DEPARTMENT OF ORTHODONTICS

DENTAL COLLEGE

THIRUVANANTHAPURAM

POST GRADUTE PROGRAMME

SEMINAR ONSEMINAR ON

CEPHALOMETRICS : HISTORY, EVOLUTION CEPHALOMETRICS : HISTORY, EVOLUTION

AND AND

LANDMARKSLANDMARKS

Seeniya. C.K

INTRODUCTION

Ever since God created man in His image, man has been trying to change man

into his image. Attempts to change facial appearance are recounted throughout recorded

history. The question of what is a normal face, as that of what constitutes beauty, will

probably never be answered in a free society.

Orthodontists, in their attempts to change facio-oro-dental deviations from

accepted norms, have adopted cephalometric measurement, a method long employed in

physical anthropology. With the introduction of roentgenography, it was inevitable that

this procedure should be employed as a medium for the purpose of roentgenographic

cephalometrics.

Cephalometric radiography was introduced in to orthodontics during the 1930s.

Cephalometry had its beginnings in craniometry. Craniometry is defined in the

Edinburgh encyclopedia of 1813 as “the art of measuring skulls of animals so as to

discover their specific differences”. For many years anatomists and anthropologists were

confined to measuring craniofacial dimensions using the skull of long dead individuals.

Although precise measurements were possible Craniometry has the disadvantage for

growth studies.

Cephalometry is concerned with measuring the head inclusive of soft tissues, be

it living or dead. However this procedure had its limitations owing to the inaccuracies

that resulted from having to measure skulls through varying thickness of soft tissues.

With the discovery of X rays by Roentgen in 1895, radiographic Cephalometry

came in to being. It was defined as the measurement of head from bony and soft tissue

land marks on the radiographic image (Krogman & Sassouni 1957). This approach

combines the advantages of Craniometry and anthropometry. The disadvantage is that it

produces two dimensional image of a three dimensional structure.

HISTORY PRIOR TO THE ADVENT OF RADIGRAPHY

CLASSIFYING PHYSIQUES

History prior to the advent of radiography should begin with the mention of the attempts

of the scientists to classify the human physiques. In 500 BC, the Greek physician &

Father of medicine, Hippocrates, designated two physical types – habitus phithicus with a

long thin body subject to tuberculosis, & the habitus applecticus – a short thick individual

susceptible to vascular diseases & apoplexy. The search was continued by Aristotle (400

BC), Galen (200AD), & Rostan (1828), who was the first to include muscle mass as a

component of physique. Viola’s (1909) morphological index recognizes three

morphological types. Kretschmer (1921) adhered to the three Greek terms: the pyknic

(compact), asthenic (without strength), & athletic. Kretshmer also included dysplastic

physique which was taken up by Sheldon again in 1940.

The long historic thread extended into the twentieth century when Sheldon

introduced his method of somatotyping, based on three components of physiques, each

rated on a seven pt. scale& expressed as a three digit no. called as somatotype. It also

included a rating of dysplasia in the five regions of the body. “Dysplasia is literally bad

shape or form. In somatotyping it refers to disharmony or uneven distribution of a

component or components in diff. parts of the body,” acc. to Carter & Heath.

Morever their definition of a somatotype quantifies relative fatness or

endomorphy, relative musculoskeletal robustness, or mesomorphy,& relative linearity, or

ectomorphy. The somatotype then stands as a “quantitative overall appraisal of

bodyshape & composition, an anthropological identification tag & a useful descriptionof

human physique.” Heath & Carter also rigorously studied Sheldon’s instructions for

somatotyping & introduced modifications to method, designed to avoid some of the

limitation of Sheldon’s system.

Sheldon’s temperamental components, viscerotonia, somatotonia, & cerebrotonia,

convey behavioral traits commonly associated with physique. With a 7 pt. scale for each

somatotype component, there is a wide distribution in the dense midrange around the 4-4-

4 type ;a close relation between somatotype & temperament becomes tenuous.

Nonetheless common knowledge suffices to recognize dominant behavioral trait in many

instances, & that information can be revealing about the people in general. It may also

give some clues relating to the orthodontic treatment by providing an insight into the

character of the patients- their expectations concerning the treatment’s contribution to

their wellbeing, & even their understanding of & willingness to accept the discipline of

cooperation needed for successful conclusion of therapy.

MEASUREMENTS AND PROPORTIONS

Early history – The Canons

Portrayal of human form demands not only artistic talent & technical ability but a

disciplined & consistent style. To ensure these stipulations when images of royalty &

deity were commissioned & executed, the ancient Egyptians developed an intricate

quantitative system that defined the proportions of the human body. It became known as

the Canon. The theory of proportions acc. to Panofsky, is a

System of establishing the mathematical relations between the various members

of the living creature, in particular of the human being, in so far as these beings are

thought of as a subjects for artistic representation. The mathematical relation can be

expressed by the division of a whole as well as by the multiplication of the unit ; the

effort to determine them could be guided by the desire for beauty as well as interest in the

norms, or finally by the need for establishing a convention ; and above all, the

proportions can be investigated with reference to the object of representations well as

with reference to the representation of the object.

The proportions of the human body were determined with an ell measuring ruler,

established in 3000BC. Its length corresponded to the distance from the elbow to the

outstretched thumb.

Initially the canons were enclosed in a grid system of equalized squares with 18

horizontal lines line 18 drawn through hairline. Later it was included in a grid system of

22 horizontal lines, line 21 drawn through the upper eyelid.

After the outline of the human figure was drafted on papyrus leaves the

iconographic norms or canon, served to insert the figure into a network of equal squares.

The image could be transferred to any required size by first drawing a coordinate system

to proper size ; into this system the image can then be drawn readily & accurately for

display in a tomb or on a wall. This procedure is still universally used to enlarge or

reduce any kind of illustration (MISE AU CARREAU).

The classical art of Greeks rejected the rigid Egyptian system for creating human

images. The Greeks needed the freedom to account for the shifting dimension of organic

movement, and the foreshortening of the upper part of a stature relative to the lower part.

