title: A study on acquired acid resistance of enamel and dentin irradiated by Er,Cr:YSGG laser.
abstract: OBJECTIVE
  This investigation was performed to evaluate the acid resistance of lased enamel and dentin by Er,Cr:YSGG laser to artificial caries-like lesions by spectrophotometry, and the ultrastructure of lased areas was investigated by scanning electron microscopy (SEM) in vitro.
  
  
  BACKGROUND
  In recent years, many studies have been performed to evaluate the effects of Er,Cr:YSGG laser on dental hard tissues. However, there have been only a few studies to determine if this laser is suitable for caries preventive treatments.
  
  
  METHODS
  An Er,Cr:YSGG laser was used to irradiate the enamel or dentin samples from 30 extracted human molars at 6 W (67.9 J/cm2) or 5 W (56.6 J/cm2) pulse energy, respectively, with or without water mist. Samples were subjected to 2 microl of 0.1 M lactic acid solution (pH 4.8) for 24 h at 36 degrees C. The parts per million (ppm) of calcium ion (Ca2+) dissolved in each solution was determined by atomic absorption spectrophotometery, and the morphological changes were investigated by SEM.
  
  
  RESULTS
  The lowest mean Ca2+ ppm was recorded in the lased samples. SEM observation showed that the lased areas were melted and seemed to be thermally degenerated. After acid demineralization, the thermally degenerated enamel or dentin surfaces were almost unchanged.
  
  
  CONCLUSIONS
  The results of this study suggested that Er,Cr:YSGG laser irradiation with and without water mist appears to be effective for increasing acid resistance.
authors.affiliation: Department of Endodontics, Showa University School of Dentistry, Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hossain
authors.forename: Y
authors.initials: Y
authors.lastname: Kimura
authors.forename: Y
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Y
authors.initials: Y
authors.lastname: Yamada
authors.forename: J I
authors.initials: JI
authors.lastname: Kinoshita
authors.forename: K
authors.initials: K
authors.lastname: Matsumoto
mesh_terms: D003743:Dental Enamel / Q000528:radiation effects*; D003804:Dentin / Q000528:radiation effects*; D006801:Humans; D019344:Lactic Acid; D053685:Laser Therapy; D013054:Spectrophotometry, Atomic
chemical_list: D019344:Lactic Acid