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

Pacific Coast Society of Orthodontists Bulletin Summer 2015

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