Thin hydroxyapatite layers formed on porous titanium using electrochemical and hydrothermal reaction

Abstract

In our previous study, it was found that hydroxyapatite (HA) microcrystals were precipitated by hydrothermal treatment on an anodic titanium oxide film containing calcium and phosphorus (AOFCP) with an equivalent Ca/P ratio to HA, which was formed on a titanium metal anode in an aqueous electrolytic solution of dissolved calcium acetate and β-glycerophosphate. In this study, the formation mechanism of the AOFCP has been clarified. Spark discharges, which occur on titanium surface with a large amount of heat generation, cause crystallization of the TiO₂ matrix of the AOFCP and incorporation of calcium and phosphorus into the matrix from these electrolytes simultaneously. The calcium and phosphorus in the matrix seem to exist as ions rather than as calcium phosphate. Also, thin HA layers consisting of the many precipitated microcrystals can be uniformly formed even on titanium with complex shapes or surface geometries such as the mesh, roughened surfaces and bead-coated porous coating by the present method.