Biomaterials

Biomaterials: key points

Biomaterials are materials that perform their function in contact with the body, inside it or on its surface. Biocompatibility is not a property decided by the material alone; it is judged by whether the material can work with an appropriate host response for its application. Ceramics are divided into bioinert materials such as alumina and zirconia, which hardly react in the body; hydroxyapatite and bioactive glass, which bond to bone; and β-TCP and others, which are resorbed and replaced by bone.

Implants that support bone use titanium and Ti-6Al-4V, which have excellent corrosion resistance and come into direct contact with bone, as well as Co-Cr alloys. When a metal far stiffer than bone carries the load, the stimulus to the bone falls and the bone thins, which is stress shielding, so β titanium alloys with a lower Young's modulus and porous metals have been developed. For parts that should disappear once their job is done, biodegradable polymers such as polylactic acid, which break down by hydrolysis, and magnesium alloys, which corrode in body fluids, are used.