Influence of Phosphoric Acid Etching on the Bond Strength of a Universal Adhesive System to Caries-Affected Dentin

The purpose of this study was to evaluate the influence of acid etching on the bond strength of a universal adhesive system (Single Bond Universal, 3M) to caries-affected dentin. Forty permanent third molars were selected and carious lesions were induced by the microbiological method with S. mutans ATCC25175. Teeth were allocated randomly across four experimental designs (n = 10): PA-I: phosphoric acid etching and application of the adhesive system, followed by immediate microtensile bond strength testing; PA-CC: phosphoric acid etching and application of the adhesive system, followed by microtensile bond strength testing after a 14-day cariogenic challenge; NPA-I: application of the adhesive system without acid etching, followed by immediate bond strength testing and NPA-CC: application of the adhesive system without acid etching followed by bond strength testing after 14-day cariogenic challenge. For microtensile bond strength testing, a restoration with Charisma composite resin was made and each specimen was sectioned with a cross-sectional area of 1 mm2. Only adhesive and mixed fractures were considered for bond strength calculation. Results were evaluated by the Kruskal-Wallis and Friedman tests. The highest bond strengths were observed in the phosphoric acid etching groups (p   0.05). The predominant fracture type was adhesive. We conclude that phosphoric acid increased the bond strength of the Single Bond Universal system to caries-affected dentin, and that cariogenic challenge did not interfere with this bond strength.