Indian iconometry studied extensively by the Ruelius, was transmitted through

Sanskrit literature & extensively reviewed in Indian texts of architecture. The

proportional canons of that system were already detailed in older sources & did not

materially change with time. Face height was used as the module of both the sariputra &

alekhyalakshana proportional system, which closely reflected the natural relation of the

parts of the body to each other. The sariputra system , dated 1200 AD is known for the

sculptures honoring the God Buddha.

In the Byzantine empire, the rectangular grid of the canon was replaced by a

scheme of three concentric circles with nose length as the radius of drawing the two

successive circles.

RENAISSANCE TO THE TWENTIETH CENTURY

Fifteenth century saw the advent of specific measurements being made to

compare the features of different skulls and head. Leonardo da vinci (1452-1519 AD)

was probably one of the earliest people of note to apply the theory of head measurement

to good effect in practice.

He used a variety of lines related to specific structures in the head to assist in his

study of the human form (Fig-1). His drawings included a study of facial proportions in

natural head position. According to the notes the profile was divided in to seven parts by

eight horizontal lines. Sub division is made with vertical lines. In his study of horse &

horse men he used a scheme of facial measurement with in a grid system with five

horizontal and six vertical lines and the subject in natural head position (Fig-2). The

joining of the lower lip and chin and the tip of the jaw and the upper tip of the ear with

the temple forms a perfect square; and each face is half a head.

Albrecht Durer (1471-1528 AC) was a brilliant, unusually productive and

exuberant artist of great virtuosity. He published a treatise in 1528 on cranial

measurements which comprised “Vier Bucher von menschlischer Proportion” dealing

with the proper proportion of human form in the first two books, the proportions

according to mathematical rules in third book, the human figure in motion in the fourth

book. Durer’s four books mark a climax which the theory of proportions had never

reached before or was to reach ever after.

Using strictly geometrical methods he provided a proportionate analysis of the

leptoprosopic (long ) face and euryprosopic (broad) face in coordinate system, where the

horizontal and the vertical lines were drawn through the same land marks or facial

features (Fig-3). His drawings attest to continuous efforts to define variations in the facial

morphology. One of this is significant as the key to cephalometric analysis. In (Fig-4) the

difference between the retroclined and the proclined facial profile is shown by a change

of angle between the vertical and the horizontal axes of a rectangular coordinate system

to characterize the facial configuration of each subject.

The sixteenth century saw the first truly scientific attempt at cranial measurement

& the introduction by Spigel (1578-1625AC) of the “lineae cephalometricae”. Spigel’s

linear cephalometricae consisted of four lines: the facial, occipital, frontal, & sincipital

lines. He described these lines as follows:

Facial: from the most inferior point of the chin to the most

superior point on the forehead.

Occipital: from the crown of the head to the atlas.

Frontal: from one temple to the other.

Sincipital: from the lowest part of the ear, in the region of the

mastoid process, to the highest part of the sinciput, sinciput being

the anterior part of the head or skull from forehead to the crown.

According to him in a well proportioned skull, these lines should all be equal to

one another. In reporting this Aitken-Meiges writes “although these lines are evidently

not sufficient for the comparative ethnography, in ascending zoological scale, these lines

approximate just in proportion as the head measured approaches the human form. To

Spigel a skull was either well proportioned or it was not.

In 1699, a Cambridge physician, Edward Tyson (1650-1708 AD) under took

some measurements on the chimpanzee skull & proposed that there was an intermediate

animal between man and monkey. He described this animal as a form of ‘pigmy’ but this

pigmy was later shown to be another chimpanzee there by negating his findings.

In the eighteenth century most of the workers in the field of craniometry were

interested in relating intelligence to certain measurements. They not infrequently found

that their native race demonstrated a higher level of intelligence, according to their

measures than did others.

The Dutchman Pieter Camper (1722- 1789 AD) was credited with the

introduction of facial angle & for famous publication “Dissertation sur les varietes

naturelles de la physionomie” which appeared posthumously in 1791. 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 facial angle as he described it was formed by the intersection of a facial line

and a horizontal plane (Fig-5). The facial line was a line tangential to the most prominent

part of the frontal bone and to the slight convexity anterior to the upper teeth. The

horizontal plane passes through the lower part of the nasal aperture, backwards along the

line of the zygomatic arch, and through the centre of the external auditory meatus.

Camper’s facial angle was readily accepted as a standard measurement in

craniology. The terms prognathic and orthognathic introduced by Retzius 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 the facial type. The term prognathism refers to the prominence of

the face, or jaws, relative to the fore head, 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 tailed simian, an orangutan, a young native African, and a

Kalmuck. Age changes in human physiognomy are also described by him. Frontal views

were also studied by Camper in a young orangutan, Kalmuck, native African, and the

face of Apollo Pythius. The most interesting proportional difference was the long face

height of native African.

The drawbacks of Camper’s facial angle were:

It ignores the contribution made by he lower jaw to facial forms.

He did not adhere strictly to his location of posterior reference point for the

horizontal plane.

The direct comparison of skull of different ages was not possible because the

locating point might alter is position relevant to other bony structures with

advancing age.

Shortly after this Deschamps (1740- 1824 AC) introduced the cephalic triangle

made up of facial, occipital, & coronal angles. The facial angle was the lesser angle

formed by the intersection of a horizontal line that passed from the external auditory

meatus to the base of the nose, which crossed a profile line. This is similar to Camper’s

facial angle. Fortunately the use of external auditory meatus as a reference point enabled

a rough comparison to be made between different skulls.

The desire to learn how men differ from each other and from animals and why,

motivated several other craniologists like Doornick, Spix, Oken and many others to put

forward their individual methods of analyzing human and animal skulls.

In the same period as Camper, there was a French man; Daubenton (1716-1799

AC) was very concerned with the relative position of the foramen magnum in man and

lower animals. He made use of new angles, including the occipital angle to make

measurements. Although his measurements were not very reliable, a similar angle was

later used by another craniologist, Pierre Broca.

