Analysis of masticatory movements in children using three-dimensional dynamic simulation model

为了探讨口腔颌面功能的发育步骤，我们对正常牙合儿童的下颌运动、咀嚼肌活动、咬合面和咬合力进行了研究。这些结果说明，儿童的口腔颌面功能表现出与成人不同的特点。然而，为了通过治疗来评估生长儿童咬合功能的生物力学发育、错牙合功能障碍以及咀嚼功能障碍的恢复过程，对下颌运动的三维视觉估计在这方面将会给我们带来更多的好处。计算机仿真技术在工业领域中被广泛应用于固体结构的运动分析。该方法也被认为是分析牙齿、下颌牙列和牙齿接触情况的有用方法，但要将该方法应用于牙科领域，必须获得各种准确的参数来建立立体的牙列模型，以及咀嚼过程中下颌和头部的动态特性。本研究可以获得乳牙列的三维精确结构、咀嚼时咀嚼肌的肌肉活动平衡、下颌开合运动时的头部运动特征以及儿童乳牙反牙合的下颌运动特征。利用这些参数建立实体动力学模型，分析咬合接触情况。然后，利用计算机图形技术直观地显示乳牙列侧移时咬合接触面积的变化，量化每颗牙齿的咬合接触面积，并在工作侧和非工作侧工作侧与非工作侧的乳第二磨牙发生咬合接触，以计算机模拟的方法评估下颌运动情况。

In order to investigate the developmental steps of stomatognathic function, we have researched into mandibular movement, masticatory muscle activity, occlusal facet and occlusal force of children with of normal occlusion. These results clarified that children showed the different characteristics in stomatognathic function from adults. However, to estimate biomechanical development of occlusal function in growing children, dysfunction of malocclusion, and recovery process from the masticatory dysfunction through the treatments, the visual estimation of mandibular movements in three-dimensions must bring us much more benefits in this research aspect. The computer simulation technology is widely used for analyzing movements of solid structures in the industrial world. This method is also thought to be useful for analyzing teeth, mandibular dentition and teeth contact situation, however to apply this method into the field of dentistry, various and accurate parameters must be obtained to make solid dentition models, and dynamic characteristic of mandible and head during mastication. In this study, we could gain the three-dimensional precise structure on primary dentition, the muscle activity balance of masticatory muscles during chewing, the characteristics of head movement during open-close movement of mandible, and the characteristics of mandibular movement in children with primary anterior reverse bite. These parameters were used for making the solid dynamic models to analyze the situation of occlusal contact. Then, computer graphics were used to visually display changing occlusal contact area during lateral excursions in the primary dentition, the occlusal contact area of each tooth was quantified, and occlusal contact occurred at the primary second molars on both the working and non-working sides during lateral excursion.Further studies are needed to evaluate the mandibular movements using computer simulation.