title: In vitro study of the effects of Nd:YAG laser irradiation on the apical sealing of endodontic fillings performed with and without dentin plugs.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effects of Nd:YAG laser irradiation on the apical sealing of root canal fillings with or without a dentin plug.
  
  
  BACKGROUND
  Previous studies have shown that Nd:YAG laser irradiation of root canal wall dentin promotes its melting, recrystallization, and therefore a less permeable surface.
  
  
  METHODS
  Thirty extracted and endodontically treated teeth were divided into three groups. Eight specimens of each group were evaluated by means of quantitative analysis, measuring the marginal apical dye leakage. The remaining two specimens were evaluated by means of qualitative analysis, using the scanning electron microscopy (SEM). For the quantitative analysis, the samples of group I were obturated. In group II, the apical third of the samples were irradiated by the Nd:YAG laser at four exposures of 100 mJ/pulse, 1 W, 10 Hz, 3 sec, and obturated. In group III, an apical dentin plug was condensed and lased using the same parameters of group II, and the root canals were obturated. The samples evaluated by SEM were prepared as those analyzed quantitatively; however, their root canals were not filled.
  
  
  RESULTS
  There were statistically significant differences among the groups regarding dye leakage. Group II showed the minor leakage average, followed, in order, by groups I and III. SEM analysis revealed open dentinal tubules in group I; melting and recrystallizing of the apical root dentin in group II; and melting and recrystallizing of a portion of the dentin plug in group III.
  
  
  CONCLUSIONS
  The Nd:YAG laser irradiation of the root canal apical third without the presence of dentin plug significantly improved the quality of the apical sealing under the experimental conditions tested.
authors.affiliation: Department of Restorative Dentistry, School of Dentistry, University of São Paulo, São Paulo, Brazil. gekelmand@dentistry.ucsf.edu
authors.forename: D
authors.initials: D
authors.lastname: Gekelman
authors.forename: I
authors.initials: I
authors.lastname: Prokopowitsch
authors.forename: C P
authors.initials: CP
authors.lastname: Eduardo
mesh_terms: D003786:Dental Pulp Cavity; D003804:Dentin; D006801:Humans; D066298:In Vitro Techniques; D053685:Laser Therapy; D008855:Microscopy, Electron, Scanning; D012389:Root Canal Obturation