Bactericidal Effect of Er: YAG Laser on Periodontopathic Bacteria

The application of Erbium YAG laser has been investigated recently in the dental field. The laser irradiation of Er: YAG does less damage to hard and soft tissues adjacent to the target site than that of CO2 or Nd: YAG. Our previous experiments showed that this laser was able to remove subgingival calculus effectively at the energy density of 7.1-10.6J/cm2 with water irrigation in vitro. The purpose of this study was to evaluate the bactericidal effect on periodontopathic bacteria at the energy density suitable for scaling. Porphyromonas gingivalis or Actinobacillus actinomycetemcomitans, which had been already spread over the surface of Tripticase-Soy Blood (TS) or Brain Heart Infusion (BHI) agar plates, was exposed to single pulse laser irradiation at the energy density of 0.04-2.6J/cm2 and the growth of bacterial colonies was examined after anaerobic culture. One P. gingivalis colony was also exposed to single pulse laser irradiation at the energy density of 1.8, 3.5, 7.1, 10.6J/cm2. Then the irradiated colonies were subcultured anaerobically and colony forming unit was counted . In results, the growth of P. gingivalis and A. actinomycetemcomitans was clearly inhibited at the irradiated site at the energy density of 0.3J/cm2 and higher. In the case of single pulse laser irradiation to one P. gingivalis colony, the colony forming unit at the energy density of 7.1, 10.6J/cm2 was significantly less than control. These results suggest that Er: YAG laser has a high potential of bactericidal effect on periodontopathic bacteria at the energy density suitable for scaling.