Comparative analysis of the gonial angle on lateral cephalometric radiographs and panoramic radiographs.

We measured the gonial angle (GA) on panoramic radiography (PR) and analyzed the correlation between the GA on PR and lateral cephalometric radiography (LCR). In total, 49 PR films and LCR films from dentate young adults were evaluated. Orthodontists plotted four points (articulare, menton, posterior gonion, and lower gonion) on the PR and carefully traced them. Using a protractor, two radiologists measured the GA on LCR images. A simultaneous experimental study of two dry skulls was performed to compare the GA on LCR and PR. The GA was slightly smaller on the PR of the dry mandible than on the LCR and tended to decrease continuously with magnitude toward the Frankfort horizontal plane. The mean GA was 115.1 ± 5.2° on PR and 122.2 ± 6.4° on the LCR. The values were highly correlated (Pearson product-moment correlation coefficient, 0.801). The GA on PR was nonsignificantly smaller than that measured on LCR. The difference may be due to head position, the inclination angle of the mandibular body, and/or the direction of the incident X-ray beam.