Root parallelism in Invisalign® treatment
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Date
2015
Authors
Nemes, Jordan
Journal Title
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Abstract
AIM: To assess root parallelism after Invisalign® treatment.
MATERIALS AND METHODS: The sample consisted of 101 patients (mean
age: 22.7 years, 29 males, 72 females) treated non-extraction with Invisalign® by
one orthodontist. Root angulations were assessed using the 4-point angulation
tool (Dolphin imaging©); the long axes of adjacent teeth were traced, yielding a
convergence/divergence angle. Acceptable root parallelism was assessed if the
root angulation did not converge/diverge more than 7 degrees. Sites evaluated:
between 1st molars and 2nd premolars, 2nd and 1st premolars, lateral and central
incisors, and between central incisors in all four quadrants. The average change
in mesio-distal root angulation was assessed between pre- and post-treatment
panoramic radiographs.
RESULTS: Paired t-tests were used to analyze the average change in mesiodistal
root angulation. Statistically significant differences were obtained indicating
a reduction in the convergence/divergence angles between teeth #16-15, #15-14,
#11-21, #24-25, #25-26, #45-44, #42-41, #41-31, #31-32, and #34-35 (at p-value
<0.05). The average change in root angulation was not affected (p>0.05) by age
(Pearson correlation coefficient), gender, occlusion type (I, II, or III), or elastic
use (unpaired, 2 sample t-test at p<0.05). Intra and inter-rater reliability for 20%
of the studied sample was assessed using the interclass correlation coefficient
3
test. All measured areas except teeth #16-15, #26-25, and #36-35 yielded good
ICC reliability scores above 0.7.
CONCLUSION: Root parallelism was improved post-Invisalign® treatment in ten
of the fourteen areas evaluated. Thus, Invisalign® may be an effective treatment
modality in controlling root angulation in non-extraction cases.
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Keywords
Invisalign, Root, Parallelism, Orthodontic