Radiographic cephalometry /certified fixed orthodontic courses by Indian dental academy

RADIOGRAPHIC
CEPHLOMETRY

www.indiandentalacademy.com

INDIAN DENTAL ACADEMY
Leader in continuing dental education



CONTENTS
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INTRODUCTION
HISTORY
TYPES OF CEPHALOGRAM
USES OF CEPHALOGRAMS
CEPHLOMETRIC TECHNIQUE
CEPHLOMETRIC LANDMARKS
TRACING TECHNIQUE
DOWN’S ANALYSIS
STEINER ANALYSIS
WITS APPRAISAL
TWEED ANALYSIS

INTRODUCTION


The assessment of craniofacial structures forms a part of
orthodontics diagnosis. Cephalometric analysis of skeletal ,dental
& soft tissues are merely aids in determining the diagnosis.
For an accurate interpretation,the various readings must not be
assessed independently. To interpret the data, all readings must
be co-related with other clinical & diagnostic criteria before
arriving at the diagnosis & treatment planning.


HISTORY


The earliest method used to asses facial proportions was by
artistic standards with harmony, symmetry and beauty as key
points.
Craniometry said to be forerunner of cephlometry. Craniometry
involved measurement of craniofacial dimensions of skulls of
dead persons.
The discovery of X- rays in 1895 by Roentgen revolutionized
dentistry.The value of radiography as a diagnostic aid in
orthodontics was proclaimed by W. A. Price in 1900

In 1922 Paccini standardized the radiographic head images by
positioning subject against film cassette at a distance of 2 m
from X-ray tube.
In 1931 Broadbent in USA and Hofrath in Germany
simultaneously presented a standardized cephalometric
technique using high powered X ray machine and a head
holder called cephalostat.


TYPES OF CEPHALOGRAMS


Cephalograms can of two types
a) Lateral cephalogramsThis provides lateral view of skull. Also referred to as
lateral “cephs”, have become virtually indispensable to
the orthodontists in treatment of patients.
They are important in orthodontic growth analysis,
diagnosis, treatment planning, monitoring of therapy and
evaluation of final treatment out come.

b) Postroanterior cephalograms (PA)
They provide additional radiographic information
mediolaterally which is particularly useful for presurgical
and asymmetric growth pattern.
The basic equipment required to obtain both lateral and PA
cephlometric view consists of an X-Ray source ,an
adujustable cephlostat, a film cassete with radigraphic
itensifying screens, and film cassette holder.


Uses of cephalograms –
Cephlometric has established itself as one of pillars of
comprehensive orthodontic diagnosis.
It is also valuable tool in treatment planning and follow of
patient undergoing orthodontic treatment.
a)

Ceplometrics helps in orthodontic diagnosis by enabling
the study of skeletal, dental and soft structures of the
cranio-facial region.

b)

It helps in classification of the skeletal dental
abnormalities and also helps in establishing facial type.

c) Cephlometrics helps in planning treatment for an
individual.
d) It helps in evaluation of the treatment results by
quantifying the changes brought by treatment.
e) Cephlometrics helps predicting the growth related changes
and changes brought by treatment.
f) Cephlometrics is a valuable aid research work involving
the cranio-dento-facial region.


RADIOGRAPHIC CEPHLOMETRIC
TECHNIQUE


Equipment:
The cephalometric radiographs are taken using an
apparatus that consists of an x-ray source and a head
holding device called cephalostat. The cephalostat consists
of two ear rods that prevent the movement of the head in
the horizontal plane. Vertical stabilization of the head is
brought about by an orbital pointer that contacts the lower
border of the left orbit.


The upper part of the face is supported by the 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 standardizing the radiographs by use of
constant head position and source film distance so that
serial radiographs can be compared.


CEPHLOMETRIC LANDMARKS
Cephalometric makes use of certain landmarks or points on
the skull which are used for quantitative analysis and
measurements.
Cephalometric landmarks can of two types :
ANATOMIC LANDMARKS
These landmarks represent actual anatomic structures of the
skull

DERIVED LANDMARKS
These are landmarks that have been obtained secondarily
from anatomic structures in a cephalogram.
REQUIREMENTS FOR LANDMARKS:
a) It should be easily seen in a radiograph.
b) It should be uniform in outline and should be
reproducible.
c) The landmarks should permit valid quntitative
measurements of lines and angles projected from them.

Cephalometric landmarks:
Nasion:
The most anterior point midway between the frontal and nasal
bones on the fronto-nasal suture.
Orbitale :
The lowest point on the inferior bony margin of the orbit.
Porion:
The highest bony point on the upper margin of external auditory
meatus.

