In Vitro Evaluation of Cytotoxicity in Novel Nano-Filled Bulk-Fill Flowable Dental Composites

Nano-filled bulk-fill flowable composites have gained widespread use in restorative dentistry owing to their ease of manipulation, reduced polymerisation shrinkage, and improved physical and esthetic properties. Despite these advantages, the potential leaching of unreacted monomers or residual nanoparticles remains a concern, as such release may compromise the biological safety of these materials. Therefore, the present study aimed to assess the cytotoxic potential of a nano-filled bulk-fill flowable composite on 3T3-L1 fibroblast cells using the MTT assay. This evaluation was undertaken to elucidate the material's biosafety profile and its suitability for clinical application.

The in vitro cytotoxicity assessment was performed in accordance with ISO 10993-5 guidelines. The nano-filled light-cured composite was finely ground, and serial extract concentrations of 25, 50, and 75 mg/mL were prepared in culture medium. 3T3-L1 fibroblasts were exposed to these extracts for 48 hours, after which cell viability was quantified using the MTT assay by measuring absorbance at 570 nm. Morphological alterations in fibroblasts following exposure were examined using phase-contrast microscopy. Statistical analysis was conducted using one-way ANOVA followed by post-hoc testing, with significance set at p < 0.05.

Mean cell viability was over 90 per cent at all of the concentrations (96.1 per cent, 94.3 per cent, 91.9 per cent), and was not significantly different at any of the controls (p > 0.05). Cells were attached with normal spindle morphology.

The tested nano-filled bulk-fill composite was found to be highly biocompatible and exhibit low cytotoxic effects, confirming that it can be used in clinical restorative cases.