Comparison of the effectiveness of different concentrations of etidronic acid in removing the smear layer from root canals

Aim This study aimed to evaluate the efficiency of 5%, 9%, and 18% concentrations of etidronic acid and EDTA in removing the smear layer from the root canal to determine the ideal concentration of etidronic acid. Materials and Methods In our study, 75 single root and canal mandibular premolar teeth, which were extracted for periodontal or orthodontic reasons, were used. To standardize the canal lengths of all teeth, they were measured 15 mm from the apical foramen and decorated under water cooling with the help of a diamond bur. The root canals were manually enlarged to the working length with ISO #20 K- and H-type files. Then, preparation was completed using Reciproc R40 (VDW, Munich, Germany) NiTi files with an apical diameter of #40. The teeth were randomly divided into 5 groups (n = 15) (Group 1: 2.5% NaOCl + 17% EDTA; Group 2: 2.5% NaOCl + 5% HEDP; Group 3: 2.5% NaOCl + 9% HEDP; Group 4: 2.5% NaOCl + 18% HEDP; and Group 5 [control group]: 2.5% NaOCl + deionized water). Irrigation was completed with 15 ml and 5 ml of the standard solution volume during instrumentation. The teeth were finally irrigated with 5 ml of distilled water and dried with paper cones. With the help of a thin flame-tipped bur and aerator, grooves parallel to the long axis were opened on the buccal and lingual surfaces of the specimens, and the roots were divided into two equal parts. Coronal, middle, and apical images of the teeth were taken under x2000 magnification using a scanning electron microscope, and the presence of a smear layer was scored by two different observers. The Kruskal–Wallis H test was used for the statistical measurement of the obtained images. In the case of significant differences resulting from comparisons with more than two groups, the groups with significant differences between them were determined using post hoc tests (Mann–Whitney U test with Bonferroni correction). Results There was a statistically significant difference between irrigation solutions in terms of smear layer removal efficiency (p < 0.05). EDTA, 5% HEDP, 9% HEDP, and 18% HEDP were significantly more efficient than the control (p < 0.05). However, there was no significant difference between EDTA, 5% HEDP, 9% HEDP, and 18% HEDP (p > 0.05). There was a statistically significant difference between regions, as smear layer removal efficiency was significantly higher in the coronal and middle regions than in the apical region for all irrigation solutions (p < 0.05). Conclusion There was no difference between 5%, 9%, and 18% etidronic acid and 17% EDTA in terms of the effectiveness of smear layer removal. Further research on the use of etidronic acid as a root canal irrigation solution is needed. Keywords: Continuous chelation, EDTA, HEDP, scanning electron microscope, smear layer removal