Atlas of Cone Beam Imaging

Library of Congress Cataloging-in-Publication Data
Miles, Dale A.
Atlas of cone beam imaging for dental applications / Dale A. Miles. — 2nd ed.
p. ; cm.
Rev. ed. of: Color atlas of cone beam volumetric imaging for dental applications / Dale A.
Miles. c2008.
Includes bibliographical references and index.
ISBN 978-0-86715-565-5 (hardcover)
eBook ISBN 978-0-86715-592-1
I. Miles, Dale A. Color atlas of cone beam volumetric imaging for dental applications. II.
Title.
[DNLM: 1. Stomatognathic Diseases–radiography–Atlases. 2. Cone-Beam Computed
Tomography–methods–Atlases. WN 17] 616.07’5722–dc23
2012036568
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Table of Contents
Preface to Second Edition
Preface to First Edition
Acknowledgments
1 CBCT in Clinical Practice
2 Basic Principles of CBCT
3 Anatomical Structures in Cone Beam Images
4 Airway Analysis
5 Dental Findings
6 Impacted Teeth
7 Implant Site Assessment
8 Odontogenic Lesions
9 Orthodontic Assessment
10 Orthognathic Surgery and Trauma Imaging
11 Paranasal Sinus Evaluation
12 Temporomandibular Joint Evaluation
13 Systemic Findings
14 Vertebral Body Evaluation
15 Selected Cases from Radiology Practice
16 Clinical Endodontics
17 Risk and Liability
Preface to the Second Edition
I am overwhelmed and somewhat humbled by the unexpected success of the
first edition of this atlas. I am also deeply grateful to the many colleagues
who have approached me at seminars to tell me that they keep this book
beside them when they are examining their cone beam volumes as well as to
the many others who have asked me to sign their copy of the first edition.
Obviously, the book has made an impact in this exciting new era of oral and
maxillofacial radiology.
In this updated second edition, I have used the term cone beam computed
tomography (CBCT) instead of cone beam volumetric imaging (CBVI). I still
believe that the more correct term for this modality is volumetric imaging.
However, as most of my radiology colleagues have pointed out, the term
CBCT is ensconced in the dental and medical literature, so I have decided,
somewhat reluctantly, to adopt the term myself. In addition to the minor title
change, I have added new cases to most chapters, developed a new section to
address anatomy in the small volume, and added three new chapters to
discuss applications for CBCT in endodontics, the risks and liabilities of
CBCT, and selected cases from my radiology practice. I believe that these
additions and updates have strengthened the book and made it even more
useful.
I am smart enough to know my limitations, and in this edition, I have
invited my first contributor, Dr Thomas McClammy*, a great endodontist
and a great friend. He has written chapter 16 about the use of CBCT in the
specialty of endodontics. As an early adopter, Dr McClammy did his due
diligence, agonized over the decision to purchase a CBCT machine, and then
plunged in. He has been like a kid in the proverbial candy store, and his
enthusiasm about this modality comes through as he explains its incredible
utility in his practice of endodontics.
Finally, some readers may question a radiologist attempting to address
liability issues arising from the use of CBCT. However, I feel very strongly
that some colleagues are setting themselves up for legal action by persisting
in looking at the CBCT volumes only to determine a suitable implant site,
and by neglecting the examination of the rest of the data or its referral to a
specialist. This is the profession’s standard of care when a task or diagnosis is
beyond our capability. Most of what I state in chapter 17 is common sense.
Nevertheless, I am taking this risk myself by addressing this concern directly.
I do it for my own peace of mind and to educate my colleagues.
I know the reader of this second edition will see these developments in
the book’s content as both necessary and exciting. Enjoy, and thanks again
for the support.
* Thomas V. McClammy, DMD, MS
Private Practice
Scottsdale, Arizona
Preface to the First Edition
Like any innovation in the dental profession, the availability of cone beam
volumetric imaging (CBVI) has preceded the understanding of its use. It
happened with panoramic imaging as it did with digital radiographic imaging.
The cone beam images in this atlas will educate dental professionals on how
to use CBVI technology to better visualize the diseases and disorders that
they encounter with their patients.
One aim of this atlas is to refresh the reader’s memory of anatomy. As
dentists we never “worked” in the axial plane of section after our anatomy
training; we have lived our lives in a world of plain films or digital images,
all in the format of 2D grayscale panoramic, intraoral, or lateral
cephalometric images. CBVI allows us to visualize patient anatomy and
pathology like never before. CBVI helps to reveal bony changes caused by
pathology. In addition, the level of anatomic detail in the 3D image sets
means that clinicians placing implants no longer have to experience anxiety
about whether they are placed correctly. CBVI allows us to determine the
precise location of the inferior alveolar nerve in relation to impacted
mandibular third molars, which improves preoperative planning and reduces
patient morbidity as well as our liability. At last, we can see out patients’
problems in a whole new manner—in 3D and color. I hope this book will
help you understand how CBVI can improve your clinical experiences and
the management of your patients’ treatment.
Acknowledgments
I am deeply appreciative to CyberMed USA and CyberMed International for
allowing me to continue to test their software product and to use it in my
practice. I happen to think that it is the premier software for examining cone
beam computed tomography image data. Mr Eusoon Han and the marketing
team at CyberMed USA work tirelessly to support the product and have
helped me understand the incredible tools within the software. Thanks to all.
Thanks once more to Prof C. Young Kim, the CEO of CyberMed
International for your product, your confidence, and your friendship. This
book would not be possible without your product and support.
A big thank you to Mr William Hartman of Quintessence for going the
extra mile with my requests, and to Ms Lisa Bywaters and Ms Bryn Grisham
for their editorial support.
Finally, love and special thanks to my wife, Kathryn, for her continued
support, love, confidence, sacrifice, and patience.
CBCT in Clinical Practice
Nothing has captured the dental profession’s imagination in the past few
years like the introduction of cone beam volumetric imaging (CBVI), which
is now referred to by most clinicians and even in the literature as cone beam
computed tomography (CBCT). I too now refer to the data volumes I receive
from clients as CBCT volumes, despite my opinion that CBCT images bear
no resemblance to traditional medical computed tomography (CT) scans
except in the display of the final product.
The process of image acquisition for CBCT machines is unlike traditional
medical CT scanners in that the patient is not usually supine, the image
gathered is in a voxel (volume element) format, the x-ray dose absorbed by
the patient is substantially lower, appointment availability is much easier, and
it is less expensive. In short, although this imaging modality produces
signicant data volumes like medical CT, it is different and vastly superior to
traditional CT data for specic dental applications.
Dentists and dental specialists continue to be amazed at the incredibly precise
and profound information produced by CBCT scans, and they are realizing
that the data they receive will influence their treatment decisions like no other
imaging modality used in the profession in the past 100 years. CBCT makes
clinical decision making easier and more precise, patient treatment decisions
more accurate, and visualization of the x-ray data more meaningful. Dentistry
is moving away from “radiographic interpretation” and into “disease
visualization,” and it could not have come at a better time.
Clinical Applications of CBCT
The applications for CBCT encompass most of the procedures clinicians
perform in their office. Some applications for CBCT are listed in Box 1-1;
examples of many of these applications are discussed in chapters 4 to 16.
Additional applications will undoubtedly follow as clinicians learn about and
begin to appreciate the incredibly beneficial data this imaging modality
delivers for improved treatment planning and clinical decision making.
The evolution of implant technology, the technical skills and training of
dental professionals, and the patients’ desire for more permanent and
predictable restorative solutions to missing teeth all ensure that implant
dentistry will remain the largest growth market for dental professionals and
commercial vendors for at least another decade. Within 5 years, the
reconstructed data in 2D/3D grayscale and color formats from CBCT
machines will become the standard of care for displaying patients’
radiographic information for presurgical implant site assessment, implant
placement, and follow-up radiographic assessment. CT, plain film imaging,
and digital imaging modalities will probably become obsolete, at least for
implant dentistry applications.
In recent years, the most rapid adoption of CBCT technology has been in
the endodontic community. Manufacturers of limited field of vision (FOV)
units have rigorously pursued the use of CBCT for endodontic imaging. In
addition, a position statement on the use of CBCT in endodontics was
developed jointly by the American Association of Endodontists (AAE) and
the American Academy of Oral and Maxillofacial Radiology (AAOMR) and
published in 2011.
1,2 More clinicians are discovering that CBCT data
provides tremendous advantages with its thin slices and precision in
endodontic imaging. For this application alone, sales of limited FOV
machines will continue to increase.
Another growing area for CBCT application is in the diagnosis and
treatment of obstructive sleep apnea (OSA). CBCT provides precision airway
assessment that can quantify the amount of airway opening as well as the
effects of different intraoral appliances. Treatment of OSA improves patient
quality of life while reducing the risk of cardiac complications related to
having an obstructed airway. This application of CBCT allows clinicians to
significantly improve patient systemic health. Construction of simple
intraoral appliances are essential for patients who have failed with continuous
positive airway pressure (CPAP) machines and have increased cardiac risk.
Considerations for CBCT
The rapid rate of adoption of this technology has been surprising. By the
summer of 2011, I had interpreted over 10,000 CBCT scans and the first
edition of this book was already out of print. Now I spend close to 80% of my
professional time interpreting CBCT scans and creating reports for clinicians
who use this technology. I practice my specialty of oral and maxillofacial
radiology both from my home in a dedicated radiology office environment as
well as while I travel to give lectures and consult. I can operate just as my
medical radiology colleagues do and practice my specialty from virtually
anywhere in the world because of global Internet access.
Just as there are many different CBCT models available on the market, I
receive the data volumes to interpret through many different avenues. Gone
are the days when we relied on 2D grayscale single images attempting to
represent 3D structures, viewed on light boxes under poor lighting
conditions, to help us make our clinical treatment decisions. It is now
possible to have 2D and 3D color “renderings” of each patient’s anatomy and
signs of clinical diseases/disorders.
Figure 1-1 shows this CBCT machine’s broad capabilities and power.
Whether you are considering purchase of a machine for image acquisition in
your practice or simply accessing this technology by requesting a scan, you
should consider the following important questions:
1. How much data (number of images) do you need?
2. How large an area do you wish to evaluate?
3. Do you simply need 2D grayscale information for your decision?
4. Does the diagnostic task really require a CBCT?
5. Does every patient require this type of imaging?
6. Are you comfortable diagnosing all of the data in the volume?
7. What is your risk of missing an important occult finding?
Fig 1-1 This 3D color reconstruction is 42 mm thick and shows bilateral
calcification of the stylohyoid complex as well as the airway, the hyoid
bone, and a cross section of the mandible.
The data volume vs the single image
Before I address these questions, it is very important to understand the size
difference between a data volume from a CBCT machine and traditional
static 2D grayscale images. Each periapical image in a computer is about 300
kB in size, and three of these static intraoral images would fill a 1-MB floppy
disk. A digital panoramic image is about 5 to 7 MB, so approximately 100
images could fit on a CD-ROM. By contrast, each CBCT data volume
acquired for a single patient can range from 100 to 250 MB. Only a few
patient scans would fit on an 800-MB CD-ROM. Even the so-called smallvolume machines provide much more anatomical information than we have
been accustomed to viewing and assessing (Fig 1-2).
Fig 1-2 Small-volume 3D color reconstruction of a 9-year-old patient with a
fractured mandible, rendered with Accurex (CyberMed International). The
fracture is easily identified in the anteroposterior view, and the 3D image
can be rotated 360 degrees to see the fracture in any orientation.
The impact of this data volume is huge, both literally and figuratively.
Several large-capacity computers or servers are necessary to store the
volumes. These data volumes should also be stored offsite via the Internet,
which requires high-speed Internet connection.
In addition, as a clinician, remember that you are responsible for all of the
information in a volume, whether you order or acquire it, and whether it is
for your own use or for a referral client. This tenet is still a source of
confusion within the profession and is sometimes made more confusing by
conflicting information provided by CBCT scanner manufacturers.
Chapter 16 is new to this edition and discusses the risk and liability issues
specific to CBCT volume data. The chapter is illustrated with multiple
examples of occult findings from volume data that, if missed, would have led
to patient harm and delayed treatment. Such oversights are unacceptable in
the dental profession, which has an implicit responsibility, like the medical
profession, to do no harm. No clinician can have a patient sign a form
absolving him/her from this important duty.
The responsibility for looking at the entire data volume is analogous to
looking at a single panoramic radiograph. No clinician would look at only
half of a panoramic radiograph; clinicians must look at the entire image.
CBCT data, although much more extensive, is no different, and if a clinician
cannot interpret the entire volume, referral to a specialist who can is
necessary. Although this at first seems to represent a fundamental paradigm
shift for all clinicians, it is really common sense and the standard of care that
we would use for any specialist referral. When a clinician is in doubt about a
finding, referral to a specialist is expected.
In 1999 the American Dental Association’s house of delegates voted to
accept the application for specialty recognition from the AAOMR to create
dentistry’s ninth specialty. Now clinicians have specialists in oral and
maxillofacial radiology to whom they can refer difficult cases.
In essence, this signals a move to the medical model of radiographic
imaging; that is, we are shifting the responsibility for the overall image
findings to a qualified radiologist after more than 100 years of clinicians
serving as their own radiology expert. Plain films and digital intraoral and
panoramic images will still be used for some diagnostic procedures, but
clinicians will probably need to enlist the services of an oral and
maxillofacial radiologist to look at patient CBCT data for occult pathology in
less familiar anatomical regions. It is both prudent and professional to do so.
Table 1-1 shows the reportable findings in 381 CBCT cases in a 1-year
period (March 2005 to March 2006).
Common CBCT concerns
How much data do you need?
This is a very difficult question to answer. Orthodontists or dentists who treat
orthodontic problems in their patients require much more diagnostic
information to assess a case and predict the outcome. Currently, orthodontic
assessment usually involves intraoral images; panoramic, cephalometric, and
sometimes hand-wrist radiographs; and plaster casts. Casts are mentioned
because, in the future, clinicians will create 3D casts from the radiographic
data in the cone beam scan. So the ability to acquire all the image data needed
in one single imaging procedure offers orthodontists a very distinct advantage
over current methods. Of course, the clinician does not always need all of
those images on an 8-year-old patient at the initial record visit because it is
unlikely that brackets will be placed on this patient until a few years later.
Dentists should think about the information they need for each diagnostic
task before they take or order a CBCT scan. This practice of applying
selection criteria is only now becoming standard practice.
4
How large an area do you wish to evaluate?
Some CBCT machines acquire larger data volumes than others. Data
acquisitions range from volumes of 4 x 4 cm2
to 22 x 22 cm2
. Figure 1-3
demonstrates the differences in size and region of the head corresponding to
these volumes. Not all clinicians need to see the entire skull or would wish to
be responsible for the occult pathology that might be encountered in the data
volume (slice). Radiologists and others wishing to assess the patient’s data
volume must scroll and be able to detect pathologic findings in as many as
512 slices (images) in three orthogonal planes (axial, sagittal, and coronal).
Most clinicians are not comfortable with this task or do not have the time to
look at such a large amount of information.
Fig 1-3 Comparison between the results from a small-volume machine
versus those from a large-volume machine. (top) Axial slice of the middle of
the condylar head. (bottom) Larger area at approximately the same level.
Both volumes contain anatomical structures and cells, such as the middle
ear, mastoid cells, airway, and vertebral bodies, all of which would require
evaluation to determine whether pathology was present.
Do you simply need 2D grayscale information for your
decision?
It may not be necessary to have 3D color information for decision making at
all. The reconstruction of a panoramic image from a 250-MB data volume
requires anywhere from 4 to 70 times the amount of x-rays needed for a
traditional panoramic film or digital image. Therefore, a 2D digital panoramic
radiograph from a full-featured panoramic machine can often suffice for the
preliminary visualization of the patient’s dentition, bone, condyles, and
related anatomy (Fig 1-4).
Fig 1-4 Digital panoramic radiograph of a developing mixed dentition.
Except for the slightly ectopic resorption of the primary canine roots, the
dentition is developing normally. This child would not need a cone beam
scan to make this determination. The x-ray dose from the CBCT scan would
not be justified when this panoramic image would suffice.
Does the diagnostic task really require CBCT?
The clinician must determine if CBCT is even necessary for a particular
diagnostic task. Applications and clinical indications to help with this
determination are discussed further in later chapters. Detection of caries does
not require a cone beam scan. Periodontal bone loss can be evaluated by
well-positioned bitewing and periapical radiographs. Some underestimation
of the alveolar architecture may occur in plain film or digital intraoral
radiography, but this task again does not require CBCT’s thin slice data to
see bone problems. If a patient exhibits systemic disease or a set of risk
factors that could accelerate the bone loss associated with periodontal
disease, a cone beam scan may be indicated to detect the disease earlier or
monitor the treatment success. However, noninvasive, diagnostic
immunoassay tests performed on saliva could detect disease processes even
earlier without exposing the patient to any x-rays. The clinician should
carefully consider the precise indications for this imaging modality and fully
expect the images produced to result in a positive finding that could affect a
treatment outcome. Although x-ray doses are lower for any CBCT machine
than traditional medical CT, not every patient will require a CBCT scan.
4
Does every patient require this type of imaging?
The short answer is an emphatic no. Again, the clinician must consider the
application and prescribe this imaging test only for those patients who would
actually benefit from a precise measurement for an implant site or a better
outcome prediction based on the data volume acquired. There are enough
reasons to use CBCT.
5,6
Income generation is not one of them, nor is the
production of “prettier images.”
Are you comfortable diagnosing all of the data in the
volume?
Most clinicians are not comfortable with viewing radiographic data in an
axial plane. We have rarely seen anatomical structures or pathology in a thin
slice format that displays a plane of information of 1 mm (or less). Consider
the image in Fig 1-5 and ask yourself if you can identify the structure
indicated by the white arrow.
Fig 1-5 Try to identify the structure designated by the arrow, but do not be
surprised if you do not recognize it; most dentists have never seen this
structure in this plane of section. Note the total opacification of the right
maxillary sinus. As is conventionally done in medical CT and with
panoramic radiographs, we are viewing the patient from the foot end, so the
patient’s right side is the left side of the image. The indicated structure is the
coronoid process.
What is your risk of missing an important occult finding?
There is a lot of interest and some confusion about who is responsible for the
image data in the CBCT volume. Is it the owner of the machine? Is it the
referring doctor? Is it the specialist whose office has the machine and
provides the radiographic data? The short answer is yes. Everyone in these
various scenarios is liable. The dentist, the dental specialist who only
provides images, and the radiographic imaging laboratory providing services
for the referring clinician would all be named in a lawsuit if a significant
finding were missed that resulted in harm to the patient. The only solution is
to look at all the images in all planes of section and record any abnormality.
Then refer this patient, with their images, for a consultation with the
appropriate clinician. If you do not feel capable of detecting and interpreting
the data, or if you do not have the time, you should probably consider using a
reading service, medical or dental, to review the image data set and report the
findings. There are always many reportable findings in CBCT scans.
1
References
1. American Association of Endodontists; American Acadamey of Oral and
Maxillofacial Radiography. AAE and AAOMR joint position statement.
Use of cone-beam-computed tomography in endodontics. Pa Dent J
(Harrisb) 2011;78:37–39.
2. American Association of Endodontists; American Academy of Oral and
Maxillofacial Radiology. Use of cone-beam computed tomography in
endodontics Joint Position Statement of the American Association of
Endodontists and the American Academy of Oral and Maxillofacial
Radiology. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
2011;111:234–237.
3. Miles DA. Clinical experience with cone beam volumetric imaging: Report
of findings in 381 cases. US Dent 2006;Sep:39–42.
4. US Department of Health and Human Services, Public Health Service,
Food and Drug Administration; American Dental Association, Council on
Dental Benefit Programs, Council on Dental Practice, Council on
Scientific Affairs. The selection of patients for dental radiographic
examinations. Revised 2004. Available at:
www.ada.org/sections/professionalResources/pdfs/-
topics_radiography_examinations.pdf. Accessed 14 March 2012.
5. Ludlow JB, Davies-Ludlow LE, Brooks SL. Dosimetry of two extraoral
direct digital imaging devices: NewTom cone beam CT and Orthophos
Plus DS panoramic unit. Dentomaxillofac Radiol 2003;32:229–234.
6. Danforth RA, Miles DA. Cone beam volume imaging (CBVI): 3D
applications for dentistry. Ir Dent 2007;10(9):14–18.
Basic Principles of CBCT
The method of obtaining the patient’s data volume in cone beam computed
tomography (CBCT) differs signicantly from that of conventional medical
computed tomography (CT). In medical CT scanning (previously termed
CAT [computed axial tomography]), the patient’s region of interest (ROI),
such as the head or abdomen or other body part, is selected. As the x-ray
source rotates around the ROI 60 times per minute, multiple sensors,
consisting of either a gas or scintillator material (most commonly cesium
iodide), detect the x-ray beam. The patient must be moved into the scanner a
known distance in the z-plane. It is this distance—perhaps a centimeter, a half
centimeter, or in cases where high resolution is required, as little as 1
millimeter—that determines the slice thickness. This type of image
acquisition is very precise. The data acquired are voluminous and, in turn, the
patient’s absorbed x-ray dose is also very large. A typical CT scan for a
maxillary implant site assessment may have a radiation dose as high as 2,100
µSV, equivalent to the dose from about 375 panoramic lm or digital images.
1
Image Acquisition
Unlike conventional CT, CBCT uses a narrow cone-shaped beam to rotate
194 to 360 degrees around the patient (Fig 2-1). The sensor is either an image
intensifier (II) that is coupled to either a charge-coupled device (CCD) (Fig 2-
2) or complementary metal oxide semiconductor (CMOS), or a thin film
transistor (TFT) flat-panel type image receptor (Fig 2-3). The II is an older
technology that was developed to improve the viewing of fluoroscopic
images in the operating room during surgery. In the past, the bright lights of
the operating room made it a poor environment for surgeons to view
radiographic film, necessitating a device to “intensify” the resulting images.
The major disadvantage of the II system is distortion at the periphery of its
images. The image pattern appears as a sphere or “ball” and thus the edge
regions are not ideal.
Fig 2-1 (left) Traditional medical CT detector array with x-ray source
rotates 360 degrees around the patient about 60 times per minute. The
thickness of each image slice is determined by the distance (usually 1.0 to
100.0 mm) the patient is moved through the gantry. This exposes the patient
to a large dose of x-rays. (right) A cone beam device, using the cone-shaped
beam, rotates around the patient. The exposure factors are similar to those
used for exposing traditional dental radiographs, so the x-ray dose to the
patient is substantially reduced.
