Improvement of mechanical properties of dental materials by shot peening

Shot peening is one of the most effective techniques for surface modification. Fatigue strength of dental prosthesis is increased by the peening introducing compressive residual stress and work-hardening into sub-surface of metallic materials. In this study, in order to improve mechanical properties of dental materials, five kind of dental materials, i.e. Au-Cu-Pt-Ag, Ag-Pd-Cu-Au, Co-Cr, cp-Ti and Ti-6Al-7Nb, were treated by shot peening. Residual stress, Vickers hardness, the number of cycle to failure and the yield stress of shot peened materials were measured by the twodimensional detector in X-ray analysis, the Vickers hardness test, the fatigue test and the inverse problem analysis based on results of indentation test, respectively. It was concluded that the yield stress of dental material increases due to the shot peening and the relationship between the yield stress obtained by inverse problem analysis and the fatigue life had higher correlativity than that between the Vickers hardness and the fatigue life.