title: Morphological changes of human teeth with Er:YAG laser irradiation.
abstract: OBJECTIVE
  The purpose of this study was to investigate morphological changes in human enamel and dentin structures irradiated with the use of an Er:YAG laser.
  
  
  BACKGROUND
  Despite the high number of research projects concerned with digital applications of lasers, few studies have targeted the effects of Er:YAG laser irradiation on human enamel or dentin structures.
  
  
  METHODS
  Enamel and dentin surfaces of 40 extracted human teeth were irradiated for 5 seconds with a 2.94 microns wavelength, at an output of 300 mJ. Histological and scanning electron microscope studies were then performed to determine the morphological changes in the enamel and dentin structures of those teeth.
  
  
  RESULTS
  The Er:YAG laser beam produced defects without signs of serious thermal damage to enamel or dentin. Undesirable thermal effects such as surface cracking or carbonization were not observed. Histological examinations revealed the presence of a thin basophilic line at the bottom and along the walls of defects in the dentin. These morphological changes were evidence of minimal thermal damage to surrounding tissue.
  
  
  CONCLUSIONS
  These findings suggest that it is possible to remove the enamel and dentin using Er:YAG laser irradiation with minimal thermal changes. However, the mechanism involved in the ablation of enamel and dentin by Er:YAG laser irradiation has not been clarified in this study. Therefore, more research is necessary before the Er:YAG laser can be used clinically in the future.
authors: Department of Endodontics, School of Dentistry, Loma Linda, California, USA.
authors: H
authors: H
authors: Tokonabe
authors: R
authors: R
authors: Kouji
authors: H
authors: H
authors: Watanabe
authors: Y
authors: Y
authors: Nakamura
authors: K
authors: K
authors: Matsumoto
mesh_terms: D003743:Dental Enamel / Q000528:radiation effects*; D003804:Dentin / Q000528:radiation effects*; D004577:Electron Probe Microanalysis; D004871:Erbium; D006801:Humans; D007834:Lasers / Q000009:adverse effects*; D008855:Microscopy, Electron, Scanning; D013499:Surface Properties / Q000528:radiation effects
chemical_list: D004871:Erbium