الفهرس 
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Abstract
Objective: This study was aimed to evaluate the effect of food simulating solvents on surface roughness and microhardness of bulk fill resin composites in vitro. Material and methods: A total number of 180 disc-shaped specimens (7 mm in diameter × 3 mm thickness) were made with three different bulk fill composites (Filtek One Bulk Fill Restorative, REVEAL HD Bulk and x-tra fil Bulk Fill Composite (n=60). Using a split Teflon mold, the composite material placed in a single increment into the mold and it was sandwiched between two straight, transparent Mylar strips and pressed between two microscopic glass slides on each side. After light-curing for all three groups, all specimens were removed from the mold and polished using (medium, fine, and super-fine grains of Sof-Lex aluminium oxide discs. Immediately after polymerization and before immersion the specimens were stored in an incubator at a 37 ±1◦C for 24 h. The baseline data of surface roughness and Vicker’s microhardness measurements (24 h) were recorded. Each group divided into three subgroups, subgroup1, specimens were immersed into methyl ethyl ketone (n=20), subgroup2, were immersed into ethanol (n=20) and subgroup3, specimens were immersed into artificial saliva (n=20) as control group. After exposure of specimens to solvents, half of the specimens of each subgroup was tested for surface roughness (n=10) by surface profilometer and the other half was tested for microhardeness (n=10) by Vicker’s microhardness tester. Morphological changes were evaluated by scanning electron microscopy. The collected data of each test were coded and statistically analyzed using two-way analysis of variance (ANOVA) followed by post-hoc Tukey multiple comparisons. Pearson correlation was used to correlate surface roughness and microhardness.Results: All tested materials showed significant differences in surface roughness and microhardness. x-tra fil Bulk Fill Composite group had the most statistically significant increasing in surface roughness and the most significant decreasing in microhardness was in Filtek One Bulk Fill Restorative. Methyl ethyl ketone caused the most surface changes in bulk-fill resin composites. SEM photomicrographs showed surface changes of all resin composites in varying degrees.Conclusion: Food simulating solvents increased surface roughness and decreased surface microhardness of bulk fill resin composites. Microhybrid x-tra fil is the most affected material regarding surface roughness and also affected overly by Methyl ethyl ketone among the FSLs. Filtek One Bulk Fill showed the most decreasing in microhardness.