Cephalometrics in orthodontics/certified fixed orthodontic courses by Indian dental academy

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INDIAN DENTAL ACADEMY
Leader in continuing dental education
Cephalometrics

• Introduction
• Historical perspective
• Cephalostat
• Uses and advantages of cephalogram
• Obtaining the cephalogram
• Cephalometric landmarks
• Cephalometric analysis
• Limitations of cephalometrics
Contents

cephalometrics
ceph=head
metrics=measure
• Defn : cephalometrics is a specialised radiographic
technique for abstracting the human head into a
geometric scheme.
• The basic elements used in geometric analysis of
cephalograms are curves, landmark points and lines.

• Cephalometric analysis is a collection of
numbers to compress information from the
cephalogram for clinical use.
• Different analysis are required for different
purposes.

Historical perspective
• 1899 – Edward Angle – Classification of Malocclusion
• 1915 – Van Loon – developed a method for 3D registration of face
and dentition – Cubus Craniophorus
• 1922 – Simon – modified Van Loon’s inventon by using a face bow.
• 1922 – Pacini – Paved the way for standardized head radiography
• 1931 – Hofrath in Germany and Broadbent in United States –
published their works in the ‘ Forschritte der Orthodontie’ and the
Angle Orthodontist respectively.
• 1939 – Lucien de Coster – published his work on proportional
relationships of the face.

The Bolton Room in the
Anatomical Laboratory of
the Medical School at
Western Reserve
University, Cleveland.

Uses and advantages
• Important diagnostic aid.
• Helps in classifying dental and skeletal
abnormalities as well as establishing facial type.
• Helps in treatment planning
• Helps in prediction of growth related changes
and that associated with surgical treatment.
• It is a valuable aid in research of craniofacial
region.

TYPES OF CEPHALOGRAMS
• Can be of two types
1. Lateral cephalogram: This provides
lateral view of the skull
2. Frontal cephalogram: This provides
antero-posterior view of the skull

Lateral and frontal cephalogram

5 feet
X-ray source
Cephalostat
Film

Cephalometric equipment
• Consists of an X-ray source and a head holding device
called cephalostat
• Cephalostat consists of two ear rods that prevent
movement of the head in horizontal plane
• Vertical stabilization is provided by an orbital pointer that
contacts the lower border of the left orbit
• The upper part of the face is supported by a forehead
clamp positioned above the region of the nasal bridge

• The distance between X-ray source and the mid-sagittal plane of
the patient is fixed at 5 feet (152.4 cm)
• Thus the equipment helps in standardization using a constant head
position which helps to compare serial radiographs
• Natural Head Position (NHP) is a standardized and reproducible
orientation of the head in space when one is focusing on a distant
point at eye level.

Definition of terminology
Anthropometry – Measurement of dimensions of the human body
and it’s parts.
Craniometry – Branch of anthropometry dealing with
measurements of dimensions and angles of bony skull.
Cephalometry – Scientific measurement of dimensions of the
‘living’ head.
Cephalometric analysis – Process of evaluating the skeletal,
dental, and soft tissue relationships of a patient by comparing
measurements performed on the patient’s cephalometric tracing
with population norms for respective measurements, to come to a
diagnosis of the patient’s orthodontic problem.www.indiandentalacademy.com

Cephalometric landmarks
Types
– Anatomic
– Derived
 Hard tissue landmarks
 Soft tissue landmarks
Anatomic
These landmarks represent actual anatomic landmarks of the skull.
Derived landmarks
These are obtained secondarily from anatomic landmarks.

Criteria for landmark selection
• Should be easily identifiable
• Should be uniform in outline and
reproducible
• Should permit valid quantitative
measurements of lines and angles
projected from them.

