Plane-based gonial angle segmentation contributes to mandibular growth direction assessment: a retrospective longitudinal study

his longitudinal study investigated the correlation between changes in four pairs of gonial angle components and changes in skeletal indicators during development and functional orthodontic treatment or orthopedic treatment. This study included 255 individuals aged 6–15 years who had two lateral cephalometric films taken at intervals of 6 months to 2 years. The 104 patients without treatment composed the observation group, and the 151 patients with functional orthodontic treatment or orthopedic treatment composed the treatment group. We measured four pairs of segmentation-based gonial angle components, including FH-based segmentation (Ar-Go’-VFH/Me-Go’-FH), SN-based segmentation (Ar-Go’-VSN/Me-Go’-SN), Go’-S-based segmentation (Ar-Go’-S/Me-Go’-S), and Go’-N-based segmentation (Ar-Go’-N/Me-Go’-N). Pearson’s correlation analysis was used to investigate the correlation between the changes in segmentation components and changes in clinical indicators. There were correlations between changes in the sagittal and vertical gonial angle components and changes in the skeletal indicators, with greater correlations for the plane-based segmentation components in both the observation and treatment groups. The correlations were greater in the treatment group than in the observation group. Moreover, the sagittal gonial angle components Ar-Go’-S might represent changes in the position of the condyle in the sagittal direction. Plane-based gonial angle segmentation was better representative of mandibular growth and development. The change in gonial angle components in the treatment group was more representative of the change in skeletal indicators than that in the observation group.