Methods for fabricating dental appliances and associated systems are provided. In some embodiments, a method includes defining a plurality of object cross-sections of a dental appliance, and sequentially polymerizing the plurality of object cross-sections to create the dental appliance. The dental appliance can include an outer shell having a plurality of teeth-receiving cavities, and an inner structure coupled to an inner surface of the outer shell. The outer shell can have a first stiffness, and the inner structure can have a second stiffness less than the first stiffness. The sequential polymerization can include integrally forming the outer shell concurrently with the inner structure.