Abstract

The historical development of cranial reference lines, basic to cephalometric orientation, was discussed. The evolution to, away from, and back again to the Frankfort horizontal plane for descriptive and communicative purposes as benefits to the clinical orthodontist was explained. Objectives were set forth as a basis for selecting the most appropriate method in orienting the headplate for measurement and assessment. The major functions of cephalometrics were pointed out to be its use for description or classification of the face together with the malocclusion and for superimpositioning for longitudinal comparison. Each of these purposes calls for particular requirements pointing to the need for combinations of planes and multisuperimposing. The statistical findings via a computer pointed to the use of the Frankfort plane as the most desirable basic reference for descriptive reasons. Composites also suggested good order from Frankfort horizontal when serial tracings were compared. It was emphasized that true porion was used, not the ear rod of the cephalometer. For growth analysis the basion-nasion plane was shown to be longitudinally of superior value for chin behavior.