Hydroxyapatite coatings on titanium

Some ceramics, including calcium phosphates and certain glasses and glass-ceramics, form an important class of bioactive materials that are used extensively in repair and reconstruction of diseased or damaged parts of the musculoskeletal system. The similarity between synthetic hydroxyapatite (HA) (Ca10(PO4)6(OH)2) and the mineral phase of bone and tooth made HA one of the earliest materials to be used to impart osteoconductive (bone-bonding) properties to the surface of biocompatible, metallic implants. HA and other calcium phosphate surfaces are used primarily to cause early stabilization of the implant in the surrounding bone through the formation of a direct bond and enhanced bone apposition. Although bioactive ceramics are used in several compositions and forms, the focus here is on the use of HA coatings in metallic implants. The coatings made by commercially available plasma-spray and other techniques are compared to those made recently by surface-mediated biomimetic routes.