Sella :
The point representing the midpoint of the pituitary fossa or
sella turcica. It is a constructed point in the mid-sagittal
plane.
Point A:
It is the deepest point in the midline between the anterior
nasal spine and alveolar crest between the two central
incisors. It is also called subspinale.


Point B:
It is the deepest point in the midline between the alveolar
crest of mandible and the mental process. It is also called
supramentale.
Basion:
It is the median point of the anterior margin of the foramen
magnum.
Bolton point :
The highest point at the post condylar notch of the occipital
bone.

Anterior nasal spine:
It is the anterior tip of the sharp bony process of the maxilla in
the midline of the lower margin of anterior nasal opening.
Gonion:
It is a constructed point at the junction of ramal plane and the
mandibular plane.
Pogonion:
It is the most anterior point of the bony chin in the median
plane.

Menton:
It is the most inferior midline point on the mandibular
symphysis.
Gnathion :
It is the most antero-inferior point on the symphysis of the
chin. It is constructed by intersecting a line drawn
perpendicular to the line connecting menton and pogonion.


Articulare :
It is a point at the junction of the posterior border of ramus
and the inferior border of the basilar part of the occipital
bone.
Condylion:
The most superior point on the head of the condyle.
Prosthion :
The lowest and most anterior point on the alveolar bone in the
midline, between the upper central incisors. It is also called
supradentale.

Infradentale:
The highest and most anterior point on the alveolar process,
in the median plane between the mandibular central incisors.
The key ridge :
The lower most point on the contour of the anterior wall of
the infratemporal fossa.
Posterior nasal spine:
The inter-section of a continuation of the anterior wall of the
pterygo-palatine fossa and the floor of the nose, marking the
distal limit of the maxilla.

Broadbent registration point :
It is the midpoint of the perpendicular from the center of sella
tursica to the Bolton plane.
Ptm point :
It is the intersection of the inferior border of the foraman
rotundum with the posterior wall of the pterygo-maxillary
fissure.


Tracing technique:
The following items are recommended for tracing a head film:
1)

A lateral cephalogram, the usual dimensions of which are

8 x 10 inches (patients with facial asymmetry often require a
frontal anteroposterior headfilm).
2)

Acetate matte tracing paper (0.003 inches thick, 8 x 10

inches).
3)

A sharp 3H drawing pencil or a very fine felt-tipped pen.

4)

Masking tape

5)

A few sheets of cardboard (preferably black),
measuring approximately 6 x 12 inches, and a hollow
cardboard tube.

6)

A protractor and tooth symbol tracing template for
drawing the teeth (optional). Most templates have round
holes for tracing the outline of the ear rods.

7)

Dental casts trimmed to maximal intercuspidation of

the teeth in occlusion


8)
9)

View box (variable rheostat desirable, but no essential).
Pencil sharpener and an eraser.


General considerations for tracing:
Start by placing the cephalogram on the view box with
the patient’s image facing to the right. Tape the four
corners of the radiograph to the view box.
With a fine felt-tipped black pen, draw three crosses on
the radiograph, two within the cranium and one over the
area of the cervical vertebrae.


These registration crosses allow for reorienting the acetate
tracing on the film for later verification or in the event the
film becomes displaced during the tracing procedure, a not
infrequent occurrence.
Next, place the matte acetate film over the radiograph and
tape it securely to the radiograph and the view box. After
firmly affixing the acetate film, trace the three registration
crosses.

. Use smooth continuous pressure on the pencil; whenever
possible, trace image lines without stopping and/or lifting
the pencil from the acetate film. Avoid erasures.
Consult dental casts when outlining molar and incisor
teeth, taking care to depict left and right teeth.


Down’s analysis
Down elected to use FH (Frankfurt Horizontal plane) as a
reference base to determine the degree of retrognathism,
orthognathism or prognathism of lower jaw.


Parameter:
Skeletal
Facial angle (87.80)
Angle of convexity (00)
A-B plane angle (-4.80)
Mandibular plane angle (21.90)
Y-axis (59.40)


Dental
Cant of occlusal plane (9.30)
Interincisal angle (135.40)
Incisor occlusal plane angle (14.50)
Incisor mandibular plane angle (1.40)
Protrusion of maxillary incisors (2.70)


Facial angle : (FH plane) to (N-Pog)
·

It is used to measure the degree of retrusion or protrusion
of the lower jaw

·

It can be defined as the inferior inside angle in which the
facial line (N-Pog) intersects the FH plane.

·

Mean value is 87.80 (SD = 3.6)

·

Increased angle = protrusive chin; Decreased angle =
retrusive chin


Facial angle


Angle of convexity:
· It is used to measure the degree of maxillary basal arch at its
anterior limit (Point A) in relative to the total facial profile
(N-Pog).
· It is formed by the intersection of the line (N-Point A) to
(Point A-Pog)
·

Mean value is 00 (SD = 5.10)

·

If the line (Point A-Pog) is located anterior to (N-point A),
the angle is +ve. Suggesting protrusive maxilla in relation to
mandible. Negative angle suggests retrusive maxilla.