Daubentons occipital angle is formed by 2 lines (Fig-6): the first line passes

along the level of opening of the foramen magnum, from the inial edge of the foramen

along the surface of the occipital condyles & anteriorily for short distance. The second

line passes from the posterior margin of the foramen magnum to the tip of the nasal

spine. Broca’s occipital angle was formed by two different lines giving alternative angles,

originating from the posterior and anterior margins of the foramen magnum& passing

anteriorly through the junction of frontal and nasal bones (Fig-7). The magnitude of

occipital angle decreases as the habitual posture of the animal tends more towards

upright.

Daubenton’s interest in the position of the foramen magnum was shared by Sir

Charles Bell (1744 -1842 AC). According to him, since the head is movable on a pivot

joint, it must always be balanced. Therefore the Negro skull being heavier in front & thus

falling forward naturally is thrown backward to poise it and relieve the muscles which

support it behind.

This hypothesis was tested by a medical student, William Gibson (1788-1868

AC) in 1809 by placing in front of him Negroid &European skulls resting on their

occipital condyles. Contrary to expectation the European head fell forward and the

Negroid skull fell backward. Earlier Samuel Soemmering (1758-1826) had noted the

same point in 1785.

An antagonist of Camper, Johann Friedrich Blumenbach (1752- 1840 AC)

rejected the method of lines & angles as a test of national characteristics & proposed a

minute survey of the skull particularly the frontal and maxillary bones. In 1795 he

described a method of positioning the cranium to be measured in a standard reproducible

manner. His method was simple consisting of resting the skull on its base and looking

down vertically up on its vault. The points to be noted were the projection of the maxillae

anterior to the frontal arch, the directions of the jaws & cheek bones (outward, forward,

etc) & the proportional breadth or narrowness of the head. He completely rejected the

idea of viewing the skull in Norma lateralis.

Anders Retzius (1796-1860 AC) correlated the two schemes, i.e., of Camper and

Blumenbach, thereby providing a basis for the methods of craniology used today. He is

also credited with the introduction of cephalic index, the ratio of breadth to length of the

skull expressed as a percentage.

John Barclay (1758-1826 AC) proposed two new angles, the superior and the

inferior basifacial angles& for the first time, incorporated the mandible in to his

measurements. These angles were formed by the intersection of the basifacial lines with a

profile line. The superior basifacial line was drawn along the basilar surface of the

superior maxillary bone & the inferior basifacial line was drawn along the base of the

lower jaw. The superior basifacial angle was not dissimilar to Camper’s facial angle &

was measured by a custom made goniometer (supplied by Dr Leach.).

The nineteenth century produced three great men in the history of craniology:

Huxley, Broca& Topinard.

Thomas Huxley (1825-1895 AC) wrote in 1876 “the so called facial angle, in the

fact, does not simply express the development of the jaws in relation to the face, but is

the product of two factors, a facial& a cranial, which vary independently. The face

remaining the same, prognathism may be indefinitely increased, or diminished, by

rotation of the frontal region of the skull, backwards or forwards, upon the anterior end of

the basicranial axes”. He also introduced two new angles, the spheno maxillary and

spheno ethmoidal angles. He preferred the spheno maxillary angle to Camper’s angle

when comparing the degree of prognathism in different skulls. This angle is formed by

the two lines drawn from basion and prosthion to prosphenion. The other angle, spheno

ethmoidal tends to be less than 180° in man.

Broca (1824-1880 AC) who is the founder of the Paris Society of Anthropology

believed that the great variability of the cranial form constituted a principal difficulty for

the craniologist. He was the first craniologist to institute a precise and accurate technique

which could be used to compare crania so that it was made possible to discriminate

between the variations in racial types among human skulls. He introduced a base line

“plan alveolo- condylien” which passes through the alveolar point & tangential to the

inferior surfaces of the two occipital condyles. He also developed a craniostat, mainly

constructed of wood for positioning the skull (Fig-8).

It was generally accepted at this time that the angles were best determined on

projected drawings of the skull. Broca devised a simple method to trace the out line of the

skull on to a piece of paper by fixing the skull in the craniostat& positioning a drawing

board with paper attached to it parallel to the mid sagittal plane& a pencil held in a frame

perpendicular to the paper. The resultant tracing was equivalent to a tracing of the

peripheral as depicted on a lateral skull radiograph.

Paul Topinard (1830- 1912 AC) used a similar criniostat with some additional

modifications (Fig-9). Topinard wrote in 1890 “the craniometer substitutes the

mathematical data for the uncertain data founded on judgment and opinion. Moreover it

studies the skeleton of the ensemble, the cranium and the face separately and each of the

plates as well.

During nineteenth century the need for standardization of methods used in

craniometry became an important issue, and since then many bodies have met to better

define those points and planes in use. The most important meeting as far as the dental

profession is concerned was held in Frankfurt-am-Maine in August 1882. This was the

13th General Congress of the German Anthropological Society and it is to this

Congress that the Frankfurt Horizontal Plane owes its name.

J.G.Garson (19th century) translated the agreement and published it in the

Journal of Anthropological Institute 1885

Earlier in 1859 a horizontal plane following the zygomatic arches was suggested

by a Russian craniologist, Von Baer. Later the plane was defined more precisely as line

drawn from the centre of each auditory meatus to the lower point on the inferior margin

of each orbit by Von Ihering (1850-1930). The Frankfurt agreement modified Von

Ihesing’s definition so that the plane passes through the upper border of the bony meatus

vertically above their centres. However the reproducibility of this plane on an intact skull

is less than Broca’s condyloalveolar plane. Subsequent to the agreement the definition of

the horizontal plane has been altered so that it is now taken as passing through the right

and left porion &left orbitale. Thereby reducing the problems incurred by asymmetrical

skulls.

