In-office teeth whitening, also called chairside bleaching, takes place during a series of appointments at a dentist's office. There are also various over-the-counter products, such as whitening toothpastes and bleaching strips, that are advertised as being effective teeth-whiteners. However, the concentration of effective ingredients tends to be much lower, lengthening treatment time and often not providing the level of whitening desired.
At our office, our whitening system uses custom-made take home trays that fit over your teeth (like a gum shield) holding the whitening gel against your teeth. The trays are worn for an hour in the morning and an hour at night (you can even wear them overnight if you want). As soon as you are happy with the color of your teeth, you simply stop; most people find that around 2 weeks gets the best results.