[Clinical study of orientation and reference planes in cephalometry].

A critical study of orientation and reference planes used in cephalometrics is undergone. The data consists of cephalometric measurements evaluated in a sample of 90 young lebanese adults, divided into 43 girls and 47 boys, whose lateral cephalograms were registered according to the natural head position. This study shows the importance of the true horizontal as orientation and reference planes, due to the high reproducibility of the natural head position, and the high variability of the intra-cranial reference planes as compared to the true vertical, as well as the low correlation among measurements based on the true horizontal as a reference plane (AB-horizontal), and the measurements based on the intra-cranial planes and points (ANB) as reference. This study also evaluated the variations of some angular and sagittal measurements (SNA, SNB, SNPog) registered according to two orientations: Frankfort plane and the natural head position.