Anatomical structures
• The major bony structures are:
• Sphenoid bone
• Zygomatic bones
• Maxilla
• Mandible

Unilateral landmarks in lateral cephalograms
• Nasion (Na)- frontonasal suture at its most superior point
on the curve at the bridge of nose
• Anterior nasal spine (ANS)-the most anterior point on
the maxilla at the level of the palate
• Subspinale(“A” point)-the most posterior point on the
curve between ANS and superior Prosthion

• Superior Prosthion(SPr or Pr)- also called
supradentale. The most anterior ,inferior point on the
maxillary alveolar process, usually found near the CEJ of
the maxillary central incisors
• Incision superius (Is)- The incisal tip of the most
anterior maxillary central incisor.
• Incision inferius (Ii)-The incisal tip of the most labial
mandibular central incisor.

• Infradentale (Id) or inferior prosthion-The most
anterior superior point on the mandibular alveolar
process,near CEJ of mandibular central incisor.
• Supramentale (“B” point)-The most posterior point
of the bony curvature of the mandible below
Infradentale and above Pogonion .

• Pogonion (Pog)-the most anterior point on the
contour of the chin
• Gnathion (Gn)-The most anterior inferior point
on the lateral shadow of the chin
• Menton (Me)-The lowest point on the
symphyseal outline of the chin

• Basion (Ba)-The most inferior posterior point in the
sagital plane on the anterior rim of the foramen magnum
• Posterior nasal spine (PNS)-The most posterior
point on the bony hard palate in the sagital plane
• Sella (S)-The center of the hypophyseal fossa
• Broadbent registration point:It is the midpoint of
the perpendicular from the center of sella tursica
to Bolton’s plane

• Glabella-the most prominent point of the
forehead in mid-saggital plane
• Chelion-the lateral terminus of the oral slit
on the outer corner of the mouth

Bilateral landmarks
Both left and right points are located and used, but
some clinicians use the midpoint of the two.
Following are the points-
– Orbitale (Or)-The lowest point of the bony orbit.
Usually the lowest point on the averaged outline is used
for construction of Frankfurt Plane
– Gonion (Go)-The most posterior inferior point at the
angle of the mandible.
– Condylion (Co)-The most posterior superior point on
the condyle of the mandible.

• Articulare (Ar)-The intersection of three radiographic
shadows :the inferior surface of the cranial base and the
posterior surface of the necks of the condyles of the
mandible
• Pterygomaxillary fissure (PTM)-Bilateral tear-
drop shaped area of radiolucency ,the anterior shadow of
which is the posterior surfaces of the maxillary
tuberosities

• Sphenoethmoidal point (SE)-The intersection of the
great wing of sphenoid and cranial floor.
• Frontomaxillary nasal suture (FMN)-The most
superior point of the suture where the maxilla articulates
with the frontal and nasal bones.

Cephalometric Lines (Planes)
• Horizontal
• Vertical
Horizontal planes:
• S-N plane :It is the cranial line between center of sella
and the nasion
• Frankfurt horizontal plane :The common tangent to
the upper external auditory meatus (at porion) and the
inferior border of the orbit (orbitale)

• Functional occlusal line (FOL):A line averaging the
points of posterior occlusal contacts from first
permanent molars to the primary molars or bicuspids
• Mandibular plane :several exist, based on different
analysis
1. Tangent to the lower border of the mandible (Tweed)
2. A line connecting gonion and menton(Downs)
3. A line connecting gonion and gnathion (Steiner)

• Palatal plane: A line joining ANS and PNS
• Bolton-Nasion plane: Line connecting basion and
nasion
• Bolton’s plane: This plane connects bolton’s points
posterior to the occipital condyles and nasion

Cephalometric
Lines (Planes)
• Horizontal
• Vertical
Horizontal planes:
• S-N plane :It is the cranial
line between center of sella
and the nasion

• Frankfurt horizontal plane
:The common tangent to the
upper external auditory meatus
(at porion) and the inferior
border of the orbit (orbitale)

• Functional occlusal line
(FOL):A line averaging the
points of posterior occlusal
contacts from first permanent
molars to the primary molars or
bicuspids

• Mandibular plane :several
exist, based on different
analysis
1. Tangent to the lower
border of the mandible
(Tweed)
2. A line connecting gonion
and menton(Downs)
3. A line connecting gonion
and gnathion (Steiner)

