Effects of UV Photo-Functionalization of Titanium Dental Implants on Osteoblast Responses In Vitro

Osseointegration is defined as the structural and functional integration between alveolar bone and a dental implant. Photo-functionalization (PF) refers to ultraviolet (UV)-induced surface modifications of titanium implants, including changes in physicochemical properties and biological responsiveness. The aim of this study was to evaluate the effects of PF on early osteoblast responses related to osseointegration on titanium dental implants in vitro. We hypothesized that PF applied to titanium implants enhances early osteoblast responses related to osseointegration. Sixteen titanium dental implants were divided into two equal groups of eight: untreated (PF-) and PF-treated (PF+). PF+ implants were exposed to UV light at 172 nm for 10 s. An additional cell-only control group was incubated without an implant. All groups were cultured in vitro with SAOS-2 human osteoblast-like cells. Cell proliferation and viability were assessed using standard in vitro assays, and DNA damage was evaluated using the Terminal deoxynucleotidyl transferase [TdT] dUTP Nick End Labeling (TUNEL) assay. Early cellular responses related to osseointegration were assessed by evaluating adhesion-related vinculin levels and alkaline phosphatase (ALP) activity. After 24 h of incubation, cell proliferation was comparable between the groups, whereas after 48 h, cell number was significantly lower in the PF- group compared with the PF+ group and the control group (p = 0.039). Osteoblast viability was significantly lower in the PF- group than in the control group (53% vs. 94%, p = 0.002), while the PF+ group showed a numerically higher viability value than the PF- group (70% vs. 53%). TUNEL assay showed no statistically significant difference in DNA damage among the groups, although the PF- group showed a slightly higher TUNEL-positive cell ratio (p = 0.563). Vinculin levels were significantly higher in the PF+ group at both 24 and 48 h compared with the PF- group and control group (p < 0.0001). ALP activity increased significantly over time in cells incubated with PF-treated implants (p < 0.0001). Within the limitations of this exploratory pilot in vitro study, UV photo-functionalization was associated with more favorable early osteoblast-like cell responses on titanium dental implants, particularly in terms of proliferation, adhesion-related vinculin levels, and ALP response. PF did not increase TUNEL-positive cell ratios compared with untreated implants under the present experimental conditions. These findings should be interpreted as preliminary biological evidence and require confirmation through larger experimental designs, detailed physicochemical surface characterization, and in vivo validation.