The shape of the mandible.

The validity of traditional cephalometric techniques for orthognathic surgical diagnosis and planning remains controversial. This not only reflects the fact that the linear and angular parameters combine size and shape together, but the techniques also generally rely upon non-homologous datum points, with the resultant data being of dubious mathematical significance. In order to circumvent these problems, the technique of medial (symmetric) axis transformation was used to compare mandibular shapes derived from lateral cephalographs of patients with various anomalies. This technique centers on defining the central (medial) axes of mandibular form and is based on equal weighting of points defining the peripheral border independent of cephalographic orientation. Measurement of the derived medial axes and their relative orientation described marked changes in mandibular shape resulting from pathosis and surgical intervention. However, further research is required to ascertain whether this specific technique for the description of biologic shape facilitates orthognathic surgical diagnosis and planning.