
Horizontal bitewing radiograph: Bitewing radiograph placed in
the oral cavity with the long dimension of the image receptor positioned horizontally. Considered the traditional placement for most
patients.
Horizontal bone loss: Bone loss that occurs in a plane parallel to
the cementoenamel junctions of adjacent teeth.
Human immunodeficiency virus (HIV): A type of retrovirus that
causes AIDS (acquired immunodeficiency syndrome).
Hydroquinone: Reduces (converts) exposed silver halide crystals to
black metallic silver. Slowly builds up black tones and contrast.
Hypercementosis: An excessive development of cementum that
makes the tooth root appear bulbous. Most frequently observed on
premolars. Appears radiopaque.
Hypersensitive gag reflex: Exaggerated gag response that is overly
sensitive.
Identification dot: Small circular embossed mark on the corner of
intraoral x-ray film. Used to determine the patient’s right or left
side when viewing radiographs.
Idiopathic resorption: Of unknown original. See External resorption and Internal resorption.
Image receptor holder (positioner): See film holder.
Immunization: Method, such as vaccines, of inducing resistance to
an infectious disease.
Impacted tooth (impaction): A tooth embedded in alveolar bone
in such a manner that its eruption is prevented. An impaction may
be partial or total.
Impulse: Measure of exposure time. There are 60 impulses per second.
Incandescence: Stage when the tungsten filament in the cathode
becomes red hot and glows. Free electrons are liberated and swarm
around the glowing wire to form the electron cloud.
Incipient (enamel) caries: The earliest stage of the caries process.
Incisive canal cyst: A type of nonodontogenic cyst arising in the
incisive canal.
Incisive (anterior palatine) foramen: Maxillary landmark situated at the midline of the palate immediately behind the central
incisors from which the nasopalatine nerve and vessels emerge.
Shape varies but is usually observed as a round pea-shaped radiolucency. Incorrect horizontal angulation superimposes the incisive
foramen over the apex of the root of the central incisor where it
may then be mistaken for an abscess or a cyst.
Indicator ring: See External aiming device.
Indirect digital imaging: Photostimuable phosphor (PSP) plate
sensor technology. Method of obtaining a digital image in which an
exposed phosphor plate is placed into a scanner and then converted
into a digital image.
Indirect theory: States that cell damage results indirectly when
x-rays cause the formation of toxins in the cell such as hydrogen
peroxide. Toxins in turn cause the cell damage.
Infection control: The prevention and reduction of disease-causing
(pathogenic) microorganisms.
Inferior border of the mandible: Dense layer of cortical bone
that forms the lower portion of the body of the mandible. Appears
very radiopaque on the radiograph.
Informed consent: Permission given by a patient after being
informed of the details of a treatment procedure.
Inherent filtration: Filtration built into the x-ray machine by the
manufacturer. This includes the glass x-ray tube envelope, the insulating materials of the tube head, and the materials that seal the port.
Intensifying screen: Plastic sheet coated with calcium tungstate or
rare earth fluorescent salt crystals. Positioned in a cassette. When
exposed to radiation, the fluorescent salts glow, giving off a blue
(calcium tungstate) or green (rare earth) light. Produces a latent
image faster than is possible when radiation alone is used.
Intensity: The total energy of the x-ray beam. The product of the
number of x-rays (quantity) and energy of each x-ray (quality) per
unit of area per time of exposure.
Interdental septa: Alveolar bone between adjacent teeth.
Internal resorption: Tooth structure lost through a resorptive
process. Typically appears as a radiolucent widening of the root
canal, representing the resorption process taking place from the
inside out. Often the cause is idiopathic (unknown).
Interpersonal skills: Techniques that increase successful communication with others.
Interpretation: The ability to read and explain what is revealed by
the radiograph.
Interproximal: Between two adjacent tooth surfaces.
Interproximal caries: See Proximal caries
Interproximal radiograph: See Bitewing radiograph.
Intraoral: Inside the mouth.
Intraoral dental film: Film that is placed in the oral cavity for
exposure.
Intraoral film: See Intraoral dental film.
Intraoral radiography: Radiographic examinations where the image
receptor is placed inside the mouth.
Inverse square law: States that the intensity of radiation is inversely
proportional to the square of the distance from the source of the
radiation to the point of measurement.
414 GLOSSARY
Inverted Y: Radiographic landmark made up of the lateral wall of
the nasal fossa and the anterior-medial wall of the maxillary sinus
often observed near the canine-premolar region.
Ion: An electrically charged particle, either negative or positive.
Ion pair: A pair of ions, one positive and one negative.
Ionization: The formation of ion pairs.
Ionizing radiation: Radiation that is capable of producing ions.
Irradiation: The exposure of an object or a person to radiation. Term
can be applied to radiations of various wavelengths, such as
infrared rays, ultraviolet rays, x-rays, and gamma rays.
Irreparable injury: Following exposure to radiation, injury that
results in damage that is not repaired during the recovery period.
May give rise to later long-term effects of radiation exposure.
Isosceles triangle: A triangle with two sides equal in length and
two identical angles opposite these two equal sides.
Isotope: Alternate form of an element, having the same number of
protons but a different number of neutrons inside the nucleus.
Many isotopes are radioactive.
Kilovolt (kV): A unit of electromotive force, equal to l,000 volts.
High kilovoltage is essential for the production of dental x-rays.
Kilovolt peak (kVp): The crest value in kilovolts of the potential
difference of a pulsating generator.
Kinetic energy: Energy possessed by a mass because of its motion.
Labial mounting method: Radiographs mounted so that the embossed dot is convex. The viewer is reading the radiograph as if
standing in front of, and facing, the patient. Recommended by the
American Dental Association and the American Academy of Oral
and Maxillofacial Radiology over the lingual mounting method.
Lamina dura: A thin, hard layer of cortical bone that lines the dental
alveolus. Appears as a thin, radiopaque line around the roots of the
teeth on dental radiographs.
Latent image: The invisible image produced when the film is exposed
to x-ray photons. Image remains invisible until the film is processed.
Latent period: The time between exposure to radiation and the first
clinically observable symptoms. Latent means hidden.
Lateral cephalometric radiograph: Extraoral radiograph of the
side of the skull often used by orthodontists at various stages of
treatment. Made by placing the patient’s head in a cephalostat.
Also called a lateral skull projection.
Lateral fossa: Slight decreased thickness (concavity) in bone between
the maxillary lateral incisor and the maxillary canine.
Lateral jaw (mandibular oblique lateral) radiograph: Extraoral
radiograph of the posterior mandible. Also called mandibular
oblique lateral projection.
Lateral skull projection: See Lateral cephalometric radiograph.
Law of B and T (Bergonie and Tribondeau): States that the
radiosensitivity of cells and tissues is directly proportional to their
reproductive capacity and inversely proportional to their degree of
differentiation.
Lead apron: Protective barrier made of lead or lead-equivalent materials. Shields patients’ gonadal areas from radiation during dental x-ray
exposures.
Lead equivalent: The thickness of a material that affords the same
degree of attenuation (absorption) to radiation as a specified thickness of lead.
LED (light-emitting diode): A semiconductor device that emits
light when electrical current passes through it. Used for safelighting the darkroom.
Lethal dose: The amount of radiation that is sufficient to cause the
death of an organism.
Liable: To be legally obligated to make good any loss or damage that
may occur.
Light-tight: Securing an area against all sources of white light.
Characteristic of a darkroom.
Line pair: Refers to the number of paired lines visible in 1 mm of an
image. The more line pairs visible, the better the spatial resolution
in an image.
Line switch: Toggle switch that is used to turn the x-ray machine on
or off.
Lingual caries: Caries that involves the lingual surface of a tooth.
Lingual foramen: A very small opening through which a branch of
the incisive artery emerges. Located in the center of the genial
tubercles on the lingual side of the mandible. See Genial tubercles.
Lingual mounting method: Radiographs are mounted so that the
embossed dot is concave. The viewer is reading the radiograph as if
standing behind the patient.
Local contributing factor: Amalgam overhangs, poorly contoured
crown margins, and calculus deposits that act as food traps and lead
to the buildup of bacterial deposits that cause periodontal disease.
Localization: Methods to provide a third dimension to two-dimensional
radiographs. Assists the radiographer in determining whether an
object is located on the facial (buccal) or lingual.
Localized bone loss: Bone loss that occurs in isolated areas.
Long-scale contrast: Low-contrast image. A radiographic image
with many shades of gray. Produced with high kilovoltage.
Mach band effect: An optical illusion that mimics the appearance
of decay. Often occurs along boundaries of sharp contrast, especially around areas of slight overlapping between adjacent teeth.
Magnification (enlargement): Enlargement of the structures
imaged on a radiograph over the actual size. Enlargement is greatest when the target of an x-ray machine is closer to the structures
of interest and is decreased when distance is greater.
Malignant: Tendency to progress in virulence and spread. Condition
that may result in death.
Malpractice: Improper practice. Malpractice results when one is
negligent.
Mandible: Lower arch (jaw).
Mandibular canal: Long canal extending from the mandibular
foramen on the medial aspect of the ramus of the mandible to the
mental foramen on the lateral aspect. Carries nerves and blood
vessels that supply most of the teeth in the mandible. Appears
radiolucent, with thin radiopaque lines above and below outlining
the cortical bone that lines the canal.
Mandibular foramen: Small opening on the lateral side of the body
of the mandible. Usually observed near the apices of the premolars.
Mandibular notch: Notch between the condyle and coronoid
process of the mandible. Also called the sigmoid notch.
Mandibular oblique lateral projection: See Lateral jaw projection.
Mastoid process: Large rounded protuberance of the temporal bone
located behind the ear.
GLOSSARY 415
Material Safety and Data sheets (MSDS): Documentation available from the manufacturers of chemical products that provide the
oral health care professional with information regarding the properties and the potential health effects of the product.
Maxilla: Upper arch. The maxillae are actually two bones, a right
and left maxilla.
Maxillary sinus: Large radiolucent cavity observed within the maxilla apical to the maxillary posterior teeth.
Maxillary tuberosity: A radiopaque prominence of bone on the
distal portion of the maxillary alveolar ridge.
Maxillofacial: Pertaining to the dental arches (maxilla and mandible)
and other supporting facial structures of the head and neck region.
Maximum permissible dose (MPD): The maximum accumulated
dose that persons who are occupationally exposed may have at any
given time of their life. It is the dose of ionizing radiation that, in
the light of present knowledge, is not expected to cause detectable
body damage. Currently established at 0.05 Sv per year (5 rem/year)
whole body.
Mean tangent: Average point where several curved surfaces touch
if a ruler is held against them. The labial or buccal surfaces of all
teeth have their most prominent point toward the lips or the cheeks
and curve toward the mesial or distal. A mean tangent would be
established by using a small ruler or any straight edge (such as a
tongue depressor) and attempting to align as many of the teeth as
possible. Occasionally, four or even five of the posterior teeth will
touch the ruler at some point. Used to establish correct horizontal
angulation, which requires that the central ray of the x-ray beam be
directed at right angles to the mean tangent.
Median palatine suture: An irregular line formed by the junction
of the palatine processes of the right and left maxillae. Appears as a
thin radiolucent line running vertically between the roots of the
maxillary incisors.
Mental foramen: An opening through which the mental nerve and
related blood vessels emerge on the lateral aspect of the body of the
mandible; exact location varies. When imaged on radiographs,
appears as a small round radiolucent area near the roots of the
mandibular premolars. Should not be mistaken for an abscess, cyst,
or other pathological condition.
Mental fossa: A depression on the labial aspect of the mandibular
incisor area.
Mental ridge: Raised ridge of bone located in the anterior region on
the lateral surface of the mandible.
Mesiodens: A supernumerary tooth located in the maxillary midline.
Mesiodistal overlap: When the projection angle of the x-ray beam
is directed from mesial to distal resulting in overlapping error.
Microbial aerosol: Suspension of microorganisms that may be
capable of causing disease produced during normal breathing
and speaking
Microsievert One millionth of a seivert. See Seivert.
Midsagittal plane (midsagittal line): An imaginary vertical line
or plane passing through the center of the body that divides it into a
right and left half. Important orientation line in determining the
ideal position of the patient’s head during radiographic exposures.
Milliampere (mA): One thousandth of an ampere. Milliamperage
determines the number of electrons available at the filament. See
Ampere.
1mSv2:
Milliampere second (mAs): The relationship between the milliamperage and the exposure time in seconds. When one is
increased, the other must be correspondingly decreased to maintain
film density.
Modeling: Technique used to orient patients, especially children,
to the radiographic procedure. Child is given the opportunity to
observe procedure being performed on another, such as a sibling
or parent. May help to alleviate fear of the unknown and gain
patient cooperation.
Moderate caries: A classification of proximal surface caries. Category where caries penetrate over halfway through the enamel
toward the dentinoenamel junction (DEJ), but do not reach the DEJ.
Molecule: Chemical combination of two or more atoms that forms
the smallest particle of a substance that retains the properties of
that substance.
Monitoring: Use of any of several devices to determine whether an
area is within safe radiation limits or whether a person’s exposure
is within permissible limits. See Area monitoring and Personnel
monitoring.
