Residual Monomer/Additive Release and Variability in Cytotoxicity of Light-curing Glass-ionomer Cements and Compomers

Abstract

In previous studies, light-cured glass-ionomer cements have been shown to evoke cytotoxic reactions. It was the purpose of this investigation (a) to determine the nature of the ingredients released into an aqueous medium from 2 light-cured glass-ionomer cements (GICs) and 3 compomers ; (b) to evaluate the cytotoxicity of these extracts; and (c) to correlate the extent of the cytotoxic effects with eluted substances. Specimens of 2 light-cured GICs and 3 compomers were prepared and extracted in distilled water or cell culture medium for 24 hrs (surface-liquid ratio 42.4 mm2/mL). The aqueous eluates were analyzed by gas chromatography/mass spectrometry (GC/MS). The relative amounts of the components released from various products were compared by means of an internal caffeine standard [%CF]. For evaluation of cytotoxic effects, permanent 3T3 fibroblasts were incubated with medium extracts for 24 hrs. In addition, the ED₅₀ concentration of the photoinitiator diphenyliodoniumchloride (DPICI) was determined. In all extracts, several water-elutable organic substances were found: (Co)monomers (especially HEMA and ethylene glycol compounds), additives (e.g., camphorquinone and diphenyliodoniumchloride), and decomposition products. The extracts of 3 products inhibited cell growth only moderately, whereas the light-cured GIC Vitrebond and the compomer Dyract Cem revealed severe cytotoxic effects. Vitrebond liberated the initiator DPICI, whereas Dyract Cem segregated a relatively high quantity [2966 %CF] of the comonomer TEGDMA in comparison with the other products. The present data show that TEGDMA and DPICI may be regarded as the prime causes for cytotoxic reactions evoked by the investigated light-cured glass-ionomer cements or compomers. Therefore, leaching of these substances should be minimized or prevented.