Date of Award

2021

Department

Department of Orthodontics

First Advisor

Heesoo Oh

First Committee Member

Joorok Park

Abstract

Introduction: When skeletal transverse discrepancies exist between the maxilla and mandible, they commonly manifest in dental malocclusion. If left uncorrected, the malocclusion can lead to periodontal issues, tooth fractures, tooth loss, or other significant dental problems. Utilization of microimplants in palatal expansion aims to correct transverse discrepancies between the maxilla and mandible by separating the palatal suture in a parallel manner aimed at maximizing skeletal changes and minimizing dental side effects. Overlying soft tissue changes can be affected by the induced skeletal changes. The purpose of this study is to evaluate skeletal expansion and the overlying soft tissue change that occurs using MARPEs (microimplant assisted rapid palatal expanders) at the end of orthodontic treatment in skeletally mature (Cervical Vertebral Maturation (CMV) ≥ 5) patients using cone-beam computed tomography (CBCT) imaging and to evaluate soft tissue changes that occur at the time of orthodontic treatment completion using CBCT imaging. Materials and Methods: CBCT scans from 19 patients who were treated using microimplant assisted rapid palatal expanders were traced and evaluated at three time points: Before orthodontic treatment (T1), post MARPE expansion with MARPE in place (T2), and after orthodontic treatment with MARPE removed. Fourteen hard tissue landmarks and six soft tissue landmarks in the midface and nasal cavity regions were traced by three judges at each time point. The traced landmark points were averaged among all three judges and comparisons were made between the three time points to see the amount of expansion that occurred at various anatomical 2 regions. Intraclass correlation coefficient (ICC) was used to evaluate inter-judge reliability for all measurements. A repeated measures ANOVA test was used for statistical comparison across all three time points and a Tukey post hoc test was used for comparison between time points. Significance was set to .05 and ICC was set to >.70. Results: Expansion with microimplant assisted rapid palatal expanders can affect the hard tissue of the midface region as well as the overlying soft tissue. Increases in skeletal width from the ANS down to the maxillary alveolar bone were statistically significant in both the short term (T1-T2) and long term (T1-T3). The nasal cavity width at inferior turbinate area increased significantly after expansion (T2) and remained increased at treatment completion (T3) and the increased soft tissue width of the alar base that presented after expansion therapy remained increased at treatment completion. Conclusion: Maxillary expansion with microimplant assisted expanders resulted in skeletal changes throughout the maxilla and led to a significant long-term increase in nasal cavity width. The soft tissue changes associated with MARPE treatment show that a widening of the base of the nose may be expected after expansion and can remain at treatment completion.

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