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).