Semester

Spring

Date of Graduation

2025

Document Type

Thesis

Degree Type

MS

College

School of Dentistry

Department

Orthodontics

Committee Chair

Peter Ngan

Committee Co-Chair

Khaled Alsharif

Committee Member

Khaled Alsharif

Committee Member

Guoqiang Guan

Abstract

Background and Objectives: Dental and skeletal Class II discrepancies are commonly associated with orofacial disharmony, and therefore appear in orthodontic clinics frequently. Class II correction for adults is generally limited to camouflage treatment with extractions, Class II elastics, Class II correctors, distalization, or orthognathic surgery in severe cases. The orthodontic field is constantly innovating to find efficient and effective means to correct class II malocclusions. The Carriere Motion Appliance TM was introduced in 2004 as an effective “distalizing” appliance to be used as a non-extraction approach to Class II correction for adolescent and adult patients. Recent clinical evidence suggests that most of the effects are dentoalveolar, and that some of the effects of the CMA can relapse after removal of the appliance and completion of comprehensive orthodontic treatment. The objective of this retrospective study was to evaluate and quantify the skeletal and dental effects of Class II correction with the CMA followed by comprehensive orthodontic treatment of Chinese adult patients with Class II malocclusions. Experimental Design and Methods: This retrospective study evaluated twenty-five post-pubertal patients with class II malocclusions treated with the CMA followed by either fixed appliances (five patients) or clear aligners (twenty patients). Orthodontic records were obtained from Dr. S.L.’s practice in Hong Kong. All patients had a full permanent dentition at the beginning of treatment. All patients were post-pubertal with a cervical vertebral maturation stage of either 5 or 6. Lateral cephalograms were taken before treatment (T1), immediately following class II correction and removal of the CMA (T2), and immediately following completion of comprehensive orthodontic treatment and removal of all appliances (T3). Angular and vertical skeletal changes were evaluated using the Dolphin imaging software; sagittal linear changes were measured by hand on T1, T2 and T3 digitally traced radiographs printed 1:1. Data were analyzed using a matched-pair t-test Wilcoxon signed rank test for the skeletal and dental changes across three timepoints. Two-sided p-values of ≤ 0.05 were considered statistically significant. Test-retest intra-rater reliability was assessed for two investigators using Pearson correlation coefficients (PCCs). Inter-rater reliability was assessed between two investigators using Intra-class correlation coefficients (ICCs). ICCs and PCCs ≥ 0.5 indicated moderate-excellent reliability. Results: Class II correction with the CMA took an average of 6.28 ± 1.9 months. Average total comprehensive treatment time for our patient sample was 32.2 ± 6.5 months. Overjet and molar relationship were significantly improved after Class II correction with the CMA. Treatment effects were primarily dentoalveolar, with no clinically significant skeletal effects; maxillary molars distalized, mandibular molars mesialized and extruded, mandibular incisors proclined, overbite was reduced, and the occlusal plane angle steepened. The mandibular plane angle increased slightly. After removal of the CMA and completion of comprehensive orthodontic treatment, molar correction relapsed somewhat due to slight mesialization of the maxillary molars. Overjet was further reduced. Overbite reduction, steepening of the mandibular plane angle, and proclination of lower incisors were somewhat recovered after removal of the CMA. Maxillary incisors were significantly retracted and retroclined. Lower anterior facial height did not change throughout the course of treatment. Conclusions: The CMA effectively improved molar relationships and reduced overjet in our sample of Class II adult Chinese patients. Molar correction relapsed slightly after removal of the CMA, however. Treatment effects of the CMA appliance were predominantly dentoalveolar. While some statistically significant skeletal changes were observed after Class II correction with the CMA and after completion of comprehensive treatment (decrease in SNB, increase in ANB, increase in mandibular plane angle), changes were minor and clinically insignificant. Lower facial height did not change over the course of treatment.

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