目的 ·应用点构法将下颌骨多个区域骨性标志点组合构建不同平面，从中筛选出对称性最佳者作为下颌骨正中矢状平面。方法 ·随机选取 40例成年患者，依据颏部偏斜程度分为偏斜组（ MA组，20例）和非偏斜组（ MS组，20例），应用 Mimics 19.0软件重建下颌骨 3D模型并描记 10组同名标志点，通过点构法构建出 120个待定平面。以迭代最近点（ iterative closest point，ICP）算法所构平面作为参考标准，在 MS组中依据角度、点距、面积等几何偏差指标进行排序初筛，在 MA组、MS组中通过对应点点距、表面积及体积差值、 3D偏差定值区间比率等临床对称性分析指标进行细筛，找出待定平面中对称性最佳者作为下颌骨正中矢状平面。结果 ·以正中联合前部、下颌角、喙突等区域标志点共同构建的平面排序位居总体前 5%。其中由下牙槽座点（ supramentale，B）、喙突顶点（ coronoid superius，Cor）、下颌角外侧凸点（ gonion lateralis，Golat）所构平面（ B-Cor-Golat）与 ICP平面间各项指标差值最小，且差异无统计学意义（ P>0.05），其余平面与参考平面间差异具有统计学意义（ P<0.05）。结论 · B-Cor-Golat平面能较好地反映下颌骨对称程度，在临床中可作为下颌骨正中矢状平面。

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.