Comparative Evaluation of Effect of Irrigation Solutions with Various Exposure Time on Microhardness of Root Canal Dentin (In Vitro Study)

Background: It is important to test the effect of the irrigating solutions on dentin, as they may come in contact during irrigation procedures. These irrigants cause alterations on dentin and enamel surfaces and affect their interactions with materials used for obturation and coronal restorations. The aim was to study the microhardness of root canal dentin after irrigation with different irrigant solutions for different periods. Materials and Methods: Twenty five newly extracted non carious human permanent incisors were sectioned at cementoenamel junction and splitted longitudinally then divided into five groups; Gr1 (control) distilled water, G2: 5.25% sodium hypochlorite (NaOCl) for (10 min) then 17% EDTA for (1 min), G3: 5.25% sodium hypochlorite (NaOCl) for (10 min) then 17% EDTA for (5 min), G4: 5.25% sodium hypochlorite(NaOCl) for (20 min) then 17% EDTA for (1 min) and G5: 5.25% sodium hypochlorite(NaOCl) for (20 min) then 17% EDTA for (5 min). Vickers microhardness was evaluated.  Results: Data were analyzed using one-way ANOVA and paired t-test. The results indicated that all treatment time with 5.25% NaOCl and 17% EDTA decreased dentin microhardness significantly compared to distilled water (control). There were significant differences (P<0.001) between the tested groups with increasing time of exposure of irrigation solutions. Treatment with distilled water (control) showed significantly the highest microhardness value, while 5.25% sodium hypochlorite for 20 minute followed by 5 minutes (G5) with 17% EDTA showed significantly the least microhardness value followed by G4, G3 and G2. Conclusions :Increasing irrigation time with both 5.25% sodium hypochlorite and 17% EDTA decreased dentin microhardness.