Comparative Study about the Removal of Smear Layer by Three Types of Laser Devices

Abstract

Objective: The aim of this study was to analyze the effectiveness of three types of laser, argon, Nd:YAG, and Er:YAG, to remove the smear layer from the prepared root canal walls in vitro. Methods: After cleaning and shaping by step-back preparation, 32 human extracted maxillary molar teeth were divided randomly into four groups. Root canals in group 1 (Gl) were unlased and were irrigated by 17% EDTA. In group (G2), root canals were irradiated by argon laser at the parameters of 1 W, 50 mj, and 5 Hz. In group 3 (G3) root canals received Nd:YAG laser irradiation at 2 W, 200 mj and 20 Hz. Teeth in group 4 (G4) were irradiated by Er:YAG laser at the following parameters: 1 W, 100 mj and 10 Hz. Then these teeth were bisected longitudinally, observed using SEM, and evaluated. Results: The middle third of the teeth from Gl showed clean wall surfaces with open dentina! tubules. In G2, at the middle third, the smear layer was free and vaporized pulpal tissue remnants were observed. In G3, most of the specimens showed very clean walls with the smear layer evaporated, melted, fused, and recrystallized in both the middle and apical thirds. The walls of G4 revealed the evaporated smear layer and open dentina! tubules in the middle and apical thirds. Statistical analysis showed significant differences between Gl and G2, Gl and G3, and Gl and G4. Conclusions: These results show that the argon laser and Nd:Y AG laser are useful to remove the smear layer and that the Er: YAG laser irradiation is the most effective to remove the smear layer on root canal walls.

The Effect of Er:YAG Laser on Entroccocus faecalis Bacterium in the Pulpectomy of Anterior Primary Teeth

“…[46][47][48] Power is one of those parameters. According to the study by Takeda et al the power of 1/2 W is adequate for clearing the smear layer, 11,49,50 moreover, the power of 1/2 W is adequate for disinfecting the canal. 51 Accordingly, in the present study, because the primary teeth are chosen and there is structural difference between primary and permanent teeth, the least power (1 W) used in other studies is chosen and examined.…”

“…48 Water or air sprays are some of the efficient factors in preventing thermal damage. [49][50][51] The study by Theodoro et al showed that applying laser for 30 seconds with water spray can decrease temperature (-2.2 ± 2.5°C). 52 It should be taken into consideration that using too much water or air cooling results in energy absorption and decreased ablation effect of laser.…”

Dental Lasers and Application Fields in Endodontics

“…Takeda et al (52) showed that irrigation with 17% EDTA, 6% phosphoric acid and 6% citric acid was not able to remove the entire smear from the root-canal system. Acidic solutions cause erosion and widening of tubules.…”

Scanning Electron Microscope Evaluation of Smear Layer Removal at the Coronal, Middle, and Apical Third of Root Canals using Er,Cr:YSGG Laser: An in vitro Study

“…6 The erbium, chromium: Yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser is approved by the Food and Drug Administration for cleaning, shaping, and enlarging the root canal. 7 Previous studies have tested the ability and effects of this laser on root canal walls and have indicated that the Er,Cr:YSGG laser is a suitable instrument for the removal of smear layer in root canals. Furthermore, George et al 8 investigated the ability of Er,Cr:YSGG lasers equipped with conical firing tips to remove smear layer from apical third of the root canal and showed a laser activation of EDTA and better performance of conical fiber tips for improving the action of EDTA in removing smear layer.…”