Cephalomatrics in orthodontics/ dental implant courses

CEPHALOMETRICS
IN
ORTHODONTICS
www.indiandentalacademy.com

CONTENTS
 Introduction
 Historical aspect
 Advantages and limitations
 Radiographic cephalometric technique
 Quality of the radiographs
 Protection from radiation
 Bibiliography.

INTRODUCTION
 Cephalometrics includes measurements, description and
appraisal of the morphologic configuration and growth
changes in the skull by ascertaining the dimensions of
line angles and planes between anthropometric land
marks established by physical anthropologists and points
selected by orthodontists.

HISTORICAL ASPECT.
 Cephalometry comes under the branch of
anthropometry with craniometry. There were
the physical anthropologists who firstly
introduced the lines or angles in measuring
the face and correlating them with each other.
 Humanity has studied itself in perpetuity,
always with a recognition of the intimate link
between the spiritual & the physical.

 Historically, the human
form has been measured
for many years .One has
been to aid humanity’s
self portrayal in sculpture,
drawing & painting.
Another has been to test
the relation of physique to
health, temperament ,&
behavioural traits.

 Orthodontists have contributed to this ongoing
effort with their study of the human face and
profile , in search of guidelines for the
reconstruction of facial dysmorphology & the
correction of malocclusion. The building blocks
for these studies have been assembled since
antiquity & even include attempts to decipher the
make up of personality traits

Classifying physiques
 In 500 B.C. the Greek physician & father of
medicine HIPPOCRATES, designated two
physical types: habitus phthisicus (long, thin
body) & habitus apoplecticus (short, thick
individual)
 Search was continued by Aristotle(400 B.C.),
Galen (200 A.D.) & Rostan (1828), who was the
first to include muscle mass as a component of
physique

 Kretschmer (1921) three greek terms:
pyknic(compact), asthenic(without
strength), athletic.

Measurement & proportion
 Portrayal of the human form demands not only,
artistic talent and technical ability but a
disciplined & consistent style. To ensure these
stipulations when images of royalty and deity
were commissioned and executed,the ancient
egyptians developed an intricate quantitative
system that defined the proportions of the
human body . It became known as a canon.

 The canon is drawn with
the head, feet, and legs in
profile and the torso in
front view. The unit of
measurement for
determining the height of
the figure, as well as
intermediate anatomic
levels such as the knee,
trunk, axle, and shoulder,
as the length of the foot.
 The construction of images in two dimensions (ie,
planar) was based on a module showing landmarks
through which base lines were drawn.

 The proportions of the human body were
determined with an “ell” measuring ruler,
established in 3,000 BC. Its length
corresponded to the distance from the
elbow to the outstreched thumb (448.8
mm) and included markings for the fist,
wrist, and finger breadths.

 Indian iconometry, studied extensively by
Ruelius was transmitted through Sanskrit
literature.
 In this, face height was used as a module
of both the Sariputra & Alekhyalaksana
proportional systems, which closely
reflected the natural relation of parts of the
body to each other.

 Sariputra system, dated 1200
A.D., is known for the
sculptures honoring the God
Buddha
 Front view of the head of a standing statue
of the God Buddha according to the highly
detailed proportional system of Sariputra.


Tibetan construction scheme
 Buddhist iconometric texts have been translated in Tibet, where proportions were modified &
adapted to the needs of tibetan art & even refined .

 In Byzantine empire, the
rectangular grid of the cannon
was replaced by a scheme of
three cocentric circles, with
nose length as the radius for
drawing the two successive
circles.Inner circle outlined the
brow & cheeks. Second circle,
with a radius of two nose
lengths, defined the exterior
measurements of the head,
including the hair & the lower
limit of face. Outermost circle
cut through the pit of the throat
& formed a halo.
 Three concentric-circle module
system of Byzantine art. Nose
length was used as the radius
for its construction.

Renaissance to
Twentieth Century
 The fifteenth century’s breakthrough in
artistic thought, concept, and technique
was exemplified vividly by the
accomplishments of Leonardo da Vinci
(1459-1519) and AlbrechtDürer (1471-
1528).

 His drawings include a study of
facial proportions and the
projection of a coordinate system
on the face of a “horseman”.
 Leonardo da Vinci. Torso of man
in profile,with study of proportions
of face & head

 Using strictly geometric
methods, Dürer provided a
proportionate analysis of the
leptoprosopic (long) face and
the euryprosopic (broad) face
in a coordinate system, where
the horizontal and vertical lines
were drawn through the same
landmarks or facial features .
 Durer's proportional analysis of a leptoprosopic
(long and narrow) face and a euryprosopic (broad
and short) face in a coordinate system constructed
according to the location of landmarks and facial
features.

