title: Influence of Er:YAG laser on microhardness of enamel adjacent to restorations submitted to cariogenic challenge in situ.
abstract: OBJECTIVE
  This study assessed the effect of the Er:YAG laser on enamel adjacent to restorations submitted to cariogenic challenge in situ, by microhardness analysis.
  
  
  BACKGROUND
  The influence of Er:YAG laser energy on secondary caries formation has been investigated in vitro. However, no research involving demineralization around cavities prepared with the Er:YAG laser under intra-oral conditions has yet been described.
  
  
  METHODS
  Slabs of enamel were randomly assigned to seven groups (n = 12), according to the cavity preparation technique: groups I, II, and III--Er:YAG laser, 250 mJ, at 2, 3, and 4 Hz, respectively; groups IV, V, and VI--350 mJ, at 2, 3, and 4 Hz, respectively; group VII--high-speed handpiece (control). Cavities were restored and the specimens were fixed in intra-oral appliances and worn by 12 volunteers for 14 d. Sucrose solution was applied to each slab 6 times/d. Samples were removed, sectioned, and examined for microhardness at 100, 200, and 300 microm (factor distance), and 30, 60, and 90 microm (factor depth), from the restoration and enamel surface, respectively.
  
  
  RESULTS
  Analysis of variance according to a split-plot model showed no difference among the cavity preparation techniques, among distances, or among depths, as well as no difference in the interaction between the factors of cavity preparation and distance. A significant difference was found in the interaction of cavity preparation and depth (p < 0.0001), as identified by contrast technique.
  
  
  CONCLUSIONS
  The results revealed that the Er:YAG laser did not differ from conventional cavity preparation with regard to enamel microhardness.
authors.affiliation: Department of Restorative Dentistry, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors.forename: Daniela T
authors.initials: DT
authors.lastname: Chimello
authors.forename: Mônica C
authors.initials: MC
authors.lastname: Serra
authors.forename: Antonio L
authors.initials: AL
authors.lastname: Rodrigues-Júnior
authors.forename: Jesus D
authors.initials: JD
authors.lastname: Pécora
authors.forename: Silmara A M
authors.initials: SA
authors.lastname: Corona
mesh_terms: D000328:Adult; D003731:Dental Caries / Q000628:therapy; D003733:Dental Caries Susceptibility / Q000528:radiation effects; D003737:Dental Cavity Preparation / Q000295:instrumentation*; D003743:Dental Enamel / Q000528:radiation effects*; D003755:Dental High-Speed Technique; D004311:Double-Blind Method; D005260:Female; D006244:Hardness / Q000528:radiation effects*; D006245:Hardness Tests; D006801:Humans; D053685:Laser Therapy; D053844:Lasers, Solid-State; D008297:Male; D009967:Orthodontic Appliances; D055815:Young Adult