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Table 2 Landmarks, reference planes and measurements used in the study

From: Orthodontic incisor retraction caused changes in the soft tissue chin area: a retrospective study

 Definition
Landmarks
 NNasion: most anterior point of the frontonasal suture where the lines of the glabella profile meet those of the nasal bones
 SSella: Center of bony contour of sella turcica
 PPorion: the midpoint of the upper contour of the metal ear rod of the cephalometer (machine porion)
 OrOrbitale: the lowest point on the inferior margin of the orbit
 AMost concave point between anterior nasalspine and superior prosthion
 U1The tip of the maxillary central incisors
 U1cThe most anterior point of clinical crown of maxillary central incisors
 L1The tip of the mandibular central incisors
 L1cThe most anterior point of clinical crown of mandibular central incisors
 BMost concave point on mandibular symphysis
 PogPogonion: the most anterior point on the osseous contour of the chin
 MeMenton: the most inferior midline point on the mandibular symphesis
 LLThe most anterior point of the lower lip based on the reference plane
 StmiUppermost point on vermilion border of lower lip
 B′The innermost point on the contour of the soft-tissue between the lower lip and the soft tissue chin
 Pog’Soft tissue pogonion: the most prominent point on the chin based on the reference plane
 Me’Soft tissue menton: the lowest point on the contour of the soft tissue chin
Reference planes
 FHFrankfurt Horizontal plane formed by Portion and Orbitale
 MPMandibular plane through Me and the lower margin of mandibular angle
 VBLA line passing through the B point and perpendicular to the FH plane serving as the vertical reference for the mandibular evaluations
 VNLA line passing through the N point and perpendicular to the FH plane serving as the vertical reference for the maxillary evaluations
Cephalometrics analysis index
 ANB (°)The ANB angle shows the difference between the maxilla and mandible
 SNA (°)The SNA angle is used to establish the relationship of the maxilla to the cranial base
 SNB (°)The SNB angle is used to establish the relationship of the mandible to the cranial base
 U1-L1 (°)Upper and lower central incisors Angle: the intersection Angle of the long axis of the upper and lower central incisors, representing the relative protrusion of the upper and lower central incisors
 U1-NA (°)The intersection Angle between the long axis of the upper central incisor and the NA line, representing the inclination of the upper central incisor
 L1-NB (°)The intersection Angle between the long axis of the lower central incisor and NB line, representing the inclination of the lower central incisor
 SN-MP (°)The Angle between the mandibular plane and the SN plane
 FMA (°)The Angle between the Frankfurt Horizontal plane and the Mandibular plane
 Stmi-Me’ (mm)Vertical distance between the landmarks of Stmi and Me’
Soft tissue area measurements
 Area 1 (cm2)The area of soft tissue chin from the border of B-B′ till the border of Me-Me’
 Area 2 (cm2)The area of lower lip till the border of B-B′
Soft tissue thickness measurements
 L1c-LL (mm)Distance between the landmarks of L1c and LL
 B-B′ (mm)Distance between the landmarks of B and B′
 Pog-Pog’ (mm)Distance between the landmarks of Pog and Pog’