Following the Frankfurt Agreement very little change of note has occurred in the

definition of points and planes. In 1914 Rudolph Martin (1864-1925) published the

“Lehrbuch der Anthropologie in Systematischer Darstellung mit besonderer

Berucksichtigung der anthropologischen Methodoen” & this is still renowned as a fine

reference book on physical anthropology.

CEPHALOMETRIC RADIOGRAPHY

In 1895, Professor William Conrad Roentgen made a remarkable contribution

to the field of science with the discovery of x-rays. On December 28 1895 he submitted a

paper “On A New Kind of Rays, A Preliminary Communication” to the Wurzburg

Physical Medical Society for publication in its journal.

Prof. Wilhem Koening & Dr. Otto Walkhoff simultaneously made the first

dental radiograph in 1896.

It was clear that the use of x-rays provided the means of obtaining a different

perspective on the arrangement and relation of bones thus expanding the horizons of

craniometry& cephalometry. The evolution of cephalometry in the twentieth century is

universally linked to Edward angle’s publication of his classification of malocclusion.

But the dogmatic inferences of the new school were criticized for failing to include

differential diagnosis of facial profile in patients with class iii& class ii malocclusion.

Van Loon was probability the first to introduce cepalometrics to orthodontics

when he applied anthropometric procedures in analyzing facial growth by making plaster

casts of face in to which he inserted oriented casts of the dentition. Hellman used

cephalometric techniques and described their value beginning with 1920s.

The first x- ray pictures of skull in the standard lateral view were taken by

A.J.Pacini & Carrera in 1922.Pacini received a research award from the American

Roentgen Ray Society for a thesis entitled “Roentgen Ray Anthropometry of the

Skull”. Pacini introduced a teleroentgenographic technique for standardized lateral head

radiography and thereby opened, what proved to become a tremendous advance in

cephalometry, as well as in measuring the growth and development of face. His method,

which was rather primitive, involved a large fixed distance from the x ray source to the

cassette. The head of the subject, placed adjacent to a standard holding the cassette, was

immobilized with a gauze bandage wrapped around both the face and the cassette after

the patient’s midsagittal plane was carefully oriented parallel to the cassette.

He identified the following anthropometric landmarks on the roentgenogram:

gonion, pogonion, nasion, and anterior nasal spine. He also located the centre of the sella

turcica and the external auditory meatus.he measured the gonion angle and the degree of

maxillary protrusion.

Atkinson in 1922 advocated the use of roentgenograms in locating the ‘key ridge’

and the soft tissue relations to the face and the jaws.

In 1923 Mc Cowen reported on profile roentgenograms that he used for

orthodontic purposes to visualize the relationship between the hard and soft tissues and to

note changes in profile which occur during treatment.

Simpson presented a method for obtaining profile roentgenograms in 1923 before

the American society of orthodontists.

In 1927 Ralph Waldron of Newark, N.J. made mention of measuring the gonion

angle from a roentgenogram taken at 90 to the facial profile. Waldron was the first to

construct a cephalometer, which differed little from those used today.

In 1928 Dewey and Riesner published an article, “A Radiographic Study of

Facial Deformity”. Dewey and Riesner immobilized the patients head in a head clamp

and placed the cassette against the patient’s face. They took profile roentgenograms by

aligning the eye- ear plane by a right angle leveling technique. They used a target

distance of three feet.

In 1931 the methodology of cephalometric radiography came to full function

when B. Holly Broadbent in USA and H. Hofrath in Germany simultaneously

published methods to obtain standardized head radiographs in the Angle Orthodontist (A

new X ray technique and its application to orthodontia) and in Fortschritte der

Orthodontie (Bedeutung der Rontgen fern und Abstands Aufnahme fur die

Diagnostik der kieferanomalien), respectively.

This development enabled orthodontists to capture the field of cephalometry from

the anatomists and anthropologists who had monopolized craniometric studies,

particularly in nineteenth century.

HOLLY B BROADBENT’S CONTRIBUTION

Broadbent’s interest in craniofacial growth began with his orthodontic education

under E.H. Angle in 1920. He continued to pursue that interest along with his orthodontic

practice, working with a leading anatomist J. Wingate Todd

The idea of diagnosing dental deformities by means of planes and angles was first

proposed in 1922 by Paul Simon of Germany in his book, “Fundamental Principles of

a Systematic Diagnosis of Dental Anomalies”. Although his “Law of the Canines”

was later disproved by Broadbent, his theories stimulated the latter to apply the principles

of craniometry to living subjects.

The uncertainty of locating land marks in the skull of the living child by

approaching through skin and soft tissues led hi to search for a means of recording

craniometric landmarks on the living child as accurately as done with a craniostat in

measuring the dead skull.

During 1920’s Broadbent refined the craniostat in to craniometer by the addition

of metric scales. That proved to be the first step in the evolution of craniostat in to a

radiographic cephalostat. It did not take him much longer to convert the direct measuring

instrument in to a radiographic craniometer.

Meanwhile the course of Broadbent’s orthodontic practice he corrected the

malocclusion of Charles Bingham Bolton, son of Chester and Francis P Bolton. His

discussions of facial growth with Congress woman Bolton led to the addition of Bolton

study of facial growth to the long list of Bolton philanthropies. As Charles grew to adult

hood this study became a major personal as well as financial commitment.

Cephalometrics was neither developed as a technique looking for an

application nor was it developed as a diagnostic tool. Broadbent’s single goal was the

study of craniofacial growth. The Broadbent technique for cephalometric radiography

was one of the tools that he developed for the implementation of that study.

The technique and apparatus perfected for the Bolton Fund study of the normal

developmental growth of the face, eliminated practically all of the technical difficulties

encountered in previous methods of recording dento-facial changes, and proved to be a

convenient as well as scientific method of measuring orthodontic procedures.