ANGLE OF CONVEXITY


A-B plane:
·

This is used to measure the relation of anterior limit of apical
bases to each other relation to facial line.

· Angle formed by intersection of line (Point A - Point B) to
(N-Pog).
·

Mean value is –4.60 (SD = 3.60)
Since point B is located behind point A, the angle is usually
–ve. Only in class III it is +ve.


A-B plane


Mandibular plane angle:
Relationship of the mandible to cranial base.
Angle formed by intersection of line (M-Go) to FH plane.
High mandibular plane angles occur in both protrusive and
retrusive faces which complicate treatment and prognosis.
High and low mandibular plane angles suggest unfavourable
growth patterns.


Mandibular plane angle


·

·

Y-axis:
Y-axis indicate the degree of forward, backward and
downward position of the chin in relation to upper face.
Acute angle formed by the intersection of line (S-Gn) to FH
plane.

·

Mean value is 59.40 (3.80)

·

An increase in Y-axis- Vertical growth, decrease in Y-axis Horizontal growth.


Dental parameters:
Cant of occlusal plane:
·

It is the measure of the slope of occlusal plane to the FH

plane.
·

Defined occlusal plane as that line bisecting the

overlapping cusps of the first molars and the incisal overbite.
When the occlusal plane is intersected to the FH plane, angle
is formed.
·


Cant of occlusal plane


Interincisal angle:
· Used to measure the relation of maxillary and mandibular
central incisors to denture base.
·

The angle is formed by passing a line through the incisal

edge and apex of the root of the maxillary and mandibular
central incisor.
·


·

Angle is small if incisors are tipped forward.


Interincisal angle


Incisor occlusal plane angle:
·

It relates the lower incisors to their functioning surface at
the occlusal plane.

·

Angle increase as teeth forward.


Incisor occlusal plane angle


Incisor mandibular plane angle:
· Angle is formed by intersection of mandibular plane with a
•

line passing through incisal edge and the apex of the root of
the lower incisor.
· Mean value is 1.40 (SD = 3.80)
· Angle increase as teeth forward.


Incisor mandibular plane angle


Protrusion of maxillary incisors:
·

It is measured as the distance between the incisal edge
of the maxillary central incisor to the line (Point A-Pog)

·

Mean value is 2.7 mm (SD = 1.8 mm)

· Distance is +ve if incisal edge of maxillary central
incisor is ahead of the line (Point A-Pog). This indicates
protrusion of maxillary central incisor. Negative
indicates retrusion of maxillary central incisor.


Upper incisor to A- pog line


STEINER ANALYSIS
Steiner selected most meaningful parameters and evolved a
composite analysis.
The skeletal analysis entails relating the upper and lower
jaw to the skull and to each other.
The dental analysis relates the upper and lower incisor
teeth to their respective jaws and to each other.
Soft – tissue analysis provides a means of assessing the
balance and harmony of the lower facial profile

Parameters:
Skeletal
SNA angle (maxilla)
SNB angle (Mandibular)
ANB angle (Maxillary-mandibular)
Occlusal plane
Mandibular plane


Dental

Soft tissue

Maxillary incisor position
Mandibular incisor position
Inter-incisal angle
Lower incisor to chin


S-line

Skeletal analysis:
Since landmarks such as porion and orbitale are not always
easily identified, Steiner elected to use the anterior cranial
base (Sella-Nasion) as reference line to which jaws are
related.
The advantage of using these two midline points (Sella
and Nasion) is that they are moved only a minimal amount
whenever head deviates from true profile position and
even if the head is rotated in the cephalostat.

Skeletal analysis:
Maxilla (SNA angle):
· It is used to measure the degree of protrusion or
retrusion of maxilla to the cranial base.
· SNA angle is formed by intersection of (S-N) line
with (N-point A) line.
· Mean SNA angle is 820.
·

Increase in angle  Forward positioning of

maxilla
· Decrease in anglewww.indiandentalacademy.com
 Backward positioning of

SNA angle


Mandible (SNB angle):
·

It is used to measure the degree of protrusion or retrusion of
mandible to the cranial base.

·

SNB angle is formed by intersection of (S-N) line with (Npoint B) line.

