title: Evaluation of the bactericidal effect of Nd:YAG, Er:YAG, Er,Cr:YSGG laser radiation, and antimicrobial photodynamic therapy (aPDT) in experimentally infected root canals.
abstract: OBJECTIVE
  In recent years, various laser systems have been introduced into the field of laser-assisted endodontic therapy. The aim of this study was to evaluate the bactericidal effect of Nd:YAG, Er:YAG, Er,Cr:YSGG laser radiation, and antimicrobial photodynamic therapy (aPDT) in experimentally infected root canals compared with standard endodontic treatment of 5.25% sodium hypochlorite (NaClO) irrigation.
  
  
  METHODS
  Two hundred and twenty infected root canals from extracted human teeth (contaminated with Enterococcus faecalis ATCC 4083 for 4 weeks) were randomly divided into five experimental groups (Nd:YAG, Er:YAG + 5.25% NaClO + 0.9% normal saline + distilled water (Er:YAG/NaClO/NS/DW), Er:YAG + 0.9% normal saline + distilled water (Er:YAG/NS/DW), Er,Cr:YSGG, and aPDT) and two control groups (5.25% NaClO as positive control and 0.9% normal saline (NS) as negative control). The numbers of bacteria on the surface of root canal walls and at different depths inside dentinal tubules before and after treatment were analyzed by means of one-way analysis of variance (one-way ANOVA). The morphology of bacterial cells before and after treatment was examined by scanning electron microscopy (SEM).
  
  
  RESULTS
  After treatment, the bacterial reductions in the experimental groups and the positive control group were significantly greater than that of the negative control group (P < 0.001). However, only Er:YAG/NaClO/NS/DW group showed no bacterial growth (the bacterial reduction reached up to 100%) on the surface of root canal walls or at 100/200 µm inside the dentinal tubules.
  
  
  CONCLUSIONS
  All the laser radiation protocols tested, especially Er:YAG/NaClO/NS/DW, have effective bactericidal effect in experimentally infected root canals. Er:YAG/NaClO/NS/DW seems to be an ideal protocol for root canal disinfection during endodontic therapy.
authors.affiliation: Department of Operative Dentistry and Endodontics, School of Stomatology, Fourth Military Medical University, 145 West Chang-le Road, Xi'an 710032, PR China.
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Cheng
authors.forename: Sumin
authors.initials: S
authors.lastname: Guan
authors.forename: Hong
authors.initials: H
authors.lastname: Lu
authors.forename: Chunmiao
authors.initials: C
authors.lastname: Zhao
authors.forename: Xingxing
authors.initials: X
authors.lastname: Chen
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.forename: Qian
authors.initials: Q
authors.lastname: Bai
authors.forename: Yu
authors.initials: Y
authors.lastname: Tian
authors.forename: Qing
authors.initials: Q
authors.lastname: Yu
mesh_terms: D000891:Anti-Infective Agents, Local / Q000627:therapeutic use; D018441:Biofilms / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects; D015169:Colony Count, Microbial; D003131:Combined Modality Therapy; D003786:Dental Pulp Cavity / Q000187:drug effects / Q000382:microbiology* / Q000528:radiation effects; D013293:Enterococcus faecalis / Q000187:drug effects / Q000254:growth & development / Q000528:radiation effects; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D016908:Gram-Positive Bacterial Infections / Q000628:therapy*; D006801:Humans; D066298:In Vitro Techniques; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D008751:Methylene Blue / Q000627:therapeutic use*; D008855:Microscopy, Electron, Scanning; D010778:Photochemotherapy; D012973:Sodium Hypochlorite / Q000627:therapeutic use
chemical_list: D000891:Anti-Infective Agents, Local; D004791:Enzyme Inhibitors; D012973:Sodium Hypochlorite; D008751:Methylene Blue