Essentials of Dental Radiography

Essentials of Dental Radiography
for Dental Assistants and Hygienists

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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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