Registration of 2D or 3D structure enables comparisons between groups or individuals. Shape variation between groups can so be appreciated. It is also ideal for studying growth or aging or other change in shape of structures anticipated because of an identified biomechanical stimulus. The change in shape of the mandible when teeth are lost is such an example. Sophisticated radiographic techniques further allow for non-destructive imaging of inner structure, such as the cochlea. Measurements are then possible in a 3D context.