ObjectiveThe purpose of this study was to assess the effect of food-simulating liquids on the flexural strength of a methacrylate-based and a silorane-based resin composite.Materials and methodsIn this in vitro study, sixty specimens of Filtek P90 and Filtek Z350 composite were prepared in a customized mold (2 × 2 × 25 mm). The specimens of each composite were divided into five subgroups as follows: one as a control group and the other four groups included distilled water, heptane, 2% citric acid, and 50% aqueous ethanol. The specimens were stored in the solutions for one week at 37°C, and the control group was stored at room temperature for the same period of time. Then, flexural strength values were measured. The statistical analysis was performed by One-Way ANOVA, Paired T test and post hoc LSD at a significance level of 0.05.ResultsIn the control group, the mean flexural strength of Filtek P90 and Filtek Z350 were 155.1 MPa and 147.3 MPa, respectively, and there was no significant difference (P-value>0.05). The mean flexural strength of Filtek P90 and Filtek Z350 significantly decreased in ethanol (P-value <0.05). Immersion in 0.02 N citric acid and heptane had no significant effect on the flexural strength of Filtek P90 and Filtek Z350. The maximum flexural strength of Filtek P90 was in the heptane group (192.6 MPa) and minimum flexural strength was in ethanol group (92.7 MPa) the maximum flexural strength of Filtek Z350 was in the heptane group (163.2 MPa) and minimum flexural strength was in the ethanol group (104.7 MPa).ConclusionThe flexural strength of tested resin composites significantly affected by ethanol solution. The flexural strength of resin composites was not affected by other food simulating liquids.

High C-factor values generated the largest gap formation. Silorane-based composite was more efficient for cavity sealing than methacrylate-based composites and resin modified glass ionomer.