Download Using Cone Beam CT in Clinical Practice

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written for dentists,
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Using Cone Beam CT
in Clinical Practice
A Peer-Reviewed Publication
Written by Jeffery B. Price, DDS, MS
Abstract
As the 20th century ended and the 21st century began,
research groups were developing an imaging technology
that would forever change dentists’ ability to image
their patients. This technology is known as cone beam
computed tomography (CBCT).1-6 In this course we will
explore the technology and principles of CBCT and we
will compare the similarities and differences between
multi-detector CT (MDCT) used in medical imaging and
CBCT. We will also discuss some of the basics of radiation
dosimetry, as well as a few tools dentists can use to
educate their patients in the relative risks of CBCT. We
will also look at how CBCT can assist the practitioner with
advanced treatment planning. Finally, we will review
some of the ethical and medicolegal issues related to the
use of CBCT imaging in dentistry.
Educational Objectives:
At the end of this self-instructional education activity
the participant will be able to:
1. Discuss the basic technology and principles of
cone beam computed tomography (CBCT) for
dental use.
2. Review the commonly administered doses of
ionizing radiation patients receive during CBCT
examinations
3. List key selection criteria and indications for the
uses of CBCT in dental practice
4. Describe how CBCT examinations can enhance
advanced treatment planning
5. Identify two medico-legal and ethical issues
regarding the use of dental CBCT
Author Profile
Jeffery B. Price, DDS, MS is a Diplomate of the American Board of Oral & Maxillofacial
Radiology. He is currently an Assistant Professor of Oral & Maxillofacial Radiology and
Director of Oral & Maxillofacial Radiology at the Meharry Medical College School of
Dentistry in Nashville, TN; in addition, he is an Adjunct Associate Professor of Oral &
Maxillofacial Radiology at the UNC School of Dentistry in Chapel Hill, NC. Dr. Price practiced general and adult restorative dentistry in Hendersonville, NC for 24 years. While in
practice, Dr. Price completed the continuum at the L.D. Pankey Institute in Key Biscayne,
FL; in addition, he attained his Mastership in the Academy of General Dentistry as well
as Diplomate status in the International Congress of Oral Implantologists. Dr. Price is
currently on the editorial board of the ICOI-sponsored journal, Implant Dentistry; and, is
a reviewer for IJOMS, JDE and JADA. He can be reached at [email protected]
Author Disclosure
Jeffrey B Price, DDS, MS discloses that he is a consultant to Sirona Dental, the commercial
supporter of this educational activity. Dr. Price further discloses that he is a faculty
member for Sirona Galileos new users training and operates an internet consultation
service for Cone Beam CT interpretation.
Go Green, Go Online to take your course
Publication date: Apr. 2013
Expiration date: Mar. 2016
Supplement to PennWell Publications
PennWell designates this activity for 2 Continuing Educational Credits
Dental Board of California: Provider 4527, course registration number CA#: 02-4527-13018
“This course meets the Dental Board of California’s requirements for 2 units of continuing education.”
The PennWell Corporation is designated as an Approved PACE Program Provider by the
Academy of General Dentistry. The formal continuing dental education programs of this
program provider are accepted by the AGD for Fellowship, Mastership and membership
maintenance credit. Approval does not imply acceptance by a state or provincial board of
dentistry or AGD endorsement. The current term of approval extends from (11/1/2011) to
(10/31/2015) Provider ID# 320452.
This course has been made possible through an unrestricted educational grant by Sirona Dental Systems.
This course was written for dentists, dental hygienists and assistants, from novice to skilled.
Educational Methods: This course is a self-instructional journal and web activity.
Provider Disclosure: PennWell does not have a leadership position or a commercial interest in any products or
services discussed or shared in this educational activity nor with the commercial supporter. No manufacturer or
third party has had any input into the development of course content.
Requirements for Successful Completion: To obtain 2 CE credits for this educational activity you must pay the
required fee, review the material, complete the course evaluation and obtain a score of at least 70%.
CE Planner Disclosure: Heather Hodges, CE Coordinator does not have a leadership or commercial interest with
products or services discussed in this educational activity. Heather can be reached at [email protected]
Educational Disclaimer: Completing a single continuing education course does not provide enough information
to result in the participant being an expert in the field related to the course topic. It is a combination of many
educational courses and clinical experience that allows the participant to develop skills and expertise.
Image Authenticity Statement: The images in this educational activity have not been altered.
Scientific Integrity Statement: Information shared in this CE course is developed from clinical research and
represents the most current information available from evidence based dentistry.
Known Benefits and Limitations of the Data: The information presented in this educational activity is derived from
the data and information contained in reference section. The research data is extensive and provides direct benefit to the
patient and improvements in oral health.
Registration: The cost of this CE course is $49.00 for 2 CE credits.
Cancellation/Refund Policy: Any participant who is not 100% satisfied with this course can request a full refund
by contacting PennWell in writing.
Educational Objectives
At the end of this self-instructional education activity the
participant will be able to:
1. Discuss the basic technology and principles of cone
beam computed tomography (CBCT) for dental use.
2. Review the commonly administered doses of ionizing
radiation patients receive during CBCT examinations
3. List key selection criteria and indications for the uses of
CBCT in dental practice
4. Describe how CBCT examinations can enhance
advanced treatment planning
5. Identify two medico-legal and ethical issues regarding
the use of dental CBCT
Image Authenticity Statement: The images in this educational
activity have not been altered.
Known Benefits and Limitations of the Data
The information presented in this educational activity is derived
from the data and information contained in reference section.
The research data is extensive and provides direct benefit to the
patient and improvements in oral health.
Abstract
As the 20th century ended and the 21st century began, research
groups were developing an imaging technology that would forever change dentists’ ability to image their patients. This technology is known as cone beam computed tomography (CBCT).1-6
In this course we will explore the technology and principles of
CBCT and we will compare the similarities and differences
between multi-detector CT (MDCT) used in medical imaging
and CBCT. We will also discuss some of the basics of radiation
dosimetry, as well as a few tools dentists can use to educate their
patients in the relative risks of CBCT. We will also look at how
CBCT can assist the practitioner with advanced treatment planning. Finally, we will review some of the ethical and medicolegal
issues related to the use of CBCT imaging in dentistry.
