Teeth whitening is a cosmetic dental procedure that can help to improve the appearance of your smile by lightening the color of your teeth. It can remove stains and make your teeth look whiter. Teeth whitening works by using a bleaching agent to break down the molecules that cause teeth to stain. The bleaching agent is typically a hydrogen peroxide or carbamide peroxide solution. The bleaching agent is applied to the teeth and then activated by a light or heat source. The activated bleaching agent then penetrates the enamel and dentin of the teeth, breaking down the molecules that cause stains.