pISSN 2234-7518
eISSN 2005-372X

Definition of the planes and the measurements

Planes and measurements Definition
Planes
Sella-Nasion plane A plane passing through point sella and point nasion
Nasion-A plane A plane passing through point nasion and point A
Nasion-B plane A plane passing through point nasion and point B
Mandibular plane A plane passing through point gonion and point menton
Horizontal reference plane (RP1) RP1 was drawn with a 7 degree below the sella-nasion plane at point sella
Frankfort horizontal plane (FHP) A plane passing through orbitale and porion points
Nasion perpendicular (N⊥) A plane passing through nasion point to chin and perpendicular to FHP
Measurements
SNA (°) The angle between sella-nasion and nasion-A point planes
SNB (°) The angle between sella-nasion and nasion-B point planes
ANB (°) The angle between nasion-A point and nasion-B point
FMA (°) The angle between the FHP and mandibular plane
RP1-PNS (mm) The vertical distance from posterior nasal spine point to RP1
S-Go (mm) The vertical distance between sella and gonion points
RP1-A (mm) The vertical distance from A point to RP1
N⊥A The linear distance from A point to nasion perpendicular
Ad1-PNS (mm) The linear distance measured between posterior nasal spine and posterior pharyngeal wall along the line of basion point to posterior nasal spine
Ad2-PNS (mm) The linear distance measured between posterior nasal spine to the adenoid tissue along the line from posterior nasal spine to the midpoint of the line intersecting basion to sella turcica
Posterior airway space (PAS) (mm) The anteroposterior depth of the pharynx measured between the posterior pharyngeal wall and the posterior nasal spine on a line parallel to the FHP through the posterior nasal spine
Superoposterior airway space (SPAS) (mm) The linear distance measured between the posterior pharyngeal wall and the dorsum of the soft palate on a line parallel to the FHP through the middle of the line from the posterior nasal spine to the tip of the soft palate
Middle airway space (MAS) (mm) The linear distance measured between the posterior pharyngeal wall and the dorsum of the tongue on a line parallel to the FHP through the tip of the soft palate
Inferior airway space (IAS) (mm) The linear distance measured between the posterior pharyngeal wall and the surface of the tongue on a line parallel to the FHP through the most anteroinferior point on the body of the second cervical vertebra
Epiglottic airway space (EAS) (mm) The linear distance measured between the posterior pharyngeal wall and the surface of the tongue on a line parallel to the FHP through the epiglottis tip
Korean J Orthod 2023;53:35~44 https://doi.org/10.4041/kjod22.117
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