Table 1. Definitions of landmarks.

Symbol	Definition
Gn (gnathion)	The midpoint between the most anterior and inferior points on the outline of the mandibular symphysis
A(subspinale)	The most concave point on the bone between the anterior nasal spine point and superior prosthion point.
UI (upper incisor)	The most anterior point on the incisal edge of the upper incisor
H (hyoid)	The most anterior and inferior point of the hyoid bone
C3 (third cervical vertebra)	The anterior and inferior point of the third cervical vertebra
Me (menton)	The most inferior point on the outline of the mandibular symphysis
CSA(cross-sectional area)	The cross-sectional area of the upper airway on each CBCT sagittal plane