Porion and condyle as cephalometric landmarks--an error study.

With the recent increase in the use of functional appliances for orthodontic treatment in which condylar growth plays an important role in the final results, orthodontists and researchers should be aware of the process of growth and development of various components of the skull to see the changes of measurements on cephalometric tracings in different stages of treatment. This study was conducted to assess the reliability of the porion and condyle on the lateral cephalogram. A group of 24 patients was selected randomly from the Orthodontic Department at Tufts University. Two sagittal roentgenograms, one in habitual (centric) occlusion and one with the mouth wide open, were taken. Each cephalogram was traced by two observers to determine discrepancies in tracing the shape and position of the porion and condyle. The Pearson product-moment coefficient of correlation was performed for inter- and intraobserver reliability for locating the porion and condyle in open- and closed-mouth positions. It was concluded that the porion and condyle cannot be located accurately and consistently on sagittal roentgenograms in the closed-mouth position. Therefore it appears advisable to obtain an open-mouth cephalogram and superimpose it onto the respective closed-mouth cephalogram. This will provide greater accuracy and reliability in obtaining cephalometric measurements.