[Study of chin morphology in Angle Class II division 2 malocclusion after non-extraction orthodontic treatment].

PURPOSE: To investigate the effect of non-extraction orthodontic treatment on the changes of chin morphology in Angle Class II division 2 malocclusion patients without tooth extractions. METHODS: A total of 20 patients with Class II division 2 malocclusion were treated with MBT straight wire appliance. Cephalometrics analysis was performed before and after treatment. The chin morphology, the position of the incisors and the profile before and after orthodontic treatment were included in the analysis. The data was analysed statistically with PASW statistics18. RESULTS: With the correction of the lingually inclined maxillary incisors, the mandibular plane moved anteroinferiorly and the anterior lower facial height increased.The chin moved forward, with introcession, the depth of the mentolabial sulcus and the chin projection decreased. Upper lip-E line and lower lip-E line became normal or close to normal. All cases showed a better improvement of the profile after treatment(P<0.05). CONCLUSIONS: In Class II division 2 malocclusion patients, after the lingually inclined maxillary incisors were corrected,the chin position could be orthodontically changed and soft tissue profile will be more esthetical.