Why CBCT?
If you are a dentist who has not yet experienced CBCT imaging, you may be asking, “What is all this excitement about?
Can CBCT really be that big of a deal?” Well, the excitement is
warranted because for the very first time in the history of dental
radiography, we are able to generate three dimensional images of
our three dimensional patients using x-ray machines in our own
offices at radiation doses lower than a traditional D-speed FMX!!!
No matter your perspective in dentistry, that is more than a big
deal; that is an ENORMOUS DEAL and for many dentists, it is
a practice and life altering experience!!! Let’s spend a little time
together and learn how this technology makes it possible for dentists to improve treatment outcomes on a more predictable basis.
First of all, what are some of the limitations of 2D imaging? The
two most commonly used forms of 2D, or plain radiography used
in dentistry are intraoral and panoramic imaging. Table 1 compares
Table 1. Differences between 2D Radiography and CBCT
Attribute
2D Imaging
CBCT
Depth of field
———
+++
Image magnification
———
+++
Connectivity w/ optical
—
+++
scans
Easily available
+++
+ (increasing)
Radiation dose
—
——
Key: +++ = excellent; ++ = very good; + = good; 0 = no effect;
- = negative attribute; -- = poor; --- = very poor
some of the advantages and disadvantages of 2D and 3D imaging.
The most important missing piece of information in periapicals
and panoramics or ‘2D problem’ if you will, is that the dentist does
not know the depth of field of the image. To put it another way, the
clinician does not know the width of the alveolar ridge in periapical
or panoramic images when treatment planning for dental implant
purposes; or, the mediolateral location of the mandibular canal
when evaluating the location of the apices of mandibular third
molars. Panoramic technology has innate imaging characteristics
such as parallax and non-uniform magnification.7-9 These endemic
problems result in images that are acceptable for the initial evaluation of our patients, but are inadequate for precise, detailed and
reliable implant planning or impacted tooth localization.10 Over
the years we have used localization techniques such as the buccal
object rule or the ‘same lingual opposite buccal’ (SLOB) technique
to localize root positions;9, 11-15 and we have worked around the
limitations of using panoramic images by using arbitrary magnification ratios to compensate for the 10 to 25% inherent variable
magnification seen in panoramic radiographs. When the task
demands precise localization, CBCT provides for non-distorted,
non-magnified reliable images for accurate diagnosis.
What is Cone Beam Computed Tomography?
Dental cone beam CT is a type of computed tomography that
uses a cone shaped x-ray beam for image exposure instead of the
standard fan shaped x-ray beam used in MDCT.9, 16-18 Figure 1
shows a typical CBCT machine with a schematic of the shape of
the cone shaped x-ray beam. The use of a cone shaped primary
x-ray beam to expose the patient results in raw images requires
slightly different processing algorithms than those used in routine MDCT imaging since the x-ray beam is collimated to a fan
shape in MDCT machines. Also, in CBCT imaging, the x-ray
source and receptor rotate an arc between 180° and 360° around
the patient while in MDCT, the x-ray source and receptor rotate
many times around the patient depending upon the region of interest. Additionally, in MDCT imaging the primary x-ray beam
and the remnant x-ray beam are both collimated, while in CBCT
only the primary x-ray beam is collimated. These and other technique characteristics result in distinct physical differences between MDCT and CBCT images; the most significant of which
is the difference in signal to noise ratio (SNR) between the two
techniques. MDCT has a SNR of approximately 90% while the
SNR for CBCT is approximately 15 to 20%. The result is that
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Figure 1: CBCT machine; note the schematic that outlines the cone
shaped x-ray beam
Figure 2. A Multiplanar Reconstruction (MPR) view consisting
of panoramic, 3D, parasagittal, coronal cross-sections and axial
reconstructions typical of most CBCT viewing software packages on
the market today.
Figure 3. A 3D volumetric rendering of a patient with multiple small
sialoliths within the left parotid gland and the left submandibular
salivary gland and duct.
CBCT provides excellent images of dense objects such as teeth
and bone while MDCT yields excellent images of the entire
range of objects seen in the human body from low density fluids
to soft tissues all the way to highly dense, calcified tissues.19-22
At first glance, this lack of soft tissue detail may seem to be
a disadvantage for CBCT; however, in dentistry most of our
diagnostic tasks are focused on teeth and bone—planning for
implants, localizing impacted maxillary canines and mandibular
third molars etc.; and as mentioned, CBCT imaging is an excellent choice for imaging these high density anatomic features. In
addition, CBCT provides images with soft tissue outlines from
which we can determine orthodontic and airway landmarks providing assistance with 3D diagnosis and planning. In actuality,
most diagnostic problems do not require the additional information of soft tissue details that MDCT can offer.
CBCT viewing software generally provides us with two types
of images — multiplanar reconstructed images (MPR) or 3D volumetric reconstructions. Figures 2 and 3 are examples of the types
of images you can expect from typical CBCT software. Once the
volumetric image is obtained, the computer processes this volume
into axial, coronal and sagittal slices which the user can then scroll
through, slice by slice. Many volumes are approximately 512 x
512 x 512 slices; the actual number of slices is dependent on the
scanning and reconstruction resolutions. Different types of 3D
volumes are obtained depending on the diagnostic task. The clinician may want to see the mandible and the maxilla for instance, or
may be interested in seeing outlines of the airway in an obstructive
sleep apnea patient. In addition, many software packages on the
market today are capable of virtual implant planning and placement whereby the user can place virtual implants into the CBCT
volume. These implant positions can then be used to order the fabrication of surgical guides to replicate the fixture positions during
implant surgery and guide the implant surgeon during surgery.23-28
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Radiation Dosimetry
Another major difference between CBCT and MDCT imaging technologies is the radiation dose required. Effective dose
is a term used to describe the relative risk of exposures to ionizing radiation and is calculated in microSieverts (μSv). Standard
MDCT images of the maxillofacial region result in radiation
doses that may range approximately 10 to 20 times higher than
CBCT images depending on the area imaged and the technique
factors utilized.29-31 Even though F-speed film is recommended
for routine use,32 many dentists still use D-speed film with round
collimation for their full mouth series technique; this examination results in an effective dose of ~388 μSv; or, three to five times
the radiation dose of many standard maxillofacial view CBCT
images.9 This relationship along with radiation doses from other
common radiographic examinations can be found in Table 2.
