The effect of collagen removal on the microleakage of four single-component adhesive systems in class V composite restorations

The role of collagen fibers in dentin adhesion and hybrid layer has not clearly been established. This study evaluated the effect of collagen removal on the microleakage of four single bottle adhesive systems at resin-dentin interfaces by dye penetration technique. Methods & Materials: This experimental study was performed on 144 class V cavities prepared in buccal and lingual surfaces of human premolar teeth at the cemento-enamel junction with the cervical margin in dentin or cementum and the occlusal margin in enamel. The cavities were etched with 36% phosphoric acid for 15 seconds, rinsed and divided into 8 groups. In 4 groups the cavities were filled with a composite resin using four different dentin adhesive systems [Single Bond, Excite, One-Step, Prime & Bond NT]. In the other 4 groups the acid etched cavities were treated with a 5.25% NaOCl solution to remove the collagen and restored using the same adhesive system and composite resin. The specimens were thermocycled and stored in distilled water at 24 °C for three months and were immersed in a 10% solution of methylene blue dye for 72 hours. After rinsing, the restorations were sectioned buccolingually and assessed under an optical stereomicroscope. Microleakage was scored by two independent observers. The data were analyzed by Kruskal Wallis and Dunn multiple comparison tests. Collagen removal resulted in a significant decrease of microleakage for One-Step and an increase for Excite at cervical margin (P<0.001) but did not reduce the microleakage at cervical margins for Prime & bond NT and Single Bond group. Except collagen removal, microleakage of class V composite restoration depends on the type of bonding system which can be related to fillers, functional monomers or solvent of adhesive systems.