title: Chemical Composition and Microhardness of Human Enamel Treated with Fluoridated Whintening Agents. A Studyin Situ.
abstract: BACKGROUND
  Dental whitening has been increasingly sought out to improve dental aesthetics, but may cause chemical and morphological changes in dental enamel surfaces.
  
  
  OBJECTIVE
  Assessin situthe effects of high-concentration hydrogen peroxide with and without fluoride on human dental enamel using the ion chromatography test (IC) and the Knoop hardness test (KHN).
  
  
  METHODS
  Nineteen enamel specimens were prepared using third human molars. These specimens were fixed on molars of volunteers and were divided into groups: OP38-Opalescence Boost PF38%, PO37-Pola Office 37.5% and CO-Control group. For chemical analysis (n= 3), the dentin layer was removed, keeping only the enamel, which was subjected to acidic digestion by microwave radiation. It was necessary to perform sample dilutions for the elements fluorine (F), calcium (Ca) and phosphorus (P) for quantification using the IC test. The KHN (n= 5) was performed before and after the treatments. Five indentations were made, separated by 100 µm, for each specimen using a load of 25 gf for 5 seconds in the microdurometer. The data were analyzed using ANOVA with a 5% significance level.
  
  
  RESULTS
  The OP38 group had the largest concentrations of F, Ca and P ions. The PO37 group showed the lowest concentrations of F and Ca ions. The average KHN was not significantly different between the OP38 and PO37 groups.
  
  
  CONCLUSIONS
  Enamel whitened with hydrogen peroxide containing fluoride had greater concentrations of F, Ca and P ions. The presence of fluoride in the whitening agent did not influence the enamel microhardness.
authors.affiliation: Faculty of Dentistry, Federal University of Para, Para, Brazil.
authors.forename: Thais de Mendonça
authors.initials: TM
authors.lastname: Petta
authors.affiliation: Faculty of Dentistry, Federal University of Para, Para, Brazil.
authors.forename: Yasmin
authors.initials: Y
authors.lastname: do Socorro Batista de Lima Gomes
authors.affiliation: Faculty of Dentistry, Federal University of Para, Para, Brazil.
authors.forename: Renata
authors.initials: R
authors.lastname: Antunes Esteves
authors.affiliation: Public Health, Evandro Chagas Institute, Para, Brazil.
authors.forename: Kelson
authors.initials: K
authors.lastname: do Carmo Freitas Faial
authors.affiliation: Faculty of Dentistry, Federal University of Para, Para, Brazil.
authors.forename: Roberta
authors.initials: R
authors.lastname: Souza D Almeida Couto
authors.affiliation: Faculty of Dentistry, Federal University of Para, Para, Brazil.
authors.forename: Cecy
authors.initials: C
authors.lastname: Martins Silva
keywords: Dental whitening; Fluoride; Hydrogen peroxide; Microhardness; Peroxides; Whitening agent