title: Thermographical and morphological studies of Er,Cr:YSGG laser irradiation on root canal walls.
abstract: OBJECTIVE
  This study was performed to investigate the temperature rises on root surfaces and morphological changes on root canal walls of extracted human teeth after irradiation by erbium, chromium: yttrium, scandium, gallium, garnet (Er, Cr:YSGG) laser and to evaluate the efficiency in removing smear layer and debris from the prepared root canal walls in vitro.
  
  
  BACKGROUND
  No report on Er, Cr:YSGG laser effects under various conditions and specific tips for endodontic treatments has been reported.
  
  
  METHODS
  Sixty extracted human teeth with single and straight root were used in this study. The teeth were prepared at 1 mm short of the apical foramen by a conventional technique using K-files. Fifty-four specimens were irradiated by Er, Cr:YSGG laser at the output powers of 2 W, 3 W, and 5 W for 7 sec with three fiber tips (200, 320, and 400 microm diameters). Temperature changes were recorded thermographically. All teeth were examined by light microscopy or scanning electron microscopy (SEM).
  
  
  RESULTS
  Thermographic study showed that the average temperature rises on root surfaces were less than 8 degrees C. Observation by light microscopy revealed the ablation at the apical stop, and that by SEM indicated that laser irradiation at 5 W using a fiber tip with 400 microm diameter was efficient for removing smear layer and debris without carbonization or melting.
  
  
  CONCLUSIONS
  The results of this study suggested that the temperature rises during Er, Cr:YSGG laser irradiation at the parameters used in this study are minimal to cause the damage on periodontal and bone tissues. Moreover, it was suggested that it is efficient to remove smear layer and debris without causing any carbonization and melting.
authors.affiliation: Department of Endodontics, Showa University School of Dentistry, 2-1-1 Kitasenzoku, Ohta-ku, Tokyo 145-8515, Japan.
authors.forename: Nelson Tatsunari
authors.initials: NT
authors.lastname: Ishizaki
authors.forename: Koukichi
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Kimura
authors.forename: Xiaogu
authors.initials: X
authors.lastname: Wang
authors.forename: Jun-Ichiro
authors.initials: J
authors.lastname: Kinoshita
authors.forename: Sheila Mayumi
authors.initials: SM
authors.lastname: Okano
authors.forename: Jayanetti Asiri
authors.initials: JA
authors.lastname: Jayawardena
mesh_terms: D002857:Chromium; D003737:Dental Cavity Preparation; D003786:Dental Pulp Cavity / Q000528:radiation effects*; D004577:Electron Probe Microanalysis; D004871:Erbium; D006801:Humans; D007834:Lasers; D028022:Low-Level Light Therapy / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D010780:Photogrammetry; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D013696:Temperature; D014092:Tooth Root / Q000528:radiation effects* / Q000648:ultrastructure*; D015019:Yttrium
chemical_list: D002857:Chromium; D015019:Yttrium; D004871:Erbium