Cephalometrics

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Contents
Introduction
History
Equipment
Tracing technique
Landmarks
Classification of analysis
Hard tissue & soft tissue analyses

Introduction
A scientific approach to the scrutiny of human craniofacial patterns was first
initiated by anthropologists & anatomists who recorded the various dimensions
of ancient dry skulls. The measurements of the dry skull from osteological
landmarks, called craniometry.
Craniometry was then applied to living subjects so that a longitudinal growth
study could be under taken.
This technique – the measurement of the head of the living subject from the
bony landmark located by palpation or pressing through the supra adjacent
tissue is called cephalometry.

History
Discovery of x-ray - Roentgen - 1895
Images can be measured in two dimension
The measurement of the head from the shadows of bony & soft tissue land
marks on the radiographic image became know as the roentgengraphic
cephalometry ( Krogman & Sassouni)
A teleroentgengraphic technique for producing a lateral head film was
introduced by Pacini in 1922. With this method the size of the image was
decreased by increasing the focus film distance to 2m, but still there was some
distortion because of head movement during prolonged exposure time.

Broadbent & Hofrath (1931) simultaneously presented a standardized
cephalometric technique using a high powered x-ray machine & a head holder
called cephalostat or cephalometer.
In 1968, Bjork designed an x-ray cephalostat research unit with a built in 5”
image intensifier that enabled the position of the patient’s head to be monitored
on a TV screen.
In 1988 a multiprojection cephalometer developed for research & hospital
environments was introduced by Solow & Kreiborg. This apparatus featured
improved control of the head position & digital exposure control as well as a no
of technical operative innovations.

The lateral cephalometric radiograph (cephalogram) also referred as ‘cephs’
itself is the product of a two dimensional image of the skull in the lateral view,
enabling the relationship between teeth, bone, soft tissue, & empty spaces to
be scrutinized both horizontally & vertically. It has influenced the orthodontist in
three major areas.
1. In morphological analyses, by evaluating the sagittal & vertical relationship of
dentition, facial skeleton, & soft tissue profile.
2. In growth analysis, by taking two or more cephalograms at different time
intervals & comparing the relative changes
3. In treatment analysis, by evaluating alteration during & after therapy.

Equipment:
The x-ray apparatus
Comprises an x-ray tube, transformers, collimators & a coolant system, all
encased.
The x ray tube is a high vacuum tube that serves as a source of x ray.
Tungsten filament cathode
step down transformer 10V
Thermionic emission
step up transformer 65-90kV
The differential potential between the cathode & anode accelerates the electron
cloud, which forms the electron beam.

Small tungsten block anode
Copper stem,
Less than 1% of the electron kinetic energy is converted into x ray photons, the
rest is lost as heat
The copper stem acts as a thermal conductor - coolant system
The size of the focal spot, which determines image quality, follows the Benson
line focus principal.
This principle says that the projection of the focal spot perpendicular to the
electron beam, is smaller than the actual focal spot that projects perpendicular
to the target. There fore the target face in the x ray tube is oriented at an angel
of 15 to 20o
to the cathode, which will also increase the image sharpness &
heat capacity of the target. The size area the effective focal spot created by the
inclined target is between 1x1mm2
& 1x2mm2
.

Benson line focus principal.

The divergent x ray beam then passes through a lead diaphragm, the collimator
that fits over the opening of the machine & determines the beam’s size &
shape. Only x ray with sufficient power will reach the patient.
The image receptor system
An image receptor system records the final product of the x ray after they pass
through the subject, the extraoral projection, like the lateral cephalometric
technique, require complex image receptor system that consists of an extraoral
film, intensifying screens, a cassette, a grid & a soft tissue shield.

The cephalostat
Also called a head holder or cephalometer.
The patient head is fixed by the two ear rods that are inserted into the ear
holes so that the upper border of the head, which is centered in the
cephalostat, is oriented with the Frankfort plane parallel to the floor & the mid
sagittal plane vertical & parallel to the cassette. The system can be moved
vertically to accommodate sitting or standing patient. The upper part of the
face is supported by the forehead clamp, positioned at the nasion.
The projection is taken when the teeth are in centric occlusion & the lips in
repose. The focus film distance is usually 5 feet & usually left side of the head
to face cassette.

TRACING TECHNIQUE
Tracing supplies & equipments.
1. Lateral cephalogram usual dimension of 8x12 inches
2. Acetate matte tracing paper 0.003” thick
3. Sharp 3H drawing pencil
4. Masking tape
5. Few sheets of black cardboard & hallow cardboard tubes
6. Dental casts trimmed to maximal intercuspation of the teeth in occlusion
7. View box ( variable rheostat )

General considerations for tracing
Draw tree registration crosses, 2 within the cranium & one over the area of the
cervical vertebrae.
patient’s name, record no, age in years & month, the date of cephalogram was
taken & doctor's name in the bottom left hand corner of the acetate tracing.

