The Chemistry of Inorganic Biomaterials | 2021
Chapter 1. Metallic Implants for Biomedical Applications
Abstract
Pure metals and their alloys are used in a broad range of medical devices, from electrodes used for tissue stimulation to stainless steel plates for bone fixation, and titanium- and cobalt-based alloys for dental implants and joint replacements. This is because they can bear large mechanical loads and resist fracture due to a favourable combination of tensile strength, and fracture toughness and strength. Through alloying and processing, metallic implants can be made to resist corrosion when they are used to permanently replace tissue, or degrade in a controlled manner for applications where tissue regeneration is expected. Their performance, however, can be significantly undermined by wear or corrosion-promoting events, such as loss of protective surface oxides and creation of microenvironments that hinder repassivation. Metallic and oxide wear debris and soluble metals released into the peri-implant space as a result of these processes can trigger a broad range of undesirable biochemical responses, from persistent local inflammation and bone loss, to systemic toxicity, to accelerated implant corrosion and mechanical failure. Prevention and even prediction of in vivo failure is challenging due to the complex and interconnected nature of chemical, physical and biological processes that take place within the peri-implant space. Further complications are added by their dependence not only on the materials properties but also the tissue/function that the material is applied in; the skill of the surgeon; the presence of microbial cells and their fragments; electrical stimulation and adjuvant therapies; and health status, life style and unique genetic makeup of the patient.