Abstract
NiTi alloy has been given much attention in recent years.It possesses unique properties, such as“shape memory effect”and“outstanding elasticity”.Recently, the new NiTi alloy wire which possesses superelastic property was developed.The author has reported its tensile and three points bending properties before.In this study, bend and successive 90degrees bends tests were performed in accordance with The ADA Specification No.32 for Orthodontic Wires to evaluate the properties of the new superelastic NiTi alloy wire and compare them to those of stainless steel, Co-Cr alloy and work hardened NiTi alloy wire.In bend test, the new superelastic NiTi alloy wire produced low and almost constant bending moment between 50 and 80degrees of deflection angle as the wire returned to a rest position.The angle of permanent bend of it was zero even after 90degrees bend.In successive 90degrees bends test, the new superelastic NiTi alloy wire stood over 2000times, which were remarkably higher than those of stainless steel and Co-Cr alloy wire, and 4times over than that of work hardened NiTi alloy wire.These properties of the new superelastic NiTi alloy wire seem to be very useful for orthodontics.Fractured surfaces of the NiTi alloy wires by SEM after successive bends test showed dimple rupture pattern which were much different from those of stainless steel and Co-Cr alloy wires.
