치과 급속 교정용 초내식성 스테인리스강 가공재의 특성

Abstract

When stainless steels are used in the human body, the nickel ion released from the alloys over a short or long term can cause such adverse effects as allergies, dermatitis, asthma. Although the higher the corrosion resistance of stainless steels and the lower the nickel content, the better it is for the human body, since nickel has an essential role in the stabilization of the austenitic phase and the corrosion resistance of stainless steels, it is difficult to remove nickel completely. In this regard, the purpose of this study was to investigate corrosion resistance, cytotoxicity and mechanical properties of super stainless steels, and upon this basis, to evaluate their potential for orthodontic applications. Super austenitic stainless steels had higher content of nickel(17~20 wt%) than super duplex stainless steels (7~10 wt%) or super ferritic stainless steels (lower than 3 wt%). Super austenitic and duplex stainless steels had nitrogen content of above 0.2 w%. These steels had high Mo or W contents of which synergistic effect together with N increases localized corrosion resistance. In terms of hardness, super stainless steels exhibited higher value than 316L S. S. and two times higher than cp Ti(grade II). Austenitic and duplex stainless steels exhibited better mechanical properties. Super stainless steels exhibited low passive current density (3~4 μA/㎠) and similar potentiodynamic polarization behaviors among themselves. Thus, these steels are considered to have high corrosion resistance in the human body-simulated solution. Pitting corrosion occurred in 316L S. S.. A3 containing the highest nickel content, as well as SAF2507 exhibited none cytotoxicity, and the others, slightly. This indicates that the cytotoxicity has no direct relation with nickel content itself in these alloys. Super stainless steels with both high corrosion resistance and good biocompatibility are expected to be used for orthodontic applications by virtue of the passive film attribute enhanced by synergistic effect of Mo+N or by high addition effect of Cr+W.