Figure 1From: Effects of twin-block appliance on the anatomy of pharyngeal airway passage (PAP) in class II malocclusion subjects Cephalometric landmarks, reference planes, and linear and angular parameters. Cephalometric landmarks, reference planes, and linear and angular parameters used for evaluation of skeletal and PAP dimension changes. Landmarks: S, sella; N, nasion; Po, porion; Or, orbitale; Go, gonion; A, Point A; B, Point B; Pog, pogonion; Gn, gnathion; Me, menton; ANS, anterior nasal spine; PNS, posterior nasal spine; Ptm, pterygomaxillary fissure; Ba, basion; Co, condylion; U, tip of soft palate; UPW (upper pharyngeal wall), the intersection of line Ptm-Ba and posterior pharyngeal wall; MPW (middle pharyngeal wall), the intersection of perpendicular line on Ptm perpendicular from ‘U’ with posterior pharyngeal wall; V, vallecula; and LPW (lower pharyngeal wall), the intersection of perpendicular line on Ptm perpendicular from ‘V’ with posterior pharyngeal wall. Reference planes: SN plane, the line joining ‘S’ and ‘N’; FH plane, line joining ‘Po’ and ‘Or’; Ptm perpendicular (Ptm per), perpendicular plane on FH plane at ‘Ptm’; and Ba-N plane, line joining ‘Ba’ and ‘N.’ Linear parameters: 1. maxillary length (ANS-PNS); 2. effective maxillary length (Co-A); 3. mandibular length (Go-Pog⊥MP); 4. effective mandibular length (Co-Gn); 5. DNP (Ptm–UPW); 6. HNP, the shortest linear distance from PNS to Ba-N plane; 7. DOP (U–MPW); 8. DHP (V–LPW); 9. SPL (U–PNS); 10. SPT, the maximum thickness of the soft palate. Angular parameters: 11. SNA, angle between ‘S,’ ‘N,’ and ‘A’; 12. SNB, angle between ‘S,’ ‘N,’ and ‘B’; 13. FMA, angle between FH plane and mandibular plane (Go-Me); 14. SPI (Ptm per × PNS-U), the angle between Ptm perpendicular and the soft palate (PNS-U).Back to article page