All-ceramic restorative materials are currently not recommended for posterior crowns and multiple unit restorations due to their tendency to fracture in use. Clinical studies of posterior all-ceramic crowns are needed to identify the causes of failure. For meaningful clinical studies to be performed, it is necessary to identify ceramic crown/luting cement combinations that will provide optimal resistance to fracture of all-ceramic crowns. Fracture of aluminous porcelain crowns has been attributed to the propagation of cracks which originate from surface irregularities. Moffa (1988) has suggested that the transverse strength of all-ceramic crown systems may be adequate to withstand occlusal loading. The success of all-ceramic crowns will therefore be improved if processing techniques could be devised to reduce or eliminate flaws on the fitting surface; or stronger, less brittle luting cements can be developed which will bond to the internal surface of ceramic crowns. This preliminary study seeks to investigate variables that affect the ceramic/cement crown interactions and identify luting cements that will improve the resistance of all-ceramic crowns to fracture under occlusal loading. Results obtained from this study will ultimately form the basis for a future study of the clinical performance of all-ceramic crowns/luting cement combinations. The project will initiate collaborative research and demonstrate research competence for the principal investigator, a first time applicant. All-ceramic crowns will be cemented onto standard polycarbonate dies with various luting cements and then loaded to failure in compression in a mechanical testing machine to determine the effect of luting cements on the fracture strength. The fitting surface of crowns will be given various treatments, etching and silane treatment and glazing followed by silane treatment. The crowns will be cemented with a resin cement and the fracture strength determined. An examination of fractured ceramic/cement couples will provide pilot data fracture strength of dental ceramic crowns.
