an upper dental arch configured to receive at least some of a user's upper teeth, the upper dental arch comprising a connector; and

a lower dental arch configured to receive at least some of the user's lower teeth, the lower dental arch comprising:

a posterior surface configured to face in an anatomically posterior direction when the user's lower teeth are received in the lower dental arch;

a recess in the posterior surface, the recess configured to be open to the anatomically posterior direction; and

a removable receiver configured to be removably positioned within the recess and to be engaged by the connector to define the forward position of the lower dental arch relative to the upper dental arch.