Increased bone apposition on a titanium oxide surface incorporating phosphate and strontium

Objective: This study investigated the osteoconductivity of titanium (Ti) implants with a phosphate (P)- and strontium (Sr) ion-incorporated oxide surface, produced by hydrothermal treatment in the rabbit cortical and cancellous bone, for future biomedical applications as a biocompatible endosseous implant surface. Material and methods: The P- and Sr ion-incorporated Ti implants (P/Sr implant) were produced by hydrothermal treatment using a P- and Sr-containing solution. The surface characteristics were evaluated by scanning electron microscopy, thin-film X-ray diffractometry, X-ray photoelectron spectroscopy and optical profilometry. Forty screw implants (20 control and 20 experimental) were placed in the tibiae and femoral condyles of 10 New Zealand White rabbits. The surface in vivo osteoconductivity of the P/Sr implants was compared with micro-arc oxidized (TO) implants with surface calcium and P chemistry by histomorphometric analysis in the cortical and cancellous bone after 4 weeks of implantation. Results: The P/Sr implants showed moderately rough surface features and had lower R_a values than the TO implants. Histologically, more direct bone apposition was observed on the surface of the P/Sr implants. The P/Sr implants displayed significantly higher bone-to-implant contact percentages compared with the TO implant in both the tibiae and the femoral condyles (P<0.01). Conclusion: The results indicate that the hydrothermally produced P- and Sr ion-incorporated Ti oxide surface may be effective in improving implant osseointegration in both cortical and cancellous bone by increasing bone apposition, due to its surface properties combining micro-topography, P/Sr chemistry and superior wettability.