Table 1 Definitions of 3D landmarks, planes, and measurements
From: Skeletal structure of asymmetric mandibular prognathism and retrognathism
Annotation | Definition |
|---|---|
Landmarks | |
Na | The midpoint of the frontonasal suture |
S | The center of the hypophyseal fossa (sella turcica) |
Or | The orbitale. Bilateral landmark |
Pog | The hard tissue pogonion |
Por | The porion. Bilateral landmark |
Por_center | The geometric mean of left and right porion. Bilateral landmark |
A-point | The hard tissue A-point |
B-point | The hard tissue B-point |
C_point | The most caudal point of the sigmoid notch. Bilateral landmark |
Con_ant | The most anterior point of the condyle. Bilateral landmark |
Con_post | The most posterior point of the condyle. Bilateral landmark |
Con_AP_center | The transverse geometric center of the condyle (between Con_ant and Con_post). Bilateral landmark |
Con_cranial | The most cranial point of the condyle. Bilateral landmark |
Con_dorsal | The dorsal point of the condyle at the intersection with C-plane. Bilateral landmark |
Con_lat | The most lateral point of the condyle. Bilateral landmark |
Con_med | The most medial point of the condyle. Bilateral landmark |
Cor | The tip of the coronoid process. Bilateral landmark |
Me | The most inferior midpoint of the chin at the mandibular symphysis. Hard tissue menton |
Go | The most posterior and inferior point of the mandibular angle. Bilateral landmark |
Reference planes | |
FH Plane | A plane through landmarks right and left Or and Por_Center |
Horizontal reference plane(HRP) | The Horizontal (x) 3-D Cephalometric Reference Plane is automatically computed as a plane 6 degrees below the Anterior Cranial Base (S-Na) plane, through S |
Midsagittal plane (MRP) | The Median 3D Cephalometric Reference Plane is computed as a plane through S and Na and perpendicular to the HRP |
Coronal reference plane (CRP) | The Vertical 3D Cephalometric Reference Plane is computed as a plane through S and perpendicular to the HRP and MRP |
MP | Mandibular plane. A plane through landmarks right Go, left Goand Me. Bilateral plane |
C-plane | A plane through landmark C_pointand parallel to FH plane. Bilateral plane |
Condyle_sag_plane | Condyle sagittal plane, a plane through Con_center, Con_dorsal and C_point. Bilateral plane |
Ramus_sag_plane | Ramus sagittal plane, a plane through landmarks C_point, Con_dorsal and Go. Bilateral plane |
Linear measurements (mm) | |
Me deviation | The distance from landmark Me to MRP |
Chin height | The height between landmarks B-point and Me (i.e. distance between the two landmarks along the y-axis of the reference frame) |
Condylar width | The distance between the most medial and lateral point of the condyle (Con_med to Con_lat). Bilateral measurement |
Condylar height | The height between landmarks Con_cranial and Con_dorsal (i.e., distance between the two landmarks along the y-axis of the reference frame). Bilateral landmark |
Ramus-proper height | The height between landmarks Con_dorsal and Go (i.e., distance between the twolandmarks along the y-axis of the reference frame). Bilateral landmark |
Ramus length | The distance from Con_cranial to Go. Bilateral measurement |
Body length | The length of left mandibular body (Go to Me). Bilateral measurement |
Con_AP | The anterio-posterior depth between landmark Con_sag_mean to N vertical from lateral view. Bilateral measurement |
Con_vert | The vertical distance between landmark Con_cranial to N along the x-axis of the reference frame (The vertical distance between condyle_cranial and axial plane at N). Bilateral measurement |
Con_transv | The distance from landmark Con_cranial to MRP. Bilateral measurement |
Go_AP | The anterio-posterior depth between landmarks Go and N vertical (i.e., distance between the two landmarks along the x-axis of the reference frame). Bilateral measurement |
Go_vert | The height between landmarks N and Go (i.e., distance between the two landmarks along the y-axis of the reference frame). Bilateral landmark |
Go_transv | The distance from landmark Go_to plane MRP |
Angular measurements (°) | |
SNA | The angle between the projection of the landmarks S–N-A-point on MRP |
SNPog | The angle between the projection of the landmarks S–N-Pog on MRP |
MPA | Mandibular plane angle, the angle between the line S–N and the MP |
Axial condyle rotation (yaw) | The 3D angle between plane Condyle_sag_plane and CRP. Rotation of condylar-sagittal plane relative to CRP from bird’s eye view. Bilateral measurement |
Frontal condyle inclination(roll) | The 3D angle between plane Condyle_sag_plane and HRP. Coronal rotation of left condylar-ramus sagittal plane with regard to HRP from frontal view. Bilateral measurement |
Axial ramal rotation (yaw) | The 3D angle between plane Ramus_sag_plane and CRP. Bilateral measurement |
Frontal ramal inclination (roll) | The 3D angle between plane Ramus_sag_plane and HRP. Bilateral measurement |
Sagittal ramal inclination (pitch) | The angle between the projection of the lines posterior ramus (Con_dorsal to Go) on medial plane and S–N from the lateral view. Bilateral measurement |
Gonial angle | The angle between the projection of the lines Con_dorsal-Go and Go-Me on MRP. Bilateral measurement |