Change in horizontal mandibular position after gothic arch tracing in edentulous patients

本实验旨在探讨哥特弓描摹对无牙患者髁突位置的影响。结果如下：选择了三名20多岁的健康男性。采用6自由度K3DMS2系统记录下颌骨前缘、双侧缘运动和叩击运动，并编制了可定量分析哥特弓和叩击点的程序。该程序能够显示哥特弓描摹时的下颌运动，同时显示前、两侧描摹路径的长度、边界角、叩击点在哥特弓描摹路径上的重叠、十个叩击点的平均值、位置坐标、标准差和变异系数。记录6例无牙患者的前、双侧边界运动和下颌骨叩击运动，并记录哥特弓尖的咬合（记录A）。然后要求被试反复描画哥德拱，直到画出清晰的顶点，并记录咬痕（记录B）。记录A和记录B的髁突位置使用断层扫描记录。记录B的前缘和双侧边界运动长度明显长于记录a，记录B的最大叩击点直径明显小于记录a，记录B的髁位移指数明显小于记录a。由此表明，追踪哥特弓的实践带来了下颌骨运动的扩展，叩击运动的稳定性，叩击运动的稳定性。无牙患者髁突位置的改善。

The purpose of this experiment was to investigate whether the practice of tracing gothic arch influence the condylar position in edentulous patient. Results were the following.Three healthy males in the twenties were selected. The anterior and bilateral border movement and the tapping movement of the mandible were recorded by mean of the K3DMS2 system with 6-degrees of freedom, and a program that can analyzed quantitatively the gothic arch and the tapping point was developed. The program was able to display the mandibular movement during gothic arch tracing, and at the same time the length of the anteriorly and bilaterally traced path, the border angle, the overlapping of tapping point over the gothic arch traced path, the average point of the ten tapping points, its positional coordinates, standard deviation, and coefficient of variation.For the six edentulous patients the anterior and bilateral border movement and the tapping movement of the mandible were recorded, and the bite was recorded at the apex of gothic arch (record A). Then the subjects were asked to trace gothic arch repeatedly till making clearly apex, and the bite was recorded (record B). The condylar positions for the record A and the record B were recorded using a tomography. The length of anterior and bilateral border movement for the record B was significantly longer than that for the record A. The maximal diameter of tapping points for the record B was significantly smaller than that for the record A. The condylar displacement index for the record B was significantly smaller than that for the record A.From these results it was suggested that the practice of tracing gothic arch brought about expansion of mandibular movement, stability of tapping movement, and improvement of condylar position in edentulous patient.