Biomimetic deposition of calcium phosphate on thermally oxidized titanium and PTFE substrates

Biomimetic deposition of calcium phosphate (apatite) on Ti substrates air-oxidized at various temperatures was studied after they were soaked in a simulated body fluid (Kokubo solution, SBF), and the deposition behavior of the surface open to SBF (open surface and the surface facing to the bottom of the container that held SBF and the specimen (contact surface) was compared. The contact surface deposited apatite in 7 days whereas the open surface could not in 2 months. The greatest ability of depositing apatite was provided by oxidation at 400°C. Moreover, apatite deposited on PTFE or silicone plate facing to the 400°C-treated Ti substrate with the tapered spacing of 0 to 0.15 mm. The mechanism of the apatite deposition on the contact surfaces was discussed in relation to the passive dissolution of titanium in SBF. The release of titanium hydroxide and OH ions from the titanium surface was considered responsible for the apatite deposition.