Three-Dimensional Analysis of Mandibular Arch Form in Skeletal Class Ⅲ Facial Asymmetry Using a Digital Model

Abstract

Aim: Facial asymmetry not only affects the mandible, but jaw deformation also extends to the cranial base, maxilla, alveolar bone, and dentition. The position of teeth and the form of the dental arch, which are located on the alveolar bone, are also affected by jaw deformity. The purpose of this study was to analyze the tooth position and arch form of mandibular dentition in skeletal Class Ⅲ facial asymmetry patients. Materials and methods: Skeletal Class Ⅲ patients diagnosed with facial asymmetry who had undergone surgical orthodontic treatment were selected as subjects. The control group consisted of skeletal Class Ⅲ patients without facial asymmetry who had undergone surgical orthodontic treatment. Twenty patients (10 males and 10 females) were selected for each group. For evaluation, mandibular study models of selected patients were scanned using a laser scanner. Using a 3D digital model, the cusp-tip and facial axis points were projected on the occlusal plane, and point dimensions were measured using modeling software. Arch forms of the two groups were drawn and compared using a polynomial formula and compared. Results: In the molar region of the facial asymmetry group, the cusp-tip and facial axis points were located lingually on the deviated side and buccally on the non-deviated side, and a significant difference was indicated. A symmetric arch form was expressed with the 6 th polynomial formula in the facial symmetry group. Meanwhile, an asymmetric arch form with an S curve on the deviated side was expressed with a 6 th polynomial formula in the facial asymmetry group. Conclusion: This study confirmed that the asymmetrical arch form is caused by differences in transverse positioning of the molars in cases with skeletal Class Ⅲ facial asymmetry. facial asymmetry, mandibular arch form, pre-surgical orthodontic treatment