title: In vitro study of the Nd:YAG laser effect on human dental enamel: optical and scanning electron microscope analysis.
abstract: OBJECTIVE
  The Nd:YAG laser irradiation of dental enamel was evaluated in enamel demineralization experiments in a Streptococcus mutans culture media.
  
  
  BACKGROUND
  Previous studies had shown that a continuous wave Nd:YAG laser at an energy of approximately 67 mJ may induce an increased acid resistance in human dental enamel when exposed to severe demineralization conditions.
  
  
  METHODS
  Enamel windows of 3 x 4 cm in the buccal surface were irradiated with a continuous wave Nd:YAG laser at a wavelength of 1,064 microns using energy densities of from 83.75 to 187.50 J/cm2. Enamel windows of 3 x 4 cm on the lingual surface served as control (without the laser irradiation). The enamel windows were then exposed to a Streptococcus mutans culture media at a temperature of 37 degrees C for 15 and 21 days. The laser effects and demineralization were examined both by optical microscopy and scanning electron microscopy (SEM).
  
  
  RESULTS
  A comparison between the lased and the unlased windows of enamel showed fusion and recrystalization of the enamel and increased acid-resistance in all groups irradiated with the Nd:YAG laser. On the other hand, the 3 x 4 delimited enamel surfaces from the control group (not irradiated with the Nd:YAG laser) showed 100% demineralization.
  
  
  CONCLUSIONS
  These findings are consistent with the finding that laser irradiation of dental results in significant reduction of the effective solubility of enamel mineral.
authors.affiliation: Department of Restorative Dentistry, UNESP, São José dos Campos, Brazil. pelinoj@dentistry.ucsf.edu
authors.forename: J E
authors.initials: JE
authors.lastname: Pelino
authors.forename: J B
authors.initials: JB
authors.lastname: Mello
authors.forename: C P
authors.initials: CP
authors.lastname: Eduardo
authors.forename: A O
authors.initials: AO
authors.lastname: Jorge
mesh_terms: D003743:Dental Enamel / Q000528:radiation effects* / Q000648:ultrastructure*; D006801:Humans; D066298:In Vitro Techniques; D007834:Lasers; D008855:Microscopy, Electron, Scanning