Discrepancies in cephalometric measurements in relation to natural head position

Resumen

The objective of this study was to determine the cephalometric discrepancy of some reference planes and angles in relation to the natural head position. 78 patients were admitted at the Orthodontic Service of the Mexico Children’s Hospital and 2 lateral X-rays were taken from the skull of each patient. The fi rst radiograph was in natural position. The patient positioned his head in a relaxed way looking into the horizon, with slightly separated legs, arms resting at the sides of the body, lips at rest. The second radiograph (assisted) was taken with the above mentioned parameters and without the olives pressing the external auditory meatus. A 4 x 8 cm to 1.5 m mirror was given to each patient of so that they could look into it with his or her pupils focused in the eye center and a plummet placed on the chassis of the plate (representing the true vertical) plus a profi le photograph with the same indications. The measurements in both plates were traced, measured and compared. We considered the random error with a standard deviation of 0.4 mm, Houston’s.1 Results: We found a statistically signifi cant difference (p = 0.004) between the Frankfort plane and the true horizontal and (p < 0.005) between nasion perpendicular to point A and between subnasal vertical to pg’ in relation to the Frankfort plane and to the true horizontal unlike facial depth (p = 0.545).

Key words: Frankfort plane, true horizontal plane, natural head position and natural head posture.