The potential cytotoxic effect of recent universal adhesives with modified monomeric compositions on human gingival epithelial cells

This study aimed to assess the cytotoxicity of three recent universal adhesives (UAs) with modified monomeric compositions compared to a typical adhesive containing bisphenol A-glycidyl methacrylate (Bis-GMA) and hydroxyethyl methacrylate (HEMA) on human gingival epithelial cells. Disk-shaped specimens of Scotchbond Universal Plus (SBP), Zipbond Universal (ZBU), Clearfil TRI-S Bond Universal Quick (CSQ), and Tetric N-Bond Universal (TNB) were fabricated and then kept in Dulbecco's Modified Eagle Medium (DMEM) for 24 h to prepare the extract medium. Cytotoxicity was evaluated with MTT, SRB, and ROS analyses. Data were analysed by ANOVA and Tukey's post hoc multiple comparison tests (P ≤ 0.05). At both tested concentrations (50% & 100%), MTT results showed that SBP, ZBU, and TNB significantly reduced cell viability compared with the control, in contrast to CSQ, which exhibited the highest viability. Regarding SRB results, SBP, ZBU, and CSQ maintained cell viabilities comparable to the control and significantly higher than TNB at both concentrations. ELISA results revealed statistically significant differences in ROS levels among all tested UAs compared to the control and to each other. The cytotoxicity of UAs is both composition and concentration-dependent, with modified formulations showing relatively safer profiles reflecting the potential effect of modifying the monomeric formulations in enhancing cytocompatibility.