In vitro peroxide penetration into the pulp chamber from newer bleaching products

To investigate peroxide penetration from newer bleaching products into the pulp chamber.

Fifty extracted human maxillary central incisor teeth were separated into five groups (n = 10). All the teeth were sectioned 3 mm apical to the cemento-enamel junction; the intracoronal pulp tissue was removed, and the pulp chamber filled with acetate buffer. Buccal crown surfaces of teeth in the experimental groups were subjected to either a whitening strip (containing 5.3% hydrogen peroxide-G1) or one of three paint-on liquid whiteners (containing 19% sodium percarbonate peroxide-G2, 18% carbamide peroxide-G3 and 8.7% hydrogen peroxide-G4). The teeth in the control group (G5) were exposed only to distilled water. The acetate buffer solution in each tooth was then transferred to a glass test tube after 30 min and leuco-crystal violet and enzyme horseradish peroxidase were added, producing a blue solution. The optical density of the resultant blue colour in the tubes was measured by a UV-visible spectrophotometer at a wavelength of 596 nm. The values were converted into microgram equivalents of HP using a spectrophotometric calibration curve. Data were analysed statistically using the Kruskal-Wallis Analysis of Variance and the Mann-Whitney U-test.

Statistically significant differences were found between all of the groups (P < 0.05). Pulpal peroxide was not observed in the control group. The amount of hydrogen peroxide (microg) found in the pulp chamber of G1 (0.726 +/- 0.024) > G4 (0.443 +/- 0.017) > G3 (0.231 +/- 0.011) > G2 (0.175 +/- 0.012).

The peroxides from the whitening strip and paint-on whiteners penetrated into the pulp chamber to varying degrees.