A plastic mouthpiece insert for allowing a wearer to whiten their teeth while getting a suntan, and have a generally oblong oval-rectangular opening with a curved rear end that abuts against the root surfaces of the frontal upper and lower teeth of the wearer. A raised front edge can protect the lips and separate in place about the opening to the mouthpiece. Whitening agents can be used to enhance the whitening effect so that ultraviolet light and heat source such as the sun or a sunlamp is all that it is needed. Reflective inner walls in the mouthpiece can magnify light to the teeth. The mouthpiece can include bite tables, and the side walls of the mouthpiece can be inwardly flared and funnel shaped for focusing and magnifying incoming light and heat. The mouthpiece can be colored to protect the inside of the wearer's mouth from receiving any light.