The purpose of this study is to investigate mechanical properties of a superelastic Ni-Ti alloy for cast clasps. Bending properties of other alloys (Co-Cr, Au-Pt, Au-Ag-Pd) have been examined by the use of a universal testing machine to be compared with that of the Ni-Ti alloy which was examined in part 1. In this paper, repeated bending forces were applied on the tip of specimens supposed clasp arms by the use of a fatigue testing machine, then permanent deflections were measured by the use of a surface-shape recorder. It can be concluded that:(1) The force required to produce the deflection in 0.1mm (P0.1: bending rigidity) of the Ni-Ti alloy was smaller than other alloys.(2) After repeated deflections (30, 000 times) of 0.25-1.00mm, specimens of the Ni-Ti alloy produced less permanent deflections than other alloys. In clinical cases, it is supposed that large amount of undercut is available by the use of a superelastic Ni-Ti alloy for cast clasps.
