Abstract
Abstract : The aim of this study was to observe the ultrastructures of root-end cavity walls prepared with Er:YAG laser, and to evaluate the temperature changes occurring on the root surface during irradiation. Human single-rooted teeth were used. After the crown was removed, the root canal was enlarged mechanically up to a size of #60. A 3-mm root-end resection was made perpendicular to the long axis of the root with a diamond bur at high speed under a continuous water spray. A root-end cavity 3 mm deep from the resected surface was prepared using Er:YAG laser with a flat-end tip (group A), Er:YAG laser with a cone-shaped tip following a flat-end tip (group B), and an ultrasonic device with a retrotip (group C). Laser energy was set at 80 mJ, and the repetition rate was 20 pps, with water and air cooling. For the thermographical observation, root canals were filled with a lateral condensation method.
The samples were sectioned longitudinally and examined using a scanning electron microscope. Group A presented a partially ablated dentin surface of the cavity wall, with a smear layer in part. Group B showed a totally ablated cavity surface with characteristic ring-like structures, without smear layer, with open dentinal tubules. The cavity wall of group C was mostly covered with a smear layer.
Temperature changes were recorded thermographically. The flat-end tip caused steep thermal increases of more than 10°C during lasing for 10 s. By contrast, the cone-shaped tip showed a temperature rise of approximately 2°C during lasing for 30 s.
These results suggest that the finishing preparation with Er:YAG laser irradiation might be feasible for the creation of a clean root-end cavity wall free of a smear layer.
