Biotribocorrosion of Titanium Dental Implants Local and systemic tissue effects

Abstract

Humans are exposed to different types of particles that can enter the body mainly by inhalation, ingestion, or dermal absorption. In view of the widespread use of biomaterials in medicine, another potential source of body contamination with microparticles (MPs, >100 nm) and/or nanoparticles (NPs, 1?100 nm) is the surface of metallic biomedical devices. Titanium is widely used in the manufacture of dental and orthopedic implants due to its excellent biocompatibility. It is a highly reactive metal, and on exposure to air or fluids it rapidly develops a layer of titanium dioxide (TiO2), which passivates the metal. However, as a result of electrochemical corrosion processes, frictional wear, or a synergistic combination of both, ions/particles may be released from metal implants into the bioenvironment. The combined effect of mechanical, biochemical, and electrochemical factors is known as tribocorrosion. When this process occurs in a biologic environment, it is referred to as biotribocorrosion. As a consequence of this phenomenon, the surface of a biomedical implant can be a potential source of release not only of MPs but also of NPs into the biologic milieu. Because NPs have a greater surface- to-volume ratio, they are biologically more reactive and potentially more harmful to human health. The chemically active metal ions/particles released from an implant surface may bind to the surrounding tissues but may also bind to proteins and be disseminated to distant organs in the vascular and lymphatic systems. Research in human samples conducted by our group has shown the presence of titanium particles in peri-implant tissue around failed human dental implants, in oral mucosa in contact with implant cover screws, in cells exfoliated from peri-implant oral mucosa around titanium dental implants, in reactive lesions in the peri-implant mucosa, and in infrequent pathologies in peri-implant tissues associated with titanium dental implants. In addition, our studies in experimental animal models demonstrated deposition of titanium MPs and NPs in target organs and the presence of a tissue response to these particle deposits. This presentation will address the local and systemic effects of biotribocorrosion of titanium, as shown by our studies in experimental animal and human tissues.