An oral treatment device that emits light onto surfaces of a user's teeth. In one aspect, the oral treatment device includes an intraoral mouthpiece. The mouthpiece may comprise a lamp support structure comprising a lamp support surface; first and second lamps, each of the first and second lamps comprising a plurality of light emitters that generate light which is emitted from a rear surface of the lamp; each of the first and second lamps mounted to the lamp support surface, thereby forming a lamp assembly, each of the first and second lamps operably coupled to a control circuit having a power source; and a lamp retaining component coupled to the lamp support structure, a lower portion of the first lamp and an upper portion of the second lamp retained between the lamp retaining component and the lamp support surface of the lamp support structure.