title: Impact of hydrogen peroxide activated by lighting-emitting diode/laser system on enamel color and microhardness: An in situ design.
abstract: BACKGROUND
  Hydrogen peroxide (HP) at lower concentration can provide less alteration on enamel surface and when combined with laser therapy, could decrease tooth sensitivity. This in situ study evaluated the influence of 15% and 35% HP gel activated by lighting-emitting diode (LED)/laser light for in-office tooth bleaching.
  
  
  METHODS
  Forty-four bovine enamel slabs were polished and subjected to surface microhardness (load of 25 g for 5 s). The specimens were placed in intraoral palatal devices of 11 volunteers (n = 11). Sample was randomly distributed into four groups according to the bleaching protocol: 15% HP, 15% HP activated by LED/laser, 35% HP, and 35% HP activated by LED/laser. The experimental phase comprised 15 days and bleaching protocols were performed on the 2(nd) and 9(th) days. Surface microhardness (KHN) and color changes were measured and data were analyzed by ANOVA (α = 0.05).
  
  
  RESULTS
  There were no significant differences in microhardness values neither in color alteration of enamel treated with 15% HP and 35% HP activated or not by LED/laser system (P > 0.05).
  
  
  CONCLUSIONS
  Both concentrations of HP (15 or 35%), regardless of activated by an LED/laser light, did not affect the surface microhardness and had the same effectiveness in enamel bleaching.
authors.affiliation: Department of Restorative Dentistry, Ribeirao Preto School of Dentistry, University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Ana Bárbara Araújo
authors.initials: AB
authors.lastname: Loiola
authors.affiliation: Department of Restorative Dentistry, Ribeirao Preto School of Dentistry, University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Aline Evangelista
authors.initials: AE
authors.lastname: Souza-Gabriel
authors.affiliation: Department of Restorative Dentistry, Ribeirao Preto School of Dentistry, University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Renata Siqueira
authors.initials: RS
authors.lastname: Scatolin
authors.affiliation: Department of Restorative Dentistry, Ribeirao Preto School of Dentistry, University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Silmara Aparecida Milori
authors.initials: SA
authors.lastname: Corona
keywords: Hydrogen peroxide; laser; microhardness; tooth bleaching