Mechanism of apatite formation on anodically oxidized titanium metal in simulated body fluid

Mechanism of apatite formation on anodically oxidized titanium metal in a simulated body fluid was investigated by XPS and TEM observation. The anodically oxidized metal was found to have rutile and anatase titania with a large number of Ti-OH groups on its surface. On immersion in SBF, the metal formed a bonelike apatite on its surface through formations of an amorphous calcium titanate and an amorphous calcium phosphate. The formation of the calcium titanate was induced by the Ti-OH groups, which reveals negative charge to interact selectively with positively charged calcium ions in the fluid. The calcium titanate is postulated to reveal positive charge, thereby interacting with the negatively charged phosphate ions in the fluid to form the calcium phosphate, which eventually crystallized into bonelike apatite.