Significance of water promoting amorphous to crystalline conversion of apatite in plasma sprayed coatings

摘要

The plasma spraying technique has been used successfully to coat the surface of titanium and its alloy implants with hydroxyapatite (HA) [1, 2]. This coating-implant system has the capacity of biologic-ally bonding firmly to bone, promoting the forma-tion of new bone at the surface and protecting the surrounding bone against metal-ion leaching from a metal prothesis. However, the plasma spraying procedure unavoidably induces changes in starting HA powders, so as to make the characteristics of HA coatings different from those of bulk HA ceramics, including the appearance of a certain amount of amorphous apatite with decrease of the crystallinity [3, 4] and the decomposition of the HA structure into tricalcium phosphate (TCP), tetra-calcium phosphate monoxide (TCPM) and oxy-hydroxyapatite (OHA) [3,5,6].