title: Bactericidal effect of Nd:YAG and Er:YAG lasers in experimentally infected curved root canals.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the bactericidal efficacy of Nd:YAG and Er:YAG laser in the experimentally infected curved root canals.
  
  
  BACKGROUND
  Previous studies revealed that laser systems have a significant bactericidal effect in both human and bovine infected straight root canals.
  
  
  METHODS
  Sixty extracted single-rooted teeth with single root canals were selected and then instrumented with endodontic files to a size 60 (K-type file). The degree of root curvature was determined according to modified Schneider's method. Each of the specimens was incubated in a sterile centrifuge tube with 1 mL of the Enterococcus faecalis suspension at 37°C for 2 weeks under aerobic conditions. After laser irradiation at each of the two settings, 50 mJ, 10 pps (0.5 W) or 100 mJ, 10 pps (1.0 W), the number of E. faecalis in each root canal was examined.
  
  
  RESULTS
  In the straight root canals, the Er:YAG laser showed higher bactericidal effects by 6.4-10.8% than did the Nd:YAG laser. Conversely, the bactericidal effect of Er:YAG laser in the curved root canals was higher by 1.5-3.1% than was that with the Nd:YAG laser. The bactericidal effect of the Er:YAG laser in the curved root canal is significantly lower than that in the straight root canal (p < 0.05).
  
  
  CONCLUSIONS
  These results suggest that further development in the endodontic laser tip and technique is required to ensure its success in curved root canals sterilization.
authors.affiliation: Division of Clinical Cariology and Endodontology, Department of Oral Rehabilitation, School of Dentistry, Health Sciences University of Hokkaido, Ishikari-Tobetsu, Hokkaido, Japan. yasuda@hoku-iryo-u.ac.jp
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Yasuda
authors.forename: Toru
authors.initials: T
authors.lastname: Kawamorita
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Yamaguchi
authors.forename: Takashi
authors.initials: T
authors.lastname: Saito
mesh_terms: D058491:Bacterial Load; D003786:Dental Pulp Cavity / Q000033:anatomy & histology / Q000382:microbiology*; D004708:Endodontics / Q000295:instrumentation; D013293:Enterococcus faecalis; D016908:Gram-Positive Bacterial Infections / Q000532:radiotherapy*; D006801:Humans; D053844:Lasers, Solid-State; D028022:Low-Level Light Therapy; D012388:Root Canal Irrigants / Q000627:therapeutic use
chemical_list: D012388:Root Canal Irrigants