The reliability and variability of SN and PFH reference planes in cephalometric diagnosis and therapeutic planning of dentomaxillofacial malformations.

Various interpretations of clinical and cephalometric data lead to different diagnostic and surgical planning in the study of dentoskeletal malformations. Many authors have identified this discrepancy as an incorrect positioning between the skeletal structures and the Frankfurt plane (PFH)--a plane that is used routinely for the sagittal measurement of the upper and lower jaw. The aim of this study was to establish a control method to verify the correct positioning of the sella-nasion point plane (SN) and the PFH. To find a reference plane, the authors concentrated their attention on measuring the intersecting angles between these two planes and the vertical posterior maxillary (PM) plane. Fifty patients (33 women and 17 men), all of whom were aesthetically and structurally harmonious class I dentoskeletal types, were analyzed using this method. Student's t-test, the Kolmogorov-Smirnov test, and Fisher's F-test were used for statistical analysis. The results were compared with those proposed by the University of Michigan. To achieve a correct diagnosis and to obtain good functional and cosmetic results in the treatment of these kinds of malformations, it is necessary to make use of the PM vertical plane during cephalometric analysis.