An oral treatment device that includes a mouthpiece and an electromagnetic radiation source. In one aspect, the oral treatment device includes a mouthpiece comprising a curved wall having a concave inner surface and a bite platform extending from the concave inner surface of the curved wall to a distal end, the distal end of the bite platform extending continuously in a non-interrupted manner from a first end of the bite platform to a second end of the bite platform； an electromagnetic radiation source configured to emit electromagnetic radiation from the curved wall； and wherein the bite platform comprises a collapsible region such that the mouthpiece is alterable between: (1) a biased state in which the curved wall has a first curvature； and (2) a flexed state in which the curved wall has a second curvature that is different than the first curvature.
