A new procedure of the tensile fatigue test for dental materials

A new tensile fatigue test using a stainless steel screw was introduced. A transparent PMMA rod was selected as the test material. A hole was drilled and tapped into the rod; a screw was put into the rod with dental cement or without cementation. Three types of cyclic loads were applied to the test piece; the number of times the load was applied when the initial crack was observed and when the final fracture occurred were recorded. Surface observation showed that actual fatigue fractures occurred in the test piece. The preferred applied load waveform was the cyclic haver-triangles load because of the small coefficient of variance. Fatigue strengths of test pieces with and without cementation were different. Cementation improved the fatigue properties, and the type of cement had an effect on the fatigue properties. Although the number of final fractures minus the number of initial cracks was the constant regardless of the type of cement used.