A method and apparatus for applying a rotational transform to a portion of a three-dimensional representation of an appliance for a living body is disclosed. The representation is defined by an input plurality of coordinates stored in a processor circuit memory, the input plurality of coordinates representing a general shape of the appliance. The method involves applying the rotational transform to the portion of the representation of the appliance within the transform volume to produce an output plurality of coordinates representing a modified shape of the appliance such that the general shape of portions of the appliance outside the transform volume remain un-modified by the rotational transform, and storing the output plurality of coordinates in the processor circuit memory.