• Palatal plane: A line joining
ANS and PNS

• Bolton-Nasion plane: Line
connecting basion and nasion
• Bolton’s plane: This plane
connects bolton’s points
posterior to the occipital
condyles and nasion

Vertical planes
• A-Pog line :Line from
Point A to pogonion

• Facial plane :Line from
nasion to pogonion

DOWN'S ANALYSIS

• One of the most commonly used analysis
• Downs based his findings on 20
Caucasian individuals of 12-17 years age
group of both sexes
• Downs analysis consists of 10 parameters
-5 skeletal and five dental

Skeletal parameters
1. Facial angle: It is the angle formed by the
intersection of nasion-pogonion plane and the
FH plane
Average value is 87.8° and range between 82-
95°.This angle gives us an indication of the
antero-posterior positioning of the mandible in
relation to the .This value increases in
cases of skeletal CL III while it decreases in
CL II cases

Mean Reading : 87.5o
Range : 82o
– 95o
N
Pog
Po
Or

Mean Reading : 0o
Range : -8.5o
– 10o
Angle of convexity: this is
formed between the
intersection of a line from
nasion to Point A ,and a line
from Point A to pogonion
This angle reveals the
convexity or concavity of the
skeletal profile
A positive angle or an
increased angle shows a
prominent maxillary base
compared to mandible or a
retrognathic profile,while a
negative or decreased angle
shows a prognathic profile

Mean Reading : -4.6o
Range : 0o
– - 9o
A-B Plane: this angle is
formed between a line
connecting Point A and
Point B , and a line joining
nasion to pogonion.
This angle is indicative of
the maxillo-mandibular
relationship in relation to
the facial plane
It is usually negative as
Point B is Positioned
behind Point A
In cases of CL III
malocclusions , a positive
angle is seen

Range : 17o
– 28o
Formed by intersection
of mandibular plane
with FH Plane.
An increased plane is
suggestive of a vertical
grower with a
hyperdivergent facial
pattern

Range : 53o
– 66o
This angle is formed
by joining sella-
gnathion line with FH
plane . This angle is
larger in CL II patterns
than CL III patterns.It
indicates the growth
pattern of the
individual.If the angle
is greater than normal,
it indicates greater
vertical growth of the
mandible and if it is
lesser ,it indicates
horizontal growth of
the mandible www.indiandentalacademy.com

Dental parameters
1

Mean Reading : 9.3o
Range : 1.5o
– 1.4o
..
between occlusal
plane and F.H. plane.
Downs constructed the
occlusal plane by
bisecting the occlusion
of first permanent
molars and incisor
overbite. This angle
gives us a measure of
the slope of occlusal
plane relative to F.H.
plane

2 Inter-incisal angle-

Mean reading : 135.4o
Range : 130o
– 150o
between the long
axes of upper and
lower incisors. This
angle decreases in CL
I bimax.protrusion and
CL II DivI.cases
,whereas it increases
in CL II DivII cases

3 Incisor Mandible Plane Angle-

Mean reading : 1.4o
Range : -8.5o
– 7o
by intersection of
long axis of lower
incisor and
mandibular plane.
An increase in this
angle is indicative of
lower incisor
proclination

4 Incisor occlusal plane angle :the inside
inferior angle formed by intersection
between long axis of lower central incisor
and occlusal plane ;it is read +ve or –ve
deviation from a right angle
An increase in this angle is suggestive of
increased lower incisor proclination

5 Upper incisor to A-Pog line-This is a linear
measurement between incisal edge of maxillary
central incisor and a line joining Point A to
pogonion
Average value is 2.7mm and range is -1 to 5mm
It is more in patients with upper incisor
proclination

Vorhies and Adams (1951)
Wriggle

STEINER’S ANALYSIS

• Developed in 1930 by Cecil C. Steiner
• This analysis aims at providing maximal
clinical information with the least number
of measurements

STEINER’S ANALYSIS
SKELETALANALYSIS
DENTALANALYSIS
SOFT TISSUE ANALYSIS

Skeletal parameter
S.N.A. angle-

Mean reading : 82o
It is the angle
formed by the intersection
of S.N. plane and a line
joining nasion and point A
This angle indicates
the relative antero-
posterior positioning of
maxilla in relation to
cranial base
A larger than
normal value indicates a
prognathic maxilla while a
smaller value suggests a
retrognathic maxilla

