title: Color alteration, hydrogen peroxide diffusion, and cytotoxicity caused by in-office bleaching protocols.
abstract: OBJECTIVE
  This study evaluated the color alteration, cytotoxicity, and hydrogen peroxide (HP) diffusion associated with different in-office bleaching protocols.
  
  
  METHODS
  Bovine enamel/dentin disks were subjected to three bleaching sessions with 35 % HP (three 15-min applications), 35 % HP (one 45-min application), or 20 % HP (one 45-min application). The control group was not bleached. Before bleaching, the disks were adapted to artificial pulp chambers positioned in compartments containing 1 ml of acetate buffer or medium, so that the dentin remained in contact with these substances. Immediately after bleaching, the HP that diffused through the disks was stabilized by acetate buffer and was quantified (two-way repeated measures ANOVA/Fisher's protected least significant difference (PLSD) test; α = 5 %). Cells of mouse dental papilla cell-23 (MDPC-23) were incubated in this culture media for 1 h, followed by analysis of cellular metabolism (methyl tetrazolium assay) (one-way ANOVA/Tukey test; α = 5 %) and morphology (scanning electron microscopy). The specimen color alteration (ΔE) was analyzed by reflection spectrophotometry (two-way repeated measures ANOVA/Fisher's PLSD test; α = 5 %).
  
  
  RESULTS
  All protocols showed equal effectiveness at the end of the treatment. HP diffusion was significantly higher in the groups bleached with 35 % HP. Reapplication of 35 % HP resulted in increased diffusion only in the first session; however, the decrease in cell metabolism was similar for all studied protocols.
  
  
  CONCLUSIONS
  Despite greater peroxide diffusion in the groups treated with 35 % HP, all protocols showed the same effectiveness and were cytotoxic to MDPC-23 cells.
  
  
  CONCLUSIONS
  Bleaching protocols using high HP concentrations should be avoided because they exert aggressive actions on odontoblast-like cells.
authors.affiliation: Department of Restorative Dentistry, Araçatuba School of Dentistry, Univ. Estadual Paulista (UNESP), Rua José Bonifácio, 11930, Araçatuba, SP, 14801-903, Brazil.
authors.forename: Letícia Cunha Amaral Gonzaga
authors.initials: LC
authors.lastname: de Almeida
authors.forename: Diana Gabriela
authors.initials: DG
authors.lastname: Soares
authors.forename: Marjorie Oliveira
authors.initials: MO
authors.lastname: Gallinari
authors.forename: Carlos Alberto
authors.initials: CA
authors.lastname: de Souza Costa
authors.forename: Paulo Henrique
authors.initials: PH
authors.lastname: Dos Santos
authors.forename: André Luiz Fraga
authors.initials: AL
authors.lastname: Briso
mesh_terms: D000818:Animals; D002417:Cattle; D003743:Dental Enamel / Q000187:drug effects; D004058:Diffusion; D004797:Enzyme-Linked Immunosorbent Assay; D006861:Hydrogen Peroxide / Q000494:pharmacology* / Q000633:toxicity; D066298:In Vitro Techniques; D051379:Mice; D008855:Microscopy, Electron, Scanning; D009804:Odontoblasts / Q000187:drug effects*; D014073:Tooth Bleaching; D058205:Tooth Bleaching Agents / Q000494:pharmacology* / Q000633:toxicity
chemical_list: D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide