title: Bleaching technique effect on dentin permeability.
abstract: OBJECTIVE
  To evaluate the effect of bleaching techniques on dentin permeability. The hypothesis was that the bleaching agent associated or not to etching and/or energy source would be able to increase dentin permeability (conductance).
  
  
  METHODS
  Fifty 1 mm-thick disks of mid-coronal dentin were obtained from human third molars, which were mounted in a filtration chamber, allowing exposure of a standardized area of 0.282 mm2. All specimens were treated with 35% liquid phosphoric acid for 15 seconds to maximize dentin permeability. Then they were randomly allocated to five different conditions: C: placebo gel (negative control); HP: Whiteness HP Maxx (WM)-35% hydrogen peroxide; PA-HP: WM preceded by phosphoric acid etching for 15 seconds. HP-E: WM associated to a light source and PA-HP-E: WM preceded by phosphoric acid etching for 15 seconds and associated to a light source. The bleaching agent was applied for 10 minutes with intermediate agitation at 5 minutes. In the groups associated with a light source, it was activated for 30 seconds every 5 minutes. Afterwards, the permeability (Lp) was measured using the Flodec device. The data were collected and analyzed with one-way ANOVA and Tukey's test (P< 0.05).
  
  
  RESULTS
  Mean and standard deviation of Lp were: C = 1.92 (1.04); HP = 1.14 (0.29); PA-HP = 14.40 (8.62); HP-E = 4.18 (5.14); PA-HP-E = 27.32 (13.24). Data revealed that phosphoric acid etching could increase the dentin permeability, while the bleaching agent or light curing alone did not.
authors.forename: Vanessa Pavoni
authors.initials: VP
authors.lastname: Cannabrava
authors.forename: Samuel Lucas
authors.initials: SL
authors.lastname: Fernandes
authors.forename: Marcela Pagani
authors.initials: MP
authors.lastname: Calabria
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Magalhlães
authors.forename: Sérgio Kiyoshi
authors.initials: SK
authors.lastname: Ishikiriama
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Atta
authors.forename: Linda
authors.initials: L
authors.lastname: Wang
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D003804:Dentin / Q000187:drug effects; D003806:Dentin Permeability / Q000187:drug effects*; D019234:Dentinal Fluid / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008027:Light; D010756:Phosphoric Acids / Q000494:pharmacology; D010919:Placebos; D017655:Silicon Compounds / Q000737:chemistry; D016369:Smear Layer; D013997:Time Factors; D014073:Tooth Bleaching / Q000379:methods*; D058205:Tooth Bleaching Agents / Q000494:pharmacology*
chemical_list: D017554:Carbon Compounds, Inorganic; D010756:Phosphoric Acids; D010919:Placebos; D017655:Silicon Compounds; D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide; C030242:phosphoric acid; C022088:silicon carbide