1. A system for determining appliance geometries for orthodontic treatment of a patient's masticatory system, the system comprising: a processor; and memory comprising instructions that, when executed by the processor, cause the system to: generate a computer representation of the masticatory system of the patient; determine an arch curve corresponding to a desired arrangement for a set of teeth of the masticatory system; digitally model the set of teeth in a plurality of different arrangements representing successive repositioning of the set of teeth from an initial arrangement toward the desired arrangement; and generate a plurality of appliances corresponding to the plurality of different arrangements, the plurality of appliances each having teeth receiving cavities, wherein the teeth receiving cavities of successive appliances have different geometries shaped to receive and resiliently reposition the set of teeth from one arrangement to a successive arrangement, and wherein the plurality of appliances is generated prior to the patient wearing an appliance of the plurality so as to reposition the set of teeth.