In vitro cytotoxicity of a low-shrinkage polymerizable liquid crystal resin monomer

The objective of this study was to determine the in vitro cytotoxicity of novel, polymerizable liquid crystal resin monomers when placed in direct contact with dental and nondental cell lines. One common dimethacrylate and three liquid crystal compounds, Bisglycidyl methacrylate (Bis-GMA), 2-(t-butyl)-1,4-bis-{4-(6-acryloxy-hexane-1-oxy)-benzoyloxy}-benzene (C6), 2-(t-butyl), 1-[6-(3-acryloxy-propionoxy)-hexane-1-oxy-benzoyloxy], 4-[4-(6-acryloxy-hexane-1-oxy)-benzoyloxy]-benxene (by-product), and a 3:2 mixture of C6 and by-product, respectively, were tested for relative cytotoxicity in vitro. Cultured dental and nondental cells were treated for 24 h with test compound dissolved in media over a fourfold range of concentration (10^-4 -10^-7 mol/L). Cytotoxicity was measured using the WST-1 reagent as an indicator of remaining cell numbers based on the reduction of WST-1 substrate by mitochondrial dehydrogenases in viable cells. Bis-GMA ID₅₀ was found to be consistent with ID₅₀ values reported in the literature. A small but significant difference in the sensitivity of the dental and nondental cells in regard to their response to this dimethacrylate was noted. The liquid crystal resin monomers were significantly less cytotoxic to all cell lines tested. ID₅₀ values of >1 × 10 ^-4 mol/L were registered for the C6 and by-product monomers alone. The 3:2 mixture of C6 and by-product had a slightly higher cytotoxicity (ID ₅₀ = 1 × 10^-4 mol/L); however, this remained significantly less than that of Bis-GMA. The results demonstrate that the newly synthesized low-shrinkage, polymerizable liquid crystal resin monomers demonstrate a minimal cytotoxic effect on both dental and nondental cells. These data suggest that the low-shrinkage liquid crystal resin monomers will not elicit a response by oral tissues (pulp tissue) when used to repair carious lesions in posterior teeth.