GITAM DENTAL COLLEGE & HOSPITAL

DEPARTMENT OF

ORAL AND MAXILLOFACIAL SURGERY

SEMINAR ON

CEPHALOMETRICS IN ORTHOGNATHIC SURGERY

Presented By:

Dr. DORCUS PRIYA EDWIN

II MDS

CONTENTS

INTRODUCTION

AIM & OBJECTIVES

HISTORY

RADIOGRAPHIC CEPHALOMETRIC TECHNIQUE

CEPHALOMETRIC LANDMARKS

TRACING TECHNIQUE AND IDENTIFICATION OF LANDMARKS

SOFT TISSUE ANALYSIS

HARD TISSUE ANALYSIS

CEPHALOMETRIC PREDICTION TRACING

LIMITATIONS & CONTROVERSIES IN CEPHALOMETRICS

RECENT ADVANCES

CONCLUSION

REFERENCES

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.

Orthognathic surgery is routinely performed for patients with dentofacial deformity and

has been conducted for more than 100 years. Orthognathic surgery has created new and

exciting opportunities in the treatment of patients with dentofacial deformities.

TREATMENT OBJECTIVES IN ORTHOGNATHIC SURGERY:

1. Function

2. Esthetics

3. Stability

The success of orthognathic surgery depends on the effective communication between the

orthodontist, patient and maxillofacial surgeon.

Treatment should commence only after both the orthodontist and surgeon have consulted

with the patients and the treatment plan should be jointly prepared (records can be

duplicated).

A complete examination of the patient should include:

1. General patient evaluation

a. Medical history

b. Dental evaluation

i. History

ii. General evaluation

iii. Periodontal considerations

iv. Occlusal-oral function evaluation

2. Sociopsychologic evaluation

3. Esthetic facial evaluation

a. Frontal analysis

b. Profile analysis

4. Radiographic evaluation

a. Lateral cephalometric evaluation

b. Antero-posterior cephalometric evaluation

c. Full mouth periapical evaluation

d. Panoramic evaluation

5. Occlusion and study cast evaluation

a. Intra-arch relationship

b. Interarch relationship

6. Temporomandibular joint evaluation

CEPHALOMETRICS is a technique employing oriented radiographs for the purpose of making

head measurements. The term cephalometrics is used to describe the analysis and

measurements made on a cephalometric radiograph.

The use of cephalometrics for orthodontic diagnosis and treatment planning in modern times

owes much to some of the early works laid down by certain pioneers of science, who carefully

and meticulously studied the osteology of the cranium.

Cephalometric normative values have been identified as guidelines to diagnosis and treatment

planning. Cephalometric analysis has been used as a standard because of the ease of procuring,

measuring and comparing hard tissue structures. The belief that treating to cephalometric hard

tissue norms results in a pleasing face is far behind in the thoughts of the current trend of

diagnosis and treatment planning.

The information from lateral and posteroanterior cephalometric radiographs forms an

important part of the database for orthognathic surgical treatment planning. Although clinical

evaluation must be the primary treatment tool in determining surgical treatment of the

orthognathic patient, cephalometric analysis is a helpful diagnostic guide.

The primary objective of treatment is not to make the patients’s cephalometric measurements

normal, but rather to make the facial appearance harmonious and occlusal function normal.

AIM & OBJECTIVES

- To understand the technical aspects, landmarks, lines and planes of cephalometrics

- To help in orthodontic diagnosis by enabling the study of skeletal and soft tissue

structures.

- Describe the subject’s dento-facial morphology

- Quantitative description of morphological deviations

- Make diagnostic and treatment planing decisions

HISTORY PRIOR TO THE ADVENT OF RADI O GRAPHY

The assessment of cranio-facial structures forms a part of orthodontic diagnosis

- Historically human form has been measured for many reasons:

1. self portrayal in sculpture, drawing and painting.

2. relation of physique - health, temperament and behavioral traits.

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.

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 3000 BC. 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).

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.

