Purpose: The purpose of this study was to compare changes in the physicochemical and biologic characteristics of titanium surfaces through short-term re-hydrophobization for 24 hours and ultraviolet (UV) re-irradiation for 24 hours.

Materials and methods: Photofunctionalization was performed with four 15-W bactericidal lamps at an intensity of 5.0 mW/cm² (wavelength = 254 ± 20 nm) on sandblasted, large-grit, acid-etched (SLA)-treated titanium surfaces, which were stored in a sterilized sealed container for 8 weeks to allow enough biologic aging. The duration of the UV irradiation was as follows: irradiation group-UV irradiated for 24 hours; re-hydrophobization group-UV irradiated for 24 hours and then stored in an ambient sterilized medium; and re-irradiation group-UV irradiated for 24 hours followed by storing for 24 hours in an ambient sterilized medium and then UV re-irradiated for 24 hours. The surface characteristics were evaluated with field emission scanning electron microscopy, x-ray photoelectron spectroscopy (XPS), and water contact angle. Cell viability and morphology were measured using fluorescence staining. Alkaline phosphatase (ALP) assay and alizarin red S staining were performed to evaluate the differentiation of osteogenic cells and the mineralization capability.

Results: Macroroughness and superimposed microroughness were observed on the disk surfaces in all groups as typically seen on SLA surfaces. The water contact angles were measured to be 1.85, 1.48, and 1.18 degrees for the irradiation group, re-hydrophobization group, and re-irradiation group, respectively, indicating superhydrophilicity. There was no difference in the surface elemental ratio or the spectra of XPS, cell viability, or ALP activity. Although the re-irradiation group had the highest total amount of calcium deposition, there was no statistical significance.

Conclusion: Within the limitations of the study, improved superhydrophilicity and bioactivity after UV irradiation were maintained during short-term re-hydrophobization and repeated re-irradiation without changing the topography of SLA titanium surfaces.