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.

In previous studies regarding the osseointegration of zirconia (ZrO2) implants, a lack of consistency was observed in the surface topographies of the ZrO2 and Ti samples because of the difficult processability of ZrO2 surfaces. To resolve this problem, we used the molecular precursor method (wet process), which is a surface-modifying technique that can easily change the surface chemistry without changing the surface topography. A roughened Ti surface was prepared using sandblasting (large-grit) and acid treatment. We were able to create ZrO2-coated Ti implants with the same topography as that of roughened Ti substrates using the molecular precursor method, which solution contained a Zr complex. The uniform presence of tetragonal Zr was confirmed, and the apparent zeta potential of the surface of the ZrO2-coated Ti implant was higher than that of Ti. In animal experiments, ZrO2-coated Ti implants showed an equivalent or higher bone-to-implant contact ratio compared to that of the non-coated implants inserted into the femur bone defects of the rats. ZrO2 with the same surface topography as that of roughened Ti exhibits a promotion of osteogenesis equivalent to or better than that of Ti in the early stages of bone formation.