APPLICATION OF COMPUTER ASSISTED SIMULATION TECHNIQUE TO ORTHODONTICS

为了研究颌面部复合体的形态与肌肉功能之间的关系，进一步了解咀嚼的意义和正畸治疗的生物学基础，我们开发了新的分析系统。该系统包括两个不同的组件：1)从每个受试者获得的包括咬压测量在内的计算机断层扫描（CT）数据中开发3D重建和自动FEM的系统；2)利用CT数据和肌电活动在颞下颌关节处的力矩计算，通过三维重建下颌骨来发展下颌运动的系统。四个正常的志愿者被研究。基线或原始测量数据来自三个来源：CT扫描、全咬合压力检测纸上的咬合力和数字记录的下颌运动。有限元分析是在32位计算机上自动生成的。自动有限元分析显示了每个个体在咬合过程中产生的应力分布。将CT图像中的坐标与运动检测器中的坐标进行变换和组合，生成重建下颌骨的运动图像。结果表明：正常受试者具有双侧对称的高剪应力区域分布。下颌畸形的年轻受试者表现出两侧应力分布的不平衡。这种不平衡在颌骨畸形的老年受试者中并不明显。在缓慢的最大打开和最大关闭时，颌骨畸形受试者的两个髁头的运动速度与正常受试者没有差异。这些计算机辅助程序可用于获得有关个体受试者下颌骨应力分布和髁突运动的临床有用信息。

In order to investigate the relationship among morphology and muscle function in maxillofacial complex, and further understanding of the meaning of mastication and biological basis of Orthodontic treatment, we have developed new analyzingsystems. The systems include two different components : 1) a system that develops 3D reconstruction and an automated FEM from computed tomography (CT) data obtained from each subject that includes bite pressure measurements ; and 2) a system that develops mandibular motion with a three-dimensionally reconstructed mandible using the CT data and moment calculation at TMJ from EMG activity. Four normal volunteer subjects were studied. Baseline or original measurements were obtained from three sources : CT scanning, biting pressure on full-occlusion pressure-detecting paper, and digitally-recorded jaw movements. The FE analysis resulted from automated generation of elements performed on a 32-bit computer. The automated FEM indicated stress distributions generated during clenching that were determined for each individual. Coordinates in the CT images and from the motion detector were transformed and combined to generate a moving picture of the reconstructed mandible. The results showed that the normal subjects had a bilaterally symmetrical distribution of regions with high shear stress. The younger subjects with mandibular deformities demonstrated a bilateral imbalance in distribution of stresses. This imbalance was not evident in older subjects with jaw deformities. The velocity of movement of the two condylar heads during slow maximum opening and closing was not different in the subjects with jaw deformities as compared to the normal subjects. These computer-assisted programs can be used to derive clinically useful information about stress distributions in the mandible and movement of the condyles in individual subjects.