Surface oxynitriding dependence on apatite formation on biomedical titanium metal in a simulated body fluid

Biomedical titanium metals subjected to gas under precisely regulated oxygen partial pressures (P O2 ) from 10 −18 to 10 5 Pa at 973 K for 1 hour were soaked in a simulated body fluid (SBF), whose ion concentrations were nearly equal to those of human blood plasma, at 36.5 °C for up to 7 days. After soaking in SBF, the following relationship held: The growth rate of apatite decreased in the order P O2 of 10 −14 Pa > P O2 of 10 4 Pa ≥ P O2 of 10 Pa > P O2 of 10 5 Pa >> P O2 of 10 −18 Pa. These results suggest that TiO 2 containing an optimal level of nitrogen strongly induces apatite formation but samples coated only with titanium nitride do not. Thus, controlling the formation of TiO 2 and/or titanium nitride is expected to improve the bioactivity and wear resistance of biomedical titanium metal.