Degradation of Resin-caries-affected-dentin Bonds Treated with Water- or Ethanol-containing Chlorhexidine

Objective: The aim of this study was to evaluate the effect of different solutions of chlorhexidine on the mechanical stability of resin-caries-affected dentin bonds. 

Method: Flat dentin surfaces were produced in 72 noncarious human molars which were submitted to a protocol of artificial caries induction using S. mutans. The teeth were assigned into 12 groups (n=6) according to the adhesive system (Single Bond Plus, Prime & Bond NT and Excite) and treatment of the caries-affected dentin (1% chlorhexidine diacetate in water, 1% chlorhexidine diacetate in ethanol, ethanol or water). After removal of the infected dentin and phosphoric acid conditioning of the caries-affected dentin for 15 s, 20 µl of each solution was applied on the demineralized surface and kept passively (no agitation) for 60 s. Then the excesses were removed by blot-drying the surface.  The adhesive systems were applied and specimens were produced with an adhesive area of 0.81 mm², which were subjected to microtensile testing after 24 hours or 6 months after storage in artificial saliva. Bond strength data were submitted to analysis of variance and Tukey’ tests (α = 0.05). 

Result: No detrimental effect was observed for any of the solutions regarding the immediate bond strengths (24 hour-storage). After six months, for all adhesive systems, no reduction in bond strength was observed, except for the water-storage groups. Chlorhexidine solutions, whether using water or ethanol, were effective in producing interfaces less prone to deterioration. 

Conclusion: Overall, resin-dentin bonds produced on caries-affected dentin were more resistant to degradation when chlorhexidine, both in water and ethanol, was used as an adjunctive step in the adhesive protocol.