Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Introduction: The aim of this study was to evaluate the influence of different irrigation protocols on resin-based sealer bond strength to dentin and the associated failure pattern. Methods: One hundred eighty single-rooted premolars were used. Roots were divided into 18 groups according to the irrigation protocol used and instrumented using 5.25% NaOCl or 2% chlorhexidine (CHX) gel as chemical auxiliary substances and 17% EDTA or 37% phosphoric acid for smear layer removal. Finally, CHX solution was used as the final irrigant in some groups. Root canals were filled with either gutta-percha and AH Plus (Dentsply, Petropolis, RJ, Brazil) (GP/AH) or Resilon/Real Seal SE (SybronEndo, Orange, CA). Bond strength was measured by the push-out test. Additionally, failure patterns were classified as adhesive, cohesive, and mixed. Data were statistically analyzed by Kruskal-Wallis and Mann-Whitney U tests. Results: In the GP/AH groups, high bond strength values were obtained when NaOCl was associated with phosphoric acid with (6.9 +/- 3.9) and without (7.4 +/- 3.8) a final flush with CHX. However, when CHX gel was used, the association with EDTA with (7.5 +/- 3.2) and without (6.0 +/- 2.3) a final flush with CHX solution showed better results. The GP/AH groups mainly showed a cohesive failure pattern. Evaluation of Resilon/Real Seal SE showed that higher bond strength values were reached when CHX was associated with phosphoric acid with (5.2 +/- 3.0) and without (4.2 +/- 2.0) a final flush with CHX solution. The failure patterns were mainly adhesive. Conclusions: Irrigation protocols influenced the bond strength of resin sealers to dentin.395689692Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2009/53976-0, 2010/50817-5]CNPq [302575/2009-0]