title: [A study on acquired acid resistance of enamel and dentine irradiated by Er, Cr: YSGG laser in vitro].
abstract: OBJECTIVE
  To evaluate the acid resistance of enamel and dentin irradiated by Er, Cr: YSGG laser to artificial caries formation in vitro.
  
  
  METHODS
  Enamel and dentin samples were irradiated with Er, Cr: YSGG laser at 6 W or 4 W for 6 second, respectively. Every sample was immersed in 3 ml of lactic demineralization solution at pH 4.8 and incubated at 37 degrees C for 24 hours. The parts per million of calcium ion of each solution was measured by atomic absorption spectrophotometry, the quantities of calcium and phosphate on the surface of enamel and dentin sample were examined by SED-X and the ultrastructure was investigated by SEM.
  
  
  RESULTS
  In the enamel and dentin samples, the dissolved Ca(2+) concentration in laser group were significantly decreased compared with that of the control group (P < 0.05). The quantities of Ca (weight%) in enamel and dentin were significantly higher in the laser group than in the control group (P < 0.05). The content of P was increased in dentin and enamel samples, but only the increase in enamel sample was significant (P < 0.05). In both samples, no significant changes on Ca/P weight ratio were found between the groups. The irradiated enamel and dentin surface lacked a smear layer and showed various patterns of microirregulation with a scaly appearance, the openings of dentinal tubules were clearly visible, but no melting or carbonization was observed.
  
  
  CONCLUSIONS
  Er, Cr: YSGG laser irradiation is effective for increasing acid resistance of dental hard tissue and does not cause thermal side effect.
authors.affiliation: Department of Stomatology, Beijing Tongren Hospital, Capital University of Medical Sciences, Beijing 100730, China. qly429@yahoo.com.cn
authors.forename: Li-yan
authors.initials: LY
authors.lastname: Qiao
authors.forename: Jing-tao
authors.initials: JT
authors.lastname: Yu
authors.forename: Xing-ya
authors.initials: XY
authors.lastname: Jia
mesh_terms: D002118:Calcium / Q000032:analysis; D003743:Dental Enamel / Q000528:radiation effects*; D003804:Dentin / Q000528:radiation effects*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D053685:Laser Therapy; D053844:Lasers, Solid-State / Q000627:therapeutic use; D010758:Phosphorus / Q000032:analysis
chemical_list: D010758:Phosphorus; D002118:Calcium