In basic terms, teeth whitening is the process of bleaching your teeth. The main bleaching agent is hydrogen peroxide (H2O2). Hydrogen peroxide, having a reduction potential of 1.78V makes it a really good oxidizing agent. This molecule is absorbed into your teeth where it encounters organic composites such as hydroxl and superoxide radicals, which is the source of the discoloration. Therefore, when the hydrogen peroxide enters the tooth enamel, it oxidizes these molecules, meaning the molecules lose electrons and the hydrogen peroxide is reduced.Essentially, the H2O2 breaks down these molecules resulting in smaller organic composites that are lighter in color.