In-office treatment can improve the colour of your teeth as much as eight shades, and the procedure takes 1 hour with instant results. The procedure is comfortable and convenient. First, your gums are covered to prevent any contact with the bleaching gel. Next, the gel is carefully applied to the teeth and exposed to an activation light for 15 minutes. The gel is removed, then reapplied and the overall process is repeated twice more for a total of 1 hour.