Endodontic re-instrumentation enhances hydroxyl ion diffusion through radicular dentine

Aim To evaluate the diffusion of hydroxyl ions from calcium hydroxide paste (CH) before root canal filling and after retreatment. Methodology After preparation of 60 root canals, the cementum layer was removed, and the canals and root surfaces were treated for smear layer removal. The apical third of roots was covered with adhesive. The canals were filled with CH, and the teeth were placed in individual vials containing 10 mL of distilled water, which had its pH measured after 7, 14, 21 and 28 days (pH1). The root canals were then divided into five groups and filled with Resilon/Real Seal (G1) or gutta-percha and Endofill (G2), Sealapex (G3), AH Plus (G4) or MTA Fillapex (G5) sealers. After storage for 7 days, the root canals were retreated. The CH was again inserted into the canals, and the teeth were placed in new vials containing 10 mL of distilled water. The pH was again measured at 7, 14, 21 and 28 days (pH2). The initial and final pH readings (pH1 and pH2) were compared by ANOVA, ANOVA2 and Tukey's tests (P < 0.05). Results The pH1 and pH2 measurements increased with time. The measurements obtained after retreatment were significantly higher than those obtained before root canal filling. Conclusions Hydroxyl ions are able to diffuse through dentinal tubules. Regardless of the filling material, it was possible to re-establish the permeability of dentine to ionic diffusion after retreatment. Time had a positive influence on ionic diffusion.