Stepwise Tracing Technique
Section 1. soft tissue profile, external cranium, vertebra
Section 2. cranial base, internal border of cranium, frontal sinus & ear rods
Section 3. maxilla & related structures including nasal bone & pterygomaxillary
fissures
Section 4. the mandible

Reference points
N nasion
S Sella
porion
Sn Subnasale
Point A
prosthion
Id Infradentale
B point B
Pog Pogonion
Gn Gnathion
Go Gonion
Me Menton

Ar Articulare
Cd Condylion
Or Orbitale
ANS anterior nasal spine
PNS Posterior nasal spine
Ba basion
Ptm Pterygomaxillary fissure

REFERANCE LINES
S-N sella –nasion. Anterioposterior extent of anterior cranial base.
S – Ar. Lateral extent of cranial base
Ar – Go. Length of ramus.
Me – Go. Extent of mandibular base
S – Gn. Y – axis.
S – Go. Posterior facial height
S – S’. perpendicular from point S to palatal plane. Expression for the
deflections of maxillary base.

Reference angles
N-S-Ar saddle angle
S-Ar-Go articular angle
Ar-Go-Me gonial angle
Ar-Go-N GO1 upper gonial angle
N-Go-Me Go2, lower gonial angle
SNA anteroposterior position of maxilla
SNB anteroposterior position of mandible
S-N-Pr anteroposterior position of alveolar part of premaxilla
S-N-id anteroposterior position of alveolar part of mandible
Pal – occ upper occlusal plane angel
Mp-occ lower occlusal plane angle

Classification of analyses
1. Methodological Classification
2. Normative classification
3. Classification according to the area of analysis

1. Methodological Classification –
The basic unit of analysis are angles & distances. Measurement in degrees
or millimeters may be treated as absolute or relative, or may be related to
each other to express proportional correlations
1. Angular analyses- the basic units are angle degrees
a. Dimensional Analysis is based on comparison of various angels in
isolation, comparing them with average figures.
E.g. Downs analysis is of this type

b. Proportional Analysis is based on comparison of various angles to
establish significant relation between the separate parts of the facial skeleton
E.g. Koski’s analysis belongs to this group

c. Analysis To Determine Position.
Angular measurement may also be used to determine the position of facial
skeleton.
The SNA and SNB angles give the relations between the maxillary and
mandibular bases and the cranial base.

2. Linear analyses
a. Orthogonal analyses. A reference plane is established, with the
various reference points projected on to it perpendicularly, after which the
distances between the projections are measured.
Illustrative & suitable for teaching but not for diagnostic purposes.
E.g. Sassouni analysis

b. Dimensional linear analyses are based on evaluation of certain
linear measurements, either direct or in projection.
The direct method gives certain linear measurements e.g. the length of the
mandibular base, as the distance between the two reference points.
Projected linear dimensional analyses determine the distance between
certain reference points that have been projected onto a reference line.
c. Proportional linear analyses are based on relative rather than
absolute values. The different measurements are compared to each other,
without reference to norms

2. Normative classification- classified according to the concepts on which
normal values have been based.
1. Mononormative analyses
Arithmetical or geometrical averages serves as the norns.
The arithmetical norms are average figures based on angular, linear or
proportional measurements.
The geometrical norms are average tracings on a transparent sheet.
Assessment consists in comparing these with the case under analysis.

2. Multinormative analyses
For these, a whole series of norms are used, with age & sex taken into
account.

3. Correlative analyses
These are used to assess individual variation of facial structure to
establish their mutual relationships. Most suitable for diagnostic purposes.

3. Classification according to the area of analysis
1. Dentoskeletal analyses.
These analyze the dental or skeletal structure. They may be made from
norma lateralis, norma frontalis, or three dimensionally.
2. Soft tissue analyses
These may involve the whole profile in norma lateralis, or certain
structures only.
3. Functional analyses
May also be used to assess functional relations such as the occlusion to
intraocclusal space relationship.

Downs analysis
Downs undertaken a study to determine the range of the facial and dental
pattern within which one might expect to find the normal, and further to
discover whether any usable correlations exists in such normals.
The control material studied was derived from 20 living individuals of age
between 12 to 17years and of both sex(10 each).
All individuals possessed clinically excellent occlusions.
Models, photographs, and cephalograms were taken.
Tracings were made of all lateral head x rays taken with the teeth in occlusion
and the Bolton triangle is outlined in each tracing according to Broadbent’s
technique, which consists of connecting the points, nasion to the center of
sella turcica and sella to the Bolton point, which is the superior point on the
concavity behind the occipital condyles.

The anatomical points and planes
used to describe the skeletal and
dental patterns.
Bolton triangle represents the area at the base of the cranium to which
face is joined. It is believed by the Broadbent to be the most stable area
from which to make serial comparisons.

