Material and methods: Forty samples of enamel were subjected to staining with 25% instant coffee solution for seven days at 37 degree C temperature. The values of the color of stained specimen were taken using a spectrophotometer. Then, the application of bleaching was done on the labial surface of the samples for eight hours daily for seven days. The final color measurement was done and the values of changes were calculated from the color measurements taken at the baseline. The total color change was calculated and designated by Delta (∆ E), which refers to color difference. The values obtained were subjected to statistical analysis. The color changes were analysed using ANOVA and tukey test at 5% level of significance.

Results: The use of manganese gluconate as chemical activator increased the efficiency of bleaching in both 10% and 16% carbamide peroxide. Also the effect of carbamide peroxide bleaching at 10% with manganese gluconate activator and carbamide peroxide bleaching at 16% without activator was comparable.

Interpretation and conclusion: Manganese gluconate in the concentration of 0.01% as a chemical activator increased the bleaching efficiency in both 10% and 16% carbamide peroxide bleaching concentrations. And the effect of carbamide peroxide bleaching at 10% with manganese gluconate activator and carbamide peroxide bleaching at 16% without activator are comparable.