This document provides an overview of cephalometric landmarks and angles used in orthodontic analysis and orthognathic surgery planning. It describes various bony and soft tissue landmarks, as well as angles measuring relationships between structures like the maxilla, mandible, and cranial base. The angles and ratios discussed can help evaluate problems like vertical discrepancies, jaw positions, and soft tissue drape to plan surgical procedures while avoiding undesirable outcomes. In total, the document introduces the key anatomical points and angular measurements used in comprehensive orthodontic and surgical treatment planning.

1. dr Maher FOUDA
Faculty of Dentistry
Mansoura Egypt
Professor of orthodontics
Cephalometric Analysis For
Orthognathic Surgery
Part 1

2. Cephalometric landmarks (boney)
S (Sella) the center of the pituitary
fossa-Sella Turcica
N or Na (Nasion)-the most anterior point
at the junction of the
nasal and frontal bones in the mid
saggital plane.
Po (Porion) the point located at the most
superior point of the
external auditory meatus.

3. o or Or (Orbitale) the lowest point on the
inferior boney border of
the left orbital cavity as viewed from the
lateral aspect.
ANS (Anterior Nasal Spine) most
anterior tip of maxillary nasal
PNS (Posterior Nasal Spine) midline tip
of posterior spine of
hard palate in the mid saggital plane.

4. P or Pog (pogonion) the most anterior
point on the contour of the
mandibular symphysis.
Pt. A (point A) the deepest midpoint on
the maxillary alveolar
process between ANS and the crest of
alveolar ridge.
Pt. B (Point B) the deepest midpoint on the
alveolar process
between the crest of the ridge and
pogonion.
Me (Menton) the lowest point on the
contour of the mandibular
symphysis.

5. Gn (Gnathion) the most anterior-
inferior point on the chin
contour constructed point,
determined by bisecting the
angle formed by the facial and
mandibular planes.
Ar (Articulare) the junction of the
basisphenoid with the
posterior of the condyle of the
mandible.
Go (Gonion) the point at the angle
of the mandible that is
most inferiorly and posteriorly
directed.

6. Mandibular length-Ar-Pg .The
mandibular length of 115 ± 5
rn rn is a useful distance
measurement to evaluate the
length of the mandible,
especially when true versus
pseudo prognathism is
being considered.

7. The Facial Plane Angle-Frankfort Horizontal
(Po-Or)
and the Facial Plane
The mean for this angle is 88 ± 3 degrees.
This angle is
influenced by the chin position. If there is a
microgenia
or a retrogenia, this angle will tend to be
more acute. As
the chin becomes more prominent it
becomes more
obtuse. This angle, however, can also be
affected if there
is retrognathia, as in Class II, or prognathia, as in
Class
III, both of which would affect the amount of chin
projection.

8. S-N-A Angle
The mean for this angle is 82 ± 3
degrees and it relates
the maxilla with the cranial base. In
cases of maxillary
retrusion this angle would be more
acute. However, in
some craniofacial deformities the cranial
base may be
too steep. Therefore there is a check
angle that we use to
better evaluate the maxilla: the Landes
angle or the angle
of maxillary depth.

9. Landes Angle (Angle of Maxillary
Depth))
This angle is formed by the
intersection of the Frankfort
horizontal and the N-A plane. The
mean is 88 ± 3 degrees.
The angle is a check on the S-N-A, but
it is more
reliable because it relates to the
reliable Frankfort Horizontal
Plane. The angle also evaluates the
anteriorposterior
position of the maxilla and helps to
determine
whether a Class II or Class III
malocclusion is secondary
to a malpositioned maxilla or
mandible.

10. Mandibular Plane Angle
(Frankfort Horizontal-Mandibular Plane
This angle is formed by the intersection of the Frankfort
Horizontal and the mandibular plane. The mean is 21 ±
3 degrees. It is an angle that expresses the vertical
posterior
facial height in relation to the anterior facial height.
In vertical discrepancies such as open bite deformities, it
is obtuse, whereas in short face syndrome patients, the
angle is more acute. According to Epker and Fish,?
patients who have acute angles tend to have strong
musculature and deep bites, whereas patients who have
high or obtuse angles have weak musculature.

