Polymeric shell appliances are provided in which the polymeric shell appliances are configured to provide one or more activation forces to facilitate tooth movement. In many embodiments, the appliances comprise interproximal engagement structures to provide activation forces to interproximal tooth surfaces. In many embodiments, the activation forces are arranged to provide a plurality of forces, including a force in a direction opposite to an intended direction of tooth movement. The polymeric shell appliances may comprise one or more tooth receiving cavities, in which each of the plurality of tooth receiving cavities is shaped and arranged to provide a counter moment of each of the plurality of teeth.
