Corrosion Resistance and Cytotoxicity of Super Stainless Steels for Skeletal Anchorage System

Nickel is one of the most common causes of allergic contact dermatitis and hypersensitivity. In case of stainless steel as a biomaterial, the higher the corrosion resistance and the lower the nickel content, the better it is for the human body. However, because nickel plays an essential role in the stabilization of the austenitic phase and in the corrosion resistance of stainless steel, it is difficult to exclude the nickel from the constituents of stainless steels. Therefore, the purpose of this study was to investigate corrosion resistance and cytotoxicity of super stainless steels, with respect to nickel content and to evaluate their potential for skeletal anchorage system. In terms of corrosion resistance, super stainless steels exhibited lower passive current density(2?4 ?A/cm2) than pure Ti(6.6 ?A/cm2) in the body-simulated solution and similar potentiodynamic polarization behaviors to each other. Pitting corrosion occurred in 316LSS, but not in the others. Open circuit potentials of annealed super stainless steels were higher than those of the cold rolled, and they were increased significantly soon after being immersed into the solution. In potentiostatic test, current densities of super stainless steels decreased abruptly soon after potential-loaded at 250 mV(SCE), which meaned these steels had high corrosion resistance in a human body. In addition, SR-50A, super stainless steel, exhibited no cytotoxicity, while the others exhibited slight cytotoxicity in agar overlay test and they all exhibited cell viability of more than 87% in MTT test. It means that super stainless steels are slightly cytotoxic to the fibroblast cell. They did not cause any significantly adverse effect on osteoblast cell proliferation. These indicated that the cytotoxicity of super stainless steels are free or slight due to their high corrosion resistance. The cytotoxicity had no relations with nickel contents, because even SR-50A with the highest nickel content exhibited no cytotoxicity. Because super duplex and ferritic stainless steels containing small amount of nickel showed high corrosion resistance, they can minimize the adverse effect of nickel when used in a human body.ope