The accuracy of measuring condylion location.

In locating condylion (Co), clinicians have used cephalograms in maximum mandibular opening to provide a clearer image of the condyle. The purpose of this study was to evaluate the accuracy of identifying condylin on a sample of open and closed mouth cephalograms of 20 patients. Five orthodontists traced each mandibular outline and located condylion and the tip of the mandibular incisor (I). The incisor tip was assumed to be relatively interpretable and served as an internal control. The differences between the open and closed positions in the horizontal and vertical components of condylion relative to the mandibular plane or in the length Co-Gn were not statistically significant. The absolute deviation around condylion was significantly different (p = 0.007), but the average absolute deviation of condylion in the open position was only 0.5 mm less than condylion in the closed position. Statistically significant differences also occurred in the means of the vertical component of the incisor tip (p = 0.002), the length Gn-I (p = 0.006), and the absolute deviation of incisor tip (p = 0.004). These results indicate that the open mouth method does not significantly change the location of condylion. It does increase the accuracy of landmark identification, but this increased accuracy on the average is not clinically significant.