Fig 2-2a In the II system, a curved input phosphor, usually censium iodide,
introduces geometric distortion, which must be compensated for by
software. The phosphor coating will degrade over time, so the II will have to
be replaced eventually—sometimes in as few as 3 or 4 years. This older
imaging system is being replaced by flat-panel displays that offer the many
advantages of a direct digital capture.
Fig 2-2b This II system is stylish but large because of the II configuration.
The x-ray source is on the left of the patient. The detector system is on the
right side. (Courtesy of Sirona USA.)
Fig 2-3a The flat-panel detector (FPD) system is a simple digital capture
system that uses only an x-ray source and a digital detector to capture the
image volume. The devices made with this type of system are much less
bulky and therefore more ergonomic.
Fig 2-3b This FPD system is the ProMax 3D. (Courtesy of Planmeca USA.)
Flat-panel detectors (FPDs) are the newest image receptors for solid-state
large-area arrays.
2 These panels are expensive but offer some advantages
over the older II systems including less distortion, wider scale of contrast,
and elimination of veiling glare.
Compared with medical CT, CBCT doses are much lower, only about 40
to 500 µSv.
1 The method of acquiring images is very different, and the
exposure factors (kV and mA) are much lower. CBCT machines use either a
single FPD or an II (scintillator or phosphor screen) coupled to a series of
CCDs. Table 2-1 illustrates the various current CBCT devices that are
available. More information about CCDs is available at the LearnDigital
website.
3
Several CBCT machines that were available in 2008, including the Iluma
(Imtec) and the CBMercuRay (Hitachi), are no longer marketed in North
America. However, manufacturers continue to introduce new machines and
improve their products. For example, in North America, the supine units like
the original NewTom 9000 (QR Verona) have largely been replaced by
machines used in mobile CBCT units, such as the NewTom VGi (QR
Verona). In addition, many manufacturers have introduced units with variable
fields of vision (FOVs) or units with either an FPD or an II.
Pixel vs Voxel Information
A pixel is a picture element. It is a square that measures between 20 and 60
µm in size. The size of the receptor area is the same whether it resides in an
intraoral device, the TFT screen, or the II and solid-state combination device.
CCDs and CMOSs for intraoral sensors are megapixel arrays, meaning that
each is one million pixels or more. The larger flat panels, of course, use many
millions of pixels.
A voxel is a volume element. This describes a pixel that has a third side; it
is really a cubed array. In CBCT this cube is made up of isotropic pixels with
equal sides. In conventional medical CT, the pixel is nonisotropic, meaning
that two sides are equal, but the third (z-plane) is a selectable width,
anywhere from 0.5 to 10 mm or more. Figure 2-4 illustrates this difference.
Fig 2-4 Traditional medical CT scanners use pixels. The slice thickness is
determined by gantry movement. The thickness, or z-plane, is determined
by the operator. CBCT devices gather the volume information directly using
voxels or cubes with known dimensions (typically 0.15 to 0.6 mm). All
CBCT slice thicknesses in the resulting image are much thinner than slices
created by medical CT devices.
Voxel Size and Image Resolution
Some manufacturers have touted voxel size as the sole measure of image
resolution and, by extension, image quality. While voxel size is important, it
is not the only parameter that affects image quality. Several studies have
addressed this point.
6–8 Pauwels et al
6 designed a cylindric prototype made
from polymethyl methacrylate that could be scanned to assess the image
quality parameters of various CBCT machines. In the results of the study, the
author stated that “the voxel size itself provides only a crude prediction of
spatial accuracy.”
6
Some types of assessment, like those for endodontic applications or
implant site assessment, may require the ability to select a very small voxel
size. Implant site assessment necessitates image capture using a voxel size of
0.2 mm or less. On the other hand, orthodontic records, airway analysis, and
temporomandibular joint (TMJ) assessment do not usually require very small
voxel sizes. Regardless, almost every contemporary CBCT unit offers
variable voxel parameters so that operators can select a voxel size ranging
from 0.076 to 0.125 mm.
Factors affecting image quality and resolution
Clinicians must identify the particular diagnostic abilities that they need from
their CBCT units. When planning to invest in a CBCT unit, clinicians must
consider many parameters in addition to voxel size in order to select the
CBCT unit that will best meet their needs:
• Detector type. II versus FPD.
• Head positioner. The most stable is a three-point configuration seen in Fig
2-3b.
• Exposure factors. The higher the milliamperage, the more photons available
to the detector. However, the trade-off is a higher radiation dose.
• Bit depth of the detector system. Affects the quality of the image
reconstruction.
• Reconstruction algorithm. Inherited from the manufacturer.
• Focal spot size at the anode. Just like that found in standard intraoral x-ray
machines.
Radiation Dose
Although the dose from CBCT machines is significant, it is much less than
that of traditional medical CT scans. Recent data from Ludlow et al
1
estimates that the absorbed x-ray dose from a CBCT examination for a
procedure like an implant site assessment is between 1% and 25% the dose
absorbed from a medical CT scan. This means that many dentally specific
evaluations can be performed much more safely with CBCT than with
medical CT. Thus, when a patient is being considered for any of the
applications cited in Box 1-1, a clinician cannot justify a medical CT
procedure since its radiation dose would greatly exceed that of a CBCT
evaluation. As more machines become available, more dose data are sure to
follow. CBCT will become the imaging modality of choice for most dental
tasks requiring 2D/3D information for clinical decision making.
Legal Concerns
A few of my colleagues believe, or have been advised by CBCT machine
manufacturers, that they can simply have their patient sign a consent form
stating that the dentist is not sufficiently trained to interpret the data beyond
the “dental bases” and is not to be held liable if a significant finding is
missed. Actually, both the owner of the CBCT machine and the referring
clinician have a co-responsibility to make sure the entire data volume is
reviewed for occult pathology. If they are not comfortable interpreting the
volume, it is up to them to make sure a qualified individual reads the volume
and reports the findings to them. There is no ignoring this responsibility.
Consider a lawyer questioning a machine owner on a witness stand. Here
is the hypothetic conversation, but I assure you it is a reasonable line of
inquiry.
Lawyer: Doctor X, was Miss Y present in your office on June 30, 2006,
for an appointment to have a CBCT examination performed?
Doctor X: Yes.
Lawyer: And Doctor X, was that CBCT examination actually performed?
Doctor X: Yes.
Lawyer: And Doctor X, did you charge a fee for that CBCT examination?
Doctor X: Yes.
Lawyer: Doctor X, what was the fee you charged Miss Y for said CBCT
examination?
Doctor X: Four hundred twenty-five dollars.
Lawyer: Doctor X, did you collect that fee from Miss Y?
Doctor X: Yes.
Lawyer: Well Doctor X, wouldn’t you call that “practicing dentistry”?
Doctor X: Yes, but …
Lawyer: Doctor X, just answer the question yes or no.”
Doctor X: Yes.
As this fictional scenario demonstrates, when a clinician performs a
procedure, charges a fee, and collects that fee, it is considered practicing
dentistry. There is no other recourse than to ensure the images in the data
volume are reviewed— all 512 images in each of the three orthogonal planes:
axial, sagittal, and coronal. If a clinician does not feel qualified to do this, it is
essential to have that volume read by an oral and maxillofacial radiologist or
a medical radiologist. See chapter 17 for further discussion of risk and
liability with cone beam imaging.
References
1. Ludlow JB, Davies-Ludlow LE, Brooks SL. Dosimetry of two extraoral
direct digital imaging devices: NewTom cone beam CT and Orthophos
Plus DS panoramic unit. Dentomaxillofac Radiol 2003;32:229–234.
2. Floyd P, Palmer P, Palmer R. Radiographic techniques. Br Dent J
1999;187:359–367.
3. Miles DA. LearnDigital website. Available at: http://www. learndigital.net.
Accessed 19 March 2012.
4. Hirsch E, Silva M. Radiation doses from different conebeam-ct devices.
Presented at the 11th Congress of the European Academy of DentoMaxillo-Facial Radiology, Budapest, 27 Jun 2008.
5. Brooks SL. Answer to question #6120 submitted to “Ask the Experts.”
Health Physics Society website. Available at:
http://hps.org/publicinformation/ate/q6120.html. Accessed 19 March 2012.
6. Pauwels R, Stamatakis H, Manousaridis G, et al. Development and
applicability of a quality-control phantom for dental cone-beam CT. J Appl
Clin Med Phys 2011;12:245–260.
7. Loubele M, Jacobs R, Maes F, et al. Image quality vs radiation dose of
four cone beam computed tomography scanners. Dentomaxillofac Radiol
2008;37:309–318.
8. Loubele M, Maes F, Schutyser F, et al. Assessment of bone segmentation
quality of cone-beam CT versus multislice spiral CT: A pilot study. Oral
Surg Oral Med Oral Pathol Oral Radiol Endod 2006;102:225–234.
Anatomical Structures in Cone Beam
Images
To discern a potential problem in the cone beam computed tomography
(CBCT) data volume, the clinician or radiologist must examine multiple
slices in three planes of section: axial, sagittal, and coronal. While clinicians
are quite familiar with many structures in the sagittal plane (since it is similar
to periapical, bitewing, panoramic, and cephalometric orientations), they are
not as familiar with these same structures as viewed in the coronal or
especially the axial plane. To illustrate this point, I would ask you to look
back at Fig 1-5 and recall the difficulty of interpreting thin slice data in a
plane of section most of us have not seen since dental school.
This chapter presents many anatomical structures in the three planes of
section as grayscale images, supported in most cases by thicker 3D slices,
slabs or volume images to help the reader orient themselves and reconstruct
the structures in the mind’s eye. No attempt was made to illustrate all
possible just structures; the chapter instead focuses on those that are
commonly seen by dentists and dental specialists to help them relearn
anatomical detail that may be long forgotten. Because many of the structures
involve several bones, they are repeated in various views and planes of
section.
Maxillary structures should be very familiar to all of us, especially in the
lateral or sagittal view. Although these bones can be described separately, we
will see them in this chapter as they appear clinically—joined together to
make walls, spaces, and structures that we must recognize to understand the
3D changes one might encounter during an examination of CBCT volume
data. When possible, these structures will be identied as they relate to one
another.
The first part of this chapter illustrates anatomy as seen in a large old of
vision (FOV). The second part focuses on these same anatomical structures
as seen in a small FOV.
Anatomy in the Large FOV
Structures identified in Figs 3-1 to 3-33 include the antra, incisive foramen
and canal, nasal fossa, nasal conchae, nasolacrimal canal, pterygoid
plates/processes, pterygoid hamulus, and styloid and mastoid processes. In
each section the structures are identified in the axial plane first (both thin and
thick sections), followed by similar views in the sagittal and coronal planes.
In some figures, we include all three planes to show the clinician and student
how a specific structure or anomaly is oriented between the three planes. In
most instances, the images start with a section through a recognizable part of
the anatomy such as the temporomandibular joint (TMJ) condyles.
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Fig 3-3 A 21.5-mm slice from the palatal to midportion of condyle.
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Fig 3-5 A 2.2-mm slice through the mandbiular fossa (middle of condyle).
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Fig 3-7 A 100-mm slab rendering (lateral pole of condyle).
Fig 3-8 A 60-mm slab rendering (middle of condyle).
Fig 3-9 This 13.2-mm slice serves as a pseudoradiograph of the posterior
region of the condyles.
Fig 3-10 A 0.15-mm slice through the middle ear region.
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Fig 3-12 A 100-mm slab reconstruction through the mandibular fossa.
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Fig 3-14 A 33.2-mm slab through the condyles.
Fig 3-15 A 100-mm slab rendering through the mandibular fossa showing
the airway.
Fig 3-16 A 100-mm slab rendering through the mandibular fossa.
Fig 3-17 A 0.15-mm slice through middle of sphenoid sinus.
Fig 3-18 A 0.15-mm slice through the middle of pterygoid plate.
Fig 3-19 A 0.15-mm slice through the middle of pterygoid plates.
Fig 3-20 A 0.15-mm slice through the posterior region of maxillary sinus.
Fig 3-21 A 0.15-mm slice through the middle of maxillary sinus.
Fig 3-22 A 0.15-mm slice through the anterior region of maxillary sinus.
Fig 3-23 A 32.3-mm slab through the anterior region of maxillary sinus.
Fig 3-24 A 26.9-mm slice through the middle of condyles.
Fig 3-25 A 53.2-mm slab through the posterior ramus.
Fig 3-26 A 53.2-mm slab through the middle of ascending ramus.
Fig 3-27 A 53.2-mm slab through the anterior region of the maxillary sinus.
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Fig 3-29 A 100-mm slab rendering through the region of the condyles.
Fig 3-30 A 69.9-mm slab rendering through the midregion of the maxillary
sinus, also showing the airway.
Fig 3-31 A 69.9-mm slab rendering through the posterior region of the
maxillary sinus, also showing the airway.
Fig 3-32 A 69.9-mm slab rendering through the anterior region of the
sphenoid sinus, also showing the airway.
Fig 3-33 Multiplanar reconstructed images showing axial (a), sagittal (b),
and coronal (c) views through the middle of the mandibular condyles.

Anatomy in the Small FOV
Anatomy is anatomy. There is no such thing as “small volume” anatomy.
However, CBCT machines are sold with different FOV sizes ranging from as
small as 38 x 50 mm to as large as 200 x 200 mm. Manufacturers have
perpetuated a belief among clinicians that the use of a small FOV CBCT
machine eliminates or greatly reduces diagnostic responsibility. This is true
to some extent. However, even an area as small as 4 x 4 cm, when positioned
over the condyle or used to image an impacted mandibular third molar, may
capture some very important anatomical structures. For example, both the
internal carotid artery and internal jugular vein lie within a half centimeter of
the medial pole of the condylar head. This section features images taken by a
CBCT unit with a small FOV that follow the path of the internal carotid
artery from the area of the medial condyle to the parasellar region.
Figures 3-34 to 3-40 illustrate that even small FOV CBCT units capture
data and images that are significant. A clinician must be familiar with as
many anatomical structures as possible to be able to delineate any potential
disparity from normal anatomical spaces and foramina.
Fig 3-34a The foramen for the internal carotid artery (top left, arrow) in its
position medial to the mandibular fossa and medial condylar pole. The
beginning of the path of the carotid artery toward the sella region is visible
(bottom right, arrows).
Fig 3-34b Continuation of the internal carotid artery (arrows).
Fig 3-34c A widening of the canal for the internal carotid artery (arrows).
Fig 3-34d As the scan moves superior to the condylar head, the upward turn
of the internal carotid artery adjacent to the sella turcica and sphenoid sinus
is visible (bottom right, arrows).
Fig 3-35a 3D color reconstruction taken through the neck of the condyle
showing the opening for the internal carotid artery (arrow).
Fig 3-35b The entire canal is outlined, including where the artery ascends
(black arrow), the canal itself (white arrows), and the opening near the
sphenoid sinus (orange arrow) where the artery ascends once more.
Fig 3-35c This view shows the sphenoid sinus (white arrow) and the place
adjacent to the sinus where the internal carotid artery ascends adjacent to the
sella turcica (orange arrow).
Fig 3-35d 3D reconstruction at the level of the superior portion of the ramus
where it joins the condylar neck. The canals for both the internal jugular
vein (white arrow) and the internal carotid artery (orange arrow) are visible.
Fig 3-36a The Endoscopic tool allows 3D reconstruction of the internal
carotid artery canal from inside the canal. The small red x near the condyle
in the scan on the left is in the vicinity of the stapes (arrows) shown in the
3D reconstruction on the right.
Fig 3-36b Further down the canal, the 3D reconstruction on the right shows
the stapes (upper arrow) and the central portion of the canal for the internal
carotid artery (lower arrow).
Fig 3-36c A view from inside the canal proceeding further toward the
region of the sphenoid sinus.
Fig 3-37a A view slightly more inferior on the ramus showing both the
foramen spinosum (left arrow) and the foramen ovale (right arrow). See if
you can identify the openings for the internal carotid artery and internal
jugular vein in this image.
Fig 3-37b A similar view of these two foramina seen at a more superior
level near the midportion of the condyle.
Fig 3-38 Multiplanar views showing the opening for the foramen ovale
(arrows) in the coronal, sagittal, and axial planes as well as a 3D color
reconstruction. Note the proximity of this foramen to the condylar region.
Fig 3-39 Similar multiplanar reconstructions of the area showing the
approximate location of the internal carotid artery (arrows) near the
sphenoid sinus.
Fig 3-40a An axial slice taken by a small FOV CBCT unit to evaluate the
left TMJ. The sequence begins with the view of the midroot region of the
maxillary left second molar.
Fig 3-40b A slice from a slightly superior level showing the relationship of
a small portion of the dens axis to the lateral mass of the arch of C1 (atlas).
Fig 3-40c A slightly more superior view showing the origin of this styloid
process, a small region of the dens axis, and the foramen in C1 to transmit
the vertebral artery.
Fig 3-40d A slice at this level shows structures that are more recognizable,
such as the condyle, nasal septum, and medial and lateral pterygoid plates.
In most cases, the data set for the contralateral TMJ complex will be imaged
for comparison. Thus, the clinician needs to look at all of these structures
from the opposite side in the fossa of Rosenmüller. Obliteration of this
space can indicate a space-occupying lesion.
Fig 3-40e At a level near the top of the condyle, some of the foramina in the
base of the skull become visible, including the foramen spinosum and the
foramina for the internal carotid artery and internal jugular vein.
Fig 3-40f Structures in this axial slice may not be familiar to most dental
clinicians. The carotid canal is well identified as it nears the parasellar
region, and structures of the temporal bone, such as the tympanic membrane
and basal turn of the cochlea, now become apparent.
Fig 3-40g More superiorly, more temporal bone structures become visible,
including the malleus, vestibule, and cochlea. Neuroradiologists can identify
up to 70 structures in the temporal bone alone. It is beyond the scope of this
atlas to identify all structures within the temporal bone.
Fig 3-40h This thin slice coronal reconstruction shows some of the
structures in the parasellar region, including the foramen rotundum and
pterygoid canal.
Fig 3-40i A slightly more posterior view shows other structures of the floor
of the skull, such as the foramen ovale.
Fig 3-40j This view at the level of the neck of the condyle shows the
cavernous sinus and foramen spinosum.
Moreover, when a small FOV CBCT unit is used to image a condyle, an
impacted third molar, or the maxillary sinus for presurgical implant
assessment, there will be structures contained within this smaller data set that
may initially confuse you. Taking the time to relearn the anatomy outlined in
this chapter and in other resources will increase the comfort and competence
in assessing small FOV scans.
Airway Analysis
While a continuous positive airow pressure (CPAP) appliance is still
considered the first-line treatment for severe sleep apnea,
1 mild to moderate
cases may be treated effectively with either a mandibular advancement device
(MAD) or a tongue retraining device (TRD).
2The MAD, which looks similar
to a sports mouth guard and is the most common dental device for sleep
apnea, directs the mandible forward and down slightly to keep the airway
open during sleep. The TRD is a dental splint that holds the tonque in one
place during sleep to keep the airway as open as possible.
Dentists who make appliances for patients experiencing sleep apnea have
a signicant role in the management of this disorder. The assessment of the
patient’s airway is an integral part of the management strategy. There appears
to be no better way to visualize the airway than by employing cone beam
computed tomography.
Fig 4-1 Airway Narrowing
Fig 4-1a Sagittal image at 0.15 mm shows narrowing of the airway in a
young patient with enlarged adenoids (arrows).
Fig 4-1b The airway is reconstructed in grayscale (40 mm thick) to
resemble a typical cephalometric image.
Fig 4-1c Sagittal image in 3D color reconstruction (40 mm thick) shows
airway narrowing.
Fig 4-1d A 3D color reconstruction shows the airway without the spinal
column.
Fig 4-1e A slice only 5 mm thick allows for airway assessment in 3D color.
Fig 4-2 Patent Airway
Fig 4-2a An axial view in 3D color shows the patent airway space.
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Fig 4-2c A 3D color reconstruction of a sagittal slice 17.2 mm thick shows
the airway. There is no restriction of the volume in this airway.
Fig 4-2d A coronal view in 3D color is reconstructed in a slice 11.5 mm
thick, representing the beginning of the nasopharyngeal airway. All other
airway spaces such as the maxillary antra, nasal cavity, and ethmoid air cells
also appear patent.
Fig 4-2e A 3D color reconstruction of a coronal slice 30 mm thick
represents the beginning of the nasopharyngeal airway. Note that the molars
on each side of the maxillary arch are now visible.
Fig 4-2f Sagittal view of the airway in 3D color, reconstructed in a slice
11.6 mm thick, representing the beginning of the nasopharyngeal airway.
All other airway spaces such as the maxillary antra, nasal cavity, and
ethmoid air cells also appear patent.
Fig 4-2g Sagittal view in 3D color, reconstructed in a slice 30.1 mm thick.
This represents the entire 3D volume of the patent airway.
Fig 4-2h This 3D color reconstruction of an axial slice at 30.1 mm thick
shows the entire 3D volume of the airway from the nasopharyngeal opening.
Note also the patent maxillary sinuses.
References
1. Bradley TD, Logan AG, Kimoff RJ, et al. Continuous positive airway
pressure for central sleep apnea and heart failure. N Engl J Med
2005;353:2025–2033.
2. Kushida CA, Morgenthaler TI, Littner MR, et al. Practice paramerters for
the treatment of snoring and obstructive sleep apnea with oral appliances:
An update for 2005. Sleep 2006;29:240–243.
Dental Findings
Even after patients undergo comprehensive clinical and radiographic
examinations, their cone beam computed tomographic data volumes referred
for radiographic interpretation often reveal incidental dental ndings; that is,
dental diseases and conditions are found that could not be appreciated
through plain lm imaging alone. In some cases, even 2D digital images
(intraoral or panoramic) are insuf cient to detect some dental lesions.
Fig 5-1 Periapical Lesions
Fig 5-1a A 2D reconstruction of a conventional panoramic image. The
periapical lesion on the maxillary left lateral incisor is barely discernible and
could be missed. Note also the mucous retention cyst in the right antrum.
Fig 5-1b A thin slice (0.15 mm) 2D pseudopanoramic image. The periapical
lesion on the maxillary left lateral incisor is easily apparent in this thin
section.
Fig 5-1c A 2D maximum intensity projection (MIP) image of the same
patient.
Fig 5-1d A 3D color panoramic reconstruction of the same patient shows
cortical perforation.
