Effect of Chlorhexidine Incorporation into Dental Adhesive Resin on Durability of Resin-Dentin Bond

Purpose: This study evaluated the effect of chlorhexidine (CHX) incorporation into experimental dentin adhesives with different hydrophilicities on the microtensile bond strength (µTBS) to dentin. Materials and Methods: Flat, deep dentin surfaces were prepared from 60 extracted human third molars. Three ethanol-solvated (50 wt% ethanol/50 wt% comonomers) experimental adhesives with varying degrees of hydrophilicity were prepared for the CHX-free groups. For the CHX-containing groups, chlorhexidine diacetate was further added to the ethanol-solvated adhesives to form a concentration of 2.0 wt% CHX. Dentin surfaces were etched with 37% phosphoric acid for 15 s, rinsed and blot dried before bonding. The adhesives were generously applied to dentin with a microbrush for 15 s. A second application of fresh adhesive was made and light cured for 20 s (600 mW/cm2) after solvent evaporation. Composite buildups were made using Filtek Z250 (3M ESPE). The bonded teeth were sectioned into 0.9 mm x 0.9 mm beams and stressed to failure at a crosshead speed of 1 mm/min. Testing was performed 24 h after specimen preparation and 12 months after storage in artificial saliva. The µTBS data were analyzed using three-way ANOVA and Tukey's multiple comparison tests. Fractographic analysis was performed by SEM. Results: Significant differences were observed for the three factors "adhesive hydrophilicity" (p 0.001), "CHX incorporation" (p = 0.001), and "storage time" (p 0.001). Interaction among these three factors was also significant (p 0.001). Incorporation of CHX had no effect on the immediate bond strength of the three experimental adhesives (p > 0.05). After storage in artificial saliva, significant reduction in bond strength was observed in all adhesive groups, except for CHX-containing adhesive I (p 0.001). The µTBS of the CHX-containing experimental adhesive III was significantly higher than the corresponding CHX-free adhesive (p 0.001) after aging. Conclusion: When incorporated into hydrophilic dental adhesives, chlorhexidine can partially reduce the degradation of the resin-dentin bonds. Keywords: chlorhexidine, resin, dentin, longevity, degradation