Downs used Frankfort horizontal plane as the reference plane to determine the
degree of retrognathism, orthognathism or prognathism.
FH is a horizontal plane running through the right and left cephalometric porion
and the left orbitale.
SKELETAL PATTERN
Facial angle (87.80
)
Angle of convexity (00
)
A-B plane (-4.60
)
Mandibular plane angle (21.90
)
Y-(growth) axis (59.40
)
DENTAL PATTERN
Cant of occlusal plane.
Interincisal angle (135.40
)
Incisor occlusal plane angle (14.50
)
Incisor mandibular plane angle (1.40
)
The protrusion of maxillary incisors
(+2.7mm)

Facial angle
This is the inferior inside angle in
which the facial line (nasion
pogonion) intersect the FH plane.
It is used to measure the degree of
retrusion or protrusion of the lower
jaw.
Mean reading: 87.80
S.D. 3.6
Range: 82 to 95 degrees

Angle of convexity.
Formed by the intersection of the line N
- point A to point A - pogonion.
This angle measures the degree of
maxillary basal arch at its anterior limit
(point A) relative to the total facial
profile (nasion-pogonion).
A positive angle suggests prominence
of the maxillary base relative to the
mandible. A negative angle in
prognathic profile
Mean reading: 00
Range: -8.5 to +10 degrees

A-B plane
Points A and B are joined and when
the line is extended , the angle formed
with the line N-pog is read.
Is the measure of the relation of the
anterior limit of the apical bases to
each other relative to the facial line.
Mean reading: - 4.6 degrees
Range: -8.5 to +10 degrees

Various methods of constructing
mandibular planes
1. Gonion – Gnathion ( Steiner )
2. Gonion – Menton
3. Tangent to the lower border of
the mandible ( Downs )

Mandibular plane angle
Downs considered mandibular plane
as tangent to the gonial angle & the
lowest point of the symphysis.
The Mandibular plane angle is
established by relating the MP to FH
plane.
High Mandibular plane angle occurs in
both retrusive & protrusive faces & are
suggestive of hyperdivergent facial
patterns.
Mean reading: 21.90
Range: 17 to 28degrees

Y-(growth) axis
is the measure of the acute angle formed
by the intersection of a line from the sella
turcica to gnathion with the FH plane.
The Y-(growth) axis indicates the degree
of downward, rearward, or forward
position of the chin in relation to upper
face.
A decrease in Y-(growth) axis in serial
radiographs may be interpreted as a
greater horizontal than vertical growth
pattern.
Mean reading: 59.40

Cant of occlusal plane.
Downs originally defined the occlusal
plane as that line bisecting the
overlapping cusps of the first molars &
incisor overbite.
The cant of occlusal plane is measure of
the slope of the occlusal plane to the FH.
When the anterior part of the plane is
lower than the posterior, the angle would
be positive. Large positive angles are
found in classII facial patterns. Long rami
tend to decrease this angle.
Mean reading: 9.340
Range: +1.3 to +14 degrees
DENTAL PATTERN

Interincisal angle
Is established by passing a
line through the incisal edge
& apex of the root of the
maxillary & mandibular
central incisors.
This angle is relatively small
in individuals whose
anteriors are tipped forward
on the denture base.
Mean reading: 135.40

Incisor occlusal plane angle
relates the lower incisor to
their functional surface at the
occlusal plane. The inferior
inside angle is read as either
positive or negative deviation
from a right angle.
The positive angle increases if
these teeth are inclined
forward.
Mean reading: 14.50
Range: 3.5 to 20 degrees

Incisor mandibular plane
angle
is formed by the intersection
of the mandibular plane with
a line passing through the
long axis of the incisor.
Mean reading: 91.40
Range: 81.5 to 97 degrees

The protrusion of maxillary incisors
is measured as the distance between the incisal
edges of the maxillary central incisor to the line
from point A- pogonion line & indicates the
maxillary dental protrusion.
This distance is positive if the incisal head is
ahead of the point A-pogonion line. Indicates the
amount of maxillary dental protrusion.
The reading is negative if the maxillary incisal
edge lies behind the point A-pogonion line and
suggests a retruded position of the maxillary
incisors.
Mean reading: 2.7mm
Range: -1 to +5mm

The polygon
Because of the difficulty of
developing a suitable
mental picture of a sizable
table of figures, Vorhies &
Adams 1951 developed a
polygon or wiggle that
express a large group of
cephalometric readings
graphically.

Steiner analysis
Steiner elected to use the anterior cranial base (sella –nasion ) as the line of
reference to which the jaws would be related. The advantage of these to
midline point is that they are moved only a minimal amount whenever the head
deviates from the true profile position.
The skeletal analysis
Dental analysis
Soft tissue analysis

THE SKELETAL ANALYSIS
Maxilla
Points A & B are regarded as the
anterior limits of the apical bases
of the maxilla & mandible.
Therefore to determine whether
the maxilla is positioned anteriorly
or posteriorly to the cranial base,
the angle SNA is noted.
If the angular reading is greater
than 820
, it would indicate a
relative forward positioning of
mandible.