Fig 5-1e A 3D full-volume reconstruction shows the same defect (arrow),
with the grayscale multiplanar images on the right. The clinician can toggle
between the images to completely visualize the lesion.
Fig 5-2 Mesiodens
Fig 5-2a A conventional panoramic image. The mesiodens was not very
distinguishable.
Fig 5-2b The pseudopanoramic image does not reveal the mesiodens, even
in a thin slice.
Fig 5-2c The MIP image, though distorted in the anterior region, shows the
mesiodens clearly.
Fig 5-2d An axial slice shows the mesiodens (arrow) in relation to the
beginning of the nasal cavity.
Fig 5-2e A 3D reconstruction of the mesiodens area suggests eruption of the
mesiodens into the right nasal cavity. This reconstruction is accomplished
by using the Cube tool in the OnDemand 3D software (CyberMed
International).
Fig 5-2f A 2D grayscale coronal image with a partial view of the problem
with the nasal cavity and mesiodens. The clinician would have to “stack”
many slices to recognize the true extent of the lesion. In the 3D color images
in Figs 5-2e and 5-2g, the lesion is easily visualized.
Fig 5-2g A 3D slab (11.0 mm thick) rendering of the mesiodens from the
coronal image in Fig 5-2f.
Fig 5-2h The Dental function in the OnDemand 3D software, normally used
for assessing implant sites, can also create cross-sectional images of the
mesiodens.
Fig 5-2i 3D color rendering of selected images from Fig 5-2h shows the
nasal cavity and maxillary sinus. Note that the thin layer of bone separating
the mesiodens from the nasal cavity is more apparent in this reconstruction.
Impacted Teeth
Impacted teeth are a common problem. Orthodontists and oral and
maxillofacial surgeons spend a lot of time assessing tooth position and
eruption patterns and managing patients referred from general dentists who
have usually seen these impactions on intraoral or panoramic radiographs.
Permanent canines erupting abnormally are common, as are horizontally
impacted mandibular third molars. Even supernumerary teeth are a common
enough anomaly to require additional radiographic assessment. Cone beam
computed tomography (CBCT) is the most appropriate way to perform this
assessment for preoperative planning and orthodontic management. It is
likely that CBCT will become the standard of care for the assessment of all
impactions in the near future.
Fig 6-1 Maxillary Canine and Mandibular Third Molar
Fig 6-1a A panoramic image, reconstructed from the cone beam data
volume, represents the type of image that would serve for the initial
assessment of the missing canine. There is no way to determine the correct
orientation (facial or palatal position) from this panoramic image. The
primary canine is retained. The permanent canine is impacted horizontally.
Fig 6-1b The same image as Fig 6-1a, using a maximum intensity projection
view. The canine appears to be anterior to the central and lateral incisors.
Fig 6-1c The cone beam multiplanar reconstructed (MPR) axial image
reveals the correct position of this impacted canine. It is posterior to the
central and lateral incisors and the retained primary canine.
Fig 6-1d The cone beam MPR sagittal image reveals the position of this
impacted canine (arrow) relative to the left lateral incisor.
Fig 6-1e The cone beam MPR coronal image reveals the position of this
impacted canine as posterior to the central and lateral incisors.
Fig 6-1f A 3D color reconstruction shows the palatal elevation caused by
the impacted canine (arrow).
Fig 6-1g A 3D color reconstruction (18.3 mm thick) shows the canine
position (arrow) unobstructed by bony anatomy.
Fig 6-1h A 3D color reconstruction (18.3 mm thick) formatted in a “4-
view” series shows the canine position unobstructed by bony anatomy at the
level of the incisal edges of the maxillary and mandibular anterior teeth.
Fig 6-1i A 3D color reconstruction (18.3 mm thick) formatted in a “4-view”
series shows the canine position unobstructed by bony anatomy at the level
of the midregion of the pulp canals of the maxillary premolars.
Fig 6-1j A panoramic image of a vertical impaction of the mandibular right
third molar reveals that the inferior alveolar nerve canal passes close to the
apex.
Fig 6-1k A pseudopanoramic image (5.0 mm) provides a sharper view of
the vertical impaction of the mandibular right third molar. The inferior
alveolar nerve canal now appears to touch the apex of the tooth.
Fig 6-1l A 3D reconstructed view of the region shows a vertical impaction
of the mandibular right third molar, with the inferior alveolar nerve touching
the apex of the tooth (arrow).
Fig 6-1m Axial, sagittal, and pseudopanoramic images with the nerve canal
drawn in and a reference line at the midroot level. At this location, the crosssectional image (top right) reveals that the inferior alveolar nerve (red oval)
does not touch the mandibular third molar (arrow).
Fig 6-1n Axial, sagittal, and pseudopanoramic images with the nerve canal
drawn in and a reference line at the level of the root apex. The crosssectional image (top right) reveals that the inferior alveolar nerve (red oval)
does touch the apex of the mandibular third molar (arrow).
Figs 6-1o and 6-1p Cross-sectional images with a reference line at the root
apex region confirm that the inferior alveolar nerve (red ovals) does touch
the very apex of the tooth (arrows).
Fig 6-2 Maxillary Third Molars
Fig 6-2a This axial image shows impactions of the maxillary third molars.
Note the root canal therapy on the second molars, as well as some minor
mucosal thickening in the left maxillary sinus (arrow).
Fig 6-2b A pseudopanoramic image (0.16 mm thick) shows the impactions
seen in Fig 6-2a. This thin section is not in the correct plane to show the
maxillary anterior teeth; however, these could be imaged by scrolling
anteriorly through the arch to the appropriate plane of section.
Fig 6-2c A sagittal image (left) shows impaction of the maxillary left third
molar; the Cube tool (right) is used to render the 3D image of the maxillary
second and third molars. Note the detail of the occlusal surface. This is a
small-volume image taken using the ProMax 3D machine (Planmeca) and
imaged with N-Liten 3D software (Planmeca).
Fig 6-2d A sagittal slice shows the same tooth impaction but with the buccal
bone imaged for preoperative evaluation. Detailed anatomy is again
visualized. This image was reconstructed using the ProMax 3D machine and
N-Liten 3D software.
Fig 6-2e This sagittal image shows the impaction of the maxillary right third
molar with the buccal bone imaged for preoperative evaluation. The
maxillary sinus is colored violet. This image was reconstructed using the
ProMax 3D machine and N-Liten 3D software.
Fig 6-2f A 3D color rendering shows the same impaction as in Fig 6-2e
without extra colorization of air space.
Fig 6-2g The image area from Fig 6-2f is rendered in 3D and color and
rotated to show the occlusal surface of the tooth (right). Because of the
communication of this tooth with the oral cavity, these pit depressions
(arrow) may be caries lesions. Image rendered using the ProMax 3D
machine and N-Liten 3D software.
Fig 6-3 Maxillary Left Quadrant
Fig 6-3a The arrow in this axial slice identifies the impacted mandibular
right third molar.
Fig 6-3b The maxillary left third molar is impacted, though the apices
appear normal in this coronal slice.
Fig 6-3c This reconstructed maximum intensity projection image shows the
vertical impaction of the maxillary left third molar and the horizontal
impaction of the mandibular left third molar.
Fig 6-3d 3D color reconstructed view showing the position of the maxillary
left third molar. In this image, extraction does not look problematic.
Fig 6-3e When the Nerve tool is used, it is clear that the inferior alveolar
nerve touches the apices of the impacted mandibular right third molar.
Fig 6-3f The apices of the maxillary left third molar still do not appear to be
a problem in these views.
Fig 6-3g A 3D color reconstructed view shows some of the apical region.
Fig 6-3h A rotated view from a superior position shows that the buccal
apices are severely dilacerated and fused. The configuration of these roots,
which could not be identified in the multiplanar 2D grayscale images, would
make extraction difficult. Only the 3D reconstruction reveals the true
situation and prevents an unpleasant surprise at the time of extraction.
Fig 6-3i A thin sagittal slice shows an unusual impaction of the maxillary
left first molar (arrow).
Fig 6-3j A thin coronal slice showing the mesial aspect of the maxillary left
first molar (arrow).
Fig 6-3k A slightly posterior coronal slice shows a minor dilaceration of the
distobuccal root (arrow).
Fig 6-3l The Cube tool (left) was used to create a 3D color reconstruction
(right) that shows the divergence and dilaceration of the mesiobuccal and
distobuccal roots (arrow) of the maxillary left first molar. The structure is
fused to the apical third.
Fig 6-3m A 20-mm reconstructed view shows the position of the impactions
in the maxillary left quadrant. Even if the maxillary left second molar were
extracted, the maxillary left first molar could not erupt because of the
dilacerated apices revealed in the 3D color reconstruction.
Implant Site Assessment
Probably the most common use for cone beam computed tomography
(CBCT), after endodontic and orthodontic evaluation, is preoperative implant
site assessment. When a clinician is placing multiple implants for an
overdenture, use of CBCT for site assessment is indispensable. However,
cases involving multiple implants and horizontal anchorage of the surgical
guide are not nearly as common as cases involving single tooth loss. With the
precision of CBCT, any clinician wishing to perform surgery for an implant
or restorative procedure can easily work on preoperative planning without
referring all surgical procedures to a specialist. The illustrated cases are not
intended to establish protocol for single implant site assessment, but rather
demonstrate the precision with which measurement and location can be
performed using appropriate CBCT software.
Importance of a Radiographic Stent and
Marker
The importance of using a radiographic stent with a nonmetallic marker for
implant site location cannot be overstated. Radiographic stents, which help to
precisely locate the desired bone receptor site, have been around for many
years.
1 The clinician provides the history, casts, and clinical findings
(including preliminary 2D radiographic information) and is the operator who
places or directs the placement of the implant. Providing a stent and a precise
description of the most desirable location is essential to allow the radiologist
and/or technician to take precise measurements of length, width, and
angulation for the implant site. If the clinician is analyzing the site, a marker
will invariably assist the evaluation. Placing a radiopaque marker at the
clinically determined location makes all subsequent steps much easier.
Software is available to perform measurements to within about 0.1 mm.
These measurement tasks are ideally performed at the site indicated by the
radiographic marker. Metal markers and barium pastes should not be used
because of their inevitable artifacts and image degradation. Metallic balls
such as copper balls may be suitable, but gutta-percha is probably the ideal
marker material. An article describing the simple construction of a
radiographic stent is available at the LearnDigital website.
2
Fig 7-1 Creating a Radiographic Stent
Fig 7-1a A clinical cast is shown in a surveyor with a coffee stir stick as
stylus. Gutta-percha will be placed into one half of the stick to provide a
radiopaque marker that will not produce scatter artifacts in the volume data.
Fig 7-1b The clinical cast is shown with the processed acrylic stent and
coffee stir stick with gutta-percha inside. A hot-wax instrument is then used
to cut off the excess gutta-percha, and the marker area is covered with new
cold-cure acrylic. Retention is provided during image acquisition by the
incisal/occlusal imprint. (Fig 7-1 courtesy of Dr Ron Shelley, Glendale,
AZ.)
Fig 7-2 Canine Site Assessment
Fig 7-2a A sagittal view (left) and a 3D color reconstruction (right) show
the metallic marker used to locate the ideal implant site.
Fig 7-2b With a marker in the implant site, the length, width, and even
angulation can be measured precisely in preparation for implant selection.
Fig 7-2c A close-up of the proposed implant site shows the ridge width and
bone height within one-tenth of a millimeter.
Fig 7-3 Premolar Site Assessment
Fig 7-3a Panoramic image of proposed implant site for the maxillary right
second premolar. With this type of 2D image it is not possible to measure
the precise distance to the maxillary sinus or the width of the alveolar bone
from the facial wall to the palatal wall.
Fig 7-3b The CBCT program identifies the precise implant site location,
ready to measure, in the cross-sectional view.
Fig 7-3c The CBCT program shows the measurement of the implant site in
the cross-sectional view.
Fig 7-4 Molar Site Assessment
Fig 7-4a The CBCT program shows the precise location of the inferior
alveolar nerve, as well as the reference line at the proposed implant site
location. (upper right) The nerve canal has been automatically labeled in red
after the arch and canal have been drawn using the simple program tools. To
stay in the center of the alveolar ridge and engage the cortical bone, an
implant measuring 4.5 × 10 mm may be used safely. Implant selection based
on 2D panoramic imaging alone would have resulted in a longer implant
and possible perforation into the submandibular fossa because of height
distortion in the radiograph.
Fig 7-4b Here, the cortex of the bone is easily visualized using the Dental
function and 3D tools. The shape of the submandibular fossa is also
apparent. (upper right) The two red dots demonstrate the change in position
of the nerve canal from the posterior end of the slice (upper dot) to the
anterior end of the slice (lower dot).
References
1. Danforth RA, Miles DA. Cone beam volume imaging (CBVI): 3D
applications for dentistry. Ir Dent 2007;10(9):14–18.
2. Miles DA, Shelley RK. Pre-surgical implant site assessment: Part I–Precise
and practical radiographic stent construction for cone beam CT imaging.
LearnDigital website. Available at:
http://www.learndigital.net/articles/2006/presurgical_stent.pdf. Accessed
11 July 2012.
Odontogenic Lesions
Although many odontogenic cysts and tumors are rare, the application of
cone beam computed tomography (CBCT) to characterize these lesions is
invaluable for preoperative planning and clinical management.
Fig 8-1 Supernumerary Tooth
Fig 8-1a An 18-year-old white woman was referred to an oral and
maxillofacial imaging facility in Seattle, Washington, for CBCT evaluation
with respect to a suspected supernumerary tooth. The maxillary third molars
had not yet erupted. The axial section shows the maxillary left third molar
and associated supernumerary tooth.
Fig 8-1b The sagittal section shows these teeth in a more recognizable view.
Fig 8-1c A 3D grayscale reconstruction shows the orientation of the
maxillary left third molar and supernumerary tooth.
Fig 8-1d A 3D color reconstruction shows the orientation of the molar and
supernumerary tooth in relation to the bone.
Fig 8-1e A 3D color reconstruction shows the orientation of the molar and
supernumerary tooth in relation to soft tissue structures such as the
maxillary sinus and partial airway.
Fig 8-1f A 3D color reconstruction shows the orientation of the molar and
supernumerary tooth in relation to anatomical structures and facial soft
tissues. The black box over the eyes is necessary to preserve the anonymity
of the patient, since the facial detail is so remarkable.
Fig 8-1g In this 3D color panoramic reconstruction of the patient, note how
single midline anatomical structures such as the hyoid bone and spine are
still projected twice because of the image reconstruction process. The
maxillary left third molar is marked (arrow).
Fig 8-2 Simple Bone Cyst
Fig 8-2a A 10-year-old Hispanic girl presenting a large radiolucent lesion in
the anterior mandible was referred to the oral and maxillofacial imaging
facility in the orthodontic department at the University of California, San
Francisco, for CBCT evaluation. A panoramic-like image reconstructed
from the cone beam data volume reveals a large, well-defined, circular
radiolucency with a cortical border. No internal calcification or root
resorption is apparent. There appears to be some remodeling of the inferior
cortex of the mandible.
Fig 8-2b A thin axial slice at the level of the hyoid bone (arrow) reveals the
expansile nature of the lesion not seen in the previous panoramic image.
Fig 8-2c A thin sagittal slice shows thinning of the anterior mandible and
some expansion.
Fig 8-2d A sagittal slab (60.0 mm thick) rendered in 3D color shows the
lesion and soft tissue outlines. Note also the transparent airway and
paranasal sinus regions.
Fig 8-2e An axial slab (60.0 mm thick) rendered in 3D color showing lesion
and soft tissue outlines. Note also the transparent airway and paranasal sinus
regions.
Fig 8-2f A full 3D color rendering shows the lesion and soft tissue outlines.
Note the apparent perforation of the anterior cortical bone. This is a
pseudoperforation caused by the slice thickness. The cortex, though thinned,
is intact, as seen in the previous images.
Fig 8-2g A full 3D color rendering shows the lesion and soft tissue outlines.
Again, note the apparent perforation of cortical bone. This image is fully
rendered, so the “perforation” actually comes from the image processing.
The opacity and transparency functions may have been manipulated
incorrectly. All 2D and 3D image data must be examined to make a correct
assessment.
Fig 8-3 Nasopalatine Duct Cyst
Fig 8-3a A 58-year-old white woman was referred for implant site
assessment for replacement of the right mandibular second molar. The
panoramic radiograph was not provided, but a typical reconstruction
simulates what it would have shown; the reconstructed “panoramic” image
fails to reveal the existence of the nasopalatine duct cyst in the anterior
maxilla. This is a good example of the kind of occult pathology found in
CBCT data volumes by oral and maxillofacial radiologists.
Fig 8-3b An axial image shows the size and irregular margins of the palatal
cyst (arrows), indicating expansion.
Fig 8-3c A 3D color reconstruction suggests possible perforation of the
palatal cyst. Recall that, as shown in Fig 8-2g, this apparent bone loss may
be only an effect of the image processing.
Fig 8-3d A coronal slice demonstrates the expansile nature of the lesion.
Note that the lesion has already eroded the floor of the nasal fossa
bilaterally.
Fig 8-3e A coronal 3D color rendering further suggests perforation of the
buccal and possibly the palatal bones by the lesion.
Fig 8-3f A sagittal slice demonstrates expansion and possible erosion of the
inferior region of the palate, since the opening from the foramen (arrows)
appears larger than normal.
Fig 8-3g The Implant mode can be used to examine the central area of the
lesion in all three planes of section.
Fig 8-4 Odontogenic Keratocyst
Fig 8-4a A 53-year-old white man was referred to Case Western Reserve
University School of Dental Medicine in Cleveland, Ohio, for evaluation of
an impacted third molar. No information was provided to the radiologist
other than a request to study the data volume. There was no referral
comment on the prescription form about a suspected cyst. This is a
pseudopanoramic reconstruction slice (0.15 mm). At the time of this
evaluation, the Preferences section of the software had been programmed to
display the image in a reverse format; that is, with the patient’s left side on
the left (white arrow).The lesion actually surrounds the mandibular right
third molar.
Fig 8-4b An axial view shows the pericoronal nature and expansion of the
lesion, resulting in remodeling of the lingual cortex.
Fig 8-4c Use of the Nerve Drawing tool in the Implant mode to determine
the relationship of the tooth and lesion to the inferior alveolar canal. Orange
represents the nerve outside the plane of section. Green represents the nerve
in the particular plane of section.
Fig 8-4d By selecting the Cube tool in the software, this image is
automatically reconstructed in a 3D color rendering. The clinician or
operator can also change the coloration by selecting presets, which can be
created and stored in the program by assigning different colors and opacity
and transparency values to particular voxels.
Fig 8-4e By selecting the Cube tool, the image can be rotated in 3D to
demonstrate the occlusal surface anatomy.
Fig 8-4f A similar, but isolated view of the image from Fig 8-4e has been
rotated to view the inferior extent of the lesion in 3D color. Note the linear
resorptive pattern of the mandibular right second molar here and in Fig 8-4e.
Fig 8-4g The OnDemand 3D server-based platform software (CyberMed
International) also has an Endoscope tool that allows the visualization of
even more detail of this lesion. The cauliflower-like radiopaque object
posterior to the ramus is a calcified lymph node.
Fig 8-4h Applying the Endoscope tool and rotating the image displays the
occlusal surface even more precisely.
Fig 8-4i An enlarged, isolated image captured from the right side of Fig 8-
4h. This is done within the program with a Capture tool. All images
captured can be stored as compressed jpeg, tiff, or bitmap images. The size
of a compressed jpeg image is often less than 400 kB. Note that there is no
loss of image quality, even in this enlarged view.
Fig 8-5 Pericoronal Radiolucency
Fig 8-5a An 8-year-old Asian girl was referred to Advanced Dental Imaging
in Salem, New Hampshire, to evaluate a radiolucency in the right anterior
maxilla. The axial view through the midroot section of the maxillary
dentition reveals a large, expansile, well-defined pericoronal radiolucency
around the maxillary right canine, which was impacted and displaced
superiorly against the lateral wall of the right nasal fossa. The radiolucency
has a definitive cortical border.
Fig 8-5b Another axial view of the pericoronal lesion at the level of the
inferior portion of the condylar heads.
Fig 8-5c The Cube tool applied to the image section in Fig 8-5b results in a
3D color image of the developing first premolar in its deviated orientation.
The view is of the developing root structure from the facial side. The lesion
has displaced the first and second permanent premolars. The maxillary right
first premolar had completed only about one-third of its root formation. A
linear resorption pattern is seen on the roots of the primary canine and
primary first molar.
Fig 8-5d A more superior slice at the level of the lateral pterygoid plates
(white arrows).
Fig 8-5e An axial slice shows the lesion at the level of the developing
permanent canine crown. The lesion obviously extends to the maxillary
sinus region. The white arrow indicates the left antrum.
Fig 8-5f A typical 9 × 9 series, like traditional computerized tomography,
shows the axial views at 1.0-mm slices from the level of the developing
premolar crowns to the incisal tip of the maxillary right canine.
Fig 8-5g Another 9 × 9 series, continuing the axial views at 1.0-mm slice
thickness, shows extension into the maxillary sinus and the relationship of
the maxillary right canine to the root structure. Note the distinct cortical
margin.
Fig 8-5h A coronal section through the midcrown region of the ectopic first
premolar demonstrates the buccal expansion of the lesion. There are no
apparent internal calcifications, even at this slice thickness of 1.0 mm.
Fig 8-5i A more posterior coronal section shows the cortical definition of
the lesion’s border (arrow).
Fig 8-5j A 3D color reconstruction shows the developing first premolar
crown in precise relation to the incisal tip of the developing maxillary right
canine. The lesion extends from the right lateral incisor region through the
maxilla and into the maxillary right sinus midway up the nose. Posteriorly,
it reaches the first molar region.
Fig 8-5k A sagittal view shows the displacement of the canine and premolar
as well as extension into the maxillary sinus region.
Fig 8-5l The Arch tool defines the central plane of the maxilla to create a
pseudopanoramic image to visualize the internal contents of the lesion.
Fig 8-5m This maximum intensity projection image demonstrates the
difficulty in orienting the structures correctly from a panoramic-type view.
Fig 8-5n A reconstructed panoramic image at a thickness of 20.0 mm. Note
that this type of image would be deficient for any clinician to fully
characterize the lesion. The cortical margin is not appreciated, and the
precise orientation of the first premolar is not discernible.
