Figure 2
Cephalometric landmarks, reference planes, and linear parameters used for the evaluation of PPWT change. Landmarks: ANS, anterior nasal spine; PNS, posterior nasal spine; MSP, mid-point of soft palate (It is the intersection of PNS-U line and a line representing the maximum thickness of soft palate); U, tip of the soft palate; Go, gonion; Me, menton; SC3, superior-anterior point of C3 vertebra; IC3, inferior-anterior point of C3 vertebra. Reference planes: 1a. palatal plane (ANS-PNS); 2b. mandibular plane (Go-Me); 3c. anterior tangent to C2 vertebra, tangent drawn along the anterior border of C2 vertebra; 4d. long axis of the soft palate (PNS-U). Linear parameters: 1. PPWT1, the distance from the intersection point of palatal plane and posterior pharyngeal wall to the intersection point of palatal plane and anterior tangent of C2 vertebra; 2. PPWT2, the distance from the intersection point of line parallel to the palatal plane passing through ‘MSP’ and the posterior pharyngeal wall to the intersection point of same line extended posteriorly and anterior tangent of C2 vertebra. 3. PPWT3, the distance from the intersection point of line parallel to palatal plane passing through the ’U’ and the posterior pharyngeal wall to the intersection point of same line extended posteriorly and anterior tangent of C2 vertebra; 4. PPWT4, the distance from the intersection point of the mandibular plane and posterior pharyngeal wall to the intersection point of the mandibular plane and anterior tangent of C2 cervical vertebra; 5. PPWT5, the distance from the intersection point of line parallel to the mandibular plane passing through the superior-anterior point of C3 vertebra and the posterior pharyngeal wall to superior-anterior point of C3 vertebra; 6. PPWT6, the distance from the intersection point of line parallel to mandibular plane passing through the inferior-anterior point of C3 vertebra and the posterior pharyngeal wall to inferior-anterior point of C3 cervical vertebra.