Fig. 6

The demography of transverse measurements on the upper first molar. A: measured when the FH plane was parallel to the floor; B: Linear and angular measurements of upper first molar on the coronal CT image. A-B: U6-AC; C-D: U6-MR; M1-M2: U6-IM; (AB-A’B’)/2: U6-BLW; (CD-C’D’)/2: U6MR-BLW; 1: ∠16/Sagittal; 2: L: ∠46/Sagittal; C: measured when the OP was parallel to the floor; D:on the axial section of maxillary arch, the coronal slide was defined as a line (green line) connecting the midpoint of the mesiodistal occlusal crown width of bilateral first molars; E: the long axis of upper first molar was defined as a line (yellow line) passing through the midpoint of the buccal and lingual cusp tips and the midpoint of the buccolingual width at the cervical base close to the furcation of the anatomic crown. The BLI of the tooth was the angle formed by the long axis of molar and true vertical line