Differential diagnosis
Although the lesion contained no discerrnible internal calcifications, the most
likely odontogenic lesion would be an adenomatoid odontogenic tumor. The
sex of the patient, location of the lesion, resorptive pattern, and tooth
displacement suggest this type of lesion. Additional possible diagnoses would
include an odontogenic keratocyst and an ameloblastic fibroma. Since an
ameloblastic fibroma behaves like a fibroma and rarely recurs, it can be
treated much more conservatively than an ameloblastoma. Incisional biopsy
prior to surgical removal was indicated to determine the precise histology of
the lesion for preoperative planning.
Fig 8-6 Mandibular Radiolucency
Fig 8-6a A 25-year-old white woman was referred to the Northwest
Radiography imaging center in Bellevue, Washington, for evaluation of a
lesion in the left posterior mandible. An axial slice shows a large, solitary,
well-defined expansile lesion with a cortical outline in the inferior portion of
the left mandible. There is no apparent perforation, but the cortex is
significantly thinned in this slice. One or two opacities are seen within the
lesion.
Fig 8-6b This coronal section confirms both the expansion of the lesion and
the thinning of the lingual cortex (arrow). The lesion is close to the molar
roots of the mandibular left first molar, which had previously undergone
root canal therapy.
Fig 8-6c This slice (0.15 mm) is a pseudopanoramic image showing the
anteroposterior extent of the lesion from the mandibular left canine to the
region of the third molar. The cortical border undulates around the second
premolar, first molar, and second molar. Note the small diffuse radiopacities
within the lesion at its inferior margin, as well as the displacement of the
inferior alveolar nerve.
Fig 8-6d The Cube tool was used to visualize the perforation of the buccal
cortex by the lesion in a 3D color view.
Fig 8-6e The lingual cortex in this patient also appears to be perforated. The
small opacity seen at the apex of the first molar represents some endodontic
fill material.
Fig 8-6f The Cube tool is used to create a 3D color image of the lingual area
and internal region of the lesion.
Fig 8-6g In this software, the clinician or radiologist can apply presets
(combinations of colors, opacities, and transparencies) to the histogram
region of selected tissues. In this patient, these presets have revealed a thin
soft tissue layer similar to a cyst lining around the molar apex and over the
bony enostosis at the inferior cortical margin.
Fig 8-6h A 3D color reconstruction of the same lesion from the lateral view.
Fig 8-6i The Arch and Nerve tools are used (left) to define the central plane
of the mandible and locate the inferior alveolar nerve (green line), as well as
(right) to create a cross-sectional image of the lesion. The vertical blue
reference line on the cross-sectional slice shows where the inferior alveolar
nerve (red dot) begins to dip below the lesion at its posterior border.
Fig 8-6j The Nerve tool illustrates the displacement of the inferior alveolar
nerve below the lesion.
Fig 8-6k (bottom panel) The reference line (orange arrow) within the
panoramic slice in a 3D color reconstruction reveals where the inferior
alveolar nerve (orange line) touches the area of enostosis. The blue arrow
points to the perforation of the buccal cortex.
Orthodontic Assessment
This section is not intended to present traditional orthodontic case workups;
instead, it simply demonstrates a few cases where cone beam volumetric
imaging (CBVI) information would help a clinician visualize the primary
case problems. No analyses are presented or suggested.
Fig 9-1 Eruption of Mandibular Permanent Teeth
Fig 9-1a A 7-year-old boy was referred to an imaging service in Seattle,
Washington, because of an unusual presentation of erupting mandibular
permanent teeth. A reconstructed pseudopanoramic image shows a possible
problem in the right anterior region of the mandible.
Fig 9-1b Even this maximum intensity projection (MIP) image does not
accurately demonstrate the mandibular problem. A supernumerary right
lateral incisor is suggested. The left lateral incisor appears to be “twinned”
or possibly fused to another extra tooth.
Fig 9-1c Instead of the fused tooth suggested in Fig 9-1b, the left lateral
incisor is actually a normal tooth. Fig 9-1b had an arch curve selected that
was too wide, which resulted in an inaccurate reconstruction. The axial and
sagittal views show a normal lateral incisor.
Fig 9-1d A 3D color reconstruction showing the anterior region reveals that
the mandibular right central incisor has erupted with an abnormal rotation.
Fig 9-1e A 3D color reconstruction in a profile configuration helps the
clinician visualize the problem.
Fig 9-1f A 3D color reconstruction in a profile configuration is created on
the left side for comparison.
Fig 9-1g A 2D grayscale sagittal view shows an unusual shape to the sella
turcica (blue arrow). The patient has no known endocrine or genetic
abnormality. The finding, while reportable, is inconsequential in this case.
Fig 9-1h A 2D grayscale sagittal view shows the development of the clivus
(blue arrows). This is a normal finding at this stage, but is never seen in the
conventional panoramic views used by orthodontists.
Fig 9-2 Palatal Impaction
Fig 9-2a This is a case of a palatal impaction of a canine in a 23-year-old
white man with retained primary molars. A temporary anchorage device had
been employed to obtain traction in a previously unobtainable location. A
2D grayscale axial view shows the palatally impacted maxillary right
canine.
Fig 9-2b A 3D color reconstruction of the axial view shows the anchorage
device.
Fig 9-2c This pseudopanoramic reconstruction slice (0.15 mm) shows the
canine, with its bracket, near the midline. Note the impacted maxillary left
third molar in this plane.
Fig 9-2d In a panoramic reconstruction including the impacted tooth, the
actual bracket is barely visible.
Fig 9-2e A 3D color panoramic reconstruction shows the impacted canine
and retained primary molars.
Fig 9-2f A 3D color reconstruction reveals the position of the canine relative
to the lateral incisor apex. Some transparency was used to show this
relationship.
Fig 9-2g A slab 3D color rendering (approximately 40 mm) in the axial
plane uses transparency to show canine position.
Fig 9-2h A 3D color reconstruction viewed from the foot end was created
for the entire volume and shows the condyle/ fossa relationships.
Fig 9-3 Facial Asymmetry
Fig 9-3a A 28-year-old white man was referred to the Northwest
Radiography imaging center in Bellevue, Washington, for radiographic
evaluation of his facial asymmetry and Class III malocclusion as part of his
orthodontic records workup. In this panoramic image, the maxillary right
teeth are not in the focal trough because of the patient’s cross-bite. Note the
shadow of thickened mucosa in the left antrum.
Fig 9-3b A panoramic MIP image provides a view of the cross-bite, as well
as the overerupted maxillary left third molar.
Fig 9-3c This 3D color panoramic reconstruction is even better than Fig 9-
3b for showing the cross-bite and Class III tooth relationships.
Fig 9-3d The Cube tool (left) renders a selected portion of the mandible to
show the ectopic position of the mandibular right second premolar from the
lingual aspect (right).
Fig 9-3e The Ortho Skeletal tool shows the tooth relationships from the
lateral (top left and right) and facial (bottom right) views.
Fig 9-3f The 3D Dentition tool uses the patient data to show the occlusion
from the palatal surfaces.
Fig 9-3g The 3D Skin tool in the OnDemand 3D software (CyberMed
International) shows the patient’s asymmetric facial outline.
Fig 9-3h The cross-bite and midline deviation of the patient’s mandible
suggest right side hyperplasia.
Fig 9-3i and 9-3j Comparison views confirm that the right side of the
patient’s mandible (left) is enlarged relative to the left side of the mandible
(right).
Orthognathic Surgery and Trauma
Imaging
Since preoperative planning is best accomplished with accurate information
about the morphology of the bony structures to be realigned, cone beam
computed tomography (CBCT) is ideal for these cases. 2D and 3D grayscale
and color information can accurately identify the anatomical architecture
beneath a patient’s soft tissue. Postoperatively, the screws, plates, implants,
and the surgical outcomes can also be assessed. Even with the presence of
scatter artifacts from the metallic materials often used, the images acquired
from the data are remarkable.
Fig 10-1 Facial Asymmetry: Preoperative/Orthodontic Evaluation
Fig 10-1a This patient has significant facial asymmetry. The right ramus
appears shorter than the left. There is a right posterior cross-bite from the
canine to the second molar and a significant midline deviation to the right
side as well.
Fig 10-1b The shortened right ramus is confirmed on this 3D color
panoramic reconstruction. A shortened condylar neck is also visualized.
Fig 10-1c A maximum intensity projection (MIP) image of the panoramic
reconstruction from Fig 10-1b. The distorted image of the cranium is due to
the large-volume machine data.
Fig 10-1d A typical panoramic reconstruction displays the calcified,
elongated stylohyoid ligament on the patient’s right side. This can also be
seen in the 3D color panoramic reconstruction in Fig 10-1b. This image
shows the shorter right ramus as part of the facial asymmetry, but it is much
less graphic than in Fig 10-1b.
Fig 10-1e During radiologic evaluation, a subchondral cyst and subchondral
sclerosis were discovered on the left condylar head (arrow). This finding
could impact the outcome of the proposed orthognathic surgery.
Fig 10-1f A coronal section from the data volume confirms the condylar
changes.
Fig 10-1g The thin slice pseudopanoramic image also confirms the condylar
cyst (arrow). This was not visualized on the panoramic reconstruction.
Fig 10-1h This 3D color reconstruction (20 mm) best reveals the
hypoplastic right condyle and neck, yet another component contributing to
the facial asymmetry.
Fig 10-1i Preoperative view of the patient’s right side.
Fig 10-1j Preoperative view of the patient’s left side.
Fig 10-2 Mandibular Fracture: Preoperative Evaluation
Fig 10-2a A 32-year-old American Indian woman was referred to an
imaging center at an oral and maxillofacial surgeon’s office in South Dakota
for evaluation of a suspected mandibular fracture. These slices show a leftside anterior mandibular fracture with slight displacement of the fragments.
Fig 10-2b A reconstruction of the patient’s right condyle from the lateral
view shows no fracture present.
Fig 10-2c A reconstruction of the patient’s left condyle from the lateral view
shows no fracture present.
Fig 10-2d This 3D color reconstruction from the facial view shows a
fracture with displaced segments.
Fig 10-2e Another 3D color reconstruction shows the fracture from the
inferior view. Note the second fracture line nearer to the midline.
Fig 10-2f A third 3D color reconstruction shows the fracture from the
lingual aspect. Here, the true extent of the lower portion of the fracture can
be appreciated.
Fig 10-2g Another fracture, located more posteriorly on the right side, has
caused the tooth to dislodge.
Fig 10-2h A 3D color reconstruction shows the fracture from the facial view
in the second molar region. This fracture apparently extends through the
tooth socket.
Fig 10-2i A 3D color reconstruction shows the fracture from a posterior
view in the second molar region. This fracture extends through the inferior
mandibular border and submandibular fossa to the tooth socket.
Fig 10-2j A 3D color reconstruction shows the position of the inferior
alveolar nerve (orange line) relative to the fracture lines.
Fig 10-2k A 3D color reconstruction in a thickened cross section (top right)
shows the position of the inferior alveolar nerve (red dot) in relation to the
second molar.
Fig 10-3 Chin Advancement: Postoperative Evaluation
Fig 10-3a A 38-year-old white woman was evaluated postoperatively for
healing following orthognathic surgery to advance her chin. This panoramic
reconstruction shows the condylar positions and gross occlusal
relationships. Note the discontinuity of the sections of the anterior mandible.
Although this is an acceptable panoramic image, this particular
reconstructed plane of section does not show the complete anterior maxilla.
Fig 10-3b The panoramic image displayed as an MIP image shows more
detail regarding the positions of the surgical plates and screws. The
occlusion is shown more precisely, but the anterior mandible is somewhat
distorted.
Fig 10-3c A 3D color reconstruction in a panoramic mode details the exact
appearance of the anatomical structures. Unfortunately, there are some
scatter artifacts from the metallic objects. This reconstruction was done at a
thickness of 30 mm. If a thicker slab rendering had been performed (at a
thickness of 50 to 60 mm), then the right zygoma would have been
displayed as nicely as the left.
Fig 10-3d A 3D color reconstruction of the entire skull details the
postoperative symmetry. Only a very slight midline deviation remains.
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Fig 10-3f Right lateral view of the 3D color reconstruction with transparent
soft tissue overlay to reveal the final esthetic result.
Fig 10-3g Left lateral view of the 3D color reconstruction of the entire skull.
Fig 10-3h Left lateral view of the 3D color reconstruction with transparent
soft tissue overlay to reveal the final esthetic result.
Fig 10-4 Mandibular Advancement: Postoperative Evaluation
Fig 10-4a A white woman was referred to an imaging center for
postoperative evaluation of a procedure to advance her entire mandible and
correct a facial asymmetry. In this thin slice pseudopanoramic
reconstruction showing the condyles, it is impossible to visualize the
surgical devices completely.
Fig 10-4b A panoramic view has been rendered in a thicker slice to see
more detail. Now it is possible to discern the surgical stabilization bar in the
left side of the mandible. Note that the length of the left ramus appears to be
much shorter than that of the right ramus.
Fig 10-4c The MIP view shows the occlusal detail and condylar fossa
relationships. The bony asymmetry has improved substantially.
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Fig 10-4e The Cube tool is used to show detail of the surgical screw
positioned on the patient’s right side.
Fig 10-4f The surgical screw in Fig 10-4e is viewed from the lingual aspect.
The position of the stabilization bar on the left side (arrow) starts to become
visible as well.
Fig 10-4g The area of the Cube tool is widened to show the entire right side
of the mandible.
Fig 10-4h The area of the Cube tool is widened to show the entire left side
of the mandible.
Fig 10-4i A 3D color reconstruction of the patient’s right side demonstrates
the surgical outcome.
Fig 10-4j A soft tissue rendering of the patient’s right side.
Fig 10-4k A 3D color reconstruction demonstrates the surgical results on
the patient’s left side.
Fig 10-4l A soft tissue rendering of the patient’s left side.
Fig 10-4m Note how the left mandibular angle flares out in this
anteroposterior view.
Fig 10-4n The soft tissue overlying the left mandibular angle in this
rendering reveals a slight but acceptable asymmetry.
Fig 10-4o An image taken from Waters projection shows the bony
structures of the patient.
Fig 10-4p The soft tissue is slightly enlarged over the stabilization bar
(arrow).
Fig 10-4q A right-side profile view of transparent soft tissue over bone
reveals the surgical site.
Fig 10-4r A transparent soft tissue profile on the left side also provides a
view of the surgical site.
Fig 10-4s A transparent soft tissue anteroposterior view over bone shows
the tracheal area. Note the calcification of the superior thyroid cartilage
(arrows).
Paranasal Sinus Evaluation
Every dentist has treated a patient with toothache pain for which acute or
chronic maxillary sinusitis is found to be the cause only after a thorough oral
examination rules out an odontogenic origin. Furthermore, patients
experiencing orofacial pain symptoms often require clinicians to evaluate
headaches that may be caused by paranasal pathology. Even if the sinus
involvement is suspected, how many times have clinicians underestimated a
pansinusitis because only the maxillary sinuses could be imaged? Cone beam
computed tomography (CBCT) is an exceptional way of imaging the
paranasal sinus region in toto.
Fig 11-1 Inflammation from Root Fragment
Fig 11-1a An axial section at the level of the maxillary first molar apices
reveals an inflammatory change in the left antrum (arrows).
Fig 11-1b A sagittal section shows the radiographic marker over the
extraction site of the left second premolar. Note the small uniform mucosal
thickening over the apical area (arrow).
Fig 11-1c A sagittal section shows mucosal thickening over the extraction
site, as well as a root tip containing endodontic fill material (arrow).
Fig 11-1d A coronal section shows mucosal thickening around the root tip.
The root tip and fill material are just barely visible in this orientation.
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Fig 11-1f A 3D color reconstruction shows the root tip of the first molar and
its relation to the mesial root of the second molar.
Fig 11-1g A 3D color slab rendering (approximately 40 mm) shows the root
tip. The space between the antral floor (arrow) and the root tip is where the
inflammatory material would be. However, the margin of the reactive
material can also be seen superior to the root tip of the extracted first molar
as labeled.
Fig 11-1h A 3D color slab rendering (approximately 40 mm) shows the root
tip of the first molar by using presets with different colors assigned to voxel
transparency and opacity values.
Fig 11-2 Mucous Retention Cyst
Fig 11-2a An axial slice through the midregion of the sinuses reveals
inflammatory change around the developing apices.
Fig 11-2b An axial slice through a more superior region of the maxillary
antra shows the classic dome-shaped appearance of a mucous retention cyst,
usually seen in a panoramic or lateral image.
Fig 11-2c The dome shape of the mucous retention cyst is also visible
arising from the floor of the left antrum in this coronal slice.
Fig 11-2d Another coronal slice shows the lesion getting smaller as the slice
transects a more posterior region of the maxillary antra.
Fig 11-2e A panoramic reconstruction from the data volume demonstrates
the usual appearance of a mucous retention cyst (arrow) seen in this mode.
Fig 11-2f A pseudopanoramic reconstruction from the data volume shows
the lesion more precisely because of the thin slice (0.15 mm) presentation.
Fig 11-2g In this 3D color reconstruction of the airway spaces, note how the
mucous retention cyst has elevated the tissue of the left maxillary antrum
(arrow).
Fig 11-2h A different set of colors in a 3D color reconstruction of the
airway spaces shows the elevation of the tissue as transparent gray (arrow).
Fig 11-2i A coronal view of the same 3D color reconstruction of the airway
spaces and mucous retention cyst. The lesion border (an air–soft tissue
interface) is seen distinctly as a darker gray line. The superior portion of the
oropharyngeal airway is also well depicted (arrows).
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Fig 11-3 Pansinusitis
Fig 11-3a A 9-year-old white girl was referred to an imaging service for
evaluation of her permanent successor teeth. In this patient, almost all of the
paranasal sinuses are opacified and filled with inflammatory product. An
axial slice at the midregion of the condyle shows complete bilateral
opacification of the maxillary antra. Note the early development of the
permanent second molar follicles.
Fig 11-3b An axial slice above the condylar region shows complete
opacification of the left maxillary antrum and mucous or air bubbles in a
portion of the right maxillary antrum (arrow).
Fig 11-3c A slice at the midorbit level shows complete opacification of the
ethmoid cell complex. The eyeballs and the optic nerves are visible through
careful analysis.
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Fig 11-3e Opacification of the right frontal sinus and most of the left is seen
in the inferior region of the orbit.
Fig 11-3f A sagittal view of the opacification of the left maxillary sinus
confirms the presence of air bubbles.
Fig 11-3g Another sagittal slice confirms the involvement of the ethmoid
cells and an extension of the inflammatory change into the frontal sinus. The
patient’s adenoid tissues are also enlarged (arrow).
Fig 11-3h A coronal section of the maxillary antra, ethmoid cells, inferior
nasal concha, osteomeatal complex, and frontal sinuses.
Fig 11-3i Similar regions are involved in this more posterior slice. Only the
frontal sinuses are not seen here (compare to Fig 11-3h).
Fig 11-3j Although the maxillary sinus involvement is apparent on this
typical panoramic view, the other airspace involvement would be grossly
underestimated if this view alone were used for sinus evaluation.
Fig 11-3k This thin slice pseudopanoramic reconstruction is only slightly
better at demonstrating the involvement of the paranasal sinuses.
Fig 11-4 Oroantral Fistula
Fig 11-4a A 65-year-old edentulous woman was evaluated for implant
placement. She had a history of frequent sinus infections. A 3D color
reconstruction shows the edentulous maxilla and mandible as well as the
dens on axis (lower arrow) and vertebral bodies on atlas (upper arrows).
Fig 11-4b This thin coronal slice shows an interruption (arrow) in the floor
of the right maxillary sinus.
Fig 11-4c 3D color reconstructions show a fistula extending down through
the maxilla and opening into the oral cavity at the interruption in the antral
floor.
Fig 11-4d Another 3D color reconstruction of the fistula (arrow). This
oroantral fistula is a likely cause for the chronic sinusitis.
Fig 11-5 Lesion in the Ethmoid Sinus
Fig 11-5a A 27-year-old man was referred to an imaging service for an
orthodontic evaluation to assess the maxillary left canine after orthodontic
traction. In a panoramic reconstruction of the patient data volume, there is
no indication of a problem in any of the visible paranasal or nasal spaces.
Fig 11-5b A solid radiopacity is seen in the left ethmoid cell (blue arrow)
with inflammatory change (opacification) visible in an adjacent air cell
(orange arrow).
Fig 11-5c The same radiopacity seen in the left ethmoid cell (blue arrow) in
a 3D color slab rendering.
Fig 11-5d The lesion in the ethmoid region is an incidental finding. The
solid radiopacity seen in Fig 11-5b has inflammatory change surrounding
the lesion. The optic nerve and medial and lateral rectus muscles can also be
seen faintly.
Fig 11-5e A different color rendering also shows this solid radiopacity in
the left ethmoid cell (blue arrow).
Fig 11-5f The ethmoid lesion (arrows) is highlighted in a sagittal view.
Fig 11-5g In this sagitta l view of the ethmoid lesion (arrow), the airway is
colorized and an outline of the transparent soft tissue is provided.
Fig 11-5h A thin coronal slice (0.15 mm) at the midregion of the sinus
shows ethmoid cell opacity.
Fig 11-5i A thicker coronal slice (4.1 mm) at the same region also shows the
ethmoid cell opacity.
Fig 11-5j A colorized slab rendering of the ethmoid lesion (arrow) allows
comparison of the left-side ethmoid lesion to the normal right-side ethmoid
cells.
Fig 11-5k Unlike the more traditional panoramic image seen in Fig 11-5a,
this 3D color panoramic reconstruction does show the ethmoid lesion.
Osteoma of the ethmoid bone has been reported only rarely.
1
Fig 11-6 Extrinsic Tumor in the Maxillary Antrum
Fig 11-6a An 18-year-old Iranian man was referred to the orthodontic
department at the University of California, San Francisco, for evaluation of
a potential sinus problem. An extrinsic odontogenic tumor had invaded the
left maxillary antrum secondarily.
Fig 11-6b This thin-slice pseudopanoramic reconstruction provides a clearer
picture of the left maxillary antrum and nasal cavity than does Fig 11-6a. On
the left side, note the lack of sinus air space, the hypoplastic condyle, and
the altered malar region.
Fig 11-6c An axial slice shows the complete absence of the left sinus and
replacement by a somewhat multilocular lesion.
Fig 11-6d The axial slice at a slightly more superior level confirms that the
lesion has replaced the maxillary antrum and extended into the malar region.
Fig 11-6e Another axial slice shows complete replacement of the left
maxillary sinus, a multilocular appearance, and the suggestion of
inflammatory product within the multilocular lesion itself.
