Cone beam computed tomographic evaluation of pharyngeal airway in North Indian children with different skeletal patterns

Table 2 Two-dimensional cephalometric variables, cross-sectional planes and volumes of the 3-dimensional pharyngeal airway

Two-dimensional cephalometric variables
(1) Gonial angle: Angle formed between line drawn tangent to the lower border of the mandible and another line tangent to the distal border of the ascending ramus and the condyle on both sides; (2) Anterior facial height (AFH): Distance between the Nasion and Menton (Me); (3) Posterior facial height (PFH): Distance between Sella (S) to Gonion(Go); (4) PFH/AFH: Ratio of AFH and the PFH; (5) FMA: Frankfurt Mandibular Plane Angle formed by the intersection of the Frankfort horizontal plane and the mandibular plane; (6) ANB: The angle formed between point A, Nasion and Point B; (7) Facial convexity: Formed by the intersection of line from Nasion to point A, to point A to pogonion(Po); (8) Condylion to point A (Co-PtA); (9) Condylion to gnathion (Co-Gn); and (10) Mandibular body length (Mand-BL): Distance from gonion to pogonion
Cross-sectional planes and volumes of the 3D pharyngeal airway
Anterior nasal plane (Ana plane)	Plane passing through anterior nasal spine (ANS) and perpendicular to FH
Posterior nasal plane (Pna plane)	Plane passing through posterior nasal spine (PNS)and perpendicular to FH
Upper pharyngeal plane (Uph plane)	Plane passing through PNS parallel to FH
Middle pharyngeal plane (Mph plane)	Plane passing through lower margin of the soft palate and parallel to FH
Lower pharyngeal plane (Lph plane)	Plane passing through superior margin of the epiglottis and parallel to FH
Volume
Nasal airway	Airway formed by the planes between Ana and Pna
Superior pharyngeal airway	Airway formed by the planes between Pna and Uph
Middle pharyngeal airway	Airway formed by the planes between Uph and Mph
Inferior pharyngeal airway	Airway formed by the planes between Mph and Lph planes
Total airway	Airway extending between Ana plane to Lph plane

FH: Frankfurt horizontal; 3D: Three-dimensional.