Effect of collagen removal on microleakage of resin composite restorations

This study evaluated the effects of collagen removal on the microleakage of two single-bottle adhesive systems. Forty human third molars were selected and each received two root preparations. The roots were randomly assigned for restoration using Prime & Bond 2.1 (Dentsply Ltda, Petrópolis, RJ 90915, Brazil) or Single Bond (3M Dental Products, St Paul, MN 55144, USA). One root in each tooth was treated with 36% H3PO4 for 15 seconds and the other received an additional treatment with 10% NaOCl for 60 seconds to remove the collagen layer before adhesive was applied. All preparations were restored with Z100 restorative resin (3M Dental Products). The specimens were submitted to 5,000 thermal cycles (5-55 degrees C) and stored in 37 degrees C distilled water for one year. The specimens were then coated with a varnish except for 1 mm of tooth structure surrounding the restoration and immersed in 2% buffered methylene blue for four hours. After rinsing, the restorations were sectioned and two independent observers scored the microleakage at the interface between the restorative material and the tooth using an optical microscope at x45 magnification. The scores were submitted to Fisher's Exact Test and the results showed that collagen removal significantly reduced microleakage for Prime & Bond 2.1 and had no effect on microleakage for Single Bond.