effect of preheating on the cytotoxicity of bulk-fill composite resins

Background. due to the effect of pre-heating on the degree of conversion of composite resins and the possible effect on cytotoxicity, the effect of pre-heating of bulk-fill composite resins was investigated on cytotoxicity in this study. methods. in this study, three different types of composite resin were used, including tetric n-ceram bulk-fil, xtrafil, and xtrabase. from each composite resin, 10 cylindrical samples (5 mm in diameter and 4 mm in height) were prepared, with five samples preheated to 68°c, and the other five samples polymerized at room temperature (25°c). twenty-four hours after polymerization, cytotoxicity was assessed by mtt assay on human fibroblasts. statistical analysis of data was carried out with two-way anova and sidak post-hoc. the significance level of the test was determined at 0.05. results. there was no statistically significant difference between the mean percentage of cytotoxicity in terms of pre-heating (p>0.05), but the cytotoxicity of the studied composite resins was significantly different (p<0.001). the cytotoxicity of tetric n-ceram bulk-fil composite resin was higher than that of the two other composite resins. conclusion. pre-heating of bulk-fill composite resin did not affect their cytotoxicity. in addition, the cytotoxicity of different bulk-fill composite resins was not the same.