Abstract
Usually the mechanical properties of dental alloys are determined from the values obtained through static tests of their tensile strength, hardness, etc. Generally, high tensile strength and ductility are preferred. However, when small stresses with in proportional limits are applied repeatedly (even though not amounting to destructive forces in static tests), they may cause rupture in the alloy or, at least, cause it to lose its original mechanical properties. This phenomenon is called metal fatigue. It is estimated that the intraoral stress loads received by dental restorations during mastication or during insertion and removal of appliances are repeated more than 3×105 time/year. From this standpoint, it may be more appropriate to estimate the fracture strength of such dental alloys based on the fatigue properties of the restorative materials used for clasps, bars, and fixed bridges. For this reason, it is necessary to obtain data through fatigue tests on the fatigue strength and the fatigue endurance limits of dental alloys, and it is important to find a correlation between these data and the static data on tensile strengths and ductility obtained by tensile tests.
