title: Effects of intracanal carbon dioxide laser irradiation on cultured human fibroblasts.
abstract: OBJECTIVE
  The purpose of this study was to evaluate, under various conditions, the damage that might occur to viable cells after CO2 laser irradiation of the root canal.
  
  
  METHODS
  A laser tip was placed within the root canal of extracted human teeth that were positioned above cultured fibroblasts (NB cells), and then irradiation was applied. The irradiation modes used were either pulse (40 pps) or super-pulse (151 pps). The laser energy was set at 32 J in both modes, and the tip of the laser beam was positioned to a point 2 mm from the fibroblasts.
  
  
  RESULTS
  When the pulse mode irradiation was applied, there was significant difference (P < .05) in the percentage of viable cells between teeth with closed apical foramen (1-mm wall between root canal and root apex) and the #15 group (No. 15 K-file used), #30 group (No. 30 K-file), or #50 group (No. 50 K-file). The difference between the #30 group and the #50 group (P < .05) was also significant. The larger the diameter of the apical foramen became, the lower was the percentage of viable cells.
  
  
  CONCLUSIONS
  If a CO2 laser irradiates a root canal system enlarged to within 1 mm of the root canal length, little damage to the periapical tissues would be expected to occur.
authors.affiliation: Department of Endodontics, School of Dentistry, Aichi-Gakuin University, Nagoya, Japan. nhoriba@dpc.aichi-gakuin.ac.jp
authors.forename: Naoki
authors.initials: N
authors.lastname: Horiba
authors.forename: Ayako
authors.initials: A
authors.lastname: Itoh
authors.forename: Masataka
authors.initials: M
authors.lastname: Yamaguchi
authors.forename: Toru
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Akira
authors.initials: A
authors.lastname: Senda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D002245:Carbon Dioxide; D016923:Cell Death; D002460:Cell Line; D005347:Fibroblasts / Q000473:pathology*; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D018915:Root Canal Preparation / Q000009:adverse effects* / Q000295:instrumentation; D018709:Statistics, Nonparametric; D019227:Tooth Apex / Q000033:anatomy & histology
chemical_list: D002245:Carbon Dioxide