 In a proportionate analysis of the face of two individuals, Durer highlighted the differences in the
profile outline by the angle between a line drawn tangent to the forehead and nose and a line
drawn tangent to the chin and the lower lip.

 Petrus Camper (1722—
89), anatomist, physician,
and scientist made
extensive studies of
crania . The key to his
methodology was to
orient crania in space on
a horizontal from the
middle of the porus
acusticus to a point below
the nose.

 Camper’s horizontal became the
reference line for the angular
measurements used to characterize
evolutionary trends in studies of facial
morphology and aging.

 The terms prognathic and orthognathic
introduced by Retsius are tied to Camper’s
illustrations of facial form in man and primates.
As a result, the angle between a horizontal
line and the line nasion—prosthion became-
the time-honored anthropological method to
determine facial type. The term prognathism
refers to the prominence of the face, or jaws,
relative to the forehead, and a straight facial
profile became labeled as orthognathous.

 Camper also provided
a variety of other
differences in facial
form by comparing
the skull morphology
of a tailed Simian, an
orangutan, a young
native African, and a
Kalmuck .

 Welcker’s (1862) elaborate studies of
growth and development of the human
skull showed the effect of various
manipulations during childhood to modify’
the shape of the neurocranium.

 Welcker also
demonstrated the
descent and rotation
of the mandble during
ontogenesis, by
means of a triangular
configuration from
basion to gnathion.
 Orientation of the skull by means of a
horizontal from prosthion tangent to the
occipital condyle.

 That triangular
schematic was later
modified to a polygon
by Hellman to depict
facial growth and to
examine differences
among individuals
with class II & III
malocclusions.
 Analysis of facial growth proposed by
Hellman,22 utilizing a polygon and the line
from nasion to auriculare as reference

 After Hellman, the polygon was used by
Korkhaus in Bonn and thereafter by Bjôrk.
 Bjôrk developed his polygon method into what
may be termed a “shapespace” analysis of the
facial skeleton. This analysis clearly illustrated
the facial configuration under the skull base to
the mandibular plane and from the
temporomaxillary joint to the profile.

Twentieth century
 The evolution of cephalometry in the twentieth
century is universally linked to Edward Angle’s
publication of his classification of malocclusion
(1899).
 This scheme used the relationship between the
maxillary and mandibular dental arches,
exemplified by the intercuspation of the
permanent first molars, as a basis for
characterizing the types of malocclusion.

 Roentgen’s discovery of Xrays in
1895 opened new doors in finding the
answers to the questions that other
relatively limited technique were unable
to answer.
 In 1921 Pacini published a paper
entitled “Roentgen Ray Anthropometry
of the skull” in which he described a
technique of producing and measuring
radiographs of both dried skull and
living patients.
 Pacini identified certain land marks
on xrays Go, Pog, Na and ANS. The
estimated centre of sella.www.indiandentalacademy.com

 The Dutchman, Vanloon(1915) is said
to be the first introducing anthropology
in to orthodontics. He made a plaster
cast of the entire face in which, models
of the dentition were inserted oriented
with help of cubus craniophorus (Device
used by anthropologists to study the
crania orbital plane) by P.Simon in
1922.
 In 1929, the world’s anthropologists met
and agreed on the definition of the
Frankfort horizontal plane.

 In 1931, Broadbent(USA) and Hofrath
(Germany) simultaneously presented
standardized cephalometric technique using
a high powered xray machine & a head
holder called cephalostat or cephalometer.
The principle involved was a constant focal
spot to object distance (5ft./152.4cm) and
preferably a constant, object to film distance.
 Lucien de coster of belgium (1939) was the
first to publish an analysis based on
proportional relationship in the face
conforming to principles used in antiquity.

Divine proportion
 In the divine proportion, developed by Greek
mathematicians, the length of a line is divided into two
parts such that the minor part divided by the major part
equals the major part divided by the total. For the
division of the total into unequal parts to appear as
proportional, the smaller part must relate to the larger as
the larger part relates to the total. In reverse, the relation
of the total to the major part must be the same as that of
the major part to the minor.
 Given its name by Pacioli, a mentor of Leonardo
DaVinci, this phenomenon has unique properties, and it
seems so mystical in its qualities

 In the divine proportion, or golden cut, the
major part is 1.61803 times larger then
the minor part. The Greek letter phi, the
initial letter of Phidias Pythagoras' first
name, has been adopted to designate the
golden ratio.

