Volumetric Analysis Of The Alveolar Housing Around The Mandibular Incisors In Response To Class II Orthodontic Correction

• Author / Creator

  Chen, Kevin

• Introduction: The use of Cone-Beam Computed Tomography (CBCT) in clinical practice has seen a rise in recent years. Its usefulness as a diagnostic adjunct to traditional imaging modalities is undeniable, especially in orthognathic surgery planning, temporomandibular joint imaging, and in locating ectopically positioned teeth. CBCTs have also been used in the literature to study changes in response to growth and treatment. The primary objective of this study was to evaluate the volumetric response of the bony alveolus around the mandibular incisors to orthodontic camouflage in growing patients with mild to moderate Class II Division 1 malocclusions. Prognostic factors including vertical face height, lower incisor proclination, and appliance type were used to predict alveolar response. The secondary objective was to determine changes in incisor inclination as a result of ForsusTM and Xbow® application.
  Methods: The sample consisted of 43 growing patients with mild to moderate Class II Division 1 malocclusions (17 males and 26 females, mean age 13.53 ± 1.18 years). Each participant was randomly assigned to either ForsusTM group (N = 23) or the Xbow® group (N = 20). Pre-treatment (T1) and post-treatment (T2) records were collected in both groups including a full FOV CBCT scan, dental casts, intra- and extra-oral photos. Teeth 3.3-4.3 were segmented along with the anterior half of the bony mandible, and virtual models generated using ITK-SNAP, version 3.6. Based on landmarks which included the left and right mental foramen and B-point, 2 sagittal and 1 axial plane were created in SlicerCMF. These were used to define the boundaries of the region of interest, and the volumes were subsequently quantified. Mandibular incisor inclination (pitch) was also measured with respect to the defined axial plane. Six patients from the sample pool were randomly selected to validate and determine the reliability of the method using Intra-class Correlation Coefficient (ICC).
  Results: Intra-rater and inter-rater reliability was good (ICC>0.75). The median increase of the alveolar housing was 4.55% (p10.93° increased the likelihood of alveolar bone loss (95% confidence interval). Appliance type and vertical face height were not predictive of alveolar response. The average proclination of all of the mandibular incisors was 9.01° ± 8.74° (p < 0.05). There was no difference in average proclination between treatment groups, and all incisors proclined a similar amount (p > 0.05).
  Conclusions: In response to Class II correction, the overall volume of the alveolar bone increased in both treatment groups. Increasing incisor proclination was associated with decreasing alveolar volumes. Both Xbow® and ForsusTM appliances caused a similar proclination of the lower incisors. This study presented with significant limitations that may limit the clinical applicability of its conclusions.

• Subjects / Keywords

  • CBCT
  • Forsus
  • Class II
  • Recession
  • Orthodontics

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-796r-9885

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.