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 (PO2) from 10 to 10 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 PO2 of 10 Pa > PO2 of 10 Pa > PO2 of 10 Pa > PO2 of 10 Pa >> PO2 of 10 Pa. These results suggest that TiO2 containing an optimal level of nitrogen strongly induces apatite formation but samples coated only with titanium nitride do not. Thus, controlling the formation of TiO2 and/or titanium nitride is expected to improve the bioactivity and wear resistance of biomedical titanium metal.