Motion: Movement of the image receptor, patient, or tube head during radiographic exposure that results in a less sharp image.
MPD: See Maximum permissible dose.
Mylohyoid ridge: Raised ridge of bone running diagonally downward and forward on the medial aspect of the ramus of the
mandible to near the apices of the molar roots. Parallels the (external) oblique ridge, but on the lingual surface and about 1/4 in (6
mm) lower. Appears radiopaque when observed on a radiograph.
Nasal bones: Bones that make up the upper bridge of the nose.
Nasal conchae: Thin bony extensions of the nasal wall.
Nasal fossa (cavity): Large air space divided into two paired radiolucencies by the radiopaque nasal septum. Visible above the roots
of the maxillary incisors.
Nasal septum: Dense cartilage that separates the right nasal fossa
from the left. Appears as a vertical radiopaque line separating the
paired radiolucencies of the nasal cavity
Nasopharyngeal air space: Open space superior to the soft palate.
Appears as a radiolucent negative shadow on a panoramic radiograph.
Negative angulation (negative vertical angulation): Achieved
by pointing the tip or end of the PID upward from a horizontal
plane.
Negative shadows: Term given to the radiolucencies produced on
a panoramic radiograph as a result of more radiation reaching the
image receptor in the areas of air spaces. Negative shadows are
shadows of “nothing.”
Negligence: Failure to use a reasonable amount of care that results
in injury or damage to another.
Neoprene gloves: Synthetic rubber utility gloves that provide
increased protection for handling potentially damaging or hazardous chemicals.
Neutron: One form of particulate (corpuscular) radiation or subatomic particle. A neutron has no electric charge and has about the
same mass as a proton.
Nitrile gloves: Synthetic latex utility gloves that provide increased
protection for handling potentially damaging or hazardous chemicals
Noise: See Electronic noise
416 GLOSSARY
Nonmetallic restoration: Restoration containing no metal. May
appear radiolucent, or radiopaque when radiopaque fillers have
been added to the restorative material.
Nonodontogenic cyst: Cyst that arises from epithelium other than
that associated with tooth formation.
Nonthreshold dose response curve: A graph showing the relationship between the dose of exposure and the response of the tissues, indicating that any amount of radiation, no matter how small,
has the potential to cause a biological response.
Nonverbal communication: Communication achieved without
words. Includes gestures, facial expressions, body movement, and
listening.
Nutrient canal: Small tubelike passageway through bone that contains blood vessels and nerves. Appears radiolucent in radiographs.
Nutrient foramen: Occasionally imaged on a radiograph as a tiny
radiolucent dot indicating the small opening in the tubelike passageway of a nutrient canal.
Object-image receptor distance: Distance between the object
being recorded and the image receptor.
Oblique ridge: Diagonal ridge of bone on the lateral aspect of the
mandible that runs downward and forward from the anterior border
of the ramus to the level of the cervical portion of the molar and
premolar roots. Sometimes referred to as the external oblique
ridge. The internal oblique ridge appears faintly parallel to the
external oblique ridge. The internal oblique ridge is not identified
as an anatomical structure, but as a landmark only.
Occipital bone: Forms the posterior part of the skull.
Occlusal caries: Caries found on the occlusal (chewing) surface of
posterior teeth.
Occlusal plane: Plane between the maxillary and the mandibular teeth.
Occlusal radiograph: Radiograph produced by placing the image
receptor against the incisal or occlusal plane. The patient stabilizes
the image receptor by biting down on it. In addition to the teeth,
occlusal radiographs may show surrounding maxillary or mandibular
structures. Depending on the placement of the image receptor and
angle of exposure, cross-sectional or topographic radiographs are produced. See Cross-sectional technique and Topographical technique.
Occlusal trauma: Excessive or repetitive force against the teeth that
results in a response.
Occult disease: The presence of disease that is not apparent clinically,
but can only be detected via a diagnostic test, such as a radiograph.
Odontogenic cyst: A cyst that arises from epithelial cells associated with the development of a tooth.
Odontoma: A tumor of odontogenic origin in which enamel and
dentin are formed. May contain soft tissues that appear radiolucent
and a hard calcified mass, sometimes resembling a tooth, which
appears radiopaque. Compound odontoma refers to odontogenic
tissues that resemble teeth. Complex odontoma denotes odontogenic tissues arranged in a haphazard manner with no resemblance
to tooth formation. Compound-complex odontoma is a mixture of
the two types.
Oral radiography: Procedures that pertain to producing radiographs of the teeth and/or the oral cavity.
OSL (optically stimulated luminescence) monitor: A personnel radiation monitor that absorbs radiation similar to TLD, but
crystals release energy during optical stimulation instead of heat.
Ossification: The pathological or abnormal conversion of soft tissues into bone.
Osteosclerosis: Abnormal increase in bone density. Appears as in
increased radiopacity on a radiograph.
Overdevelopment: Leaving the film in the developer solution too
long or using developer that is too warm. Overdevelopment results
in a dark image.
Overexposure: Exposing the image receptor too long or subjecting
the image receptor to an inappropriately increased kVp or mA setting. Overexposure results in a dark image.
Overhang: A restoration that is not contoured to the tooth properly.
Overlap: Term used to refer to a distortion of the tooth image in
which the structures of one tooth are superimposed over the structures of the adjacent tooth. Caused by incorrect horizontal angulation of the central beam and/or incorrect positioning of the image
receptor in relationship to the teeth of interest.
Oxidation: The process during which the chemicals of the developing
and fixing solutions combine with oxygen and lose their strength.
Palatoglossal air space: Open space between the tongue and palate.
Appears as a radiolucent negative shadow on a panoramic radiograph.
Panoramic radiograph: Generic term pertaining to the radiographic
image produced by a panoramic x-ray machine. Images all the teeth
and supporting structures of the maxilla and mandible.
Panoramic radiography: Procedure performed with a specialpurpose x-ray machine that uses a stationary patient and a simultaneously moving x-ray source and image receptor to produce an
image of the entire dentition and surrounding structures.
Paralleling technique: Intraoral technique that places the image
receptor positioned parallel to the long axes of the teeth while the
central beam of radiation is directed perpendicularly (at right
angles) toward both the teeth and the image receptor.
Particulate radiation (corpuscular radiation): Minute subatomic
particles such as protons, electrons, and neutrons; also alpha and
beta particles. These particles occupy space; have mass and weight;
and, with the exception of neutrons, have an electrical charge.
Pathogen: A disease-causing microorganism.
Patient education: Informing patients about the benefits of oral
health and preventive oral hygiene. Providing the patient with necessary information that explains the value of dental radiographs and
demonstrates radiation safety measures employed in the practice.
Patient relations: Establishment of the relationship between the
patient and the oral health care professional.
Pediatric dentistry: Branch of dentistry that specializes in providing comprehensive preventive and therapeutic oral health care for
children.
Pedodontic image receptor: Any smaller-sized film packet, phosphor plate, or digital sensor used for radiographs of children’s teeth.
Penumbra: Partial shadow or fuzzy outline around the image.
Periapical cemental dysplasia (PCD): Sometimes referred to as
cementoma. A tumor derived from the periodontal ligament of a
fully developed and erupted tooth, usually a mandibular incisor.
Early PCD is radiolucent and appears identical to radicular cysts.
In the later stages of development, calcification occurs that appears
as radiopaque masses surrounded by a radiolucent line. The teeth
are vital and need no treatment.
GLOSSARY 417
Periapical radiograph: Image that shows the entire tooth or teeth
and surrounding tissues. Peri means “around” and apical is the root
end of the tooth.
Period of injury: Radiation-induced changes that follow the latent
period.
Periodontal diseases: Diseases that affect the supporting tissues of
the teeth.
Periodontal ligament (PDL) space: The space between the root of
a tooth and the lamina dura where the thin but dense and strong
fibrous tissues of the periodontal ligament are located. Radiographically, the periodontal ligament appears as a thin radiolucent line
between the lamina dura and the root.
Periodontitis: Inflammation of the periodontium.
Periodontium: Tissues that invest and support the teeth (gingiva and
alveolar bone).
Permanent teeth: Teeth that erupt after the primary teeth have been
exfoliated (shed). Consists of 32 teeth—8 incisors, 4 canines, 8 premolars, and 12 molars.
Personal protective equipment (PPE): Clothing, masks, eyewear,
and gloves worn by dental personnel as a protective barrier that prevents the transmission of infective microorganisms between oral
health care practitioners and patients.
Personnel monitoring: The occasional or routine measuring of the
amount of radiation to which a person working around radiation
has been exposed during a given period of time.
Personnel monitoring device: Device (film badge, thermoluminescent dosimeter [TLD], direct ion storage [DIS] dosimeter and optically
stimulated luminescent [OSL] dosimeter) worn by a radiation worker
to measure the amount of radiation received in a given period of time.
pH: Chemical symbol used with a number from 0 to 14 to designate
the relative acidity or alkalinity of a solution. Under 7 is acidic,
over 7 is alkaline, 7 is neutral, neither acidic or alkaline.
Phleboliths: Calcified masses that are observed as round or oval
bodies in the soft tissues of the cheeks.
Phosphors: Fluorescent crystals, calcium tungstate or rare earth,
used in the emulsion that coats intensifying screens. Give off light
when subjected to radiation.
Photoelectric effect: An attenuation process for x- and gamma radiation in which a photon interacts with an orbital electron of an atom.
All of the energy of the photon is absorbed by the displaced electron
in the form of kinetic energy.
Photon (x-ray photon): A quantum of energy. Both x-rays and
gamma rays are photons.
Photostimuable phosphors (PSP): Digital imaging sensors that
use rare earth phosphor (barium europium fluorohalide) coated
plates. When exposed to x-rays, the PSP sensor or plate “stores”
the x-ray energy until stimulated by a laser beam to produce a digital image.
PID: See Position indicating device.
Pixel: Small, discrete units of digital information that together constitute an image. Pixel is a term shortened from the words “picture”
and “element”
Point of entry: Spot on the surface of the face toward which the
central beam of radiation is directed when aligning the PID for
intraoral exposures.
1pix = plural of picture; el = element2.
Polychromatic: A term derived from the Greek meaning “having
many colors.” Used in dental radiography to describe the x-ray
beam because it is composed of many different wavelengths.
Port: Opening in the tube head that is covered with a permanent seal
of glass, beryllium, or aluminum through which the x-rays exit.
The port is opposite the window in the x-ray tube and is the place
where the PID attaches to the tube head.
Position indicating device (PID): Also called beam indicating
device (BID). An open-ended, cylindrical or rectangular device
attached to the tube head at the aperture to direct the useful beam of
radiation. PIDs are available in different lengths.
Positive angulation (positive vertical angulation): Angulation
achieved by pointing the end of the PID downward from a horizontal plane.
Post and core: Metal restorative material used in an endodontically
treated tooth when support for a crown is needed. Appears
radiopaque.
Posteroanterior cephalometric radiograph: Extraoral radiograph
of the entire skull in the posteroanterior plane. Also called a posterioranterior projection (PA).
Posteroanterior projection (PA): See Posterioanterior cephalometric radiograph.
Potassium alum: One of the components of fixer solution. Shrinks
and hardens the gelatin emulsion.
Potassium bromide: Restrains the developing agents from developing the unexposed silver halide crystals.
PPE: See Personal protective equipment.
Preservative: One of the chemicals (sodium sulfite) used in both the
developer and fixer solutions to slow down the rate of oxidation
and prevent spoilage of the solution.
Primary beam (primary radiation or useful beam): The original undeflected useful beam of radiation that emanates at the focal
spot of the x-ray tube and emerges through the aperture of the tube
head.
Primary teeth: Teeth that fall out or are exfoliated naturally. Consists of 20 teeth—8 incisors, 4 canines, and 8 molars.
Processing: The act of bringing out the latent image and making it
permanently visible. Includes the following darkroom procedures:
developing, rinsing, fixing, washing, and drying.
Processing tank: Stainless steel receptacle divided into compartments for developer solution, water rinse, and fixer solution. Used
to process radiographs.
Protective barrier: Shield of radiation-absorbing material used to
protect against radiation exposure.
Proton: A subatomic particle of the atom. The proton is contained in
the nucleus and has a positive electrical charge. The proton has mass
and weight. The number of protons determines the chemical element.
Proximal caries: Caries found on the proximal surfaces (mesial and
distal) of teeth.
Proximal surface: Where adjacent teeth contact each other in the
arch. The mesial and distal surfaces are proximal surfaces.
Pterygoid plates: Extensions of the sphenoid bone.
Pulp chamber (cavity): Noncalcified tooth tissue containing blood
vessels and nerves. Appears radiolucent, as this soft tissue offers
only minimal resistance to the passage of x-rays.
418 GLOSSARY
Pulp stone: Calcification that appears in the pulp chamber of the
teeth, caused by an abnormal disposition of calcium salts. Often
described as nodules or denticles. Seen on radiographs as one or
more small radiopaque, irregularly shaped, rounded masses within
the pulp chamber.
Quality: Term used when describing the intensity of the x-ray beam.
