Professional teeth whitening is available in an in-office procedure as well as take-home trays. In-office whitening is done in a single treatment that takes about an hour to complete. After cleaning the teeth, a bleaching agent is applied to your teeth. A special light is used to help enhance the results, which are noticeable immediately. Take home trays, on the other hand, let you whiten your teeth in the comfort of your own home. Trays are made from impressions of your mouth. They are made to be worn with a bleaching agent for a few hours twice a day or overnight while you sleep. Treatment times vary based on the level of discoloration and your desired results.