Figure 2. A, Linear and angular measurement for hard palate morphology and the first molar. 1 and 2, Measurement of palatal length, width, and height; 3, the width of the nasal cavity and the angle of the first molar palatal root on the first molar coronal plane; 4, the palatal slope inclination and the width of the palate roof (upper width) on the first premolar and first molar coronal plane. B, The three-dimensonal (3D) surface set up using generalized additive models with integrated smoothness estimation based on the cone-beam computed tomography (CBCT) data set. 1, ANS-PNS was divided into 14 pieces in the sagittal section; 2, in each coronal section corresponding to these 14 pieces, along the contour line of the palatal bone, 8 points were chosen; 3, in total, 113 points were chosen for establishing the 3D surface of palatal bone; 4 and 5, 3D surface of palatal bone. C, A nonlinear curve approximation model of the palatal bone contour line in the first premolar (1), first molar (2), palatal suture (3), and palatal undersurface section (4) were set up based on the CBCT data set.