EFFECT OF ENDODONTIC IRRIGATION SOLUTIONS ON MICROHARDNESS OF ROOT-CANAL DENTIN

Objectives: This study was undertaken to evaluate the effect of severa l endodontic irrigation solutions on the microhardness of root canal d entine. Methods: Eighteen freshly extracted maxillary incisors were us ed in this experiment. The crowns of teeth were sectioned at the cemen to-enamel junction. The root canals were instrumented to an apical siz e #50 file, and irrigated with saline solution. The prepared roots wer e divided equally into two groups each of nine roots. Each root was se ctioned transversely into cervical, middle and apical segments. The th ree sections of each root were separately mounted in a metal chuck wit h acrylic resin. The coronal dentine surfaces of the root segments wer e polished. The microhardness of the dentine was measured for the purp oses of control data at 500 mu m and 1 mm from the pulpo-dentinal inte rface. The canal portions in the root segments included in the first g roup were irrigated with 3% H2O2 and 5% NaOCl solutions used alternati vely, while 17% EDTA solution was the irrigation used in the second gr oup. One millilitre of each solution/segment was applied for 60 s expo sure time. After irrigation, dentine microhardness was re-assessed and compared with the control values obtained before the irrigation treat ment. Data were statistically analysed using ANOVA and Scheffe's test. Results: The results showed that, irrigation with either H2O2/NaOCl o r EDTA decreased the microhardness value of root dentine. Irrigation w ith EDTA gave more reduction of dentine hardness compared to H2O2/NaOC l 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 denti ne. (C) 1998 Elsevier Science Ltd. All rights reserved.