Influence of dentin on the hydrogen ions release in calcium hydroxide paste associated with chlorhexidine

Objective: To measure the pH of a Ca(OH)2 paste, pure or associated with 0.4% of chlorhexidine digluconate (CHX), in 24h, 7 and 14 days.Methods: Twenty bovine roots were standardized and a root perforation was performed 5 mm from the cervical area, opening an access to the root canal. After external sealing, the canals were filled with a Ca(OH)2 paste, pure or associated with CHX 0.4% (n = 10). The opening was sealed and the roots were immediately immersed in distilled water. The pH was measured in the following times: 24h, 7 and 14 days. Similar conditions were performed using polyethylene tubes, which formed four groups: G1 – Ca(OH)2 in dentin; G2 – Ca(OH)2 + CHX in dentin; G3 – Ca(OH)2 in polyethylene tubes; G4 – Ca(OH)2 + CHX in polyethylene tubes. Results: Except for G4, the pH decreased over time. In the first 24h, G3 presented the higher pHvalue, and there were no differences between G1 and G3, and G3 and G4 (p > 0.05). In 7 days the pH was higher for G1, and no differences were found only between G3 and G4 (p > 0.05). In 14 days the pH was higher for G4, and there were significant differences between G1 and G4, and G2 and G3 (p > 0.05). Conclusion: There was a decrease of pH over time in all groups except for the association Ca(OH)2 + CHX in polyethylene tubes. Dentin presented influence on the final pH of the Ca(OH)2 paste.