Study Of Chin Morphology In Angle Class ⅡDivision2Malocclusion After Orthodontic Treatment

Class Ⅱ division2malocclusion is a more common malocclusion deformity. Its main characteristics are as follows:distal molar relationship, anterior teeth lingual inclination and the locking bite. Compared with normal occlusion, relatively shorter mandibulars or relatively retrusive mandibular locations and shorter of the lower surface are always with such patients, which caused serious effects to oral aesthetics and functionality. With the development of X-ray cephalometry technology, the reasearch of Class Ⅱ division2malocclusion has been increased. But compared with other malocclusal abnormalities, such studies are still relatively fewer. In addition, these studies have focused on the relationship between the deformity and the condyle trajectory and temporomandibular joint disorders. The morphological changes of chin before and after the correction of the deformity is rarely reported by researches.The shape of the chin is one of the important clinically aesthetic indicators, it usually refers to the three-dimensional structures of the central body of the mandible and both sides before the mental foramen, including the middle joint, chin nodules, the spines on the chin, and the spines under the chin. Protrusion of the chin and the depth of chin lip groove have important implications to the coordination aesthetics of underface, and the size and morphology of the chin are related to the shape and position of soft tissue, and even to the whole profile appearance. This study was aimed to investigate the impact of orthodontic treatment to chin morphological changes of Class Ⅱ division2malocclusion patients, by analyzing X-cephalometric measurements of the deformity with non-extraction treatment before and after correction, to provide a reference and a basis for the treatment of such patients in the clinical.PURPOSE:To investigate the effects of orthodontic treatment on the changes of chin morphology in Angle Class Ⅱ division2malocclusion patients without tooth extractions.METHODS:A total of20patients with Class Ⅱ division2malocclusion were treated with straight wire appliance. Cephalometrics analysis was performed before and after treatment. The chin morphology, the position of the incisors and the porfile before and after orthodontic treatment were included in the analysis. Then the data was analysed statistically with PASW statistics18.RESULTS:With the correction of the lingually inclined maxillary incisors, the mandibular plane moved anteroinferior and the anterior lower facial height increased.The chin moved forward, the chin introcession, the depth of the mentolabial sulcus and the chin projection decreased. Upper Lip-E line and and lower lip E-Line became normal or close to normal. All of the cases showed up a better improvement of the profile after the therapy.CONCLUSION:In class Ⅱ division2malocclusion patients, after the lingually indined maxillary incisors were corrected,the chin position could be orthodontically changed and soft tissue profile will be improved esthetically.