Influence of fluoride content and pH on the corrosion resistance of titanium and its alloys

In the last decade, new titanium alloys have been developed in different areas of dentistry, such as TiAl6V4 and NiTi. Concurrently, treatments using fluoride supplementation, such as odontology fluoride containing gels, have also been widely used in odontology. The aim of this study was to compare the NiTi, NiTiCo and TiAl6V4 alloys with the titanium, regarding the corrosion resistance in Fusayama Meyer artificial saliva with different pH and fluoride contents. In the experimental methods, the corrosion potential was measured over time, then a linear sweep voltametric analysis measured the polarization resistances and corrosion currents. Our results have shown that TiAl6V4 alloys have a good corrosion resistance as good as that of titanium in Fusayama Meyer saliva and acid salivary solution, except NiTi and NiTiCo alloys. Conversely, we noticed, as for the titanium, a remarkable localized corrosion phenomenon of those new alloys in fluoride and acid–fluoride salivary solutions. The fluoride ions could cause the breakdown of the protective passivation layer that normally exists on the titanium and its alloys, leading to pit corrosion.