The authors studied possible influences on angular and vertical linear measurements of the Frankfort Horizontal Plane (FHP) when used as an orientation plane in posteroanterior cephalometric radiographies. Ninety posteroanterior cephalometric radiographies were used, obtained from thirty patients in three positions: FHP parallel to the Horizontal Plane, FHP forming angles of plus and minus five degrees with the Horizontal Plane. After statistical treatment, five out of the six angular measurements and three out of the eleven vertical linear ones did not show statistically significant differences at a five percent level, in spite of the inclinations. The authors concluded that, in cases of inclination of the plane of orientation in posteroanterior cephalometric radiography, the angular measurements are more reliable than the vertical linear ones. As to the anatomic coronal planes, on which are located the cephalometric points considered for the measurements, the vertical linear measurements proved to be highly sensitive to the inclinations when the coronal planes are not quite close, and the angular measurements present only loss of reliability when the cephalometric points are on coronal points quite distant.
Radiography, dental; Cephalometric