Mandible
To assess whether the
mandible is protrusive or
recessive to the cranial
base, the SNB angle is
read.
An angle less than 800
indicates the retrusive
mandible.

Relationship of maxilla to mandible
By noting the SNA & SNB readings the offending jaw can usually be
pinpointed. The more significant reading, however, is the ANB
reading, which provides the relative position of the jaws to each
other.

Occlusal plane
The occlusal plane is drawn
through the region of the
overlapping cusps of the first
premolars& first molars.
The angle between occlusal
plane to S-N is measured.
The mean reading for normal
occlusion is 140
.

Mandibular plane
Is drawn between gonion &
gnathion. The mandibular plane
angle is formed by relating it to
the anterior cranial base.
Mean reading 320
.
Excessive high or low
mandibular plane angles
suggest unfavorable growth
pattern.

DENTAL ANALYSIS
Maxillary incisor position
The upper incisor to N –A
reading in degrees indicates the
relative angular relationship of
the upper incisor teeth, where as
the upper incisor to N –A reading
in the millimeter provides
information on the relative
forward or backward position of
the incisor teeth to the N-A line.

Mandibular incisor position
The lower incisor to N-B
measurement in millimeters
shows the relative forward or
backward positioning of these
teeth to the N-B line, in degrees
indicate the relative axial
inclination of these teeth to the N-
B line

Interincisal angle
1300

Lower incisor to chin
The degree of prominence of the
chin contributes to the
determination of the placement of
the teeth in the arch.
Ideally according to Holdaway, the
distance between the labial
surface of the lower incisor to the
N-B line should be equal i.e.,
4mm.

SOFT TISSUE ANALYSIS (Steiner’s)
The soft tissue analysis is basically a graphic record of the visual
observations made in the clinical examination of the patient. The soft tissue
analysis includes an appraisal of the adaptation of the soft tissue to the
bony profile with consideration to the size, shape, & posture of the lips as
seen on the lateral head film.

According to Steiner the lips in well balanced faces, should touch a line
extending from the soft tissue contour of the chin to the middle of an S
formed by the lower border of the nose. This line is referred as S line.
Lips located beyond this line tend to be protrusive, in which case the teeth
&/or jaws usually require orthodontic correction.

Is a measure of the extent to which the
jaws are related to each other.
Perpendicular lines from point A & point
B are drawn to the occlusal plane,
which is drawn through the region of
overlapping cusps of 1st
premolars & 1st
molars. Point BO is approx 1mm ahead
of point AO in men, & in women they
generally coincided.
Wits appraisal

McNamara analysis
This method of cephalometric analysis is conventional in nature in that it
consists of a predetermined set of measurements of angles and distances
applied to each cephalometric tracing.
This analysis method is useful in the diagnosis and treatment planning of
the individual patient when the values derived from the tracing of the
patient's initial head film are compared to established norms.
He considered three sample groups for his analysis.
The first sample contains normative data derived from lateral cephalograms
of the children comprising the Bolton standards, the longitudinal records of
whom were retraced and digitized by Behrents and McNamara to include all
the landmarks necessary for the this analysis.

The second sample contains selected values from a group of normal children
from the Burlington Orthodontic Research Centre who also were followed
longitudinally.
The third group considered is the Ann Arbor sample of 111 young adults who,
in the opinion of his co-workers and himself, have good to excellent facial
configurations.
Patients in this latter group had a Class I occlusion and good skeletal balance
with an orthognathic facial profile.
The average age of the females in the sample was 26 years 8 months, while
the average age of the males was 30 years 9 months at the time the
cephalogram was taken.

In an effort to create clinically useful analysis, the craniofacial skeletal
complex is divided into 5 major sections.
1 Maxilla to cranial base
2 Maxilla to mandible
3 Mandible to cranial base
4 Dentition
5 Airways

Maxilla to cranial base
The position of the maxilla in the skull first should be assed clinically by
observing the soft tissue profile, and then by evaluating by various lateral
ceph measurement to normative standards.

Hard tissue evaluation
The construction of the nasion
perpendicular is accomplished by first
defining the Frankfort horizontal plane
using anatomic porion (the superior
aspect of the external auditory meatus)
and orbitale (the lower border of the orbit
of the eye) as reference points. To which
a perpendicular line is dropped from the
nasion.
To determine the anteroposterior orientation of the maxilla relative to the
cranial base, the linear distance is measured between nasion perpendicular
& point A. In a well balanced faces, this measurement is 0mm in mixed
dentition & 1mm in adult.

Soft tissue evaluation
The nasolabial angle & the cant of the
upper lip should be examined. Average
nasolabial angle 1020
SD 80
The cant of upper lip should be slightly
forward to form an angle of about 140
SD 80
in women & 80
SD 80
in men with
the nasion constructed perpendicular.

Maxilla to mandible Anteroposterior relationship
A linear relationship exists between the
effective length of the midface & that of the
mandible. Any given effective midfacial
length corresponds to an effective
mandibular length within a given range.
To determine the maxillomandibular
differential, the midfacial length is
substracted from that of the effective
mandibular length this difference should
be between 20 & 23mm in small individual
(mixed dentition stage), & 27 to 30mm in
large individuals.