S.N.B angle-

Mean reading : 80o
It is the angle
between S.N. plane
and a line joining
nasion to Point B.
This angle indicates
the antero-posterior
positioning of the
mandible in relation to
cranial base
An increase indicates
a prognathic mandible
and lesser value
suggests retrusive
mandible www.indiandentalacademy.com

A.N.B. angle-

ANB
Mean reading : 2o
This angle is formed by
intersection of the lines
joining nasion to Point
A, and nasion to Point
B. It denotes the
relative position of
maxilla and mandible to
each other. An increase
is suggestive of CLII
skeletal tendency while
lesser than normal
suggests CLIII skeletal
relationship

Occlusal plane angle-

Mean reading : 14o
Formed between
occlusal plane and
S.N. plane .The
occlusal plane is
represented by a line
passing between the
overlapping cusps of
first premolars and
first molars. This
angle denotes the
relation of occlusal
plane to cranium and
face.

Mandibular plane angle-It is the angle
formed between Mandibular plane and
S.N. plane. The mandibular plane is a line
connecting gonion and gnathion
Mean value is 32 degrees
This angle indicates growth pattern;a
lower angle suggests a horizontal growing
face and increased angle shows a vertical
pattern

Mean reading : 32o

Dental parameters
Upper incisor to N-A(angle)- Formed by
intersection of long axis of upper centrals
and line joining nasion to point A.
Mean is 22 degrees.
It indicates the relative inclination of upper
incisors; increased angle is seen during
proclination

Lower incisor to N.B (angle)-Formed
between N-B plane and long axis of lower
incisor
Mean value is 25 degrees.
It shows us the inclination of lower central
incisor; an increased value shows
proclined incisor and decreased angle
gives retroclined incisor

Upper incisor to N.A (Linear)-It is a linear
measurement formed between labial
surface of upper central incisor and a line
joining nasion to Point A .
Mean value is 4mm
This value helps in determining upper
incisor position ;it increases in proclined
upper incisors

Lower incisor to N.B (Linear)- It is the linear
distance between Labial surface of lower
central incisor and a line joining nasion to
Point B.
Mean value is 4mm.
It helps us to assess lower incisor
inclination; increased value shows
proclination and vice-versa

Interincisal angle-Formed between long axis
of upper central and long axis of lower
central incisors.
Mean value is 130-131 degrees.
A decreased angle is seen in proclination
of incisors and increased in retroclined
incisors

Mean reading : 130o

Soft tissue analysis
S-line – Steiner suggests that in a well balanced
face the lips should touch a line extending from
soft tissue contour of the chin to the middle of an
‘S’ formed by lower border of nose
If lips are beyond this line , it indicates protrusive
lips and convex profile;and if behind the line
shows retrusive lips and the patient may have
concave profile

TWEED’S ANALYSIS

TWEED’S ANALYSIS
• Three planes are used forming a
diagnostic triangle:
1)Franfurt horizontal plane (FH PLANE)
2)Mandibular plane(MP)
3)Long axis of mandibular incisor(MIA)
• Frankfort mandibular plane angle :
formed by intersection of FH plane with mandibular
plane (mean=25°)

SOFT TISSUE NASION
PRONASALE
SUB NASALE
SUB SPINALE
LABRALE SUPERIUS
STOMION
LABRALE INFERIUS
SUB MENTALE
SOFT TISSUE POGONION
SKIN GNATHION
SOFT TISSUE CEPHALOMETRIC LANDMARKS

Problems and limitations
• It is a two dimensional representative of three
dimensional structures.
• Problems in orientation of patient while procuring
radiograph.
• Fallacy of false precision- difficulty in location of
landmarks precisely.
• Fallacy of ignoring the patient- mean population
averages differ from characteristics of a particular
patient.
• Fallacy of using chronological age for comparisons and
references within age classes.

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Cephalometrics in orthodontics/certified fixed orthodontic courses by Indian dental academy

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