Résumé
Decalcification and its effect on microhardness of root canal dentin by an aqueous solution of 17% EDTA at different time intervals were studied.Single rooted forty extracted human premolar teeth after adequate processing and embedded with acrylic resin were randomly divided into 8 groups based on different time intervals. Each sample group was assessed for Ca<sup>2+</sup> release into the test solution by Atomic Absorption Spectrophotometer, respectively and then were subjected for microhardness testing.17% EDTA and 0.9% Saline, test solutions were used; EDTA was adjusted to 7.5 pH. Data analysis was done by One Way analysis of variance (ANOVA) and the comparison of means was done by using Tukey’s multiple comparison tests. The decalcifying activity of 17% EDTA solution was time dependent and increased immersion time showing very high significant influence on the amount of calcium extracted (<strong>F=154.304, p). The reduction in microhardness for 17% EDTA solution was time dependent and increased immersion time showing very high significant decrease in the microhardness among the different time intervals tested (<strong>F=249.925, p < 0.0005</strong>).Effect of 17 % EDTA solution as root canal irrigant is time dependent as evidenced by dentin microhardness reduction.