title: Structural changes of Er:YAG laser-irradiated human dentin.
abstract: OBJECTIVE
  The aim of this study was to investigate the phase, compositional, and morphological changes of Er:YAG laser-irradiated dentin.
  
  
  BACKGROUND
  To date, nothing comprehensive has been reported about the phase and compositional changes of human dentin after Er:YAG laser irradiation.
  
  
  METHODS
  The human dentin was irradiated by Er:YAG laser with irradiation energies from 300 mJ/pulse-10 pps-10 sec to 700 mJ/pulse-10 pps-10 sec with and without water spray. After irradiation, the specimens were analyzed by means of x-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).
  
  
  RESULTS
  After exposure to Er:YAG laser, dentin showed no phase changes on the x-ray diffractometer. In Fourier transform infrared analysis, two absorption bands at 2200 and 2015 cm(-1) could be traced on dentin treated by Er:YAG laser with irradiation energies beyond 300 mJ/pulse-10 pps-10 sec and without water spray. The OH(-) band disappeared at 1630 cm(-1). Scanning electron micrographs revealed that laser energy of 500 mJ/pulse-10 pps-10 sec was sufficient to prompt melting and recrystallization of dentin crystals.
  
  
  CONCLUSIONS
  Our study demonstrated that Er:YAG laser irradiation on dentin with water spray would not significantly change the structure and composition. Therefore, water cooling is important for reducing the thermal effect of Er:YAG laser.
authors.affiliation: Graduate Institute of Clinical Dentistry, College of Medicine, National Taiwan University and National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Bor-Shiunn
authors.initials: BS
authors.lastname: Lee
authors.forename: Chun-Pin
authors.initials: CP
authors.lastname: Lin
authors.forename: Yu-Lin
authors.initials: YL
authors.lastname: Hung
authors.forename: Wan-Hong
authors.initials: WH
authors.lastname: Lan
mesh_terms: D003804:Dentin / Q000528:radiation effects* / Q000648:ultrastructure*; D004577:Electron Probe Microanalysis; D004871:Erbium; D006801:Humans; D066298:In Vitro Techniques; D028022:Low-Level Light Therapy / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D008963:Molar; D012680:Sensitivity and Specificity; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship
chemical_list: D004871:Erbium