Effect of endodontic irrigation solutions on microhardness of root canal dentine

Purpose: This study was undertaken to evaluate the effect of several endodontic irrigation solutions on the microhardness of root canal dentine. Methods: Eighteen freshly extracted maxillary incisors were used in this experiment. The crowns of teeth were sectioned at the cemento–enamel junction. The root canals were instrumented to an apical size #50 file, and irrigated with saline solution. The prepared roots were divided equally into two groups each of nine roots. Each root was sectioned transversely into cervical, middle and apical segments. The three sections of each root were separately mounted in a metal chuck with acrylic resin. The coronal dentine surfaces of the root segments were polished. The microhardness of the dentine was measured for the purposes of control data at 500 μm and 1 mm from the pulpo–dentinal interface. The canal portions in the root segments included in the first group were irrigated with 3% H2O2 and 5% NaOCl solutions used alternatively, while 17% EDTA solution was the irrigation used in the second group. One millilitre of each solution/segment was applied for 60 s exposure time. After irrigation, dentine microhardness was re-assessed and compared with the control values obtained before the irrigation treatment. Data were statistically analysed using ANOVA and Scheffeʹs test. Results: The results showed that, irrigation with either H2O2/NaOCl or EDTA decreased the microhardness value of root dentine. Irrigation with EDTA gave more reduction of dentine hardness compared to H2O2/NaOCl irrigation. The reduction of KHN of dentine following the irrigation treatment was statistically significant (p<0.05) at both levels of hardness measurement. Conclusions: Both H2O2/NaOCl and EDTA irrigating solutions significantly reduced the microhardness of root canal dentine.