A Study On The Symmetry Of The Anterior Mandibular Body

This study aims to explore the optimal mandibular symphysis sagittal plane for patients with skeletal Class III mandibular asymmetry. Thirty-three orthognathic surgery patients with the skeletal Class III malocclusion were divided into the asymmetry group(n=15)and the symmetry group(n=18) . A digital three-dimensional model of the anterior mandibular body was established. Five types of mandibular symphysis sagittal planes(MSP1,MSP2,MSP3,MSP4 and MSP5) were constructed to calculate the overlap ratio (OR) of the anterior mandibular body three-dimensional entity and cross-section. The symmetry of the bilateral anterior mandibular body was analyzed to select the optimal mandibular symphysis sagittal plane. 1. In both asymmetric and symmetric groups, the overlap rate (or) of three-dimensional entity of anterior mandibular body calculated based on MSP3 plane was higher than that of MSP1, MSP2, MSP4 and MSP5 planes (p<0.05). 2. In both asymmetric and symmetric groups, the overlap ratio (OR) of the anterior mandibular body cross-section calculated based on the MSP3 plane was higher than that of MSP1,MSP2, MSP4, and MSP5 planes (p<0.05). 3.Referring to the MSP1, MSP3, MSP4, and MSP5 planes, there were no statistical differences in the symmetry of the anterior mandibular body between the asymmetry group and the symmetry group (p>0.05). The mandibular symphysis sagittal plane (MSP3) can be used to guide the repositioning of the deviated mandible in orthognathic surgery and set the mandibular occlusal plane goal in preoperative orthodontics treatment.