The Impact of Gonial Angle on Skeletal Class II Division 1 Malocclusion: A Cephalometric Study

Abstract

The gonial angle plays a crucial role in craniofacial morphology and directly affects mandibular positioning and growth patterns, and overall mandibular shape. This study aims to analyze the relationship between the gonial angle and skeletal class II division 1 malocclusion, emphasizing its impact on skeletal discrepancy between the maxilla and the mandible, both horizontally and vertically. A total of 116 lateral cephalographs 56 males and 60 females of Libyan White Ancient population patients diagnosed with skeletal class II division 1, were analyzed using Dr.Ceph software (Fytik Co.) Eighteen skeletal measurements were assessed, with focus on the gonial angle (Ar-Go-Me) and correlation with ANB, SNB, and mandibular plane angle(SN-MP). Statistical analysis was done using SPSS 12.0 software (Lead Technology Co.). The measurement of the study sample was compared with the normal values of the Libyan population, including Pearson correlation analysis and t-tests to determine the significance of gonial angle effects. The results showed a significantly larger gonial angle observed in patients with class II Div1 malocclusion compared to normal cephalometric values for Libyans (p<0.01). The gonial angle demonstrates a positive correlation with ANB (r=0.287, p-0.002) and mandibular plane angle (r=0.352, p<0.001), and a negative correlation with SNB 9r=-0.297, p=0.001). These findings suggest that the increased gonial angle is associated with mandibular retrusion, steeper mandibular plane, clockwise (downward) rotation of the mandible, and increased lower facial height leading to a more pronounced class II skeletal relationship.