Embodiments include dental appliances, dental appliance systems, and methods of making and using such appliances. In one embodiment, a dental appliance includes a shell having a number of cavities to receive one or more teeth, each cavity having an inner surface. At least a first portion of a particular cavity is scaled-up in size by a first selected percentage over one or more dimensions of a corresponding tooth to provide a first space between the cavity inner surface and the corresponding tooth surface. At least a second portion of the particular cavity is scaled-up in size by a second scaled-up percentage over one or more dimensions of a corresponding gingival outer surface adjacent to the corresponding tooth to provide a second shape.