A method, the method comprising: obtaining a representation of a patient's dentition, said representation including bite information for a plurality of the patient's teeth; determining a movement path to move one or more teeth from an initial arrangement to a target arrangement; determining a first facet on a first tooth (604, 624, 644, 664) of a first arch and a second facet on a second tooth (614, 634, 654, 674) of a second arch, wherein said bite information indicates that said first tooth and second tooth come into occlusion when the patient bites; and determining an appliance geometry for an orthodontic appliance configured to move the one or more teeth along the movement path, wherein the appliance geometry includes: a first shell (602, 622) including a first tooth-receiving cavity to receive the first tooth, said first tooth-receiving cavity comprising an occlusal surface feature (606, 626, 646) at a location corresponding to the first facet of the first tooth and protruding away from the first tooth-receiving cavity and a second shell (612, 632) comprising a second tooth receiving cavity to receive the second tooth wherein the second tooth receiving cavity comprises a second occlusal surface feature (616, 636, 656) at a location corresponding to the second facet of the second tooth and protruding away from the second tooth-receiving cavity, said first and second occlusal surface features configured to contact and to redirect bite forces to apply a force to drive the one or more teeth on the movement path wherein the appliance geometry modifies the first and second occlusal surfaces of the patient's teeth based on the occlusion forces provided when the patient bites to reduce occlusion force applied to a facet with unfavourable occlusion forces, so as to move one or more of the patient's teeth on the second arch to a predetermined configuration along the movement path when the patient bites while wearing the appliance. obtaining a representation of a patient's dentition, said representation including bite information for a plurality of the patient's teeth; determining a movement path to move one or more teeth from an initial arrangement to a target arrangement; determining a first facet on a first tooth (604, 624, 644, 664) of a first arch and a second facet on a second tooth (614, 634, 654, 674) of a second arch, wherein said bite information indicates that said first tooth and second tooth come into occlusion when the patient bites; and determining an appliance geometry for an orthodontic appliance configured to move the one or more teeth along the movement path, wherein the appliance geometry includes: a first shell (602, 622) including a first tooth-receiving cavity to receive the first tooth, said first tooth-receiving cavity comprising an occlusal surface feature (606, 626, 646) at a location corresponding to the first facet of the first tooth and protruding away from the first tooth-receiving cavity and a second shell (612, 632) comprising a second tooth receiving cavity to receive the second tooth wherein the second tooth receiving cavity comprises a second occlusal surface feature (616, 636, 656) at a location corresponding to the second facet of the second tooth and protruding away from the second tooth-receiving cavity, said first and second occlusal surface features configured to contact and to redirect bite forces to apply a force to drive the one or more teeth on the movement path wherein the appliance geometry modifies the first and second occlusal surfaces of the patient's teeth based on the occlusion forces provided when the patient bites to reduce occlusion force applied to a facet with unfavourable occlusion forces, so as to move one or more of the patient's teeth on the second arch to a predetermined configuration along the movement path when the patient bites while wearing the appliance. a first shell (602, 622) including a first tooth-receiving cavity to receive the first tooth, said first tooth-receiving cavity comprising an occlusal surface feature (606, 626, 646) at a location corresponding to the first facet of the first tooth and protruding away from the first tooth-receiving cavity and a second shell (612, 632) comprising a second tooth receiving cavity to receive the second tooth wherein the second tooth receiving cavity comprises a second occlusal surface feature (616, 636, 656) at a location corresponding to the second facet of the second tooth and protruding away from the second tooth-receiving cavity, said first and second occlusal surface features configured to contact and to redirect bite forces to apply a force to drive the one or more teeth on the movement path wherein the appliance geometry modifies the first and second occlusal surfaces of the patient's teeth based on the occlusion forces provided when the patient bites to reduce occlusion force applied to a facet with unfavourable occlusion forces, so as to move one or more of the patient's teeth on the second arch to a predetermined configuration along the movement path when the patient bites while wearing the appliance.