title: Effect of Nd:YAG laser irradiation for removal of intracanal debris and smear layer in extracted human teeth.
abstract: OBJECTIVE
  The objective of this study was to evaluate the efficacy of Nd:YAG laser to remove debris and smear layer on the instrumented root canal walls in vitro.
  
  
  BACKGROUND
  There have been some contradictory reports about the efficacy of Nd:YAG laser to remove debris and smear layer.
  
  
  METHODS
  Thirty-six extracted single mandibular incisor human teeth were used in this study. The teeth were sectioned at an enamel-cementum junction and the roots were instrumented up to # 50-K files size, then divided into three groups of 12 teeth. The first group (Group 1) was unlased as a control, and in the other two groups, root canals were irradiated by Nd:YAG laser at two different parameters; 1 W, 20 pps (Group 2) and 2 W, 20 pps (Group 3). After laser irradiation, the roots were bisected longitudinally, observed by scanning electron microscopy, and evaluated the condition of cleanliness on the root canal walls according to our criteria.
  
  
  RESULTS
  In most of the specimens in Groups 1 and 2, debris and smear layer remained on the root canal wall surfaces covering the orifices of dentinal tubules. However, specimen in Group 3 showed very clean root canal walls with debris and smear layer evaporated, melted, fused, and recrystallized in most cases. Statistical analysis demonstrated a significant difference between Groups 1 and 3.
  
  
  CONCLUSIONS
  These results suggest that Nd:YAG laser is useful to remove debris and smear layer and causes melting of internal structures on the instrumented root canal walls at the parameters of 2 W and 20 pps.
authors.affiliation: Department of Endodontics, Showa University School of Dentistry, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Harashima
authors.forename: F H
authors.initials: FH
authors.lastname: Takeda
authors.forename: Y
authors.initials: Y
authors.lastname: Kimura
authors.forename: K
authors.initials: K
authors.lastname: Matsumoto
mesh_terms: D003786:Dental Pulp Cavity / Q000528:radiation effects / Q000648:ultrastructure; D003804:Dentin / Q000528:radiation effects / Q000648:ultrastructure; D005069:Evaluation Studies as Topic; D006801:Humans; D053685:Laser Therapy; D008855:Microscopy, Electron, Scanning; D009354:Neodymium; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000379:methods; D016369:Smear Layer; D018709:Statistics, Nonparametric
chemical_list: D009354:Neodymium