Ti4+ to Ti3+ conversion of TiO2 uppermost layer by low-temperature vacuum annealing:: Interest for titanium biomedical applications

Because of the Ti3+ defects responsibility for dissociative adsorption of water onto TiO2 surfaces and due to the hydroxyls influence on the biological behavior of titanium, controlling the Ti3+ surface defects density by means of low-temperature vacuum annealing is proposed to improve the bone/implant interactions. Experiments have been carried out on Ti-6Al-4V alloys exhibiting a porous surface generated primarily by chemical treatment. XPS investigations have shown that low-temperature vacuum annealing can create a controlled number of Ti3+ defects (up to 21% Ti3+/Ti4+ at 573 K). High Ti3+ defect concentration is linked to surface porosity. Such surfaces, exhibiting high hydrophilicity and microporosity, would confer to titanium biomaterials a great ability to interact with surrounding proteins and cells and hence would favor the bone anchorage of as-treated implants. (C) 2002 Elsevier Science (USA).