Orientation-sella-nasion or Frankfort horizontal.

The controversy regarding the most appropriate line for cephalometric orientation has been resolved and can be summarized in the following five areas of consideration: 1. Clinical significance. The ability of the clinician to visualize the Frankfort horizontal plane affords him the opportunity for effective clinical communication, which is lacking with sella-nasion. In addition, he is able to demonstrate the orientation of the face, chin, and palate to Frankfort horizontal plane, which is also lacking in the sella-nasion system. 2. Anatomical significance. The direct relationship of the Frankfort horizontal plane with the basic sense organs of sight and hearing displays a relationship to the face. Sella, in contrast, relates to the brain and not the face. 3. Measurement accuracy. Studies performed to test the accuracy of selection of the planes under consideration showed no significant differences when true porion and not the ear rod was used and when experienced technicians performed the tracings. 4. Application in description. If the reference line is to be considered reliable for description, the correlation between the measurements of the maxilla and the mandible to the reference line should be minimal. In a study performed, SNA and SNB displayed a significantly higher correlation than N-Po to FH and N-A to FH. 5. Application in growth forecasting. A study was performed in order to evaluate the application of these lines of orientation to growth forecasting. In every instance the reference frame which utilized the Frankfort horizontal plane was appreciably better than that which utilized sella-nasion.