Refers to the number of x-rays in the beam.
Quality assurance: The planning, implementation, and evaluation
of procedures used to produce high-quality radiographs with maximum diagnostic information while minimizing radiation exposure.
Quality control: A series of tests to ensure that the radiographic
system is functioning properly and that the radiographs produced
are of an acceptable level of quality.
Quantity: Term used when describing the intensity of the x-ray
beam. Refers to the penetrating ability of the beam.
Rad: Traditional unit for measuring absorbed dose. 100 rads equals
one gray (Gy). One rad equals 0.01 Gy. 1,000 millirads equals 1 rad.
Radiation: The emission and propagation of energy through space
or through a material medium in the form of electromagnetic
waves, corpuscular emissions such as alpha and beta particles, or
rays of mixed and unknown types such as cosmic rays. Most radiations used in dentistry are capable of producing ions directly or
indirectly by interaction with matter.
Radiation leakage: Refers to the x-rays that escape out of the tube
head at places other than the port.
Radiation worker: A radiographer or professional who works with
or around ionizing radiation or equipment that produces ionizing
radiation.
Radiator: A large mass of copper just outside the x-ray tube and
connected to the anode terminal. The radiator functions to carry
off the excess heat produced in the energy exchange that takes
place when the electrons of the cathode stream are converted into
about 1% x-rays and 99% heat. The radiator conducts the heat
away from the target and cools the tube.
Radicular cyst: A cyst around the apex of a tooth. Generally
observed as a small radiolucent circular area that extends away
from the apical portions of the root. The sac of the cyst has a distinct wall or capsule that surrounds it and can be distinguished as a
faint radiopaque thin line.
Radioactivity: The process whereby certain unstable elements
undergo spontaneous disintegration (decay). The process is accompanied by emissions of one or more types of radiation and generally results in the formation of a new isotope.
Radiograph: An image produced on photosensitive film by exposure to x-rays. Developing the film produces a negative image that
can be viewed and interpreted.
Radiographic contrast: See Contrast.
Radiography (roentgenography): The making of radiographs by
exposing and processing x-ray film.
Radiology: That branch of medical science that deals with the use of
radiant energy in the diagnosis and treatment of disease.
Radiolucent: That portion of the radiograph that is dark. Structures
that lack density permit the passage of x-rays with little or no resistance. These structures appear dark on the image.
Radiolysis of water: Ionization can dissociate water within a cell
into hydrogen and hydroxyl radicals that have the potential to
recombine into new chemicals such as hydrogen peroxide. These
new chemicals act as toxins (poisons) to the body, causing cellular
dysfunction. Considered an indirect effect of radiation exposure.
Radiopaque: That portion of the radiograph that appears light.
Dense structures resist the passage of radiation. These structures
appear light on the image.
Radioresistant: Refers to a substance or tissue that is not easily
injured by ionizing radiation.
Radiosensitive: Refers to a substance or tissue that is relatively susceptible to injury by ionizing radiation.
Rampant caries: Severe, unchecked caries that affect multiple teeth.
Ramus: The ascending portion of each end of the mandible.
Rapid (chairside) processing: The use of a chairside darkroom
(a light-tight box with a filter cover) and concentrated and/or
heated developer to quickly process working films, such as those
used during endodontic procedures.
Rare-earth phosphors: Salt crystals, usually lanthanum (La) and
gadolinium (Gd), used to coat intensifying screens. When these
absorb x-rays, they fluoresce and emit energy in the form of green
light.
Recovery period: Period following exposure to radiation, where
some healing can take place.
Recurrent (secondary) caries: Caries that occurs under a restoration or around its margins.
Reference film: A radiograph processed under ideal conditions and
then used to compare periodically subsequent films. Quality control procedure to monitor processing solution quality.
Rem (roentgen equivalent in man): Traditional unit for measuring dose equivalent. Used to compare the biological effects of the
various types of radiation. One rem equals 1 rad times a biological
effect weighting factor. Because the weighting factor for x- and
gamma radiation equals 1, the number of rems is identical to the
absorbed dose in rads for these radiations. 100 rem equals one sievert (Sv); one rem equals 0.01 Sv; 1,000 millirems equal 1 rem.
Replenisher: A superconcentrated solution of developer or fixer that
is added daily, or as indicated, to the developer or fixer in the processing tank to compensate for loss of volume and loss of strength
from oxidation. The act of adding replenisher to the processing
solutions is known as replenishment.
Residual cyst: Cyst that remains in the jaw after the tooth that
caused it to form is extracted or exfoliated. May remain within the
bone, becoming encapsulated with an epithelial lining, or may
undergo considerable growth. Appears radiolucent, and the lining
of the cyst appears as a thin radiopaque line.
Resorption: Refers to a loss of bone or tooth structure. May originate
from natural causes such as the gradual reduction of size of the roots
of primary teeth, or may be idiopathic (the result of unknown causes).
Restrainer: Potassium bromide in the developer solution that slows
down the action of the elon and hydroquinone and inhibits the tendency of the solution to chemically fog the films.
Retained root: Root remaining after the tooth has been extracted.
Retake radiograph: A radiograph that has been taken after the first
image is deemed undiagnostic.
Retention pin: Metal pin used to support a restoration.
Reverse Towne radiograph: Extraoral projection used to view the
condylar neck of the mandible. Also called open mouth projection.
GLOSSARY 419
Rhinoliths: Calcifications within the maxillary sinuses.
Risk: The chance or likelihood of adverse effects or death resulting
from exposure to a hazard.
Risk management: Policies and procedures to be followed by the
radiographer to reduce the chances that a patient will file legal
action against the dentist and oral health care team.
Roentgen (R): Traditional unit measurement of exposure to radiation. Measured in air. A simplified definition of the roentgen is the
amount of x-radiation or gamma radiation required to ionize 1 cc of
air at standard conditions of pressure and temperature (2.083 billion ion pairs).
Roentgen ray: See X-ray.
Roentgenograph: See Radiograph.
Roller transport system: Moves films through the developer, fixer,
water, and drying compartments of an automatic processor. Motordriven gears or belts propel the roller transport system.
Root canal treatment: See Endodontic therapy.
Root surface caries: See Cemental caries.
Rotational center: The axis on which the panoramic tube head and
the drum rotate. Based on tomographic radiography principles.
Rule of isometry: Geometric theorem stating that two triangles with
two equal angles and a common side are equal (isosceles) triangles.
This theorem is the basis of the bisecting technique.
Safelight: Special filtered light that can be left on in the darkroom
while films are processed.
Safelight filter: Removes short wavelengths in the blue-green region
of visible light. The longer wavelength red-orange light is allowed
to pass through the filter, illuminating the darkroom without fogging the film.
Sarcoma: Malignant tumor of connective tissue origin.
Scatter radiation: Radiation that has been deflected from its path
by impact during its passage through matter. This form of secondary radiation is scattered in all directions by the tissues of the
patient’s head.
Sclerotic bone: A hardening of the bone as a result of inflammation
or excessive growth of fibrous tissue and deposition of mineral
salts. See Condensing osteitis.
Screen film: Extraoral film for use in cassettes with intensifying
screens. Emulsion is more sensitive to green, blue, and violet light,
emitted when the radiation strikes the phosphors in the intensifying
screens than to the x-radiation.
Secondary radiation: Given off by any matter irradiated with x-rays.
Created at the instant the primary beam interacts with matter and
gives off some of its energy, forming new and less powerful wavelengths. Often referred to as scatter radiation.
Selection criteria: Guidelines developed by an expert panel of health
care professionals to assist in deciding when, what type, and how
many radiographs should be taken.
Selective reduction: Chemical change that takes place within the
film emulsion during development. During this change, the nonmetallic elements are separated from the silver halide of the
exposed crystals, leaving a coating of metallic silver on the film
emulsion while the bromide is removed. The process is called
selective because the unexposed grains are not reduced.
Self-determination: The legal right of an individual to make choices
concerning health care treatment.
Sensor: For use in digital imaging. An electronic or specially coated
plate that is sensitive to x-rays. Placed intraorally to capture a radiographic image when exposed to x-rays.
Sepsis: Infection, or the presence of septic matter.
Septum: Thin wall of bone that acts as a partition to separate the
nasal cavity or the maxillary sinuses. Appears radiopaque.
Severe caries: A classification of proximal surface caries. Category
where caries has penetrated over halfway through the dentin toward
the pulp.
Shadow casting: Principle that x-rays cast shadows of images onto
the image receptor, producing a radiographic image of the teeth
and supporting structures.
Sharpness (See Definition): The distinct outlines of structures
observed on a radiograph.
Short-scale contrast: High-contrast image. A radiograph that exhibits
black and white with few shades. Produced with low kilovoltage.
“Show-tell-do”: Technique used to orient the patient, especially
children, to the radiographic procedure. Showing the radiographic
equipment—image receptor and holder, x-ray machine—to the
patient while explaining their use may help to alleviate fear of the
unknown and gain patient cooperation.
Sialolith: A salivary calculus or hardened, stonelike mass that forms
within the passage of the salivary ducts. If sufficiently large, such
masses appear slightly radiopaque on the radiograph.
Sievert (Sv): Système Internationale unit for measuring the dose
equivalent. The sievert is used to compare the biological effects of
various types of radiation. One sievert equals one gray times a biological effect weighting (qualifying) factor. Because the weighting
factor for x- and gamma radiation equals 1, the number of sieverts
is identical to the absorbed dose in grays for these radiations. One
sievert equals 100 rem. See Microsievert.
Silver halide crystals: Compounds of a halogen (either bromine or
iodine) with silver. Dental film emulsion is approximately 90 to 99
percent silver bromide and 1 to 10 percent silver iodide. Silver
halide crystals are sensitive to radiation. It is the silver halide crystals that, when exposed to x-rays, retain the latent image.
Silver thiosulphate complex: A very stable compound found in
used fixer of dental radiographic processors following the interaction
of sodium thiosulphate with the silver ions in the emulsion of film.
Silver point: Endodontic filling material.
Sinus projection: See Waters radiograph.
SLOB rule: Stands for same on lingual, opposite on buccal. Used in
localization techniques to determine the facial (buccal) or lingual
position of objects. The tube shift method of localization states that
if the structure or object in question appears to move in the same
direction as the horizontal or vertical shift of the tube, then the
structure or object is located on the lingual. Conversely, if the move
is in the opposite direction of the shift of the tube, the object is
located on the buccal (facial).
Sodium carbonate: Provides required alkalinity of the developer
solution to activate developing agents.
Sodium sulfite: Chemical of the developing solution that prevents
rapid oxidation of the developing agents.
Sodium thiosulfate: Chemical of the fixer solution that together
with the ammonium thiosulfate removes the unexposed and any
remaining undeveloped silver halide crystals.
420 GLOSSARY
Soft radiation: Longest wavelength of the x-rays. Removed from
the polychromatic beam by filtration because soft radiation (Grenz
rays) have no value in producing dental radiographs.
Solarized emulsion: Used for duplicating film. Produces a duplicate image that gets lighter the longer the film is exposed to light.
Darker images result from shorter exposure times.
Solid state: Specifically means, no moving parts. Refers to digital
image sensors, usually CCD or CMOS technology.
Somatic cells: Any body cells except the reproductive cells.
Somatic effect: When radiation affects all body cells except the
reproductive cells.
Spatial resolution: The discernable separation of closely adjacent
image details that contributes to image sharpness. The greater the
spatial resolution, the sharper the image appears. When referring to
a digital image, sharpness is determined by the number and size of
pixels and measured in line pairs. When the number of pixels is
low, the image appears to have jagged edges and becomes difficult
to see.
Spatter: A heavier concentration of microbial aerosols such as visible particles from a cough or sneeze.
Speech reading: Method of lip reading used by the hearing impaired.
Sphenoid bone: Cranial bone bordered by the frontal and ethmoid
bones.
Standard precautions: A practice of care to protect persons from
pathogens spread via blood or any other body fluid, excretion, or
secretion (except sweat). All-inclusive term that has replaced universal precautions, where the focus was on blood-borne pathogens.
Static electricity: A white-light spark that creates a radiolucent artifact on the film.
Statute of limitations: Time period during which a person may
bring a malpractice action against another person.
Step-down transformer (low-voltage transformer): Device
consisting of two metal cores and coils so positioned within the circuitry of the tube head to decrease the line voltage to between 3
and 12 volts. Low voltage is required in the cathode to warm up the
filament wire.
Step-up transformer (high-voltage transformer): Device consisting of two metal cores and coils positioned within the circuitry
of the tube head to increase the potential of the line current to the
high kilovoltage required to produce x-radiation.
Step-wedge (penetrometer): A device consisting of increasing
increments of an absorbing material. A radiographic exposure
made with a step-wedge is used to determine the amount of radiation reaching the image receptor through each of the increments.
Measurements of radiographic image density may be used to evaluate the intensity and penetrative power of the radiation.
Sterilize: Aseptic treatment, autoclaving or dry heat processes, that
results in the total destruction of spores and disease-producing
microorganisms.
Stochastic effect: When a biological response is based on the probability of occurrence rather than the severity of the change.