According to Broadbent the patient’s head was centered in the cephalostat with

the superior borders of the external auditory meatus resting on the upper parts the two ear

rods. The lowest point on the inferior bony border of the left orbit, indicated by the

orbital marker, was at the level of the upper parts of the ear rods. The nose clamp was

fixed at the root of the nose to support the upper part of the face. The focus film distance

was set a t 5 feet (152.4 cm) and the subject film distance could be measured to calculate

image magnification. With the two X ray tubes at right angles to each other in the same

horizontal plane, two images (lateral & postero anterior) could be simultaneously

produced. (A new x-ray technique and its application to orthodontia, By B. Holly

Broadbent D.D.S., Angle Orthodontist, April, 1931)

While Germany’s Hofrath’s technique differed from Broadbent’s in that the path

of the central ray was not fixed in relation to the head and no plan was suggested for

super positioning subsequent x-rays.

OTHER IMPORTANT CONTRIBUTIONS MADE BY BROADBENT.

In 1937, using serial records of twins; he showed how growth – or its lack – was

the greatest limiting factor in clinical success. In 1943 he stipulated that eruption of the

third molars had no ill effect on the denture, particularly the lower incisors.

In 1938, a group under Allan G. Brodie at the University of Illinois presented

material based on a cephalometric appraisal of orthodontic results:

1) The use of elastics causes a disturbance in the Bolton plane-occlusal plane angle;

2) Axial inclinations of orthodontically-moved teeth tend to return to their original

inclinations;

3) Bone changes during treatment are restricted to the alveolar process.

Brodie, in a landmark study (1941) used for his PhD in anatomy, corroborated

Broadbent’s contention that the growth pattern of the normal child’s face

develops in an orderly fashion downward and forward and that the pattern, once

attained at an early age, did not change.

Thompson and Brodie (1942) in a report on the rest position of the mandible,

concluded that:

1) The morphogenetic pattern of the head was established at a very early age and did

not change;

2) The presence or absence of teeth has little, if any, bearing on the form or the rest

position of the mandible; and

3) Vertical facial proportions are constant throughout life.

Margolis (1943) wrote on the relationship between the inclination of the lower

incisor and the incisor-mandibular plane angle and was the first to corroborate

Tweed’s clinical observation that, in normal occlusions, the lower incisors are 90°

to the mandibular basal bone.

In 1947, Wylie produced a method of assessing anteroposterior dysplasias, and,

that same year, Margolis contributed his maxillo-facial triangle.

(Lewis, A.B.: The impact of cephalometry on orthodontic concepts. Angle Orthodontist,

1950)

CEPHALOMETRIC ANALYSIS

The major use of radiographic cephalometry is in characterizing the patient’s

dental and skeletal relationships. This led to the development of a number of

cephalometric analyses to compare a patient to his or her peers, using population

standards. William. B. Downs in 1948 developed the first cephalometric analysis. Its

significance was that it presented an objective method of portraying many factors

underlying malocclusion and there could be a variety of causes of malocclusion exclusive

to teeth. This was followed by other analyses by Cecil. C. Steiner (1953), C.H.Tweed

(1953) , R.M. Ricketts (1958), V.Sassouni (1969), H.D. Enlow (1969), J.R.

Jaraback(1970), & Alex Jacobson (1975) etc.

EVOLUTION OF CEPHALOMETRICS

The thoroughness of Broadbent’s approach to the design of the cephalometric

method is evident from the fact that the basic technique has survived almost unchanged

for over seventy years.

In about two decades times the instrumentation had evolved to a form more

suitable for the individual practitioner through the pioneering efforts of Margolis, Higley

& others.

PATIENT ORIENTATION:

The ears were established as the basis for orientation& fixation in the beam axis.

Frankfurt plane was adopted for horizontal orientation with nasion for stabilization. The

FH plane was chosen because this was approximate the natural head position (NHP). But

the FHP also had its drawbacks & these were:

1. Some individuals show a variation of their FH plane to the true horizontal to an

extent of ± 10°.

2. The landmarks to locate the FH plane, orbitale& porion, especially the latter are

difficult to identify on a cephalogram.

An alternative to overcome this problem was to use a functionally derived NHP.

According to Morrees &Kean, it was obtained by asking the subject to look at the image

of their eyes in the mirror located at eye level. A frame of reference was originally

intended as a reliable procedure for orienting facial profiles so that same orientation

could be established on different occasion by different investigators. Although the

functionally derived NHP was more accurate its reproducibility was less than FHP

(anatomic approximation of NHP). Lateral and posterio- anterior views perpendicular to

each other in the horizontal plane were specified for three dimensional analyses.

Bjork’s studies of facial prognathism illustrated the unreliability of intra cranial

reference lines in cephalograms (Some biological aspects of prognathism and occlusion

of teeth, Angle Orthodontist, 1951)

Kroagman and Sassouni (1957) conducted an exhaustive survey of

roentgenographic cephalometry in which the FH Plane coincided with the physiologic or

true horizontal.

Sassouni made an attempt to standardize the orientation of cephalograms by

means of an optical plane advocated in 1862 by Broca, who stated that “when a man is

standing and when his visual axis is horizontal, he(his head) is I natural position.”

X-RAY SOURCE POSITION

The x-ray source is positioned 5 feet (152.4) from the subject’s midsagittal plane.

A change to 150 cm has been adopted by some as a conveniently round metric number,

but the difference is negligible. A major improvement in lateral cephalostats is the

capability of taking lateral& postero-antrior views with a single x-ray source instead of

two.

FILM POSITION & ENLARGEMENT

The other significant change from the original technique is adjustability of film

position. The original cephalostat was based on the design of the anthropometric

craniometer &cassettes were attached to these mechanisms. The disadvantage of this very

efficient mechanical design is that it makes cassette position and resultant enlargement

depended on head size. Evaluation of serial changes by direct superimposition is made

unreliable by this variable enlargement.

The relative immunity of angular measurements to enlargement distortions led

many researchers to opt for angular over linear values whenever possible. Also newer

instruments have been developed that can over come this drawback of variable

enlargement by providing independent adjustments for head holding mechanisms and

cassette.