·

Mean value is 800

·

Increase in angle  Forward positioning of mandible
Decrease in angle  Backward positioning of mandible

SNB angle


Maxilla to mandible (ANB angle)
ANB angle provides information on the relative position of
maxillary and mandible to each other.
Angle formed by joining AN and NB (SNA-SNB)
Mean value is 20.
Increase in SNA (More than 20) suggests protrusive maxilla
Decrease in SNA (less than 20) suggests retrusive maxilla and
protrusive mandible


ANB angle


Occlusal plane:
· It shows significance of the teeth in occlusion to the
cranial base and face.
· Occlusal plane is drawn through the region of the
overlapping cusps of the first premolars and the
molars.
Angle formed by S-N plane to occlusal plane.
·

Mean reading for normal occlusion is 140.

Occlusal plane:


Mandibular plane (Go-Gn)

It shows the growth pattern.
·

It is drawn between gonion (Go) and gnathion (Gn)

·

Mean reading is 320.
Excessive low or high mandibular plane angle suggests
unfavourable growth pattern

Dental analysis:
Maxillary incisor position:
To know the relative location and axial inclination of the
upper incisors by relating the teeth to N-A line.
· Axial inclination: The upper incisor to N-A reading indicates
the axial inclination of the upper incisor in degrees (Mean
220)
· Location: Distance between most anteriorly placed point on
the maxillary central incisor to the N-A line in millimeters
(Mean 4 mm).


Upper incisor to N-A (angle)


Upper incisor to N-A (linear)


Mandibular incisor position:
To know the relative anteroposterior location and axial
inclination of the lower incisors by relating the lower
incisors to N-B line.
· Axial inclination: Angle formed between the long axis of
the lower incisor and the N-B line indicates axial
inclination of lower incisor (Mean = 250)
·

Location: Distance between most anteriorly placed point
on mandibular incisor to N-B line (Mean = 4 mm).

Mandibular incisor position:


Inter-incisal angle:
·

To know the relative position of the upper incisor to that
of lower incisor.

·

Angle formed by passing through long axis of upper
central incisor and lower central incisor.

·

Mean value is 1300


Inter-incisal angle:


Soft-tissue analysis (S-line):
· According to Steiner, Lips in well balanced faces should
touch a line extending from soft-tissue contour of the chin to
the middle of an S formed by lower border of the nose. This
line is referred to as S-line.
· Lips located beyond S-line tend to be procumbency and
need orthodontic treatment.
Lips located behind S-line, patient profile is generally
“concave” and needs treatment.

STEINER`S S-LINE


Wits appraisal
The Wits appraisal is a linear measurement and not an
analysis.
The purpose of Wits appraisal is to determine the severity
of jaw disharmony that is not reflected in the conventional
ANB angle (Steiners analysis).


ANB as a measure of jaw dysplasia:
ANB angle in normal occlusions is 20. Angle greater
indicates class II disharmony. Negative angle indicates
class III disharmony.
This is an acceptable generalization, there are many
instances in which this (ANB angle) does not apply.


Therefore variations from the accepted (ANB=20) assume
importance

when

attempting

to

appraise

craniofacial skeletal disharmony.


degree

of

Method of Wits appraisal :
The purpose of Wits appraisal is to determine the severity
of jaw disharmony that is not reflected in the conventional
ANB angle.
·

It is a measure of the extent to which the jaws are related
to each other anteroposteriorly.

·

Here, first the occlusal plane is drawn through the region
of overlapping cusps of first premolars and first molars
(Steiner analysis).

· Then, perpendicular lines are drawn from point A and
point B to the occlusal planes.

WITS APPRAISAL


The points of contact on the occlusal plane from A and B are
labeled as Ao and Bo respectively.
Normal occlusion: Point Bo is 1 mm anterior to Ao
·

Class II: Point Ao is located anterior to Bo.

·

Class III: Point Bo is located anterior to Ao.
Normal-For men - -1mm
For women – 0mm (range,-2 to 4mm).


Therefore wits appraisal is intended not as single
diagnostic criteria but as an additional measurement to
SNA angle (Steiner’s) which aids in assessing the degree
of anteroposterior jaw disharmony.


Tweed analysis:
The Tweed analysis makes use of three plane that form a
diagnostic triangle. The planes used are;
·

Frankfort horizontal plane

·

Mandibular plane
Long axis of lower incisor
The objectives of the analysis include;

·

Determination of the position of the lower incisor
Evaluation of prognosis

TWEED ANALYSIS


The angles formed by these three planes are;
Frankfort mandibular plane angle (FMPA):
It is the angle formed by the intersection of the Frankfort
horizontal plane with the mandibular plane. The mean
value is 250
Incisor mandibular plane angle (IMPA):
It is angle formed by the intersection of the long axis of the
lower incisor with the mandibular plane. It indicates the
relative inclination of the lower incisor. The mean value is
900.

Frankfort mandibular incisor angle (FMIA):
It is the angle formed by the intersection of the lower
incisor with the FH plane. The mean value is 650.


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Radiographic cephalometry /certified fixed orthodontic courses by Indian dental academy

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