Storage phosphor: Usually composed of europium activated barium fluorohalide, coating on a photostimulable phosphor plate
used in indirect digital imaging. The storage phosphor “stores” the
x-ray energy similar to the way silver halide crystals within film
emulsion store a latent image. A scanning device is used to release
the stored energy to be converted to a radiographic image on a
computer monitor.
Structural shielding: The protection afforded by building materials
found in walls, partitions, and cabinetry, present in most buildings
where dental radiographs are exposed.
Styloid process: Long, narrow spine that extends downward, from
the inferior surface of the temporal bone, just anterior to the mastoid process.
Subject contrast: The difference in densities of a radiographic
image caused by the differing thicknesses of the tissues or objects
penetrated by the x-ray beam.
Submandibular fossa: Irregular depression in the bone near the
angle on the lingual of the mandible. Usually observed radiographically below the roots of the molars and extending forward as far as
the premolar region. Thin and offering little resistance to the passage of the x-rays, it appears radiolucent.
Submentovertex projection: Extraoral projection showing the base
of the skull, the position of the mandibular condyles, and the zygomatic arches. Also called a base projection.
Supernumerary teeth: Extra teeth not normally a part of the dentition. May resemble normal teeth, only smaller with conical
crowns, or bear no resemblance to a normal tooth. Often malpositioned or unerupted.
Suture: A line of union of adjacent cranial or facial bones that
appears radiolucent on radiographs.
Symphysis: Prominent bone where the right and left sides of the
mandible fuse at the midline.
Système Internationale (SI): A metric system of units of that measures radiation quantities. The Système Internationale units are
coulombs per kilogram (C/kg), gray (Gy), and sievert (Sv).
Target: Small block of tungsten imbedded in the face of the anode,
bombarded by the electrons streaming from the cathode. The focal
spot is located on the target.
Target–image receptor distance (source–image receptor distance): Distance between the focal spot on the target and the
recording plane of the image receptor.
Target–object distance (source–object distance): Distance
between the focal spot on the target and the object being radiographed.
Target–surface distance (source–surface distance): Distance
between the focal spot on the target and the skin surface of the
patient.
Taurodontia: Teeth characterized by very large pulp chambers and
very short roots.
Temporal bone: Cranial bone the makes up the temple, or side of
the face. Contains the ear structures, including the auditory meatus.
Temporomandibular disorders (TMD): Term used to describe
the collection of symptoms and diseases that are generally found
involving the temporomandibular joint.
Temporomandibular joint (TMJ): One of two joints connecting
the mandible to the temporal bone.
Temporomandibular joint projection: See Transcranial radiograph.
Thermionic emission: The release of electrons when a material
such as tungsten is heated to incandescence. Electrons are boiled
off from the cathode filament in the x-ray tube when electric current is passed through it.
GLOSSARY 421
Thermoluminescent dosimeter (TLD): Monitoring device containing certain crystalline compounds (usually lithium fluoride)
that store energy when struck by x-rays. When heated, the crystals
give off light in proportion to the amount of radiation exposure.
Threshold dose response curve: A graph showing the relationship between the dose of exposure and the response of the tissues,
indicating that there is a “threshold” amount of radiation, below
which no biological response would be expected.
Thyroid collar: An attached or detachable supplement to the lead
apron. Contains 0.25 mm lead or lead-equivalent materials to protect the radiosensitive thyroid gland in the neck region during the
exposure of intraoral radiographs.
Timer: A mechanical, electrical, or electronic device that can be set
to predetermine the duration of the interval that current flows
through the x-ray machine to produce x-rays.
Time–temperature: Principle of film processing. The length of
time the film spends in the developer is based on the temperature of
the developer solution. When the temperature is cool, processing
time is increased. When the temperature is warm, processing time
is decreased. Film manufacturer will usually recommend an ideal
temperature and time that will produce quality images.
TLD: See Thermoluminescent dosimeter.
Tomograph: A radiograph made using the tomography technique.
Tomography: A radiographic technique used to show detailed images
of structures located within a predetermined plane of tissue while
eliminating or blurring those structures in the planes not selected.
Topographical technique: Occlusal radiography technique that
follows the rules of bisecting. The central rays of the x-ray beam
are directed through the apices of the teeth perpendicularly toward
the bisector to produce an image.
Torus (tori-plural): Form of benign tumor. Outgrowth of bone
called exostosis.
Torus mandibularis (lingual torus): Hard, bony protuberance on
the lingual surface of the mandible. Usually located above the
mylohyoid line near the premolars. Often bilateral.
Torus palatinus: Hard, bony protuberance on the midline of the
maxilla.
Total filtration: The combination of inherent and added filtration in an
x-ray machine. Many states require a total filtration of 2.5 mm of aluminum equivalent for x-ray machines operating at or above 70 kVp.
Trabeculae: Tiny bars or plates of bone that form a network of
various-sized compartments that account for the honeycomb
appearance of bone.
Trabecular bone (cancellous bone): The softer spongy bone that
makes up the bulk of the inside portion of most bones. The cells of
trabecular bone vary in size and density.
Tragus: Small cartilaginous prominence of tissues located near the
center and in front of the acoustic meatus (outer ear opening).
Transcranial projection: Extraoral projection used to image the
temporomandibular joint (TMJ) in both an open and closed position. Also called a TMJ projection.
Transformer: One of several types of electrical devices capable of
increasing or decreasing the voltage of an alternating current by
mutual induction between primary and secondary coils or windings
on cores of metal. See High-voltage transformer and Low-voltage
transformer.
Transitional (mixed) dentition: Having both primary and permenent teeth present in the oral cavity. Usually exists between 6 and
12 years of age.
Triangulation: Widening of the periodontal ligament space at the
crest of the interproximal bone.
Tube head (tube housing): Protective metal covering that contains the x-ray tube, the high-voltage and low-voltage transformers,
and insulating oil. Attached to the flexible extension arm by a yoke.
The PID attaches to the tube head at the port.
Tube shift method: Method of localization. See Buccal-object rule.
Tube side: Describes the side of an intraoral film packet, phosphor
plate, digital sensor, and extraoral film or phosphor plate cassette
that must face the source of x-rays coming from the x-ray tube.
Tuberosity: Broad eminence on a bone.
Tumor: Swelling or a growth of tissue.
Tungsten (Wolfram): Element with an atomic number of 74. High
melting point makes this metal ideal for use as the cathode filament
and as the anode target.
Underdevelopment: Not leaving the film in the developer solution
long enough or using developer that is too cool or an old, weak
solution. Underdevelopment results in a light image.
Underexposure: Not exposing the image receptor long enough or
using an inappropriately decreased kVp or mA setting. Underexposure results in a light image.
Universal precautions: A method of infection control in which
blood and certain body fluids are treated as if known to be infectious
for HIV, HBV, and other blood-borne pathogens. The all-inclusive
term standard precautions has replaced universal precautions, where
the focus is on blood-borne pathogens.
Useful beam (useful radiation): That part of the primary beam
that is permitted to emerge from the tube head and limited by the
port, collimator, and lead-lined PID.
Velocity: Property exhibited by electromagnetic radiation. Refers to
the speed of the wave as it travels through space. In a vacuum, all
electromagnetic radiations travel at the speed of light (186,000
miles/sec or ).
Verbal communication: Using words to exchange information
between two or more persons.
Vertical angulation: The direction of the central beam in an up or
down direction achieved by directing the tip of the PID upward or
downward. See Negative angulation and Positive angulation.
Vertical (angular) bone loss: Occurs in a vertical direction. Alveolar crest is reduced in a manner that creates angular defects.
Vertical bitewing radiograph: Bitewing radiograph placed in the
oral cavity with the long dimension of the image receptor positioned vertically. Covers an increased area in the vertical dimension, resulting in more information regarding the periodontium
being recorded.
Vertical bitewing series: A set of 4 to 7 vertical bitewings. May
include both posterior and anterior images.
View box: Device used to view dental radiographs. Consists of a
light source illuminator behind an opaque glass.
Volt: Unit of electromotive force or potential that is sufficient to cause
a current of l ampere (A) to flow through a resistance of 1 ohm (W).
Voltage: Electrical pressure or force that drives the electric current
through the circuit of the x-ray machine. See Kilovolt and Kilovolt
peak.
3 * 108 m/sec
422 GLOSSARY
Voltmeter: Device for measuring the electromotive force (the difference in potential or voltage) across the x-ray tube.
Voxel (volume element): Similar to a pixel, but adds a third dimension
of digital data that together constitute an image. Used in computed
tomography imaging. Voxel is a term shortened from the words “volume” and “element” (similar to the shortened term for pixel where
)
Waste stream: The collective flow of waste materials beginning at
the point of discard, through waste treatments, to the final disposition of the material.
Waters radiograph: Also called the sinus projection. Similar to the
posteroanterior cephalometric radiograph except that the center of
interest is focused on the middle third of the face.
Wavelength: In radiography, the length in angstrom units or centimeters of the electromagnetic radiations produced in the x-ray
machine. The distance from the crest, or top of one wave to the
crest of the next, determines the wavelength—hence its penetration
ability.
Weighting factor (qualifying factor): Used to convert absorbed
dose to dose equivalent. Takes into consideration the difference in
biological effectiveness of various types of radiation (x-, gamma,
alpha, beta, etc). Some radiations (such as alpha particles) cause
more biological damage than others (such as x-rays). The qualifying factor for dental x-rays is 1; for alpha particles it is 10.
Wet reading: Viewing a radiograph under white light conditions
after only two or three minutes of fixation. Used when a diagnosis
from the radiograph is needed quickly. Following the wet reading,
the film must be returned to the fixer to complete processing.
Working radiograph: A film that is rapidly processed when information is needed quickly. Often used during endodontic procedures. However, short developing and fixing times, combined with
minimal washing, result in a substandard radiograph.
x-coordinate: One of two values assigned to dimensions of a pixel
that tell the computer where the pixel is located. Computer software uses the x-coordinate along with the y-coordinate to reconstruct digital data captured by a sensor or photostimuable plate into
a radiographic image displayed on a monitor.
X-ray (roentgen ray): Radiant energy of short wavelength that has
the power to penetrate substances and to record shadow images on
photographic film, phosphor plates, and digital sensors.
X-ray film: See Radiograph and Film packet.
X-ray tube: Electronic tube located in the tube head that generates
x-rays.
y-coordinate: One of two values assigned to dimensions of a pixel
that tell the computer where the pixel is located. Computer software uses the y-coordinate along with the x- coordinate to reconstruct digital data captured by a sensor or photostimuable plate into
a radiographic image displayed on a monitor..
Yoke: Curved portion of the x-ray machine that is connected to the
extension arm. The tube head is suspended within the yoke and can
be rotated vertically and horizontally within it.
Zygoma: Cheek bone. Attaches to the zygomatic process of the temporal bone to form the zygomatic arch.
Zygomatic arch: Arch formed by the temporal process of the zygomatic bone and the zygomatic process of the temporal bone. Forms
the outer margin of the cheek prominence.
Zygomatic process: Process of the temporal bone that attaches to
the zygoma to form the zygomatic arch.
