Localized corrosion resistance and cytotoxicity evaluation of ferritic stainless steels for use in Implantable dental devices with magnetic connections

Abstract

The ferromagnetic property of ferritic stainless steels makes them potential materials for use as implantable dental devices with magnetic connections. In this work, the corrosion resistance and cytotoxicity of the AISI 444 ferritic stainless steel (SS) was evaluated in a phosphate buffer solution (PBS) and compared with two materials used for fabrication of implantable materials, specifically, NeoM (a ferritic type of SS) and ISO 5832-1 (an austenitic type of SS). All tested materials showed passivity in the PBS electrolyte used. Susceptibility to pitting corrosion in the test solution used however was only associated to the NeoM steel, that has been used in commercial dental implant devices. A large concentration of precipitates/inclusions of complex nature was found in the microstructure of this steel and it is the probable reason for its low resistance to localized corrosion, much lower than that of the AISI 444 SS used in this study. The AISI 444 stainless steel tested is a Nb and Ti stabilized steel and it presented mainly Nb and Ti rich types precipitates in its microstructure. No pits were seen at the surface of this last steel after polarization tests. The pitting resistance of the AISI 444 steel was compared to that of the ISO 5832-1 austenitic and it was found similar to this last steel that is well known for its good corrosion resistance performance. The results suggested that the AISI 444 steel is a potential candidate for replacement of the commercial ferromagnetic alloys currently used in dental prosthesis.