Changes in growing individuals are evaluated by comparing tracings of
cephalometric radiographs taken at different times. The methods of
cephalometric superimposition differ according to the planes or anatomic
structures used as references. It is not presently known if the superimposition
method used has . any effect on growth interpretation and evaluation of
This study compa~ed four different methods of cephalometric
superimpositions on the cranial base by investigating the differences in
landmarks changes between methods. Tracings of pretreatment and
posttreatment cephalograms of 30 patients were superimposed according to the
following methods: 1-Sella-Nasion @ Sella, 2-Frankfort horizontal @ Ptv, 3-
Basion-Nasion @ CC, and 4-Basion horizontal @ Basion. Differences in the
amount of changes among the superimposition methods · were assessed
independently for the following landmarks: ANS, PNS, A point, B point,·
Pogonion, and Gonion.
The results revealed statistically significant differences (ps0.05) among
the methods for four out of the six landmarks studied. For the landmark ANS,
there was a significant difference between FH @ Ptv and the rest of the
methods. FH @ Ptv was also significantly different then SN @ S for point A
with no difference among the three remaining techniques. For points Pogonion
and Gonion, there \Vas a significant difference between FH @ Ptv and BN @ CC. Furthermore, there was a significant difference between FH @ Ptv and BN
@ CC for point Gonion.
These results show small but statistically significant differences among
the methods of superimposition. This suggests caution in interpreting the
longitudinal information from each method by a 9ommon set of guidelines. The
clinical significance of the small differences ( ~ 1.2 · mm ) in the methods is a
topic for future research.
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