pix = plural of picture and el = element
423
A
Abscess, 296–97
Absorbed dose, 16
Absorption, 13–15
Acetic acid, 86
Acidifier, 86
Acquired immunodeficiency syndrome (AIDS), 115
Activator, 85
Acute radiation syndrome (ARS), 51
Added filtration, 62
Advanced caries, 305, 306
Advanced chronic or aggressive periodontitis, 320, 322–23
Age, radiation injury and, 51
Aged film fog, 238
Aging patients, 341
Air spaces images viewed on panoramic radiograph, 397–98
glossopharyngeal air space, 397
nasopharyngeal air space, 397
palatoglossal air space, 397
Ala, 183, 185, 386
ALARA (as low as reasonably achievable), 50, 58
for children, 329
Ala-tragus line, 183, 386
Alkaline, 256
Alpha particle, 10
Alternating current (AC), 25
Aluminum equivalent, 62
Alveolar bone, 277
Alveolar (crestal) bone, 315
Alveolar process, 275, 277
Alveolus, 277
Amalgam, 292
Amalgam tattoo, 292
Ameloblastoma, 299
American Academy of Oral and Maxillofacial Radiology
(AAOMR), 70
American Academy of Pediatric Dentistry, 326
American Academy of Periodontology classification of periodontal
disease, 320
American Dental Assistants Association (ADAA), 135
American Dental Association (ADA), 70, 135
American Dental Hygienists’Association (ADHA), 135
Amperage, 23–24, 26
Ampere (A), 26
Analog, 99, 100, 108
Anatomical order, 265
Anatomical variations, supplemental radiographic techniques for,
353–56
edentulous patient, 353–56
tori, 353
Anatomy. See Radiographic anatomy
Andontia, 294–95
Angle of the mandible, 275, 396
Angstrom (Å), 12
Angular bone loss, 315
Angular cheilitis, 344
Angulation
horizontal, 152–53, 166
negative, 153
positive, 153
vertical, 152–53, 166
Ankylosis, 368
Anode, 27
Anodontia, 278, 294–95, 326
Anomaly, 294. See also Developmental anomalies, appearance of
Anterior nasal spine, 275, 280, 281, 394
Anterior palatine foramen, 281
Anterior structures not recorded, 229
Antihalation coating, 80
Antiseptic, 115
Apical disease, appearance of, 296–97
cyst, 297
granuloma, 297
periapical abscess, 296–97
Apical foramen, 277
Apical structures not recorded, 229
Appearance, 139
Apprehensive patient, 341, 342
Area monitoring, 67
Arrested caries, 309
Articular eminence, 393
Artifacts, 234, 366
Artificial intelligence, 99, 107
Asepsis, 115
Atom, 9
Atomic number, 9
Atomic structure, 9–10
Atomic weight, 13
Attitude, 139
Authority, 242
Automatic film processing, 91–93
equipment, 91–92
preparation, 92
procedure, 93
Automatic processor, 247
Autotransformer, 25–26
B
Background radiation, 16–17
Barrier envelope, 119
Base material, 292, 293
Benign, 300
Beta particle, 10
Binding energy, 10
Biodegradable, 259
Biological effect mechanisms, 48–49
Bisecting technique, 5, 148–49, 179–95
advantages and disadvantages of, 180
dimensional distortion, 181
fundamentals of, 180–81
horizontal angulation, 182
image receptor positioners, holding in place, 181–82
mandibular canine exposure, 191
mandibular incisors exposure, 190
mandibular molar exposure, 193
mandibular premolar exposure, 192
maxillary canine exposure, 187
maxillary incisors exposure, 186
Index
Bisecting technique (Continued)
maxillary molar exposure, 189
maxillary premolar exposure, 188
object-image receptor distance, 181
points of entry, 185
steps in, summary of, 183–84
target-image receptor distance, 180
vertical angulation, 182, 185
Bisecting technique error, 232
Bisector, 180, 182
Biteblock, 154
bisecting technique, 181
paralleling technique, 163
Bite extension, 181–82
Bitetab, 202–3
Bitewing examination, 78, 148, 196–214. See also Bitewing technique
fundamentals of, 197–98
horizontal angulation, 203, 206
image receptor positioners, holding in place, 202–3
image receptor size and number to use, 198
point of entry, 207
sequence of placement, 201–2
of transitional dentition, posterior, 335
vertical angulation, 206–7
vertical bitewing series, 318
Bitewing technique, 207–11
canine bitewing exposure, 209
central incisors bitewing exposure, 208
molar bitewing exposure, 211
premolar bitewing exposure, 210
Black lines, marks, or spots
chemical contamination, 235
handling errors, 236
Black paper stuck to film, 237
Black pressure marks, 236
Blank image
handling errors, 236
incorrect exposure, 234
processing and darkroom protocol errors, 235
Bone loss, 315–16
Brown images, 236
Buccal caries, 308
Buccal-object rule, 357, 358
C
Calcifications, appearance of, 299
Calcium hydroxide paste, 293
Calcium tungstate, 368
Calculus, 316
Cancellous bone, 277
Cancer
patients with, 341
radiation and, 52
Canine bitewing exposure, 209
Canine-premolar overlap, 351
Canthus, 183, 184, 185
Carcinogenic mechanisms, 52
Carcinoma, 300
Caries, 303–13
advanced, 306
arrested, 309
buccal, 308
cemental (root), 308
classification of, 306–9
conditions resembling, 309–11
depth grading system, 306
detection of, 304–5
description of, 304
enamel (incipient), 305, 306
interpreting, 304, 306
lingual, 308
moderate, 306
occlusal, 307–8
proximal, 307
radiographic appearance of, 305
rampant, 309
recurrent, 308–9
severe, 306
Cassette holder, 382
Cassettes
extraoral image receptors, 369–71
panoramic radiographic procedure, 383
quality control procedures, 247–48
Cataracts, 52
Cathode, 26, 27
Caustic, 256
Cell sensitivity, 49
Cemental (root) caries, 308
Cementoenamel junction (CEJ), 308, 315
Cementomas, 299–300
Cementum, 277
Centers for Disease Control and
Prevention (CDC), 116
Central incisors bitewing exposure, 208
Central ray, 28
Cephalometric radiograph, 366
lateral (lateral skull), 367
posteroanterior, 367
Cephalostat, 365
Cervical burnout, 309, 310
Cervical spine, 396
Chair-side film processing, 91
Chairside manner, 139–40
Characteristic radiation, 13
Charge-coupled device (CCD), 99, 100
Chemical contamination, 235–36
black/white spots, 235
stains, 236
Chemical fog, 238
Chemical fumes, film storage/protection and, 80
Chernobyl, 48
Children, radiographic interpretation, 334–36
mandibular anterior occlusal radiograph of primary dentition, 335
mandibular canine periapical radiograph of transitional dentition,
336
mandibular molar periapical radiograph of transitional dentition,
336
maxillary anterior occlusal radiograph of primary dentition, 334
maxillary canine periapical radiograph of transitional dentition, 336
maxillary central-lateral incisors periapical radiograph of transitional dentition, 335
maxillary molar periapical radiograph of transitional dentition, 336
posterior bitewing radiograph of transitional dentition, 335
Children, radiographic techniques, 325–39
ALARA radiation protection, 329
anodontia, 326
assessment of radiographic need, 326
communication, 141, 334
exposure intervals, 326
extraoral radiographs, 327–28
horizontal angulation, 330–33
image receptor sizes and numbers, 326–27, 330–33
lateral jaw projection, 327–28
panoramic radiograph, 327
patient management, 141, 329, 334
point of entry, 330–33
primary dentition, 327
424 INDEX
projection types, 327–28
suggested, 328–29, 330–33
supernumerary (extra) teeth, 326
transitional mixed dentition, 326, 327
vertical angulation, 330–33
Cieszynski, A., 4, 5
Clear image. See Blank image
Code of Ethics, 135
Coherent scattering, 14
Coin test, 246
Collimation, 62–64
Collimator, 28
Communication. See Patient communication
Complementary metal oxide semiconductor (CMOS), 99, 100
Composite, 292
Compton effect (scattering), 14–15
Computed tomography (CT), 4, 372–73
Computer, in digital radiography, 106
Computer monitor, 247
Condensing osteitis, 299
Condyle, 275
Cone, 3
long, 5
Cone beam computed tomography (CBCT), 4, 365, 373–74
Cone beam volumetric imaging (CBVI), 4, 373
Conecut error, 153, 232–33
Confidentiality, 134
Consumer-Patient Radiation Health and Safety Act of 1981, 71, 132
Contact point, 203
Contamination, 115
Contrast, 34
Control panel, 21, 22–24
electric current, 22
exposure button, 24
kilovolt peak (kVp) selector, 23
line switch, 22
milliampere (mA) selector, 22–23
timer, 23
Coolidge, William David, 3, 4
Coronal structures not recorded, 229–30
Coronoid process, 275, 283, 395
Cortical bone, 277
Coulombs per kilogram (C/kg), 15
Crookes, William, 2
Crookes tube, 2
Cross-contamination, 115
Cross-sectional technique, 216
Crowded teeth, 351
Crowns, 292–93
full metal, 292
porcelain-fused-to-metal, 293
porcelain jacket, 293
porcelain stainless steel, 293
Crystal, 38
Culturally diverse patients, 341, 346–47
Cumulative effect, 49
Cyst, 296, 297, 298
D
Dark images
development error, 235
incorrect exposure, 233–34
Darkroom, 84, 86–88
lighting, 86–87
light leaks, test for, 246–47
maintenance, 87–88
monitoring, 244, 246–47
protocol errors, 235
safelight test, 244, 246–47
Daylight loader, 86
infection control for processors with, 126–28
“Dead-man” exposure switch, 24
Dead pixel, 236
Decay, 10
Definition. See Sharpness
Definitive evaluation method, 357
Dens in dente, 295
Density, 33–34
Dental Assisting National Board Examination (DANB), 132
Dentigerous cyst, 297
Dentin, 277
Dentinoenamel junction (DEJ), 306
Dentition, 278
Department of Health and Human Services (DHHS), 134
Depth grading system, 306
Deterministic effect, 51
Developer, 84, 85
safe handling of, 256, 257
Developing agent, 85
Developmental anomalies, appearance of, 294–96
andontia, 294–95
dens in dente, 295
dilaceration, 296
fusion, 296
gemination (twinning), 296
hypercementosis, 295–96
mesiodens, 295
supernumerary teeth (extra teeth), 295
taurodontia, 296
Diagnosis vs. interpretation in viewing radiographs, 268
Digital image/imaging, 4–5, 98
Digital image receptors, 4–5
Digital Imaging and Communications in Medicine (DICOM), 109,
111
Digital imaging equipment, radiographic wastes, 260–61
Digital radiographic noise, 237, 238
Digital radiography, 97–113
acquiring, methods of, 99–101
advantages and limitations of, 110
characteristics of, 108–9
DICOM standards, 109, 111
direct digital imaging, 99–100
exposure, 102–4
fundamental concepts, 98
indirect digital imaging, 99, 100–101
patient preparation, 102
radiation exposure, 109
terminology, 99
uses, 98–99
Digital radiography equipment, 101–2, 104–8
computer, 106
image receptors, 104–6
preparation, 101–2
software, 106–8
x-ray machine, 104
Digital sensor type, 35
Digital subtraction, 99, 107
Digitize, 99
Dilaceration, 296
Direct current (DC), 25
Direct digital imaging, 99–100
Direct supervision, 132
Direct theory, 48
Disability, 344–46. See also Special needs patients
Disclosure, 134
Disinfect, 115
Disinfectants, safe handling of, 257–58
Disinfection of instruments and equipment, 117–18
INDEX 425
DIS (direct ion storage) monitor, 69
Disposal options of radiographic waste
products, 261. See also Radiographic wastes, management of
Distance
effects of variations in, 41–42
object-image receptor distance, 41, 42
radiation protection for radiographer, 67, 68
target-image receptor distance, 41–42
target-surface distance, 41
Distomesial overlap, 232
Disto-oblique periapical radiographs, 357, 359–60
Distortion, 39
dimensional, 181
DNA (deoxyribonucleic acid), 9
Documentation, 134
Dosage, 5
Dose, 15
absorbed, 16
critical organs and, 53
effective dose equivalent, 16
lethal, 50
total, 50
Dose equivalent, 16
effective, 54
Dose rate, 50
Dose-response curve, 49–50
threshold/nonthreshold, 49
Dosimeter, 69
Dots, 236
Double exposure, 234
Double image, 234
Drying, in film processing, 84
Duplicate radiograph, 360–61
Duplicating film, 79–80, 360–61
E
Eastman Kodak Company, 4
Edentulous patient, 353–56
Education. See Patient education
Effective dose equivalent, 16
Elderly patients
communicating with, 141
Electrical circuit, 25
Electric current, 22, 25
Electricity, 24–26
alternating current, 25
amperage, 26
direct current, 25
electrical circuit, 25
transformers, 25
voltage, 26
Electrode, 26–27
Electromagnetic radiation, 11–12
Electromagnetic spectrum, 11–12
Electron, 9–10
Electron cloud, 27
Electronic noise, 99, 109, 237, 238
Electron shells, 9–10
Element, 9
Elementary and Dental Radiology (Raper), 3
Elon, 85
Elongation, 182, 232
Embrasure
bisecting technique, 182
bitewing radiography, 198, 203
paralleling technique, 166
Embryological defects, 52
Empathy, 139
Emulsion, 75
solarized, 80
thickness of, 77–78
Enamel, 277
Enamel (incipient) caries, 305, 306
Endodontic fillers, 293, 294
Endodontic therapy, 356–57
Energy, 9, 10
Energy levels, 9
