In vitro toxicity of spiroorthocarbonate monomers designed for non-shrinking dental restoratives

In development of photopolymerized expanding monomers with epoxy resin syst ems, there is a need for reactive expanding monomers that exert a good bioc ompatibility profile. The objective of this study was to evaluate the in vi tro toxicology of new spiroorthocarbonates designed to be expanding monomer s. The expanding monomers investigated were: trans/trans-2,3,8,9-di(tetrame thylene)-1,5,7,11-tetraoxaspiro[5,5]undecane (DTM-TOSU), 5,5-diethyl-19-oxa dispiro-[1,3-dioxane-2,2'-1,3-dioxane-5',4'-bicyclo[4.1.0] heptane] (DECHE- TOSU); 3,9-diethyl-3,9-dipropionyloxy methyl-1,5,7,11-tetraoxaspiro[5.5]und ecane (DEDPM-TOSU); and 3,9-diethyl-3,9-diacetoxy methyl-1,5,7,11-tetraoxas piro[5,5]undecane (DAMDE-TOSU). The in vitro toxicology of these monomers m easured their cytotoxicity and mutagenicity potential. Succinic dehydrogena se (SDH) activity in the MTT assay was used to assess the toxic dose that k ills 50% of cells (TC50) for all the monomers. Their mutagenic potential wa s measured in the Ames Salmonella assay with and without metabolic activati on. Two solvents, DMSO and acetone, were used to validate effects. Appropri ate controls included the solvents alone. All the expanding monomers in thi s study were less cytotoxic than BISGMA (p < 0.01), a commercial component of dental restoratives. The relative cytotoxicity of the expanding monomers in DMSO was defined in the following order: DTM-TOSU (more toxic) > DECHE- TOSU > DEDPM-TOSU > DAMDE-TOSU. Each was significantly different from the o ther (p < 0.05). Overall, the TC50 values of all expanding monomers were si gnificantly greater in DMSO than in acetone (p < 0.05). However, for BISGMA this trend was opposite. For mutagenicity results, the expanding monomers were non-mutagenic and there was no solvent effect on this outcome. The non -mutagenicity and low cytotoxicity profile of these expanding monomers sugg ests their potential for development of biocompatible non-shrinking composi tes.