Comparative investigations on the bioactivity of surface grain refined titanium and surface oxidized titanium for biomedical implant applications

Surface engineering of titanium (Ti) for medical implant applications is an active research area in the biomedical field across the globe. Improving the bioactivity of the Ti surface is crucial for implant applications where osseointegration is essentially required to enhance the healing rate. In the
present work, shot peening followed by micro-arc oxidation (MAO) treatments were applied to pure Ti with an objective to investigate the role of surface grain refinement and the oxide layer on biomineralization ability to assess the bioactivity of the surface. After shot peening with steel balls, Ti substrates were subjected to MAO using sodium phosphate solution. Grain refinement was observed at the surface after the shot peening at a submicrometer levels ranging from 0.5 to 2 µm for a thickness of 50µm. Ti sheets subjected to MAO exhibited a porous oxide layer on the surface. From the XRD analysis, the TiO2 layer was observed as a combination of anatase and rutile. Higher Ca/P-based apatite deposition on shot-peened Ti compared with MAO Ti was observed in the in vitro immersion studies. The results indicated increased bioactivity for grain refined Ti compared with MAO Ti. Hence, it is concluded that the microstructure influences the bioactivity of Ti implants compared with the oxide layer.