Effect of Peroxide Bleaching Systems on the Marginal Integrity and Surface Hardness of Composite Restorations

Abstract

Peroxide bleaching systems may affect resin composite restorations through their strong oxidative effect. The objective was to investigate the influence of bleaching systems on long-term stability of marginal integrity of composite restorations and composite surface resistance. Class V cavities were prepared at the enamel-dentine junction and filled using a total-etch adhesive system Gluma Comfort Bond (n=36) and self-etching adhesive iBond (n=36) in combination with the microhybrid resin composite material Charisma. The peroxide bleaching gel Opalescence PF 20% (20 wt. % carbamide peroxide) was applied 25 times on the restorations. The control groups were exposed to distilled water for 24 hours and two months before a microleakage test was performed. Composite hardness was characterized after 0, 2, 7, 14 and 25 applications of the gel and compared with the control group (each n=5) exposed to distilled water for two months. Surface morphology was evaluated using scanning electron microscopy. After the gel application no significant changes in marginal integrity were found for both groups of samples. With Gluma Comfort Bond due to its high bonding performance and with iBond due to its decreased performance on enamel causing marginal integrity failure at the beginning of the experiment. On the other hand, pronounced surface porosity and decreased hardness of the composite material indicated its significant degradation in the presence of the bleaching gel.

Keywords

• bleaching
• microleakage
• marginal integrity
• adhesive
• restorative composite
• surface hardness