title: Effects of Er,Cr:YSGG laser irradiation in human enamel and dentin: ablation and morphological studies.
abstract: OBJECTIVE
  This investigation was performed to determine quantitatively the ranges of ablation and to evaluate the morphological changes in human enamel and dentin irradiated by Er,Cr:YSGG laser with or without water spray.
  
  
  BACKGROUND
  Recently, Er,Cr:YSGG laser has been introduced in dental clinics to remove carious dental hard tissues in anticipation of replacing the high-speed dental drill.
  
  
  METHODS
  A total of 40 extracted human teeth were used in this study. An Er,Cr:YSGG laser was used to ablate human dental hard tissues with the output powers of 3 to 6 W. Ablation extent with or without water spray at different output powers was measured, and the morphological changes on enamel and dentin were also investigated by stereoscopy and scanning electron microscopy (SEM).
  
  
  RESULTS
  The irradiation with water spray significantly (p < 0.001) increased the ablation depths compared to those irradiated without water mist. Morphological findings by SEM indicated that when irradiated without water spray, carbonization with brown or dark color was recognized in enamel or dentin, respectively. In addition, cavities with a molten lava-like appearance were produced and an irregular structure with many microholes was observed in dentin.
  
  
  CONCLUSIONS
  These results suggest that during the Er,Cr:YSGG laser irradiation, water spray directed at the ablation sites increases the ablation depths and water plays an important role as an initiator of the ablation of dental hard tissues.
authors.affiliation: Department of Endodontics, Showa University School of Dentistry, Kitasenzoku, Ohta-ku, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hossain
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Y
authors.initials: Y
authors.lastname: Yamada
authors.forename: Y
authors.initials: Y
authors.lastname: Kimura
authors.forename: N
authors.initials: N
authors.lastname: Matsumoto
authors.forename: K
authors.initials: K
authors.lastname: Matsumoto
mesh_terms: D003743:Dental Enamel / Q000528:radiation effects* / Q000648:ultrastructure*; D003804:Dentin / Q000528:radiation effects* / Q000648:ultrastructure*; D006801:Humans; D007834:Lasers