Effect of Elapsed Time Following Bleaching on Microleakage of Resin Composite Restorations

The elapsed time prior to the placement of bonded restoration possibly affects the bond integrity of resin composite to bleached tooth. The purpose of this study was to evaluate the effect of elapsed time after tooth bleaching on microleakage of resin composite restorations with different adhesive systems. Seventy-two extracted sound human premolars were randomly divided into 6 groups of 12 teeth each. Group I was a control group without tooth bleaching. Group II to VI were bleached with 10% carbamide peroxide using custom bleaching trays for 14 days. Group II-VI represented immediate, 1, 7, 14, and 28 days time interval between bleaching process and bonding procedure, respectively. After the elapsed time of each group, class V cavities (3x4x1.5 mm) were prepared on both buccal and lingual aspects of each tooth. An occlusal margin of the prepared cavities was placed on enamel and a cervical margin was located on root surface. All teeth of each group were treated with either an etch-and-rinse adhesive (Single Bond 2; SB) or a self-etching primer adhesive (Clearfil SE Bond X; SE), and were subsequently bulk-filled with resin composite followed by lightcured for 40 sec. Restored teeth were polished and soaked in 2% methylene blue for 2 hours. The specimens were longitudinally cut through the restored cavities with a slow-speed diamond saw obtaining three slabs for each cavity. The median scores of dye penetration were analyzed using Kruskal-Wallis test. There was no statistically significant difference in microleakage among the elapsed time after tooth bleaching (p>0.05) regardless of adhesive systems used, although, group II and III showed higher dye penetration score compared to other groups. At cervical wall, SB performed significantly higher microleakage than SE (MannWhitney U tests p<0.05).