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

artist of great virtuosity.

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.

Craniometry can be said to be the forerunner of cephalometry. Craniometry involved the

measurement of craniofacial dimensions of skulls of dead persons. This method was not

practical in living individuals due to soft tissue envelop which made direct measurements

difficult and far less reliable.

The evolution of cephalometry in the twentieth century is universally linked to Edward Angle’s

publication of classification of malocclusion. With various motives and methods, mathematics

of measurement was applied to human form.

The discovery of x-rays in 1985 by Roentgen revolutionized dentistry. It provided a method of

obtaining the inner craniofacial measurements with quite a bit of accuracy and reproducibility.

In 1922 paccini standardized the radiographic head images by positioning the subjects against a

film cassette at a distance of 2 metres from the x-ray tube.

In 1931 Broadbent in USA and Hofrath in Germany simultaneously presented a standardized

cephalomertic technique using a high powered x-ray machine and a head holder called

cephalostat.

RADIOGRAPHIC CEPHALOMETRIC TECHNIQUE

The patient is positioned within the cephalostat using adjustable bilateral ear rods placed

within each auditory meatus. The midsagittal plane of the patient is vertical and parallel to the

film plane and perpendicular to the x-ray beam. The patient’s Frankfort plane (ie line

connecting the superior border of the external auditory meatus and infraorbital rim) is oriented

parallel to the floor. There is always a varying amount of magnification in any radiograph. The

amount of magnification is determined by the ratio of x-ray source-object distance and to

source-to-film distance.

CEPHALOMETRIC LANDMARKS

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

15"5 feetSource Plane

X-ray Source Patient in Head

Positioning Device

Mid-saggital Plane

Film Plane

X-ray Film in

Cassette

RADIOGRAPHIC CEPHALOMETRIC

TECHNIQUE

the construction of various cephalometric lines or planes and for subsequent numerical

determination of cephalometric measurement.

Reliable evaluation of a cephalometric radiograph depends on accurate definition and

localization of landmarks; there are certain soft t issue landmarks that are essential to the basic

understanding of the various analyses used today in clinical dentistry.

HARD TISSUE LANDMARKS:

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

curvature between the ANS and prosthion

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.

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 within 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.

TRACING TECHNIQUE AND IDENTIFICATION OF LANDMARKS

Before any attempts are made to trace a cephalometric head film, one should be thoroughly

familiar with gross anatomy of head, especislly the bony componenets of cranium and face. It

should be understood that a 2-dimentional cephalogram represents a 3-dimentional object and

that the bilateral structures will be projected onto the film. Bilateral structures are traced

independently. An average is then drawn by visual approximation, which is represented by a

broken line.

TRACING EQUIPMENT:

1. A lateral cephalogram with usual dimensions 8x10 inches

2. Acetate matte tracing paper (0.003 inches thick and 8x10 inches)

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

4. Masking tape

5. Protractor

6. Viewbox

7. Pencil sharpener and eraser

GENERAL CONSIDERATIONS:

1. Start with placing the cephalogram on the view box with patient’s image facing to right

2. Tape the four corners of the radiograh to the view box

3. With a fine felt tipped black pen draw 3 crosses on the radiograph, two on the cranium

and one on the cervical vertebrae. These registration crosses helps in reorienting the

acetate sheet for later verification.

4. Place the matte acetate sheet on the radiograph and secure it to radiograph and

viewbox

5. After firmly affixing the acetate film trace the three registration crosses

6. Print the patient’s name, record number, age, the date the cephalogram was taken and

your name in the bottom left hand corner of the acetate tracing

7. Begin tracing by identifying the relevant landmarks

8. While tracing use smooth continuous pressure on the pencil. Whenever possible trace

image lines without stopping or lifting the pencil. Avoid erasures.