POSTERO-ANTERIOR (FRONTAL) CEPHALOMETRY

Since the introduction of a standardized method for obtaining skull radiographs,

cephalometrics has become one of the major diagnostic tools in orthodontics. The

posterior anterior cephalogram contains diagnostic information not readily available from

other sources. This information allows the practitioner to evaluate the width and

angulation of the dental arches in relation to their osseous bases in the transverse plane;

evaluate the width and transverse positions of the maxilla and mandible; evaluate the

relative vertical dimensions of bilateral osseous and dental structures; assess nasal cavity

width; and analyze vertical and/or transverse facial asymmetries.

Malocclusions &dentofacial deformities constitute three dimensional conditions

or pathologies. Although all orthodontic patients deserve an equally comprehensive three

dimensional diagnostic examinations, assessment of postero- anterior cephalometric

views are of particular importance in cases of:

1. Dento alveolar & facial asymmetries

2. Dental & skeletal cross bites.

3. Functional mandibular displacements

The same equipment that is used for the lateral cephalometric projections is

utilized. The initial unit described by Broadbent consisted of a set up in which two X ray

sources with two cassettes were simultaneously used, so that lateral and frontal

cephalograms were taken at the same time. Although precise three dimensional

evaluations are possible using this technique, it has now been almost abandoned since it

requires rather large equipment with two x ray sources.

Modern equipment uses one x-ray source. Therefore following lateral

cephalometric registration, the patient must be repositioned if a postero anterior

cephalogram has to be produced. A head holder or cephalostat that can be rotated 90° is

used, so that the central X ray beam penetrates the skull of the patient in a postero

anterior direction and bisects the transmeatal axis perpendicularly. Maintaining the

identical horizontal orientation from lateral to the postero- anterior projection is critical

when comparative measurements are made on each other. (Moyers et al, 1988)

In using natural head position for postero anterior cephalometric registrations,

some practical problems are encountered. The patient’s head is facing the cassette; which

makes it difficult for the patient to look in to a mirror to register natural head position

(Solow &Tallgren, (1977). Furthermore, space problems make it impossible to place a

nose piece in front of nasion to establish support in a vertical plane.

For better evaluation of patients with craniofacial anomalies that require special

attention to the upper face, the patient head should be positioned with the tip of the nose

and forehead lightly touching the cassette holder. (Chierci, 1981)

In cases of suspected significant mandibular displacement, the PA cephalogram

should be taken with the mouth of the patient slightly open in order to differentiate

between functional mandibular displacements & dentoskeletal facial asymmetry (Faber,

1985). As far as exposure conditions and considerations are considered, more exposure is

needed for PAcephalograms than lateral views (Enlow, 1982)

CEPHALOMETRIC LAND MARKS

Cephalometric landmarks are readily recognizable points on a cephalometric

radiograph or tracing, representing certain hard or soft tissue anatomical structures

(anatomical landmarks) or intersections of lines (constructed landmarks).landmarks

are used as reference points for the construction of various cephalometric lines or planes

and for subsequent numerical determination of cephalometric measurement.

Measure points and land marks used in anthropometrics were formulated at a

series of international congress on “Prehistoric Anthropology and Archeology.” three

of the more important ones were held at Frankfort (1882), Monaco (1906), and Geneva

(1912). The agreements reached at Monaco and Geneva state that “A land mark in

anthropometry is as near as possible a definite point from or to which to measure.”

Landmarks show a fairly definite range of normal variation or oscillation about

mean. It is important for the orthodontist to determine whether facial dimensions and

relationship of facial components fall with in the range of normal variation or whether the

deviations are to be classified as abnormalities.

REQUIREMENTS OF LANDMARKS AND MEASURE POINTS

1. Landmarks should be easily seen on the roentgenogram, be uniform in out line,

and easily reproducible.

2. Lines and planes should have significant relationship to the vectors of growth of

specific Ares.

3. Landmarks should permit valid quantitative measurements of lines and angles

projected from them.

4. Measure points and measurements should have significant relation to the

information sought.

5. Measurements should be amenable to statistical analyses but should preferably

not require extensive specialized training, in statistical methods.

Garn (1961) pointed out that there are no ‘fixed points’ in the skull of living

person. Variability of the landmarks depends on age, sex, maturation rate, ethnic

background, and other factors.

Following is a list of the most commonly used cephalometric landmarks. In these

definitions, the following convention is used: midsagittal identifies landmarks lying on

the midsagittal plane, unilateral identifies land marks corresponding to unilateral

structures and bilateral applies to landmarks corresponding to bilateral structures.

LATERAL CEPHALOGRAM

HARD TISSUE LANDMARKS

A-point (Point A, Subspinale, ss) : the deepest point (most posterior) midline

point on the curvature between the ANS and prosthioin

Anterior nasal spine (ANS): the tip of the bony anterior nasal spine at the

inferior margin of the piriform aperture in the midsagittal plane.

Articulare (Ar) : a constructed point representing the intersection of three

radiographic images: the inferior surface of the cranial base and the posterior out

line of the ascending rami or mandibular condyles

B-point (Point B, Supramentale, sm): the deepest (most posterior) midline point

on the bony curvature of the anterior mandible, between infradenale and

pogonion.

Basion (Ba): the most anterior inferior point on the margin of the foramen

magnum in the midsagittal plane.

Bolton (Bo) : the highest points on the outlines of the retrocondylar fossae on the

occipital bone, approximating the centre of the foramen magnum

Condylion (Co) : the most superior point on the head of the mandibular condyle

Glabella (G): the most prominent point of the anterior contour of the frontal bone

in the midsagittal plane.

Gnathion (Gn) : the most anterior inferior point on the bony chin in the

midsagittal plane

Gonion (Go): the most posterior inferior point on the outline of the angle of the

mandible.

Incision inferius (Ii) : the incisal tip of the most labially placed mandibular

incisor

Incision superius (Is) : the incisal tip of the most labially placed maxillary

central incisor

Infradentale (Id, Inferior prosthion) : the most superior anterior point on the

mandibular alveolar process between the central incisors

Menton (Me): the most inferior point of the mandibular symphysis in the

midsagittal plane.

