title: Influence of pH on the effectiveness of hydrogen peroxide whitening.
abstract: OBJECTIVE
  To evaluate the influence of pH on the bleaching effect of hydrogen peroxide on chromogen agents.
  
  
  METHODS
  Hydrogen peroxide 50% was mixed with red wine or with an alcoholic solution of tobacco in glass cuvettes, resulting in final peroxide concentrations of 16.97% and 21.12%, respectively. The pH of this mixture was measured and adjusted with 3.3 M HCl solution or 2.5 M NaOH solution to obtain the final pH values of 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, and 9.0. After mixing, the color of these solutions was evaluated in a reflectance spectrophotometer; readings were repeated after 10 minutes for the wine solution and 20 minutes for the tobacco solution. Ten samples were prepared for each solution at each pH. Color changes (Delta E) were calculated. The data were statistically analyzed using analysis of variance one-way and Tukey tests, with a significance level of 5%.
  
  
  RESULTS
  There were significant differences among the different pH values for the wine and tobacco solutions (p=0.0001). The Tukey test showed that for both solutions, pH 9.0 resulted in a significantly greater bleaching effect than the other values tested.
  
  
  CONCLUSIONS
  The efficacy of hydrogen peroxide bleaching is directly proportional to the increase in its pH.
authors.forename: C R G
authors.initials: CR
authors.lastname: Torres
authors.forename: E
authors.initials: E
authors.lastname: Crastechini
authors.forename: F A
authors.initials: FA
authors.lastname: Feitosa
authors.forename: C R
authors.initials: CR
authors.lastname: Pucci
authors.forename: A B
authors.initials: AB
authors.lastname: Borges
mesh_terms: D006801:Humans; D006861:Hydrogen Peroxide / Q000008:administration & dosage*; D006863:Hydrogen-Ion Concentration; D058205:Tooth Bleaching Agents / Q000737:chemistry* / Q000627:therapeutic use; D014075:Tooth Discoloration / Q000188:drug therapy*
chemical_list: D058205:Tooth Bleaching Agents; D006861:Hydrogen Peroxide