Efficient Removal of the Smear Layer Using Er:YAG Laser

Objectives: The aim of this study was to examine the effects of Er:YAG laser irradiation equipped with a cone-shaped fiber tip (inner-diameter: 300 µm) on root canal walls of extracted teeth with or without EDTA pre-treatment. Methods: A total of 15 human single-rooted teeth extracted for periodontal reasons were used. After root canal preparation up to an apical size of #40 file, the teeth were divided into three groups: (1) teeth treated with chemical irrigation (15% EDTA plus 5% NaOCl); (2) teeth irradiated with Er:YAG laser (laser parameters were set at 30 mJ and 40 mJ, 20 pps, and draw-up speed of 1 mm/sec); (3) teeth irradiated with Er:YAG after chemical irrigation. Subsequently, the samples were split longitudinally and prepared for examination by scanning electron microscopy and laser microscopy. Results: SEM observation showed the removal of smear layer and open dentinal tubules in all three groups. The root canal walls irradiated with Er;YAG laser were free of debris and smear layer, without cracks and carbonization. The size of open tubules by laser irradiation was smaller than that by chemical irrigation. In addition, the surface of the ablated area by laser after chemical irrigation was smoother than that by laser alone. Laser microscopic analysis revealed that the depth and volume of lased regions increased almost to double by the combined use of chemical irrigation and Er:YAG laser irradiation compared to laser alone. Conclusions: These results showed that Er:YAG laser with a cone-shaped tip is a suitable tool for the removal of smear layer in root canals. Moreover, it was suggested that Er:YAG laser irradiation in combination with chemical irrigation is efficient for cleaning the prepared canal wall.