Pacific Coast Society of Orthodontists Bulletin Winter 2017 - 50

Presentation Summary

Doctors

Clinical Applications of 3-D Imaging
in Orthodontics
Dr. Morvarid Emamy

Presented by Dr. Juan Martin Palomo at the PCSO
Annual Session, Oct. 14, 2017
How and When to Use CBCT
Focus
One thing that sets CBCT apart from traditional
radiography is that everything does not have to
be seen at once; instead, focus can be placed on
the area of interest. In traditional radiography,
the practitioner sees all the information at once,
while in CBCT (or 3-D) imaging, the scan has different layers of information. If you make a cut
and look inside, additional information can be
found.

Dr. Juan Martin Palomo
Case Western Reserve University,
Cleveland, OH

The axial view of the dentition is an important
view retrieved from the CBCT; it can help with
finishing and differential torque. CBCT is a valuable tool for evaluation of bucco-lingual inclination of posterior teeth, and provides objective
information regarding the need for palatal
expansion.
The transverse dimension of maxillary and
mandibular arch can be accurately evaluated
using CBCT, while 2-D information may not be
sufficient to help with this evaluation.
3-D Superimpositions
Superimpositions are another clinical application
of CBCT. This has made it much easier to evaluate
growth compared to many years ago when
research like the Bolton study was conducted.
One of the most difficult challenges in orthodontic imaging is to separate growth from the effect
of treatment. The Bjork study provided orthodontics with many non-growing stable landmarks
that could be used after a certain age for an accurate superimposition. Refer to the ABO website
for further information and videos on superimpositions.
Superimpositions can be landmark-based,
surface-based, or voxel-based. Voxel-based
superimpositions are automated and use the
radiopacities and radiolucencies throughout the

selected volume, reducing the chance of operator
error, which is the main disadvantage of the
landmark superimposition method.
In traditional CT, there is a specific value for
each shade of gray. In CBCT, there is a number
assigned to each shade of gray; this is measured
in Hounsfield units which represent bone density.
Although these values are not calibrated in CBCT
and do not have diagnostic value, they are still
relative to each other and can be used for treatment planning.
How to Compare Two Methods of Superimpositions
Traditionally, orthodontists have measured different areas, but that is not the best approach.
When you work in 3-D, the answers are more
complete. The use of color mapping helps visualize the amount of change, providing a lot more
information than mere distances and angles.
As it turns out, for every superimposition, T1 is
unchanged, so the superimposed T2 image represents the change.
Superimposition can be a lengthy process. One
way to make it more efficient is to use commercially available software and have different views
of the head in all three planes of space, put a box
around landmarks that are not changing, such
as the anterior part of Sella and inner cortex of
frontal bone, etc., and then start the superimposition process.
The 3-D Airway
The airway can also be measured using 3-D imaging. In her sleep manifesto, The Sleep Revolution,
Arianna Huffington writes, "When you are well
rested, you rise undefeatable." Proper rest is
important to overall wellbeing. Airway problems
impact the quality of sleep. The apnea-hypopnea
Index (AHI) is used to indicate the severity of
sleep apnea; it measures the number of apnea
events per hour. Being a male, overweight, a
smoker, or having a family history of sleep apnea
means more risk of developing sleep apnea.
Forty-two million American adults have sleep

PCSO Bulletin  Winter 2017

https://www.americanboardortho.com/

Table of Contents for the Digital Edition of Pacific Coast Society of Orthodontists Bulletin Winter 2017