Pacific Coast Society of Orthodontists Bulletin Spring 2015 - (Page 44)

SUMMARY ANNUAL SESSION CBCT: ASSESSMENT OF ANATOMICAL BOUNDARY CONDITIONS IMPORTANT TO ORTHODONTISTS Presented by Dr. David Hatcher, PCSO Annual Session, October 4, 2014. Summarized by Dr. Shahram Nabipour, PCSO Bulletin Central Region Editor. C one-beam computed tomography (CBCT) is a very good tool for observing anatomy. In one volume we can see how structures are anatomically and functionally related. When exceeded, some anatomic limitations may result in dental decline. Such limitations are referred to Dr. Hatcher as boundary conditions; three-dimensional (3D) volumetric imaging can be used to identify select anatomic boundaries. This imaging can also provide information as to how things are structurally, anatomically, and functionally related. The boundary areas Dr. Hatcher covered include: * Impactions * Roots and ridges * TMJ IMPACTIONS Dr. Hatcher notes that in cases of impacted teeth, a 3D volumetric CBCT scan can indicate to the clinician whether the affected tooth is labial or lingual, and thus determine exposure and mechanics; it can also serve as an essential image for the surgeon who will do the exposure. CBCT can reveal key anatomic features that will affect the orthodontist's decision-making, such as external root resorption of teeth adjacent to the impaction. Dr. Hatcher showed several such cases involving impacted teeth. ROOTS AND RIDGES In a clockwise facial growth pattern, in which the chin comes down and back, what factors (other than genetics) are involved? 44 Dr. Hatcher cites a study he directed at the University of California, San Francisco, in which orthodontic patients were put into one of three groups: low mandibular plane angle (MPA), average MPA, and high MPA (greater than 39 degrees). There were 25 patients in each group. The thickness of the alveolar ridge was measured at the root apex. The findings of the study showed that the steeper the mandibular plane, the thinner the alveolus at the root apex. The study also found that after completion of orthodontic treatment, the patients with thinner ridges (and higher MPAs) had more teeth moved out of the bone and also experienced more root resorption. Most orthodontists know that when a tooth is tipped or torqued and thus engages the cortex, it can undergo root resorption. This phenomenon has been recognized for some time, but Dr. Hatcher notes that there is now clear visual evidence of it through CBCT imaging. He then presented several cases showing the thinner alveolus on high angle patients, and the accompanying root resorption. TMJ When stress and strain are placed on teeth and bone, they adapt to their environment. By looking at these tissues via CBCT imaging, one can clearly visualize and uncover the underlying forces that could be responsible for changes within them. Most clinicians start the patient evaluation with the face. We search the face for asymmetries. Most often, our patients do present with facial asymmetries; some are mild, some are extreme, and most are in younger patients. The question is, what can cause the changes in younger people that then persist as asymmetries? When the temporomandibular joint (TMJ) is perturbed due to a local insult such as an arthritic change, a regional adaptation takes place in that area. Likewise, when such an insult to the joint takes place during growth and development prior to completion of somatic growth, the regional adaptation affects many regions of the face including the body of the mandible, the maxilla, the hyoid bone, the skull base, the temporal bone, and the occlusion. PCSO BULLETIN * SPRING 2015

Table of Contents for the Digital Edition of Pacific Coast Society of Orthodontists Bulletin Spring 2015

The Whole is Greater Than Its Parts
The Land of Opportunity
Donated Orthodontic Services Program — AAO-DOS
Trustee Report
AAO Council on Scientific Affairs (COSA) Report
Component Reports
AAOF Report
AAO Leaders Complete Terms in San Francisco: The End of an Era for PCSO
Preparing for the Unexpected: Your Emotional SOS Plan Part I
Resident Spotlight: Dr. Mona Afrand, Orthodontic Resident, University of Alberta Department of Orthodontics; Younger Member Spotlight: Dr. Mostafa Altalibi, Calgary, Canada
PCSO At A Glance
The AEODO Research Data Portal: Restructuring Workflow
The Aveolar Bone Housing — The Orthodontist’s World
Case Report Pre-Treatment
Smile and Appliance Esthetics — New Understandings
How to Remember Names and Places: A Dale Carnegie Program
The Latest Trends in Orthodontic Treatment: Part I
Training and Giving Feedback to The Clinical Staff to Ensure a Well-Tuned Team
Treatment Possibilities with Invisalign®
Class III Treatment: Timing and Protocol
Orthodontics: The Key to Successful Interdisciplinary Treatment
CBCT: Assessment of Anatomical Boundary Conditions Important to Orthodontists
Case Report Post-Treatment
Sectional Mechanics for Class II Correction
Dr. Donald Poulton

Pacific Coast Society of Orthodontists Bulletin Spring 2015