A comparison of three superimposition methods.

The purpose of this investigation was to compare the reliability of three superimposition methods: Björk's structural, Ricketts' four-position, and Pancherz's method. The material consisted of 14 pairs of cephalograms obtained before and after Herbst treatment. Each pair of cephalograms were traced and superimposed by means of the three different methods three times each. A reference grid was used to quantitatively evaluate the sagittal dental and skeletal changes. The results revealed that: (1) there was no statistically significant difference between the repeated measurements in the three methods, i.e. all three methods were reliable. (2) There was no significant difference among the three superimposition methods to evaluate the sagittal skeletal and dental changes. (3) Comparing the coefficient of reliability, none of the three methods was suitable for individual assessment, and Pancherz's method only was acceptable for assessment of patients in groups.