Surface modification of titanium by anodic oxidation in phosphoric acid at low potentials: in vitro and in vivo study

S. CERE; M. KATUNAR; J. BALLARRE; A. CISILINO; J. C. ORELLANO; A. GOMEZ SANCHEZ

Praga

Congreso; 63st Meeting of the Internacional Society of Electrochemistry; 2012

Internacional Society of Electrochemistry

Surface modification of titanium in the nanometrical range was performed in order to improve both the biocompatibility and the corrosion resistance in the biological media. The presence of anatase and the incorporation of phosphate to the surface film was determined, while the electronic properties of the surface oxide presented a carrier number adequate for biomedical applications. The increase in the film thickness from 3 to 42 nm was estimated from EIS results when anodising potentials from 0 to 30 V were applied, whereas a bi-layer structure of the protective oxide was determined. Electrochemical test were performed in simulated body fluid (SBF), in order to evaluate the corrosion resistance of the anodic oxide layers after 24h and 30 days of immersion. After immersion a slight increase in the passivity current density during anodic polarization tests evidences that the SBF exposition produces minor effects on titanium surfaces, and the barrier layer remains effective against corrosion since neither rupture of the film nor localized corrosion occurs. Besides,  no significant changes in corrosion barrier effect of the surface films (native or anodised) is evidenced with EIS, in accordance with anodic polarization tests. In vivo implantation of as received and 30 V anodised Ti samples were performed in Wistar rats. Micro-computed tomography and 3D reconstructions after 60 days of implantation showed that the relative quantity of new bone surrounding the implants was similar for both surface finishes (Figure 1a and b). However, it can be observed a noticeable difference in their topology: while the new bone in the 30V anodising treatment is uniform and completely covers the implant surface, the bone in the as-received titanium presents a discontinuous structure with holes, with uncovered portions of the surface implant.