Cytotoxicity of Bulk-Fill Composites on Stem Cells from Human Exfoliated Deciduous Teeth—An In Vitro Study

Background: This study aimed to evaluate the cytotoxicity of bulk-fill composite materials compared to conventional compomers on stem cells from human exfoliated deciduous teeth. Methods: 90 standardized resin composite discs (4 mm thick, 4 mm diameter) were fabricated using a 3D-printed plate, comprising four bulk-fill composites (SDR, Tetric EvoCeram Bulk-Fill, VisCalor Bulk, Cention-N) and one compomer (Dyract XP). Samples were polymerized per the manufacturer’s instructions and sterilized. Stem cells were isolated from the pulp of exfoliated primary teeth. Cells were cultured and exposed to extracts of the composite materials soaked in culture medium for 24 h. Cytotoxicity was assessed using the MTT colorimetric assay, measuring cell viability via mitochondrial activity, and the Annexin V assay, quantifying apoptosis and necrosis via flow cytometry. Statistical analysis was performed using ANOVA and Tukey post hoc tests. Results: All materials significantly reduced cell viability compared to the control (p < 0.05), with optical density values indicating high cytotoxicity. Tetric EvoCeram exhibited the lowest necrosis and apoptosis levels, while Dyract XP showed the highest necrosis. Statistical analysis revealed no significant cytotoxicity differences among most bulk-fill composites (p < 0.05). Conclusion: Bulk-fill composites and conventional compomer tested exhibit comparable and significant cytotoxic effects on stem cells from human exfoliated primary teeth pulp. While these materials offer clinical advantages in pediatric dentistry due to ease and speed of application, their use underscores the dilemma of balancing operative efficiency with biological safety, and their cytotoxic profiles should be taken into consideration prior to application.