Abstract: PURPOSE: To explore the clinical value of 3D computed tomography (CT) reconstruction in the prognostic evaluation of orthodontic treatment for patients with skeletal Class Ⅱ malocclusion. METHODS: A total of 48 patients with skeletal Class Ⅱ malocclusion who received orthodontic treatment at the Department of Stomatology, Baoji People's Hospital from January 2022 to January 2023 were selected. All patients underwent CBCT scans 1 week before treatment (T0), 1 month after treatment(T1) and 6 months after treatment(T2). 3D Slicer software was used for modeling, and Geomagic Qualify software was utilized for fitting alignment and measuring the three-dimensional movement distances of various landmarks on the maxilla and mandible. The coordinates of the landmarks at T1 and T2 were compared and analyzed. Pearson correlation analysis was used to determine the correlation between significant relapse landmarks. SPSS 19.0 software package was used for statistical analysis of the data. RESULTS: One month and six months post-treatment, changes in the horizontal coordinate of landmark Rgo and changes in the anteroposterior coordinates of landmarks A, RP, B, Pog, Gn, Me, Rgo and Lgo, as well as changes in the vertical coordinate of Gn were statistically significant(P<0.05). Correlation analysis revealed a positive correlation between the horizontal movement distance of landmark Rgo from T1 to T0 and the relapse distance(r=0.293, P=0.043). There was a positive correlation between the anteroposterior movement distance of landmark A from T1 to T0 and the relapse distance(r=0.418, P=0.003), a positive correlation between the movement distance of RP from T1 to T0 and the relapse distance (r=0.470, P=0.001), a negative correlation between the movement distance of B from T1 to T0 and the relapse distance(r=-0.523, P=0.000), and a negative correlation between the movement distance of Pog from T1 to T0 and the relapse distance(r=-0.391, P=0.006). CONCLUSIONS: Three-dimensional CT reconstruction can provide precise three-dimensional quantitative analysis for the prognostic assessment post-orthognathic surgery in patients with skeletal Class Ⅱ malocclusion. It helps identify landmarks with a high risk of relapse, thus providing more targeted postoperative treatment and monitoring strategies for clinical practice.

Key words: Three-dimensional CT reconstruction, Skeletal Class Ⅱ malocclusion, Orthodontics, Prognostic assessment, Relapse risk