Abstract: Objective: To three-dimensional analyze and classify the maxillomandibular asymmetry from jaw position and mandibular shape and to provide basis for clinical diagnosis and treatment using midsagittal plane of facial and mandible as the reference plane. Methods: The preoperative CBCT data of 86 patients with facial asymmetry were imported in Proplan CMF software to construct 3D model of bone tissue and 3D point measurement system. The characteristics of asymmetric deformity were analyzed from jaw position and mandibular shape and a new classification system was established. Results: Maxillomandibular asymmetry was divided into three categories: jaw position deviation, mandibular shape asymmetry, and both jaw position and mandibular shape deviation. Jaw position deviation included type T (transverse asymmetry) and type V (vertical asymmetry). In T1 and T3 groups, body length, ramus length, lateral ramal inclination, and frontal ramal inclination were significantly different between the deviated side and the contralateral side (P<0.01). The number of mandibular translational deviation cases was too small to be included in statistical analysis. In type V, frontal ramal inclination and ramus length were significantly different between the deviated side and the contralateral side (P<0.01). However, the others were not statistically significant. The differences of contour measurement items of two sides were statistical significance (P<0.05). Conclusion: The classification system of maxillomandibular asymmetry can provide clinical basis for diagnosis and treatment.

Key words: Maxillomandibular asymmetry , Midsagittal plane , Mandibular contour