Date of Award

2023

Department

Department of Orthodontics

First Advisor

Joorok Park

First Committee Member

Heeyeon Suh

Second Committee Member

Heesoo Oh

Abstract

Objectives: The purpose of this study is to determine the skeletal and dental contributions in the orthodontic correction of Class II subdivision malocclusions using cone-beam computed tomography (CBCT) analysis. Methods: 50 Patients that completed non-surgical orthodontic treatment at the University of the Pacific Graduate Orthodontic Clinic with initial Class II subdivision malocclusions were identified. Patients were classified as growing or non-growing, and further categorized if a skeletal asymmetry was present. Final records were assessed with 3-dimensional CBCT. Wilcoxon signed-rank tests were used to compare linear skeletal, angular, and dental measurement differences between pre- and post-treatment CBCTs on Class I and Class II sides. Results: Of 50 patients, 40 were treated with fixed appliances and 10 with clear aligners. Elastics were the most common Class II correction modality utilized. In growing patients on the class II side, the lower first molar (L6) mesialized by 1.57mm and extruded by 1.21mm (P< .005). In nongrowing patients on the Class II side, the L6 mesialized by .73mm (NS), and the upper first molar (U6) distalized by .52mm (P=.006). The results of a multiple regression analysis for growing patients revealed that only changes in U6 and L6 anterior-posterior positions on the Class II side had a statistically significant relationship with the amount of Class II correction. However, a positive correlation was observed between mandibular growth and L6 mesial movement (P= .0006) on the Class II side in growing group, suggesting that mandibular growth on Class II side contributed to Class II correction. Mandibular total length change between Class I and Class II sides did not show a statistically significant difference in both the growing group (P = .413) and total sample (P= .231). Conclusion: In patients with a Class II subdivision malocclusion with and without skeletal asymmetry, the Class I and Class II sides display differences that are mainly dentoalveolar. In growing patients, the Class II molar relationship was largely corrected by the mesialization of the L6. Growing patients with a skeletal asymmetry did not tend to grow more asymmetric. In non-growing patients, the Class II relationship was corrected by distalization of the U6 and mesialization of the L6. The correction of Class II subdivision malocclusion with and without skeletal asymmetry was achieved primarily by dentoalveolar effects.

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