LINES AND PLANES OF LATERAL CEPHALOMETRICS

PLACEMENT OF THREE

ORIENTATION CROSSES

AVERAGING OF BILATERAL IMAGES ON TRACI

NG USING

A BROK

EN LINE

A cephalometric evaluation of the craniofacial complex requires a plane of reference from

which we can assess the location of various anatomic structures. Tradit ionally two planes have

been used, namely the sella turcica-nasion (SN) plane and the Frankfort horizontal (FH).

1) Blumenbach’s plane (Resting horizontal plane) - It is the plane formed as the skull,

minus the mandible rest on a flat horizontal surface. Entails the skull resting anterior on

maxillary teeth and posterior either on occipital condyles or on the mastoid process.

2) Broadbent’s line (S-N reference line) – From sella to nasion.

3) Broadbent Bolton line – Line from Bolton patient to nasion.

4) Broca’s line – Extends from true anatomic prosthion to the lower most point of the

occipital condyle. When skull is resting on horizontal surface.

5) Camper’s line – Line extending from tip of ANS to the centre of external auditory

meatus. Camper’s plane is a triangular plane formed by two lines from tip of ANS to

each external auditory meatus.

6) Decoster’s line – This is the only line that is not linear connection of two points. It

represents an actual anatomical contour of the planoethmoidal line from internal plate

of frontal bone down through roof of cribriform plate to the anterior portion of sella

turcica.

7) Frankfort horizontal plane) – Its origins date back to the international congress on

prehistoric anthropology and archaeology, held in Frankfort in 1882. The line runs from

orbitale to porion. It is supposed to represent the ideal horizontal position of the head

when the patient stands erect.

8) Palatal plane – Line running from ANS to PNS.

9) His plane – Runs from acanthion to opisthion.

10) Hold way line – Also referred as harmony line was developed by R.A. Holdaway and is

strictly a soft tissue profile assessment reference line. Runs from soft tissue pogonion to

vermilion border of upper lip.

11) Huxley’s line – Runs from nasion to basion and referred as nasion – basion line. It

would be the near perfect base reference line for research purposes on growth and

development.

12) Mandibular plane – Four different mandibular planes.

Steiner – Line joining Go and Gn

Downs – Line joining Go and Me

Tweed and Ricketts – Straight line tangent to the lower most border of mandible.

Bimpler’s line – Line from menton to antigonial notch.

13) Margolis line – Line runs from nasion to spheno-occipital-synchondrosis.

14) Occlusal plane – 3 occlusal planes.

First plane – Line joining midpoint of overlap of M-B cusps of upper and lower first

molars with point bisecting overbite of incisions. Used by Downs and Steiner.

Second plane – Used by Ricketts and in Wits analysis called as functional occlusal plane

and is line joining the midpoint of the overlap of M-B cusp of I st molars and buccal cusps

of premolars or deciduous molars.

Third plane – Line joining midsection of molar cusps to the tip of upper incisors.

15) Orbital plane – Plane perpendicular to FH plane at orbitale.

16) Ramal plane – Line tangent to posterior border of ramus of mandibular.

17) Rickett’s esthetic line –Extends from soft tissue tip of nose to the most anterior portion

o profile of soft tissue chin.

18) Von Ihering’s line – Orbitale to center of external auditory meatus.

19) Y-axis – Given by Downs and extends from sella to gnathion.

20) Constructed horizontal (cHP) plane - Legan and Burstone suggest using a constructed

horizontal . This is a line drawn through nasion at an angle of 7 degrees to the SN line.

This constructed horizontal tends to be parallel to true horizontal . However, in those

cases in which SN is excessively angulated, even the constructed horizontal would not

approximate true horizontal, in which case an alternative reference line must be sought.

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.

METHODS OF CEPHALOMETRIC ANALYSIS

Two basic approaches

- Metric approach - use of selected linear and angular measures

- Graphic approach - “overlay” of individual’s tracing on a reference template and visual

inspection of degree of variation

orbitaleporionsellanasion

In 1946, Dr. Charles Tweed developed Tweeds diagnostic triangle. First true classic full scale

cephalometric analysis developed by William B. Downs in 1948.

