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The purpose of this study was to evaluate the effect of 0.2% chlorhexidine gluconate on the microhardness and roughness of root canal dentin compared with widely used irrigation solutions. Ninety, mandibular, anterior teeth extracted for periodontal reasons were used. The crowns of the teeth were removed at the CEJ. The roots were separated longitudinally into two segments, embedded in acrylic resin, and polished. A total of 180 specimens were divided into 6 groups of 30 teeth at random according to the irrigation solution used: group 1: 5.25% NaOCl for 15 min; group 2: 2.5% NaOCl for 15 min; group 3: 3% H2O2 for 15 min; group 4: 17% EDTA for 15 min; group 5: 0.2% chlorhexidine gluconate for 15 min; and group 6: distilled water (control). Each group was then divided into 2 subgroups of 15 specimens: groups 1a, 2a, 3a, 4a, 5a, and 6a were submitted to Vickers microhardness indentation tests; groups 1b, 2b, 3b, 4b, 5b, and 6b were used for determination of the roughness of root dentin. The data were recorded as Vickers numbers and Ra, microm for roughness test. The results were analyzed statistically by using one-way ANOVA and Tukey tests. The results indicated that all the irrigation solutions except chlorhexidine significantly decreased microhardness of root canal dentin (p < 0.05); 3% H2O2 and 0.2% chlorhexidine gluconate had no effect on roughness of the root canal dentin (p > 0.05). Although there are many other factors for irrigation solution preference, according to the results of this study, 0.2% chlorhexidine gluconate seems to be an appropriate endodontic irrigation solutions because of its harmless effect on the microhardness and roughness of root canal dentin.

Use of resin-based restorative materials recently has become widely accepted for treatment of endodontically treated teeth. However, some solutions routinely used during endodontic treatment procedures may have an effect on bond strengths of adhesive materials to root canal dentin. The purpose of this in vitro study was to evaluate the effect of various medications on microtensile bond strength to root canal dentin. Fourteen extracted human single-rooted teeth were used. The crowns and the pulp tissues were removed. The root canals were then instrumented and widened to the same size. The teeth were randomly divided into seven groups of two teeth each. The root canal dentin walls of the roots were treated with 5% sodium hypochloride (NaOCI), 3% hydrogen peroxide (H2O2), the combination of H2O2 and NaOCl, or 0.2% chlorhexidine gluconate for 60 s; or calcium hydroxide or formocresol for 24 h. The teeth in control group were irrigated with water. The root canals were obturated using C&B Metabond. After 24 h of storage in distilled water, serial 1-mm-thick cross-sections were cut, and approximately 12 samples were obtained from each group. Microtensile bond strengths to root canal dentin were then measured by using an Instron machine. The data were recorded and expressed as MPa. The results indicated that NaOCI, H2O2, or a combination of NaOCl and H2O2 treatment decreased bond strength to root canal dentin significantly (p < 0.05). The teeth treated with chlorhexidine solution showed the highest bond strength values (p < 0.05). In conclusion, chlorhexidine is an appropriate irrigant solution for root canal treatment before adhesive post core applications.