Vertical relationship
Lower anterior facial height is measured
from ANS to menton.
In a well balanced faces, the vertical
dimension correlates with the effective
length of the midface (Co-point A)
An increase or decrease in the lower anterior facial height can have a
profound effect on the horizontal relationship of the maxilla and mandible.
For example, if the mandible is rotated downward and backward
concomitant with a 15 mm increase in lower anterior facial height the chin
point moves away from the nasion perpendicular

If lower anterior facial height is increased, the mandible will appear to be
more retrognathic. If lower anterior facial height is decreased, the mandible
will appear to be more prognathic.
In a growing person an increase in lower anterior facial height will
camouflage a similar increase in mandibular length, which may result in the
appearance that the chin is in the same relationship anteroposteriorly to
cranial base structures.

Normative standards in
McNamara’s analysis

Mandibular plane angle is the
angle between anatomic FH & the
line drawn along the lower border
of the mandible through
constructed gonion & menton.
On average, the mandibular
plane angle is 22 degrees +/-
4degrees.
A higher measurement
suggestive of excessive lower
face height, whereas a lesser
angle would tend to indicate a
deficiency in lower face height.

The facial axis angle is the angle
formed by line constructed from
the posterosuperior aspect of the
PTM to gnathion relative to the
cranial base, which is represented
by a line joining basion to nasion.
In a balanced face, the facial axis
angle is 90degrees.

The relationship of the mandible to
cranial base is determined by
measuring the distance from
pogonion to nasion perpendicular. In
individuals with medium sized face ,
such as an adult woman, pogonion is
positioned 4-0mm behind the nasion
perpendicular line. And the large
individuals, such as adult men, the
measurement of the chin position
extends from about 2mm behind to
approx 2mm forward of the nasion
perpendicular line.
Mandible to cranial base

Maxillary incisor position
To measure position of maxillary
incisors, a vertical line is drawn
through point A parallel to nasion
perpendicular. The distance from
point A to the facial surface of the
upper incisor is measured.
Dentition
In planning the orthodontic treatment, one must determine the
anteroposterior position of both upper & lower incisors.

Mandibular incisor position
To determine the anteroposterior
position of the lower incisor, the
distance is measured between the
edge of the mandibular incisor & a
line drawn from point A to pogonion.
In a well balanced face, the distance
should be 1 – 3mm.

Two measurements are used.
Upper pharynx
Upper pharyngeal width is measured
from a point on the posterior outline of
the soft palate to the closest point on
the pharyngeal wall. This measurement
is taken on the anterior half of the soft
palate outline. The average
nasopharynx is approx 15 -20 mm in
width, a width of 2mm or less in this
region indicates airway obstruction.
Airway analysis

Lower pharynx
Lower pharyngeal width is
measured from the point of
intersection of the posterior border
of the tongue & the inferior border
of the mandible to the closest point
on posterior pharyngeal wall. The
average measurement is 11 – 14
mm, independent of the age.

HARVOLD ANALYSIS
Harvold, using data derived from the Burlington growth study, developed
standard for the ‘unit length’ of maxilla and mandible. The maxillary unit length
is measured from the posterior border of mandibular condyle to the ANS,
while the mandibular unit length is measured from the same point to the
anterior point of the chin. The difference between these no provide an
indication of size discrepancy between the jaws

ENLOW’S COUNTERPART ANALYSIS
Enlow et al pointed out that, both the dimensions and alignment of craniofacial
components are important in determining the overall facial balance.
If anterior facial height is long, facial balance and proper proportions are
preserved if posterior face height and mandibular ramus height also are
relatively large.
On the other hand, short posterior facial height can lead to a skeletal open bite
tendency even if anterior face height is normal, because the proportionality is
disturbed.
The same is true for anteroposterior dimension

If the maxilla is long
(measurement 6), there is no
problem if mandible is also long
(measurement 7), but
malocclusion will results if the
mandibular length is merely
normal. The same would be true
for anterior vs posterior vertical
dimensions (1-3)

Ricketts analysis
The less traditional points, planes, & axes used in the Rickets analysis
Location Of Points
A6 upper molar
B6 lower molar
C1 condyle
CC center of the cranium
CF points from planes of
pterygoid

LOCATION OF XI POINT
a. Locate FH and draw PtV plane
perpendicular to the FH
b. Construct 4 planes tangent to points R-1,
R-2, R-3, & R-4 on the borders of the ramus
c. The constructed plane forms a rectangle
enclosing the ramus
d. Xi point is located in the centre of the
rectangle at the intersection of the diagonals

Definition and location of axe
Facial axis a line extending from the
foramen rotundum (PT-Gn)

Condylar axis extends from DC (the
point on the neck of the condyle
along the Ba-N plane) to Xi point
used to describe the morphologic
features of the mandible

Corpus axis extends from Xi to PM
(suprapogonion) ; used to describe
the morphology of the mandible
and to evaluate dentition changes

INTERPRETATION
CHIN IN SPACE
Facial axis
The angle formed between the
Ba-N plane and the plane from
foramen rotundum to gnathion.
Average angle is 90degrees.
A lesser angle suggests the
retropositioned chin.

