Materials and Method: In this experimental study, the occlusal enamel of each sixty caries-free mandibular molars was removed and their midcoronal dentin was exposed. The specimens were then mounted in auto-polymerizing resin 1mm apical to CEJ. Then, the specimens were divided into 6 groups (n=10) based on contamination with a hemostatic agent (H), application of chlorhexidine (CHX) and the adhesive system used and then were classified as Group 1: Adper Single Bond (ASB) Group 2: H+ASB Group 3: H+0.2% CHX+ASB Group 4: Clearfil SE Bond (CSB) Group 5: H+CSB Group 6: H+0.2% CHX+CSB. Then, composite resin rods (4×2 mm) were built up on the dentin surfaces and after thermocycling, the SBS (MPa) was evaluated. Statistical analysis was performed using two-way ANOVA and post hoc Tukey tests (p< 0.05).

  Results: There were statistically significant differences between bond strength values of group 1 (ASB) and group 2 (H+ASB) (p< 0.001) and group 1 (ASB) and group 3 (H+CHX+ASB) (p< 0.001). Similarly, significant differences were seen between group 4 (CSB) and group 5 (H+CSB) (p< 0.001) and between group 4 (CSB) and group 6 (H+CHX+CSB) (p< 0.001). 

  Conclusion: Contamination with hemostatic agent reduced the SBS of both total- and self-etching adhesive systems. In addition, application of chlorhexidine after the removal of hemostatic agent had a negative effect on SBS of total- and self-etching adhesive systems.