In 1953, Dr. C.C. Steiner presented his famous Steiner’s analysis. Riedel in 1952

developed SNA and SNB angle. Sassouni (1995) described total archial analysis.

Rickets (1960) give dynamic analysis to study morphology of a patient at different stages

of development or treatment. Jacobson’s ‘Wits’ appraisal (1975) was used for assessing

horizontal disharmony of the jaw.

For surgical correction quadrilateral analysis Dipaolo (1970) and an analysis by

McNamara (1984) developed.

BURSTONE HARD TISSUE ANALYSIS:

PLANES

• SN PLANE

• HP PLANE

• PALATAL PLANE

• OCCLUSAL PLANE

• MANDIBULAR PLANE

• Constructed points like Gnathion & Gonion

CRANIAL BASE: Length of cranial base is measured from Articulare to nasion parallel to HP

• Ar-Ptm

• Ptm-N

- Ar-PTM is measured parallel to HP to determine the horizontal distance between the

posterior aspects of mandible and maxilla.

- Male – 37.1 +/- 2.8

- Female – 32.8+/-1.9

- Increase or decrease in these values indicates prognathism/retrognathism

- PTM – N :MALE 52.8 +/- 4.1; FEMALE 50.9 +/- 3

HORIZONTAL SKELETAL PROFILE ANALYSIS

In this analysis all measurements are made parallel to HP

N-A-Pg(angle) - This measurement indicates the degree of skeletal convexity

Male – 3.9 +/- 6.4o Female – 2.6 +/- 5.1o ; + ve angle indicates convex face; -ve angle

indicates concave face

N-A (Linear) - Here apical base of maxilla is related to N. Used to determine if anterior

part of maxilla is protrusive/retrusive. Male – 0.0 +/- 3.7 Female - -2 +/- 3.7; +ve

indicates prognathism ; -ve indicates retrognathism

N-B (Linear) - Here apical base of mandible is related to N. Male - -5.3 +/- 6.7;

Female - -6.9 +/- 4.3 ; This quantitates the AP position of mandible and degree of

mandibular horizontal dysplasia

N-Pg (Linear) - This indicates prominence of chin. Used to determine discrepancy in

alveolar process, chin or mandibular proper Also determines the discrepancy in genials

Male - -4.3 +/- 8.5; Female - -6.5 +/- 5.1

VERTICAL SKELETAL ANALYSIS

• In this analysis all measurements are made perpendicular to HP.

• Reflects the anterior, posterior or complex dysplasia of face.

N-ANS(Linear) - It signifies the middle third facial height. Male – 54.7 +/- 3.2

Female – 50 +/- 2.4

ANS-GN(Linear) - It signifies the lower third facial height. Male – 68.6 +/- 3.8;

Female – 61.3 +/- 3.3

PNS-N(Linear) - It signifies the posterior maxillary height Male – 53.9 +/- 1.7

Female – 50.6 +/- 2.2

MP-HP(Angle)- It signifies the posterior divergence of mandible shown by MP angle.

The angle relates the posterior facial divergence with respect to anterior facial

height. Male - 23o +/- 5.9o ; Female – 24.2o +/- 5o

VERTICAL DENTAL ANALYSIS

• Measurements for this analysis

- UI perpendicular to NF - It denotes the anterior maxillary dental height. Aids to

evaluate the total vertical dimensions of premaxilla from approximate piriform

aperture perpendicular to tip of maxillary incisor crown. Signifance: indicates

how far the incisor have erupted in relation to nasal floor. Male - 30.5 +/- 2.1;

Female – 27.5 +/- 1.7

- LI perpendicular to MP - This measures the anterior mandibular dental height.

Determines the total dmensions of anterior mandible from MP perpendicular to

tip of mandibular incisor crown. Signifance: denotes how far the incisor have

erupted in relation to MP ; Male - 45 +/- 2.1; Female – 40.8 +/- 1.8

- U6 perpendicular to NF - This measures the posterior maxillary dental height.

