A mouthpiece that adjusts manually in the mouth and seals the treatment area. It includes light emitters and heat generators. Textured bands guide and direct light to diffuse evenly. A seal bead seals the gum above the teeth. For whitening, a whitening gel is first applied to the users teeth, the mouthpiece is then positioned in the users mouth, and the seal bead seals against the users gums. Then, the light emitter(s) and heat generator(s) are activated to effect the whitening while causing an increase in the temperature enabling the user to mold the mouthpiece to their mouth.
