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Antibacterial Effects of Nd:Yag Laser in Root Canal Samples: In Vitro Study

The aim of this study was to investigate the antibacterial effect of an Nd:YAG laser in root canal samples using suspension of Enterococcus faecalis and Staphylococcus aureus. Twenty-two single-rooted teeth were instrumented, sterilized and inoculated with bacterial suspension concentration of 106 CFU/ml in brain-heart broth. The samples were irradiated by Nd:YAG laser ; one half with power setting of 3.5 W and the other half with 2.5 W frequency of 40 Hz in five cycles with 15 s of lasing and with 15 s of pause for cooling. After irradiation the samples were placed in vials with broth, and the number of CFU/ml was determined after one and two weeks. Laser beams of 3.5 W power settings sterilized only three samples in the first week. In one of them bacteria, predominantly Enterococcus faecalis, grew in the second week. In another sample pure culture of Enterococcus faecalis grew. Irradiation by the Nd:YAG laser with 2.5 W did not sterilize any sample. Nd:YAG laser with parameters used in this study did not significantly reduce the number of bacteria in root canal specimens.