Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 15 1 2018 01 06 30 40 EN Elham Khoshbin Assistant Professor, Department of Endodontics, School of Dentistry, Hamadan University of Medical Sciences, Hamadan, Iran Zakiyeh Donyavi Assistant Professor, Department of Endodontics, School of Dentistry, Hamadan University of Medical Sciences, Hamadan, Iran Erfan Abbasi Atibeh Assistant Professor, Department of Periodontics, School of Dentistry, Alborz University of Medical Sciences, Karaj, Iran Shahin kasraei Professor, Department of Restorative Dentistry, School of Dentistry, Shahid Beheshti University of Medical Sciences, Tehran, Iran Rasoul Yousefimashouf Associate Professor, Department of Microbiology, Hamadan University of Medical Sciences, Hamadan, Iran Ghodratollah Roshanaei Associate Professor, Modeling of Noncommunicable Diseases Research Center, Department of Biostatistics and Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran Faranak Amani Assistant Professor, Department of Endodontics, School of Dentistry, Alborz University of Medical Sciences, Karaj, Iran 2017 06 13 2017 08 22 Objectives: Laser irradiation, as an adjunct to root canal preparation, may increase the success rate of endodontic treatments. This study aimed to assess the effect of neodymium-doped yttrium aluminum garnet (Nd:YAG) and diode lasers on the apical seal of the root canals filled with AH Plus® and mineral trioxide aggregate (MTA)-based sealers. Materials and Methods: This in-vitro experimental study was conducted on 96 single-rooted, single-canal extracted human teeth with closed apices. The root canals were prepared by using ProTaper® rotary instruments and were randomly divided into six groups (n=16): 940-nm diode laser and AH Plus® sealer (group 1), Nd:YAG laser and AH Plus® sealer (group 2), AH Plus® sealer (group 3), 940-nm diode laser and MTA-based sealer (group 4), Nd:YAG laser and MTA-based sealer (group 5), MTA-based sealer (group 6), as well as positive and negative control groups. A bacterial leakage model was used for microleakage assessment. Qualitative assessment was done by using a scanning electron microscope (SEM). Data were analyzed by two-way analysis of variance (ANOVA) at the significance level of 0.05. Results: There were statistically significant differences between the experimental and control groups (P=0.002). The laser-treated groups showed a lower apical microleakage compared to the non-laser-treated groups, although the difference was not statistically significant (P>0.05). No significant differences were noted between the two lasers in terms of the apical microleakage, irrespective of the type of sealer (P>0.05). Conclusions: Laser irradiation, as an adjunct to root canal preparation, has no significant effect on the level of apical microleakage. https://fid.tums.ac.ir/index.php/fid/article/view/1958 https://fid.tums.ac.ir/index.php/fid/article/download/1958/988