Accuracy of Gonial Angle Measurement: Panoramic Radiography versus Lateral Cephalometry in Adult Class I Malocclusion

Abstract

Panoramic radiographs are more routinely taken than cephalometric radiographs in orthodontics. One of the values that can be evaluated in panoramic radiographs is the gonial angle. This study aims to investigate the accuracy of panoramic radiographs in evaluating the gonial angles obtained from lateral cephalometric radiographs and compare the results between pre and post-treatment, moreover, on both sides, right and left of the mandible in adult patients diagnosed with Class I malocclusion, and to find a possible correlation of gonial angle measurements between the panorama and lateral cephalometric radiographs. Gonial angles were assessed in 40 adult patients with Class I malocclusion (20 males and 20 females; average age: 23-26 years), obtained from orthodontic clinical records using both panoramic radiographs and lateral cephalograms. On lateral cephalograms, the gonial angle was determined at the intersection of the mandibular and ramus planes. On panoramic radiographs, the angle was measured by drawing one line along the inferior border of the mandible and another line along the posterior border of the ascending ramus on both the right and left sides. The measurements from the two radiographic techniques were statistically analyzed and compared using Pearson’s correlation coefficient and a paired t-test. No statistically significant difference was observed between the gonial angles measured on panoramic radiographs and those obtained from lateral cephalograms. Additionally, the comparison between the right and left gonial angles measured on panoramic radiographs revealed no significant difference in mean values. In contrast, measurements from lateral cephalograms demonstrated a statistically significant decrease from 127.73° ± 6.69° pre-treatment to 126.95° ± 6.99° post-treatment, representing a mean reduction of 0.775° (p = 0.014). The ICC analysis demonstrated excellent agreement, with values ranging from 0.978 to 0.992 pre-treatment and 0.987 to 0.996 post-treatment. As there was no statistically significant difference between the gonial angle measurements obtained from panoramic radiographs and those from lateral cephalograms, panoramic imaging can be reliably used in orthodontics to assess the gonial angle, offering the advantage of minimal interference from overlapping anatomical structures. Our results revealed that the gonial angle changes after orthodontic treatment remained relatively stable for a period of (10 to 12) months after orthodontic treatment.