New 3-dimensional cephalometric analysis for orthognathic surgery.

Two basic problems have been associated with traditional 2-dimensional cephalometry. First, many important parameters cannot be measured on plain cephalograms; and second, most 2-dimensional cephalometric measurements are distorted in the presence of facial asymmetry. Three-dimensional cephalometry, which has been facilitated by the introduction of cone-beam computed tomography, can solve these problems. However, before this can be realized, fundamental problems must be solved. These include the unreliability of internal reference systems and some 3-dimensional measurements, and the lack of tools to assess and measure the symmetry. In the present report, we present a new 3-dimensional cephalometric analysis that uses different geometric approaches to solve these fundamental problems. The present analysis allows the accurate measurement of the size, shape, position, and orientation of the different facial units and incorporates a novel method to measure asymmetry.