title: [Histological evaluations on periapical tissues after irradiation by erbium-doped yttrium aluminum garnet laser in Labradors dogs].
abstract: OBJECTIVE
  To investigate the thermal effects on periapical tissues of Labrador dogs after intra-canal irradiation by erbium-doped yttrium aluminum garnet (Er:YAG) laser at different powers based on the antibacterial experiment of Enterococcus faecalis and Escherichia coli in root canals with an isthmus, to assess the histological changes, and to prove the safety for clinical applications.
  
  
  METHODS
  Two hundred root canals of 10 healthy adult Labradors dogs were selected and divided into 5 groups. Excepted one as control group, root canals in other 4 groups were irradiated by Er:YAG laser with 1.5, 2.0, 2.5, 3.0 W for 30 s. Ten Labradors dogs were sacrificed at 0 (immediately after irradiation), 2 days, 2 weeks, 1 and 2 months. After preparation of pathological specimen, histological changes after laser irradiation in periapical tissues were evaluated and scores of inflammation were graded. Statistical analysis was performed using SPSS 13.0 software package.
  
  
  RESULTS
  No significant difference was observed at the apical area between 1.5, 2.0, 2.5 W and control groups at most periods (P>0.05), whereas significant difference was observed between 3.0 W and other groups for all periods (P<0.05).
  
  
  CONCLUSIONS
  These results suggest that if proper output powers (2.0-2.5 W) of laser irradiation are chosen, disinfection in root canals can be finished successfully and thermal effects on the periapical tissues can be minimized.
authors.affiliation: Special Dental Consultation Clinic, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine. Shanghai 200011, China. E-mail:damingming1228@126.com.
authors.forename: Hao-Ming
authors.initials: HM
authors.lastname: Wang
authors.forename: Meng-Qi
authors.initials: MQ
authors.lastname: Zhou
authors.forename: Jin
authors.initials: J
authors.lastname: Hong
mesh_terms: D000535:Aluminum; D000818:Animals; D003786:Dental Pulp Cavity; D004203:Disinfection; D004285:Dogs; D013293:Enterococcus faecalis; D004871:Erbium; D006801:Humans; D053844:Lasers, Solid-State; D010486:Periapical Tissue / Q000473:pathology* / Q000528:radiation effects; D018915:Root Canal Preparation; D015019:Yttrium
chemical_list: C503779:yttrium-aluminum-garnet; D015019:Yttrium; D004871:Erbium; D000535:Aluminum