Titanium was introduced in surgeries in the 1950s after being used in dentistry for a decade before. It is now the metal of choice for prosthetics, internal fixation, internal body devices and instrumentation. Titanium is used from head to toe in biomedical implants. Titanium can be found in neurosurgery, bone conduction hearing aids, false eye implants, spinal fusion cages, pacemakers, toe implants and shoulder / elbow / hip / knee replacements, and much more.. The main reason why titanium is often used in the body is due to the biocompatibility of titanium and, with surface modifications, to the bioactive surface. Surface characteristics that affect biocompatibility are surface texture, steric hindrance, binding sites and hydrophobicity (wetting). These features are optimized to create an ideal cellular response. Some medical implants, as well as parts of surgical instruments are coated with titanium nitride (TiN).
Titanium is considered to be the most biocompatible metal due to its resistance to corrosion of body fluids, bio-inertia, osseointegration capacity and high fatigue limit. Titanium’s ability to withstand the harsh physical environment is the result of the protective oxide film that naturally forms in the presence of oxygen. The oxide film is strongly adherent, insoluble and chemically impermeable, preventing reactions between the metal and the surrounding environment.
It has been suggested that the ability of titanium for osseointegration results from the high dielectric constant of its surface oxide, which does not denature proteins (such as Ta and Co alloys). Its ability to physically bond with bone gives titanium an edge over other materials that require the use of an adhesive to stay attached. Titanium implants last longer and much higher forces are needed to break the bonds that bind them to the body in relation to their alternatives.
The surface properties of a biomaterial play an important role in determining the cellular response (cell adhesion and proliferation) to the material. The titanium microstructure and its high surface energy allow it to induce angiogenesis, which favors the osseointegration process.