title: Study on removal effects of filling materials and broken files from root canals using pulsed Nd:YAG laser.
abstract: OBJECTIVE
  The aims of this study were to investigate the capability of removing the filling materials or broken files from root canals with pulsed Nd:YAG laser irradiation at three parameters, and to evaluate the temperature rises on root surfaces and morphological changes of root canal walls in vitro.
  
  
  BACKGROUND
  There has been no report on removing the filling materials and broken instruments from root canals with laser irradiation.
  
  
  METHODS
  Thirty-six extracted human incisors were divided into two groups of 18 each. Eighteen root canals were shaped and obturated with gutta-percha and root canal sealer. In another 18 specimens, 3-mm long fractures of files were performed intentionally during root canal preparation. A pulsed Nd:YAG laser irradiation was performed repeatedly at three parameters of 1, 2, and 3 W to remove the filling materials or file fragments. Temperature rises on root surfaces during laser irradiation were measured by thermography, and the remaining of obturated materials and morphological changes of root canal walls were evaluated by stereoscopy and scanning electron microscopy.
  
  
  RESULTS
  In more than 70% of the teeth, the obturated materials were completely removed by laser, and in more than 55% of the teeth, the broken files were successfully removed. Temperature rises ranging from 17 degrees C to 27 degrees C were measured from 6 to 11 repeated times.
  
  
  CONCLUSIONS
  These results demonstrated that a pulsed Nd:YAG laser irradiation has the capability of removing the obturated materials in root canals and is useful for removing the broken files in same if the counter-measure reducing the temperature rise is performed.
authors.affiliation: Department of Endodontics, Showa University School of Dentistry, Tokyo 145-8515, Japan.
authors.forename: D G
authors.initials: DG
authors.lastname: Yu
authors.forename: Y
authors.initials: Y
authors.lastname: Kimura
authors.forename: Y
authors.initials: Y
authors.lastname: Tomita
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
authors.forename: H
authors.initials: H
authors.lastname: Watanabe
authors.forename: K
authors.initials: K
authors.lastname: Matsumoto
mesh_terms: D003786:Dental Pulp Cavity / Q000528:radiation effects* / Q000648:ultrastructure; D004868:Equipment Failure; D006801:Humans; D007180:Incisor; D053685:Laser Therapy; D008855:Microscopy, Electron, Scanning; D012387:Root Canal Filling Materials / Q000009:adverse effects*; D012389:Root Canal Obturation / Q000379:methods; D018915:Root Canal Preparation / Q000295:instrumentation*; D013696:Temperature; D013817:Thermography; D013997:Time Factors
chemical_list: D012387:Root Canal Filling Materials