title: Influence of chemical activation of a 35% hydrogen peroxide bleaching gel on its penetration and efficacy--in vitro study.
abstract: OBJECTIVE
  The aim of this study was to evaluate the effects of chemical activation of hydrogen peroxide (HP) gel on colour changes and penetration through the tooth structure.
  
  
  METHODS
  One hundred and four bovine incisors were used. One dentine (CD) disc and one enamel-dentine (ED) disc were prepared from each tooth. They were positioned over artificial pulpal chambers and the bleaching was performed with an experimental 35% HP gel. Two control and six experimental groups were prepared. In the positive control group (PC) no chemical activator was used. In the negative control group (NC) the specimens did not receive any bleaching. Each experimental group received a different chemical activator (manganese gluconate-MG; manganese chlorite-MC; ferrous sulphate-FS; ferrous chlorite-FC; and mulberries root extract-MRE). After the bleaching procedure a sample of solution was collected from the artificial pulpal chamber and the HP concentration was measured. The data were analysed using ANOVA, Tukey's, and Dunnett's tests.
  
  
  RESULTS
  The groups MG and FS showed a significantly lower penetration of HP than the PC group. For the parameter Delta E, all the groups, with the exception of the group MRE, showed a significantly higher means in relation to the PC group in ED colour. For dentine colour, just the groups MG and FS had significant differences in relation to PC.
  
  
  CONCLUSIONS
  The addition of MG and FS decreases the penetration of HP. The chemical activation using metal salts tested was effective in increasing the bleaching effect.
authors.affiliation: Department of Restorative Dentistry, São José dos Campos School of Dentistry, São Paulo State University - UNESP, Av. Eng. Francisco José Longo, 777, São José dos Campos, SP, Brazil. carlosrgt@fosjc.unesp.br
authors.forename: Carlos Rocha Gomes
authors.initials: CR
authors.lastname: Torres
authors.forename: Annette
authors.initials: A
authors.lastname: Wiegand
authors.forename: Beatrice
authors.initials: B
authors.lastname: Sener
authors.forename: Thomas
authors.initials: T
authors.lastname: Attin
mesh_terms: D000818:Animals; D002417:Cattle; D002712:Chlorides / Q000494:pharmacology; D003116:Color; D003743:Dental Enamel / Q000033:anatomy & histology / Q000187:drug effects* / Q000378:metabolism; D003745:Dental Enamel Permeability / Q000187:drug effects; D003804:Dentin / Q000033:anatomy & histology / Q000187:drug effects* / Q000378:metabolism; D003806:Dentin Permeability / Q000187:drug effects; D005296:Ferrous Compounds / Q000494:pharmacology; D005782:Gels; D005942:Gluconates / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000493:pharmacokinetics / Q000494:pharmacology*; D017895:Manganese Compounds / Q000494:pharmacology; D031625:Morus; D010936:Plant Extracts / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000493:pharmacokinetics / Q000494:pharmacology*; D013053:Spectrophotometry / Q000379:methods; D013997:Time Factors; D058205:Tooth Bleaching Agents / Q000493:pharmacokinetics / Q000494:pharmacology*
chemical_list: D002712:Chlorides; D005296:Ferrous Compounds; D005782:Gels; D005942:Gluconates; D017895:Manganese Compounds; D010936:Plant Extracts; D017382:Reactive Oxygen Species; D058205:Tooth Bleaching Agents; C020748:ferrous sulfate; D006861:Hydrogen Peroxide; C025340:manganese chloride; C030691:gluconic acid