There are more ways of tooth bleaching. Some clinics do in-office bleaching, which normally takes one or more visit of 30-60 minutes. This method has the advantage of being fast, but it also uses more aggressive bleaching agents, which may leave the teeth very sensitive. We use a more gentle method, which uses individually fabricated trays for home use.

Bleaching using individual trays at home
At the first dental visit (after scaling and polishing) impressions are taken of both jaws. These impressions are used to fabricate very thin trays, which are ready in 2-3 days. The trays are very thin, and since they only cover the teeth, they are usually quite comfortable to use. A small amount of bleaching agent is added to the tray opposite of each tooth before use. The trays can either be used while sleeping, or during the day. Depending on initial tooth color (yellowish teeth bleach more efficiently then gray, for example) results can be seen after a single nights use. Often, use during 3-4 nights will give the desired result. Be careful not to bleach too much! Over bleached teeth may seem unnatural. The trays can be used many times if care is taken in handling them. There is a tendency for bleached teeth to slowly return to their original color, so the trays should be saved for future use. 

As far as it is known, bleaching does not harm the teeth. However, your teeth will most likely be sensitive during bleaching and 1-2 days thereafter.  Fillings, crowns, and veneers will most likely not change color in the same way as your teeth, which may lead to an unsatisfactory result if your front teeth have any of these. It may therefore be necessary to change these restaurations if bleaching is desired. 

Bleaching and tooth cleaning 
Bleaching and tooth cleaning are different. Often, people want their teeth lighter because they are stained by tobacco, red wine, tea, and coffee. A thorough cleaning can remove these superficial stains, at times turning the teeth so light that bleaching is not necessary. Superficial stains and calculus should always be removed prior to bleaching.

Bleaching of discolored, root canal treated teeth
If only a single, root canal treated tooth is discolored, a different method is used for bleaching. In this case the bleaching agent is placed inside the tooth, and covered by a temporary filling. It normally takes several changes of the bleaching agent before the desired result is attained.