Intracellular stress caused by composite resins: An in vitro study using a bioluminescent antioxidant-responsive element reporter assay

Context: Elucidating the effects of leachates from composite resins (CRs) on cells by examining the transcription level of detoxification genes and the antioxidant-responsive element (ARE), would be helpful in clinical practice. Aims: The aim of the study is to investigate the cytotoxicity of commercially available CRs, we used a reporter assay system to evaluate intracellular stress based on ARE-mediated transcription. Setting and Design: The study design was an in vitro study. Materials and Methods: Seven kinds of CRs were each placed in four-well plates to which culture medium was added and then light-cured. The prepared samples were used either immediately (sample A) or after incubation at 37°C for 24 h (sample B) in the subsequent ARE-luciferase reporter assay, in which HepG2 cells stably expressing an ARE-regulated luciferase reporter gene (HepG2-AD13 cells) were cultured for 6 h in culture media with the CR eluate (samples A or B) or without (control) (n = 4). In the cell viability assay, cell viability in various solutions with the same incubation time was confirmed by MTT assay (n = 4). Statistical analysis was performed using the paired t-test and one-way analysis of variance. Results: All CR solutions showed an increase in ARE activation rate; a CR with spherical nanofillers showed the highest ARE activation rate of 108.5-fold in sample A. Cell viability was not significantly reduced for any of the CRs in sample A. However, the CR-containing bisphenol A-glycidyl methacrylate (Bis-GMA) caused a significant decrease in cell viability in sample B. Conclusions: The intracellular stress in the viable cells differed among the CRs, depending on the type of monomer used. In particular, Bis-GMA-containing hydroxyl groups showed high cytotoxicity.