In Vitro Intraoral Resurfacing Of Dental Ceramic Prostheses Using High-Speed Clinical Handpieces

Intraoral resurfacing of ceramic prostheses using dental handpieces/burs is the key in restorative dentistry because the durability of ceramic prostheses depends on the resurfacing processes and quality. This dissertation investigated the critical scientific issues during dental resurfacing of bioceramics using clinical high-speed dental handpieces and diamond burs. The following contributions and conclusions have been made:A novel 2-DOF in vitro dental cutting tester has been developed to simulate the clinical intraoral resurfacing operations. The performance of a high-speed dental handpiece was dynamically evaluated using the tester. The application limitations of the dental handpiece in rapid and micro-fine finishing of ceramic prostheses have been proposed. The results demonstrate that the process parameters, including depth of cut, feed rate, cutting direction and material properties were central factors in controlling the clinical performance of a dental handpiece.The surface integrity and the removal mechanism in dental resurfacing of ceramic prostheses were investigated based on indenting fracture theory and surface morphology analysis. Consequently, a mathematical expression of a threshold load of lateral cracking for dental resurfacing of dental ceramics was addressed, with which the removal mechanism could be predicted. The results show that the resurfaced surface quality was sensitive to the grit size of dental diamond burs, but insignificantly changing with the depth of cut and the feed rate of dental handpieces.The stress fields and the degrees of subsurface damage of ceramic prostheses in simulated dental resurfacing operations were investigated using finite element analysis (FEA). A finite element model was established to predict the stress fields and the depths of subsurface damage in ceramic prostheses as functions of the dental operational conditions. It shows the stresses were all centered at the grit exit point, and the depths of subsurface damage increased with both the depth of cut and the feed rate. The FEA predictions were in agreement with the experimental measurements.An approach of optimization of the complex dental resurfacing processes was presented based on the artificial neural network technology and sequential quadratic programming algorithm. It involved a multi-objective function considering both the material removal rate and the subsurface damage degrees to optimize the dental processes. An illustrative example demonstrates that the approach was fast and efficient for optimization of the dental process parameters.The above research outcomes have provided the fundamental data and scientific base to restorative dentistry on proper intraoral dental resurfacing of ceramic prostheses.