11. Y-Axis (Growth Angle)
This is the anterior-inferior angle formed by the S-Gn
plane and Frankfort horizontal. It is a predictor angle
used by orthodontists to predict the amount of
forward
and/or downward growth of the mandible. If the
angle
is obtuse it indicates the mandible is tending to grow
downward rather than forward. Interceptive
orthodontics
would attempt to correct this problem early. If the
angle is acute it indicates that the mandible is
growing
forward, resulting in a prognathic tendency or a
vertically
deficient face.

12. S-N-Pg
This angle relates the cranial base
plane with the facial
plane. The mean is 80 ± 3 degrees.
It is a less accurate
measurement than the facial plane
angle, but can be
used as a check measurement to
see the accuracy of the
facial plane angle. It relates
primarily the chin with
the cranial base but is also
affected by the position of the
mandible as a whole.

13. S-N-Or
This angle relates the cranial
base with the orbital rim
position. The mean is 54 ± 4
degrees. This angle is helpful
if one is concerned about the
orbital rim position in
relation to maxillary
hypoplasia.

14. Upper Facial Height,
Lower Facial Height,
and Total Facial Height)
Measurement of the total
facial height is evaluated
by
first drawing a plane 7
degrees from the S-N
plane. This
is known as the
horizontal plane. From
this horizontal
plane (HP) a
perpendicular line is
dropped and horizontals
are made to either ANS
or Pt. A and menton.

15. If you are using ANS related
to nasion, then this distance
represents 45 percent of the
total facial height,
whereas if you are using Pt.
A to nasion, it represents
about 50 percent of the total
facial height. In an article by
Grayson,9 means and
extremes in total and lower
facial
height in linear measure are
evaluated as follows:

16. Soft Tissue Analysis
In evaluating the soft tissues of a
patient we again turn
to the work of Legan ad
Burstone. It has been found
that in planning surgery, changes
in soft tissue are
important to the final outcome of
the procedure. It is
also important to the final
outcome of the procedure. It
is also important to determine
whether the procedures
will compromise the soft tissues
of the neck, nose, or lips
so as to produce a result that
may be dentally correct but
cosmetically a disaster.

17. G' (Soft Tissue Glabella) the most
prominent point in the
midsagittal plane of the forehead.
Cm (Columella point) the most anterior
point on the columella of
the nose.
Sn (Subnasale) the point at which the
nasal septum merges with
the upper cutaneous lip and the
midsagittal plane.

18. Ls (Labrale superius) the
mucocutaneous border of the upper lip
in the rT;1idsagittal plane.
Li (Labra/e inferius) the mucocutaneous
border of the lower lip in
the midsagittal plane.
Pg' (Soft-tissue pogonion) the most
anterior point of the soft-tissue
chin.

19. HP (Horizontal plane) a plane drawn 7
degrees above the S-N
plane, from which perpendicular lines
are drawn to measure
vertical soft tissue distances.
Stms (Stomion Superius) the lowermost
point on the vermilion of the
upper lip.
Stmi (Stomion Inferius) the uppermost
point of the vermilion of the
lower lip.

20. C (Cervical Point) the innermost point
between the submental
area and where the neck begins its
vertical position.
Me' (Soft Tissue Menton) lowest point on
the contour of the soft
tissue chin.
Gn' (Soft Tissue Gnathion) the
constructoo midpoint between soft
tissue pogonion and soft tissue me(lton;
can be located at
intersection of subnasale to soft tissue
pogonion line and the
line from C to Me'.

21. Angle of Soft Tissue Facial
Convexity-G'-Sn-Pg'
This is the inferior angle formed by
the soft tissue glabella
(G') and subnasale plane with the
subnasale soft
tissue pogonion (Pg') plane. The
mean is 12 ±4 degrees.
This angle increases as the face
becomes more convex,
as in patients with Class II
malocclusions, but in whom
the soft tissue chin button has not
compensated.

22. Upper Lip Length (Sn-Stms)
This measurement, in millimeters, is
the distance from
subnasale to stomion superius (or
the most inferior portion
of the upper lip vermilion). The
mean is 21 ± 2mm.
In patients with a true short upper
lip this distance is
below the mean and the external
millimeter measurement.