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Fig 11-6g This slice reveals ethmoid cell involvement and possible
displacement of the nasal septum to the right side.
Fig 11-6h The lesion extends posteriorly into the ethmoid cells and has
caused a loss of their normal architecture. The appearance is that of a
multilocular lesion within the air cells.
Fig 11-6i A slice demonstrating extension of the lesion into more air cells.
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Fig 11-6k A more superior slice shows probable extension of the
odontogenic lesion into the left frontal sinus.
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Fig 11-6m The multilocular appearance in this sagittal slice suggests loculi
of variable size, which is most consistent with an ameloblastoma.
Fig 11-6n A 3D color rendering of the image seen in Fig 11-6m.
Fig 11-6o This coronal slice confirms the lesion’s extension through the
ethmoid cell region into the left frontal sinus.
Fig 11-6p The frontal sinus opacification may just be secondary
inflammatory change because of the blocked osteomeatal complex. Note the
slight inflammatory change in the inferior region of the right maxillary
antrum. Note also the enlarged right inferior meatus and deviation of the
nasal septum.
Fig 11-6q The Dental tool, usually used to draw a preliminary curve for
implant-related tasks, was employed here to select a thin layer through the
maxilla. This provides another look at the lesion characteristics visible in the
left side of the maxilla.
Fig 11-6r A more refined curve through the middle nasal region shows the
lesion extension into the ethmoid cells.
Fig 11-6s A 3D color reconstruction compares the normal right maxillary
sinus region with the abnormal left antrum. The blue arrows are an attempt
to outline the margins of the lesion.
Fig 11-6t Another color combination created with the color presets confirms
the area of the lesion from maxilla to frontal sinus.
Fig 11-7 Fibrosseous Lesion in the Frontal Sinus
Fig 11-7a A 32-year-old man was evaluated for frontal sinus headaches of
an unknown origin. A thin coronal slice near the anterior portion of the right
frontal sinus shows a large, well-defined, mixed radiolucent/radiopaque
lesion (arrow).
Fig 11-7b The lesion (arrow) is shown slightly more posterior than in Fig
11-7a, at the level of the maxillary canines.
Fig 11-7c The sagittal view shows the lesion (arrow) near the lateral aspect
of the frontal sinus.
Fig 11-7d A second sagittal view of the lesion (arrow) near the midline.
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Fig 11-7f This axial view of the lesion (arrow) is slightly inferior to Fig 11-
7e.
Fig 11-7g A 3D color reconstruction slab rendering shows a dense
inhomogeneous mass (arrow).
Fig 11-7h This 3D color reconstructed slab rendering includes the soft
tissue and details the difference between the nonaerated space on the left
(arrow) and the normal aerated space on the right.
Fig 11-8 Antrolith in the Maxillary Antrum
Fig 11-8a Evaluation of an axial image of 58-year-old white male resulted
in the incidental finding of an antrolith (arrow) in the maxillary sinus.
Fig 11-8b The coronal image shows the cortical osteoma (arrow) attached
by a pedicle. Osteomas are less common in the maxillary sinus than in the
fronto-ethmoidal regions and will have either a broad base or a pedicle that
joins them to a cortical wall.
Fig 11-8c A 3D color reconstruction (10 mm) shows both the osteoma and
the antral lining surrounding it (arrow).
Fig 11-8d A 3D reconstruction using the Cube tool in OnDemand 3D
(CyberMed international) shows the dense lesion and the antral mucosal
lining surrounding the bony portion.
References
1. Lachanas VA, Koutsopoulos AV, Hajiioannou JK, Bizaki AJ, Helidonis
ES, Bizakis JG. Osteoid osteoma of the ethmoid bone associated with
dacryocystitis. Head Face Med 2006;2:23.
Temporomandibular Joint Evaluation
One of the most fascinating applications of cone beam computed tomography
(CBCT) for radiologists is the characterization of condylar changes and
appearance of the temporomandibular joint (TMJ) complex. In conventional
2D and tomographic imaging, dentists previously made assertions that a
feature like the so-called bird-beak appearance was indicative of
osteoarthritis or a loose body in the joint space (also known as a joint mouse).
We used panoramic images as gross screening images, knowing that the
image was not truly a lateral projection and therefore almost always
underestimated the true changes. Several techniques were invented in an
attempt to capture the condyle in its true position, or to slice up the condyle
from medial to lateral pole to try to see the changes on various regions of the
condylar head. As if it were not difficult enough to image the TMJ complex
with conventional 2D grayscale techniques, the variations in the condyle’s
shape and size from one side to the other made the task of interpreting
signicant changes even more challenging.
This kind of guesswork in radiographic interpretation will become a thing
of the past with the use of CBCT. True condylar shapes in 3D and color can
replace the 2D grayscale “Rorscharch tests” we used for TMJ assessment.
For all clinicians, this represents a huge leap in our understanding of the
condyles, the TMJ complex, and the appearance of these structures in
response to arthritic insults and systemic alterations.
Fig 12-1 Altered Condylar Morphology
Fig 12-1a A 51-year-old white woman was referred to the Northwest
Radiography imaging center in Bellevue, Washington, for evaluation of the
TMJs after experiencing mild joint pain. A panoramic reconstruction shows
a shortened left condylar neck and altered condylar morphology relative to
the right condyle.
Fig 12-1b A 3D color reconstruction of the panoramic radiograph in Fig 12-
1a shows more detail of the clinical situation.
Fig 12-1c The right condyle is reconstructed by using the Cube tool. Note
the inflammatory changes in the antra.
Fig 12-1d The left condyle is reconstructed by using the Cube tool.
Compare this condyle to the rightside image in Fig 12-1c.
Fig 12-1e A 3D color reconstruction of the right condyle.
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Fig 12-1g A thin coronal slice (0.15 mm) through the midregion of the
condyles demonstrates asymmetry.
Fig 12-1h Same view as Fig 12-1g, presented in a 20.0 mm slice.
Fig 12-1i A 3D color reconstruction at a thickness of 40 mm shows the
altered left condyle.
Fig 12-2 Facial Asymmetry
Fig 12-2a A 33-year-old white woman was referred to a Seattle,
Washington, imaging center for evaluation of a facial asymmetry. A
panoramic reconstruction shows left-side hypoplasia. The teeth are in
occlusion. Note the presence of mandibular tori.
Fig 12-2b A thin panoramic image (2.0 mm) shows hypoplasia of the left
condylar neck and head.
Fig 12-2c A 3D color panoramic reconstruction shows hypoplasia of the left
condylar neck and head, and the teeth are in occlusion. The midlines are
aligned.
Fig 12-2d A maximum intensity projection image with measurements
reveals that the entire ramus is hypoplastic. This finding, coupled with the
hypoplastic neck and condylar head, confirms hypoplasia of the entire left
ramus.
Fig 12-2e The right condylar head in a 3D color reconstruction.
Fig 12-2f 3D color reconstruction of the left condylar head.
Fig 12-2g A coronal slice demonstrates the hypoplastic left condyle in
comparison with the right condyle (arrows).
Fig 12-2h A 3D color reconstruction of the skull shows the shortened left
side. Note the difference between the left and right mandibular angles.
Fig 12-2i Right-side view of the 3D color reconstruction.
Fig 12-2j Left-side view of the 3D color reconstruction displaying smaller
structures than those in Fig 12-2i.
Fig 12-3 Bilateral Condylar Remodeling
Fig 12-3a A 31-year-old white woman was referred to the Northwest
Radiography imaging center in Bellevue, Washington, for evaluation of the
TMJs. The symmetric changes suggest an autoimmune problem such as
rheumatoid arthritis. This thin coronal slice shows bilateral remodeling and
flattening of the condylar heads.
Fig 12-3b This 3D color reconstruction confirms the bilateral remodeling
and flattening of the condylar heads seen in Fig 12-3a.
Fig 12-3c A 3D color reconstruction viewed from the foot end reveals a
rather symmetric relationship of the condyles and fossae.
Fig 12-3d The Cube tool is used to show the right condyle in an
anteroposterior orientation.
Fig 12-3e The Cube tool is used to show the left condyle in an
anteroposterior orientation.
Fig 12-3f The Cube tool is used to show the right condyle in a lateral
orientation.
Fig 12-3g The Cube tool is used to show the left condyle in a lateral
orientation.
Fig 12-3h 3D color reconstruction of the patient’s right side.
Fig 12-3i 3D color reconstruction of the patient’s left side.
Fig 12-3j A 3D color reconstruction of the patient from an anterior view
shows the obvious mandibular symmetry despite the gross condylar
changes.
Fig 12-4 Osteoarthritis of the TMJ Structures
Fig 12-4a This case represents a 34-year-old white woman with mild,
intermittent, unilateral joint pain. In the past, the term bird beak was
frequently applied to changes associated with osteoarthritis (OA) of the
TMJ, probably because of the myriad lateral projection techniques applied
to see the condylar change. Now that it is possible to visualize the condylar
structures in 3D color reconstructions, some of the terminology should be
reconsidered. A thin axial slice (0.15 mm) of the midregion of the condyles
reveals some condylar sclerosis on the lateral pole of the right condyle
(arrow).
Fig 12-4b In this thin-slice pseudopanoramic reconstruction, the left
condyle shows what appears to be an osteophytic projection, or what some
have called a classic bird-beak appearance.
Fig 12-4c In a thicker slice of the panoramic reconstruction, the left condyle
still demonstrates the bird-beak appearance.
Fig 12-4d Even this thin slice sagittal view suggests the same appearance as
in Fig 12-4c.
Fig 12-4e The condyle on the patient’s right side appears to be normal in
this saggital view.
Fig 12-4f The right condyle is not normal, but instead shows a flattened,
thickened, remodeled region (arrow) on the lateral pole as suggested in the
axial image, Fig 12-4a.
Fig 12-4g The right condyle seen from the lateral view confirms a flattened,
thickened, remodeled area (arrow); one might imagine that in a 2D lateral
grayscale image, this region would look like a beak.
Fig 12-4h The view of the left condyle in 3D color with the use of the Cube
tool reveals some significant lipping of the bone along the anterior margin
(arrow). Compare this image to Fig 12-4i to see how the bird-beak
appearance could also have been misinterpreted by simple angulation
changes.
Fig 12-4i Is it a bird beak appearance or not? You decide after comparison
with Fig 12-4h.
Fig 12-4j This coronal slice shows a subchondral cyst on the superior aspect
of the left condyle (arrow).
Fig 12-4k A 3D color reconstruction illustrates the lipping phenomenon
(arrow), but does not show the cyst seen in Fig 12-4j. As detailed as CBCT
views can be, multiple images from the data volume are usually required to
visualize all of the changes and problems.
Fig 12-5 Loose Body in the Joint Space
Fig 12-5a A 62-year-old white woman was referred to a Seattle,
Washington, imaging center for TMJ evaluation because of joint noises. A
panoramic reconstruction from the data volume shows little indication of a
loose body in the joint space (also known as a joint mouse), although the left
condylar head is altered in appearance.
Fig 12-5b A thin-slice pseudopanoramic reconstruction shows a very slight
radiopacity anterior to the left condylar head.
Fig 12-5c A sagittal slice at a thickness of approximately 20 mm simulates
the typical plain image view one might see in tomography. The loose body
is clearly depicted.
Fig 12-5d A thin sagittal slice (0.15 mm) demonstrates the loose body more
precisely.
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Fig 12-5f A 3D color reconstruction visualizes the problem.
Fig 12-5g A coronal view is used to compare the left and right sides. The
left condyle is hypoplastic and shows an altered morphology. The right
condyle has some less dramatic changes.
Fig 12-5h The 3D color reconstruction compares left and right sides. The
left condyle is hypoplastic; lipping is evident. The loose body is not very
apparent.
Fig 12-5i A 3D color view created with the Cube tool shows the loose body
in the left condyle (arrow).
Fig 12-5j A 3-D color view created with the Cube tool shows the left
condyle in an anterior projection, revealing the loose body adjacent to the
lateral pole.
Fig 12-5k The left condyle is shown in 3D color Endoscope mode in
OnDemand 3D software (CyberMed International). Note how this tool
increases the image resolution significantly.
Fig 12-5l Enlargment of the Endoscope view.
Fig 12-5m An Endoscope view from the anterior perspective shows the
condyle at a distance.
Fig 12-5n A thin sagittal slice shows the vertebral bodies. Osteophytic
activity is seen on the superior portion of C2 (arrow). Changes in the
vertebral bodies are often seen concomitantly with condylar changes from
OA.
Fig 12-5o A 3D color panoramic reconstruction demonstrates the condylar
changes, including the hypoplastic left condylar neck and head.
Fig 12-6 Condylar Tumor
Fig 12-6a A 62-year-old white woman was referred to Advanced Dental
Imaging in Salem, New Hampshire, for evaluation of a proposed implant
site for a missing maxillary right lateral incisor, as well as for evaluation of
the TMJs. A panoramic reconstruction demonstrates an enlargement of the
right condylar neck and head relative to the left side. The right stylohyoid
process also appears elongated compared with the left.
Fig 12-6b A thin slice (0.15 mm) pseudopanoramic reconstruction confirms
the altered right condylar morphology and enlarged size.
Fig 12-6c A thin axial slice (0.15 mm) allows the clinician to compare the
right and left condylar heads.
Fig 12-6d A thin coronal slice (0.15 mm) allows the clinician to compare
the right and left condylar heads. Note the appearance of two loculi on the
right condyle.
Fig 12-6e A thin sagittal slice (0.15 mm) shows the normal left condyle.
Fig 12-6f A thin sagittal slice (0.15 mm) of the hyperplastic right condyle
includes the neck.
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Fig 12-6h An image rendered with the Cube tool shows the enlarged
condyle. The tumor is apparently originating from the pterygoid fovea
region.
Fig 12-6i An image rendered with the Cube tool shows the normal left
condyle for comparison.
Fig 12-6j A 3D color reconstruction shows the TMJ structures in a bilateral
comparison. The differential diagnosis for this lesion included central giant
cell granuloma, hyperplasia of the right condyle, osteochondroma, and
traumatic bone cyst.
Systemic Findings
Although patients who visit our dental practices can have many different
systemic conditions (eg, cardiopulmonary problems, endocrine disorders, and
so on), few of them will show overt radiographic signs of their disorders in
the head and neck region when imaged. Recent clinical studies have identied
the presence of sclerotic plaques in the carotid region as a potential harbinger
of hypertension and possibly stroke,
1–3 and there are always patients who are
referred to imaging centers if various head or neck cancers are suspected.
Regardless, signicant systemic findings are rare in the typical population of
patients that we treat and refer for cone beam computed tomography (CBCT).
This is the good news.
The bad news, however, is that although the incidence of occult
pathology may be small, the outcome could be signicant for the patient with a
positive finding. I must reiterate here the absolute requirement for the entire
data volume to be examined by a competent radiologist, with either a medical
or oral and maxillofacial background, if we are to properly use CBCT for
our patients’ needs. A myopic clinician may become involved in a serious
lawsuit if no attempt is made to examine the data volume beyond an implant
site assessment or evaluation for a clicking joint. These CBCT data volumes
are not the single radiographs used in the past for most clinical decisions. The
scans produce powerful, reconstructable data sets that require the clinician to
have signicant anatomical and pathologic understanding as well as the skills
for thorough patient examination and precise radiographic interpretation.
The following cases demonstrate some of the serious systemic findings
reported in more than 1,800 patients. There is no doubt that, as more cases
are examined worldwide and the ndings reported, many more significant
systemic findings will be uncovered in these CBCT data volumes.
One systemic condition or disorder that appears to have identifiable
radiographic findings in the CBCT data volumes in its later stages is type 2
diabetes mellitus. In the first 1,000 data volumes that I examined, I believe
that I saw medial arterial calcification (MAC), formerly called Mönckeberg
sclerosis, in at least 13 cases. Although that translates into an incidence of
only 1.3%, this finding is significant. Type 2 diabetes mellitus affects over
300 million people worldwide.
4 The National Diabetes Education Program
(NDEP), a branch of the US Department of Health and Human Services, only
recently produced an informational brochure for dental clinicians to discuss
with and give to patients. The NDEP states that “nearly 21 million Americans
have diabetes, and some 7 million don’t know they have it.”
5
MAC is a unique problem for diabetic patients. Vessels with
calcifications in their medial layers cannot respond appropriately to the
vascular demands placed on them. This is a form of peripheral arterial disease
(PAD), which is significant because it could lead to below-the-knee
amputations in diabetic patients with end-stage renal disease (ESRD). The
NDEP reports that diabetes is responsible for “fully 67% of lower-extremity
amputations.”
5
In my experience, MAC can be seen on panoramic and even
intraoral films.
6,7 We have known about the problem for years, but now we
have an incredible opportunity to visualize the changes in carotid arteries
through CBCT. The following cases illustrate this convincingly. It is likely
that some of the cases described in the literature as having “diffuse
calcifications,” suggesting a patient is at increased risk for stroke, may have
grossly underestimated cases of type 2 diabetes mellitus; the panoramic
image is a vastly inferior image modality for this type of evaluation. It also
underscores the necessity for the radiologist or clinician to have all of the
clinical information while examining CBCT data volumes, so the findings
can be placed in their proper context.
Type 2 diabetes mellitus is more common in African American, Hispanic,
American Indian, Asian American, and Pacific Islander populations than in
other populations. It is also more common in older members of the
population.
5
A quote from researchers at the Cleveland Clinic Center for Continuing
Education expertly sums up the relationship between type 2 diabetes mellitus
and kidney function. These researchers state
8
:
Diabetes has become the number one cause of ESRD in the United
States, and the incidence of type 2 diabetes mellitus continues to grow
both in the United States and worldwide. Approximately 45% of new
patients entering dialysis in the United States are diabetics. Early
diagnosis of diabetes and early intervention are critical in preventing the
normal progression to renal failure seen in many type 1 and a significant
percentage of type 2 diabetics.
Diabetes is the number one cause of adult blindness and the number one
cause of kidney failure. Two of every three people with diabetes die of heart
disease or stroke.
5 Once thought of as an incidental finding, MAC is now
considered to be a significant sign of PAD, which requires aggressive
treatment in the diabetic patient.
9
Fig 13-1 Medial Arterial Calcification: Case 1
Fig 13-1a A 71-year-old white woman was referred to a Seattle,
Washington, imaging service for follow-up evaluation of her mandibular
surgery. A maximum intensity projection (MIP) panoramic image reveals a
calcification in the right oropharyngeal area (arrow).This projection appears
very similar to calcifications seen in reports by Friedlander and Baker
1,2 and
Carter et al.
3
Fig 13-1b An MIP panoramic image shows bilateral calcifications (arrows),
which are very uncommon if the case represents a sclerotic plaque. This
presentation would be more consistent with a systemic condition that affects
more of the vascular system, such as type 2 diabetes mellitus.
Fig 13-1c The axial view of this patient shows that the calcifications are
starting to surround the carotid arteries (arrows).
Fig 13-1d The coronal view of this patient shows the right-side calcification
(arrow).
Fig 13-1e In the coronal section of the right-side calcification, the Cube tool
reveals a more circumferential calcification pattern, like that seen in MAC.
Fig 13-1f The image in Fig 13-1e is enlarged to reveal this circumferential
calcification pattern (arrow).
Fig 13-1g In the axial section of the left side, the Cube tool reveals the
circumferential calcification pattern described previously.
Fig 13-1h The Cube tool is used on the left side of the coronal section to
help confirm the calcification (arrow).
Fig 13-1i A 3D color close-up of the left side confirms the calcification
(blue arrow). Note the patient’s airway (small orange arrow) and skin
(large orange arrow).
Fig 13-1j A 3D color reconstruction shows both the result of orthognathic
surgery and the bilateral MAC calcifications (arrows).
Fig 13-2 Medial Arterial Calcification: Case 2
Fig 13-2a A 72-year-old white woman was referred to an orthodontist for
temporomandibular joint (TMJ) evaluation related to moderate, intermittent
joint pain. Type 2 diabetes mellitus is possibly the underlying systemic
problem. A circumferential calcification (arrow) of the right carotid artery
region is seen in this thin axial slice (0.15 mm).
Fig 13-2b Bilateral calcifications (arrows) in the carotid artery regions are
present at the level of C3 to C4.
Fig 13-2c Bilateral circumferential calcifications (arrows) are confirmed in
the 3D color reconstruction.
Fig 13-2d A Cube tool reconstruction of the left-side calcification (arrow)
confirms the circumferential pattern.
Fig 13-2e Even this thin coronal slice (0.15 mm) suggests an MAC pattern
(arrow).
Fig 13-2f A 3D color reconstruction shows bilateral calcifications (arrows).
Note the airway and condyle anatomy in this image. This was rendered at a
thickness of about 40 mm.
Fig 13-2g The MIP image also suggests the bilateral circumferential pattern
of MAC (arrows).
Fig 13-3 Medial Arterial Calcification: Case 3
Fig 13-3a An 83-year-old white man was referred to the Northwest
Radiography imaging center in Bellevue, Washington, for CBCT evaluation
of implant sites. A panoramic reconstruction at a thickness of about 13 mm
fails to show the oropharyngeal calcifications.
Fig 13-3b A 3D color panoramic reconstruction at a thickness of about 30
mm clearly demonstrates the oropharyngeal calcifications consistent with
MAC (arrows).
Fig 13-3c Bilateral circumferential calcifications (arrows) show up in this
axial slice.
Fig 13-3d Bilateral circumferential calcifications (arrows) are visible in an
axial slice slightly superior to the level in Fig 13-3c.
Fig 13-3e Right-side calcifications in this 3D color reconstruction extend
along a significant portion of the artery.
Fig 13-3f Left-side calcifications in a 3D color reconstruction also extend
along a significant portion of the artery.
Fig 13-3g Use of the Endoscope tool in the software enhances the arterial
detail.
Fig 13-3h An enlarged view provided by the Endoscope tool depicts the
exact relationship of the arterial problem to the mandible and airway.
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Fig 13-3j A coronal section slightly more posterior to that in Fig 13-3i
shows excellent definition of the calcified arterial rings (arrows).
Fig 13-3k Multiplanar views of the right side with an automatic 3D color
reconstruction (bottom right).
Fig 13-3l Multiplanar views of the left side with an automatic 3D color
reconstruction (bottom right).