 In 1509, Luca Pacioli, Pastor,
Tutor, and Professor of the Holy
Theology, presented an oration on
the golden proportion from the
mathematical sciences. Its
publication contained a drawing of
the face in profile, oriented in
natural head position and
inscribed in a golden triangle and
a golden rectangle .
 Mans face in profile encased in a
golden triangle and a golden
rectangle.

 Paradies demonstrated that the golden section is the key to
determining the lower face height in the rehabilitation of the
edentulous.
 Ricketts was the first in recent history to expound in detail on the
divine proportion and the Fibonacci series as they relate to the face
in norma frontalis and norma lateralis, and to the growth of the face.
 The sectio aurea, or the divine proportion, observed in many
creations of nature also pertains to a variety of facial dimensions in
the norm mesh diagram of 18yearold American women.
 Sectio Aurea (distances) Minor/Major = Major/Total = 1.618034

 In the search to define guidelines
for diagnosis and treatment
planning according to esthetic
principles of facial harmony, Brons
studied the ideal relations among
the parts of the soft tissue profile
outline in adults . He reported that
in the harmonious profile outline,
the ratio of upper face height to
maxillary alveolar height
(subnasale to stomion) to
mandibular face height (the
distance from stomion to gnathion)
is 1 : 0.61 : 1—the golden
proportion
 An optimal and harmonious profile
configuration that exhibits the
divine proportion between upper
face height

 William B.Downs (1947) he completed a
landmark study “variations in facial
relationship : their significance in
treatment and prognosis” which come to
known as Downs analysis
 Richard A. Riedel (1922-1994) introduced
one of the most widely accepted
diagnostic cephalometric measurements
in use: ANB angle

 Cecil C. Steiner (1953) published his analysis.
That offer specific guide for the use of
cephalometric measurements in treatment
planning ,based on what compromises in incisor
positions would be necessary to achieve normal
occlusion when the ANB angle was not ideal
 Tweed (1954), constructed a triangle formed by
lower central incisor, mandibular plane, and
frankfort horizontal plane.
 In 1968, Bjork designed X-ray cephalostat in
which patients head position was highly
reproducible.

 More recently, in 1988 a multiprojection
cephalometer developed by Solow &
Kreiborg. This apparatus featured improved
control of head position and digital exposure
control as well as number of technical
operative innovations.
 Dr. Robert M.Ricketts first introduced the
computer in Orthodontic Cephalometry,
Computerized Cephalometry has number of
advantages over conventional one of being
less time consuming, lesser chances of error
and easy storage and retrieval of
cephalometric values and tracings.

ADVANTAGES
 Study Casts – information of dental structures
 Facial photographs – surface features
 But only cephalometric images yield accurate
information on the spatial relationships between
surface and deep structures.
 This is relatively non- invasive, non-destructive,
high information yield at relatively low
physiologic cost. It rendered serial assessment
of growth possible and permitted investigators
to monitor the ongoing procedures of treatment
and growth in vitro.

 Important in orthodontic growth
analysis,diagnosis, treatment planning,
monitoring of therapy, and evaluation of
final treatment outcome.
 Cephalographs provide additional
radiographic information mediolaterally,
which is particularly useful for
presurgical and asymmetric growth
evaluation.

LIMITATIONS
1. Radiation exposure
2. Absence of anatomical references whose
shape and location remain constant
throughout time.
3. Lack of sufficient standardization in current
image acquisition and measurement
procedures.
4. Cephalograms are 2 dimensional pictures of
3 dimensional objects. It leads to different
projective displacement of anatomical
structure lying at different parts.www.indiandentalacademy.com

RADIOGRAPHIC CEPHALOMETRIC
TECHNIQUE
 The basic components of the equipment
for producing a lateral cephalometric are:
 1. An X-ray apparatus
 2. An image receptor system
 3. A cephalostat.

X-ray Apparatus:-
comprises of X-rays tube,
transformers, filters,
collimators, and a coolant
system, all encased in the
machine’s housing.
 The three basic elements
that generate the X- rays
a. a cathode
b. an anode
c. the electrical power supply
 X-ray tube head

Cathode:- is a tungsten filament
surrounded by a molybdenum
focussing cup. And serves as
a source of electrons.
Anode:- Consist of a tungsten
target embedded in a copper
stem. The purpose of the
target in an x ray tube is to
convert the kinetic energy of
the electrons generated from
the filament in to x ray
photons.

