Bonelike apatite formation on anodically oxidized titanium metal in simulated body fluid

Porous titania layers which were mainly composed of rutile and anatase were formed on the surface of titanium metals by the anodic oxidation in H2SO4 and Na2SO4 solutions. Titanium metals subjected to the anodic oxidation in CH3COOH and H3PO4 solutions formed porous titania layers which were essentially amorphous and contained only a small amount of anatase. Titanium metals anodically oxidized in H2SO4 and Na2SO4 solutions formed bonelike apatite on their surfaces in simulated body fluid (SBF) within 1 and 3 days, respectively. It was found that the rutile precipitated on their surfaces had (101) plane parallel to the substrate. These results indicate that not only anatase but also (101) plane of rutile can show high apatite-forming ability in SBF. On the contrary, specimens anodically oxidized in CH3COOH and H3PO4 solutions did not form apatite even after the soaking in SBF for 7 days. This might be attributed to the formation of only a small amount of anatase on their surfaces.