Effect of etching the coronal dentin with the rubbing technique on the microtensile bond strength of a universal adhesive system

Abstract

Background. The adhesion of composite resins to the dentin substrate is influenced by the treatment of the smear layer. While etch-and-rinse systems require dentin to be conditioned with phosphoric acid, self-etching systems preserve the smear layer by incorporating it into the adhesive layer. Objectives. The objective of this study was to evaluate the influence of etching with the rubbing technique on the microtensile bond strength (μTBS) of a universal adhesive to dentin. Material and methods. Eighteen extracted teeth were selected. Two etch-and-rinse techniques (with and without rubbing) and a self-etching technique were used to bond the dentin surfaces with a universal adhesive system. After 24 h, the bonded samples were prepared for the μTBS testing. The specimens were loaded with a tensile force at a crosshead speed of 0.5 mm/min until failure. The scanning electron microscope (SEM) analyses were used to reveal the failure modes. The data were statistically analyzed with the one-way analysis of variance (ANOVA) and χ2 tests. Results. The etch-and-rinse system with rubbing produced significantly lower bond strength (42.11 ±9.26 MPa,) than the etch-and-rinse system without rubbing (47.30 ±8.12 MPa) and significantly higher bond strength than the self-etching system (38.07 ±9.49 MPa). Conclusions. Under the conditions of this study, dentin etched with phosphoric acid for 3 s in the etch-and-rinse mode with the rubbing technique for a universal adhesive system decreases the μTBS of the composite to dentin.