A system and method for determining a center of resistance of a tooth may include receiving a 3D digital representation of an initial arrangement and a final arrangement of a patient's teeth and determining a 3D treatment plan. The 3D treatment plan may include a plurality of 3D stages for rearranging the teeth from the initial arrangement toward the final arrangement. The method may also include determining, in accordance with the 3D treatment plan, an intended movement of the teeth for each of the stages and deriving, using a 3D resistance model, an applied force system for achieving the intended movement of the teeth for each of the stages. The method may also include deriving 3D geometries of oral appliances for the stages in response to the applied force system. Various other systems and methods are also disclosed.