One fact that many people, medical and dental professionals
included, are not aware of is that we are exposed to ionizing radiation every day in our daily lives. Sources of background radiation
include cosmic radiation (gamma-rays, x-rays and beta particles)
and ingested food products, such as bananas with trace amounts
of radioactive potassium, etc.; but, the largest source of ionizing
radiation for many of us is radon which comes from basements
of buildings and other terrestrial sources such as building materials; i.e., concrete.33 Although it is far from perfect, an easy to
use tool for patient education is to use the average daily background
ionizing radiation exposure of 8 μSv per day as the denominator
3
Table 2. Radiation doses from common radiographic examinations
Effective Doses, Probability of Excess Fatal Cancer Risk per Million Examinations and Daily Background Equivalence from Dental
and Maxillofacial X-Ray Examinations
Technique
Dose
CA Risk per Million Exams
Background Equivalency
(microSieverts)
CA Risk per
0.8
1.7 days
Million Exams
Background
0.3
15 hours
Equivalency
35
2
4.4 days
8 μSv/day
171
9
21 days
Panoramic—indirect digital
14
0.8
1.7 days
Skull/Ceph—indirect digital
5
0.3
15 hours
FMX (PSP or F-Speed film—Rectangular collimation)
35
2
4.4 days
FMX (PSP or F-speed film—Round collimation)
171
9
21 days
FMX (D-Speed film—Round collimation)
388
21
47 days
One PA or BW (PSP or F-Speed; Rectangular Collimation)
2
0.1
6 hours
One PA or BW (PSP or F-Speed; Round Collimation)
9.5
0.5
1 day
One PA or BW (D-Speed; Round Collimation)
22
1.2
2.7 days
4 BWs (PSP or F-Speed-Rectangular Collimation)
5
0.3
15 hours
4 BWs (PSP or F-Speed-Round Collimation)
38
2
4.6 days
4 BWs (D-Speed-Round Collimation)
88
5
10.7 days
Tomogram (8 cm x 8 cm field of view)
10
0.5
1.2 days
Cone Beam CT exam (NewTom 3G — 12” FOV)
68
4
8.3 days
Sirona GALILEOS Comfort 15 cm x 15 cm x 15 cm
61
3.3
7.6 days
Sirona ORTHOPHOS XG 3D 8 cm x 8 cm
64
3.5
8 days
Sirona ORTHOPHOS XG 3D 5.5 cm x 8 cm (Maxilla)
41
2.2
5.1 days
Sirona ORTHOPHOS XG 3D 5.5 cm x 8 cm (Mandible)
52
2.9
6.5 days
Sirona ORTHOPHOS XG 3D 5.5 cm x 5 cm
30
1.7
3.8 days
Carestream 9300 8 cm x 8 cm of the Jaws
75
4.1
9.4 days
Carestream 9300 10 cm x 5 cm of the Maxilla
30
1.7
3.8 days
Carestream 9300 10 cm x 5 cm of the Mandible
56
3.1
7 days
Siemens Somatom 64 MDCT MaxilloMandibular Scan
2100
153
256 days
MDCT Maxilla Only
1400
102
171 days
Courtesy of Dr. John Ludlow
when determining the equivalent number of background days of
radiation in a particular radiographic examination. For instance, if
a CBCT resulted in a radiation dose of 80 μSv, the equation would
be 80 μSv/8 μSv per day = 10 days of background radiation equivalence, for patient education purposes. This is not a perfect system
since the background radiation in this example is spread out over
ten days while the CBCT radiation is delivered in 15 to 20 seconds,
but 80 μSv is considered a very low dose of radiation and again, the
rationale for using this system is to provide for a patient education
tool, not to defend a PhD dissertation in medical physics.
To summarize radiation doses with CBCT—remember, as with
most radiographic techniques, there is no ‘blanket’ statement—one
must compare various factors such as field of view, scanning resolution, technique factors of kVp, mA and time, etc. In general, CBCT
has significantly less radiation dose than MDCT; and, CBCT has
a slightly greater radiation dose compared to panoramic radiology
and optimized digital radiation with rectangular collimation.
Selection Criteria and When to Use CBCT
A common question that many dentists have when they begin using CBCT technology is how to decide when to use the technology.
It’s one thing to have this wonderful piece of equipment, but how
should a conscientious dentist who wants to avoid over-irradiating
his or her patients decide when to order cone beam scans? We will
look at what a few professional organizations have to say on the
subject and then explore a few other areas of dentistry.
In June 2012, the American Academy of Oral & Maxillofacial
Radiology (AAOMR) updated their recommendation on the use
of radiology for dental implantology purposes. Since 2000, the
AAOMR has recommended using some type of cross-sectional
imaging during definitive treatment planning for dental implantology cases.34 This recommendation originally referred to conventional tomography; but, now with the advent of cone beam CT,
CBCT is currently recommended as the optimal imaging choice
for the definitive treatment planning of dental implants by the
AAOMR.35 The main point to remember is that this statement is
not a standard of care; it is only a position statement and does not
take the place of a clinical examination and clinical judgment rendered by a provider. Many authors outline the differing opinions
and different types of implant cases for which to consider using
CBCT examinations. Perhaps the most succinct summary was offered by Benavides et al in an article published in Implant Dentistry
in April, 2012: “Because the 3D information obtained with CBCT
cannot be obtained with other 2D imaging modalities, it is virtually impossible to predict which treatment cases would not benefit
from having this additional information before obtaining it.”36
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In 2010, the American Association of Endodontists (AAE)
released a joint position statement with the AAOMR outlining the
use of cone beam CT for endodontic diagnosis and treatment planning.37 There are many indications for using CBCT, but a primary
tenet is to avoid the routine use of CBCT for the initial evaluation
of endodontic cases. In other words, use a low radiation dose
technique, such as a periapical radiograph, for initial evaluation.
