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

Gonial angle (GA) is one of the essential angles that is used in orthodontic treatment plans. It is often evaluated by lateral cephalometry, but because of its overlap of right and left structures, a lack of different magnifications on two sides, and strength of panoramic radiography in angular measurements, it was decided to compare panoramic radiography and lateral cephalometry for determining GA in patients referring to dental clinic of Guilan University of Medical Sciences (GUMS) in 2017 and 2018.

The study samples included Lateral cephalograms and panoramic radiographs of 391 patients (215 females and 176 males) with an age range of 6-40 years. In both methods, GA was determined based on two tangents drawn from the inferior border of the mandible and posterior borders of condyle and ramus of both sides. The values of the studied parameters were compared using paired t-test.

The mean value of the GA in lateral cephalogram was 119.07°±7.88° and the mean value of GA in panoramic radiography was 116.36°±8.20°. The difference of GA measurement between the two methods was statistically significant. Moreover, a similar significance was observed in the measured GA with respect to gender and skeletal classifications.

The difference of GA measurements obtained from lateral cephalograms and panoramic radiographs were found to be statistically significant. Thus, panoramic radiography would not be an alternative for lateral cephalometry in determining GA and it is suggested to be used only for the preliminary diagnosis.