Pacific Coast Society of Orthodontists Bulletin Spring 2023 - 29

Faculty Files
Figure 2. Distolateral tooth movement (mm) versus
time (day) for right and left maxillary canines moved
by 4 and 78 kPa, respectively, in a growing male subject.
These linear relationships for days 0 and ≥day
7 are characterized by slopes (y = speed in mm/day)
and R2
values
maxillary canine and a different stress was assigned
to the other side.
A total of 9 to 11 study visits were scheduled on
days 0, 1, 3, ±7, 14, ±7, 28, 42, 56, 70, and 84. At each
study visit, a modified gingival index (MGI) score8
was recorded to monitor inflammation; d between
hooks was checked to ensure target force delivery
and the coil spring changed, if indicated; and a
maxillary impression was made using a custom
tray and polyvinylsiloxane impression material to
construct a plaster model. Each subject, thus, had
nine to 11 models that were used with a three-axis
microscope and a custom set of three acrylic templates
containing reference markers that uniquely
fit the maxillary canines and posterior teeth, for
three-dimensional tooth movement measurements
over time.9
Data and Statistical Analyses
Height and cephalometric superimpositions
compared at the start and end of orthodontic
treatment determined whether subjects were
actively growing (G) or not (NG). Linear and angular
tooth movements for each maxillary canine versus
time were assessed to confirm that translation with
minimal side effects was achieved. Speed (mm/
day) of distolateral movement (as prescribed by
the orthodontic appliance) was calculated for day
Figure 3. Mean speeds of distolateral tooth translation
(mm/day) for five magnitudes of applied stress
(kPa) for a sample of 92 maxillary canines. Vertical
bars indicate ±standard deviations about the means.
The dotted line indicates the logarithmic relationship
with R2
= 0.962. Brackets denote significant differences
with specific P values as indicated.
0 as baseline and ≥day 7 because of the relatively
large movements at days 1 and 3 from compression
of the periodontal ligament following initial force
application. Means and standard deviations were
calculated, and t tests and analyses of variance with
post hoc tests were used to assess for variables that
significantly affected (P < .050) the speed of tooth
movement (converted to mm/month).
Results
Forty-six of the 48 subjects who gave informed
consent completed the study. The G and NG groups
included 36 patients (19 females, 17 males; aged
13.5 ± 1.7 years) and 10 patients (eight females, two
males; aged 19.2 ± 5.3 years), respectively. All 46 subjects
made at least eight study visits over a range of
76 to 107 days, 94% completed nine to 11 visits, and
67% followed the schedule within at least three days.
Stable posterior anchorage was confirmed by the fit
of the posterior template for each model in the set
of dental models for each subject. Root resorption
was not observed when radiographs from before
and after the study or orthodontic treatment were
compared. Average MGI scores for each subject were
<1, indicating gingival inflammation was low and
between absent and mild.
Distolateral movements at the end of the study
averaged 4.55 ± 1.95 mm overall and were linearly
Spring 2023 PCSO Bulletin
29
Pacific Coast Society of Orthodontists Bulletin Spring 2023

Table of Contents for the Digital Edition of Pacific Coast Society of Orthodontists Bulletin Spring 2023
