ObjectivesPreviously, we have reported that photocatalytically active hydrophilicity of the anatase titanium dioxide (TiO2) nanoparticles coated onto commercially pure titanium discs presented significantly improved hydrophilicity after ultraviolet irradiation. As hydrophilicity has shown enhancement of osseointegration, the in vivo responses were of great interest. The aim of this study was to evaluate whether or not the photo-activated hydrophilicity generated at the time of implant placement has an effect on the longer healing periods for osseointegration. Materials and methodsPhotocatatytically active nanostructured TiO2 powder (Degussa P-25), which consists of approximately 80% anatase and 20% rutile, was spin-coated onto commercially pure titanium discs and was heat-treated thereafter. These P25-coated discs were irradiated with ultraviolet (UV) light for the test (+UV) group, and non-irradiated discs were prepared for the control (-UV) group. Both groups of discs were placed in the rabbits' tibiae. After 12weeks of healing period, histological analysis and gene expression analysis using real-time RT-PCR were performed. ResultsFrom the histological analyses, there were no specific differences between -UV and +UV groups. However, from the gene expression analysis, ALP, RUNX-2 and IL-10 were significantly upregulated for the +UV group compared with the -UV group. ConclusionsThe biologically enhancing effect to photocatalytically activated surfaces remained even after 12weeks of healing time in terms of genetic responses.