Ceph Tracing Notes

The Major Cephalometric Landmarks

Landmark	Functional unit	Position	Tracing Tips
(S) Sella	Cranial Base	Indicates the posterior end of the anterior cranial base, located in the center of the cavity of the sella turcica	First draw the contour of the depression in the bone, extending anteriorly and posteriorly over the edges of the concavity; then mark point S in the center of the concavity. Extend your line forward along the floor of the anterior cranial base as shown (because this helps when and if you need to do superimpositions).
(NA) Nasion	Cranial Base	Indicates the front end of the anterior cranial base, and is located at the anterior end of the junction between the nasal and frontal bones	Draw the outer surface of the nasal and frontal bones past the junction; then draw a suture between the bones. Identify point Na as the place where these lines intersect.
(ANS) Anterior nasal spine	Maxilla	Indicates the front end of the maxilla, and is located at the tip of the anterior nasal spine	Trace the superior and inferior surfaces of the anterior nasal spine and mark its tip as ANS; then follow the external contour of the bone downward toward the upper incisor, and mark point A at the depth of this concave line.
(A) Point A	Maxilla	Another landmark associated with the anterior maxilla, located at the innermost point of the contour of the premaxilla between the anterior nasal spine and the incisor tooth
(PNS) Posterior Nasal Spine	Maxilla	Indicates the posterior end of the maxilla, and is located at the tip of the posterior spine of the palatine bone, at the junction of the hard and soft palates	Trace the inner contour of the anterior maxillary alveolar process, and continue posteriorly along the roof of the mouth to the end of the bony outline. Mark the end of the palatal bone contour as PNS.
(B) Point B	Mandible	Indicates the anterior part of the bony base of the mandibular dentition, and is located at the innermost point on the contour of the mandible between the incisor tooth and bony chin	race the bony chin. Include the inner aspect of the symphysis as shown (useful for superimposition). Follow the external contour of the bone from the chin upward toward the incisor, and mark point B as the depth of this concave line (image 1). Image 1: Tracing the contour of the mandibular symphysis to locate point B.
(Pg) Pogonion	Mandible	The most anterior point on the contour of the chin	Pogonion is the most prominent point on the anterior aspect of the bony chin. Menton is the most inferior point on the bony chin, and Gnathion is the point on the anterior inferior contour of the chin halfway between pogonion and menton (image 2).
(Me) Menton	Mandible	The most inferior point on the mandibular symphysis (i.e. bottom of chin )
(Gn) Gnathion	Mandible	The center of the inferior contour of the chin, halfway between pogonion and menton
(Go) Gonion	Mandible	Indicates the angle of the mandible, and is located at the center of the inferior contour of the mandibular angle	- Follow the lower border of the mandible posteriorly around the mandibular angle and up the posterior surface of the ramus. Mark the center of the curvature at the gonial angle point Go.
(U1) Upper Incisor	Dentition	Maxillary central incisor tip	Orient your tooth template to accurately represent the axial inclination of the incisor and the position of the tooth’s facial surface. Then use the template to draw in the outline of the incisor
(L1) Lower incisor	Dentition	Mandibular central incisor tip	Orient your tooth template to accurately represent the axial inclination of the incisor and the position of the tooth’s facial surface. Then use the template to draw in the outline of the incisor
(U6) Upper Molar	Dentition	Maxillary 1st molar, mesial cusp tip	This means that the tooth you want to trace is the one of a nearly-superimposed pair that is slightly above and behind the image of the other side. To place the first molar template accurately, it can help to first trace the sides of the second molar. To complete the teeth, it is not necessary to trace all the other teeth, but it is important to outline the occlusal plane of the cheek teeth (2nd molar to 1st premolar). To do this digitally, a point on the crown of the first premolar can be added to orient a line across the crown of the first molar.
(L6) Lower molar	Dentition	Mandibular 1st molar, mesial cusp tip
Soft Tissue Profile	Extra	Outline of the soft tissue profile, from the bridge of the nose to the chin

Tracing Teeth

Important to accurately locate :

• The facial surface of the crowns of the upper and lower incisors
• The inclination of the roots of the incisors
• The position of the upper and lower first molars By convention the molar on the left side, i.e. closest to the film is the one being traced

Watch out for the Orbital, Mandibular canal and 3rd molar

These aren’t fully necessary but help complete tracing of the jaws

Orbitale, Mandibular Canal, 3rd Molar

To complete the tracing of the jaws: trace the orbital rims and note point orbitale (Or), the most inferior point on the lower border of the orbit (image 1).

The orbits are bilateral structures, and if you can see both sides separately, trace both and locate point Or halfway between the two sides.

Also trace the shadow of the inferior alveolar canal and the crown of the unerupted third molar if present (image 2). These structures are especially useful as stable areas for superimposition.

Image 1: Tracing the orbital rim to locate point Or. Don’t confuse the dotted line behind the orbit with the orbital rim—a common tracing mistake.	Image 2: Tracing the outline of the neurovascular bundle below where it enters the lower part of the ramus, and the outline of a third molar at the stage of crown formation.

Link to original

Reference Line	Proportion being measured	Related Landmarks
S-N , the inclincation of the anterior cranial base	Vertical
True horizontal, the visual axis which is drawn perpendicular to true vertical through the lower border of the orbit	Vertical	(Or)
ANS-PNS, palatal plane	Vertical
Functional Occlusal plane	Vertical	Occluding surfaces of posterior teet
Go-Gn, mandibular plane	Vertical
Vertical Nasion Line	A-P	point A should be about 2 mm in front of the Nasion vertical line, with a range of 0-4 mm. Point B should be about 2 mm behind it, with a range of -4 to zero. But the difference between the vertical lines through points A and B should not be more than 4 mm, otherwise the teeth can’t occlude properly.
NA line, NB line ANB angle, SNA and SNB nagles	A-P	ANB line angle is angle between the NA and NB lines, SNA and SNB angles is the angle between sella-nasions-a/b
Point A vertical line	A-P ( maxillary teeth)	- upper central inciro should be slightly but not very much ahead of the line
Point B vertical line	A-P (mandibular Teeth )	Same as upper, lower incisors should be slightly but not very far in front (about 2 mm in front with a range of 1-5 mm )
Mandibular plane (Go-GN)	Mandibular Incisor angulation
Cranial Base plane (S-N )	Maxillary Incisor angulation

03 - Cephalometric Superimposition

Technique of overlaying a ceph tracing from one time point on another tracing from the same individual from a **different time point

Information overload

Instead of measuring all the angles between both timepoints, superimposition make it so that the amount of info is more “manageable”

Region of superimposition	Changes
Cranial Base	- - Changes in the jaws and face relative to cranial base, because the CB stops growing at 7, we see these changes in relation to a neutral referenc epoint
Maxillary superimposition	- Skeletal changes are canceled out and only dental changes relative to the maxilla are demonstrated

Exercise/Technique

See 03 - Cephalometric Superimposition

Line angles

SNA : How protrude or retruded the mandible (“retrognathic vs prognathic),4 degrees is normally considered significant in these relations SNB: same but for mandible ANB: Class (i.e. class III negative angle ) SN-GN : Divergence of of mandible Maxillary incisor to SN plane: inclination of the maxillary incisor (greater = proclination) Interincisal angle = ? still tells a hint of proclination of incisors Maxillary and mandibular to NA/nb: position within skeletal base , protrusive, retrusive or well positioned pg- to n perpendicular: idea of where the bony chin sits: deficient or too prominent.