Comparison of the smear layer removal efficacy of various irrigation solutions with an ultrasonic activation system

Ensuring complete disinfection of the root canal system is one of the main goals of endodontic treatment. During the shaping of the root canal system, an amorphous, irregular, organic and inorganic-containing layer is formed, which is called smear layer. In addition to reducing the bonding of obturation materials to root dentin, the smear layer provides a nutrient medium for microorganisms, increases microleakage and reduces the effect of irrigation solutions on dentin. By using Scanning Electron Microscopy (SEM), this study aims to be compared the smear layer removal activity of 17% Ethylene Diamine Tetra Acetic Acid (EDTA), 10% Glycolic acid (GA) and 18% Etidronic acid (EA), which are used as a final wash solution and activated by ultrasonics. Material and Method In this study, 80 human mandibular premolar teeth extracted for orthodontic/periodontal reasons were used. The teeth were kept in distilled water at room temperature until the time of the study. The endodontic enterance cavity of each tooth was opened and in order to obtain a standard root length, the crowns were cut with diamond burs with a root length of 15 mm from the enamel-cement margin. The working length of the remaining roots was determined to be 1 mm shorter after the tip of the number 15 K-file appeared from the apical foramen. After the working lengths of the teeth were determined, canal widening operations were performed with the Reciproc R25 rotary tool file suitable for reciprocating motion with the help of an endodontic motor. The samples were randomly divided into 4 groups, one of which was the control group (n=20). In each group, different final irrigation solutions were used with the passive ultrasonic activation (PUI) system. Group 1: %2,5 NaOCl +%17 EDTA+PUI Group 2: %2,5 NaOCl +%10 GA+PUI Group 3: %2,5 NaOCl +%18 EA+PUI Group 4: %2,5 NaOCl+distilled water +PUI (control group) After all these procedures, the teeth were divided into two with flame-tipped diamond burs in the buccolingual direction. During the procedure, care was taken not to touch the root canal cavity. From the samples; SEM images were taken under x2000 magnification with the central part of the coronal, middle and apical tripartite regions, and the presence of the smear layer was scored observationally by the the two different observers. Result Compliance with normal distribution was evaluated with the Kolmogorov Smirnov test. The Kruskal Wallis H test was used to compare the data that were not normally distributed according to groups of three or more, and multiple comparisons were examined with the Dunn test. Significance level was taken as p<0.05. Interobserver agreement was calculated using Cohen's kappa statistics. Kappa test results showed that there was no statistically significant difference between the assessors (kappa value = 0.866). No statistically meaningful difference was observed between the EDTA, GA and EA groups (p>0.05). In the evaluation made within each group, there was no meaningful difference in the coronal and middle third regions of the root canal in the EDTA and GA groups (p>0.05), but a statistically significant difference was found in the apical region (p<0.05). In the EA group, there was a meaningful difference between only the coronal and apical triples (p<0.05). Conclusions There is no significant difference between the smear layer removal efficiency of EDTA, GA and EA irrigation solutions. None of the irrigation solutions used could completely remove the smear layer from the root canals.