Development and properties of Ti-In binary alloys as dental biomaterials

The objective of this study is to investigate the effect of alloying element indium on the microstructure, mechanical properties, corrosion behavior and in vitro cytotoxicity of Ti-In binary alloys, with the addition of 1, 5, 10 and 15 at.% indium. The phase constitution was studied by optical microscopic observation and X-ray diffraction measurements. The mechanical properties were characterized by tension and microhardness tests. Potentiodynamic polarization measurements were employed to investigate the corrosion behavior in artificial saliva solutions with and without fluoride. In vitro cytotoxicity was conducted by using L929 and NIH 3T3 mouse fibroblast cell lines, with commercially pure Ti (CP-Ti, ASTM grade 2) as negative control. All of the binary Ti-In alloys investigated in this work were found to have higher strength and microhardness than CP-Ti. Electrochemical results showed that Ti-In alloys exhibited the same order of magnitude of passivation current densities with CP-Ti in artificial saliva solutions. With the presence of NaF, Ti-10In and Ti-15In showed transpassive behavior and lower current densities at high potentials. All experimental Ti-In alloys showed good cytocompatibility, at the same level as CP-Ti. The addition of indium to titanium was effective on increasing the strength and microhardness, without impairing its good corrosion resistance and cytocompatibility.