Tray Bleaching A custom fitted tray is worn over your teeth. A small amount of the bleaching gel is placed in the tray and worn for a brief amount of time each day. This is the most common technique because it's easy to use and costs less. Impressions are taken of your mouth and a thin custom made plastic tray is made which you take home and wear for about one to two hours per day. While some results may be seen in a couple days, it usually takes one to two weeks to see the full whitening of your teeth. This procedure is sometimes used in conjunction with the in-office laser bleaching if you have severe discoloration (dark grey or purple) or internal teeth staining.