  Micromovements that occur in the joint between dental prostheses and implants
can lead to wear-induced degradation. This process can be enhanced by corrosion
in the oral environment influenced by the presence of solutions containing
fluoride. Moreover, the eventual galvanic interactions between NiCr and Ti
alloys can accelerate the wear-corrosion process. In this work, the
tribocorrosion process of Ti6Al4V and NiCr alloys used in dental implant
rehabilitations immersed in fluoride solutions at different pH values was
investigated. The galvanic interaction effect between the alloys was also
assessed. Tribocorrosion tests in corrosive media were performed with isolated
Ti6Al4V and NiCr alloys, followed by testing with both alloys in contact. The
media selected were based on fluoride concentrations and pH values that are
possible to be found in oral environments. Analysis of the surfaces after the
tribocorrosion tests was carried out using confocal laser microscopy. The wear
profile and volume losses were determined by confocal measurements. It was
concluded that the galvanic interaction between the alloys increased the
tribocorrosion resistance of Ti6Al4V, compared with that of the isolated
Ti6Al4V alloy. Ti6Al4V coupled with NiCr reduced the electrochemical potential
decay during sliding. The increased resistance was explained by the
electrochemical shift of the Ti6Al4V potential from active dissolution to the
passive domain.
