Abstract
Orthodontic stainlessβsteel appliances are considered to be corrosion resistant, but localized corrosion can occur in the oral cavity. This study was undertaken to evaluate the properties of super stainless steels in orthodontic applications. Accordingly, the metallurgical properties, mechanical properties, corrosion resistance, amount of the released nickel, cytotoxicity, and characteristics of the passive film were investigated. Corrosion resistances of the specimens were high and in the following order: super austenitic stainless steel (SRβ50A) > super ferritic stainless steel (SFSS) = super duplex stainless steel (SRβ6DX) > 316L SS > super martensitic stainless steel (SRβ3Mo) in artificial saliva, 37 Β°C. At 500 mV (SCE), current densities of SRβ50A, SFSS, SRβ6DX, 316L SS, and SRβ3Mo were 5.96 ΞΌA/cm^2^, 20.3 ΞΌA/cm^2^, 31.9 ΞΌA/cm^2^, 805 ΞΌA/cm^2^, and 5.36 mA/cm^2^, respectively. Open circuit potentials of SRβ50A, 316L SS, SRβ6DX, SRβ3Mo, and SFSS were β 0.2, β 0.22, β 0.24, β 0.43, and β 0.46 V (SCE), respectively. SRβ50A, SFSS, and SRβ6DX released below 3 ng/ml nickel for 8 weeks, and increased a little with immersion time, and 316L SS released about 3.5 ng/ml nickel, but SRβ3Mo released a large amount of nickel, which increased with immersion time. The study demonstrated that SRβ50A, SRβ6DX, and SFSS have high corrosion resistance and mild or no cytotoxicity, due to the passive film enhanced by synergistic effect of Mo + N or by high addition effect of Cr + W. All super stainless steels showed very low cytotoxicity regardless of their nickel contents, although SRβ3Mo was found to be relatively cytotoxic. From these studies, these steels are considered suitable for orthodontic applications. Β© 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 69B: 183β194, 2004