title: Extraradicular diffusion of hydrogen peroxide and pH changes associated with intracoronal bleaching of discoloured teeth using different bleaching agents.
abstract: OBJECTIVE
  To evaluate the extraradicular pH and hydrogen peroxide (HP) diffusion when either 35% carbamide peroxide (CP), 35% HP or sodium perborate (SP) is used for intracoronal bleaching of artificially discoloured teeth.
  
  
  METHODS
  Single rooted extracted human premolars were stained with whole blood cells. After shaping and cleaning, they were root filled and a base cement placed 1 mm below the buccal cementoenamel junction (CEJ). Four cemental defects were prepared just below the CEJ on each root surface. The teeth were randomly divided into four groups of 11 specimens, and intracoronally bleached using CP, HP, SP or distilled water (CL). Each tooth was suspended in a vial of distilled water and bleached for 7 days. The pH of the extraradicular distilled water was tested at 0, 1, 2 and 7 days and the HP that diffused through the root quantified using the Ferrous Oxidation-Xylenol Orange 2 Assay. The results were analysed using the one-way anova and Scheffe tests.
  
  
  RESULTS
  Carbamide peroxide produced the greatest increase and HP the least pH change (P < 0.05 except day 1), SP was intermediate. From day 1 onwards, radicular diffusion of HP was greatest with HP and least with CP (P < 0.01), again SP was intermediate. There was no significant difference between CP and SP.
  
  
  CONCLUSIONS
  Carbamide peroxide had very low levels of extraradicular diffusion of HP, in the presence of cemental defects. It could be an alternative to the other intracoronal bleaching agents.
authors.affiliation: Faculty of Dentistry, National University of Singapore, Singapore.
authors.forename: G P
authors.initials: GP
authors.lastname: Lee
authors.forename: M Y
authors.initials: MY
authors.lastname: Lee
authors.forename: S O Y
authors.initials: SO
authors.lastname: Lum
authors.forename: R S C
authors.initials: RS
authors.lastname: Poh
authors.forename: K-C
authors.initials: KC
authors.lastname: Lim
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001641:Bicuspid; D001881:Borates / Q000737:chemistry / Q000627:therapeutic use; D000077463:Carbamide Peroxide; D003806:Dentin Permeability; D004058:Diffusion; D004338:Drug Combinations; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000627:therapeutic use; D006863:Hydrogen-Ion Concentration; D016877:Oxidants / Q000737:chemistry / Q000627:therapeutic use; D010545:Peroxides / Q000737:chemistry / Q000627:therapeutic use; D012391:Root Resorption / Q000209:etiology; D014073:Tooth Bleaching / Q000009:adverse effects / Q000379:methods*; D014075:Tooth Discoloration / Q000188:drug therapy*; D019553:Tooth, Nonvital; D014508:Urea / Q000031:analogs & derivatives* / Q000737:chemistry / Q000627:therapeutic use
chemical_list: D001881:Borates; D004338:Drug Combinations; D016877:Oxidants; D010545:Peroxides; D000077463:Carbamide Peroxide; D014508:Urea; D006861:Hydrogen Peroxide; C027707:sodium perborate