Comparison of different test models for the assessment of cytotoxicity of composite resins

This study compared the use of different test models to assess the cytotoxicity of a dental composite. The cytotoxicity of a composite polymerized using two halogen-based light-curing units (LCUs) (Max LC and Astralis) and two light-emitting diode LCUs (E-light and Freelight) served as the basis of comparison. Disk-shaped specimens (7 mm diameter, 2 mm high) were fabricated using the four different light sources. The specimens were used in several cytotoxicity test models: direct and indirect contact tests as well as an extract test with an established cell line L-929. The cells were stained with neutral red after cell-material contact for 48 h. Neutral red-stained areas (in mm2, for direct and indirect tests) and absorbance readings (for extract tests) were analysed statistically using ANOVA and the Tukey post hoc test, with P < 0.05 considered to be significantly different. Good correlation between direct and indirect contact tests (r = 0.903) was found. The extract test was the least correlated among the three tests. It was found that the E-light + Freelight-cured composite elicited cytotoxicity from the correlated studies. Uncured specimens were most detrimental to the cells in all tests. Our data demonstrated that composite cured with light-emitting diode LCUs were cytotoxic to L-929 cells. Different test models were found to give rise to different findings. Thus, a good cell-material contact method would replicate more closely the physiological situation in vivo. This in turn would give more clinically relevant results.