Novel assessment system for prosthodontic design with the fatigue fractography analysis.

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The objective of this research project was to investigate the fracture mechanics of dental alloys and polymers used in removable dental prostheses. Fracture surfaces of clinically retrieved dentures were analyzed by means of fractographic technique to correlate the location of failure in the denture structures with estimated stress distribution created in the materials used 'in the dentures. Stress distribution was calculated by the three dimensional finite element analysis for each retrieved denture structure. The stress analyses were also conducted with experimental fatigue tests for the alloys and the polymers used in the clinical dental prostheses. Results indicated that high stress area within the Ti-6A1-7Nb, Co-Cr, and gold alloy used in the denture structures coincided with their fatigue fracture locations. The probabilities of fatigue fracture and permanent deformation of the dental alloys were closely related to the material strengths and the deflections. To minimize the possibilities of fatigue failures, the denture structures should be designed with consideration of the maximum tensile stresses that are determined by the mechanical properties of the alloys and the polymers. Also, the estimation of critical occlusal loads was possible by calculating the critical stress that could induce fracture initiation in the alloys and the polymers. The results of the project strongly suggest that an innovative approach for optimizing the denture designs and evaluating new biomaterials is promising for future biomaterial design system.