Enlargement. See Magnification
Equipment
film duplicating procedure, 360
regulations, 132
for viewing radiographs, 247, 268–70
Equipment standards, 59, 62–66
collimation, 62–64
fast film and digital image sensors, 64–65
filtration, 59, 62
image receptor holding devices, 65
lead apron, 65, 66
position indicating device, 64
thyroid collar, 65–66
Ethics, 135
Evaluation, periodic, 242
Exfoliation, 278, 328
Exostosis, 300
Exposure, radiation. See Radiation exposure
Exposure button, 24
Exposure charts, 44
Exposure factors, film, 35
exposure time, 40
incorrect, 233–34
kilovoltage (kVp), 41
milliamperes (mA), 40
milliampere/seconds (mAs), 41
occlusal radiographs, 217
variations in, 39–41
Exposure time, 40
Extension arm, 21, 22, 24
External aiming device, 163, 203
External auditory meatus, 275, 393
External resorption, 297, 298
Extraoral equipment monitoring, 247–48
Extraoral film, 78–79
packaging, 79
size, 79
Extraoral image receptors, 366, 368–71
cassettes, 369–71
film identification, 371
intensifying screens, 368, 370, 371
traditional film, 366, 368
Extraoral radiography, 35, 364–76
for children, 327–28
computed tomography, 372–73
cone beam computed tomography, 365, 373–74
exposure factors, 371
extraoral image receptors, 366, 368–71
grids, 371
in oral health care, 365–66
purpose and use of, 365
tomography, 372–74
Extra teeth (supernumerary), 295, 326
Eyewash station, 256, 257
F
Facial profile radiographs, 365
Fast film and digital image sensors, 64–65
Federal Performance Act of 1974, 132
Filament, 27
Film, x-ray, 74–82
426 INDEX
composition of, 75
contrast, 35
digital sensor type, 35
duplicating, 79–80
exposure factors (See Exposure factors, film)
extraoral, 78–79
fast film and digital image sensors, 64–65
history of, 4
image receptor holder, 65
intraoral, 76–78
latent image formation, 75
monitoring, 247
optimum processing, patient protection and, 65
packet, 76–77
pedodontic, 78
screen, 78
speed, 77–78
storage and protection, 80
types of, 76–80
Film badge, 69
Film duplicating procedure, 360–61
equipment, 360
Film duplicator, 360
Film feed slot, 92
Film fog, 237
Film hanger, 89
Film holder. See Image receptor positioning
Film loop, 202–3
Film mount, 265
Film mounting. See Mounting radiographs
Film processing, 35, 83–96
automatic, 91–93
chemical maintenance, 93–94
darkroom, 86–88
developing, 84
drying, 84
fixing, 84
manual, 88–91
procedures, 35
processing chemical maintenance, 93–94
processing solutions, 247, 248
processing tank, 88
rapid, 91
rinsing, 84
solutions, 84–86
system monitoring, 247, 248
washing, 84
Film processing errors, 235–36
chemical contamination, 235–36
development error, 235
processing and darkroom protocol errors, 235
Film processing solutions, 84–86
developer, 85
fixer, 85–86
hardening agents, 86
replenisher, 86
Film recovery slot, 92
Filter, 28, 62
Filtration, 59, 62
added, 62
inherent, 62
total, 62
Fitzgerald, G. M., 4, 5
Fixer, 84, 85–86
safe handling of, 255–56
used fixer waste, disposal of, 259–60
Fixing agent, 85
Floor, sinus, 275, 282
Focal spot, 27, 35–36
Focal trough (layer), 379, 381–82
Focusing cup, 27
Fogged images, 237–38
aged film fog, 238
chemical fog, 238
digital radiographic noise, 237, 238
miscellaneous light fog, 238
radiation fog, 237
safelight fog, 238
storage fog, 238
white light fog, 237–38
Follicular (eruptive) cyst, 297
Foreign body, 301
Foreshortening, 182, 232
Fracture line, 301
Frankfort plane, 386
Frequency, 12
Frequently asked questions (FAQs), 143
Fresh-film test, 247
Frontal bone, 274
Full metal crown, 292
Full mouth series (full mouth survey), 150–52
Furcation involvement, 316
Fusion, 296 G
Gag reflex, 341, 342–44. See also Hypersensitive gag reflex
Gamma rays, 10
Gelatin, 75
Gemination (twinning), 296
General/bremsstrahlung radiation, 13
General Electric, 3
Generalized bone loss, 315
Genetic cells, 49
Genetic effect, 49
Genetic mutation, 52
Genial tubercles, 275, 283, 395
Geometric factors, 35
Ghost images, 379, 398–99
Gingivitis, 315, 320–21
Glenoid fossa, 393
Globulomaxillary cyst, 297, 298
Glossopharyngeal air space, 397
Goals, 135
Granuloma, 296, 297
Gray (Gy), 16
Gray scale, 99, 108
Gray value, 99, 100
Green films, 235
Grid, 35, 371
Gutta percha, 293 H
Half-value layer (HVL), 62
Halide, 75
Hamulus, 283, 395
Handling errors, 236–37
black image, 236
black lines, 236
black paper stuck to film, 237
black pressure marks, 236
blank image, 236
dots, 236
lightening pattern, 236
panoramic radiography, 389–93
smudged film, 237
star-bursts, 236
white lines or marks, 236, 237
Handwashing, 117
INDEX 427
Hardening agent, 86
Hard palate, 394
Hard radiation, 12
Hazardous waste, 252
Head positioner guides, 385–86
Health Insurance Portability and Accountability Act (HIPAA), 134
Hearing impairment, patients with, 341
Heat and humidity, film storage/protection and, 80
Hemostat, 356
Hepatitis B, 115
Herringbone error, 231
High contrast, 34
Horizontal angulation, 152–53
bisecting technique, 182
bitewing examination, 203, 206
children, radiographic techniques for, 330–33
occlusal radiographs, 217–18
paralleling technique, 166
Horizontal bitewing radiograph, 198
Horizontal bone loss, 315–16
Human immunodeficiency virus (HIV), 115
Hydroquinone, 85
Hypercementosis, 295–96
Hypersensitive gag reflex, 341, 342–44
extreme cases of, 343
reducing psychogenic stimuli, 342–43
reducing tactile stimuli, 343
I
Identification dot, 77, 152
incorrect position of, 231
mounting radiographs, 265–66
Identification of, 292–94
Idiopathic resorption, 297
Image receptor positioning, 65
anterior structures not recorded, 229
apical structures not recorded, 229
bisecting technique, 181–82
bitewing examination, 202–3
coronal structures not recorded, 229–30
digital radiography, 104–6
identification dot, incorrect position of, 231
incorrect, 229–31
intraoral radiographic procedures, 153–54
occlusal radiographs, 217
paralleling technique, 162, 163–65
reversed image error, 231
slanted or tilted instead of straight occlusal plane, 230–31
Image receptor size/number
for bitewing examination, 198
for children, 326–27, 330–33
Immunization, 115
Impacted teeth, 278
Implant, 294
Impulse, 23
Incandescence, 27
Incipient (enamel) caries, 305, 306
Incisive canal, 394
Incisive canal cyst, 297
Incisive (anterior palatine) foramen, 275, 281, 394
Indicator ring, 165
Indirect digital imaging, 99, 100–101
Indirect theory, 48–49
Infection control, 114–29
after procedure, 123–25
classification of objects used, 118–19
disinfection of instruments and equipment, 117–18
guidelines for, 116
handwashing, 117
intraoral film, 119
personal protective equipment, 117
prior to procedure, 119–22
during procedure, 122–23
for processors with daylight loader, 126–28
purpose of, 115–16
for radiographic procedure, 119–25
for radiographic processing, 125–26
standard precautions, 115, 116
sterilization of instruments and equipment, 118
terminology, 115
universal precautions, 115
Inferior border, 275, 282, 285, 396
Informed consent, 133–34
Infraorbital foramen, 393
Inherent filtration, 62
Injury from radiation exposure, factors that determine, 50–51
Instruments and equipment
sterilization and disinfection of, 117–18
Insurance claims, 134
Intensifying screens, 37–38, 78, 247–48, 368, 370, 371
Intensity, 28
Interdental septa, 315
Internal resorption, 298
International Commission on Radiation Units and Measurements
(ICRU), 15
International Commission on Radiological Protection (ICRP), 70
Interpersonal skills, 139–40
Interpretation vs. diagnosis in viewing radiographs, 268
Interproximal, 307
Interproximal caries, 307
Interproximal radiograph, 148, 197–98
Intraoral film, 76–78, 119
emulsion speeds (sensitivity), 77–78
infection control, 119
packaging, 77
packet, 76–77
projection types, 78
size, 78
speed groups, 78
Intraoral image receptors, pixel size of, 38
Intraoral radiography, 35
anatomy, basics of radiographic, 278–86
bitewing examination, 148
film holders, 153–54
horizontal angulation, 152–53
image receptor positioners, holding in place, 153–54
occlusal examination, 148
periapical examination, 148
points of entry, 153
preparations, 154–55
procedures, 147–60
radiographic examination, 150–52
seating position, patient, 155–56
sequence of procedure, 156–58
shadow casting, 149–50
techniques, 148–49
vertical angulation, 152–53
Inverse square law, 42–43
Inverted Y, 281
Involuntary movement conditions, 341
Ion, 10
Ionization, 10, 48
Ionizing radiation, 10
Ion pair, 10
Irradiation, 49
Irreparable injury, 51
Isometric triangle, 180
Isotope, 10
428 INDEX
K
Kells, C. Edmund, 3, 4
Kilovolt (kV), 26
Kilovolt peak (kVp), 23, 35, 41
Kinetic energy, 13, 28
L
Labels, 255
Labial mounting method, 266
Lamina dura, 277, 320
Landmarks, 280–86. See also individual regions
air spaces images viewed on panoramic radiograph, 397–98
mandible and surrounding tissues, 395–96
mandibular anterior region, 283–85
mandibular posterior region, 285–86
maxilla and surrounding tissues, 393–95
maxillary anterior region, 280–82
maxillary posterior region, 282–83
normal anatomical, 274–76
soft tissue images viewed on panoramic radiograph, 396–97
Laser beam, 11
Latent image, 75, 84
Latent period, 51
Lateral cephalometric radiograph (lateral skull), 367
Lateral fossa, 282
Lateral jaw projection, 327–28
Lateral jaw radiograph (mandibular oblique lateral), 367
Lateral pterygoid plate, 393
Law of B and T, 49
Lead
safe handling of, 258–59
waste, 260
Lead apron, 65, 66
Lead equivalent, 65
LED (light-emitting diode), 87
Legal responsibilities, 131–37
equipment regulations, 132
ethics, 135
goals, 135
informed consent, 133–34
liability, 134
license regulations, 132
malpractice issues, 135
patient records, 134–35
patient relations, 133
risk management, 132–33
Lethal dose (LD), 50
Liability, 134
License regulations, 132
Light, film storage/protection and, 80
Lightening pattern, 236
Light (thin) images
development error, 235
incorrect exposure, 233–34
Lighting, darkroom, 86–87
daylight loader, 86, 87
in-use light, 87
light-tight, 86
safelight, 87
viewbox, 87
white ceiling light, 87
Light leaks, test for, 246–47
Light-tight, 86, 91, 244
Line pair, 108
Line pairs per millimeter (lp/mm), 99
Line switch, 22
Lingual caries, 308
Lingual foramen, 275, 283, 395
Lingual mounting method, 266
Lingula, 395
Localization, 357
Localization methods, 357
definitive evaluation method, 357
right-angle method, 357
tube-shift method (buccal-object rule), 357, 358
Localized bone loss, 315
Logs, 242
Long-scale contrast, 34
Low birth rate, 52
Low contrast, 34
M
Mach band effect, 310–11
Magnification, 38–39
Maintenance schedules, 242
Malaligned or crowded teeth, 351
Malignant, 300
Malpractice, 135
Mandible, 275
Mandible and surrounding tissue landmarks, 395–96
angle of the mandible, 396
cervical spine, 396
coronoid process, 395
genial tubercles, 395
inferior border of the mandible, 396
lingual foramen, 395
lingula, 395
mandibular canal, 395
mandibular condyle, 395
mandibular foramen, 395
mandibular notch, 395
mental foramen, 395
mental fossa, 395
mental ridge, 395
mylohyoid ridge, 396
oblique ridge, 396
submandibular fossa, 396
Mandibular anterior occlusal radiograph of primary dentition, 335
Mandibular anterior region landmarks, 283–85
genial tubercles, 283
lingual foramen, 283
mental fossa, 285
mental ridge, 283
radiolucent features, 283–84
radiopaque features, 283
Mandibular canal, 275, 285, 395
Mandibular canine exposure, 174
bisecting technique, 191
paralleling technique, 174
Mandibular canine periapical radiograph of transitional dentition, 336
Mandibular condyle, 395
Mandibular cross-sectional occlusal radiograph, 224
Mandibular foramen, 275, 395
Mandibular incisors exposure, 173
bisecting technique, 190
paralleling technique, 173
Mandibular molar exposure, 176
bisecting technique, 193
paralleling technique, 176
Mandibular molar periapical radiograph of transitional dentition, 336
Mandibular notch, 275, 395
Mandibular oblique lateral projection, 327–28
Mandibular posterior region landmarks, 285–86
inferior border of the mandible, 285
mandibular canal, 285
mental foramen, 285
mylohyoid ridge, 285
oblique ridge, 285
INDEX 429
Mandibular posterior region landmarks, (Continued)
radiolucent features, 285
radiopaque features, 285
submandibular fossa, 285
