Does the chin projection and sella point position affect the W angle reliability?

Purpose: The purpose of this study was to compare the reliability and validity of the Sella (S) and G points used in the W angle for different types of malocclusions. Materials and methods: Pretreatment cephalometric radiographs of 700 individuals aged 15 to 25 years, who began orthodontic treatment between 2019 and 2024, were randomly selected from the archives of the Department of Orthodontics at Afyonkarahisar Health Sciences University. After applying exclusion criteria, 570 radiographs (290 females, 280 males) were included in the study. These radiographs were divided into three groups based on ANB and Wits values: Class I (C1) (n = 103), Class II (C2) (n = 178), and Class III (C3) (n = 111). Each group was further divided into nine subgroups according to chin projection (low [a1], normal [a2], high [a3]), the vertical position of the sella point (low [b1], normal [b2], high [b3]), and the sagittal position of the sella point (low [c1], normal [c2], high [c3]). The vertical position of the sella point was determined by calculating its distance from the FH plane, while its sagittal position was assessed by measuring the distance of its projection onto the FH plane relative to the orbitale point. Chin projection was determined using the Pg-NB measurement. Results: Statistical analysis showed that chin projection was positively correlated with the W angle in all subgroups (p < 0.001). The sagittal position of the sella point did not significantly affect the W angle in any of the classes. However, the vertical position of the sella point was positively correlated with the W angle only in the subgroups with high vertical values (C1b3, p = 0.002; C2b3, p < 0.001; C3b3, p < 0.001). Conclusion: Both chin projection and the vertical position of the sella point were found to influence the W angle, whereas the sagittal position of the sella point did not have a significant effect.