Influence of film thickness on in vitro bioactivity of thin anatase films produced through direct deposition from an aqueous titanium tetrafluoride solution

With proper pre-treatment of the metal, well-crystallized thin anatase films of thicknesses varying from 0.12 to 0.79 μm were deposited on commercially available pure titanium (CPTi) substrate from a 25 mM titanium tetrafluoride aqueous solution. The deposition of anatase films took place at a low temperature of 60 °C between 1 to 48 h. After a heat treatment in air at 300 °C for 1 h to remove fluorine from the anatase films, the films of thicknesses above 0.41 μm induced apatite deposition in a simulated body fluid (SBF) within 5 days. The 0.12 μm thick anatase film required 21 days to induce apatite formation in SBF. There appeared to be a critical film thickness of anatase, above which the in vitro bioactivity improved greatly. But further increases in the film thickness of anatase did not have remarkable effect on in vitro bioactivity.