Experimental data acquisition and Finite Element Analysis of kinetic aspects of functional occlusion in order to optimize dental reconstrucions

正确的咬合是制作牙科矫正器的一个重要方面。由于牙科技师在口腔外生产修复体，因此必须将下颌骨的运动准确地转移到牙科实验室条件下。然后可以产生没有干扰并且具有足够咀嚼能力的牙齿清洁。近年来，越来越多的假体重建已产生的CAD/CAM。这使得能够特别关注患者的个体功能状况。然而，只有当运动学（=运动和变形）和动力学（=力和应力）数据都被记录下来时，才能利用这个巨大的优势。不幸的是，到目前为止，运动学数据，专门，已被记录，因此，用于构建牙科修复。牙齿的运动，下颌骨的变形，牙周间隙和关节盘的变形，包括所有涉及的组织，在运动和咀嚼过程中，以前不能被记录。此外，还没有关于牙齿咀嚼、紧咬和/或磨牙（磨牙症）过程中这些动力学的个体信息;这些信息可能是必不可少的，因为在这些活动中会产生非常高的偏心力，导致所有陶瓷或镶面牙科修复体失效的风险很高。在这种情况下，考虑到上述动力学方面，修复体的无干扰咬合是强制性的。在本研究中，将通过采集咬合/咀嚼力、肌肉电活动、下颌运动和MRI图像，采集22名健康受试者的缺失动力学数据。这些数据将能够改善现有的有限元模型（FEM）的口颌系统，包括颞下颌关节，所有咀嚼肌，下颌骨，牙齿，颞下颌关节盘，牙周系统。这种修改的有限元法，其扩展使用极端的几何形状将能够模拟的动力学方面的咀嚼和磨牙症的牙齿。最后，模拟应导致基于CAD/CAM的重建和无干扰咬合的产生，从而优化这些咬合的咬合方面，并因此减少技术并发症，例如陶瓷修复体的碎裂和分层。使用这些FEM的另一个目的是模拟咀嚼/磨牙期间牙种植体和这种种植体支撑的上部结构的负载。由于牙科种植体与骨刚性连接，咬合力不能像天然牙齿那样得到阻尼;这导致上部结构和周围骨上的应力更大。根据这些优化的有限元模拟结果，可以在基于CAD/CAM的上部结构制造过程中考虑这些方面。

Correct occlusion is an essential aspect of the fabrication of dental restorations. Because dental technicians produce prosthetic restorations outside the oral cavity, accurate transfer of movement of the mandible to dental laboratory conditions is mandatory. Dental restorations without interferences and with sufficient chewing ability can then be produced. In recent years prosthetic reconstructions have been increasingly produced by CAD/CAM. This enables special attention to be devoted to the individual functional condition of the patient. This enormous advantage can, however, be exploited only when both kinematic (= motion and deformation) and kinetic (= forces and stresses) data are recorded. Unfortunately, until now, kinematic data, exclusively, have been recorded and, therefore, used for construction of dental restorations. The motion of the teeth, the deformation of the mandible, the deformation of the periodontal gap and the articular disc, including all the tissues involved-during motion and during chewing could not previously be recorded. In addition, individual information about these dynamics during chewing and clenching and/or grinding (bruxism) of the teeth has not been available; such information might be essential, because extraordinarily high eccentric forces are developed during these activities, resulting in a high risk of failure of all ceramic or veneered dental restorations. In this context interference-free occlusion of the restoration, taking into account the aforementioned kinetic aspects, is mandatory. In this study this missing kinetic data would be acquired for 22 healthy subjects, by acquisition of biting/chewing forces, electric muscle activity, jaw movement, and MRI images. These data would enable improvement of an existing finite-element model (FEM) of the stomatognathic system, including the temporomandibular joints, all chewing muscles, the mandible, the teeth, the temporomandibular disc, and the periodontal system. This modification of the FEM, and its expansion for use with extreme geometry would enable simulation of the kinetic aspects of chewing and bruxism of the teeth. Finally, the simulations should result in the CAD/CAM-based reconstruction and production of interference-free occlusion, enabling optimization of occlusal aspects of these restorations, and, consequently, reduced technical complications, for example chipping and delamination of the ceramic restoration. Another objective of the use of these FEM is simulation of the loading of dental implants and such implant-supported suprastructures during chewing/bruxism. Because dental implants are connected rigidly to the bone, occlusal forces cannot be damped as they are for natural teeth; this results in greater stress on the suprastructures and the surrounding bone. On the basis of the results expected from such optimized FE simulations, these aspects can be taken into consideration during CAD/CAM-based manufacture of the suprastructures.