Crystal growth of calcium phosphate on chemically treated titanium

Calcium phosphate (Ca–P) phases were grown on titanium which was treated with H 3PO 4 and diluted alkali solution by immersing in supersaturated calcification solutions (SCSs) at 37°C, i.e. fast calcification solution (FCS) and Hanks'-balanced salt solution (HBSS). A significant difference between the sizes of the Ca–P crystals precipitated from FCS and from HBSS was observed and ascribed to the fact that the ion concentrations of Ca 2+ and HPO 2− 4 in HBSS are much lower than those in FCS and some inhibitors of Ca–P growth such as Mg 2+ and CO 2− 3 ions are present in the former. Micron-scaled thin crystal plates composed of hydroxyapatite and octacalcium phosphate grew directly on the treated surfaces from FCS whereas nano-sized, bone-like apatite particles deposited from HBSS. It was found that the longer the H 3PO 4 etching was, the more easier Ca–P phases were deposited on the treated surface when the alkali ageing time was fixed. No Ca–P deposition was observed on any untreated or single-step treated metals after 2 weeks of immersion in either HBSS or FCS. The present study makes it possible to prepare Ca–P coatings on titanium implants by simple chemical method, which might enhance their activity of bone bonding.