Pacific Coast Society of Orthodontists Bulletin Summer 2017 - 44

Presentation Summary

Impacted Maxillary Canines and CBCT:
Diagnosis and Management
Dr. Dawn Pruzansky
PCSO Bulletin Contributing Editor

Presented by Dr. Jae Hyun Park at the PCSO Spring
Training, March 3, 2017
Dr. Park began his lecture with a summary of
clinical applications of CBCT, based on a survey
of postgraduate programs, including:1
 Impacted/supernumerary teeth
 Craniofacial anomalies
 TMJ assessment

 Airway assessment

 Surgical treatment planning
 Clinical trials
Dr. Jae Hyun Park
Diplomate, American Board of
Orthodontics; Professor and Chair:
Postgraduate Orthodontic
Program, Arizona School of
Dentistry & Oral Health

Evaluation of root proximity is also an important
application of CBCT, since an 89% false positive
rate is seen when evaluating roots with
panoramic radiographs. Dr. Park also spoke of
buccal alveolar bone height assessment using
CBCT. If soft tissue is removed from the scan,
alveolar bone height measurements had similar
accuracy comparing 0.2 mm and 0.4 mm voxel
sizes. In the presence of soft tissue, however, the
0.2 mm voxel-size scans were more accurate than
0.4 mm.2 There is a risk of overestimating fenestrations and dehiscences on CBCT because thin,
cortical labial bone layers may not be detected.
Patcas et al. reported that if the mandibular anterior alveolar bone cannot be visualized on CBCT, it
is less than 1 mm thick.3
When considering maxillary anterior retraction,
the palatal bone must also be evaluated. Proclination of anterior teeth by 3 degrees will lead to
a 1 mm increase of overjet; the same is true of
retroclination and the resultant decrease in overjet. The anatomic limit to the retraction of maxillary anterior teeth is the pretreatment position of
the palatal plate.4 As a general guideline, hyperdivergent patterns will have thinner alveolar bone
housing than hypodivergent patterns.

Once an impacted canine is brought into the
arch, it is likely to experience issues with torque
(28%), gingival architecture (27%), and alignment
(17%).5 Once in retention, use of a labial bow on
the canine should be avoided during the retention stage, as it may aid in relapse/intrusion.
Labially displaced canines are more common in
patients with a hyperdivergent pattern. Additional characteristics include reduced maxillary
arch width and maxillary crowding. Only 17% of
labially displaced canines have sufficient space
for eruption.
In determining the length of treatment for
impacted canines, the angle and position of
impaction must be considered. Olive reported
that treatment can vary from 8 to 21 months,
depending on the zone in which the canine
crown is located.6 When the lateral incisor experiences root resorption, it typically (82%) occurs at
the middle third of the root.
The indications for when to use a CBCT image to
localize an impacted canine are:7
1.
2.
3.

Angle greater than 30 degrees
Root resorption in adjacent teeth is
suspected
Suspicion of dilaceration of the canine root

Zucatti et al. stated that age, distance from cusp
tip to occlusal plane, and beta-angle are indicators of treatment time. A patient over the age
of 25 will require more time. A canine located
in the mesial half of the lateral incisor will need
10 more visits than a canine located in the
distal half.8
If the angle of impaction is greater than 45
degrees, the canine may need extraction.7 In
this case, substitution or autotransplantation

PCSO Bulletin  Summer 2017

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