Fig 13-4 Bisphosphonate-Induced Osteonecrosis of the Jaw
Fig 13-4a A 55-year-old white woman was referred to Advanced Dental
Imaging in Salem, New Hampshire, for a cone beam scan to evaluate a
previous extraction site on the left side of the posterior mandible. The
imaging illustrates the diagnosis of osteonecrosis of the jaw secondary to
bisphosphonate medication. A thin axial slice shows an ill-defined
radiolucency in the left side of the posterior mandible. There are multiple
perforative defects.
Fig 13-4b The Cube tool is used to create a 3D color reconstruction.
Fig 13-4c An enlarged view of the reconstruction in Fig 13-4b.
Fig 13-4d A panoramic reconstruction at a thickness of about 25 mm.
Fig 13-4e A pseudopanoramic reconstruction at a thickness of about 9.1
mm.
Fig 13-4f The same reconstruction as in Fig 13-4e is created with a slice
slightly anterior to the previous position.
Fig 13-4g A 3D color panoramic image shows scatter artifacts from the
existing metallic restorations.
Fig 13-4h A panoramic MIP image. This image is not good for a detailed
view of the lesion, but it gives an overall impression of the dental treatment
without the scatter artifacts seen above.
Fig 13-4i The Dental tool, used mainly for implant site assessment, is
employed here to obtain crosssectional slices (top right) from the anterior to
the posterior of the lesion and to delineate the location of the inferior
alveolar nerve (red dot) relative to the lesion.
Fig 13-4j This cross-sectional slice is posterior to that in Fig 13-4i.
Fig 13-4k This cross-sectional slice is posterior to that in Fig 13-4j.
Fig 13-4l This cross-sectional slice is posterior to that in Fig 13-4k.
Fig 13-5 Squamous Cell Carcinoma
Fig 13-5a A 51-year-old white man was seen at an imaging center in South
Dakota for evaluation of radiolucencies associated with partially impacted
mandibular third molars. The mandibular left third molar was symptomatic.
Whole-body positron emission tomography and computerized tomography
scans identified bilateral focal hypermetabolic areas in the third molar
regions. The radiologist report also noted an asymmetric increase in 2-
fluoro-2-deoxy-D-glucose (FDG) uptake in the left posterior mandible that
was deemed “suspicious” for focal squamous cell carcinoma. The cone
beam images confirm the presence of a malignancy. A panoramic image
reconstructed at a thickness of about 30 mm shows bilateral pericoronal
radiolucencies. Both lesions exhibit regular cortical outlines, and neither
lesion looks particularly ominous.
Fig 13-5b Scrolling through this panoramic image reveals that the lesion on
the patient’s left side appears much larger and seems to encroach on the
inferior alveolar nerve canal.
Fig 13-5c A thin-slice panoramic image (0.15 mm) shows some irregularity
at the margins of the left-side lesion, as well as small permeative defects.
These are more ominous radiographic features.
Fig 13-5d A sagittal view shows the proximity of the left-side lesion to the
nerve canal.
Fig 13-5e By using the Dental tool, which is most often reserved for implant
assessment, it is possible to colorize the inferior alveolar nerve canal
(green), show the proximity of the lesion to the canal, and assist the
surgeon’s approach.
Fig 13-5e A thin axial slice (0.15 mm) shows the lesion perforating the
buccal cortical bone.
Fig 13-5g A thin axial slice (0.15 mm) shows the lesion perforating the
buccal cortical bone, but more importantly, it shows the permeative
appearance of this lesion. The inferior alveolar nerve canal is shown by the
arrow.
Fig 13-5h A thin coronal slice (0.15 mm) shows the permeative appearance
on the buccal aspect of this lesion. The inferior alveolar nerve canal is
shown by the arrow.
Fig 13-5i A more posterior coronal slice reveals destroyed cortical bone.
Note the intact marginal area on the mandibular right third molar.
Fig 13-5j This is the site of the greatest cortical destruction.
Fig 13-5k The Dental tool shows axial, cross-sectional, and panoramic
images relating the lesion appearance.
Fig 13-5l The Dental tool shows axial, cross-sectional, and panoramic
images at the most posterior aspect of the lesion. The nerve canal (arrow)
appears to be separate from the lesion at this point.
Fig 13-5m A 3D color reconstruction shows the perforation caused by the
lesion.
Fig 13-5n A close-up 3D color reconstruction provides a detailed look at the
perforation.
Fig 13-5o The lesion is shown from the lingual aspect in this 3D color
reconstruction.
References
1. Friedlander AH, Baker JD. Panoramic radiography: An aid in detecting
patients at risk of cerebrovascular accident. J Am Dent Assoc
1994;125:1598–1603.
2. Friedlander AH. Identification of stroke-prone patients by panoramic and
cervical spine radiography. Dentomaxillofac Radiol 1995;24:160–164.
3. Carter LC, Tsimidis K, Fabiano J. Carotid calcifications on panoramic
radiography identify an asymptomatic male patient at risk for stroke. A
case report. Oral Surg Oral Med Oral Pathol Oral Radiol Endod
1998;85:119–122.
4. The World Health Organization. Diabetes Fact Sheet Nº 312.
http://www.who.int/mediacentre/factsheets/fs312/en/index.htm. Accessed
7 September 2012.
5. National Diabetes Education Program. Working together to manage
diabetes: A guide for pharmacy, podiatry, optometry, and dental
professionals, 2007. Available at: http://www.
ndep.nih.gov/diabetes/WTMD/index.htm. Accessed 13 September 2012.
6. Miles DA, Craig RM, Langlais RP, Wadsworth WC. Facial artery
calcification: A case report of its clinical significance. J Can Dent Assoc
1983;49:200–202.
7. Miles DA, Craig RM. The calcified facial artery: A report of the panoramic
radiograph incidence and appearance. Oral Surg Oral Med Oral Pathol
1983;55:214–219.
8. Augustine J, Vidt DG. Cleveland Clinic Disease Management Project:
Diabetic nephropathy. Available at: http://
www.clevelandclinicmeded.com/medicalpubs/
diseasemanagement/nephrology/diabeticnephropathy/
diabeticnephropathy.htm#prevalence. Accessed 8 August 2008.
9. Hayden MR, Tyagi SC, Kolb L, Sowers JR, Khanna R. Vascular
ossification–calcification in metabolic syndrome, type 2 diabetes mellitus,
chronic kidney disease, and calciphylaxis– calcific uremic arteriolopathy:
The emerging role of sodium thiosulfate. Cardiovasc Diabetol 2005;4(1):4.
Vertebral Body Evaluation
A joint is a joint is a joint … or so I used to teach my graduate students.
Although the temporomandibular joint (TMJ) is specialized in its motion
capability, and the mandible is the only bone in the body with an articulation
on each side, the TMJs are considered “loaded” just like the knees and hips
and can demonstrate comparable osteoarthritic changes. On plain radiographs
or even digital images, many condyles that are “ugly,” misshapen, modied by
osteophytic activity, or even grossly altered in their morphology still might
be totally asymptomatic. On the other hand, using these same image receptors
(eg, panoramic, tomographic), TMJs may appear normal and yet be quite
painful. The pain, especially in conditions like osteoarthritis (OA), might
precede the actual radiographic change by many months. Now, with cone
beam computed tomography (CBCT), we may have an opportunity to detect
the osteoarthritic changes earlier. There can be a correlation to other loaded
joints like the knee and/or intervertebral joints as well. When I see vertebral
bodies with subchondral cyst formation and subchondral sclerosis in cone
beam images, I also often see concomitant changes on the condylar head. In
Table 1-1, 32 of the 381 total patients were found to have osteoarthritic
changes in the vertebrae. That represents approximately 8.4% of that initial
patient population.
Fig 14-1 Osteoarthritic Findings: Case 1
Fig 14-1a This patient showed significant changes in the cervical vertebrae
without major alteration of the TMJ condyles. Unlike rheumatoid arthritis,
which is polyarticular and symmetrical and can affect the condyles, OA
usually affects one or two major loaded joints in the body asymmetrically. A
panoramic reconstruction shows ostensibly normal condyles.
Fig 14-1b A sagittal view shows osteophytic activity on many surfaces, loss
of intervertebral joint space, and subluxation of the vertebrae C3 to C5
(arrows).
Fig 14-1c This sagittal view reveals significant subchondral sclerosis and
subchondral cyst formation on C3 to C5.
Fig 14-1c A coronal view shows the subchondral cysts on C5 (arrows).
Fig 14-1e The right condylar head appears normal in this thin sagittal slice
(0.15 mm).
Fig 14-1f The left condylar head may have a slight cortical thickening
(arrow), which is indicative of early subchondral sclerosis.
Fig 14-1g A 3D color panoramic reconstruction demonstrates that the
condyles, although altered slightly in shape, appear normal.
Fig 14-2 Osteoarthritic Findings: Case 2
Fig 14-2a A 56-year-old white woman showed osteoarthritic changes in the
vertebral bodies, along with slight concomitant condylar head involvement.
There are significant osteophytic changes on C3, C4, and C5, with collapse
of the intervertebral joint spaces and subluxation (bottom three arrows). C2
also shows subchondral sclerosis and possible fusion with the anterior arch
of C1 (top arrow).
Fig 14-2b Subchondral cyst formation on C1.
Fig 14-2c Additional subchondral cyst formation (arrow).
Fig 14-2d The left condylar head appears normal.
Fig 14-2e The right condylar head shows some surface thickening in the
form of subchondral sclerosis (arrow). This is an early change but indicative
of synovial fluid loss and subsequent bone formation to protect the condylar
surface.
Fig 14-2f Direct volumetric rendering of the TMJ. The Dual mode allows
both condylar heads to be viewed for comparison.
Fig 14-2g A pseudopanoramic reconstruction shows the condyles. The left
condyle looks marginally thicker than the right.
Fig 14-3 Osteoarthritic Findings: Case 3
Fig 14-3a A 66-year-old Asian man was referred to Northwest Radiology
imaging center in Seattle, Washington, for an implant site assessment.
Osteoarthritic findings are apparent, with severe osteophyte formation,
subluxation, and loss of intervertebral joint space seen on C3, C4, and C5
(arrows). There is also a large erosion on the anterior aspect of C4 (upper
left arrow).
Fig 14-3b Subchondral cyst formation on C4 (orange arrow) as well as C5
(blue arrow).
Fig 14-3c The condylar heads in the axial view, as well as the 3D Cube tool
color reconstruction of the right condyle appear relatively normal. (left)
Some slight cortical thickening may be present on the lateral pole (arrow) in
the axial view. (right) The 3D reconstruction shows it to be condylar lipping
(arrow).
Fig 14-3d The right condyle in 3D color is rotated to show the lateral
aspect. The deep depression (arrow) is an imaging artifact; the patient was
not correctly positioned to capture the entire condylar area.
Fig 14-3e The left condyle is essentially normal except for some mild
flattening (arrows).
Fig 14-3f Lateral aspect of the condyle seen in Fig 14-3e.
Fig 14-3g In this 2D thin slice grayscale image, the anterior portion of the
left condyle (arrow) looks like an osteophytic projection. However, the 3D
color rendering in Fig 14-3f shows that this shape is just the result of some
flattening of the condyle.
Fig 14-3h Lipping of the right condylar head (arrow) is confirmed in this
3D color reconstruction.
Fig 14-3i Even though this 3D color panoramic reconstruction suggests an
osteophytic projection with the traditional bird-beak appearance (arrow), it
has been shown that this is actually flattening and lipping of the condylar
surface. Regardless of appearance, the condition can still be attributed to
OA.
Fig 14-3j Although this grayscale panoramic reconstruction seems to be a
good depiction of the condyles, it grossly underrepresents the scope of
condylar change seen in the previous images of this case.
Selected Cases from Radiology
Practice
Although the featured cases in this chapter present some medical history, I
rarely have such information when I review a cone beam computed
tomography (CBCT) data set. In my practice, I ask clinicians to provide only
patient names and dates of birth. This approach is appropriate for an oral and
maxillofacial radiologist because having the entire dental and medical records
might bias my review of the cone beam volume data and my analysis of
occult pathology. However, if a case is sent to me for a second opinion, there
is often a specic nding that the referring clinician lacks the training to
characterize more specically. In referral cases, I still follow the same
systematic approach that I take to review any data volume. Although I
capture suf cient images to characterize the nding for which the referral was
made, I must study the entire data volume for occult pathology. If I limited
my review of the data, I would miss additional reportable ndings that could
be signicant and require additional follow-up management.
Fig 15-1 Undiagnosed Orofacial Pain
A healthy 15-year-old adolescent girl was referred for CBCT evaluation of a
lesion in the right posterior region. The patient had complained of pain in the
posterior right mandible and the initial dentist had supposed the pain was due
to the developing third molar. The area was imaged in a panoramic
radiograph in preparation for removal of the mandibular right third molar.
The panoramic radiograph revealed a 2 cm x 3 cm radiolucent lesion in the
posterior right mandible. The mandibular right third molar was extracted.
Even without access to the original conventional panoramic radiograph, the
lesion was obvious on the reconstructed panoramic view from the CBCT
volume (Fig 15-1a).
Fig 15-1a Reconstructed panoramic view from CBCT data. The extraction
site for the mandibular right third molar is obvious, as is the lesion in the
area of the mandibular right premolars and first molar.
The review of the data volume began with the axial view in the mandible
(Fig 15-1b). As the data slices moved into the paranasal sinus spaces,
significant mucosal change became apparent in the maxillary sinus, ethmoid
air cell complex, and sphenoid sinuses, and multiple images were captured in
the software for inclusion in the final report (Figs 15-1c to 15-1j). As the
mandibular slices were examined in full, the cystic lesion became apparent
and was captured in grayscale and color images, including 3D color
reconstructions that characterize the lesion for presurgical planning (Figs 15-
1k to 15-1o). Finally, review of the temporomandibular joint (TMJ) complex
revealed osteoarthrosis of the right condyle (Fig 15-1p).
Fig 15-1b This axial view shows the recent extraction site of the mandibular
right third molar (arrow).
Fig 15-1c Thin slice axial view of significant mucosal change in the
ethmoid air cell complex (arrows).
Fig 15-1d Thin slice axial view of additional mucosal change in the inferior
region of the sphenoid sinus (arrows).
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Fig 15-1f Another axial view of mucosal change (arrows) in the maxillary
antra at the level of the developing apices of the maxillary second molars.
Fig 15-1g Sagittal view of the mucosal change in the left maxillary antrum
(arrow).
Fig 15-1h Sagittal view of the mucosal change in the right maxillary
antrum. Note the lesion is also imaged around the mandibular right first
molar.
Fig 15-1i Coronal view of the mucosal changes in the maxillary antra
(lower arrows) and ethmoid air cell complex (upper arrows). Note also the
thinned cortex of the mandibular lesion with slight scalloping.
Fig 15-1j 3D color reconstruction of the lesion with an apparent perforation
of the lingual cortex.
Fig 15-1k Unilocular radiolucent lesion (arrow), which has thinned the
lingual cortex.
Fig 15-1l 3D color reconstruction (20 mm) showing an empty cavity
(arrow).
Discussion of the case
This case illustrates the problem of being confronted with a patient with
undiagnosed orofacial pain. It is interesting that the initial dentist thought that
the developing third molar could be the source of the pain. This is rarely the
case. If the tooth had been further developed and trying to erupt, there would
be the possibility of pericoronitis, but this is not the reality.
The volume data shows that the patient had more than one problem: a
mandibular lesion, pansinusitis, and condylar osteoarthrosis. The chronic
sinusitis could not have given rise to the pain in the right mandible; there is
no referral pattern from the paranasal sinus spaces to the mandibular posterior
region. The lesion surrounding the mandibular right premolars and first molar
was found only incidentally but is a more probable source of the patient’s
pain. However, the finding of osteoarthrosis of the right condyle cannot be
ruled out as a source of the pain because pain from the TMJ complex can
refer to the posterior mandible. To correctly diagnose the orofacial pain, the
clinician must delineate whether or not the reported pain in the right mandible
is related to a bone problem or a soft tissue/muscular problem. In addition,
there is no patient history to rule out a myofascial pain problem. There is
always the possibility that the finding of the lesion in the right mandible is
serendipitous.
Fig 15-1m Pseudopanoramic reconstruction at 1 mm in thickness shows the
region of the extraction site. This was probably not the source of the
patient’s pain. The mandibular lesion is not visible in this thin section.
Fig 15-1n Use of multiplanar and panoramic views clarifies the
radiographic features of the lesion. It is a well-defined, solitary radiolucency
with no internal calcification and a cortical margin situated between the
mandibular right premolars and first molar that envelops the root apices
without resorption or displacement. It also extends to the alveolar crest and
has thinned, but does not appear to have perforated, the lingual cortical
plate.
Nevertheless, there are some changes associated with this lesion that
suggest that the provisional diagnosis of a traumatic bone cyst is just that, a
provisional diagnosis. The lesion does not appear to behave like a traumatic
or simple bone cyst because of the thinning of the cortices and extension to
the alveolar crest.
Fig 15-1o 3D color reconstruction using the Cube tool. Rotating to view the
lesion from the lingual confirms that there is no root resorption of the
mandibular right first molar. Additional transparent lesions confirms no
resorption of any apices in the vicinity.
Fig 15-1p Temporomandibular joint (TMJ) condylar views show the
formation of a subchondral cyst on the right condylar head. Given the
patient’s age, this is most likely osteoarthrosis and not osteoarthritic change.
A differential diagnosis should include lesions of odontogenic origin such
as cysts or tumors. My list of differential diagnoses includes: traumatic bone
cyst, central giant cell granuloma or other vascular/reactive lesion, and
possible odontogenic keratocyst.
Consequently, the following recommendations were made:
1. Aspirational biopsy is indicated prior to any surgical intervention for
this lesion. The presence of a strong colored fluid would most likely
confirm a dramatic bone cyst.
2. The patient should also be referred to the primary care provider and/or
an otolaryngologist for clinical and endoscopic evaluation of the
paranasal sinuses.
Fig 15-2 Stafne Defect
A 41-year-old man was imaged in a local dental office with a CBCT machine
with a large field of view. The referring dentist was concerned about an ovoid
radiolucency seen in the right posterior mandible in the region of extracted
mandibular right third molar (Fig 15-2a). The patient was asymptomatic and
had no significant medical history. Although not exactly typical, the lesion is
not uncommon in the mandible and is often a source of unnecessary concern
for clinicians (Figs 15-2b to 15-2g). In addition, there were several incidental
findings in the data volume (Figs 15-2h to 15-2k).
Fig 15-2a A thin slice pseudopanoramic image shows a small, well-defined
somewhat ovoid radiolucency with a distinct cortical margin. Unlike a
typical lingual developmental submandibular salivary gland depression
(Stafne defect), this lesion is located superior to the inferior alveolar nerve
canal.
Fig 15-2bReconstructed multiplanar (axial and coronal) views (top) and a
thin slice panoramic (bottom) reveal that the lesion has developed from
outside the mandible and remodeled the bone. The typical Stafne defect
develops inferior to the inferior alveolar nerve.
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Fig 15-2d 3D color reconstruction of the Stafne defect using the Virtual
Endoscopy tool with preset colors. Note the improved appearance of the
hyoid bone and the presence of the airway.
Fig 15-2e Colorization of the inferior alveolar nerve within the canal
showing the nerve’s relationship to the lesion.
Fig 15-2f This reconstructed panoramic view simulates what might be seen
on a conventional film-based panoramic radiograph.
Fig 15-2g These images better characterize the developmental lesion. The
image in the middle shows the lesion viewed from the posterior direction.
Fig 15-2h This thin slice coronal section shows another incidental finding, a
small mucus retention cyst in the right maxillary sinus.
Fig 15-2i Further posterior in the coronal plane, the beginning of the
palatine torus is visible as well as a deviated nasal septum (arrow).
Fig 15-2j This thin slice axial view shows the most obvious incidental
finding in the volume, a palatine torus.
Fig 15-2k Presence of the palatine torus was confirmed in a thin slice
sagittal view.
Discussion of the case
Although not a significant lesion to be biopsied, the developmental anomaly
in this case is often identified incorrectly. If a clinician uses only a panoramic
radiograph to assess the lesion, its location superior to the inferior alveolar
canal may suggest that it is something other than the lingual developmental
submandibular salivary gland depression, known as a Stafne defect. Such a
conclusion could lead to a biopsy, which increases patient cost and could
become a source of stress and anxiety for the patient from uncertainty about
the nature of the lesion. The coronal views and 3D color reconstructions
confirm that the reshaping of the mandible occurred from something outside
of the bone and not within it. This eliminates the possibilities of odontogenic
cysts and tumors of significance. Confirmation could be achieved by a plain
film sialography—certainly less invasive than a biopsy— but in this case,
only periodic radiographic follow-up is indicated to observe if there is any
enlargement of the lesion. Because the CBCT allowed for a more accurate
characterization of the developmental anomaly, the patient was spared the
anxiety and cost of an unneccessary surgical biopsy.
Fig 15-3 Nasophyaryngeal Carcinoma
A 71-year-old man underwent presurgical imaging to evaluate the extraction
site of the mandibular left first molar. Implant placement in the extraction site
was scheduled to take place 1 month after the radiographic examination.
According to the medical history, there were no medical contraindications to
the planned procedures.
Review of the data volume started in axial views at the extraction site and
continued superior to it. In the axial and sagittal planes of section, a condyle
cyst was revealed in the left condyle (Figs 15-3a to 15-3d). Moving superior
in the axial plane of section, significant mucosal changes were visible in the
sphenoid sinus and superior ethmoid air cells on the right side (Figs 15-3e to
15-3g).
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Figs 15-3b Sagittal view of the subchondral cyst (arrow) in the left condylar
head.
Figs 15-3c and 15-3d 3D reconstructed views of the left condyle
demonstrating lipping. Both lipping and subchondral cysts appear frequently
in patients with osteoarthritis.
Fig 15-3e Thin slice axial view showing mucosal change in the sphenoid
sinus and superior ethmoid air cell complex on the right (arrow).
Fig 15-3f Additional changes in the ethomoidal air cell complex extending
inferiorly (upper arrow). In addition the lateral wall of the sphenoid sinus is
hyperostotic (lower arrow), suggesting a long-standing problem.
Fig 15-3g Another axial view showing the superior ethmoid air cells (upper
arrow) and the hyperostotic walls of the sphenoid sinus (lower arrow).
Once the same areas were reviewed in sagittal views, it became clear that
the changes in the nasal cavity and airway were more than just inflammation
(Figs 15-3h to 15-3j). The opacification of the paranasal sinus spaces
stemmed from an extrinsic problem. The coronal plane of section allowed for
better tracking of the extent of the lesion (Figs 15-3k to 15-3m). Additional
reportable findings affecting the patient’s treatment were seen in sagittal
views, including a residual periapical lesion (Fig 15-3n) and an osteophyte on
vertebral body C2 (axis) (Fig 15-3o).
