How Do Tooth-Bleaching Agents Work?

Most contain carbamide peroxide, which combines with moisture in the mouth to lighten teeth much as peroxide bleaches hair. Dentists use a concentrated bleach that contains 30% to 35% carbamide peroxide applied for 30 to 60 minutes. Its activity may be enhanced with heat or light. Home kits contain a less-concentrated form, about 10% to 15% carbamide peroxide, that is applied at night for two weeks. The most common side effect is that bleaching makes teeth more sensitive to heat and cold, but that effect subsides with time.