A Cephalometric Study of Various Horizontal Reference Planes in Natural Head Position

Various intra and extracranial cephalometric horizontal reference planes have been used to formulate diagnosis and plan individualized treatment for an integrated correction of the malocclusion. Aim: The aim of this study was to evaluate variability of intracranial reference planes, i.e sella-nasion, basion-nasion, Frankfurt horizontal, functional occlusal, mandibular and maxillary-mandibular bisector planes, in relation to the true horizontal plane in natural head position and their relationship to each other. Materials and methods: For the present study, 100 subjects (50 males and 50 females) were selected between the age group of 17 and 25 years having pleasing profile with competent lips with Angle’s Class I molar relationship and normal overjet and overbite with no history of taking any form of orthodontic treatment. Results: The data collected was statistically analyzed. Pearson’s correlation coefficient to quantify the strength of association between the pairs of angular variables was calculated. Their significance, i.e. p-value was set at p < 0.001. Reproducibility for natural head position over a 2-month period was quantified by measuring the difference between the variable Frankfurt horizontal/ true horizontal at initial (T1) and second (T2) recordings of the randomly selected subjects (n = 10). Significance for statistical test was set at p < 0.05. The results inferred on studying the data for intraindividual natural head position reproducibility was that the reproducibility was less variable (more reliable) than the interindividual variability of craniofacial reference planes related to horizontal plane. Conclusion: Among all the reference planes studied, the Frankfurt horizontal plane was closest to the true horizontal and thus could be recommended as a reference plane, when radiographs were not recorded in natural head position.