If there are more advanced diagnostic problems such as a tooth
that requires re-treatment, complex root anatomy, suspected root
fracture or root resorption etc., then CBCT would be indicated. As
with all radiographic examinations, ensuring that the potential diagnostic benefit of the CBCT outweighs the risks of the additional
radiation exposure is important in endodontic imaging.
Using CBCT to evaluate orthodontic patients is a topic of discussion among many clinicians. Several post-graduate orthodontic
programs teach their residents to routinely expose a CBCT scan
on all orthodontic patients,38 yet many practicing orthodontists do
not support this approach. The crux of this issue revolves around
patient selection and the question of whether 3D radiographic
examinations with full 3D cephalometric analyses are indicated for
routine, Class I malocclusion cases with mild to moderate crowding for example. There are arguments pro and con on whether to
use CBCT routinely.39, 40 The official American Association of
Orthodontists (AAO) policy at this time is to use CBCT imaging selectively based on clinical judgment using factors such as
asymmetrical growth patterns, missing teeth etc.41 One significant
factor in this issue is the use of higher dose CBCT examinations
with younger patients who are more sensitive to ionizing radiation.42 Another factor is the lack of studies comparing the efficacy
of treatment outcomes of patients managed with routine 2D versus
3D cephalometry derived from CBCT volumes. The results of
these or similar studies have the potential to provide a great deal of
guidance on this issue.
There are many other uses for CBCT in the dental office—
TMJ examinations, localization of impacted teeth, evaluation of
pathology and areas of trauma etc. that are based on specific clinical
histories and examination findings. The dental professional must
use these findings in conjunction with an understanding of the
risks and benefits of CBCT imaging when deciding whether to
order a scan.
Risk to Benefit Analysis
The risk to benefit analysis is the key to making the decision to
order a CBCT scan or any other radiograph.9, 43-45 When you see
the word ‘risk,’ medical physicists actually mean the chance of
developing a fatal cancer. Effective dose was mentioned earlier and
values of effective dose for selected radiographic examinations are
given in Table 2. Effective dose allows us to compare the risk of a
dental CBCT with the risk of a chest x-ray or a MDCT of the head
or chest or any other radiographic examination for that matter.
For any diagnostic question the clinician needs to answer, if
CBCT is the modality that provides that answer with the lowest
radiation to the patient, then CBCT is the best radiographic examination to use. The benefit to the patient is that more accurate
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and/or more predictable treatment can be rendered in a safer,
quicker or more efficacious manner as a result of using CBCT
imaging. The final treatment is often the result of a more comprehensive diagnosis achievable only by the use of CBCT imaging.
In summary, since the risks of CBCT imaging are small; and, if it
is likely that the information provided by the CBCT scan will
improve the treatment outcome, then order the scan; however,
if the information will not affect the treatment outcome, then the
scan should not be ordered.
Advanced Treatment Planning
The literature is rife with examples of how to use CBCT for dental implantology;23, 26, 46-56 therefore, we will focus on advanced
treatment planning in other areas of dentistry. Figures 4 and 5
show a difficult to diagnose caries case in tooth #20. The reconstructed panoramic width can vary from a few millimeters to a
centimeter or more and will appear similar to a routine panoramic
within the alveolar ridge region. As you will notice, the coronal
aspect of #20 in the panoramic view does not reveal any alarming
amount of caries. In the cross-sectional view seen in Figure 5 you
will see a different story. Now that all the superimposed tissues
have been removed, you see a low density area representing deep
occlusal caries encroaching upon the pulp. Clinically there was
not a break in the enamel and although the referring clinicians
suspected incipient caries, they were not expecting the tooth to
require endodontic therapy.
Figure 4. CBCT panoramic reconstruction; note the normal appearance of
the coronal aspect of tooth #20 with mild periapical PDL space widening.
Figure 5. Note the significant change in density of the dentin between
the pulp chamber and the occlusal enamel, and proximity of the low
density dentin to the pulp chamber; in addition, there is slight widening of the PDL space with mildly increased periapical bone density.
5
Figures 6—9 are from an endodontic case showing selected
screenshots from a volume referred for implant treatment planning and an over-read. As you can see from the reconstructed
panoramic and multiplanar views, there are three endodontically
treated teeth that illustrate commonly seen entities on CBCT images. Figure 7 shows tooth #10 with a widened PDL space in the
apical region extending palatally with a mild effect on the endosteal surface of the palatal cortex. Figure 8 shows #15 with a widened
periapical PDL space that has affected the buccal cortical plate.
Figure 9 shows coronal and axial views of tooth #19, revealing an
untreated mesiolingual canal. Remember, these are all incidental
findings seen in a case referred for dental implant planning and
Figure 9. MPR views including a cross-sectional view of #19; note
the void in the area of the mesiolingual canal indicating a lack of an
endodontic filling.
Figure 6. Reconstructed panoramic of a CBCT case referred for implant
planning.
Figure 7. MPR views from the implant planning case shown in Figure
6, including a cross-sectional view of #10; note the widened PDL space
and mild thinning of the palatal cortex.
review by an oral radiologist, not for evaluation of these endodontically treated teeth. The recommendation in the radiology report
was for endodontic re-treatment of #19 and monitoring of teeth
#’s 10 & 15 since they were asymptomatic.
