The present invention provides a system and method for correcting facial features and oral function in a subject. Also provided are a plurality of intra-oral appliances, which make up the system. The intra-oral appliances each include an appliance body configured for engaging one or more of the gingival-buccal area, the gingivolabial area, and the vestibular area of the subject's mouth, and include one or more extensions for at least partly defining the cavity in the vestibule of the subject's mouth.