Variation in Cephalometric Reference Lines

Abstract

The use of intracephalic reference lines in cephalometric assessment is valid only if these lines bear some constant relationship to the true horizontal and to each other. Otherwise, the use of a true horizontal would give the benefit that cephalometric assessment would be based on the same standards as clinical judgment. In using a true horizontal, however, the radiograph must be taken with the head in a reproducible natural posture. A study was carried out to assess the reproducibility of a natural head posture using a simple positioning method in a standard cephalostat, and to assess the variation in the relationship of the sella-nasion, Frankfort, maxillary and mandibular reference lines, to a true horizontal and to each other. Though in their mean inclinations the Frankfort and the maxillary reference lines were almost parallel to each other and to the true horizontal, the range of variation for all the reference lines was considerable. The range of variation in the reference lines was greater than the error of reproduction of head position, and the range of variation of the slope of the mandibular line was no greater than that for the slope of each of the other three lines. The sella-nasion line was reproduced more accurately that the other reference lines, using a digitizer. The possibilities of a simple cephalometric analysis based on a true horizontal are outlined.

Reliability and Reproducibility of Natural Head Position: A Cephalometric Study

“…[2][3][4]24 They clearly exceed the standard deviations of HOR in NHP (1.46°). The difference between mean value of SN/HOR in MP I (8.452°) and MP II (7.581°) is only 0.87°.…”

“…7 The search for an alternative lead to NHP, which showed better stability and reproducibility. [1][2][3][8][9][10] Moreover, NHP was seen to describe dentofacial and profile features of the subject in the head plate as they appear in real life.…”

“…Two most widely used reference planes, viz, Frankfort plane (FH plane) and S-N plane have been found to vary considerably in their inclination, which prompted second thinking among orthodontists regarding their very use in cephalometric diagnosis and treatment planning. [2][3][4][5][6] These conventional intracranial reference planes were found to vary over time, within individuals, depending on various factors. 7 The search for an alternative lead to NHP, which showed better stability and reproducibility.…”

Turkish Norms of McNamara's Cephalometric Analysis

“…Individual variations in the slope of intracranial reference lines may result in different interpretations of the craniofacial structure of subjects with similar profiles. [26][27][28][29] 2. Variations in the relationships between reference lines may result in different evaluations of facial skeletal patterns depending on the particular reference plane used.…”

“…Variations in the relationships between reference lines may result in different evaluations of facial skeletal patterns depending on the particular reference plane used. [29][30][31][32] 3. An evaluation of craniofacial structure by means of intracranial reference lines does not always reflect the clinical appearance of the individual subject.…”