Aids to evaluate the posterior dental mandibular vertical height/molar eruption

Male - 26.2 +/- 2 ; Female – 23 +/- 1.3

- L6 perpendicular to MP - Measures the posterior mandibular dental height;

Male - 35.8 +/- 2.6; Female – 32.1 +/- 1.9

MAXILLA AND MANDIBLE ANALYSIS

• This is analysed by following measures

- PNS – ANS - Denotes the total effective length of maxilla. Male - 57.7 +/- 2.5

Female – 52.6 +/- 3.5

- AR – GO - Quantitates the length of mandibular ramus Male - 52 +/- 4.2 ;

Female – 46.8 +/- 2.5

- GO - PG - Aids in establishing the length of mandibular body. Male – 83.7 +/-

4.6; Female – 74.3 +/- 5.8

- AR-GO-GN - This angle denotes relationship between ramal plane and MP. Aids

in diagnosis of skeletal open/closed bite problems. Male – 119.1o +/- 6.5o ;

Female – 122o +/- 6.9o

- B – PG - This measurements denotes prominence of chin related to mandibular

denture base. Male - 8.9 +/- 1.7; Female – 7.2 +/- 1.9

DENTAL ANALYSIS

Measurements for this analysis

- OP – HP (Angle) - OP denotes its steepeness/flatness. Increased angle: assess skeletal

open bite, lip incompetence,increased facial height, retrognathia. Decreased angle:

assess deep bite, decreased facial height, lip redundancy. Male - 6.2o+/- 5.1o ; Female –

7.1o+/-2.5o

- A – B(Linear) - This linear measurements represents the relationship of maxillary and

mandibular apical base to OP Male - -1.1 +/- 2 ; Female - -0.4 +/- 2.5 Significance: if A-B

distance is large with point B projected posteriorly to point A denotes class II occlusion

and vice versa

- U1 – NF(Angle) - Represents angulations of maxillary central incisors to NF Male - 111o

+/- 4.7o Female – 112o +/- 5.3o Signifance: aids to determine the

procumbency/recumbency of incisor . Vitals in assessing long term stability of dentition

- L1 – MP(Angle) - Denotes angulation of mandibular incisors to MP; Male - 95.9o+/- 5.2o

Female – 95.9o+/-5.7o Significance: determines the procumbency/recumbency of lower

incisor.

SOFT TISSUE ANALYSIS

The soft-tissue envelope of the face plays an important role in esthetics, functional balance and

facial harmony. Today the soft t issue evaluation receives an awesome acknowledgement and is

recognized by every cl inician that the success of orthodont ic treatment is closely related to the

soft tissues changes of the face.

VARIOUS SOFT TISSUE ANALYSIS HAVE BEEN PUT FORTH:

Steiner

Ricketts

McNamara

Merrifield’s Z angle

Holdaway

Burstone – COGS

Arnett, Bergman et al - STCA

Burstone CJ (1958) pointed out the importance of analyzing the soft t issues around the skeletal

structures and out lined the procedure for taking the cephalograms used for analyzing the soft t

issue. He pointed out that the average profile must be considered depending upon individual,

ethnic, racial and imperial factors.

FACIAL FORMS ANALYSIS

This analysis describes overall horizontal soft tissue profile.

The following analysis is used:

Facial convexity angle(G-Sn-Pg) - Mean value 12o +/- 4o ; +ve value indicates a convex

profile; -ve value indicates concave profile

Maxillary prognathism(G-Sn) - Describes the amount of maxillary excess/deficiency in

AP ; +ve - maxillary retrusion; -ve - maxillary procumbency ; Mean value 6+/-3

Mandibular prognathism(G-Pg) - Mean value 0 +/- 4; Indicates mandibular

prognathism/ retrognathism . Increase –ve value indicates mandibular deficiency

HORIZONTALPLANECOLUMELLA

GNATHION

CERVICAL POINT

Vertical height ratio(G-Sn/Sn-Me) - Mean value 1:1 (G-Sn To Sn-Me) Inference : Ratio