 Less than 1 % of the electron kinetic energy
is converted to the x rays photons.
 The size of the focal spot , which
determines image quality. The target face in
the x ray tube is oriented at an angle of 15
to 200
to the cathode .
 The size or area of the effective focal spot
created by the inclined target is between
1x1 mm2 and 1x2 mm2 .

 the low- energy photons are
filtered out by means of an
aluminium filter
 The divergent x ray beam then
passes through a lead
diaphragm(collimator) that fits
over the opening of the
machine housing and
determine the beam’s size and
shape.
 Only x ray with sufficient
penetrating power are allowed
to reach the patient

c. Electric power supply :-
the primary function of the power supply of an x
ray machine are to
1. provide a low voltage current to heat the x
ray tube filament by use of an step- down
transformer
2. generate a high potential diff. between the
anode and cathode by use of a high- voltage
transformer

 Image Receptor system : Extra oral
projection like lateral ceph. requires a
complex image receptor system that
consists of an extra oral film, intensifying
screens, a cassette, a grid and soft tissue
shield.
 Extra oral film is a screen film, size
ranging from 8x10 inches to 10x12
inches. Basic component of the film are
an emulsion of silver halide crystals
suspended in a gelatin frame work and a
transparent blue- tinted cellulose acetate
that serves as a base.www.indiandentalacademy.com

Silver halide → Metallic silver → film → Visible &
Crystals exposed ↓↓ processing permanent
to X-rays Latent image image
Intensifying Screens: Phosphorescent crystals such
as Ca tungstate & Barium lead sulfate coated
onto a plastic support.
- Exposed to X-ray beam- emit fluorescent light-
can be recorded by screen film
Decreases patient exposure dose.
-- Increases contrast by intensifying the photographic
effect.

 Grid: - To prevent the fogging.
Comprising alternate Radio-opaque
(usually lead) and strips of radiolucent
material (often plastic) and placed
between subject and film.
 R.O. of Lead foil – act as absorber
 R.L. of Plastic – allow the primary
beam to pass through the film .

 Soft Tissue Shield: - is an aluminium
wedge that is placed over the cassette in
order to act as a filter and reduce over
penetration of the X-rays into the soft
tissue profile.

Cephalostat:- As described by Broadbent (1931).
 Patient’s head is fixed by
2 ear rods that are
inserted into the ear holes
so that the upper border
of the ear holes rest on
the upper part of the ear
rods.
 Head is centered in the
cephalostat, is oriented
with the FHP parallel to
floor and MSP vertical
and parallel to the
cassette.

 Standardized FHP is
achieved by placing the
infraorbital pointer at the
patient’s orbit and then
adjusting the head until
the infra-orbital pointer
and ear rods are at the
same level.
 The upper part of face is
supported by forehead
clamp positioned at
nasion

The conventional use of 2 ear rods to stabilize the
head in radiographic Cephalometry is based on the
assumption that the transmeatal axis of human is
perpendicular to mid-sagittal plane.
A distance of 15cm from the midsagittal plane of the
cephalostat to the film cassette is often used.
 This fixed distance produces magnification that is
somewhat consistent. Exposure parameters in
cephalometric radiogra-phy are usually composed of
variable selections of kilovoltage (kVp), milliamperes
(mA), and exposure time. Affecting the choice of the
proper exposure settings are the patient's size and
age, the x-ray source-to-film distance, and the type of
film/screen combination used in film cassette.

 To penetrate the bony structures of the skull,
however, settings below 70 kVp should not be
used, if possible. Also, exposure times under 1
second are desirable to reduce possible blurring
caused by patient movement. This may be
accomplished by using the highest available
milliampere setting and/or high-speed
film/screen combinations.

Natural head posture (NHP)
 The concept of NHP in the living subjects
was introduced in Orthodontics in 1950s.
Broca, an anatomist described NHP as
the position of the head attained when an
individual stands with the visual axis in the
horizontal plane.
 The patient should be standing up and
should look into the reflection of his or her
own eyes in a mirror directly ahead in the
middle of the cephalostat (Sollow and
Tallgren in 1971).www.indiandentalacademy.com

 Natural head position is a standardized and
reproducible orientation of head in space when
one focusing on distant point at eye level.
 Focus film distance is usually 5 ft.
 Teeth are in C.O. and lips in response.
 Usually left side of the head faces the cassettes.
 For the PA projection (Caldweld projection).The
bilateral ear rods are rotated 90 degree relative
to their orientation during the lateral projection
procedure.
 A lead marker should be attached to one of the
upper corners of the cassette to indicate the
patient’s right or left side

Film Processing:-
 In general manual processing of the
cephalometric-radiographs at 68o
f
requires 5 minutes development cycle
followed by a 30-seconds rinse and a
10 minute fixation cycle. At least a 20
minute washing cycle is necessary after
that. If not rinse thoroughly the fixer
solution will continue to act on film after
processing and eventually tint or
discolour the image.
 Automatic processors commonly
produce a dry, processed film in about
4 to 6 min.

