Influence of the Surface Chemical Composition Differences between Zirconia and Titanium with the Similar Surface Structure and Roughness on Bone Formation

The osseointegration of zirconia (ZrO2) implants is still controversial. In this study, we aimed to make clear the influence of surface chemical composition, Ti or ZrO2, to osseointegration. First, a roughened Ti surface was prepared with a combination of large-grit sandblasting and acid treatment. Then, we applied molecular precursor solution containing Zr complex onto roughened Ti surface and can deposit thin ZrO2 film onto roughened Ti surface. We can change surface chemical composition from Ti to ZrO2 without changing the surface structure and roughness of roughened Ti. The tetragonal Zr was uniformly present on the ZrO2-coated Ti surface, and the surface of the ZrO2-coated Ti showed a higher apparent zeta potential than Ti. Ti and ZrO2-coated Ti rectangular plate implant was placed into the femur bone defect. After 2 and 4 weeks of implantation, histomorphometric observation revealed that the bone-to-implant contact ratio and the bone mass values for ZrO2-coated Ti implants inserted into the femur bone defects of the rats at 2 weeks were significantly higher than those for Ti implants (p < 0.05). It revealed that ZrO2 with a similar surface structure and roughness as that of roughened Ti promoted osteogenesis equivalent to or better than that of Ti in the early bone formation stage.