RESUMEN
The purpose of this study was to investigate the influence of chlorhexidine (CHX) concentration on the microtensile bond strength (ìTBS) of contemporary adhesive systems. Eighty bovine central incisors were used in this study. The facial enamel surface of the crowns was abraded with 600-grit silicon carbide paper to expose flat, mid-coronal dentin surfaces. The tested materials were Scotchbond Multipurpose (SMP), Single-Bond (SB), Clearfil SE Bond (CSEB) and Clearfil Tri S Bond (CTSB). All the materials were applied according to manufacturer's instructions and followed by composite application (Z250). The teeth were randomly divided into 16 groups: for the etch-and-rinse adhesives (SMP and SB), 0.12 percent or 2 percent CHX was applied prior to or after the acid etching procedure. For the self-etch adhesives (CSEB and CTSB) 0.12 percent or 2 percent CHX was applied prior to the primer. Control groups for each one of the adhesive systems were also set up. The specimens were immediately submitted to ìTBS testing and the data were analyzed using Analysis of Variance and the Tukey post hoc test (alpha = .01). The failure patterns of the specimens were observed using scanning electron microscopy. The effects of 2 percent CHX were statistically significant (p < 0.01) for the self-etch adhesives but were not significant for the etch-and-rinse adhesive systems. Analysis of the data demonstrated no statistical difference between the etch-and-rinse adhesive systems. CHX-based cavity disinfectants in concentrations higher than 0.12 percent should be avoided prior to the self-etch adhesive systems evaluated in this study to diminish the possibilities of reduction in bond strength.