الخلاصة

Abstract Background: Bleaching the discolored teeth may affect the sealing ability of immediately placed composite resin restoration. The aim of this in vitro study was to evaluate and compare the neutralizing effect of delayed bonding and different antioxidant agents on the microleakage of composite restoration in endodontically treated teeth after intracoronal bleaching with hydrogen peroxide. Materials and methods: Following endodontic therapy, 60 sound human mandibular 2nd premolar teeth of comparable sizes were randomly divided into six groups, each of 10 samples (n=10). Except Group A (negative control), all samples in the other groups were exposed to internal bleaching with 35% hydrogen peroxide (Opalescence® Endo ‘’walking’’ bleach) that placed into the pulp chamber for 5 days. For Group B, the samples were immediately bonded after bleaching. Group C, the bonding procedure was delayed 2 weeks after bleaching. Groups D, E and F, the samples treated with 10% Sodium Ascorbate (SA), 10 % Green Tea (GT) and 10% Pine Bark (PB) respectively and then restored immediately. In all groups, the access cavities were restored using Scotchbond™ Universal Adhesive and Filtek™ Bulk Fill posterior restorative composite resin. Teeth were subjected to 500 thermal cycles and immersed in 2% methylene blue for 1 day. Teeth were sectioned longitudinally from buccal to lingual direction, passing through the center of the restoration, using a diamond disk. The samples were examined under stereomicroscopic magnification (40X). Microleakage was assessed with a 0 – 4 scoring system and analyzed using nonparametric statistical methods (α =0.05). Results: Internal bleaching with 35 % hydrogen peroxide gel for 5 days resulted in significant (p >0.01) increase in microleakage of composite resin restorations when bonding was performed immediately after bleaching (Group B). No significant difference (p>0.05) was found between negative control group (Group A) and group that bonded after 14 days after bleaching (Group C). Furthermore, there was no significant difference among groups that bonded after treatment with 10% of antioxidant materials (D, E and F) when compared to each other, and when compared to control group (Group A). Conclusion: The use of antioxidants effectively reversed the compromised sealing ability of composite filling to bleached dental tissue and all the antioxidants used in this study was equally effective to neutralize the adverse effects of hydrogen peroxide on microleakage of immediately restored teeth. Keywords: Bleaching; Microleakage; Green Tea; Pine Bark; Sodium Ascorbate