Pacific Coast Society of Orthodontists Bulletin Summer 2015 - (Page 20)
Special Section
Faculty Files
CBCT
Cone-Beam
Computed
Tomography
Dr. James Mah
Director of Advanced Education
Program in Orthodontics,
School of Dental Medicine,
University of Nevada, Las Vegas
Cone-Beam Computed Tomography
in Orthodontics-Benefits of
Comprehensive Visualization
Although cone-beam computed tomography
(CBCT), also known as volumetric computed
tomography (VCT), has been available in North
America for almost 15 years, it is still commonly
thought of as a new and emerging technology in
dentistry, and has not been universally adopted.
Quite possibly, the most significant barrier is lack
of education on the clinical applications of the
technology and the risk vs. benefit. Regarding the
former, this article will primarily focus on what
one sees with a CBCT evaluation of orthodontic
patients, and what one doesn't with conventional
two-dimensional imaging. A discussion of risk vs.
benefit - particularly in light of recent reports
on effective absorbed radiation dose from CBCT
- will be presented.
Imaging Goals in Orthodontics
At the heart of the matter is the topic of establishing imaging goals to comprehensively diagnose and treat orthodontic patients. Historically,
attempts were made as early as 1931 to provide
multi-dimensional imaging using Broadbent's
Orientator, which provided both lateral and
posteroanterior cephalometric views. Despite
numerous advances in imaging technologies,
there is no general consensus for imaging goals
in orthodontics. It is probably safe to say that
panoramic and lateral cephalograms are very
common, but use of the latter is occasionally
questioned. Some clinicians supplement these
views with occlusal and intraoral views, as well as
hand and wrist films. Quite likely, the choice of
image views is related to the goals of imaging
for a particular patient with a specific clinician.
Herein, there is considerable variation. In addition
to viewing the dentition and skeletal structures,
some clinicians are interested in more detailed
views of the temporomandibular joints, alveolar
morphology, and the airway.
Comprehensive Evaluation for
Comprehensive Treatment
As Dr. Peter Dawson observed, "90% of clinical
failures occur before treatment has begun."
The roots of his commentary are complex (pun
intended), involving patient assessment, diagno-
20
sis, and treatment planning. Among these issues
are the problems of misdiagnosis and incorrect
assumptions. Unfortunately, when we look at the
diagnostic sensitivity and specificity of conventional imaging for a number of diagnostic functions in orthodontics, the results are not good.
For example, in vitro evaluation of condylar surface erosions is at best 0.64 with panoramic
imaging; it is 0.95 with CBCT evaluation.1 Evaluation of three-dimensional (3D) alveolar morphology is next to impossible with conventional
imaging, yet studies of 3D bone morphology
show that there are many undetected bony
dehiscences and fenestrations - 51% and 39%
respectively - in a pretreatment group of orthodontic patients.2 Many other studies in dentistry
have reported the diagnostic accuracy of conventional imaging relative to CBCT. For the purpose
of brevity, not everything be presented here, but
the conclusions are identical. CBCT is superior in
all reports.
Certainly, one could take the position that "normal" or "routine" patients would not likely have
these problems, and conventional imaging would
likely suffice. One could take this a step further
and challenge whether any type diagnostic imaging has value. Such is the case with radiographic
evaluation for temporomandibular disorder
(TMD).3
The challenge for a clinician is how to determine
whether these patients are truly normal or routine without a comprehensive and thorough
evaluation. Assumptions can be made; most of
the time, these assumptions should be valid, but
that is the nature of a population distribution.
Some colleagues have proposed that Class I
malocclusions with mild arch length deficiency
should be considered normal, but there is no evidence to support the position that patients with
Class I malocclusions have fewer TMD, airway,
pathology, periodontal, or other problems. This is
a very "orthocentric" view of patients. Also, we
treat individuals, not populations, and by virtue
of a specialty, the types of patients seen by an
orthodontist are more complex and more likely
PCSO Bulletin Summer 2015
Table of Contents for the Digital Edition of Pacific Coast Society of Orthodontists Bulletin Summer 2015
Staying Connected in a Large, Diverse Orgainziation
Palm Springs: A PCSO Favorite
Trustee Report
PCSO at a Glance
PCSO Member News
AAOF Report
Special Section on CBCT
CBCT Imaging Protocols Within PCSO Residency Programs
Cone-Beam Computed Tomography in Orthodontics - Benefits of Comprehensive Visualization
Case Report Pre-Treatment
CBCT in Today's Orthodontic Practice
Case Report Post-Treatment
Differentiating Posterior Crossbites with CBCT Volumetric Images
Apps for the Orthodontist
Dr. Ib Leth Nielsen, San Francisco, CA
Dr. Robert J. Bendzak
Dr. Arthur A. Dugoni's 90th Birthday Makes for a Special Alumni Meeting in San Francisco
Preparing for the Unexpected: Your Emotional SOS Plan, Part II
Resident Spotlight
Hygiene: A New Battle for an Old War
Dr. Peter Picard, 1919-2013
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