Identification of the cephalometric reference point condylion on lateral head films.

The tracing error of the cephalometric reference point condylion was studied in two groups of children with the mean ages 11 and 13 years. Two lateral cephalograms of each subject were available. The first film had been taken according to the standard method with the teeth in habitual occlusion, and the other with the mouth open to maximum extent. The condylion was registered on all films on two occasions with an interval of one month. The distance condylion-prognathion (mandibular length) was also recorded. The tracing error was found to be significantly greater when the condylion was located on occlusion films as opposed to open mouth films. The greatest precision of an individual measurement of mandibular length was, therefore, achieved on open mouth films. For group means, however, there was no significant difference between occlusion and open mouth films.