Effect of bleaching treatments on microleakage of Class I restorations.

OBJECTIVE: To test the effect of bleaching agents on microleakage of composite restorations. METHODS: Sixty extracted human molar class I cavities were restored using Scotchbond 1 and Filtek Z250 composite according to the manufacturer's instructions. The teeth were randomly divided into four groups (n = 15 each). Group 1 was the control group, which was not bleached. Group 2 had a once-daily bleaching treatment with 20% carbamide peroxide gel for eight hours. Group 3 had a bleaching of 6% H2O2 for 30 minutes twice a day. Group 4 had a bleaching treatment once per day with 19% percarbonate gel for eight hours. The bleaching was carried out at 37 degrees C for 14 days. Nail varnish was applied on the apical portion of the teeth only, and the specimens were immersed in a 0.1% rhodamin-B-isothiocyanate for 24 hours at 37 degrees C. After thorough rinsing with tap water, the specimens were embedded in self-curing methacrylate resin. The blocks were sectioned with a water-cooled microtome saw into three to five slices. The cuts were positioned centrally through the restorations and approximately parallel to the long axis of the tooth in the mesiodistal direction. Microleakage was evaluated at the occlusal margins of the class I restorations using a stereo microscope. RESULTS: Microleakage occurred in all groups. The percentage of sections showing leakage was 20% (Group 1), 11% (Group 2), 15% (Group 3), and 18% (Group 4). The statistical evaluation (Kruskal-Wallis test) showed no significant difference between groups (p = 0.537). CONCLUSION: Bleaching with the materials tested has no influence on microleakage of Filtek composite bonded with Scotchbond I.