Facial (depth) angle
Angle between the facial plane and
FH.
This angle provides some
indication of the horizontal position
of the chin.
It also suggests whether a skeletal
class II or III pattern is due to the
position of the mandible.

Mandibular plane
Measures an angle to FH.
On an average this angle is 260
at
9years of age and decreases
approx 10
every 3 years.
A high or steep mandibular plane
angle implies that an open bite may
be due to the skeletal morphologic
characteristics of the mandible.

Convexity at point A
Convexity of the middle face is
measured from point A to the facial
plane.
The clinical norm at 9 years of age is
2mm and decreases 10
every 5 yrs.
High convexity implies skeletal class
II. Negative convexity implies class
III.
CONVEXITY

Lower incisor to A-pog
The A-pog line is referred to as the
denture plane and is useful reference to
measure the position of the anterior
teeth. Ideally the lower incisor should be
located 1.0mm ahead of the A-pog line
TEETH

Upper molar to PtV
This measurement is the distance from
the pterygoid vertical (back of the
maxilla) to the distal of the upper molar.
On an average this measurement should
equal the age of the patient +3mm.
This measurement assist in determining
whether the malocclusion is due to he
position of the upper or lower molar.
It is also useful in deciding whether
extractions are necessary.

Lower incisor inclinations
The angle between the long axis of the
lower incisor and the A-PO plane is
measured. On the average this angle
should be 280
.gives some idea of lower
incisor procumbency.

Lower lip to E line
The distance between the lower lip and the
esthetic plane is an indication of the soft
tissue balance between the lips and profile.
The average norm for this measurement is
-2mm at 9yrs of age.
PROFILE

UPPER & LOWER GONIAL ANGLE OF JARABACK
The upper gonial angle is
formed by the ascending
ramus and the line joining
nasion and gonion. A large
upper gonial angle suggests
horizontal growth changes,
a large lower gonial angle
suggests vertical growth.

BJORK SUM OF POSTERIOR ANGLES
On average the sum of the three
angles the saddle, articulare, and
gonial angle should be 3960
+/-60
.
If it is greater than 3960
, the direction
of growth is likely to be vertical, if it is
smaller growth may be expected to be
horizontal.

ANTERIOR TO POSTERIOR FACE HEIGHT (JARABACK RATIO)
Posterior face height (S-Go) X
anterior face height (N-Me)
The mean value for this is 62-
65%. A higher percentage
means a relatively greater
posterior face height and
horizontal growth. A small
percentage denotes a
relatively shorter posterior
face height and vertical
growth.

Tweed analysis
Included only three measurement
norms range
FMPA- Frankfort mandibular plane angle 25 16-35
IMPA- Incisor mandibular plane angle 90 85-95
FMIA- Frankfort mandibular incisor angle 65 60-75

SASSOUNI ANALYSIS
The first cephalometric method to emphasize vertical as well as horizontal
relationships & the interaction between vertical & horizontal proportions.
Viken Sassoni studied 100 lateral head x-ray films taken with the Broadbent
– Bolton roentgengraphic cephalometer.
The samples were 51 girls and 49 boys, principally of the Mediterranean
racial origin. The chronological age ranges from 7 years to 15 years. All the
x- ray films are from the files of the Philadelphia Center for Research in Child
Growth.

Sassouni pointed out that the horizontal anatomic planes –
The inclination of the anterior cranial base,
FH plane,
Palatal plane,
Occlusal plane, &
The mandibular plane
tend to converge toward a single point in well-proportioned faces. The
inclination of these planes to each other reflects the vertical proportionality
of the face.

TERMINOLOGY
Planes
Mandibular base plane angle – A plane tangent to the inferior border of the
mandible
Occlusal plane – A plane going through the mesial cusps of the permanent
first upper and lower molar and incisal edges of the upper and lower
central incisors.
Palatal plane – A plane perpendicular to the midsaggital plane, going
through the anterior and posterior nasal spines.

Anterior cranial base – Structurally, the floor of the anterior cerebral fossa. In
the lateral x ray film there are two contours: the upper is the roofing of the
orbit, including the lesser wing of the sphenoid, and the lower is posteriorly
the spheno-ethmoid area and anteriorly the cribriform plate.
Anterior cranial base plane or basal plane – a plane parallel to the axis opf
the upper contour of the anterior cranial base and tangent to the inferior
border of the sella turcica.
Ramal plane – A plane tangent to the posterior border of the ascending
ramus.

