# (Bio)Tribocorrosion in Dental Implants: Principles and Techniques of Investigation
## 1 Introduction
In particular, material debris is dangerous because it can trigger a biological response [11], resulting in metallosis, the deposition of metals in human organs and tissues; cytotoxicity-necrosis, in which cells can digest very small particles (not large enough to activate macrophage action) that corrode them and, in some cases, cause their death; hypersensitivity, which is closely related to the patient and which is the biological and immunological response of B and T lymphocytes to the presence of metals; pseudotumor, which is the formation of a huge mass of tissue, probably not aggressive, originating  
Figure 1: Schematic of tribocorrosion phenomena. from wear and tear that, although not a true cancer, can cause symptoms such as pain, paralysis, etc. ; osteolysis and osteopenia, respectively, the former being the complete destruction of bone, while the latter is the loss of bone mass associated with its density and not its protein aspect. According to [PERSON]'s law [12], bone mass varies continuously as a function of external loads and static and dynamic mechanical stresses. This means that bone needs incentives to maintain its form and density; genetic effects, that is, potential genetic damage to DNA and chromosomes in terms of alterations in structure and number. Chromium and cobalt appear to be potentially mutagenic metals; moreover, some studies have shown an increased tendency for cancer development in patients undergoing surgery with metal and polyethylene implants [13]. Other studies confirmed [14] that there is a correlation between tribocorrosion and biological problems in that the chemical-mechanical degradation results in the release of ions that attack human cells, impairing osseointegration. This process is amplified when the patient has diseases such as diabetes and surface modifications are applied to the implant to promote macrophage activity [15]. [PERSON] et al. [16] stated, however, that vitamin D deficiency has a greater tendency for failure as determined by incomplete osseointegration. According to the study by [PERSON] et al. [17], aging and potential osteoporosis are also risk factors for osseointegration. Therefore, tribocorrosion, implant failure and biological activity are all related, as the main factor leading to implant loosening is immunologically mediated rejection [18], and this is facilitated by the former. The long-term success of oral implants depends on maintaining healthy tissues around them. Accumulation of bacterial plaque induces inflammatory changes in the soft tissues surrounding oral implants and can lead to their progressive destruction (peri-implantitis) and, ultimately, to implant failure. According to [PERSON] et al. [19], implant success is assessed by considering aspects of implant stability, peri-implant bone loss after one year of use, the health of peri-implant hard and soft tissues and patient-related factors, including pain or infection due to peri-implantitis, a pathological condition that occurs in the tissues surrounding dental implants. This infectious condition affects about two out of 10 patients [20; 21]. With approximately 12 million implants placed worldwide each year by a growing number of physicians with varying skills, there is concern that peri-implantitis is a growing complication in dentistry [22]. Numerous treatment protocols for peri-implantitis have been proposed, including non-surgical, surgical and combined approaches. The stability and retention of the prostheses remains a major challenge for these complex defects. This review discussed the phenomena of biotriborrosion, conceptualized and defined the process, then illustrated the investigation techniques and analytical models. Finally, it focused on the case of dental implants, highlighting the most relevant recent investigations.