Effect of pre-treatment on the adhesion of sealers to dentin

Objective: The adhesion of three resin based sealers (Diaket-ESPE (D), AH-Plus-Dentsply (AP) and Endo-REZ-Ultradent (ER)) was tested with different pre-treated dentin. Methods: The coronal 2/3rds of 180 extracted human third molars were removed. Polished flat dentin surfaces were then divided into four main groups and conditioned with either 19% citric acid (CA) and 5.25% NaOCl, EDTA and NaOCl, Smear Clear (SC) and NaOCl (SybronEndo) or a rinse with 10 mL distilled water (control). These groups were then divided into 3 subgroups according to the sealer used. Using a specially designed jig, the sealer was placed into a 3-mm wide x 3-mm deep well which was then set onto the tooth at a 90-degree angle and allowed to set for 7 days in 100%RH. The set-up was then placed into a mounting jig which was designed for the Instron Universal Testing Machine so that only a tensile load was applied (1mm/m). Data was calculated as MPa and statistically analyzed using a two way ANOVA. Results: Mean tensile bond strengths (MPa±SD) ranged from 10.99±0.83 (AP) to 0.62±0.14 (D). Pre-treatment with CA/NaOCl showed weaker bonds than controls in AP group. SC pre-treatment increased adhesion of ER. CA/NaOCl significantly enhanced D's adhesion to dentin. Inspection of fractured surfaces indicated failure of adhesion to dentin for D and ER. The failure appeared to be mainly cohesive within the sealer for AP. Conclusions: Removal of the smear layer may impair sealer adhesion to dentin but consideration should always be given in selecting appropriate pre-treatment because different sealers require different dentin pre-treatments for optimal adhesion.