Teeth whitening is usually preceded by a cleaning to ensure the gel is able to penetrate the tooth surfaces evenly and to reduce potential sensitivity. Before the gel is applied, a mouthguard will be used to gently hold your lips open and back to enable the activating light to reach all your teeth. Next, the gel will be applied and a special light will be focused on your teeth for about 15 minutes. Once the time is up, the gel will be removed from your teeth, revealing your whiter, brighter, healthier-looking smile. While a single treatment can yield good results, a series of up to three treatments can provide the best results, especially when staining and discoloration are significant.