Comparative Evaluation of Irrigant Activation Systems for Smear Layer Removal in the Apical Third of Root Canals: A SEM Analysis

Abstract

Background: The smear layer is a surface film of debris that remains on dentin or other tooth surfaces, such as enamel or cementum, after instrumentation with either rotary instruments or endodontic files. Sodium hypochlorite is the gold standard in endodontic irrigation, but it does not remove the inorganic components of the smear layer. Twin Kleen, a mild chelating agent based on 1-Hydroxyethylidene-1,1-Diphosphonic Acid (HEBP), enhances debris removal and prevents smear layer formation, allowing for simplified irrigation as a single solution. Researchers have developed activation devices to improve the delivery of irrigant to the working length. Aim: The study aimed to evaluate and compare the efficacy of different irrigation activation systems: manual, sonic, ultrasonic and Laser activation on the removal of smear layer from the apical third of instrumented root canal using Scanning electron microscope. Method: Thirty-two single-rooted teeth were prepared with the help of Neo endo S files. Copious irrigation was done using twinkleen (HEBP+3% NaOCl) in between instrumentation. All the specimens were randomly divided into 4 equal groups according to the method of activation used: group 1 (n = 8) manual agitation, group 2 (n = 8) sonic activation, group 3 (n = 8) ultrasonic activation, and group 4 (n = 8) laser activation. Samples were then sectioned and sent for SEM examination. In all groups, canals were rinsed with saline to rinse off the residual irrigants and dried with paper points. One-way ANOVA test followed by Sceffe’s Post hoc test was used to compare the significant difference between the 4 groups. Results: All four groups removed the smear layer, and the laser group showed the best smear layer removing capability compared to other groups, but this was significant only with respect to group (MDA) and group 2 (sonic activation) (p<0.05). The study mainly showed that sonic activation efficiently removed the smear layer in the apical third of the root canal. Groups I (MDA) and III (Ultrasonic) had more residual smear layer on the canal walls than sonic activation, but this was only significant with respect to the MDA group. A probable explanation for irrigant activation providing cleaner canals is that higher frequency results in higher flow velocity, which aids in the efficient removal of debris. Conclusions: Within the limitations of the study, all the activation systems were able to remove the smear layer from the apical third of the root canal, with laser showing the best result, followed by sonic, ultrasonic and manual dynamic agitation.