The mouthpiece includes a plurality of individual thin layers of material forming a base or shell portion of the mouthpiece alternating with a plurality of individual bristle layers which are configured to the shape of bristles at the interior surfaces thereof. The base layers are comprised of a material which is sufficiently stiff to permit driving of the mouthpiece, while the bristle layers comprise material which is sufficiently flexible to produce an effective scrubbing action in operation without damage to the mouth tissues.