The next case is an example of maxillary canine localization
with evaluation of effects on surrounding teeth in a 15 year-old
female. Figure 10 is a conventional panoramic and Figure 11 is
a CBCT reconstructed panoramic. Large follicular spaces are
associated with the impacted maxillary canines. In addition,
there is significant resorption of the apices of the lateral incisors
as seen on the cross-sectional views in Figures 12 and 13. With
the information provided by CBCT imaging, a realistic approach
for moving these canines into the arch can be developed. Furthermore, the patient and parents can be informed as to realistic
expectations for the future of the lateral incisors.
Figure 10. A conventional panoramic radiograph with impacted
maxillary canines.
Figure 8. MPR views including a cross-sectional view of #15; note the
widened PDL space and the effect on the buccal cortical plate.
Figure 11. A CBCT panoramic reconstruction of the same patient from
Figure 10.
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Figure 12. MPR and volumetric views of impacted #6 with apical
resorption of #7.
Figure 16. MPR and volumetric views of the same patient from Figures
14 & 15; note the oblique fracture of the palatal root of tooth #4.
Figure 13. MPR and volumetric views of impacted #11 with apical
resorption of #10.
Figure 17. The oblique fracture of the palatal root of #4 is more easily
seen in this close-up cross-sectional view.
The next case is an example of a 67 year-old female who
presented to the clinic with intractable pain in the posterior
right maxilla. She reported seeing multiple dentists as well as a
neurologist. As noted in Figures 14 & 15, routine 2D imaging
does not reveal an obvious cause for her discomfort; however,
the cross-sectional view of tooth #4 revealed an oblique fracture
of the palatal root (Figures 16 & 17). The patient’s symptoms
improved dramatically upon removal of the tooth.
Figure 14. Conventional panoramic image to evaluate posterior right
maxillary pain.
The following case illustrates an area that we all need to
be mindful of—accessory neurovascular bundles. Figure 18 is
the reconstructed panoramic of a patient referred for implant
planning; a curvilinear corticated area of low density oriented
in vertical plane was noted palatal to the #12 implant site as
seen on the axial and coronal reconstructions (Figures 19 &
20). These are aberrant courses of the middle superior alveolar
neurovascular bundle and are occasionally seen in the maxillary premolar to canine region. The size of these neurovascular
channels are large enough to potentially cause significant
bleeding if injured during implant surgery; so, prior knowledge of their presence and anatomic location is quite important
for the implant surgeon.57-59
Figure 18. Reconstructed CBCT panoramic view of a case for implant planning. Note the fiduciary markers noting the planned implant locations.
Figure 15. Periapical radiograph of tooth #4.
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7
Figure 19. Axial slice through the maxilla; note the maxillary canine
root apices and the corticated area of low density palatal to tooth #11
denoted by the dotted orange circle.
Figure 20. A coronal reconstruction posterior to tooth #11 through the
corticated low density seen in Figure 19; a curvilinear, corticated low
density structure is seen coursing longitudinally through the maxilla
in the first premolar/canine region.
Figure 21. Routine periapical radiograph of tooth #9; this tooth had a
history of trauma three months prior to this radiograph.
Figure 22. MPR views with volumetric reconstruction of the trauma
patient seen in Figure 21.
Figure 23. Close-up sagittal views of tooth #9 revealing the communication of the endodontic lesion with the tissues within the floor of the
nasal fossa.
The final advanced treatment planning example is a
trauma case. A 17 year-old male who had suffered a bicycle
injury about 3 months previously was referred to the Oral
Diagnostic Services Clinic for advanced imaging to determine whether the periapical lesion associated with tooth #9
communicated with the nasal fossa. Figure 21 shows a PA
of tooth #9 with ~2 cm radiolucency in the periapical region
that extended along the distal root surface. Figure 22 is the
multiplanar reconstruction with panoramic, coronal, crosssectional and axial views showing different aspects of the
lesion. Figure 23 is the close-up cross-sectional view that
does indeed show decreased density of the cortical floor of
the nasal fossa as well as changes within the nasal mucosa,
both of which reflect a communication of this large periapical
granuloma or perhaps radicular cyst with the nasal fossa. This
tooth was treated with a conventional endodontic procedure
and is currently healing well.
These advanced treatment planning cases were chosen to
illustrate the unique imaging principles and value that 3D
CBCT imaging holds for the practicing dentist. Routine periapical and panoramic images were unable to provide the clinician with the advanced type of diagnostic information gained
from these CBCT images. CBCT technology enhances the art
and science of advanced interdisciplinary treatment planning
in a manner which is not currently available from other officebased imaging modalities.
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Medicolegal Issues
A recurring question at seminars and courses with clinicians is
whether all of the images contained in a CBCT dataset needs to be
reviewed. The AAOMR and many other authors have expressed
the opinion that the entire CBCT dataset needs to be reviewed.35,
43, 45, 60, 61
The basic premise is that a dentist is responsible for interpreting the entire content of periapical, bitewing, panoramic and
cephalometric radiographs. The only difference between these
radiographs and a CBCT is the volume of information contained
in the dataset. If the dentist does not feel comfortable assuming
the responsibility for reviewing the entire volume, referral to an
OMFR (Oral & Maxillofacial Radiologist) would be an option.
Continuing dental education courses are available through the
AAOMR and ADA Annual Sessions to assist CBCT machine
owners with interpretation training. In addition, owners of
CBCT machines should contact the manufacturer of their machine for information regarding training in not only operation of
the machine, but also a review of 3D anatomy, basic interpretation of CBCT volumes as well as a review of oral pathology.
A second question relates to management of incidental findings. An incidental finding can be defined as a radiographically
or clinically significant condition seen on a radiograph that is unrelated to the original diagnostic question or original purpose for
exposing the radiograph. Common incidental findings include
thickened maxillary sinus mucosa, antral pseudocysts, concha
bullosae, tonsiliths, enostoses, TMJ remodeling and undiagnosed periapical pathology,62, 63 Clinicians who are new owners
of CBCT machines face not only the challenge of learning, or
re-learning, these and other maxillofacial conditions, entities
and anatomic features, but they or their office staff must also
invest the added time and effort to manage referrals to the proper
healthcare provider for evaluation and/or follow-up. This is an
unexpected burden for many new CBCT machine owners.
