Leaching of hydrogen peroxide from bleached bovine enamel.

Accurately weighed bovine enamel slabs were individually immersed in 2 ml of 35% hydrogen peroxide for 1, 3, 5, 30, or 60 min. A control group was obtained by individual immersion of bovine enamel slabs in 2 ml of saline for 60 min. All samples were washed, dried, acid-etched with 37% phosphoric acid for 60 s, then washed and dried again. Two milliliters of double-distilled water were used for individual sample leaching. Leaching was done for 1, 5, 10, 20 min, or 7 days for the experimental groups and for 7 days for the control group. The samples of one of the experimental groups were leached for a second time for 1 min. A total of 112 samples was used in this study. Hydrogen peroxide was spectrophotometrically identified and quantified in all leaching solutions based on the oxidation reaction of leuco-crystal violet buffer solution by hydrogen peroxide, a reaction catalyzed by horseradish peroxidase. The results revealed a significant difference in the quantity of leached peroxide between bleached samples (irrespective of the duration of leaching) and control, saline-treated ones. No difference was observed in the quantity of leached peroxide between releached samples and control, saline-treated ones. However, these were small, random, and numerically insignificant. Statistically significant differences were also noted among some of the experimental groups. They were thought to hold no clinical significance. The results suggested that upon immersion, the complete leaching of peroxide from bleached enamel occurs rapidly.