Nasion (N,Na) : the intersection of the internasal and frontonasal sutures in the

midsagittal plane

Opisthion (Op) : the most posterior inferior point on the margin of the foramen

magnum in the midsagittal plane

Orbitale (Or) : the lowest point on the inferior orbital margin

Pogonion (pog, P, Pg) : the most anterior point on the contour of the bony chin in

the midsagittal plane

Porion (Po): the most superior point of the outline of the external auditory

meatus (anatomic porion). When the anatomic porion cannot be located readily

the superior most point of the image of the ear rods (machine porion) sometimes

is used instead.

Posterior nasal spine (PNS) : the most posterior point on the bony hard palate in

the midsagittal plane, the meeting point between the inferior and the superior

surfaces of the bony hard palate at its posterior aspect

Prosthion (Pr, Superior prosthion, Supradentale): the most inferior anterior

point on the maxillary alveolar process between the central incisors.

Pterygomaxillary fissure (PTM, Pterygomaxillare): a bilateral inverted tear

drop shaped radiolucency whose anterior border represents the posterior surfaces

of the tuberosities of the maxilla. The landmark is taken at the most inferior point

of the fissure, where the anterior and the posterior outline of the inverted teardrop

merge with each other.

R- Point (Registration point): a cephalometric reference point for registration of

superimposed tracings.

Sella (S): the geometric centre of the pituitary fossa (sella turcica), determined by

inspection – a constructed point in the midsagittal plane.

SOFT TISSUE LANDMARKS

Cervical point (C): the innermost point between the submental area and the neck

in the midsagittal plane. Located at the intersection of lines drawn tangent to the

neck and submental areas.

Inferior labial sulcus (Ils): the point of the greatest concavity on the contour of

the lower lip between the labrale inferius and menton in the midsagittal plane.

Labrale inferior (Li): the point denoting the vermillion border of the lower lip in

the midsagittal plane.

Labrale superior (Ls): the point denoting the vermillion border of the upper lip

in the midsagittal plane.

Pronasale (Pn): the most prominent point of the tip of the nose, in the midsagittal

plane.

Soft tissue glabella (G’): the most prominent point of soft tissue drape of the fore

head in the midsagittal plane.

Soft tissue menton (Me’): the most inferior point of the soft tissue chin in the

midsagittal plane.

Soft tissue nasion (N’, Na’): the deepest point of the concavity between the

forehead and the soft tissue contour of the nose in the midsagittal plane.

Soft tissue pogonion (Pg’, Pog’): the most prominent point on the soft tissue

contour of the chin in the midsagittal plane.

Stomion (St): the most anterior point of contact between the upper and lower lip

in the midsagittal plane. When the lips are apart at rest, a superior and an inferior

stomion point can be distinguished.

Stomion inferius (Sti): the highest midline point of the lower lip.

Stomin superius (Sts) : the lowest midline point of the upper lip

Subnasale (Sn): the point in the midsagittal plane where the base of the

columella of the nose meets the upper lip.

Superior labial sulcus (Sls): the point of greatest concavity on the contour of the

upper lip between subnasale and labrale superius in the midsagittal plane.

Trichion (Tr): an anthropometric landmark, defined as the demarcation point of

the hair line in the midline of the forehead.

POSTERO- ANTEROIR CEPHALOGRAMS

A. BILATERAL SKELETAL LANDMARKS

Greater Wing Superior Orbit (GWSO) - the intersection of the superior border

of the greater wing of the sphenoid bone and lateral orbital margin.

Greater Wing Inferior Orbit (GWI0) - the intersection of the inferior border of

the greater wing of the sphenoid bone and the lateral orbital margin.

Lesser Wing Orbit (LWO) - the intersection of the superior border of the lesser

wing of the sphenoid bone and medial aspect of the orbital margin.

Orbitale (O) - the midpoint of the inferior orbital margin.

Lateral Orbit (LO) - the midpoint of the lateral orbital margin.

Medial Orbit (MO) - the midpoint of the medial orbital margin.

Superior Orbit (SO) - the midpoint of the superior orbital margin.

Zygomatic Frontal (ZF) - the intersection of the zygomaticofrontal suture and

the lateral orbital margin.

Zygomatic (Z) - the most lateral aspect of the zygomatic arch.

Foramen Rotundum (FR) - the center of foramen rotundum.

Condyle Superior (CS) - the most superior aspect of the condyle.

Center Condyle (CC) - the center of the condylar head of the condyle.

Mastoid Process (MP) - the most inferior point on the mastoid process.

Malar (M) - the deepest point on the curvature of the malar process of the

maxilla.

Nasal Cavity (NC) - the most lateral point on the nasal cavity.

Mandible/Occiput (MBO) - the intersection of the mandibular ramus and the

base of the occiput.

Gonion (G) - the midpoint on the curvature at the angle of the mandible (gonion).

Antegonial (AG) - the deepest point on the curvature of the antegonial notch.

B. MIDLINE SKELETAL LANDMARKS

Crista Galli (CG) - the geometric center of the crista galli.

Sella Turcica (ST) - the most inferior point on the floor of sella turcica.

Nasal Septum (NSM) - the approximated midpoint on the nasal septum between

crista galli and the anterior nasal spine.

Anterior Nasal Spine (ANS) - the center of the intersection of the nasal septum

and the palate.

Incisor Point (IPU) - the crest of the alveolus between the maxillary central

incisors.

Incisor Point (IPL) - the crest of the alveolus between the mandibular central

incisors.

Genial Tubercles (GT) - the center of the genial tubercles of the mandible.

Menton (ME) - the midpoint on the inferior border of the mental protuberance.

C. BILATERAL DENTAL LANDMARKS

Maxillary Cuspid (MX3) - the incisal tip of the maxillary cuspid.

Maxillary Molar (MX6) - the midpoint on the buccal surface of the maxillary

first molar.

Mandibular Cuspid (MD3) - the incisal tip of the mandibular cuspid.

