Removal of smear layer by two endodontic irrigation solutions and erbium: yttrium, aluminum, garnet [Er:YAG] laser: a scanning electron microscope [SEM] study

The purpose of the present study was to determine the effect of 17% Ethylene, di-amine, tetra-acetic acid [EDTA], 6% phosphoric acid and Erbium: Yttrium, Aluminum, Garnet [Er:YAG] Laser in removing the smear layer by scanning electron microscopy. In this study, 80 single-rooted human teeth were selected. Instrumentation was done by use of hand files and step-back technique up to file #40 at apical and file #80 at coronal area. During instrumentation, 1ml of 5.25% sodium hypochlorite [NaOCl] was used as irrigation between each file. The teeth were randomly divided into four groups with different methods of smear removal.17% Ethylene, di-amine, tetra-acetic acid was used in group 1, 6% Phosphoric acid in group 2, Erbium: Yttrium, Aluminum, Garnet laser in group 3, and no intervention in group 4 [as control]. Roots were then longitudinally sectioned and prepared for scanning electron micrograph in cervical, middle and apical areas. Data were analyzed by Kruskal-Walis, Mann-Whitney, Friedman and Wilcoxson tests [P<0.05]. The results showed a significant difference in smear layer removal between three methods in favor of the EDTA [P<0.001] and Phosphoric groups [P<0.001] with no significant difference between them [P=0.49]. Although Er:YAG laser showed some limited ability to remove the smear layer, the effectiveness was not significantly different from the control group [P=0.157]. Based on the findings of this study, EDTA and Phosphoric acid were effective methods to remove smear layer from the root canal walls but Er:YAG laser showed less efficacy compared to the other experimental groups

Graphite application and different powers of neodymium-doped yttrium aluminium garnet [Nd:YAG] laser on dentin surface changes: a scanning electron microscopy study

Various methods have been used for the treatment of dentine hypersensitivity such as dentifrices, sealants and different types of lasers. The aim of this study was to evaluate the effect of Neodimium:Yttrium-Aluminium-Garnet [Nd:YAG] laser in association with graphite on the dentin morphologic changes. In this experimental in vitro study, 16 freshly extracted third molars were selected. 5 specimens with the dimensions of 2×2×1 mm from root trunk were prepared. Specimens were randomly divided into five groups: group 1 [control, no laser irradiation]. Group 2, 3 irradiated by Nd:YAG laser 0.5 and 1W, output power respectively. Group 4, 5 smeared with graphite and then irradiated by Nd: YAG laser 0.5 and 1W output power. Samples were prepared for scanning electron microscopy. Number and diameter of dentinal tubules were determined in different groups and analyzed with the Kruskal-wallis and Mann-Whitney tests [SPSS 16]. The number of tubules had significant difference between all groups [P<0.001], except group 1 in comparison with group 2 [P> 0.05], and group 3 in comparison with group 4 [P> 0.05]. Micro-cracks and rupture of melted dentin materials were seen in group 4 and 5. According to the findings of this study, smearing with graphite on dentin surface increase the absorption of Nd:YAG laser energy and reduced the diameter and number of open dentinal tubules