Corrosion Features of Titanium Alloys in Dental Implants: A Systematic Review

Titanium and its alloys are the gold standard for dental implants because of their unique combination of chemical, physical, and biological properties, and in particular thanks to their biocompatibility, resistance to corrosion, and mechanical properties. However, despite advanced technologies to avoid corrosion of dental implants, the mechanisms toward the release of metals and their role in the onset of peri-implant diseases are still under-investigated. The combination of stress, corrosion, and bacteria contributes to implant failure. Recent studies suggest the existence of wear/corrosion products may correlate with peri-implantitis progress by triggering microbial dysbiosis, the release of pro-inflammatory cytokines, and animal bone resorption. The aim of the present article is to highlight the various features of corrosion of titanium alloys used in dental titanium implants, to review the evidence toward biocorrosion in the oral environment and to discuss the methodological and electrochemical aspects of surface treatments and titanium-based alloys. The present review was conducted according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. The research question was about the corrosion of titanium alloys used in dental implants and their consequent biological side effects on peri-implant tissue. After screening the duplicates and following the application of exclusion criteria, the full texts of 23 articles were included in the review. The development of improved strategies toward the reduction of corrosion and degradation of titanium alloys used for dental implants is crucial, also to prevent metal release in the tissue surrounding them to prolong their lifetime. As chemical and physical properties are crucial for the electrochemical behavior of the implant material, the development of appropriate alloys or coatings/layers for corrosion inhibition is mandatory.