Mandibular Molar (MD6) - the midpoint on the buccal surface of the

mandibular first molar.

IDENTIFICATION AND REPRODUCIBILITY OF CEPHALOMETRIC

LANDMARKS:

It is essential to evaluate the validity of information obtained from the lateral head

film. Cephalometric measurements on radiographic images are subject to errors that may

be caused by radiographic projection errors with in the measuring system & errors in

landmark identification.

Landmark identification errors are considered as the major source of

cephalometric error. Many factors are involved uncertainty. They are:

Density & sharpness of the image

Anatomic complexity & superimposition of hard and soft tissues

Observer’s experience in locating a landmark and defining the location of the

landmark.

A Meta analysis was carried out by B. Tipkova, P. Major, N. Prasad&B. Hebbe in

1997 AJO

To determine the reproducibility of some commonly used 15 landmarks. Meta

analysis is a quantitative review technique described as the statistical analysis of a large

collection of results from individual studies for the purpose of integrated finding.

The 15 landmarks were N, S,Or, Ba, P, ANS, PNA, Pt. A, Ptm, Go, Co, Ar, Pog,

Me, Pt.B. It was concluded from the study that some landmarks are more reproducible in

a horizontal direction and others in a vertical direction. B, A, Ptm,Go, & S, exhibited

acceptable levels of accuracy along the horizontal axis. A, S, Ptm exhibited acceptable

levels of along the vertical axis as well.

LANDMARK IDENTIFICATION ERROR IN POSTERIOR ANTERIOR

CEPHALOMETRICS

Paul W. Major, Donald E. Johnson and Karen L. Hesse conducted a study

which was designed to quantify the intraexaminer and interexaminer reliability of 52

commonly used posterior anterior cephalometric landmarks. The horizontal and vertical

identification errors were determined for a sample of 33 skulls and 25 patients. The

results show that there is a considerable range in the magnitude of error with different

horizontal and vertical values.

Interexaminer landmark identification error was significantly larger than

intraexaminer error for many landmarks. The identification error was different for the

skull sample compared to the patient sample for a number of landmarks. The relevance of

knowing the identification error for each landmark being considered in a particular

application was discussed.

Regardless of the clinical or research application, it is critical to know the

reliability of the reference landmarks. Baumrind and Frantz point out that there are two

general classes of error associated with cephalometric measurements. The first class of

errors is “projection” errors which arise from the geometry of the radiographic setup.

The fact that the x-ray beam originates from a source which has a finite size leads

to a penumbra effect or optical blurring. The x-ray beam diverges as it moves away from

the source, which results in an overall magnification of the object being radiographed and

a radial displacement of all points which are not on the principal axis (central ray). The

radiographic image is distorted as points closer to the film are magnified less than points

farther from the film.

The second general class of landmark errors may be termed “errors of

identification,” and arise due to uncertainty involved in locating specific anatomic

landmarks on the radiograph. The precision with which any landmark may be identified

depends on a number of factors.

Landmarks lying on a sharp curve or at the intersection of two curves are

generally easier to identify than points located on flat or broad curves.

Points located in areas of high contrast are easier to identify than points located in areas

of low contrast. Superimposition of other structures, including soft tissue over the area of

the landmark in question, reduces the ease of identification.

Precise written definitions describing the landmark reduces the chance of

interpretation error. Operator experience is an important factor since increased

knowledge of anatomy and familiarity with the radiographic appearance of the subject

reduces interpretive errors.

A literature review concerning the reliability of landmark identification in

posterior anterior cephalometrics revealed only one article, by El-Mangoury et al.,

which determined the horizontal, vertical and radial variability of 13 landmarks.

They found that each landmark had its own characteristic noncircular envelope of

error, and that the variability is different in the horizontal and vertical directions.

Unfortunately, the majority of posterior anterior cephalometric analyses use landmarks

whose identification error has not been independently reported.

CONCLUSION

Broadbent did not present the profession with a premature infant in the need of

artificial; life support and careful nurture. He gave us a gangling but vigorous adolescent

ready to enter the work force.

Clinical orthodontics is yet to fully utilize Broadbent’s contribution. He gave us a

three dimensional analysis, but orthodontics has remained preoccupied with the lateral

view. The lateral view is easy to work with and the patient is also much more

recognizable than in the frontal (P-A) view, especially with soft tissue enhancement. But

it is not enough.

We treat in three dimensions and the width dimensions that are visualized on the

frontal view are crucial in many cases. In these days of increasing awareness of the

contribution of muscular and respiratory function, we can no more afford to continue to

close our eyes to the information in the frontal view than we could afford to ignore the

lateral view up to now.

REFERENCES

1. Craniometry and Cephalometry: A History Prior to the Advent of

Radiography – Laetitia. M. Finlay ; Angle Orthodontist 1980

2. Fifty Years of Cephalometric Radiography – Editorial ; Angle Orthodontist

1981

3. A New X Ray Technique and its Application in Orthodontia – B. Holly

Broadbent ; Angle Orthodontist 1931

4. Radiographic cephalometry – Alexander Jacobson

5. Practice of Orthodontics – J.A. Salzmann

6. Orthodontic Cephalometry – Athanasios. E. Athanasiou

7. Oral Radiology – Paul .W. Goaz, Stuart. C. White

8. Cephalometric Radiography – Thomas Rakosi

9. Glossary of Orthodontic terms – John Daskalogiannakis

10. Contemporary Orthodontics – William R. Proffit

11. Lewis, A.B.: The impact of cephalometry on orthodontic concepts. Angle

Orthodontist, 1950

12. Some biological aspects of prognathism and occlusion of teeth, Angle

Orthodontist, 1951

13. Cephalometric Landmarks Identification & Reproducibility – A Meta analysis

– American journal of orthodontics 1997

14. Landmark identification error in posterior anterior cephalometrics Paul W.

Major, Donald E. Johnson, Karen L. Hesse- Angle Orthodontist, 1994

15. Résumé of the workshop and limitations of the technique – Salzmann, AJO-

DO 1958