Abstract: An orthodontic appliance comprising a shell shaped to receive a patient's teeth and to urge one or more teeth into a predetermined alignment and/or orientation, the shell including a jaw-biasing region which extends beyond the patient's internal gum line when the shell is worn over the patient's teeth, the jaw-biasing region being configured to apply a bias to the jaw to modify the shaping thereof. By modifying the shape of the jaw to accommodate the patient's repositioned teeth, the present orthodontic appliance may be able to reduce the likelihood and/or severity of orthodontic relapse, thereby achieving a more stable outcome for the patient.