Effects of Thermal Oxidation on Biocompatibility of Ni-Ti Shape Memory Alloy

概要

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In order to improve the biocompatibility of a Ni-Ti alloy, mechanically polished Ni-Ti samples were subjected to isothermal oxidation (TO) in N2-20vol%O2 at temperatures of 573 and 773K. We conducted cell culture tests with L929 fibroblast cells to examine the cell proliferation. Amount of Ni ions elusion in culture medium used during cell proliferation test was analyzed by atomic absorption photometer. As a results, all TO-treated samples showed good biocompatibility after 3 days of immersion tests, and released Ni ions were significantly reduced by TO-treatment. These are because the TOtreatment generated thick and stable surface modified layer at the alloy surface. In addition, wear resistance of the Ni-Ti alloy was also improved by TO-treatment. After the wear tests, biocompatibility was evaluated by cell proliferation tests, and its results showed that the surface damage on the TO-treated sample did not affect the attachment cells. From these results we can conclude that the isothermal oxidation treatment is effective as a surface modification method for Ni-Ti alloy.