Arcs
1. Anterior arc – The arc of a circle, between anterior cranial base plane and
mandibular plane with O as the center and O-ANS as the radius.
2. Posterior Arc – The arc of a circle, between anterior cranial base plane
and mandibular base plane with … as center and OS p
as radius. (S p
is
the most posterior point on the rear margin of sella turcica)

If the planes intersect relatively close to
the face & diverge quickly as they pass
anteriorly, the facial proportions are long
anteriorly & short posteriorly, which
predisposes the individual to open bite
malocclusion. Sassouni coined the term
skeletal open bite for this anatomic
relationship.
If the planes are nearly parallel, so that
they converge far behind the face &
diverge only slowly as hey pass
anteriorly, there is a skeletal
predisposition to anterior deep bite, and
the condition is termed as skeletal deep
bite.

In a well proportioned face,
the ANS, the maxillary incisor,
& the bony chin should
located along the same arc.

Soft tissue analysis
For Soft tissue analysis, distinction is made between
1. Profile analysis
2. Lip analysis
3. Tongue analysis

PROFILE ANALYSIS
Assessment of the total profile
1. Proportional analysis- the profile may be divided into 3 equal parts
Frontal third tr (trichion)-n
Nasal third n-sn
Gnathic third sn-gn

2. Angular profile analysis, convexity of profile
Skeletal profile
Soft tissue profile
Full soft tissue profile including the nose

3. Thickness of the soft tissue profile
Burstone mean values

Bowker and Meredith method of determination

LIP ANALYSIS
Ricketts lip analysis
The reference line used by Ricketts is from the nose tip to the skin pogonion.
Normal is upper lip 2-3mm and the lower lip 1-2mm behind this line.

Steiner’s lip analysis
Upper reference point is the center of the s shaped curve between the tip of
the nose and subnasale. Lower reference point is the soft tissue pogonion.

Holdaway’s lip analysis
This is quantitative analysis. Holdaway determines the angle between a
tangent to the upper lip and NB line, called H angle. With ANB angle 1-30
, the H
angle should be 7-80
.

ANALYSIS FOR THE TONGUE POSITION
Only a limited no of methods are available for analysis of tongue position in
the radiograph.
Reference
I – incisal edge of the lower central incisor
M – cervical, distal third of the lost erupted molar
V – most caudal point on the shadow of the soft palate or its projection onto
the reference line
I and M are connected and the connecting line continues to V
The line connecting I and V is bisected, the point of bisection being point O.
From this, a perpendicular line is drawn to the roof of the mouth.

A transparent template is used for the determinations. This has a horizontal
line which is placed to coincide with the reference line traced on the
radiograph, and a vertical line which should coincide with the vertical
reference line.
From point O on the template, where the three lines meet, another four lines
are drawn, all at 300
angles. This gives a total of 7 lines, and these are
marked out on the millimeters.
Using the template two type of determination can be executed
1. Assessment of tongue position
2. Assessment of tongue motility

Assessment of tongue position
On the radiograph taken in occlusion, the space between tongue and roof of
the mouth is defined by distances in millimeter.
If the lines on the template are numbered from 1-7, the measurement made
along 1 gives the distance between the soft palate and root of the tongue,
those lines along 2-6 gives the relationship of the dorsum of the tongue to the
roof of the mouth, and that along no 7 the position of the tip of the tongue
relative to the lower incisors.

Assessment of tongue motility
The position of the tongue in the dental occlusion is compared with that in
rest position. The template is used to determine the height of the dorsum
of the tongue on all 7 lines, in both radiographs. The difference between
occlusion and rest position is then calculated. This method permits
assessment of the actual change in the tongue position, independent of
the interocclusal space.
The occlusal position is taken as zero, with the changes in the position
given in positive and negative figures, i.e., a positive figure indicates that
the tongue is higher in rest position than in the occlusal position, and vice
versa.

THE RESULT OF TONGUE POSITION ASSESMENT
The root of the tongue (measurement no 1); with the anomalies in the
nasal breathing, a small spacing is found between the root of the tongue
and the soft palate (0.9-2.1mm on average). A space in this region is not
always due to mouth breathing, but may also occur with small tongue, in
cases of deep overbite. A small tongue may sometimes also seen with
class III malocclusion, but it is then in an anterior position, so that the
space between the root of the tongue and the soft palate is large. In cases
of mouth breathing, the space is large(5.1-5.2mm on average).
The dorsum of the tongue is (measurement no 2-6) is relatively high with
class II malocclusion. In cases of deep overbite, the dorsum is high at the
back, low in front. In all other cases dorsum tends to be low.

The tip of the tongue (measurement no 7) is retracted in cases of class III
and class II cases with nasal breathing, and even more so in cases of deep
overbite. With the class II and mouth breathing the tip of the tongue is
considerably retracted, whereas retraction is less with class III and mouth
breathing. In cases of open bite the tip of the tongue lies forward.

