Methods: Sixty root canals were shaped by step-back technique, 1 mm short of the apical foramen under irrigation with sodium hypochlorite 1% (SH). At the end of instrumentation, the root canals were irrigated with EDTA17% and SH for smear layer removal. The cementum layer was removed, the root surface was washed with EDTA, and the apical 3 mm of each root were covered with a fast-setting adhesive. The canals were filled with CHP, and after sealing the access openings, the teeth were washed and placed in individual vials containing 10 mL of distilled water, which had its pH measured after 7, 14, 21 and 28 days (pH1). After removal of CHP, the root canals were divided into five equal groups and filled with Resilon / Real Seal or gutta-percha and Endofill, Sealapex, AH Plus or MTA Fillapex sealers. After storage for 7 days at 37° C in 100% relative humidity, the root canals were re-treated. After the final irrigation with EDTA and HS, the CHP was again inserted into the canals, the teeth sealed, washed and placed in new vials containing 10 mL of distilled water. Again the pH of water was measured at 7, 14, 21 and 28 days (pH2). The initial and final pH readings (pH1 and pH2) were compared by t test (p < 0.05).
Results: The pH readings obtained after retreatment (pH2) were significantly higher than those obtained before root canal filling (pH1).
Conclusions: Despite of the sealer employed, it is possible to re-establish dentin permeability to ionic diffusion after retreatment.