Objectives:

To compare the differences in gonial angle measurements on panoramic and lateral cephalometric radiographs. Furthermore, to evaluate if skeletal classes I, II and III influence the measurement in those radiographs.

Methods:

A cephalometric evaluation of 60 patients (38 females and 22 males) from the Institute of Orthodontics of the Faculty of Medicine of the University of Coimbra was performed. Patients were divided into three groups corresponding to classes I, II and III. In cephalograms, the gonial angle was measured at the intersection of the ascending ramus line and the mandibular plane. In panoramic radiographs, it was measured at the intersection of two lines: the tangent to the inferior border of the mandible and the tangent to the distal border of the ascending ramus and the condyle on both sides. The differences between radiographs were assessed with the ANOVA test, assuming a 0.05 level of significance.

Results:

The mean gonial angle value was 127.30 ± 8.5 degrees on panoramic radiographs and 128.28 ± 7.8 degrees on lateral cephalograms. The three skeletal classes achieved a strong agreement between measurements. Differences were also observed between skeletal classes, particularly between classes I and III (p=0.007) and classes II and III (p=0.036).

Conclusions:

Panoramic and cephalometric radiographs are both a viable method to assess the gonial angle, regardless of the skeletal pattern. The gonial angle value may vary according to the skeletal pattern.

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