Bleaching is a procedure which involves lightening of the colour of a tooth through the application of a chemical agent to oxidize the organic pigmentation in the tooth.
Tooth bleaching today is based upon hydrogen peroxide as an active agent. Hydrogen peroxide may be applied directly or produced in a chemical reaction from sodium perborate or carbamide peroxide. Hydrogen peroxide acts as a strong oxidizing agent through the formation of free radicals, reactive oxygen molecules and hydrogen peroxide anions. These reactive molecules attack the long chained, dark coloured chromophore molecules and split them into smaller, less coloured and more diffusible molecules.