Incisor Inclination and Arch Width Changes Following Mandibular Setback Surgery for Correction of Mandibular Prognathism

Purpose: The aim of this study was to investigate and evaluate the changes of incisor inclination and arch width in the surgical-orthodontic treatment to correct a Class Ⅲ malocclusion resulting from skeletal mandibular prognathism. Materials and methods: The skeletal mandibular prognathism subjects consisted of 25 males and 20 females (mean age:22.8±4.2years). A lateral cephalogram was taken for each subject before preoperative orthodontic treatment (T1), presurgical (T2), and at completion of the postoperative orthodontic treatment (T3). Skeletal and dental values and arch width measurements at T1, T2 and T3 were obtained. Each cephalogram was traced and digitized twice. For statistical evaluation, all the data were expressed as Mean±Standard deviation and analyzed with SPSS software. Results: At pretreatment, dental compensation was normally found in both dental arches, including anterior and posterior teeth. During presurgical orthodontic treatment, most of the patient’s mandibular incisors were significantly decompensated (P<0.05), while no significant changes were noted in the maxillary incisors (P ≥ 0.05). The increase in maxillary inter-first molar width were statistically significant (P<0.05). With effective dental decompensation, the relationship between teeth and basal bone was improved obviously. It is beneficial for moving bone bulk in surgery. After the surgery, most of the patients (97.8%) finished with proper overjet and overbite, establish stable and harmony occlusion. Conclusion: By effective and proper dental decompensation, desired teeth positions could be achieved before surgery, which could lead to better surgical results.