Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 15 3 2018 06 13 178 186 EN Zahra Bahrololoomi Associate Professor, Department of Pediatric Dentistry, School of Dentistry, Shahid Sadoughi University of Medical Sciences, Yazd, Iran Reza Birang Professor, Department of Periodontics, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran Nasim Chiniforush Researcher, PhD of Laser Dentistry, Laser Research Center of Dentistry (LRCD), Dentistry Research Institute, Tehran University of Medical Sciences, Tehran, Iran Hazhir Yousefshahi Dentistry Student, School of Dentistry, Isfahan University of Medical Sciences, Isfahan, Iran Elnaz Foroughi Assistant Professor, Department of Pediatric Dentistry, School of Dentistry, Arak University of Medical Sciences, Arak, Iran 2018 06 13 2018 06 13 Objectives: Successful root treatment depends on elimination of microorganisms from the root canal. Considering incomplete removal of bacteria from the canal by usual methods, lasers have been suggested as a new modality. Despite their anti-bacterial properties, lasers can cause thermal changes. This study assessed the thermal changes of root surface in pulpectomy of primary teeth following the use of Er:YAG laser. Materials and Methods: Sixty primary anterior teeth were collected and prepared by K-file up to number 50. Then, they were randomly divided into two groups and were irradiated with Er:YAG laser. The first group was irradiated with 1 W laser and the second group with 1.5 W laser. The laser irradiation time was two 10-second cycles with a 2-second interval in both groups. Thermal changes were measured by a thermometer in the apical and coronal areas per second. The results were analyzed by repeated measures ANOVA considering the laser power as between-subject variable. Results: There was a temperature increase in the coronal and apical areas in use of 1 W power. There was a temperature rise in the coronal and apical areas in use of 1.5 W power. The temperature rise in the apical third was more than that in the coronal third; also, the average temperature rise was more in use of 1.5 W power than 1 W power. Conclusions: As the average temperature increase was not more than 7°C in any group, this type of laser seems to be suitable for root treatment of primary anterior teeth. https://fid.tums.ac.ir/index.php/fid/article/view/2614 https://fid.tums.ac.ir/index.php/fid/article/download/2614/1007