title: Sub ablative Er: YAG laser irradiation on surface roughness of eroded dental enamel.
abstract: OBJECTIVE
  This study evaluated the effects of Er:YAG laser irradiation applied at varying pulse repetition rate on the surface roughness of eroded enamel.
  
  
  METHODS
  Bovine enamel slabs (n = 10) were embedded in polyester resin, ground, and polished. To erosive challenges, specimens were immersed two times per day in 20mL of concentrated orange juice (pH = 3.84) under agitation, during a two-day period. Specimens were randomly assigned to irradiation with the Er:YAG laser (focused mode, pulse energy of 60 mJ and energy density of 3.79 J/cm(2) ) operating at 1, 2, 3, or 4 Hz. The control group was left nonirradiated. Surface roughness measurements were recorded post erosion-like formation and further erosive episodes by a profilometer and observed through atomic force microscopy (AFM).
  
  
  RESULTS
  Analysis of variance revealed that the control group showed the lowest surface roughness, while laser-irradiated substrates did not differ from each other following post erosion-like lesion formation. According to analysis of covariance, at further erosive episodes, the control group demonstrated lower surface roughness (P > 0.05), than any of the irradiated groups (P < 0.05).
  
  
  CONCLUSIONS
  The pulse repetition rate of the Er:YAG laser did not affect roughness of dental enamel eroded. The AFM images showed that the specimens irradiated by the Er:YAG laser at 1 Hz presented a less rough surface than those irradiated at 2, 3, and 4 Hz.
authors: Faculty of Dentistry of Ribeirao Preto, University of Sao Paulo, Department of Restorative Dentistry, Ribeirao Preto, Sao Paul, Brazil.
authors: Fabiana Almeida
authors: FA
authors: Curylofo-Zotti
authors: Faculty of Dentistry of Ribeirao Preto, University of Sao Paulo, Department of Restorative Dentistry, Ribeirao Preto, Sao Paul, Brazil.
authors: Taísa Penazzo
authors: TP
authors: Lepri
authors: School of Dentistry, University of Ribeirao Preto, Ribeirao Preto, Sao Paul, Brazil.
authors: Vivian
authors: V
authors: Colucci
authors: Sao Leopoldo Mandic Institute and Dental Research Center, Department of Restorative Dentistry, Campinas, Sao Paul, Brazil.
authors: Cecília Pedroso
authors: CP
authors: Turssi
authors: Faculty of Dentistry of Ribeirao Preto, University of Sao Paulo, Department of Restorative Dentistry, Ribeirao Preto, Sao Paul, Brazil.
authors: Silmara Aparecida Milori
authors: SA
authors: Corona
mesh_terms: D000818:Animals; D002417:Cattle; D003743:Dental Enamel / Q000528:radiation effects*; D053844:Lasers, Solid-State; D028022:Low-Level Light Therapy; D018625:Microscopy, Atomic Force; D013499:Surface Properties
keywords: AFM; dental erosion; profilometer; pulse repetition rate