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Introduction: The effect of final finishing and polishing time on the microleakage of composites restorations are not yet recognized. Therefore, this study aimed to evaluate the effect of final finishing and polishing time on microleakage of  hybrid composite restorations.

Methods: In this in-vitro study, 40 molar teeth of class 5 cavity(2mm occlusogingival×3mm mesiodistal×1.5mm depth) were prepared at the buccal surface. The cavities were restored via Z₂₅₀ composite and cured for 40 seconds by LED Valo. The cavities were randomly divided into 4 groups(n=10) according to the polishing time(immidiate, polishing 15 minutes, 24hours and one week after restoration). The teeth were subjected to 500 thermal cycles and submerged in 2% fuchsin to evaluate rate of microleakage. After monting, the specimens were sectioned in half, that both halves were examined under a stereomicroscope. Kruskal Wallis and Mann Whitney tests were applied in order to analyze the study data ( &alpha=0.05).

Results: Polishing time did not produce any effects on the microleakage in the dentine margin )Pvalue=0/56) and even enamel margin (Pvalue=0/12). The difference between microleakage rate of dentine margin and enamel margin  was not demonstrated to be significant in regard with polishing immediately (Pvalue=0/26( and polishing after 15 minutes )Pvalue=0/53) , though polishing after 24 hours (Pvalue=0/03) and one week ( Pvalue=0/00) was reported to make a significant difference between the both margins. Moreover, the rate of microleakage was observed less in the enamel margin.

Conclusion: The study findings revealed that different polishing time does not have any effect on the microleakage rate of Z₂₅₀ restorations in both dentine margin and enamel margin.