Ion beam sensitizing of titanium surfaces to hydroxyapatite formation

CaO and P2O5-containing Ti surfaces were prepared and examined for their bioactivity. The preparation involved the incorporation of Ca and P into Ti by ion implantation to a total dose of up to 8×1017 ions/cm2 with a 1.7 Ca/P ratio and a subsequent oxidation at 500°C in O2 for 40 min. The model surfaces were examined for their reactivity toward hydroxyapatite formation by microscopically recording the mineralization in a simulated body fluid. The ion implantation-modified surfaces were shown to exhibit enhanced mineralization by inducing heterogeneous nucleation, growth, and proliferation of hydroxyapatite, relative to a control sample of pure Ti. The surface-induced reactivity was shown to relate to the enhanced provision of the ionic mineral components Ca2+ and HPO42− directly supplied from the surface and the substrate-mediated nucleation by the hydroxylated surface of TiO2.