Apatite formation on chemically treated titanium

Bioactive behaviour of inorganic materials, which is characterized by hydro xyapatite formation (HA), was first described on glasses (so-called bioacti ve) from the Na2O-CaO-P2O5-SiO2 system. The leaching of Na+ and Ca2+ ions f rom the glass surface and subsequent silaca gel layer formation were descri bed as the main conditions for HA formation. On titanium the gel layer is f ormed after a treatment in alkaline solutions. In this work the influence of Na+ content in the surface layer after differ ent multiple washing on RA formation was observed. No difference among samp les was found even if the Na+ content was considerable different. From the loss of phosphorus and calcium in solution it could be gathered that HA sur face layer was formed on each sample after 5 days of exposure in SBF. Using X-ray, HA was confirmed after 10 days of exposure in SBF. When the alkali treated titanium wets subsequently thermally treated, the l osses of phosphorus and calcium were observed as lately as 10 days of expos ure in SBF. This negative effect of the heat treatment on apatite formation could be explained by the dehydration (the decrease of the hydroxyl groups content in surface layer was analysed by DRIFT) and by the crystallization of the initial amorphous layer. The results show that the presence of the gel layer rich in hydroxyl groups is the main condition for the apatite formation on chemically treated tita nium. On contrary, the HA formation is inhibited due to the dehydration and the crystallization of the amorphous surface layer with the initial Na+ co ntent.