Summary
Cone beam CT is arguably the greatest technological advancement that dental radiology has witnessed. The dental profession
now has the ability in virtually any dental office, on a daily basis,
to generate full 3D images of our patients’ dental and maxillofacial complex. These images are reliably accurate with no
magnification and unfettered by superimposition from other
anatomic structures. We can see individual teeth and supporting
tissues from any and all angles providing previously impossible
to achieve comprehensive oral and dental diagnoses. If you were
not excited about the potential for CBCT in your practice before
this course, I do hope that you now share the excitement of the
dentists who own and use CBCT technology, and hope that you
plan to utilize the technology in your practice!!
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Author Profile
Jeffery B. Price, DDS, MS is a Diplomate of the American Board of
Oral & Maxillofacial Radiology. He is currently an Assistant Professor
of Oral & Maxillofacial Radiology and Director of Oral & Maxillofacial Radiology at the Meharry Medical College School of Dentistry
in Nashville, TN; in addition, he is an Adjunct Associate Professor
of Oral & Maxillofacial Radiology at the UNC School of Dentistry in
Chapel Hill, NC. Dr. Price is also a consultant with Sirona Dental and
teaches many of their Galileos new users training courses. He also has
an internet-based Cone Beam CT interpretation practice. Dr. Price
practiced general and adult restorative dentistry in Hendersonville, NC
for 24 years. While in practice, Dr. Price completed the continuum at
the L.D. Pankey Institute in Key Biscayne, FL; in addition, he attained
his Mastership in the Academy of General Dentistry as well as Diplomate status in the International Congress of Oral Implantologists. Dr.
Price is currently on the editorial board of the ICOI-sponsored journal,
Implant Dentistry; and, is a reviewer for IJOMS, JDE and JADA.
Disclaimer
Jeffrey B Price, DDS, MS discloses that he is a consultant to Sirona
Dental, the commercial supporter of this educational activity. Dr.
Price further discloses that he is a faculty member for Sirona Galileos
new users training and operates an internet consultation service for
Cone Beam CT interpretation.
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Questions
1.The single most significant feature of cone
beam CT imaging is its ability to generate
what type of images?
a.
b.
c.
d.
Multiple panoramic images with different focal troughs
Accurate, non-magnified 3D images
Full face images with lateral and PA cephs
3D images of hard and soft tissues with equal diagnostic
efficacy
2.What feature makes CBCT different from
MDCT?
a. The type of x-ray photons
b. The shape of the x-ray beam—cone-shaped for CBCT
and fan-shaped for MDCT
c. The type of patient being imaged
d. The area of the patient being imaged
3.The ‘2D Problem’ refers to which of the
following?
a. The inability of 2D images such as periapicals and
panoramics to give information on the depth of objects
being imaged
b. Problems keeping the x-ray beam perpendicular to the
receptor
c. The problem of accurately tracking radiation doses
d. The two problems of magnification and geometric
distortion
4.Signal to noise ratio refers to
_________________?
a. The actual anatomic information (signal) contained in
an x-ray beam or image as compared to the amount of
scattered x-rays (noise).
b. The ability of an x-ray detector to determine hard
tissues from soft tissues.
c. The ability of CBCT to provide images with excellent
soft tissue contrast.
d. The ability of CBCT to improve noisy images so that
they can be of diagnostic quality.
5.Cone beam CT contains more scattered
radiation (more noise) than MDCT
techniques; how does this limit images taken
with CBCT machines?
a. CBCT images provide for excellent soft tissue contrast.
b. CBCT images provide for excellent hard tissue contrast
(bone and teeth).
c. CBCT images can provide excellent contrast for both
hard and soft tissues.
d. CBCT is a poor imaging technique because of this noise
and should no longer be used.
6.MPR is an acronym used in CBCT imaging; what does MPR mean?
a.
b.
c.
d.
Most Pixel Reduction
Many Pixel Resolution
MultiPlanar Reconstruction
Maximum Postal Reshaping
7.Which of the following statements best
describes the term effective dose?
a. A way to determine the penetrating ability, or effectiveness, of a radiation beam.
b. The dose of ionizing radiation as measured at the skin.
c. A dose of ionizing radiation measured in the organ; also
known as the organ dose, such as the thyroid dose in
dental x-rays.
d. A calculated, estimated radiation dose used to compare
the relative risks of various radiographic examinations
from chest x-rays to CBCT scans and dental BWs.
8.Which of the following has the highest
effective dose?
a.
b.
c.
d.
D-speed FMX with round collimation
A maxillofacial CBCT of 75 microSieverts
An average maxillofacial multidetector CT
An average panoramic x-ray
9.Background ionizing radiation is endemic;
which of the following is the largest source of
background radiation for the average person
in the U.S.?
a. Hydroxyl ions in water
b. Radioactive uranium from nuclear power plants
c. Radon from basements and building supplies like
concrete
d. Sunburns in the summer
10. The average daily background dose of
ionizing radiation for the average person in
the U.S. is approximately ________.
a.
b.
c.
d.