23. This vertical distance measures the
soft tissue of the
upper lip, interdental distance at
rest, and the soft tissue
lower lip and chin. If the value
approaches 1: 3 or
1:4 it jndicates a short upper lip or
a long lower one
third of the face. If the ratio
approaches 1:1 it usually
means a short lower ,one third of
the face, and only
rarely do we find a true long upper
lip.
Clinical Evaluation of the Soft Tissue of
the Lower Half
of the Face
a. Upper lip relation to Lower third of face

24. Clinical Evaluation of the Soft Tissue of
the Lower Half
of the Face
This soft tissue vertical measurement
takes into consideration the interlabial
distance,
which at rest is 0 to 3mm. (If this
distance is wider
than 3mm it indicates lip incompetence.)

25. If this ratio
is greater than 1: 09, such as 3: 1, it is
indicative of
excessive vertical dimension of the
maxilla. If the
ratio is smaller, such as 1: 3, it is
indicative of either
a short maxilla in its vertical dimension
or a long
vertical chin.

26. and Sn-Gn'-C = 100 +7 degrees
The lower facial height and the
lower facial depth
relationship is a 1: 1 relationship,
and the angle
formed by the lower facial throat
angle is 100 ±7 degrees.
If this ratio becomes larger than 1,
the patient
has a short neck or if the angle is
significantly greater
than 100 degrees the submental
area is obtuse.

27. These
two measurements become
important when considering
a reduction genioplasty or a
mandibular setback
procedure. If the setback is
done in a patient
with an obtuse lower facial
throat angle, it could create
an unsightly bulging in.the
submental area and a.
·very unhappy patient. Class III
patients who have
short, heavy throats and obtuse
lower facial throat
angles should have maxillary
advancement or mandibular
setback procedures combined
with advancement
genioplasty.

28. d. Depth of submental
sulcus . The depth of
the submental crease
should be about 4mm to
produce
a pleasing lower lip to
chin contour.
Labio-mental sulcus depth (depth of sulcus
perpendicular
to Li - Pg' =4 mm.

29. With the tools of the cephalometric analysis at hand, it
is possible to effectively evaluate the patient and his
soft tissue drape. We can tell which jaw is abnormal and
direct our surgical approach to that area. If we were to
attempt to correct a pseudoprognathic jaw deformity
by incorrectly moving the mandible posteriorly
we would doom the patient to a good functional
occlusion but an aesthetically disastrous result with a
flat facial appearance. As we move the various bony
parts we are directly or indirectly affecting the overlying
soft tissues to produce the optimum functional and
aesthetic result.

30. 1. Soft Tissue Changes in the Mandible with
Advancement
and Retrusion
A. A mandibular advancement of lOmm would
result in:
a. Labial sulcus at Pt. B, moves forward 10mm
b. Soft tissue pogonion moves forward 10mm
c. The lower lip and vermilion border advance
6.5 to 8mm. If, however, the preoperative
overjet is not extensive so that the lower lip is
not rolled up under the upper teeth, the lower
lip advancement will be closer to lOmm.

31. d. As the mandible is advanced the labial sulcus
become more shallow, and the lower lip becomes
less prominent. If, however, you are
doing only an advancement osseous genioplasty,
the labial sulcus may remain as deep or
become even more prominent.

32. e. Little, if any, changes in the upper lip occur
when the mandible is moved unless there is an
opening of the vertical dimension. In these cases,
as the increase in vertical height occurs, the
upper lip becomes thinner.

33. 2. A mandibular setback of 10mm would result in:
a. Soft tissue pogonion moves back 10mm.
b. The labial sulcus moves back 8mm.
c. Lower lip and vermilion move back 6-7mm
because
they are held forward slightly by the contact
with the upper incisors.
Cephalometric superimposition: before (black) and after(re

34. d. Upper lip and vermilion move back 2mm due to
the increase in vertical dimension frequently seen
as the mandible is moved posteriorly. (This is
because
prognathic patients are frequently overclosed
before surgery.)

35. e. The upper lip at Pt. A moves back 0.2mm because
of the change in vertical dimension. Therefore
the upper lip appears to lengthen and becomes
thinner.
f. The labial mental sulcus increases slightly and the
lip becomes slightly more prominent when compared
to the chin and lower lip sulcus.

36. .
1. Maxillary advancement of 10mm
a. Nasal tip will advance 2-3mm.
b. The nasolabial angle will decrease depending
on what is done or not done to the anterior nasal
spine.
c. Stomion moves forward and slightly lower
because the upper lip elongates about 1mm.
B. Soft tissue changes in maxilla with advancement and
impaction

37. Reference