Methods: Occlusal enamel of 48 non-carious human third molar teeth were removed. Specimens randomly divided into control groups (G1, G2) and Chlorhexidine groups (G3, G4). Dentin surfaces were etched with 37% phosphoric acid gel (Ultra-etch, Ultradent, USA) for 30 seconds, rinsed with distilled water for 10 seconds, and dried. Adhesive resin (PQ1, Ultradent, USA) applied and cured for 20 seconds. Two increments of 2 mm Composite resin (Amelogen, Ultradent, USA) were placed inside a washer mounted on the surface and each layer light cured for 40 seconds (Blue Phase C8, Ivoclar Vivadent, Schaan, Lichtenstien). In Chlorhexidine groups before applying adhesive, dentin surfaces were treated with 2% chlorhexidine (Shahrdad, Iran) for 30 seconds. In each group Shear bond strength (SBS) were evaluated immediately (G1, G3); and after two months storage(G2, G4) in collagenase solution (Sigma-Allorich, Usa) by universal testing machine (Zwick/Z250, Type KAP-Z, Zwick Roell Group, Ulm, Germany). Data were analyzed by two-way ANOVA and Tukey post-hoc test at significance level of 0.05 with SPSS version 11.0 software.
Results: The mean SBS was 14.6700 ±1.50634, 15.6092 ±1.68335, 10.3342 ±1.44849, and 14.7467 ±1.96915 in G1, G2, G3, and G4 respectively. One-way ANOVA test revealed no significant difference in immediate SBS among groups (P-value>0.05). After 2 months storage, SBS was significantly reduced in control group (P-value<0.05) but no significant differences in chlorhexidine group observed (P-value<0.05). SBS in Chlorhexidine group was significantly higher than the control group after 2 months (P-value<0.05).
Conclusions: Chlorhexidine had no adverse effect on immediate bond strength and could preserve the dentin bond after two months collagenase storage.