Análisis de la variabilidad y coincidencia diagnóstica de los planos Sella-Nasion y de Frankfurt respecto a la horizontal verdadera en posición natural de la cabeza

The aim of this study was to investigate the variability of intracranial and extracranial planes in natural head position (NHP) using photographic and radiographic records. In the first part of the study, the reproducibility of NHP and variability of Frankfort horizontal (FH) and Sella-Nasion (SN) planes with respect to the true horizontal (TH) in NHP were evaluated. The results showed good reproducibility of NHP in photographic records (Dahlberg's coefficient 1.60). The FH showed lower variability than the SNplane, with variances of 4.59 and 10.12, respectively. In the second part of the study, the agreement among cephalometric variables based on the three planes evaluated (FH, SN, TH) was assessed. For the upper maxilla, the Wilcoxon test was significant for variables based on the FH-TH and FH-SNplanes and was non-significant for variables based on SN-TH. For the mandible, the Wilcoxon test for repeated measures was significant for all the variables based on the three planes. Although variability was higher for the SNplane than for the TH plane, diagnostic agreement was better between the SNand TH planes. The FH plane was found to be reliable but showed the lowest diagnostic agreement.