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修复体的一个重要方面。由于牙科技术人员在口腔外生产修复体，因此必须将下颌骨的移动准确地转移到牙科实验室条件下。然后，可以生产出不受干扰并具有足够咀嚼能力的牙齿修复件。近年来，越来越多的假体重建是由CAD/CAM产生的。这使得对患者的个体功能状况给予特别关注。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，才能利用这种巨大的优势。不幸的是，到目前为止，运动学数据只被记录下来，因此被用于牙科修复体的构建。在运动和咀嚼过程中，牙齿的运动、下颌的变形、牙周间隙和关节盘的变形，包括所有涉及的组织，以前都无法记录下来。此外，还没有关于牙齿咀嚼、咬合和/或磨牙(磨牙症)过程中这些动力学的个人信息；这些信息可能是必要的，因为在这些活动中会产生非常高的偏心力，导致所有陶瓷或贴面牙修复体失败的风险很高。在这方面，考虑到上述动力学方面的因素，修复的无干扰咬合是强制性的。在这项研究中，22名健康受试者将通过获取咬合力/咀嚼力、电肌肉活动、下颌运动和核磁共振图像来获取缺失的动力学数据。这些数据将有助于改进现有的口腔颌面系统的有限元模型，包括颞颌关节、所有咀嚼肌肉、下颌骨、牙齿、颞颌关节盘和牙周系统。这种对有限元的修改，以及它的扩展，用于极端几何，将能够模拟牙齿咀嚼和磨牙症的动力学方面。最后，模拟应该导致基于CAD/CAM的重建和产生无干扰的咬合，从而能够优化这些修复体的咬合方面，从而减少技术复杂性，例如陶瓷修复体的碎裂和分层。使用这些有限元方法的另一个目的是模拟咀嚼/磨牙症期间种植体和这种种植体支撑的上部结构的载荷。由于牙种植体牢固地连接到骨骼上，咬合力不能像天然牙齿那样受到抑制；这会导致上部结构和周围骨骼受到更大的压力。基于这种优化有限元模拟的预期结果，可以在基于CAD/CAM的上层建筑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.