Corrosion of titanium implants and connected prosthetic alloys using lactic acid immersion test

Background/purpose: Combination of dental titanium implants with other prosthetic metallic components may lead to metal ion release that increases the risk of adverse reactions in patients. The present study therefore aimed to determine in vitro metal ion dissolution from different alloy combinations. Materials and methods: Dental alloys were subjected to a lactic acid immersion test together with titanium implants and matched with controls. Between day 1 and 38, open direct current potentials (DCP) between the samples and the electrolyte were recorded and metal dissociation inside the electrolyte was assessed using ICP-MS. Results: Absolute DCPs of the different alloys increased significantly (p<0.001) from 100-150mV to 490-580 mV within the first two weeks of immersion, dropping to about 450mV later on largely independent of the material. Titanium showed highest dissociation rates (2.00-12.06µg/cm2 per day; p=0.0002); all other components demonstrated poor corrosive dissolution (<0.6µg/cm2 per day). After immersion of 38 days, titanium still yielded high dissociation (0.64-1.38µg/cm2 per day) for all test groups. Presence of fine gold inside the electrolyte significantly increased dissociation of titanium (p=0.027). Dissociation of iron indicated contamination from tool components used for implant production. Optical examination of non-precious metal surfaces showed no corrosive discoloration after 5 or 26 weeks of lactic acid immersion. Conclusion: Within the limitations of this study, there is no objection against the use of non-precious alloys for the fabrication of components and prostheses supported on titanium implants if gold is not present inside the same electrolyte.