Fabrication of bioactive titanium and its alloys by combination of doubled sandblasting process and alkaline simulated body fluid treatment

Abstract

In this study, we aimed to improve apatite-forming ability of titanium (Ti) and its alloys, Ti–15Mo–5Zr–3Al, Ti–12Ta–9Nb–6Zr–3V–O, Ti–6Al–4V, and Ti–22V–4Al. The surfaces of Ti and its alloys were treated by the doubled sandblasting process using ceramic grinding particles with 14.0 and 3.0 µm for average particle size. The Ti and its alloys were immersed in the alkaline simulated body fluid (SBF) which was adjusted at higher pH than that in the physiological SBF and were heated in the alkaline SBF by electromagnetic induction. By this treatment, apatite nucleation was promoted near the surface of the substrates and apatite nuclei were precipitated in the pores of the substrates. By immersing in the physiological SBF to test apatite-forming ability, hydroxyapatite was covered the entire surfaces of the Ti and its alloys within 1 day and high apatite-forming ability was shown. The doubled sandblasting process firstly using larger grinding particles and secondly using smaller ones was most effective to increase the surface roughness of the substrates. Average adhesive strength of the hydroxyapatite layer formed in the physiological SBF increased, which depended on the increase of the surface roughness. These results indicated that sandblasting condition was an important factor to improve mechanical interlocking effect related to the increase of the surface roughness and that the doubled sandblasting process had a possibility to be one of the candidates of the treatment to solve this problem.