Corrosion of dental implants made of Ti-6Al-4V connected to 316L SS in agressive environment

Abstract

Implants made of dissimilar alloys, such as Ti-6Al-4V, connected to abutment of stainless steel (SS), are being considered for application as dental implants leading to galvanic corrosion. Body fluids are corrosive electrolytes that contain aggressive ions, such as chlorides, leading to localized attack at weak points of the passive film on materials used for implants fabrication. Another reason of apprehension concerning corrosion is the method of joining the different materials. This might lead to small gaps between the two materials and promote crevice conditions that stimulate localized corrosion. In this study, the corrosion resistance of a Morse taper dental implants made of Ti-6Al-4V alloy in contact to a prosthetic abutment of 316L, with the two parts joined by mechanical forces consisting of strikes, using different numbers of strikes (3, 5 and 7), was studied. The study was carried out by SVET technique in phosphate buffer solution (PBS) with an addition of H2O2 and pH adjust to 3 to simulate inflammatory conditions. The results showed high electrochemical activity at the interface between the two alloys. SVET maps showed that the Ti alloy acted as anode whereas the 316L SS as cathode. At the interface of the dissimilar alloys, large amounts of corrosion products accumulated showing the effect of the galvanic corrosion. This was mainly observed for the samples with 3 strikes for joining both alloys. The electrochemical activity was the lowest for the dental implant mounted with 5 strikes. SVET maps and SEM images showed a strong effect of crevice corrosion for the implants joined by lowest number of strikes among the testes.