Optimising the bioactivity of alkaline-treated titanium alloy

A layer of sodium titanate hydrogel on titanium alloy (Ti6Al4V) induces apatite formation in simulated body fluid (SBF). This paper seeks to determine the parameters of alkaline-treated and subsequent heat treatment which lead to the most rapid formation of apatite. Specimens were soaked in 3, 5, 10 or 15 M solutions of NaOH at temperatures of 60 or 80 °C for 1, 3 or 7 days. It was found that the optimum treatment for the Ti6Al4V alloy was a 3-day soak in 5 M NaOH solution at 80 °C. Specimens treated under these optimum conditions were subsequently heat-treated at 500, 600, and 700 °C for 1 h so as to consolidate the sodium titanate hydrogel layer and improve its bonding to the substrate. Treatment at 600 °C resulted in the best bonding and the optimum rate of apatite formation. On soaking in simulated body fluid (SBF), apatite formed within 3 days, as compared to the 7-day formation, which was the best rate previously reported. The acceleration in the rate of apatite formation is significant, as it should allow for earlier load bearing of prostheses following implantation.