[Three-dimensional superimposition of the skull base for the longitudinal evaluation of the effects of growth and of treatment].

To evaluate growth or treatment change, superimposition of serial radiographs on a stable reference structure is necessary. In 2-D cephalometrics, the cranial base is often used for this purpose because it shows minimal changes after neural growth is completed, but the cranial base landmarks in lateral or P-A cephalograms are unreliable when other orientations are evaluated. In this paper we present a novel method for 3-D superimposition based on fully-automated voxel-wise registration of the surface cranial base. The software packages allow quantitative assessment of changes between two time points via calculation of the Euclidean distances between the surfaces of the 3-D models, and visual assessment of the location and magnitude of changes in the jaws over time via graphical overlays in which changes are shown in color maps. This enables a detailed examination of the adaptation patterns for patients who experience clinically significant skeletal changes with growth and/or treatment.