Osteoblast growth behavior on micro-arc oxidized β-titanium alloy

beta-titanium (beta-Ti) alloys are known for their excellent physical properties and biocompatibility, and are therefore considered as next-generation metals for orthopedics and dental implants. To improve the osseous integration between beta-Ti alloys and bone, this study develops a titanium dioxide (TiO2) coating on the surface of beta-Ti alloys by using micro-arc oxidation (MAO) technique. The anatase (A) rich and rutile (R) rich TiO2 layer, were formed on beta-Ti, respectively. In vitro tests were carried out using pre-osteoblast cell (MC3T3-E1) to determine biocompatibility and bone formation performance. Biocompatibility includes cell adhesion, cell proliferation, and alkaline phosphatase (ALP) activity, while the bone formation performance contains osteopontin (OPN), osteocalcin (OCN) and calcium content. Cell morphology was also observed. In addition, raw beta-Ti, A rich TiO2 and R rich TiO2 were implanted into the distal femora of Japanese white rabbits for 4, 8, and 12 weeks to evaluate its in vivo performance. Experimental results show that TiO2 coating can be grown on and well-adhered to beta-Ti. The anatase phase formed under a low applied voltage (350 V), while the rutile phase formed under a high applied voltage (450 V), indicating that crystal structure is strongly influenced by applied voltage. A porous morphology was obtained in the TiO2 coating regardless of the crystal structure and exhibited superior bone formation performance than beta-Ti. In vivo analysis and in vitro test show similar trends. It is also noticeable that the R rich TiO2 coating achieved better biocompatibility, osteogenesis performance. Therefore, a MAO-treated R rich TiO2 coating can serve as a novel surface modification technique for beta-Ti alloy implants. (C) 2010 Elsevier B.V. All rights reserved.