This post is written by a dentist, Heikki Pilvinen from hammasklinikka Medident Helsinki. He is an expert in dental implants and teeth whitening.


Teeth Whitening is one of the fastest and least invasive techniques to create a big difference in the look of your smile. Majority of the dentists provide either office teeth whitening, take-home teeth whitening kits, or both. The effectiveness of these whitening procedures is slightly different, but their action is generally the same. Initially, you know that whitening works but do you know how it works?

Stains on the teeth can either be extrinsic or intrinsic. Extrinsic stains appear on the surface of the teeth while intrinsic bright tonixteeth, on the other hand, can be found between the microcracks in your enamel and deep within your dentin (the layer of your tooth underneath your enamel). Some of the stains which are extrinsic can also be removed by both whitening toothpastes and rinsing of the mouth. There are some other extrinsic stains which are considered to be stubborn and can only be removed by the use of teeth whitening agents and also the unsightly intrinsic stains that cause discoloration of the teeth can also be removed by the same teeth whitening agent.

While a lot of individual consider teeth whitening as bleaching, it is very vital to understand that the dentist does not make use of the same whitening chemicals that you use to whiten your laundry to whiten your teeth! Laundry bleach is a chemical that is referred to as sodium hypochlorite the odor resembles that of chlorine and can be toxic if swallowed, so this chemical cannot be found very close to your mouth! The two chemicals which are commonly used in tooth whitening are hydrogen peroxide and carbamide peroxide.

Although the enamel which the hard outer surface of your teeth, looks solid, at the microscopic level, it is actually porous. What causes stains and discoloration on the teeth are those compounds from the food you eat or could either be from smoking and this occurs when these chemicals penetrate the porous enamel and accumulate there.  Tooth whitening works when hydrogen peroxide generates a chemical reaction that breaks the staining compounds.

During dental surgery, the dentist will first cleanse the teeth and then apply a gel containing 10 to 35% of hydrogen peroxide. Sometimes a high powered light is then used to help speed up the chemical reaction. After leaving it for a few minutes, the dentist will remove the bleaching gel and apply it again. The whole bleaching procedure usually takes about 45 minutes to one hour.

For teeth whitening at home, your dentist will get the impression of the teeth and create soft dental trays. These trays are then filled with a thin layer of gel containing 10 to 20% carbamide peroxide. (Carbamide peroxide is disintegrated into hydrogen peroxide and urea in the mouth, so the active bleaching agent in at home kits is still hydrogen peroxide.) At-home bleaching trays are put on for several hours during the day or during sleep. Since they are less powerful, at-home systems last for a while to achieve the same whitening effects as in-office systems.

Tooth whitening is not a good solution for everyone. Since tooth whitening is designed to treat the stain on natural dental enamel, patients who have restorations of gums (i.e. fillings or crowns) or veneers should not be treated for tooth whitening. Whitening compounds do not work on ceramic or porcelain composites of which these restorations are made so that the tooth color can become non-coherent. Teeth whitening will not work on tooth discoloration, as a result of changes in the inner part of the teeth, below the enamel, like gray teeth caused by certain medications. Therefore, it is always recommended that teeth whitening, whether at home or in the office, should be performed under the supervision of your dentist.