The key to a successful teeth whitening session lies in the chemicals used. There are different bleaching agents, but two of them are more commonly used: carbimide peroxide and hydrogen peroxide.
Carbamide peroxide, also known as urea hydrogen peroxide and urea peroxide, is an oxidizer. It is a type of compound comprised of urea and hydrogen peroxide. This compound is considered an effective cleaning agent, and most dentists use it for tooth bleaching procedures. When it reacts with water, carbamide peroxide dissolves into its composite parts, supplying the hydrogen peroxide that is necessary for teeth whitening procedures. The reason why this compound is preferred is that it has more stable molecules compared to hydrogen peroxide.
The produced hydrogen peroxide oxidizes extrinsic stains on the enamel. Different methods are used to apply the peroxide gel, from in-surgery application to night-guard application. The effect from the procedure is proportional to the amount of time the gel remains on the teeth. The gel’s concentration also determines the effect. For teeth whitening, concentrations very between 10 percent and 35 percent. However, higher concentrations come with a higher risk of producing side effects, e.g. chemical burns. A concentration of 10 percent is considered safe.
Hydrogen peroxide is another oxidizer which is used as a bleaching agent. It is the simplest type of peroxide and represents a clear liquid that is colorless in dilute solutions. The bleaching agent has a strong oxidizing capacity and is considered a highly reactive chemical. Some studies suggest that high concentrations of hydrogen peroxide can increase the porosity of teeth, thus changing the enamel. Concentrations higher than 38 percent were found to result in teeth demineralization and calcium loss.
The Federal Drug Administration has approved hydrogen peroxide gels with concentration under 16 percent and carbamide peroxide with concentration below 16 percent.
Most over-the-counter products contain hydrogen peroxide in concentrations of 3 percent or 3.5 percent. These are easy to find in most pharmacies and drugstores. When used, they have whitening effect, killing germs and bacteria that are found on the teeth and in the mouth cavity.
Other physical and chemical agents are used for tooth whitening as well. Toothpastes usually contain small amounts of calcium carbonate, aluminum oxide, silica, and calcium phosphate. They act to clean off stains from colored molecules which are absorbed with the food.