Purpose: The aim of this study was to gain information about the antimicrobial effect of Er:YAG laser irradiation on bacteria in dental root canals in vitro. Materials and Methods: The coronal section of 20 extracted human teeth was removed to enable better access to the canals. All canals were cleaned and enlarged by the conventional method using K-files size 10 to 40. Apical foramens were sealed with fissure sealant. Sterilization of canals followed at 120°C for 15 min. Then 10 canals were inoculated with Streptococcus aureus bacteria and 10 others with E. coli bacteria. All teeth were kept for 2 h at 37°C. After 2 h all canals except the controls were sterilized with the laser set at 15 Hz, 60 mJ energy per pulse for 12 s. The procedure was repeated four times. Material was taken from each canal, incubated for 24 h, and the results analyzed. Results: A significant reduction of bacterial content was found in the laser-sterilized canals. Conclusion: Er:YAG laser can be used for sterilization of root canals.

Keywords: Er:YAG laser, bacteria, root canal