Effect of magnification on lateral cephalometric studies.

The effect of radiographic magnification on the horizontal distance sella-nasion, the vertical distance nasion-menton, and the oblique distance sella-gnathion was explored. Five different longitudinal cephalometric studies provided the data for this survey. Two series of graphs were created: 1 from the raw data as they originally were published, the other in natural size after meticulous compensation for radiographic magnification. The importance of correction for magnification at once became obvious when these graphs were reviewed. The following conclusions were made: the distances listed in commonly used cephalometric atlases differ greatly because of different magnification and cannot be compared directly. The distances from the Ann Arbor, Michigan, study must be multiplied by 0.886, and those from the Bolton Standards and the Philadelphia studies must be multiplied by 0.943 to obtain natural dimensions. Correction to natural size is essential when comparing cephalometric distances from different sources; publication of data corrected to an arbitrary "standardized enlargement" creates confusion. Although differences between the corrected distances were small, regional variation seems to exist.