Evaluation of root canal smear layer removal by two types of lasers: A scanning electron microscopy study

Abstract

Abstract Objective: This study was to compare the effects of Erbium: Yttrium-Aluminium-Garnet (Er: YAG), and Neodimium: Yttrium-Aluminium-Garnet (Nd: YAG) lasers on removing the smear layer using scanning electron microscopy. Background: Removing Smear layer and exposure of dentinal tubules facilitate a tight-fitting root canal filling, which is necessary for a successful endodontic treatment and one of the proposed methods for removing the smear layer is the use of lasers. Materials and Methods: In this experimental study, 55 human single-rooted teeth were examined. Instrumentation was done using the step-back technique with hand files up to file #40 at the apical area and file #80 at the coronal area. The samples were divided into three groups: Samples irradiated by the Er: YAG laser (1 W, 10 Hz, 130.7 J/cm2 ) in Group 1 (n=25), the Nd: YAG laser (2 W, 15 Hz, 188.25 J/cm2 ) in Group 2 (n=25) and samples irrigated by 5.25% NaOCl as the control in Group 3 (n=5). Next, roots were bisected longitudinally and prepared for scanning electron microscopy. Data were analyzed using the Kruskal-Wallis, Mann-Whitney, Friedman and Wilcoxon tests (P<0.05). Results: The Er: YAG laser can remove more of the smear layer from the root canal wall than the Nd: YAG laser (P=0.000). Comparisons between three regions showed that both of the lasers proved less efficient in apical parts of the root canal. Conclusion: Based on the findings of the present study, irradiation by the Er: YAG laser was more effective in smear layer removal than the Nd: YAG laser.