Fig 15-3h A thin slice sagittal section showing a large mass in the
nasopharynx extending into the ethmoid air cells and sphenoid sinus. The
lesion also appears to have caused an erosion or perforation into the sella
turcica (arrow).
Fig 15-3i A thickened sagittal section showing the invasion of the tumor
(arrows) from the nasal cavity into the sphenoid sinus.
Fig 15-3j A sagittal view at the midline in the posterior nasopharynx
showing the location of the tumor (arrow) outside of the paranasal sinus
spaces.
Fig 15-3k A coronal view through the midportion of the paranasal sinuses
and nasal structure. Note the obliteration of the inferior and common meatal
spaces (lower arrow), as well as the extension from the inferior nasal cavity
to the ethmoid air cell complex (upper arrow).
Fig 15-3l A coronal view through the posterior portion of the nasal cavity
suggests an extension of the tumor into the posterior nasopharyngeal space
and confirms the presence of hyperostotic walls on the lateral aspect
(arrows).
Fig 15-3m Another coronal section showing the communication of the
lesion from the posterior nasopharynx region (lower arrow) into the right
sphenoid sinus (upper arrow).
Fig 15-3n A sagittal view reveals a residual periapical lesion (arrow) on the
endodontically treated maxillary left second molar.
Fig 15-3o An osteophyte (arrow) is noted on C2 (axis).
Discussion of the case
It was recommended that the patient undergo an immediate otolaryngologic
evaluation as well as both conventional computed tomography and magnetic
resonance imaging to rule out a possible tumor. A differential diagnosis of
the tumor would have included chronic unilateral pansinusitis, antrochoanal
polyp, angiofibroma, and nasopharygeal carcinoma.
The extension of the soft tissue mass from the maxillary sinus to the
nasopharynx is consistent with an antrochoanal polyp. However, the
extension of the mass through the ethmoid complex and involvement of the
sphenoid sinus are atypical. It is possible that a long-standing antrochoanal
polyp could have blocked the osteomeatal complex and caused a retrograde
inflammatory change leading to sinusitis in the ethmoid air cells and
sphenoid sinus. Certainly the hyperostotic walls of the sphenoid sinus and
ethmoid complex support that hypothesis.
As for angiofibroma, it is a relatively common tumor of the nasal cavity
but more common in adolescence, often with epistaxis as a complaint. It
would be simple to confirm this possible diagnosis with magnetic resonance
imaging.
Nasopharyngeal carcinoma is rare in the United States. It is much more
common in China and the rest of Asia. Symptoms can include nasal
congestion, epistaxis, blood in the saliva, hearing loss, headaches, frequent
ear infections, and lymphadenopathy. Nasopharyngeal carcinomas are
classified into keratinizing and nonkeratinizing types, and the EpsteinBarr
virus is a known risk factor. The prognosis is influenced by the type of tumor
and of course the staging.
1 Unfortunately because of the rarity of this type of
tumor and the lack of symptomatology, the patient often has little indication
that anything is seriously wrong until the lesion is large and invading
structures secondarily.
The final histologic diagnosis in this case was a Schneiderian papilloma,
negative for squamous dysplasia.
Fig 15-4 Medial Arterial Calcification: Case 1
A 64-year-old woman was referred from a clinician in Illinois as part of a
diagnostic evaluation for obstructive sleep apnea. The review of the data
volume began in the axial plane of section, where calcification of the internal
carotid arteries was immediately identified (Fig 15-4a). Review of coronal
slices confirmed the extent of the calcification (Figs 15-4b to 15-4d).
Although intimal plaques are quite common in patients at this stage of life, in
this case, the widespread calcifications consistent with medial arterial
calcification (MAC) are more ominous. If carotid plaques are present
bilaterally in the cervical regions and the parasellar regions, the chances of
widespread MAC are significantly increased.
Fig 15-4a An axial view demonstrating bilateral calcification of the internal
carotid arteries in the parasellar region.
Fig 15-4b A coronal section showing the same arteries and the same
calcifications. Note the proximity of the structures to the condylar heads.
Clinicians who order CBCT volumes to examine the TMJ complex must
evaluate the sella turcica region.
Fig 15-4c These medial calcification changes must be delineated from the
anterior clinoid processes. The internal carotid artery ascends bilaterally past
the sphenoid sinus and past sella turcica. Thus, there is often the appearance
of four circular calcified vessels. Here, only three circular areas (arrows) are
visible.
Fig 15-4d A coronal section thickened to 10 mm demonstrates bilateral
carotid artery plaques (arrows) at the level of the C3 and C4 vertebrae. In
addition to significant carotid calcifications (cervical and parasellar
portions), there are physiologic calcifications of the pineal gland and
superior horns of the thyroid cartilage.
Discussion of the case
This patient was recommended for evaluation for undiagnosed or
uncontrolled type 2 diabetes mellitus as well as a compromised renal function
possibly secondary to the diabetic changes.
Diabetic patients with the kind of widespread vascular change evidenced
in this CBCT data volume are often candidates for below the knee
amputations in the near future.
2 Aggressive therapy including control of the
diabetes is mandatory to extend life and improve the quality of it. Dental
specialists who use CBCT and identify these types of changes are responsible
to refer their patients to medical care for proper management of undiagnosed
or uncontrolled diabetes.
In response to my request, the referring clinician forwarded the patient’s
medical history, which included a history of acid reflux, arthritis, high blood
pressure, heart disease, depression, sleep apnea, and sarcoidosis. The surgical
history included a tonsillectomy, extraction of wisdom teeth, and removal of
an ovarian cyst. Additional signs or symptoms recorded by the patient
included dizziness. The record of medications included losartan (angiotensin
antagonist), hydrochlorothiazide (diuretic), simvastatin (cholesterollowering
agent), fluoxetine (selective serotonin reuptake inhibitor, antidepressant),
ropinirole (nonergoline dopamine agonist, antiparkinson agent), tramadol
(centrally acting analgesic), and fenofibrate (cholesterol-lowering agent) as
well as multivitamins, calcium and magnesium supplements, fish oil, aspirin,
and glucosamine sulfate.
There was no mention of diabetes. The relationship between diabetes,
renal problems, and cardiovascular disease is well documented. The clinician
was advised to refer the patient to a primary care provider for evaluation of
dysglycemia and possible renal problems.
Fig 15-5 Medial Arterial Calcification: Case 2
A 74-year-old white man underwent a diagnostic evaluation for orofacial pain
including a possible TMJ disorder. The medical history included a history of
arterial sclerosis and diabetes. During the course of the evaluation, a large
field of vision (FOV) CBCT scan was ordered to evaluate the TMJ complex.
The patient was in no physical distress at the time in the evaluation. The
clinician identified mild osteoarthritic changes of the left condyle and C2
vertebral body. There was also a loose body in the atlantoaxial junction.
However, none of these osteoarthritic changes were the source of the
patient’s TMJ pain, and the clinician had decided that the patient’s symptoms
were due to a myofascial pain problem.
My review of the data volume began in the axial plane of section. Axial
and saggital views show graphic changes that could possibly relate to the
TMJ pain, including mild osteoarthritic changes in the facet joints between
C3 and C4 vertebrae (Fig 15-5a), in the dens axis (Fig 15-5b), and in axis
(Fig 15-5c). There was also indication of bilateral calcification of the
stylohyoid ligament complex (Fig 15-5d). However, further evaluation of the
CBCT data quickly revealed significant calcification changes. The location of
a small ovoid radiopacity posterior to the clivus (see Fig 15-5c) was unusual
and unexpected. A thickened sagittal view reconstructed as a maximum
intensity projection (MIP) image revealed a tubularlike structure consistent
with a vessel and MAC (Fig 15-5e). The location was intriguing, but my
familiarity with such findings in the cervical and parasellar portions of the
internal carotid arteries in other cases told me this could be another example
of MAC. The focus of this case had to be identifying MAC in significant
portions of the arterial tree (Figs 15-5f to 15-5h). Further investigation into
the unusual vascular pattern in the clivus region proved that these changes
were in the vertebral arteries ascending through the foramen magnum into the
brain (Figs 15-5i to 15-5n).
Fig 15-5a An axial view showing remodeling, subchondral sclerosis, and
subchondral cyst formation in the facet joints between C3 and C4 vertebrae
(arrow).
Fig 15-5b Subchondral cyst formation (arrow) in the dens axis seen in an
axial view at a superior level.
Fig 15-5c Small subchondral cyst (lower arrow) in C2 (axis) in a sagittal
section. Also, note the unusual small ovoid calcification (upper arrow).
Fig 15-5d Bilateral calcification of the elongated stylohyoid ligament
complex (arrows). Although there were no signs or symptoms suggestive of
Eagle syndrome, this finding would also be reported to the clinician for his
evaluation of the undiagnosed orofacial pain.
Fig 15-5e Slice data thickened to 20 mm and reconstructed using the MIP
tool to delineate the vascular calcifications (arrow).
Fig 15-5f A sagittal slice revealing calcification in the left internal carotid
artery (arrows) adjacent to the sella turcica.
Fig 15-5g A similar vascular calcification of the right internal carotid artery
(arrows).
Fig 15-5h Axial slice at the level of the sella turcica showing the bilateral
involvement of the internal carotid arteries (arrows).
Fig 15-5i Axial slice at the level of the inferior portion of the mandibular
condyles showing the typical circular pattern of MAC (arrows).
Fig 15-5j Thick section MIP image showing MAC of the vertebral arteries
ascending into the cranial cavity (lower arrows). Note also the physiologic
calcifications seen in the pineal gland (upper arrow) and choroid plexuses
(middle arrows).
Fig 15-5k 3D color reconstruction (20 mm) to characterize the calcification
of the vertebral arteries (arrows).
Fig 15-5l The Cube tool in the OnDemand 3D software (CyberMed
International) focusing on the vertebral arteries within the foramen magnum.
Fig 15-5m The Cube tool show the calcification of the vertebral arteries
(arrows) within the foramen magnum.
Fig 15-5n Thick slice coronal section using an MIP tool to show the typical
circular pattern of MAC in the internal carotid arteries (arrows) adjacent to
the sella turcica and just superior to the sphenoid sinus./
Discussion of the case
The medical history was requested after the CBCT volume had been
reviewed. The patient’s medical questionnaire had recorded difficulty
sleeping, impaired hearing, heart murmur, heart palpitations, hypoglycemia,
poor circulation, shortness of breath, sleep apnea, slow-healing sores, swollen
and stiff and painful joints, tired muscles, and heart disease. The patient also
recorded clinical signs and symptoms of dizziness and injuries to his neck
and back. Previous surgeries included back surgery, tonsillectomy, knee
surgery, and five coronary bypasses. Medications taken by the patient
included carvedilol (beta-blocker), fenofibrate (cholesterol-lowering agent),
oxaprozin (nonsteroidal anti-inflammatory drug) and oxybutynin (antispasmodic agent). With this history of heart problems, hypoglycemia,
dizziness, and slow-healing sores it is highly likely that this patient is also an
undiagnosed diabetic. It was necessary to recommend that the patient be
referred for evaluation for hypertension and stroke risk as well as
dysglycemia and potential end-stage renal disease.
Discussion of MAC Cases
Arterial calcifications in the medial layer of arteries are usually secondary to
compromised vascularity from type II diabetes mellitus. It can also signal that
a patient is approaching end stage renal disease.
3The type of calcification in
MAC is found in many other arteries in the body, but imaging it has never
been as easy as with CBCT. With the use of CBCT in dental imaging, it is
my belief that dental clinicians will be confronted more often with clear
evidence of arterial calcification. Intimal plaques such as those seen in the
pharyngeal space on panoramic radiographs are quite common, but the
plaques in the carotid arteries are only really visible in panoramic radiographs
when the patient is positioned just so and the resulting image layer is wide
enough to display it. However, there is no mistaking MAC findings on CBCT
images.
Clinicians who see evidence of arterial calcification in CBCT data
volumes should be ready to refer the patient to the primary care provider.
Anyone who reports MAC findings could be responsible for the initial
diagnosis of type 2 diabetes mellitus, for identifying a patient who is
noncompliant with diabetes treatment, or for saving the limbs of a diabetic
patient who is approaching end-stage renal disease. Just because a clinician is
evaluating an implant site does not provide absolution from reporting on
significant unexpected findings. Some of these findings will have an
immediate and direct impact on the patient’s systemic health.
Conclusions
Occult findings in CBCT data volumes are unavoidable, all are reportable,
and some may actually save your patient’s life. It takes only patience to
examine CBCT data in full. Significant findings can be found in data from
CBCT units with both small and large FOV, and clinicians are responsible for
everything recorded within the CBCT data volume.
If you are uncomfortable looking at the entire data set, the standard of
care dictates that you refer this task to a qualified oral and maxillofacial
radiologist or other dental specialist. In doing this you will ensure that your
patient receives the best care possible and avoid any potential liability from
an inadequate evaluation of the data.
A formal report should be included with every CBCT image set and
recorded in the patient’s record. Clinicians who examine their own CBCT
volumes can use simple reporting software to produce a concise and complete
CBCT report. Additional information concerning reporting software can be
found at any of these websites:
• www.EasyRiter.com
• www.learndigital.net
• www.OnDemand3D.com
References
1. Tabuchi K, Nakayama M, Nishimura B, Hayashi K, Hara A. Early
detection of nasopharyngeal carcinoma [epub ahead of print 8 June 2011].
Int J Otolaryngol 2011;2011:638058.
2. Schoppet M, Al-Fakhri N, Franke FE, et al. Localization of
osteoprotegerin, tumor necrosis factor-related apoptosisinducing ligand,
and receptor activator of nuclear factorκB ligand in Mönckeberg’s
sclerosis and atherosclerosis. J Clin Endocrinol Metab 2004;89:4104–
4112.
3. US Renal Data System. USRDS 2006 Annual Data Report: Atlas of EndStage Renal Disease in the United States. Bethesda, MD: National
Institutes of Health, National Institutes of Diabetes and Digestive and
Kidney Diseases, 2006.
Clinical Endodontics
Thomas V. McClammy, DMD, MS
The pace of adoption of cone beam computed tomography (CBCT) within the
specialty of endodontics was not anticipated by dental CBCT specialists,
1
endodontists, or even the manufactures and marketers of cone beam
technology. When the rst edition of this atlas was published in 2008, there
were relatively few articles concerning CBCT. However, it is now
commonplace to see numerous references to CBCT in every dental journal or
trade magazine, especially for endodontics. CBCT is here to stay and the
technology is only getting better and more user friendly to the benet of
patient care globally. This chapter discusses some of the areas that CBCT is
being used on a regular basis in clinical endodontics.
Fig 16-1 Misdiagnosis: Case 1
There is little question that lesions of endodontic origin
2
(LEOs) can be
visualized much better with CBCT than with conventional periapical
radiographs. It has been suggested that a thorough endodontic diagnosis
should include at least three well-angulated periapical radiographs,
3 and even
a bitewing radiograph can provide important diagnostic information in almost
every endodontic case. Nowadays, most multiangulated radiographs are
unnecessary when compared with CBCT data in multiple planes of section.
CBCT images provide much more information than what can be visualized in
radiographs, regardless of the angulation used.
A woman was referred for evaluation and potential endodontic treatment
of the maxillary right second molar, which had been restored with a relatively
new crown. Routine diagnostic testing of the tooth with cold, palpation, and
percussion indicated results within normal limits. However, a periapical
radiograph provided a glimpse of the adjacent anatomy, including a
suspicious radiolucency associated with the palatal root of the maxillary right
first molar (Fig 16-1a). Further diagnostic testing indicated that the maxillary
right first molar was indeed compromised. The tooth was sensitive to
percussion, did not respond to a cold test, and was tender when palpated on
both the buccal and the palatal sides. Offangle periapical radiographs
revealed radiolucencies indicating compromised periapical tissues (Fig 16-
1b).
Fig 16-1a Periapical image of the maxillary right second molar showing a
little of the maxillary right first molar.
Fig 16-1b Off-angle preoperative periapical radiograph of the maxillary
right first molar.
Following diagnostic testing, CBCT imaging of the maxillary right
quadrant was undertaken to better visualize the area and allow for a more
accurate diagnosis. The CBCT scan with a 40 × 40 mm field of vision (FOV)
was centered on the maxillary right first molar (Fig 16-1c).
Fig 16-1c CBCT slice of the maxillary right quadrant with radiolucencies
noted in all three planes of section and in a 3D volume rendering (upper
right). DB—distobuccal; MB—mesiobuccal.
The changes that were visible only vaguely on the conventional
radiographs became evident in the 3D CBCT imaging. The maxillary right
first molar was subsequently treated endodontically (Fig 16-1d). Pulpal
necrosis was confirmed when the root canal system was accessed.
Fig 16-1d The maxillary right first molar following endodontic therapy.
Fig 16-2 Misdiagnosis: Case 2
A man had been referred to numerous clinicians for evaluation because of
pain he experienced when flying. The patient, an avid fisherman, described
severe pain on the left side of his head, face, and neck that occurred even
when he flew at low altitudes in a float plane to his favorite fishing holes.
The pain was also present when he flew commercially as well as at other
times when he changed altitude. The referring dentist had focused his
diagnostic efforts on maxillary left first premolar, an abutment tooth for a
three-unit fixed prosthesis. The patient had also been referred to a neurologist
who had made a diagnosis of trigeminal neuralgia. There had been
discussions of neurosurgery to treat the trigeminal neuralgia and relieve some
of the pain.
Periapical images of the maxillary left first premolar and first molar did
not reveal any suspicious radiographic findings (Figs 16-2a and 16-2b).
Fig 16-2a Periapical radiograph of the maxillary left first premolar.
Fig 16-2b Periapical radiograph of the maxillary left first molar.
Diagnostic tests were initiated on the patient’s left side with an emphasis
on the maxillary left quadrant. Periapical and CBCT images did not
demonstrate anything significant or out of the ordinary. Pain of odontogenic
origin could not be reproduced. However, near the end the evaluation, the
patient mentioned that his mandibular left second molar was slightly tender
after this appointment. A periapical radiograph was taken of the mandibular
left second molar, which revealed some osseous apical changes (Fig 16-2c).
A CBCT scan was ordered (Fig 16-2d).
Fig 16-2c Periapical radiograph of the mandibular left second molar.
Fig 16-2d CBCT images showing osseous changes in all three planes (axial,
sagittal, and coronal) as well as in a 3D volume rendering (upper left).
Further diagnostic tests indicated that the pulpal tissues in the mandibular
left second molar were necrotic. At the next appointment, the root canal of
the mandibular left second molar was accessed, and the pulp was found to be
necrotic and noticeably putrescent.
In follow-up appointments, the patient indicated that he had not had pain
on his left side or any incidence of aerodontalgia since completion of the
endodontic therapy (Fig 16-2e). Without the benefit of CBCT imaging, the
misdiagnosis of this case could have resulted in an unnecessary neurosurgical
procedure.
Fig 16-2e perative periapical radiograph of the mandibular left second
molar.
Fig 16-3 Nonsurgical Retreatment
A 75-year-old woman was referred for an evaluation and potential
retreatment of the maxillary left first molar. Examination revealed a draining
sinus tract on the buccal side between the maxillary left second premolar and
first molar. Tracing that sinus tract with a gutta-percha cone indicated that the
area responsible was the mesiobuccal root of the maxillary left first molar. In
addition to other diagnostic tests, periapical and panoramic radiographs as
well as a CBCT of the maxillary left quadrant were taken. Both the periapical
and the panoramic radiographs increased the suspicion concerning the
maxillary left second premolar and first molar (Fig 16-3a).
Fig 16-3a Periapical radiograph of the maxillary left first molar prior to
retreatment.
There is tremendous value in using panoramic imaging for diagnosis.
Some CBCT machines allow a panoramic scout image to be taken prior to
scanning the full CBCT data volume. Not only does this facilitate a more
accurate positioning of the CBCT unit, but in certain cases a 2D panoramic
image can be an asset to the diagnosis and the potential treatment (Fig 16-
3b). A well-positioned panoramic radiograph can provide immediate
information about a patient’s previous dental treatment and offer a helpful
visual context to discuss preventive dentistry.
Fig 16-3b Panoramic radiograph highlighting the region of interest (ROI).
A CBCT scan was taken with a 40 × 40–mm FOV of both the maxillary
left second premolar and first molar as well as adjacent anatomy (Fig 16-3c).
The maxillary left second premolar and first molar both had very profound
LEOs. Slices in all planes of section (axial, coronal, sagittal) showed the
lesions (Figs 16-3d and 16-3e). Although the endodontic treatment of both of
these teeth looked clinically acceptable in some planes of section, these
images also showed significant periradicular osseous changes. Further
evaluation of these slices revealed missed canals in both teeth. Being able to
identify missed canals requires familiarity with the imaging software and
knowledge of what to look for. After all, the eye cannot see what the mind
has not taught it to recognize, and likewise clinicians can only see and treat
what they know. The CBCT scans in Figs 16-3c to 16-3e clearly illustrate a
missed second mesiobuccal canal.
Fig 16-3c LEOs (yellow arrows) on both the maxillary left second premolar
and first molar.
Fig 16-3d Coronal CBCT slice showing LEO on the maxillary left second
premolar (arrow). The missed mesiobuccal canal in the maxillary left
second premolar is also visible (circle).
Fig 16-3e Sagittal CBCT slice showing LEOs (arrows) on both the
maxillary left second premolar and first molar.
An untreated necrotic canal houses virulent pathogens and their byproducts. Under the right conditions, these pathogens can create periradicular
lesions. Periapical images sometimes reveal these lesions radiographically,
but CBCT slices allow early detection of these lesions and provide the
advantage of 3D visualization prior to surgical and nonsurgical treatment.
Clinicians can now know exactly where to look for missed canals prior to
creating the access cavity, which increases pretreatment confidence.
Treatment options were discussed with the patient, and she elected to
have the maxillary left first molar re-treated nonsurgically. Access of the root
canal system through the existing porcelain-fused-to-metal crown revealed
that the original endodontic treatment was quite good but that the second
mesiobuccal canal had not been accessed at all (Fig 16-3f). The process of
shaping and cleaning the root canal system of the maxillary left first molar
demonstrated that the second mesiobuccal canal was positioned under a hood
of dentin resting under the mesial marginal ridge, a common spot for second
mesiobuccal canals in maxillary first molars (Fig 16-3g). The canals were
filled with gutta-percha (Figs 16-3h and 16-3i).
