RESUMO
Despite the increasing demand for tooth-colored restorations in dentistry, polymerization shrinkage and marginal microleakage still remains a problem.The purpose of the present study was to evaluate microleakage in three different resin composites, P90, Z250 and Z250 XT, in class V cavity of permanent human premolars.Standardized class V cavities were prepared on the buccal surface of 45 extracted human premolars. The occlusal margins of cavities were prepared at the enamel and gingival margins extending 1mm below the cementoenamel junction. The teeth were randomly assigned into three groups [N=15] and preparations restored with three different composites following the manufacturer instructions: Group A, Filtek Z250 [microhybrid composite] with Adper Single Bond total etch adhesive system; Group B, Filtek Z250 XT [nanohybrid] with Adper Single Bond total etch adhesive system;Group C, Filtek P90 [silorane] with its self-etch adhesive system [P90 system adhesive]. its adhesive system [P90 system adhesive]. The teeth were then subjected to thermal cycles [1000 cycle, 5 degrees and 55 degrees Celsius +/- 2 degrees Celsius] with a dwell time of 30 seconds, and immersed in 2% basic fuchsine for 24 hours. Longitudinally sectioned teeth were examined under the stereomicroscope. Kruskal-Wallis and Mann-Whitney U test at 95% significance level were used.Filtek Z250XT showed significantly higher microleakage than the other two composites [p<0.001]. However, there was no statistically significant difference between P90 and Filtek Z250 [p=0.217].Although all of the restorative systems had microleakage, silorane-based composite showed less microleakage compared to two other methacrylate-based composites