Bending Property of Super-Elastic Ti-Ni Alloy Dental Castings with Different Heat Treatments

Abstract

Bending property of Ti-Ni alloy dental castings was evaluated in comparison with that of Co-Cr alloy in a cantilever test. Heat treatment effect on the bending property was also investigated in relation to phase transformation. Ti-50.85Ni (mol%) alloy was used, and the shape of bending test specimens was half-rounded in cross section, 2.0 mm in diameter. The bending test was carried out at 310 K. Distance between the loading point and the grip edge was 5.0 or 10.0 mm. Maximum bending deflection was 0.50 mm. Thermal behavior accompanying phase transformation of Ti-Ni alloy was examined by differential scanning calorimetry. Load-deflection diagrams of Ti-Ni alloy castings in the bending test showed elastic and super-elastic deformation, while those of Co-Cr castings showed elastic and permanent deformation. Maximum bending load and residual deflection of the Ti-Ni castings were lower than those of the Co-Cr castings and were decreased by heat treatment under a high-stress condition at the 5-mm loading point. Transformation temperature was increased by heat treatment, which was thought to influence the change in bending property. Super-elasticity of the Ti-Ni alloy castings in bending was shown to be improved by heat treatment, offering the potential to improve the design and clinical performance of cast dental prostheses.