Biocompatibility Analysis of Two Clinically-Employed Resin-Based Composites

Objective: Patient demand for aesthetic restorative treatment of posterior teeth combined with the fear of mercury toxicity has led the dental profession to consider alternative materials to dental amalgam. Methacrylate resin-based composites (RBCs) offer such an aesthetic alternative to dental amalgam in posterior teeth, however, unpolymerised monomers can leach from RBCs whilst in situ in the oral environment, and have been associated with adverse biological, toxicological and immunological tissue responses. Therefore, the current study aimed to determine the biocompatibility of two clinically-employed modern nanohybrid RBCs.

Method: Human oral keratinocyte TR146 cell responses were determined following direct exposure (24-72 h) to polymerised disc-shaped specimens of two commercially-available RBCs; Grandio™ (Shade A3; Voco GmbH, Cuxhaven, Germany) and GrandioSO™ (Shade A3; Voco GmbH). Biocompatibility assessment involved viable cell counts (trypan blue dye exclusion), metabolic activity (XTT assay), cellular toxicity (lactate dehydrogenase activity), reactive oxygen species generation (reduced glutathione levels), apoptosis (caspase 3/7 activity) and expression of interleukin-1α, interleukin-8, prostaglandin E₂ and tumour necrosis factor-α inflammatory cytokines.

Result: Both Grandio™ and GrandioSO™ elicited significant decreases in viable cell counts (P<0.0001), metabolic activity (P=0.0001) and reduced glutathione levels (P<0.0005) compared with untreated controls Significant increases in cellular toxicity (P<0.0012) and caspase 3/7 activity (P>0.0001) were observed for both RBCs compared with treated controls. Inflammatory cytokines expressed up to an eight-fold increase compared with untreated controls.

Conclusion: The clinically-employed RBCs employed in this study elicited significantly adverse viability, metabolic, toxicological, oxidative stress, apoptotic and inflammatory responses in human oral keratinocytes. Unset RBC material has the potential to elicit cell death and cellular toxicity in the oral environment, reducing the lifetime of the restoration and ultimately, compromising patient well-being.