Enhancement of apatite-forming ability of parallely aligned Ti-substrates with optimum gaps by autoclaving

Pure titanium pieces were air-oxidized and autoclaved at 121°C for 20min before aligning various pairs of specimens in the GRAPEμ set-up, i.e., two pieces of rectangular substrates were aligned parallel to each other with optimum gap width (spatial design). Then, they were soaked in Kokubo's simulated body fluid (SBF) for 7 days to clarify how the autoclaving is to affect the in vitro apatite-forming ability on the substrates under the specific spatial design. Autoclaved specimens deposited a larger number of apatite particles, and showed stronger apatite X-ray diffraction than the specimen only heated in air. X-ray photoelectron spectroscopy (XPS) analysis indicated that the amount of chemically adsorbed OH and TiOH groups on the thermally oxidized titanium specimens increased by autoclaving. These results lead to the conclusion that the increase of TiOH groups and OH(s) and H₂O groups on the surface enhanced the in vitro apatite-forming ability on spatial design.