The teeth whitening tray or whitening mouthguard mouthpiece retains the safe whitening gel in close approximation to the teeth. Custom fit teeth whitening mouthpieces are the most effective. This Carbamide peroxide gel oxidizes the stains and accumulated pigments producing the new whiter smile. Simply pour a small amount of the whitening gel into the mouthpiece and keep it in place for a short time as directed by the manufacturer. The effect of some gels can be accelerated by laser lights also available from the MGS. Keep the trays away from heat or pets. Store and clean as per the retailers instructions. Consumers are to be cautioned that tooth sensitivity increases with higher concentration such as 35% to 44%. Any sensitivity can be treated with desensitizing pastes or gels.