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
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