Sperl, Adam2020-09-082020-09-082020-06https://hdl.handle.net/11299/216100University of Minnesota M.S. thesis. June 2020. Major: Dentistry. Advisor: Thorsten Gruenheid. 1 computer file (PDF); vi, 42 pages.Introduction: Rapid maxillary expansion (RME) and fixed appliance therapy are commonly used to treat maxillary transverse deficiencies, but the treatment causes buccal displacement of appliance anchor teeth, which can damage the periodontium. Clinical decision making may be improved by better understanding how this treatment affects the periodontium. Objectives: The purpose of this study was to assess factors that might affect buccal bone changes adjacent to the permanent maxillary first molar after RME and fixed appliance therapy. Methods: Pre-treatment (T1) and post-treatment (T2) cone-beam computed tomography (CBCT) scans were obtained from 45 patients treated with RME and fixed appliance therapy. Measurements of buccal alveolar bone thickness adjacent to the mesiobuccal root of the maxillary first molar were made on CBCT images at 4 mm (B4), 6 mm (B6), and 8 mm (B8) from the CEJ. Anatomic defects of the buccal bone were recorded. T-tests were performed to compare T1 and T2 alveolar bone thickness and to determine whether teeth with post-treatment anatomic defects had thinner initial bone. Correlation analyses were conducted to examine the relationship between buccal alveolar bone thickness changes and the following variables: prescribed expansion, age at T1, time between T1 and T2, post-expansion retention time, and initial bone thickness. Results: There was a statistically significant reduction in buccal alveolar bone thickness from T1 to T2. 47.7% of teeth and 60% of patients had anatomic defects after treatment. Teeth with T2 anatomic defects had significantly thinner buccal bone at T1. Reduction in alveolar bone was correlated with only one tested variable: initial bone thickness. Conclusions: RME and fixed appliance therapy can result in a significant reduction in buccal alveolar bone thickness and an increase in anatomic defects adjacent to the expander anchor teeth. Anchor teeth with greater initial buccal bone thickness are likely to have a greater reduction in buccal bone thickness. Anchor teeth with thin initial buccal bone are more likely to develop post- treatment anatomic defects of the buccal bone plate.enBoneCBCTCone BeamExpanderRMERPEThesis or Dissertation