Galvanic Corrosion Between Ti/Ti6Al4V and Various Dental Alloys

The corrosion tendencies of metals are related with their position in the electromotive series. These electrode potential degrees may change due to the composition of the alloys, the surrounding medium or due to the alterations in the composition because of the recurrent costing. The galvanic corrosion appears when different electrochemical potentials are bound to one another and the electrical conductibility is assured by the presence of an electrolyte. It is difficult to avoid coupling of different metals, a problem concerning the choice of the alloy used for the implant bone supra-structure. One has studied the galvanism of several couples formed between a dental implant and diverse dental alloys in Afnor saliva. The electrochemical behavior of 8 commercial dental alloy superstructures with titanium and titanium alloy (Ti6Al4V) implants was investigated by electrochemical techniques. Non-precious alloys were Ni-Cr based (Wiron NT and Verasoft), Co-Cr based (Vitallium alloy) and Cu based (Gaudent). Semi-precious alloys were Ag-Pd based (RX91 and Unique White). The precious alloys were Au-Pd based (Ceram) and Au-Ag based (Argenco). Some of the corroded and non-corroded surfaces were observed by optical microscopy. From linear polarization curves the corrosion potential and the current densities were evaluated. The results showed very low corrosion rates, ranking from 10-6 to 10-9 A/cm2. All the results obtained indicate the fact that the corrosion process intensity corresponding to the coupling between titanium (respectively Ti6Al4V) and semi-precious alloys is reduced. The surface of precious and semi-precious alloys is not attacked, but the titanium (Ti6Al4V) surface is oxidized in time