Corrosion of titanium dental implants has been associated with implant failure and is considered one of the triggering factors for peri-implantitis. This corrosion is concerning, because a large amount of metal ions and debris are generated in this process, the accumulation of which may lead to adverse tissue reactions in vivo. The goal of this study is to investigate the mechanisms for implant degradation by evaluating the surface of five titanium dental implants retrieved due to peri-implantitis. The results demonstrated that all the implants were subjected to very acidic environments, which, in combination with normal implant loading, led to cases of severe implant discoloration, pitting attack, cracking and fretting-crevice corrosion. The results suggest that acidic environments induced by bacterial biofilms and/or inflammatory processes may trigger oxidation of the surface of titanium dental implants. The corrosive process can lead to permanent breakdown of the oxide film, which, besides releasing metal ions and debris in vivo, may also hinder re-integration of the implant surface with surrounding bone.

Implant surface oxidation occurred in bacteria-containing medium even at early stages of immersion (2 days). The incremental corrosion resulted in dissolution of metal ions and debris into the testing solution. Dissolution of metal ions and particles in the oral environment can trigger or contribute to the development of peri-implantitis at later stages.

The surface morphology and chemical composition of commercially pure titanium dental implants and healing abutments exposed in vitro or in vivo to oral bacteria were studied.

Presence of metal ions and debris resulting from corrosion processes of dental implants in vivo can elicit adverse tissue reactions, possibly leading to peri-implant bone loss and eventually implant failure. This study hypothesized that the synergistic effects of bacterial biofilm and micromotion can cause corrosion of dental implants and release of metal ions in vivo. The goal is to simulate the oral environment where an implant will be exposed to a combination of acidic electrochemical environment and mechanical forces. Four conditions were developed to understand the individual and synergistic effects of mechanical forces and bacterial biofilm on the surface of dental implants; In condition 1, it was found that torsional forces during surgical insertion did not generate wear particle debris or metal ions. In condition 2, fatigue tests were performed in a wet environment to evaluate the effect of cyclic occlusal forces. The mechanical forces applied on the implants were able to cause implant fracture as well as surface corrosion features such as discoloration, delamination, and fatigue cracks. Immersion testing (condition 3) showed that bacteria ( Streptococcus mutans ) were able to create an acidic condition that triggered surface damage such as discoloration, rusting, and pitting. A novel testing setup was developed to understand the conjoint effects of micromotion and bacterial biofilm (condition 4). Surface damage initiated by acidic condition due to bacteria (condition 3), can be accelerated in tandem with mechanical forces through fretting-crevice corrosion. Permanent damage to surface layers can affect osseointegration and deposition of metal ions in the surrounding tissues can trigger inflammation.