Cytotoxicity and Genotoxicity of Resin-Based Dental Composites Modified with Quaternary Ammonium Salts

The primary reason of dental restoration failure is the recurrence of caries, driving research to incorporate quaternary ammonium salts (QASs) into resin-based composites (RBCs). Given the prolonged contact of these materials with oral tissue, this in vitro study assessed the biocompatibility (cytotoxicity and genotoxicity) profiles of experimental RBCs modified with cetyltrimethylammonium bromide (CTAB) and dimethyldioctadecylammonium bromide (DODAB), using two restorative materials: an unmodified–experimental composite, KE, and Flow-Art (FA) as comparative standards. The primarily novelty of this study is the direct comparison of the cellular safety profiles of CTAB vs. DODAB when incorporated into RBCs. Human fibroblast BJ cells were exposed to composite eluates for 24 h, and cell viability (MTT assay), the percentage of apoptotic and necrotic cells (the Annexin V/Propidium Iodide (PI) flow cytometry method), and DNA damage (the alkaline comet assay) were quantified. Among the compounds evaluated, only CTAB caused a significant, dose-dependent decrease in BJ cell viability, primarily by inducing late apoptosis or necrosis. Cell viability was severely reduced, dropping by 84% at 2 wt% CTAB (p < 0.001) compared to control. Consistent with this effect, CTAB also induced a dose-dependent increase in DNA damage. In contrast, the DODAB-modified composites, along with the KE and FA controls, exhibited non-cytotoxic and non-genotoxic profiles across all tested concentrations. This innovative comparative assessment highlights that DODAB exhibits superior cellular safety, offering vital guidance to prioritize its use for developing safe and effective next-generation antibacterial dental composites. Conversely, CTAB is precluded for clinical use at these concentrations due to its observed toxicity.