Contrary Effects of UV-Irradiation on In Vitro Apatite-Forming Ability of TiO2 Layer in Simulated Body Fluid

Apatite-forming ability is a prerequisite to ensure the direct bonding of biomedical materials to living bone. Recently, Shozui et al. reported that UV- irradiation enhanced the in vitro apatite-forming ability of the TiO2 layer (rutile) prepared by heat-treatment of titanium substrates in air. This study examined TiO2 (anatase)-covered Ti samples, derived by chemical and subsequent thermal treatment (CHT), in terms of their in vitro apatite-forming ability after UV-irradiation under varied conditions. UV-irradiation of CHT in air reduced the amount of active sites for apatite nucleation, while the UV-irradiation in water increased them. These contrary responses indicate that environmental factors of the UV- irradiation are important for controlling the in vitro apatite- forming ability of the anatase layer.