Abstract: Objective · To develop a new point-based mandibular median sagittal plane (MMSP)selecting varied mandibular planes which were formedcombining bony landmarks derived multiple regions of the mandible. Methods · Forty adult patients were evenly divided into two groupsthe degree of chin deviation: mandibular asymmetric group (MA group) and mandibular symmetric group (MS group). Three dimensional (3D) mandibular models were rebuiltMimics 19.0 software. In this software, 3D coordinates of 4 central landmarks and 6 pairs of lateral landmarks were collected. Then 120 candidate planes were constructedpoint-based method, and compared with the reference plane formedthe iterative closest point (ICP) algorithm. All the planes were reordered and screenedgeometric indices such as angle, distance and area in MS group. In addition, the clinical symmetrical indices such as point-to-plane distance, surface area difference, volume difference, and 3D deviation ratio of screened planes were compared in MA and MS groups. Results · The candidate planes co-constructed with landmarks three mandibular regions (symphysis, mandibular angle and coronoid process) were the top 5% of all the planes. Among them, no statistical difference between B-Cor-Golat plane (constructed with supramentale, coronoid superius and gonion lateralis) and ICP plane was found (P >0.05), while there were significant differences between the rest screened planes and the reference plane (P<0.05). Conclusion · The B-Cor-Golat plane can be used as the mandibular median sagittal plane to reflect the symmetrical degree of the mandible well.

Key words: mandible, median sagittal plane, point-based plane, mandibular deviation