torus mandibularis (lingual torus), 285
Mandibular premolar exposure, 175
bisecting technique, 192
paralleling technique, 175
Mandibular topographical occlusal radiograph
anterior, 222
posterior, 223
Manual film processing, 88–91
equipment, 88–89
preparation, 89
procedure, 89–91
Mastoid process, 275, 393
Material Safety Data Sheets (MSDSs), 252–55
Maxilla, 275
Maxilla and surrounding tissue landmarks, 393–95
anterior nasal spine, 394
articular eminence, 393
external auditory meatus, 393
glenoid fossa, 393
hamulus, 395
hard palate, 394
incisive canal, 394
incisive foramen, 394
infraorbital foramen, 393
lateral pterygoid plate, 393
mastoid process, 393
maxillary sinus, 395
maxillary tuberosity, 393
nasal cavity, 394
nasal septum, 394
orbit, 393
styloid process, 393
zygoma, 395
zygomatic process of the maxilla, 395
Maxillary anterior occlusal radiograph of primary dentition, 334
Maxillary anterior region landmarks, 280–82
anterior nasal spine, 280
incisive foramen, 281
inverted Y, 281
lateral fossa, 282
median palatine suture, 281
nasal fossa (cavity), 281–82
nasal septum, 280
radiolucent features, 281–82
radiopaque features, 280–81
soft tissue of the nose, 281, 282
Maxillary canine exposure, 170
bisecting technique, 187
paralleling technique, 170
Maxillary canine periapical radiograph of transitional
dentition, 336
Maxillary central-lateral incisors periapical radiograph of transitional
dentition, 335
Maxillary incisors exposure, 169
bisecting technique, 186
paralleling technique, 169
Maxillary molar exposure, 172
bisecting technique, 189
paralleling technique, 172
Maxillary molar periapical radiograph of transitional
dentition, 336
Maxillary posterior region landmarks, 282–83
coronoid process, 283
floor, 282
hamulus, 283
maxillary sinus, 283
maxillary tuberosity, 282
pterygoid plates, 282
radiolucent features, 283
radiopaque features, 282–83
septum, 282
zygoma, 282
zygomatic arch, 282
zygomatic process, 282
Maxillary premolar exposure, 171
bisecting technique, 188
paralleling technique, 171
Maxillary sinus, 275, 283, 395
Maxillary topographical occlusal radiograph
anterior, 220
posterior, 221
Maxillary tuberosity, 275, 282, 393
Maxillofacial, 365
Maximum permissible dose (MPD), 70
for general public, 70
for radiation workers, 70
McCormack, Franklin, 4, 5
Mean tangent, 153, 182, 203
Median palatine suture, 275, 281
Mental foramen, 275, 285, 395
Mental fossa, 285, 395
Mental ridge, 275, 283, 395
Mesiodens, 295
Mesiodistal overlap, 232
Metallic restorations, 291–92
Microbial aerosol, 115
Microsievert (μSv), 16
Midsagittal plane, 156, 386
Milliampere (mA), 22–23, 26, 40
Milliampere/second (mAs), 41
Millisievert (mSv), 144
Miscellaneous light fog, 238
Modeling, 334
Moderate caries, 305, 306
Moderate chronic or aggressive periodontitis, 320, 322
Molar bitewing exposure, 211
Molecule, 9
Monitoring
area monitoring, 67
darkroom, 244, 246–47
equipment used to view radiographic images, 247
extraoral equipment, 247–48
personnel monitoring, 69–70
processing system, 247, 248
of radiation, 67, 69–70
schedule, 242
x-ray film, 247
x-ray machine, 243–44, 245
Morton, William James, 3, 4
Motion, 37
Motor disorders, 341
Mounting radiographs, 265–68
advantages of, 265
anatomical landmarks, 267
film mounts, 265
identification dot, 265–66
labial mounting method, 266
lingual mounting method, 266
methods of, 266
procedure, 266–68
using mounted radiographs, 270
Mouyen, Francis, 4–5
Mylohyoid ridge, 275, 285, 396
430 INDEX
N
Nasal bones, 275
Nasal cavity, 394
Nasal conchae, 282
Nasal fossa (cavity), 280, 281–82
Nasal septum, 275, 280, 394
Nasopharyngeal air space, 397
National Board Dental Hygiene Examine (NBDHE), 132
National Council on Radiation Protection and Measurements
(NCRP), 70
National Voluntary Laboratory Accreditation Program
(NVLAP), 70
Needs assessment, 242
Negative angulation, 153
Negative shadows, 379
Negligence, 135
Neoprene gloves, 255
Neutron, 9
Nitrile gloves, 255
Noise, 99, 109
Nonmetallic restorations, 292, 309–10
Nonodontogenic cyst, 297
Nonodontogenic tumors, appearance of, 300–301
Nonthreshold dose-response curve, 49
Nonverbal communication, 141
Nutrient canal, 277
Nutrient foramen, 277
O
Object-image receptor distance, 37, 41, 42
bisecting technique, 181
Oblique ridge, 275, 285, 396
Occipital bone, 274
Occlusal caries, 307–8
Occlusal examination, 148, 215–26. See also Occlusal radiographs
types of, 216
Occlusal plane, 156
slanted or tilted instead of straight, 230–31
Occlusal radiographs, 78, 148, 216–19
cross-sectional technique, 216
exposure factors, 217
fundamentals of, 216–17
horizontal angulation, 217–18
image receptor orientation, 217
image receptor requirements, 217
mandibular cross-sectional occlusal radiograph, 224
mandibular topographical occlusal radiograph (anterior), 222
mandibular topographical occlusal radiograph (posterior), 223
maxillary topographical occlusal radiograph (anterior), 220
maxillary topographical occlusal radiograph (posterior), 221
patient positioning, 217
points of entry, 218
summary of, 219
topographical technique, 216
vertical angulation, 218, 219
Occlusal trauma, 316–17
Occult disease, 373, 378
Occupational Safety and Health Administration (OHSA), 116, 252
Odontogenic cyst, 297
Odontogenic tumors, appearance of, 299–300
Odontoma, 299
Operator, technical ability of, 59
Oral health care, 365–66
Oral presentation, 142–43
Oral radiography, 3
Oral surgeon’s use of alternate imaging modalities, 364–76
Orbit, 393
Orthodontic materials, 294
Orthodontist’s use of facial profile radiographs, 365
OSL (optically stimulated luminescence) monitor, 69
Ossifications, appearance of, 299
Osteosclerosis, 299
Output consistency test, 243, 245
Overdevelopment, 229
Overexposure, 229
Overhang, 292
Overlapping
canine-premolar, 351, 352
radiographic errors, 206, 232–33
Ownership, 134
Oxidation, 94
P
Palatoglossal air space, 397
Panoramic, 378
Panoramic radiography, 4, 327, 328, 366, 377–401
advantages and limitations of, 378–79
anatomical landmarks, 393–97 (See also Landmarks)
cassette and film preparation, 383
exposure, 384
focal trough, 379, 381–82
fundamentals of, 379–80
ghost images, 398–99
images of machine parts, 398
imaging errors, 386–92
patient positioning, 384, 386, 389–92
patient preparation, 383, 387
procedure, 383–84
processing, 384
purpose and use, 378
unit preparation, 383
Panoramic x-ray machine, 382, 385–86
Paralleling technique, 5, 148, 149, 161–78. See also Periapical
examination
advantages and disadvantages of, 162
fundamentals of, 162–63
horizontal angulation, 166
image receptor holders, 162, 163–65
mandibular canine exposure, 174
mandibular incisors exposure, 173
mandibular molar exposure, 176
mandibular premolar exposure, 175
maxillary canine exposure, 170
maxillary incisors exposure, 169
maxillary molar exposure, 172
maxillary premolar exposure, 171
points of entry, 166
steps in, summary of, 167–68
vertical angulation, 166
vs. bisecting technique, 163
Partial image, 235
Particulate radiation, 10
Pathogens, 115, 116, 316
Patient, radiation protection for, 58–66, 67. See also Equipment
standards
operator ability, 59
optimum film processing, 65
professional judgment, 58
technique standards, 59
Patient communication, 140–41
children, 141, 334
cultural differences, 141
elderly, 141
honesty and, 140
nonverbal, 141
show-tell-do, 141
verbal, 140
INDEX 431
Patient education, 141–45
frequently asked questions, 143–45
methods of, 142–43
necessity for, 142
oral presentation, 142–43
printed literature, 143
value of, 142
Patient management
for children, 329, 334
communication, 334
modeling, 334
patients who refuse radiographs, 135
Show-tell-do, 334
special needs patients (See Special needs patients)
Patient positioning, 155–56
occlusal radiographs, 217
panoramic radiography, 384, 386, 389–92
wheelchair bound patients, 345
Patient records, 134–35
confidentiality, 134
documentation, 134
insurance claims, 134
ownership, 134
releasing, procedure for, 134
retention, 134–35
Patient relations, 133, 139–40
appearance, 139
attitude, 139
interpersonal skills, 139–40
Pediatric dentistry, 326
Pedodontic film, 78
Penetrometer test, 34
Penumbra, 34
Periapical abscess, 296–97
Periapical cemental dysplasia (PCD), 299–300
Periapical examination, 161–95. See also Bisecting
technique; Paralleling technique
Periapical image receptor. See Image receptor positioning
Periapical radiograph, 78, 148
Period of injury, 51
Periodontal diseases, 314–24
advanced chronic or aggressive periodontitis, 320, 322–23
American Academy of Periodontology
classification of, 320
anatomical configurations, 317
appearance of, 315
bone changes recorded by, 315
bone loss, 315–16
calculus, 316
examination for, 315–17
gingivitis, 320–21
interpretation of, 320–23
limitations of, 317
local contributing factors, 316–17
moderate chronic or aggressive periodontitis, 320, 322
occlusal trauma, 316–17
pathogens, 316
prognosis and treatment, 317
slight chronic periodontitis, 320, 321–22
techniques, 318–20
triangulation, 317
uses of, 315–17
Periodontal ligament (PDL), 277
Periodontal ligament (PDL) space, 321
Periodontitis, 315
Periodontium, 318
Permanent teeth, 278, 326, 334–36
Personal protective equipment (PPE)
for infection control, 116, 117
for safe handling of radiographic chemicals and materials, 255
Personnel monitoring, 69–70
Personnel monitoring device, 69–70
PH, 256
Phleboliths, 299
Phosphors, 368, 370
Photoelectric effect, 14
Photon, 12
Photostimuable phosphor (PSP), 98, 99, 100–101
Physical pressure, film storage/protection and, 80
Pixel, 99, 100, 108, 373
dead, 236
size, 38
Points of entry, 153
bisecting technique, 185
bitewing examination, 207
children, radiographic techniques for, 330–33
occlusal radiographs, 218
paralleling technique, 166
Polychromatic, 26
Poor definition, 234
Porcelain-fused-to-metal crown, 293
Porcelain jacket crown, 293
Porcelain stainless steel crown, 293
Port, 28
Position indicating device (PID), 3–4, 41
circular vs. rectangular, 4
equipment standards, 64
incorrect positioning of, 232–33
long cone, 5
positioning for, correct and incorrect, 39
target-image receptor distance established by,
36–37, 38, 41–42
target-surface distance and, 41
Positive angulation, 153
Post and core, 293
Posterior bitewing radiograph of transitional dentition, 335
Posteroanterior (PA) cephalometric radiograph, 367
Potassium alum, 86
Potassium bromide, 85
Potential difference, 26
Pregnant patients, 341
Premolar bitewing exposure, 210
Preparations for intraoral radiographic procedures, 154–55
patient, 155
unit, 154–55
Preservative, 85
Price, Weston A., 4, 5
Primary beam, 27, 28, 62–63
Primary teeth, 278, 326, 334–36
Printed literature, 143
Processing. See Film processing
Processing chemical maintenance, 93–94
Processing equipment, cleaners used on, 258
Processing solutions, 247, 248
Processing system monitoring, 247, 248
automatic processor, 247
processing solutions, 247, 248
Processing tank, 88
Professional organizations, web sites for, 132
Projection types for children, 327–28
Prosthodontist’s use of facial profile radiographs, 365
Protection of x-ray film, 80
Protective barrier, 67, 115, 117
Proton, 9
Proximal surface, 197
Proximal surface caries, 307
Pterygoid plates, 282
Public Law 86-373, 71
432 INDEX
Pulp chamber, 277
Pulp stone, 299
Q
Quality, 28
Quality administration procedures, 242
Quality assurance, 241–50. See also Quality control
authority and responsibilities, 242
competency of radiographer, 242–43
logs and periodic evaluation, 242
monitoring and maintenance schedules, 242
needs assessment, 242
quality administration procedures, 242
written plan, 242
Quality assurance programs, 248
Quality control, 243–48
darkroom monitoring, 244, 246–47
equipment used to view radiographic images monitoring, 247
extraoral equipment monitoring, 247–48
processing system monitoring, 247, 248
time intervals for performing tests, 242
x-ray film monitoring, 247
x-ray machine monitoring, 243–44, 245
Quantity, 28
R
Rad, 16
Radiation, 10. See also X-rays
atomic structure, 9–10
background, 16–17
characteristic, 8–18, 13
electromagnetic, 11–12
general/bremsstrahlung, 13
hard, 12
ionization, 10
ionizing, 10
ionizing radiation, 10
measurement of, 8–18
