Purpose: In order to minimize thermal damage when Nd:YAG laser is applied in root canals and to improve the cleaning effects of laser irradiation, the Nd:YAG laser was combined with NaOCl or EDTA, and the morphological effects were investigated by scanning electron microscopy. Materials and Methods: Seventy-eight extracted human mandibular central and lateral incisors were used. After root canal enlargement, each root canal was filled with either 5% or 12% sodium hypochlorite or 7% or 14% EDTA. In the laser irradiation group, the pulsed Nd:YAG laser was applied at an output of 1 or 3 W and a frequency of 15 PPS for 5 s, and a 320-μm fiber was inserted into the root canal filled with the irrigant solution and moved up and down within a range of about 5 mm from the apical end. Ultrasonic cleaning was used as control. Each tooth was sectioned mesiodistally, and SEM observation was performed to statistically compare the cleaning effects of the laser irradiation and ultrasonic cleaning groups. Results: No statistically significant differences existed in the cleaning effects with respect to irrigant solution type and concentration. However, NaOCl tended to be superior to EDTA. In the laser irradiation group, cleaning effects were greatest in the apical area. When compared to the control, statistically significant cleaning effects were obtained by combining 3-W Nd:YAG laser and an irrigant solution. Conclusions: The results confirmed that 3-W Nd:YAG laser eliminated the smear layer without damaging the hard tissue inside the root canal.
Keywords: root canal irrigation, NaOCl, EDTA, concentration, Nd:YAG laser, SEM