title: In vitro assessment of the acid resistance of demineralized enamel irradiated with Er, Cr:YSGG and Nd:YAG lasers.
abstract: OBJECTIVE
  This study's purpose was to evaluate the acid resistance of demineralized enamel irradiated with high-intensity lasers.
  
  
  METHODS
  Enamel fragments were demineralized and treated as follows (N=10): Group 1-no treatment; Group 2-five percent sodium fluoride (NaF) varnish; Group 3-Er, Cr:YSGG laser (8.92 J/cm2, 0.5 W, 20 Hz, 30 seconds); Group 4-NaF and Er, Cr:YSGG laser; Group 5-Er, Cr:YSGG laser and NaF; Group 6-Nd:YAG laser (84.9 J/cm2, 0.5 W, 10 Hz, 30 seconds); Group 7-NaF and Nd:YAG laser; and Group 8-Nd:YAG laser and NaF. The samples were subjected to pH-cycling and assessed by microhardness (analysis of variance; α equals five percent) at different depths from the outer enamel surface. Samples were observed using polarized light microscopy (PLM) and scanning electron microscopy (SEM).
  
  
  RESULTS
  There were no significant differences among the experimental groups in any of the subsurface layers evaluated. PLM observation revealed that the extent of demineralization of the irradiated samples was similar to the samples for Group 1 (control). SEM observation showed that irradiated surfaces were ablated and presented areas of melting.
  
  
  CONCLUSIONS
  Laser irradiation, with or without applying five percent sodium fluoride, was not capable of increasing the enamel white spot lesions' acid resistance.
authors.affiliation: School of Dentistry, University of Uberaba, Minas Gerais, Brazil.
authors.forename: Diones M
authors.initials: DM
authors.lastname: Santos
authors.affiliation: Biopathology Division; in the School of Dentistry, University of Uberaba, Minas Gerais, Brazil.
authors.forename: Ruchele D
authors.initials: RD
authors.lastname: Nogueira
authors.affiliation: Biomaterials Division; in the School of Dentistry, University of Uberaba, Minas Gerais, Brazil.
authors.forename: Cesar P
authors.initials: CP
authors.lastname: Lepri
authors.affiliation: Biomaterials Division; in the School of Dentistry, University of Uberaba, Minas Gerais, Brazil.
authors.forename: Luciano S
authors.initials: LS
authors.lastname: Gonçalves
authors.affiliation: Department of Restorative Dentistry, Ribeirão Preto School of Dentistry, University of São Paulo, São Paulo, Brazil.
authors.forename: Regina G
authors.initials: RG
authors.lastname: Palma-Dibb
authors.affiliation: Biomaterials Division, School of Dentistry, University of Uberaba, Minas Gerais, Brazil. vinicius.martins@uniube.br.
authors.forename: Vinícius R
authors.initials: VR
authors.lastname: Geraldo-Martins
mesh_terms: D000143:Acids; D000818:Animals; D002327:Cariostatic Agents / Q000494:pharmacology; D002417:Cattle; D003743:Dental Enamel / Q000187:drug effects / Q000528:radiation effects* / Q000648:ultrastructure; D005460:Fluorides, Topical / Q000494:pharmacology; D006244:Hardness; D006863:Hydrogen-Ion Concentration; D053844:Lasers, Solid-State / Q000627:therapeutic use*; D028022:Low-Level Light Therapy / Q000379:methods*; D008855:Microscopy, Electron, Scanning; D008859:Microscopy, Polarization; D012969:Sodium Fluoride / Q000494:pharmacology; D017001:Tooth Demineralization / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy; D014089:Tooth Remineralization
chemical_list: D000143:Acids; D002327:Cariostatic Agents; D005460:Fluorides, Topical; D012969:Sodium Fluoride