particulate, 10
radioactivity, 10–11
scatter (secondary), 63–64
secondary, 14–15
soft, 12
units of (See Units of radiation)
Radiation Control for Health and Safety Act, 71
Radiation exposure, 15, 47–56
alternate imaging modalities, 371
biological effect mechanisms, 48–49
cell sensitivity to, 49
in children, 326, 330–33
comparisons, 53–54
critical organs and doses, 53
in digital radiography, 102–4, 109
dose-response curve, 49–50
effective dose equivalent, 54
exposed area, 50
factors, 59
injury, 50–51
organizations responsible for exposure limits, 70–71
panoramic radiographic procedure, 384
risk estimates, 53
sensitivity to, 50
sequence of events following, 51
short- long-term effects of, 51–52
tissues of the body, 51
supplemental radiographic techniques, 353
Radiation fog, 237
Radiation leakage, 67
Radiation protection, 57–73
ALARA, 58
distance, 67, 68
monitoring, 67–70
organizations responsible for exposure limits, 70–71
for patient (See Patient, radiation protection for)
for radiographer, 66–67
safety legislation, 71
shielding, 67, 68
time, 67
Radiation worker, 70
Radiator, 28
Radicular cyst, 297
Radioactivity, 10–11
Radiographer
competency of, 242–43
culturally sensitive, 341, 346–47
radiation protection for, 66–67
Radiographic anatomy, 273–88. See also Anatomical variations,
supplemental radiographic techniques for
alveolar bone, 277
anatomical landmarks, normal, 274–76
basics, intraoral radiographs, 278–86 (See also
Landmarks)
deviations from normal (See Radiographic anatomy,
deviations from normal)
teeth, 277–78
Radiographic anatomy, deviations from normal, 289–302
apical disease, 296–97
calcifications, 299
caries (See Caries)
developmental anomalies, 294–96
nonodontogenic tumors, 300–301
odontogenic tumors, 299–300
ossifications, 299
restorative material, 290–94
tooth resporption, 297–98
trauma, 301
Radiographic chemicals and materials, safe handling of, 252–59
cleaners used on processing equipment, 258
developer, 256, 257
disinfectants, 257–58
eyewash station, 256, 257
fixer, 255–56
general recommendations for, 256
labels, 255
lead, 258–59
Material Safety Data Sheets, 252–55
personal protective equipment, 255
Radiographic contrast, 35
Radiographic errors, 227–40
fogged images, 237–38
handling errors, 236–37
panoramic radiography, 386–92
processing errors, 235–36
recognizing, 228–29
technique errors, 229–34
Radiographic examination, 150–52
Radiographic image, factors affecting, 35–39
contrast, 35, 36
distortion, 39
magnification/enlargement, 38–39
sharpness/definition, 35–38
Radiographic wastes, management of, 259–61
digital imaging equipment, 260–61
discarded radiographs waste, 260
disposal options, 261
lead waste, 260
used fixer waste, 259–60
waste management service, questions to ask of, 259
INDEX 433
Radiographs, 2. See also Supplemental radiographic
techniques
bitewing, 78, 148, 197–214
distances, effects of variations in, 41–42
errors (See Radiographic errors)
exposure charts and, 44
exposure factors, effects of variations in, 39–41
guidelines for prescribing, 60–61
inverse square law and, 42–43
maxillary vs. mandibular, anatomical landmarks distinguishing, 267
mounting (See Mounting radiographs)
occlusal, 78, 148
patients who refuse, 135
periapical, 148
quality, characteristics of, 228
quality, producing, 32–46
retake, 59
terminology used to describe, 33–35
uses of, 5
viewing (See Viewing radiographs)
waste, discarded, 260
Radiography, 2
advances in, 5
digital image receptors, 4–5
history of, 1–7
panoramic, 4
scientists and researchers, 2–3, 4
Radiology, 2
Radiolucent, 13, 33, 84
Radiolucent features
mandibular anterior region landmarks, 283–84
mandibular posterior region landmarks, 285
maxillary anterior region landmarks, 281–82
maxillary posterior region landmarks, 283
Radiolysis of water, 48–49
Radiopaque, 13, 33, 84
Radiopaque features
mandibular anterior region landmarks, 283
mandibular posterior region landmarks, 285
maxillary anterior region landmarks, 280–81
maxillary posterior region landmarks, 282–83
Radioresistant, 49
Radiosensitive, 49
RadioVisioGraphy, 4, 5
Rampant caries, 309
Ramus, 275
Raper, Howard Riley, 3, 4
Rapid (chairside) processing, 91
Rare-earth phosphors, 368
Recovery period, 51
Recurrent (secondary) caries, 308–9
Reference film, 247
Rem, 16
Replenisher, 86
Residual cyst, 297
Resorption, 297
Responsibilities, 242
Restorative material, appearance of, 290–94
amalgam, 292
base material, 293
composite, 292
crowns, 292–93
endodontic fillers, 293, 294
identification of, 292–94
implant, 294
metallic restorations, 291–92
nonmetallic restorations, 292
orthodontic materials, 294
post and core, 293
retention pin, 293
surgical materials, 294
Restrainer, 85
Retained root, 298
Retake radiograph, 59
Retention, 134–35
Retention pin, 293
Reversed image error, 231
Reverse Towne radiograph, 368
Rhinoliths, 299
Right-angle method, 357
Rinsing, in film processing, 84
Risk, 53
vs. benefit, 53
Risk management, 132–33
audit for, 133
Roentgen (R), 15
Roentgen, Bertha, 2
Roentgen, Wilhelm Conrad, 2, 4
Roentgenograph, 2
Roentgen ray, 2
Roller transport system, 92
Rollins, William Herbert, 3, 4
Root canal treatment, 356
Root (cemental) caries, 308
Rotational center, 380
Rule of isometry, 4, 5, 148–49
S
Safelight, 87
Safelight filter, 87
Safelight fog, 238
Safelight test, 244, 246–47
Safety and environmental health, 251–63
OSHA standards, 252
radiographic chemicals and materials, safe handling of, 252–59
radiographic wastes, management of, 259–61
requirements for, 252
Sarcoma, 300–301
Scatter (secondary) radiation, 35, 52, 63–64
Scientists and researchers, 2–3, 4
Sclerotic bone, 299
Screen film, 78, 366
Screen-film contact, 38
Screen thickness, 37–38
Seating position, patient. See Patient positioning
Secondary (recurrent) caries, 308–9
Secondary (scatter) radiation, 14–15, 63–64
Selection criteria, 58
Selective reduction, 85
Self-determination, 133–34
Sensitivity to radiation exposure, 50
Sensor, 4, 100
Sepsis, 115
Septum, 282
Severe caries, 305, 306
Shadow casting, 34–35
intraoral radiographic procedures, 149–50
Sharpness, 34, 35–38
crystal/pixel size and, 38
focal spot size and, 35–36
motion and, 37
object-image receptor distance and, 37
poor, 234
screen-film contact, 38
screen thickness and, 37–38
target-image receptor distance and, 36–37
Shelf life, film storage/protection and, 80
Shielding, 67, 68
434 INDEX
Short-scale contrast, 34
Show-tell-do, 141, 334
Sialolith, 299
Sievert (Sv), 16
Silver halide crystals, 75, 84
Silver point, 293
Silver thiosulphate complex, 259–60
Slight chronic periodontitis, 320, 321–22
SLOB rule, 357
Smudged film, 237
Sodium carbonate, 85
Sodium sulfite, 85
Sodium thiosulfate, 85
Soft radiation, 12
Soft tissue images viewed on panoramic radiograph, 396–97
Soft tissue of the nose, 281, 282
Software, in digital radiography, 106–8
Solarized emulsion, 80
Solid state, 98
Somatic cells, 49
Somatic effect, 49
Spatial resolution, 99, 108
Spatter, 115
Special needs patients, 340–49
aging, 341
angular cheilitis, 344
apprehensive patient, 341, 342
cancer, 341
conditions prompting alterations to radiographic procedures, 341
culturally diverse, 341, 346–47
disability, 344–46
gag reflex, 341, 342–44
hearing impairment, 341
hypersensitive gag reflex, 341, 342–44
involuntary movement conditions, 341
motor disorders, 341
pregnancy, 341
speech reading, 345–46
visual impairment, 341
wheelchair bound, 341
Species, variation in sensitivity, 50
Speech reading, 345–46
Sphenoid bone, 275
Stains, 236
Standard precautions, 115, 116
Star-bursts, 236
Static electricity, 236
Statute of limitations, 135
Step-down transformer, 25
Step-up transformer, 25
Step-wedge, 243, 244
Sterilization of instruments and equipment, 118
Sterilize, 115
Stochastic effect, 51
Storage fog, 238
Storage of x-ray film, 80
Storage phosphor, 100
Structural shielding, 67
Styloid process, 275, 393
Subject contrast, 35
Submandibular fossa, 275, 285, 396
Submentovertex radiograph, 368
Supernumerary teeth (extra teeth), 278, 295, 326
Supplemental radiographic techniques, 350–63
acceptable variations in technique, 351–52
anatomical variations, 353–56
disto-oblique periapical radiographs, 357, 359–60
edentulous patient, 353–56
endodontic techniques, 356–57
exposure factors, 353
film duplicating procedure, 360–61
localization methods, 357
malaligned or crowded teeth, 351
overlap, avoiding, 351
tori, 353
vertical angulation, altering, 351, 353
Surgical materials, 294
Suture, 278
Symphysis, 184, 275
Système Internationale (SI), 15
T
Target, 27
Target-image receptor distance, 36–37, 38, 41–42
bisecting technique, 180
Target-object distance, 38
Target-surface distance, 41
Taurodontia, 296
Technique errors, 229–34
artifacts, 234
incorrect exposure factors, 233–34
incorrect positioning of image receptor, 229–31
incorrect positioning of tube head and PID, 232–33
poor definition, 234
Technique standards, 59
Teeth, radiographic appearance of, 277–78
Temporal bone, 274
Temporomandibular disorder (TMD), 365
Temporomandibular joint (TMJ), 372
Thermionic emission, 27
Threshold dose-response curve, 49
Thyroid collar, 65–66
Time intervals for performing tests, 242
Timer, 23
Time-temperature, 89
Tissues of the body, radiation exposure and, 51
TLD (thermoluminescent dosimeter), 69
Tomograph, 372
Tomography, 4, 372–74, 379
Tooth resporption, appearance of, 297–98
external resorption, 297, 298
idiopathic resorption, 297
internal resorption, 298
Topographical technique, 216
Tori, 353
Torus, 300
Torus mandibularis, 285, 353
Torus palatinus, 353
Total dose, 50
Total filtration, 62
Trabeculae, 277
Trabecular bone, 277
Tragus, 386
Transcranial radiograph (TMJ), 368
Transformer, 25
Transitional mixed dentition, 326, 334–36
Trauma, appearance of, 301
Triangulation, 317
Tube head (tube housing), 21, 22, 24
incorrect positioning of, 232–33
stability, 243, 244
Tube-shift method (buccal-object rule), 357, 358
Tube side, 75, 77
Tumors, appearance of
nonodontogenic, 300–301
odontogenic, 299–300
Tungsten, 27
Twinning (gemination), 296
INDEX 435
U
Ultraviolet waves, 10–11
Underdevelopment, 235
Underexposure, 233
United States Nuclear Regulatory Commission, 70, 71
U.S. Environmental Protection Agency (EPA), 116, 252
U.S. Food and Drug Administration (FDA), 116
Units of radiation, 15–16
absorbed dose, 16
dose equivalent, 16
effective dose equivalent, 16
exposure, 15
terms used for, 15
Universal precautions, 115
Useful beam, 28
V
Velocity, 12
Verbal communication, 140
Vertical angulation, 152–53
bisecting technique, 182, 185
bitewing examination, 206–7
children, radiographic techniques for, 330–33
occlusal radiographs, 218, 219
paralleling technique, 166
Vertical bitewing radiograph, 150, 198, 318
Vertical (angular) bone loss, 315–16
Victor CDX shockproof dental x-ray machine, 3
Viewbox, 87, 247, 268–70
Viewing radiographs, 268–70
equipment for, 268–70
interpretation vs. diagnosis, 268
sequence for, 269–70
Visual impairment, patients with, 341
Volt (V), 26
Voltage, 26
Voltmeter, 23
Voxel (volume element), 373
W
Walkhoff, Otto, 2–3, 4
Washing, in film processing, 84
Waste management service, questions to ask of, 259
Waste stream, 259
Waters radiograph, 367
Wavelength, 12
Weighting factor, 16
Wet reading, 89–90
Wheelchair bound patients, 341
White light fog, 237–38
White lines, marks, or spots
chemical contamination, 235
handling errors, 236, 237
Working radiograph, 91, 356
Written plan, 242
X
X-coordinate, 99, 100
“X Light Kills” (Rollins), 4
X-ray film. See Film, x-ray
X-ray machine monitoring, 243–44, 245
output consistency test, 243, 245
step-wedge, 243, 244
tube head stability, 243, 244
X-ray machines, 20–31
components of, 21–24
control panel, 22–24
digital radiography, 104
electricity and, 24–26
evolution of, 21
extension arm, 24
history of, 3–4
monitoring (See X-ray machine monitoring)
operation of, 28–29
tube head (tube housing), 24
x-ray beam and, 28
x-ray tube and, 26–28
X-rays, 2
discovery of, 2
interaction with matter, 13–15
production of, 13
properties of, 12–13
techniques, 5
X-ray tube, 26–28
anode, 27
cathode, 27
operation, summary of, 27–28
Y
Y-coordinate, 99, 100
Yoke, 24
Z
Zygoma, 274, 282, 395
Zygomatic arch, 274–75, 282
Zygomatic process, 282, 395
436 INDEX