Dental Implant (CpTi) Performance: Electrochemical and Tribocorrosive Investigation
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Dental implants made of titanium alloys have been used as a predictable therapy approach to replace missing teeth. The oral environment subjects titanium implants to varying conditions like changes in pH, temperature, and saliva contamination leading to chemical corrosion together with mastication process. Objective: In this study, the combined effect of chemical corrosion and wear (so called tribocorrosion) in the degradation of dental implant material (cpTi) under varying pH oral environment was investigated. Methods: Titanium (cpTi) discs were subjected to sliding tests in artificial saliva at varying pH: 3.0, 6.0 and 9.0. A custom made tribocorrosion apparatus was used to carry out the tests. The tribological system consisted of a ceramic ball of 28mm diameter articulating against the flat face (titanium). Results: EIS results indicated an increase in electrochemical double layer capacitance (Cdl) at pH 3.0 and 6.0 after sliding. Surprisingly, in the presence of tribological stresses the measured current evolution was highest and fluctuated the most at pH 6.0. In addition, the greatest weight loss was measured at pH 6.0. Conclusions: Despite reports of cpTi being electrochemically stable down to pH 2.0, this study suggests degradation peaks at near neutral pH pH values in the presence of motion. At pH 6.0 the passive film layer, typically protecting the surface of titanium may not be reformed cohesively, resulting in more tribocorrosion products at the surface, which are easily sheared off. These findings elevate concern with regards to dental implants because the average pH of the oral cavity is 6.3.