Holdaway’s soft tissue cephalometric analysis
In a series of two article Reed Holdaway outlined the parameters of soft
tissue balance. His analysis comprises 11 measurements.
Soft-tissue facial angle
This is an angular measurement of a line
drawn from soft-tissue nasion, where the
sella-nasion line crosses the soft-tissue
profile, to the soft-tissue chin at a point
overlying the hard-tissue suprapogonion of
Ricketts measured to the Frankfort
horizontal plane. A measurement of 91
degrees is ideal, with an acceptable range of
±7 degrees.

Nose prominence.
Next in importance to variations in chin position are variations in noses.
Nose prominence can be measured by means of a line perpendicular to
Frankfort horizontal and running tangent to the vermilion border of the upper
lip. This measures the nose from its tip in front of the line and the depth of
the incurvation of the upper lip to the line.
Arbitrarily, those noses under 14 mm. are considered small, while those
above 24 mm. are in the large or prominent range. Nasal form should be
judged on an individual basis.

Superior sulcus depth
Superior sulcus depth measured to a perpendicular to Frankfort and
tangent to the vermilion border to the upper lip. A range of 1 to 4 mm. is
acceptable in certain types of faces, with 3 mm. being ideal.
This measurement is especially useful in cases found to be on either
extreme of facial convexity where a measurement to the H line (harmony
line) is misleading because of the change in the cant of this line in highly
convex or concave faces.
Observing this measurement and setting treatment
goals accordingly should reduce the number of
orthodontically treated patients who develop an
unpleasant expression in this area as a result of too
much retraction of anterior teeth.

Measurement of soft-tissue subnasale to H line (upper sulcus
depth)
The ideal is 5 mm., with a range of 3 to 7 mm. When the skeletal
convexity of a case will be from – 3 to +5 mm. at retention, the lips can
usually be aligned nicely along the H line when the superior sulcus
measurement is at or near 5 mm. With short and/or thin lips, 3 mm. will
be adequate. In longer and/or thicker lips, 7 mm. may be in excellent
balance.

Skeletal profile convexity.
This is a measurement from point A to the hard-tissue line Na-Pog or facial
plane.
This is not really a soft-tissue measurement, but convexity is directly
interrelated to harmonious lip positions and, therefore, has a bearing on the
dental relationships needed to produce harmony of the features of the
human face.

Basic upper lip thickness
This is near the base of the alveolar process, measured about 3 mm.
below point A. It is at a level just below where the nasal structures
influence the drape of the upper lip. This measurement is useful, when
compared to the lip thickness overlying the incisor crowns at the level of
the vermilion border, in determining the amount of lip strain or
incompetency present as the patient closes his or her lips over protrusive
teeth.

Upper lip strain measurement.
The usual thickness at the vermilion border level is 13 to 14 mm.
Excessive taper is indicative of the thinning of the upper lip as it is
stretched over protrusive teeth; also, excessive vertical height may
produce more than 1 mm. of taper due to lip stretching.
When the lip thickness at the vermilion border is larger than the basic
thickness measurement, this usually identifies a lack of vertical growth of
the lower face with a deep overbite and resulting lip redundancy.

H angle.
This is an angular measurement of the H line to the soft-tissue Na-Po line or
soft-tissue facial plane.
Ten degrees is ideal when the convexity measurement is 0 mm. However,
measurements of 7 to 15 degrees are all in the best range as dictated by the
convexity present. Ideally, as the skeletal convexity increases, the H angle
must also increase if a harmonious drape of soft tissues is to be realized in
varying degrees of profile convexity.
The H angle, when considered with the basic
skeletal convexity of a face and sulcus depth
measurements, can be used as a guide in planning
the anteroposterior position of the denture to give
proper lip support and a natural unstrained drape of
the soft tissues covering the denture area of the
face. www.indiandentalacademy.comwww.indiandentalacademy.com

Table

Lower lip to H line
The ideal position of the lower lip to the H line is 0 to 0.5 mm. anterior, but
individual variations from 1 mm. behind to 2 mm. in front of the H line are
considered to be in a good range.
When the lower lip is situated behind the H line, the measurement is
considered to be a minus figure. A lower lip measurement of much more
than – 1 mm. when other profile measurements are only reasonably good
is indicative of lower incisors that are positioned too far lingually.
When the lower lip rolls out more than 2 mm.
beyond the H line, the denture is usually
protrusive, or at least the upper incisors are
protrusive, and an excessive overjet and/or
overbite is present.

Inferior sulcus to the H line.
The contour in the inferior sulcus area should fall into harmonious lines
with the superior sulcus form. This is measured at the point of greatest
incurvation between the vermilion border of the lower lip and the soft-
tissue chin and is measured to the H line .
It is an indicator of how well we manage axial inclinations of the lower
anterior teeth.

Soft-tissue chin thickness (10 to 12 mm. average).
This is recorded as a horizontal measurement and is the distance
between the two vertical lines representing the hard-tissue and soft-
tissue facial planes at the level of Ricketts' suprapogonion.
Usually, these lines diverge only slightly from the area of nasion down
to the chin.

Cephalometrics

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