<1 denotes that disproportionality and there is large lower 3rd face height and vice-versa

Lower face throat angle(Sn-Gn-C) - Mean value - 100o +/- 7o

Lower vertical height depth ratio(Sn-Gn/C-Gn) - Mean value 1.2:1; Inference : Ratio>1

indicates short neck

LIP POSITION AND FORM ANALYSIS

The following analysis is used

- Nasolabial angle(Cm-Sn-Ls) - Mean value 102o +/- 8o ; Inference : obtuse angle

indicates maxillary hypoplasia and vice-versa

- Upper lip protrution(Ls to Sn-Pg) - Mean value 3 +/- 1; Inference : Increased value

indicates protrusion and vice-versa

- Lower lip position(Li to Sn-PG) - Mean value 2 +/- 1; Inference: Denotes amount of lip

protrusion

- Mento labial sulcus(Si to Li-Pg) - Mean value 4 +/- 2; Inference: Assess prominence of

the chin

- Vertical lip chin ratio(Sn-Stms/Stmi-Me) - Aids to assess the lower 3rd face. Lower 3rd

face is divided into 3 parts: length of upper lip i.e distance from Sn-Stms shoule be

approximately 1/3rd the total and distance from stmi to Me should be 2/3rd.

- Maxillary incisor exposure(Stm-U1) - Distance from upper lip to maxillary incisor is the

key factor in determining vertical position of maxilla. This corresponds to pleasing smile.

- 2mm of incisor exposure at rest is normal Inference: pt. with vertical maxillary excess

tend to show a larger amount of upper incisor with lips in repose.

- Interlabial gap(Stms-Stmi) - Mean value – 2+/-2; Aids to measure the vertical distance

between upper lip and lower lip with lips at rest. Inference: patient with vertical

maxillary excess have increased interlabial gap and lip incompetence and vice-versa

SURGICAL-ORTHODONTIC CEPHALOMETRIC PREDICTION TRACING

By Epker and Fish (1980 JCO) adopted in part from the mechanics developed by Ricketts for

cephalometric analysis, growth prediction and visual treatment objective construction as

presented by Bench, Gugino, and Hilgers.

1) To accurately assess the profile esthetic results which will result from the proposed

surgery,

2) To consider the desirability of simultaneous adjunctive procedures such as genioplasty,

suprahyoid myotomy, etc.,

Li

PogSm

3) To help determine the sequencing of surgery and orthodontics (i.e., if the surgery is

done first will it be more difficult or easier to do the indicated orthodontics),

4) To help decide what type of orthodontics might best be employed (i.e., extraction

versus non-extraction)

5) To determine the anchorage requirements should extraction treatment be chosen

- The first step in producing a prediction tracing is to overlay a piece of acetate paper on

the original cephalometric tracing and trace all structures which will not be significantly

altered by the surgery and/or orthodontics

- Determination of Ideal Vertical Position for the Upper Incisor.

- Autorotation of the Mandible.

- Genioplasty Determination

- Placement of Teeth In Ideal Positions.

RECENT ADVANCES

Although the time honoured process of hand tracing and analyzing cephalograms is still

clinically useful, it has clear drawbacks. One major drawbacks is the amount of time required

for tracing. Another is the difficulty of presenting the data in a form that the avarage patient

can easily understand.

In an effort to address these problems a process of digitalization made it possible to insert

information on relative landmark positions into computer usable format.

The various advances in cephalometrics are:

Digital cephalometry

Laser scanning

Softwares

- Dolphin

- Vistadent

- OPAL

LIMITATIONS OF VARIOUS CEPHALOMETRIC ANALYSIS COMMONLY USED

ANB angle as a measure of jaw Dysplasia

• According to Steiner, the SNA reading indicates whether face protrudes or retrudes

bellow the skull. Although the ANB is a reliable indication of A-P jaw relationship in most

instances, there are many situations in which this reading cannot be relied on.

