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

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 etchandrinse mode with the rubbing technique for a universal adhesive system decreases the μTBS of the composite to dentin