Date of Graduation

2014

Document Type

Thesis

Degree Type

MS

College

School of Dentistry

Department

Orthodontics

Committee Chair

Peter Ngan

Committee Co-Chair

Chris Martin

Committee Member

Bryan Weaver

Abstract

Early orthopedic interventions have been advocated for patients presented with Class III malocclusion. However, many conventional treatment modalities have negative dental changes that accompany the positive skeletal changes. There is a lack of literature on comparing a new hybrid hyrax bone anchored maxillary protraction to conventional tooth anchored maxillary protraction. The objective of this retrospective study is to quantify and compare differences in craniofacial morphology, if any, between patients treated with tooth anchored versus bone anchored maxillary protraction. A total of 40 patients (16 males, 24 females) with Class III malocclusion who had received early orthopedic treatment with tooth anchored maxillary expansion and protraction or with bone anchored hybrid hyrax maxillary expansion and protraction were selected for the study. Lateral cephalograms were taken at the start of phase I treatment (mean age 9.8+/-1.6 for tooth anchored and 9.6+/-1.2 for bone anchored) and at the end of maxillary protraction. A custom cephalometric analysis based on variables described by Bjork and Pancherz, Mcnamara, Tweed, Jaraback, and Steiner was used. Data were analyzed using a one-way analysis of variance with p<0.05. Significant differences between the two groups were found in 8 out of 37 cephalometric variables after maxillary protraction (p<.05). Subjects in the tooth anchored group had more proclination of maxillary incisors, an increased overjet correction and molar relationship correction, an increased downward movement of A point, a decreased vertical position of the maxillary incisor, a increased opening of the articulare angle (S-Ar-GoI), an increase in mandibular plane (SNL-ML and FH-ML). These results show that there is similar forward movement of A point and the same amount of forward movement of the maxillary molars between the two maxillary protraction modalities. Based on the sum total of these results, the hybrid hyrax bone anchored maxillary protraction may be a better treatment alternative for Class III patients with a hyperdivergent growth pattern.

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