APPLICATION OF COMPUTER ASSISTED SIMULATION TECHNIQUE TO ORTHODONTICS

为了研究颌面部复合体的形态和肌肉功能之间的关系，并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。这些系统包括两个不同的组件：1)系统，其根据从每个受试者获得的包括咬合压力测量的计算机断层扫描(CT)数据来开发3D重建和自动有限元分析；以及2)系统，其使用CT数据和根据EMG活动在TMJ处的力矩计算来开发具有三维重建的下颌运动的系统。研究对象为4名正常志愿者。基线或原始测量来自三个来源：CT扫描、完全咬合测压纸上的咬合压力和数字化记录的颌骨运动。有限元分析的结果是在32位计算机上执行的单元自动生成。自动有限元显示了咬合过程中产生的应力分布，这些分布是为每个人确定的。CT图像中的坐标和来自运动检测器的坐标被转换和组合，以生成重建的下颌骨的运动图像。结果表明，正常受试者双侧高切应力区域呈对称性分布。年轻的下颌畸形受试者表现出双侧应力分布的不平衡。这种不平衡在患有下颌畸形的老年受试者中并不明显。颌骨畸形患者在缓慢最大张开和闭合过程中，两个髁突头部的运动速度与正常受试者无明显差异。这些计算机辅助程序可以用来获得有关单个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.