Comparison of the Effects of Two Different Drinks on Microhardness of a Si-lorane-based Composite Resin

Statement of the problem: acidic foods and drinks can erode composite resins. silorane-based composite is a new low shrinkage composite with higher hydro-phobicity which might resist the erosive effect of beverages. purpose: the aim of this study was to determine the effects of 100% orange juice and non-alcoholic carbonated beer on microhardness of a silorane-based composite in comparison with two methacrylate-based composite resins.materials and method: ninety disc-shaped composite specimens were fabricat-ed of filtek p90, filtek z350 xt enamel and filtek z250 (3m-espe) (n=30) and randomly divided into 3 subgroups of 10.group 1 was immersed in distilled water, group 2 in 100% orange juice, and group 3 in non-alcoholic beer for 3 h/day. primary, secondary and final vickers microhardness tests were performed at the beginning of the study and 7 and 28 days later. surface of 2 specimens in each group was evaluated under scanning electron microscope on day 28. data were analyzed using repeated measures of anova model (?=0.05).results: the primary and secondary microhardness of p90 was significantly lower than that of z350, and z250 (p < 0.001). microhardness of z350 was also lower than that of z250 (p= 0.002). on day 28, microhardness of p90 was lower than z250 and z350 (p < 0.001); however, microhardness values of z250 and z350 were not significantly different (p= 0.054). microhardness of specimens subjected to non-alcoholic beer was significantly lower than that of controls (p= 0.003). meanwhile, the microhardness value of resins in orange juice was some-where between the two mentioned values with no significant difference with any of them (p > 0.05). conclusion: although 28 days of immersion in 100% orange juice and non-alcoholic beer decreased the microhardness of all specimens, p90 experienced the greatest reduction of microhardness and non-alcoholic beer had the highest effect on reducing microhardness.