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

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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.