Fig 16-3f All three canals, including the unaccessed second mesiobuccal
canal. DB—distobuccal; MB—mesiobuccal; P—palatal.
Fig 16-3g Endodontic access cavity of the maxillary left first molar after
shaping, cleaning, and thorough disinfection of the first and second
mesiobuccal (MB) canals and the distobuccal (DB) canal. Conservative
endodontic access cavities often do not allow visualization of all canal
orifices simultaneously, especially through a well-placed crown.
Fig 16-3h The root canal system was obturated with the vertical
condensation of warm gutta-percha. DB—distobuccal; MB—mesiobuccal.
Fig 16-3i Postoperative periapical radiograph showing the nonsurgical
retreatment of the maxillary left first molar.
Fig 16-4 Surgical Retreatment
Advances in technology have made most surgical endodontic retreatment
unnecessary. However, when apical surgery becomes necessary, a CBCT
volume provides the tremendous advantage of 3D visualization of the tooth
and surrounding anatomy prior to picking up the scalpel.
A 19-year-old patient was referred for evaluation and potential
endodontic treatment of the mandibular right second premolar. The
preoperative radiograph showed a significant periradicular radiolucency (Fig
16-4a). Vitality tests indicated that the pulp was necrotic. The tooth was
treated initially with conventional endodontic therapy. A draining sinus tract
in the buccal vestibule seemed to heal but returned within a few months of
the original treatment. Nonsurgical retreatment was completed to place
mineral trioxide aggregate (MTA) in the apical third of the root canal system,
which would make surgical endodontic retreatment easier if it proved
necessary
4
(Figs 16-4b and 16-4c). The draining sinus tract persisted and was
traced with a gutta-percha cone. Because apical endodontic surgery was
required, a CBCT scan was taken to provide 3D imaging prior to treatment
(Fig 16-4d). Knowing the exact location of important anatomical structures is
critical both for treatment planning as well as for the surgical procedure itself.
Fig 16-4a Preoperative radiograph of the mandibular right second premolar.
Fig 16-4b Placement of MTA in apical third of the mandibular right second
premolar.
Fig 16-4c Postoperative radiograph following nonsurgical retreatment.
Fig 16-4d CBCT scan taken prior to endodontic surgical retreatment
procedure. Axial (top left), sagittal (bottom left), and coronal (bottom right)
slices shown, as well as 3D rendering (top right).
The CBCT scan revealed a significant lesion in all three planes of section.
The apex was in close proximity to the neurovascular bundle and the mental
foramen. The coronal slice illustrated that although the lesion surrounded the
apical extent of the root, the buccal bone fenestration, and thus the location of
the draining sinus tract, was much more coronal. The midroot area was easily
accessed once a fullthickness flap was elevated. However, accessing the most
apical extent of the root required entry through 1 to 2 mm of buccal cortical
bone.
The apex of the root was accessed, and the root end was resected (Fig 16-
4e). Because the apical third of the root canal system had previously been
obturated with MTA, the surgery proceeded efficiently and in minimal time
(Fig 16-4f). Moreover, use of CBCT images of the mandibular right second
premolar prior to the surgery made the clinician confident in every stage of
the procedure.
Fig 16-4e Apical aspect of the mandibular right second premolar after root
end resection.
Fig 16-4f Radiographic image of the mandibular right second premolar
following apical surgery.
Fig 16-5 Resorption Defect
Prior to CBCT imaging, it was often difficult to provide a reliable prognosis
for a tooth with a resorption defect, regardless of whether the defect was
internal or external. However, CBCT scans allow clinicians to view the
defect in three dimensions. This is enough information to make an educated
preoperative assessment of resorption defects.
A 57-year-old woman was referred for evaluation of her maxillary central
incisors. The dental history indicated orthodontic treatment during her
teenage years and porcelain veneers on the maxillary anterior teeth from
canine to canine. The palatal aspect of the maxillary right central incisor was
extremely calcified and discolored. In radiographic examination, the
maxillary left central incisor appeared to have a resorption defect (Figs 16-5a
and 16-5b). A CBCT scan was ordered to assist with the treatment decisions
for both teeth.
Fig 16-5a Radiographic examination of the maxillary central incisors.
Fig 16-5b A closer look the maxillary left central incisior prior to treatment.
The calcification of the maxillary right central incisor was so complete
that even finding the canal was questionable. A CBCT scan can provide
important pretreatment information for significantly calcified canals. When a
calcified tooth is carefully viewed in the axial plane, the canal is usually
discovered somewhere along the length of the tooth. Once it is located in the
CBCT volume, the canal can also be found clinically with conservative
endodontic access and the use of a dental operating microscope.
At this point, the digital imaging and communications in medicine
(DICOM) files were sent electronically to an oral and maxillofacial
radiologist for an additional opinion as well as a written report on any occult
pathology. Figures 16-5c to 16-5e show images created by OnDemand 3D
software (CyberMed International) to analyze the DICOM data.
Fig 16-5c CBCT scans of the maxillary incisors showing the calcification of
the right central incisor and the resorption defect of the left central incisor.
Fig 16-5d Axial CBCT slice viewed using OnDemand 3D software to show
calcification of of the maxillary right central incisor with very faint evidence
of canal space remaining (arrow).
Fig 16-5e CBCT axial slice illustrating the contiguous resorptive defect,
externally and internally, of the maxillary left central incisor (arrow). The
extreme calcification of the right central incisor is also visible.
The maxillary right central incisor was treated endodontically; its single
canal was located, shaped, and cleaned. Because of the uncertain prognosis
for the maxillary left central incisor, the patient elected to have it removed
and have an immediate implant placed. Figure 16-5f shows the maxillary
right central incisor following endodontic therapy as well as the implantsupported provisional restoration in place of the maxillary left central incisor.
Fig 16-5f The maxillary right central incisor has undergone endodontic
therapy. The maxillary left central incisor has been replaced with an implant
and a provisional restoration.
Fig 16-6 Root Fracture: Case 1
Some manufacturers of CBCT machines purport that CBCT scans will allow
clinicians to see and diagnose all root fractures. Although many of these
statements are grossly exaggerated, there are some situations in which the
clinician can actually image root fractures clearly in CBCT scans prior to
treatment. More often, 2D radiographs and 3D CBCT data volumes do not
display fractures directly; rather, experienced clinicians know to analyze
imaging for evidence of root fractures such as bone destruction and
associated sequelae caused by bacterial invasion and the endotoxins they
produce. This is especially true when experienced clinicians use highresolution CBCT scans to image a suspected root fracture. CBCT imaging
can facilitate an accurate diagnosis of root fracture prior to treatment.
A 34-year-old woman was referred for evaluation of the maxillary left
second premolar treated 2 years previously with endodontic therapy.
Periodontal probing revealed a 7- to 9-mm pocket on the palatal side. Class
III mobility was evident. Radiographic analysis was inconclusive, but CBCT
imaging showed a palatal fracture (Figs 16-6a and 16-6b). The tooth was
extracted, and an immediate implant was placed with a provisional
restoration (Fig 16-6c).
Fig 16-6a Preoperative radiograph of the maxillary left second premolar.
Fig 16-6b Preoperative CBCT scans of the maxillary left second premolar
definitively illustrate a midroot fracture on the palatal side.
Fig 16-6c An immediate implant was placed and provisionally restored.
Fig 16-7 Root Fracture: Case 2
A 65-year-old woman was referred for evaluation of the maxillary right
lateral incisor. A clinical examination revealed that it had been previously
treated with surgical and nonsurgical endodontic therapy. The existing allceramic crown was retained intraradicularly by a post and core restoration.
The tooth exhibited Class III mobility, and a root fracture was suspected. In
addition to periapical radiographs, a CBCT scan was taken (Figs 16-7a and
16-7b).
Fig 16-7a Preoperative periapical radiograph of the maxillary right lateral
incisor.
Fig 16-7b Sagittal CBCT slice of the maxillary right lateral incisor clearly
showing the root fracture (arrow).
Although a fracture of this nature can sometimes be diagnosed with
conventional periapical images, CBCT scans provide additional benefits in
documentation and in aiding communication with the patient. Moreover, the
clinical information that can be used for treatment is substantial. Treatment
included removal of the fractured maxillary right lateral incisor and
immediate placement of an implant with a provisional restoration (Figs 16-7c
to 16-7e). The tooth was definitively restored with a porcelain-fused-to-metal
crown (Figs 16-7f and 16-7g). Root Fractures: Case 2 379
Fig 16-7c Labial aspect of the extracted maxillary right lateral incisor.
Fig 16-7d Sagittal view of the extracted maxillary right lateral incisor.
Fig 16-7e An implant was placed in the maxillary right lateral incisor site
and restored with a crown.
Fig 16-7f Implant-supported definitive restoration 16 months after
placement.
Fig 16-7g Coronal (left) and sagittal (right) CBCT slices showing the
maxillary right lateral incisor implant-supported restoration.
Fig 16-8 Unusual Root Canal Anatomy
Many times clinician’s would like to have another view of a tooth they are
considering treating. A clinician may even fantasize about having a tooth
extracted for just a few minutes just to have a look at its anatomy. While
temporary extraction is not possible, CBCT imaging does provide an
opportunity to visualize anatomy more precisely.
A 54-year-old man was referred for evaluation and possible treatment of
the mandibular left third molar. This molar was an abutment tooth for a
mandibular partial denture, and the patient expressed a sincere desire to save
the tooth. A periapical radiograph was taken (Fig 16-8a). It was quickly
determined that additional views including CBCT scans were necessary (Fig
16-8b).
Fig 16-8a Preoperative periapical radiograph of the mandibular left third
molar.
Fig 16-8b Preoperative CBCT scans of the mandibular left third molar
illustrating the challenging root canal anatomy. ML—mesiolingual; MB—
mesiobuccal.
The pulpal status of the mandibular left third molar was diagnosed as
necrotic, which was confirmed when endodontic therapy was performed. The
complexity of root canal anatomy increases exponentially from anterior teeth
to posterior teeth. This third molar was no exception and was a clinical
challenge. However, with enhanced CBCT imaging, patience, perseverance,
and disciplined application of fundamental shaping and cleaning principles,
the final result was well worth the effort (Fig 16-8c).
Fig 16-8c Periapical image of the mandibular left third molar after
endodontic treatment.
References
1. Miles DA, Danforth RA. A clinician’s guide to understanding cone beam
volumetric imaging. Acad Dent Ther Stomatol 2007;(special issue):1–13.
2. Schilder H. Canal debridement and disinfection. In: Cohen S, Burns RC
(eds). Pathways of the Pulp. St Louis: Mosby, 1976:111–133.
3. Kaffe I, Gratt BM. Variations in the radiographic interpretations of the
periapical dental region. J Endod 1988;14:330– 335.
4. Ruddle CJ. Nonsurgical endodontic retreatment. In: Cohen S, Burns RC
(eds). Pathways of the Pulp, ed 8. St Louis: Mosby, 2002:875–929.
Risk and Liability
The most controversial area of cone beam computed tomography (CBCT)
imaging is the issue of who is liable for examining the data volume once it is
captured. This should not be controversial. In an executive opinion statement
from 2008, the Executive Committee of the American Academy of Oral and
Maxillofacial Radiology stated that “it is the responsibility of the practitioner
obtaining the CBCT images to interpret the ndings of the examination. Just as
a pathology report accompanies a biopsy, an imaging report must accompany
a CBCT scan.”
1 This opinion is shared by both the American Association of
Orthodontists and the American Association of Oral and Maxillofacial
Surgery.
2,3The patient cannot sign away negligence. The clinician has an
obligation to review all of the data contained in a CBCT volume or to refer
the CBCT data set to either an oral and maxillofacial radiologist or medical
radiologist to review the volume for occult pathology.
Waiver of Liability
In one of the few articles specifically addressing medicolegal issues
associated with CBCT imaging, Friedland
4 discusses the issue of a waiver of
liability. Simply stated, the signing of any waiver of liability carries no legal
weight because the profession as a whole, not the individual clinician, sets
the standard of care that patients can expect. Anyone reading this textbook
would be well advised to read Friedland’s article.
Informed Refusal
Some clinicians believe that they can have a patient sign another type of
waiver called an informed refusal. The idea is that if a clinician stipulates that
the imaging is specific for a particular task, such as presurgical implant site
evaluation and the subsequent surgical procedure, the patient can waive the
clinician’s responsibility toward any data set outside of the stipulated
purpose. Unfortunately, the informed refusal waiver is also indefensible in a
courtroom.
In the California Book of Accepted Jury Instructions,
5
it reads:
It is the duty of a [dentist] who holds himself out as a specialist in a
particular field of [dental], surgical or other healing science, to have the
knowledge and skill ordinarily possessed, and to use the care and skill
ordinarily used, by reputable specialists practicing in the same field and
in the same or a similar locality and under similar circumstances. A
failure to fulfill such duty is negligence.
5
Under this definition, clinicians who interpret radiographic information
(including CBCT) are held to the same level of competence as a radiologist
because radiology is a recognized specialty within dentistry. Failure to read
the entire data volume is considered negligence. Thus, in a court of law, it
would be indefensible for a clinician to deny responsibility for an entire
CBCT data volume because he is not an oral and maxillofacial or a medical
radiologist.
Responsibility for Diagnosis
The issues of negligence and responsibility for CBCT scans are simple, but
understanding some of the statements that are made about these topics
requires a nuanced understanding. At the 2009 International Congress on 3D
Dental Imaging, Curley
6
told participants that “the risks and errors typically
found and assumed by patients with 2D imaging can be considered
malpractice and negligence since better technology is available.” In addition,
“dentists can recommend 3D imaging as an option without fears that they
could be liable for diagnosing everything seen on the image. They are only
responsible for those areas that are within the scope of their practice,
dentistry, jaws and oral cavity.”
6
Unfortunately, many attending clinicians depart these meetings thinking
that these statements absolve them from looking at the entire CBCT volume
or sending it to be read by a radiologist. Nothing could be further from the
truth. The lawyer is not saying you do not have to look at the volume. He is
saying you are not responsible for diagnosing everything in the volume. That
is a significant difference.
We are not required to diagnose everything on panoramic radiographs
either, but we do have to follow the American Dental Association (ADA)
standards of care: When you do not have the knowledge or skill to understand
what you are looking at, the standard is to refer.
7
In the 2011 revision of the
ADA Principles of Ethics and Code of Professional Conduct, under
consultation and referral, it states that “dentists shall be obliged to seek
consultation, if possible, whenever the welfare of patients will be safeguarded
or advanced by utilizing those who have special skills, knowledge, and
experience.”
7
So, a clinician cannot abrogate duty and responsibility by having the
patient sign a form to waive the need to refer the CBCT volume for
evaluation because the clinician is only reviewing that CBCT data for a
specific task. This is not informed refusal. If you have not looked at the data,
how can you inform the patient of anything that might be untoward in the
data? If you cannot inform the patient as to any of the potential risks from
occult pathology, how can they refuse? It is not enough to simply inform the
patient about the risks of the implant procedure. The following cases illustrate
a sample of some of the occult pathology that I have encountered over the
past few years.
Case Presentation 1
A 58-year-old white woman was referred to an imaging center for a CBCT
scan for temporomandibular joint (TMJ) analysis. In the axial images a mass
effect was noted in the right pharyngeal recess (fossa of Rosenmüller, behind
the ostium of the eustachian tube). Both a 3D color rendering and an audio
video interleave movie were created of this region where two large masses
were noted (Figs 17-1a and 17-1b) and reported to the clinician.
Fig 17-1a The lateral recess has been obliterated by a possible lesion
encroaching on the airway (arrows) on the right side.
Fig 17-1b This 3D reconstruction obtained using the 3D module shows one
large and one small elevation of a tumor (orange arrows). Note the
epiglottis (yellow arrow).
Case Presentation 2
A 57-year-old white woman underwent CBCT scanning because of exquisite
pain on palpation over the superior portion of the left mastoid process.
Several years earlier she had been diagnosed with breast cancer. She had
been treated with chemotherapy and lymphadenectomy. Because of this
medical history, the dentist repeatedly referred her to her medical providers to
investigate for metastases, but they countered that the probable diagnosis was
mastoiditis or otitis media and that a prescription for an antibiotic would be
sufficient. They even suggested that she might have a TMJ disorder. The
dentist referred the CBCT volume for analysis and requested that special
attention be paid to the region of the left ear. The data volume revealed
significant destruction of the medial portions of the left mastoid air cell
complex, which turned out to be one of several metastatic lesions (Figs 17-2a
to 17-2g). Other metastatic lesions were found with subsequent conventional
computed tomography and positron emission tomography scanning in her left
hip and liver.
Fig 17-2a The left mastoid air cell complex has lost the normal definition of
the air cells (upper left). Some sclerotic margins are also visible on the
TMJs (upper right). There is also some mild subchondral sclerosis on the
right condylar head (lower left).
Fig 17-2b An axial slice highlighting the changes in the left mastoid air cell
complex (arrow).
Fig 17-2c A coronal slice demonstrating changes in the left mastoid air cell
complex (arrow) as well as some perforation defects encroaching on the
lateral aspect of the mastoid process.
Fig 17-2d A sagittal slice near the medial pole of the right mandibular
condyle of the TMJ.
Fig 17-2e A sagittal slice just medial to Fig 17-2d showing gross destruction
of the posterior region of the mastoid process as well as radiopaque change
in the inferior portion within the cells. The faint outline of the mandibular
condyle head can be seen within the fossa in this image (arrow).
Fig 17-2f A 3D color reconstruction of the normal right mastoid process
using the Cube tool (OnDemand 3D software, CyberMed International).
Fig 17-2g A 3D reconstruction of the left mastoid process. The superior
portion reveals a perforation defect that has eroded through the bone
(arrow).
Case Presentation 3
An 81-year-old white woman was referred to an endodontist in Mesa,
Arizona, for evaluation of a radiographic radiolucency related to the
mandibular right first premolar that had been treated endodontically. In the
data volume taken by a limited field of view CBCT machine, the endodontist
also captured part of the mandibular right molar region. The patient was
asymptomatic. Regardless, the data volume was sent for a second opinion.
The first finding was the radiolucency associated with the mandibular right
first premolar (Figs 17-3a to 17-3d). The second was a pericoronal lesion
around the mandibular right third molar (Figs 17-3e to 17-3k).
Fig 17-3a Large radiolucency associated with the mandibular right first
premolar.
Fig 17-3b Continuation of the lesion to the mesial aspect of the root of the
mandibular right canine. The margins of the lesion are welldefined and there
are no internal calcifications.
Fig 17-3c The radiolucency associated with the mandibular right first
premolar seen in cross section.
Fig 17-3d From the distal aspect of the mandibular right first premolar, the
lesion shows thinning of the buccal cortex and small perforation defects on
the lingual aspect (arrows).
Fig 17-3e A pericoronal radiolucency associated with the mandibular right
third molar seen in axial section.
Fig 17-3f The coronal section shows the displacement of the molar and
thinning of the lingual cortical margin.
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Fig 17-3h A sagittal view from a more medial aspect showing expansion of
the lesion.
Fig 17-3i A 3D color reconstructed sagittal view, showing destruction of the
external oblique ridge.
Fig 17-3j A 3D color reconstructed sagittal view, showing destruction of the
external oblique ridge.
Fig 17-3k A 3D color reconstructed view attempting to show the soft tissue
of the cyst.
It is unlikely that these two radiolucent lesions are unrelated. The
presence of a pericoronal lesion around the mandibular right third molar
would give rise to the following differential diagnosis: dentigerous cyst,
odontogenic keratocyst, ameloblastoma, and, although more rare, a
mucoepidermoid carcinoma or even a squamous cell carcinoma. The
presence of another large lesion that has thinned or eroded the buccal or
lingual cortices and caused perforation defects suggests an odontogenic cyst
or ameloblastoma. Since the lesions could be related, it is more probable that
these are odontogenic keratocysts such as those seen in the nevoid basal cell
carcinoma syndrome. Even if these two lesions are separate, they are
significant.
After description of these lesions is completed and the differential
diagnosis is established, the patient has to be imaged again using a CBCT
machine with a larger field of view. In addition, confirmation of nevoid basal
cell carcinoma syndrome would require imaging of the chest and cranium to
search for indication of bifid ribs and calcified falx cerebri, respectively.
What is significant about this case from an imaging standpoint is that
both lesions were found in a data set taken by a CBCT unit with a small field
of vision. Even in a CBCT data set with a small field of view, there are often
significant findings for which the clinician is responsible, if not for diagnosis,
at least for follow-up. In this case, the patient was referred to an oral and
maxillofacial surgeon as well as to her primary care provider and a geneticist
for further evaluation. The clinician was responsible for locating and
describing the lesion and referring the patient for further evaluation. The
endodontist did not have to make the diagnosis of nevoid basal cell
carcinoma syndrome but was required to follow the standard of care of
referral.
Parting Comments
Dentistry has a new tool that will help clinicians to define the diseases and
disorders that they encounter with our patients. The CBCT technology
available to clinicians can improve presurgical planning and reduce the
patient’s morbidity and our liability. Clinicians can visualize the bony
changes caused by the pathology, capture sufficient presurgical anatomy in
such detail that they no longer have to fear placing implants, and determine
the precise location of the inferior alveolar nerve in relation to impacted
mandibular third molars. Now, at last, clinicians can visualize our patient
anatomy in a whole new manner—in three dimensions and in color.
References
1. Carter L, Farman AG, Geist J, et al. American Academy of Oral and
Maxillofacial Radiology executive opinion statement on performing and
interpreting diagnostic cone beam computed tomography. Oral Surg Oral
Med Oral Pathol Oral Radiol Endod 2008;106:561–562.
2. Turpin DL. Befriend your oral and maxillofacial radiologist. Am J Orthod
Dentofacial Orthop 2007;131:697.
3. Holmes SM. iCAT scanning in the dental office. Fortress Guardian
2007;9:2.
4. Friedland B. Medicolegal issues related to cone beam CT. Semin Orthod
2009;15:77–84.
5. Breckenridge PJ (ed). Book of Accepted Jury Instructions, ed 8. St Paul:
West Group, 1995.
6. Curley A. CBCT: Controversies in the Legal Standard of Care. Presented
at the 3rd International 3D Dental Imaging Congress, Chicago, 20 June
2009.
7. American Dental Association Principles of Ethics and Codes of
Professional Conduct. Chicago: American Dental Association, 2011.
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