Extraradicular diffusion of hydrogen peroxide and pH changes associated with intracoronal bleaching of discoloured teeth using different bleaching agents.

AIM 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. METHODOLOGY 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.