The terms whitening and bleaching are often used interchangeably, however there is a difference. Whitening is the umbrella term whereas bleaching is one form of whitening. Teeth can be whitened by physical removal of superficial stains using abrasive agents such as toothpaste or prophy paste, or through bleaching processes, which rely on chemicals to penetrate enamel and dentine.4 Peroxide based whitening products work to remove the appearance of stain through a redox chemical reaction. Free radicals are produced when the oxidising agent hydrogen peroxide (HP) breaks down. These free radicals are then available to react with organic molecules in enamel and dentine, breaking down the double bonds of the chromogens (colour causing agents). These new, simpler molecules reflect light differently resulting in the appearance of whiter teeth.1,4
The active ingredient found in most bleaching agents is hydrogen peroxide (HP), which can be delivered as HP or as carbamide peroxide (CP). CP is a stable compound which in contact with water will break down into HP and urea.1 For example, 10% CP breaks down into about 3% HP and 7% urea.3,5 Consequently, this breakdown process results in a slower release of the HP, and typically requires longer wear times for individuals using CP bleaching agents.