1 microSv
3 microSv
8 microSv
20 microSv
11. Approximately how many standard
maxillofacial CBCT scans would equal the
radiation dose of one FMX series taken with
D-speed film using round collimation?
a. About one maxillofacial CBCT scan per two D-speed
film-based, round collimation FMX series
b. About one maxillofacial CBCT scan per one D-speed
film-based, round collimation FMX
c. About two maxillofacial CBCT scans per one D-speed
film-based, round collimation FMX
d. About three to five maxillofacial CBCT scans per one
D-speed film-based, round collimation FMX
12. If the field of view of a standard panoramic
radiograph is used for comparison purposes,
which of the following types of radiographic
examinations would have the highest
amount of radiation per volume of tissue
exposed?
a. Routine panoramic
b. A standard maxillofacial CBCT scan of 300 micron
resolution
c. A high resolution maxillofacial CBCT scan of 100
micron resolution
d. Medical MDCT
13. The AAOMR (American Academy of
Oral & Maxillofacial Radiology) has recommended cross-sectional imaging for dental
implantology since ________?
a.1995
b.2000
c.2005
d.2010
14. The AAOMR currently recommends
_________ as the imaging modality of choice
for definitive dental implant treatment
planning.
a. Magnetic resonance imaging
b.MDCT
c. Periapical radiographs
d.CBCT
15. A guideline for use of CBCT in endodontics as well as other areas of dentistry is: .
a. First use a low-dose technique such as a periapical
radiograph for the initial evaluation of patients to avoid
routinely exposing CBCT scans on all patients
b. CBCT scans should be used routinely as the initial
radiographic examination for all patients
c. CBCT use is indicated as a screening tool when new
patients first come to the dental office
d. Use CBCT on any patient to replace BW’s, PA’s or
panoramic radiographs
16. A major principle of all radiographic
examinations is:.
a. To make sure the patient’s insurance will pay for the
x-ray.
b. To ensure that there is a reasonable expectation that
the radiographic examination will provide a diagnostic
benefit that will outweigh the risk of the radiation.
c. Use good batteries in your exposure controller.
d. Do not take the time to educate patients about radiation
safety.
17. All of the following may be reasons for
orthodontists to use CBCT technology;
which ONE is generally NOT agreed upon
by all orthodontists?
a.
b.
c.
d.
Evaluate asymmetrical growth pattern
Localizing impacted teeth
Evaluate condylar growth
Routine CBCT use on all orthodontic patients
18. Which of the following office routines
is considered the optimal routine when
considering radiographic examinations?
a. Take CBCTs on all new patients
b. Take a medical and dental history, perform a clinical
examination and then decide on the appropriate
radiographic examination to order
c. Use CBCT examinations just to see what you might
find
d. CBCT scans are indicated for all endodontic diagnoses
19. The key to making the decision to order a
CBCT scan is the ___________?
a.
b.
c.
d.
Risk to benefit analysis
Risk = return curve
Return on investment analysis
Radiation dose curve
20. According to medical physicists, the term
‘radiation risk’ means what?
a. The chance of developing a radiation skin reaction after
an x-ray exposure
b. The opportunistic infection that occurs after an x-ray
exposure
c. The chance of developing a fatal cancer after an x-ray
exposure
d. The chance that vascular disease will develop in the area
of an x-ray exposure.
21. A clinician should strongly consider ordering a CBCT scan if which of the following
is true?
a. The CBCT machine has not been used very much
recently.
b. The information provided by the scan will improve the
treatment outcome.
c. The information provided by the scan will not affect the
treatment outcome.
d. The patient requests a CBCT scan.
12www.ineedce.com
Questions
22. One of the treatment planning examples
showed a case of deep caries that was
obscured on the reconstructed panoramic
but visible on the cross-sectional images.
Why do you think the cross-sectional images
were better able to show the caries than the
panoramic image?
a. The panoramic image had more magnification
b. The panoramic image had more geometric distortion
c. The panoramic image had a thicker image layer and
therefore had more superimposed tissues within the
image thereby obscuring the caries
d. The cross-sectional image was a more accurate image
23. According to the case discussed in the
course, what difficulties do clinicians face
when using CBCT imaging to evaluate
endodontically treated teeth?
a.
b.
c.
d.
Widened periapical PDL spaces
Evaluate crown margins
Evaluate fit of custom posts
Evaluate for root resorption
24. Another treatment planning example using
CBCT imaging was maxillary canine localization. What valuable pathologic feature
besides canine localization was mentioned
during the discussion of that case?
a.
b.
c.
d.
Premolar transposition
Pulpal recession
Gingival recession
Resorption of the apices of the lateral incisors
25. One of the treatment planning cases
showed a fractured root on a maxillary
premolar. Why do you think routine 2D
imaging did not identify this fractured root?
a. Sclerotic pulp chambers
b. 2D imaging could not show the fracture within the correct long axis of the fracture; while in CBCT imaging,
we can see teeth from any view, at any angle
c. Poor radiographic technique by previous clinicians
d. Dense bone overlying the roots
26. What is the significance of undiagnosed
neurovascular bundles in proximity to
implant osteotomy sites?
a. There is no significance
b. Implants should not be placed
c. With proper technique, implant surgeons can vary
placement, if necessary, so that large neurovascular
bundles can be avoided to prevent intra- or postoperative bleeding
d. Since most of these are actually benign bone marrow
spaces and do not contain nerves and blood vessels, no
special notice is required
27. In general, why would a clinician choose
to use CBCT technology instead of 2D
technology?
a. To be able to see the patient in 3D so that advanced
diagnostic information can be obtained
b. Just to impress the patient with 3D images during the
consultation
c. To stay current with technology
d. To use the latest equipment
28. When considering the topic of whether
to look at only the area that the clinician is
interested in, or evaluating all the images
in a CBCT dataset, which of the following
statements best describes the recommendation by the AAOMR?
a. Practicing clinicians only need to look at the region of
interest in the CBCT scan and not bother with looking
at areas outside the region of interest.
b. Clinicians need to look at all the images in a CBCT
dataset; if they do not want to accept this responsibility,
referral to an OMFR is an option.
c. Clinicians only need to look at the 3D volume plus the
area of interest in the CBCT images and not the entire
CBCT dataset.
d. Clinicians only need to look at the panoramic
reconstruction and the area of interest in the CBCT
images and not the entire CBCT dataset.
29. Common incidental findings seen on
CBCT images include all of the following
except which ONE?
a. Thickened maxillary sinus mucosa
b. Antral pseudocysts
c.Tonsiliths
d. Intracranial aneurysms
30. Which of the following is the greatest technological advancement in dental radiology?
a.
b.
c.
d.
