Effect of bleaching on color change of composite after immersion in chlorhexidine and coffee

Background: Since the introduction of resin composites, the staining of resin-based materials by colored solutions such as coffee, tea, chlorhexidine (CHX), and other beverages has become a common concern. Aim: The aim of this study was to evaluate the effect of home and office bleaching as a treatment for discoloration of composite after immersion in coffee or CHX. Materials and Methods: A microhybrid composite (Z250), nanohybrid composite (Z550), and nanofill composite (ultimate, body shade) were selected. Forty disk shape specimens (8 mm diameter and 2 mm thickness) for each composite were prepared then divided into two groups according to staining solutions (25 g of coffee in 250 ml water, 20 min/day or 0.2% CHX, 1 min/day). Following 1 month staining, specimens were divided into two groups again. Half of the specimens was bleached with in office bleaching agent (Opalescence Boost 40% hydrogen peroxide concentration) 3 times in one visit for 15minutes and the others subjected to home bleaching agent(Opalescence 10% carbamide peroxide) 6h/day until 2 weeks both from Ultradent Products, Inc., South Jordan, UT, USA. Color of the specimens was measured with a spectrophotometer using CIELAB color space at baseline, after 1 month staining, and after ending the bleaching process. Statistical Analysis: Analysis of variance was used to analyze the data (P < 0.05). Results: Coffee and CHX provided significant color changes in all groups (P < 0.05). Z550 was the material more prone to discoloration in coffee in comparison with Filtek Ultimate (P = 0.003). After bleaching, materials showed significant reduction except stained Z550 by coffee in home bleaching groups. Both home and office bleaching provided significant color changes in all CHX groups (P < 0.05). Conclusion: Coffee produced more color changes than CHX. The hydrogen peroxide has the same whitening effect in comparison with carbamide peroxide.