Diode laser radiation and its bactericidal effect in root canal wall dentin

Objectives: The aim of this study was to investigate the antibacterial effect of a diode laser in deep root canal dentin, Background Data: The microbial colonization of root canal dentin can lead to failures in conventional endodontic treatment if an inadequate bacterial reduction only is achieved through canal treatment and chemical disinfection. Methods: 100 mu m, 300 mu m and 500 mu m bovine dentin slices obtained by longitudinal sections were sterilized and inoculated on one side with an Enterococcus faecalis suspension. Laser radiation was performed on the opposite side with the diode laser (810 nm) at a setting of 3 W in continuous mode (CW). Radiation was performed using a 400-mu m tapered fiber tip at an angle of approximately 5 degrees to the surface over a period of 30 seconds. The output power at the distal end of the tip was 0.6 W. The bacteria were then eluted through vibration and cultured on blood agar plates. The colony count reflected the antibacterial effect of laser radiation as a function of the layer thickness. Results: A mean bacterial reduction of 74% was achieved even with a 500-mu m thick slice. Conclusion: This investigation indicates that the diode laser radiation reduces the number of bacteria in deep layers of infected root canal wall dentin.