D-speed film
Automatic daylight loaders
XCP film holders
Dental Cone Beam Computed Tomography
Notes
www.ineedce.com
13
Notes
14www.ineedce.com
ANSWER SHEET
Using Cone Beam CT in Clinical Practice
Name:
Title:
Specialty:
Address:E-mail:
City:
State:ZIP:Country:
Telephone: Home (
)
Office (
Lic. Renewal Date:
) AGD Member ID:
Requirements for successful completion of the course and to obtain dental continuing education credits: 1) Read the entire course. 2) Complete all
information above. 3) Complete answer sheets in either pen or pencil. 4) Mark only one answer for each question. 5) A score of 70% on this test will earn
you 2 CE credits. 6) Complete the Course Evaluation below. 7) Make check payable to PennWell Corp. For Questions Call 216.398.7822
If not taking online, mail completed answer sheet to
Educational Objectives
Academy of Dental Therapeutics and Stomatology,
1. Discuss the basic technology and principles of cone beam computed tomography (CBCT) for dental use.
A Division of PennWell Corp.
P.O. Box 116, Chesterland, OH 44026
or fax to: (440) 845-3447
2. Review the commonly administered doses of ionizing radiation patients receive during CBCT examinations
3. List key selection criteria and indications for the uses of CBCT in dental practice
4. Describe how CBCT examinations can enhance advanced treatment planning
For immediate results,
go to www.ineedce.com to take tests online.
Answer sheets can be faxed with credit card payment to
(440) 845-3447, (216) 398-7922, or (216) 255-6619.
5. Identify two medico-legal and ethical issues regarding the use of dental CBCT
Course Evaluation
1. Were the individual course objectives met?Objective #1: Yes No
Objective #2: Yes No
Objective #3: Yes No
Objective #4: Yes No
Objective #5: Yes No
P ayment of $49.00 is enclosed.
(Checks and credit cards are accepted.)
If paying by credit card, please complete the
following:
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Please evaluate this course by responding to the following statements, using a scale of Excellent = 5 to Poor = 0.
2. To what extent were the course objectives accomplished overall?
5
4
3
2
1
0
Acct. Number: ______________________________
3. Please rate your personal mastery of the course objectives.
5
4
3
2
1
0
Exp. Date: _____________________
4. How would you rate the objectives and educational methods?
5
4
3
2
1
0
5. How do you rate the author’s grasp of the topic?
5
4
3
2
1
0
6. Please rate the instructor’s effectiveness.
5
4
3
2
1
0
7. Was the overall administration of the course effective?
5
4
3
2
1
0
8. Please rate the usefulness and clinical applicability of this course. 5
4
3
2
1
0
9. Please rate the usefulness of the supplemental webliography.
4
3
2
1
0
5
10. Do you feel that the references were adequate?
Yes
No
11. Would you participate in a similar program on a different topic?
Yes
No
Charges on your statement will show up as PennWell
12. If any of the continuing education questions were unclear or ambiguous, please list them.
___________________________________________________________________
13. Was there any subject matter you found confusing? Please describe.
___________________________________________________________________
___________________________________________________________________
14. How long did it take you to complete this course?
___________________________________________________________________
___________________________________________________________________
15. What additional continuing dental education topics would you like to see?
___________________________________________________________________
___________________________________________________________________
AGD Code 165
PLEASE PHOTOCOPY ANSWER SHEET FOR ADDITIONAL PARTICIPANTS.
COURSE EVALUATION and PARTICIPANT FEEDBACK
We encourage participant feedback pertaining to all courses. Please be sure to complete the survey included
with the course. Please e-mail all questions to: [email protected].
INSTRUCTIONS
All questions should have only one answer. Grading of this examination is done manually. Participants will
receive confirmation of passing by receipt of a verification form. Verification of Participation forms will be
mailed within two weeks after taking an examination.
COURSE CREDITS/COST
All participants scoring at least 70% on the examination will receive a verification form verifying 2 CE
credits. The formal continuing education program of this sponsor is accepted by the AGD for Fellowship/
Mastership credit. Please contact PennWell for current term of acceptance. Participants are urged to contact
their state dental boards for continuing education requirements. PennWell is a California Provider. The
California Provider number is 4527. The cost for courses ranges from $20.00 to $110.00.
Provider Information
PennWell is an ADA CERP Recognized Provider. ADA CERP is a service of the American Dental Association
to assist dental professionals in identifying quality providers of continuing dental education. ADA CERP
does not approve or endorse individual courses or instructors, nor does it imply acceptance of credit hours
by boards of dentistry.
Concerns or complaints about a CE Provider may be directed to the provider or to ADA CERP at www.ada.
org/cotocerp/.
The PennWell Corporation is designated as an Approved PACE Program Provider by the Academy of General
Dentistry. The formal continuing dental education programs of this program provider are accepted by the
AGD for Fellowship, Mastership and membership maintenance credit. Approval does not imply acceptance
by a state or provincial board of dentistry or AGD endorsement. The current term of approval extends from
(11/1/2011) to (10/31/2015) Provider ID# 320452.
RECORD KEEPING
PennWell maintains records of your successful completion of any exam for a minimum of six years. Please
contact our offices for a copy of your continuing education credits report. This report, which will list all
credits earned to date, will be generated and mailed to you within five business days of receipt.
Completing a single continuing education course does not provide enough information to give the
participant the feeling that s/he is an expert in the field related to the course topic. It is a combination of
many educational courses and clinical experience that allows the participant to develop skills and expertise.
CANCELLATION/REFUND POLICY
Any participant who is not 100% satisfied with this course can request a full refund by contacting PennWell in writing.
Image Authenticity
The images provided and included in this course have not been altered.
© 2013 by the Academy of Dental Therapeutics and Stomatology, a division of PennWell
CT413PAT
Customer Service 216.398.7822