Eugenol diffusion through dentin related to dentin hydraulic conductance

Abstract

Objectives: The purpose of this study was (1) to find an easy way of evaluating the concentration of eugenol in cell culture fluids; (2) to confirm the relationship between the concentration and the cytotoxicity of eugenol in vitro; (3) to evaluate the cytotoxicity of four temporary eugenol-based filling materials: IRM, super EBA, Kalsogen and zinc oxide–eugenol cement; and (4) to establish a relationship between dentin permeability, eugenol diffusion and cytotoxicity. Methods: (1) The concentration of eugenol was measured with a spectrofluorimeter; (2) the cell viability of L 929 cells cultivated for 24 h with eugenol-containing medium was evaluated by the MTT assay; (3) after measurement of hydraulic conductance, occlusal cavities in human teeth in vitro were filled with the restorative materials. The cytotoxicity was measured with undiluted test medium and with various dilutions in culture medium; (4) after Lp measurement, the eugenol concentration in the media in the pulp chamber that diffused from IRM and 10 −3 mol/l eugenol solution was measured. Results: (1) A proportional relationship ( p=0.001 and r=1) was found between the concentration of eugenol; (2) eugenol started to be cytotoxic at 10 −5 mol/l and killed 95% of the cells at 10 −3 mol/l; (3) zinc oxide–eugenol cement was the most cytotoxic filling material when tested with the 1:100 dilution; (4) a significant relationship was found between Lp and cytotoxicity ( p=0.04) depending on the dilution of the test medium. A significant relationship was found between Lp and eugenol diffusion from a 10 −3 mol/l solution ( p=0.03) but not between Lp and eugenol diffusing from solid IRM (non significant). Significance: Eugenol diffusion from zinc oxide–eugenol cement appears to depend more on the role of hydrolysis of eugenol from zinc oxide–eugenol cement than on dentin permeability.