Biomechanics

Biomechanics

Temporomandibular Joint

In synovial joints such as the temporomandibular joint (TMJ), mechanical stress and its resulting deformation of lining tissues are important factors in the generation of fluid transport and nutrition for the articular tissues. If stresses are too high, or too frequent, fatigue damage to the tissues is likely. The final clinical manifestation of this process is osteoarthritis of the joint. Therefore, for the long-term health of the tissues lining the synovial joints, it is important that there should be mechanisms controlling the magnitudes of stresses in the articular tissues. The work that is progressing in this area uses various techniques to explore the mechanisms controlling stresses in the TMJ. Such techniques include computer generated numerical modelling of muscle and joint forces and in vivo testing, in human subjects, of computer modelling predictions. Moreover, given the utility of computer modelling to predict in vivo conditions, in vitro simulation of these conditions has been used to test the effects of static and dynamic loads on the TMJ disc and how these factors influence the ability of the disc to control intracapsular stresses.

Tooth Wear

Occlusal and incisal wear can account for significant losses of tooth structure from the human dentition. Currently very little is known about the etiology and mechanisms that govern wear. The extent of tooth wear is currently evaluated by means of qualitative or ordinal scales that are insensitive to small changes in loss of tooth structure. The rate of wear cannot be ascertained using these methods. These problems are being addressed by the development of a quantitative measuring method that uses a computer-aided-design (CAD) software program to record and model the incisal and occlusal wear facets of the human dentition. When fully developed, this system will allow the location, size and distribution of wear facets to be recorded, as well as determining the rate of wear. The effect of dental treatment and disorders like bruxism and bulimia on the loss of tooth structure are some of the areas that could apply this technique.

Cavity Preparation Design

The life span of dental restorations has been difficult to predict. Current life-span predictions are based on clinical evaluation that in general does not account for the amount of tooth structure removed during the operative process. The effect that preparation dimensions have on the survivability of the restoration is only qualitatively known. Present research efforts are aimed toward determining the volumetric changes that occur when tooth structure is removed during various tooth preparation procedures. Future research will focus on determining the fatigue resistance of prepared teeth with various cavity preparation sizes. This will ultimately permit the development of a failure prediction model for teeth that are candidates for given cavity/crown preparation procedures. Restoration life-span information could allow the dentist and patient to make more accurate treatment planning decisions.

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