• The ANB angle in normal occlusions is generally 2 degrees. Angle greater than this mean

value indicate tendency toward class II jaw disharmonies; smaller angles (negative

readings) reflect class III jaw discrepancies. While this is an acceptable generalization,

numerous instances exist in which this does not apply.

Cephalometrics for you and me – Steiner – 1953 ;AJO

• Porion and Orbitale are not accurate for our use as we are not dealing with dry skulls.

• Points S and N are clearly visible in the X- ray pictures and can be located easily and

accurately.

• Emphasizes that points S and N are located in the mid sagittal plane of the head and

therefore they are moved a minimum amount whenever the head deviates from the

true profile position and that the points are located on hard non yielding tissue.

• The same holds true for a rotation of the occlusal plane: backward (counterclockwise)

rotation of the occlusal plane has a decreasing effect on the ANB angle, though sagittal

basal relationships remain constant.

Shortcomings of ANB angle

• Taylor in 1969 pointed out that ANB angle did not always indicate true apical base

relationship. Varied horizontal discrepancies of points A and B could give the same ANB

measurement because variation in the vertical distance from nasion could compensate

for other variation.

• Beatty in 1975 reported that ANB angle is not always an accurate method of

establishing the actual amount of apical base divergence.

• As an alternative to ANB angle for measuring apical base discrepancy , he devised the

AXD angle, where point- x is located by projecting point A on to a perpendicular to SN

line. Point D is located in the bony sympyhsis as described by Steiner. The two variables,

nasion and point B, were eliminated. He also introduced a linear measurement AD, to

describe the A-P relationship of the jaws.

• Cross evaluation with different reference planes is important and can be demonstrated

with the ANB angle.

• If one takes only the ANB angle to measure the relative position of maxilla and

mandible to each other ,one must realize that any different horizontal or vertical

position of point N and the location of the points A and B in the vertical plane will have

an influence on the size of this angle and not on the actual sagittal relation of the two

jaws. (Hussals and Nanda-1984)

STEINERS ANALYSES - Acceptable compromises:

• Steiner clearly recognized that cephalometric standards are merely gauges by which to

determine more favorable compromises as a treatment goal. He developed a chart that

reflects a number of average measurements of normal Dentofacial relationships.

• Steiner recognized variations in antero -posterior jaw relations to each other.

• The compromise describes the anticipated axial inclinations of the maxillary and

mandibular incisors to the NA and NB lines at various ANB relationships.

Soft tissue analyses- Holdaway

• NASO LABIAL ANGLE – formed by two lines namely the columella tangent and an upper

lip tangent. Arbitrary value is 90 to 110 degrees.

• Legan and Burstone report a mean value of 102 +/- 4 degrees.

• Scheidman et al drew a postural horizontal line through subnasale and further divided

the nasolabial angle into columella tangent to postural horizontal ( 25 degrees) and

upper lip tangent to postural horizontal ( 85 degrees).

• They argue that each of these angles should be assessed individually in as much as they

vary independently.

• An apparently normal nasolabial angle may be oriented in an abnormal fashion, a fact

that would be disclosed if the component angles were measured individually.

CONCLUSION

• Although innumerable limitations exist in the field of cephalometrics. This is not to

suggest that cephalometry is not a useful measurement tool for use by clinical

orthodontist, it is still a very significant & effective diagnostic tool.

• A combination of various cephalometric norms and variables should be compiled to

arrive at a proper diagnosis.

REFERENCES:

1. Burstone CJ, Legan HL: Cephalometrics for orthognathic surgery, J Oral Surg

1978;36:269-277

2. Legan HL, Burstone CJ: Soft t issue cephalometric analysis for orthognathic surgery, J

Oral Surg 1980; 38:744-51

3. Text book of Radiographic Cephalometry by Alexander Jacobson.

4. Text book of Orthodontic current principals & tech; 4th edn, by T.M.Graber & Robert .L.

Vanarsadall

5. Textbook of Essentials of orthognathic surgery by Johan P Reyneke