Quality of the Radiographs: Cephalometric
Image:-
 Image quality is a major factor influencing the
accuracy of cephalometric analysis. An
acceptable diagnostic radiograph is
considered in the light of 2 groups of
characteristics:
Visual characteristics
 Density
 Contrast
Geometric Characteristics
 Image unsharpness
 Image magnification
 Shape Distortion.

A. Density – is the degree of blackness of the
image. 2 main factors that control the
radiographic density are:
The exposure technique : Exposure factors
related to density are expressed as an
equation.
Density = Kvp x mA x S/D
The processing procedure : Density is directly
proportional to the temperature of the
developing solution and size of silver halide
crystals (larger grain size- high speed film)
B. Contrast - is the difference in densities
between adjacent areas. If the contrast is
high there will a short scale contrast and vice
versa. www.indiandentalacademy.com

Factors controlling the radiographs contrast
are:-
Tube Voltage: When the voltage is low,
contrast will be high but there will be short
scale contrast and vice versa.
Secondary or Scattered Radiation:
Decreases the contrast by producing film fog.
Subject Contrast: Nature and properties of the
subject i.e. thickness, density, and atomic
number.
Processing Procedure: - Increases
temperature –Increased contrast.

Geometric Characteristics
A.Image Unsharpness
 Geometric –due to penumbra (fuzzy outline)
 Motion
 Materials –Grain size –Intensifying screens
B.Image magnification : Enlargement of the actual size of
the object.
 Greater the object – film distance greater is the
magnification . At 90mm object to film distance with a 5 feet
anode-object distance enlargement is about 6% at a
distance of 130mm it will be 8.5%.
 It is also noted that in any single plane of the head that is at
right angle to the central rays, the enlargement is uniform
through out. Rotation of head could cause foreshortening of
the images of objects on one side and elongation of those
on the other side.

C. Shape Distortion: results in an image that does not
correspond proportionally to the subject.
 It occurs as results of improper orientation of the
patients head in the cephalostat or improper
alignment of the film and central rays.
 Usually the miliamperage setting does not
exceed 10mA the kilovoltage is about 60-90 KV,
exposure time not more than 3 seconds.
 An increases by 15 KV necessitates to decrease
the exposure time to half.
 Optimum temperature of developer and
developing time are 680
F and 5 minutes
respectively.

Protection from Radiation:-
 Protection measures that aim to minimize the
exposure to the patient include:-
1.Utilization of a high speed film (D,E) and
intensifying screen decreased dose of
radiation decreased exposure time.
2. Filtration of secondary radiation by an
aluminium filter.
3.Collimation by a diaphragm made of lead –
optimum beam size.
4.Proper exposure technique and processing –
to avoid repetition.

5.The patients wearing a lead apron in order
to absorb scattered radiation.
To avoid scattered radiation the operator
should stand at least 6 feet from the
patient, at an angle of 90 to 1350 to the
central ray of x- ray beam or should
preferably behind a Pb protective barrier.
5.The patients wearing a lead apron in order
to absorb scattered radiation.
To avoid scattered radiation the operator
should stand at least 6 feet from the
patient, at an angle of 90 to 1350 to the
central ray of x- ray beam or should
preferably behind a Pb protective barrier.

Conclusion
 Cephalometry is one of the important
diagnostic aids in orthodontics which help
in diagnosis & treatment planning. Despite
of its limitation of radiation exposure, it is a
non-invasive, & non-destructive technique
for the evaluation of final treatment
outcome.

Bibliography
 Athanasios E Athanasiou;Orthodontic Cephalometry;Mosby-Wolfe,1
1995:11-20,46-60,107-123.
 Alexander Jacobson; Radiography Cephalometry;Quintessence
Co,1995,26-33,39-62,165-173,175-184.
 Stuart c. white and Michael J. pharoah; oral radiology principles and
interpretation; Mosby 4th
edition, 6-9
 Ricketts RM, The biologic signifacance of the divine proportion &
fibonacci series. AJO 1982:81:351-370
 Ronald E Goldstein, Esthetics in Dentistry, 2nd
edition
vol.1,B.C.Decker 1998.

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