title: Inhibitory effects of a super pulsed carbon dioxide laser at low energy density on periodontopathic bacteria and lipopolysaccharide in vitro.
abstract: OBJECTIVE
  Previous studies have described the effect of irradiation by a carbon dioxide (CO2) laser at high energy density on oral bacteria, and various side-effects have also been observed. However, no published studies have examined the effect of irradiation by a CO2 laser at low energy density on oral bacteria. The purpose of this study was to investigate the effects of super pulsed CO2 laser irradiation on periodontopathic bacteria and lipopolysaccharide (LPS).
  
  
  METHODS
  Bacterial suspensions of two species of periodontopathic bacteria received laser irradiation at energy densities of 0-12.5 J/cm2. The suspensions were then spread over agar plates and incubated anaerobically. The bactericidal effects were evaluated based on colony formation. Samples of LPS were laser-irradiated at energy densities of 0-12.5 J/cm2. The biological activity was measured, and LPS was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE).
  
  
  RESULTS
  The irradiation at low energy densities of 7.5 and 12.5 J/cm2 killed more than 99.9 and 99.999% of Porphyromonas gingivalis and more than 99% of Actinobacillus actinomycetemcomitans was sterilized by the irradiation at 7.5 J/cm2. LPS biological activity was significantly decreased by laser irradiation at energy densities of more than 7.5 J/cm2 (p < 0.05), and the components of LPS analyzed by SDS-PAGE was diminished non-specifically.
  
  
  CONCLUSIONS
  The results indicate that CO2 laser irradiation at low power is capable of bactericidal effect on periodontopathic bacteria and decreasing LPS activity.
authors.affiliation: Department of Periodontology, Dental Research Center, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Kojima
authors.forename: Koichi
authors.initials: K
authors.lastname: Shimada
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Iwasaki
authors.forename: Koichi
authors.initials: K
authors.lastname: Ito
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000254:growth & development / Q000528:radiation effects*; D000693:Anaerobiosis; D002245:Carbon Dioxide; D015169:Colony Count, Microbial; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D006801:Humans; D007834:Lasers; D008070:Lipopolysaccharides / Q000032:analysis / Q000528:radiation effects*; D016966:Porphyromonas gingivalis / Q000254:growth & development / Q000528:radiation effects*
chemical_list: D008070:Lipopolysaccharides; D002245:Carbon Dioxide