Cephalometrics

CEPHALOMETRY
INTRODUCTION
www.indiandentalacademy.com

WHAT IS……
Cephalometrics is the interpretation of
lateral skull radiographs taken under
standardized conditions.
A collection of numbers intended to
summarize information from a cephalogram.

Purpose of Cephalometrics
Virtually indispensable to orthodontics.
Study craniofacial growth (comparing to the
same individual)
Diagnosis (comparing to standards)
Planning orthodontic treatment
Evaluation of treated cases

TWENTY CENTURIES OF
CEPHALOMETRY
THE SCIENTIFIC APPROACH TO SCRUTINY THE
HUMAN CRANIOFACIAL PATTERNS WAS DONE
FIRST BY ANTHROPOLOGISTS AND ANATOMISTS
ON DRY SKULLS.
THE MEASUREMENT OF DRY SKULL FROM
OSTEOLOGICAL LANDMARKS IS CALLED
CRANIOMETRY.
THE MEASUREMENT OF HEAD OF LIVING
SUBJECTS FROM BONY LANDMARKS LOCATED BY
PALPATION AND PRESSING THROUGH
SUPRAADJASCENT STRUCTURES IS CALLED
CEPHALOMETRY

TWENTY CENTURIES OF
CEPHALOMETRY(CONTD..)
HUMAN FORM HAS BEEN STUDIED FOR MANY
REASONS, HISTORICALLY
1. AS AN AID IN SELF PORTRAYAL IN
SCULPTURES,DRAWING,AND PAINTING
2. TO TEST THE RELATION OF PHYSIQUE TO
HEALTH, TEMPERAMENT, AND BEHAVIOUR
TRAITS.
HIPPOCRATES(500BC) DESIGNATED TWO FORMS
HABITUS PHTHISICUS(LONG THIN BODY)
HABITUS APOPLETICUS(SHORT THICK BODY)
ARISTOTLE(400BC),GALEN(200AD),
ROSTAN(1828) CARRIED ON WITH THE
RESEARCH

TWENTY CENTURIES OF
KRETSCHMER(1921) ADHERED TO THREE GREEK
FORMS
1. PYKNIC(COMPACT)
2. ASTHENIC( WITHOUT STRENGTH)
3. ATHLETIC
LATER HE INCLUDED DYSPLASTIC PHYSIQUE
MEASUREMENT AND PROPORTION
EGYPTIANS DEVELOPED A PROPORTIONATE
SYSTEM OF HUMAN BODY, KNOWN AS CANONS.
IT WAS ENCLOSED INTO A GRID WITH 18
HORIZONTAL LINES,LATER CHANGED INTO 22
LINE GRID SYSTEM.THE TOP THREE SQUARES
WERE DIVIDED INTO FIVE PARTS TO DRAW FACE
INTO ACCURATE DETAIL.

TWENTY CENTURIES OF
GREEK SYSTEM WAS NOT AS RIGID AS EGYPTIAN.
INDIAN ICONOMETRY – TWO PROPORTIONAL
SYSTEM WERE USED
1. SARIPUTRA
2.ALEKHYALAKSANA
FACE HEIGHT WAS USED AS MODULE FOR
BOTH. UNITS USED TO MEASURE
WERE
ANGULA. 1 ANGULA =8mm
IN BYZANTINE EMPIRE, RECTANGULAR GRID WAS
REPLACED BY SCHEME OF THREE CONCENTRIC
CIRCLES,WITH NOSE LENGTH AS RADIUS OF
CIRCLES.
LEONARDO DA VINCI,DRAWINGS SHOWED STUDY
OF PROPORTIONAL SYSTEM AND COORDINATEwww.indiandentalacademy.com

TWENTY CENTURIES OF
DURER WAS MOST OUTSTANDING, PROVIDED A
PROPORTIONATE ANALYSIS OF THE
LEPTOPROSOPIC AND EURYPROSOPIC FACE IN A
COORDINATE SYSTEM.
HE ALSO MADE USE OF TWO LINES TO GIVE
FACIAL ANGLE, SHOWED ABOUT THE VARIATION
IN FACIAL MORPHOLOGY.
PETRUS CAMPER GAVE REFERENCE PLANRE
CALLED CAMPERS HORIZONTAL LINE
VAN LOON 1915 ADVOCATED PROPER
ORIENTATION OF CAST ACCORDING TO FACE
PACINI1922 INTRODUCED A METHOD
STANDARDISED HEAD RADIOGRAPHY
IN 1931 CEPHALOMETRY RADIOGRAPHY CAME TO
FULL VERSION WHEN BROADBENT IN US AND
HOFRATH IN GERMANY SIMULTANEOUSLY
PUBLISHED METHOD OF STANDARDISED HEAD
RADIOGRAPHY.

RADIOGRAPHIC
CEPHALOMETRIC TECHNIQUE
BASIC EQUIPMENT FOR PRODUCING A LATERAL
CEPHALOGRAM ARE
AN X-RAY APPARATUS COMPRISES OF
AN X-RAY TUBE, A VACUUM TUBE SERVES AS
SOURCE OF X RAYS.
HAS 1. CATHODE, TUNGSTEN FILAMENT
SORROUNDED BY MOLYBDENUM FOCUSING
CUP, ACTS AS SOURCE OF ELECTRONS.
2. ANODE, SMALL TUNGSTEN BLOCK
EMBEDDED IN COPPER STEM, WHICH STOPS THE
ACCELERATED ELECTRONS AND TRANSFER
LESS THAN 1% INTO X RAY PHOTONS.

TRANSFORMERS, STEP DOWN PROVIDE LOW
VOLTAGE,10V AND HIGH CURRENT TO CATHODE
AND STEP UP, TO PROVIDE HIGH POTENTIAL
DIFFERENCE FOR GENERATION AND
ACCELARATION OF ELECTRON CLOUD.
FILTERS, MADE OF ALUMINIUM, FILTERS OUT
THE LOW ENERGY X RAYS.
COLLIMATORS,MADE OF LEAD, GIVES SHAPE TO
THE BEAM,SO THAT ONLY HIGH ENERGY BEAM
REACHES PATIENT
COOLANT SYSTEM, TO COOL THE ANODE BY
DISSIPATING ENERGY INTO OIL SORROUNDING
TUBE
2. IMAGE RECEPTOR SYSTEM, RECORDS THE FINAL
PRODUCT OF X RAYS AFTER THEY PASS
THROUGH SUBJECT. CONSISTS OF
AN EXTRA ORAL FILM,EITHER 8 INCHES INTO
10 INCHES OR 10 INTO 12 INCHES, SENSITIVE TO
FLOUROSCENT LIGHT RADIATED FROM
INTENSIFYING SCREENS.

CEPHALOSTAT
TWO EAR RODS PATIENT HEAD IS FIXED BY INSERTED
THEM INTO EAR HOLES.
HAS INFRAORBITAL POINTER TO STANDARDIZE THE
POSITION
FORE HEAD CLAMP TO SUPPORT THE FACE,POSITIONED
AT NASION
PROPER ALLIGNMENT IS CHECKED IF RADIOPAQUE CIRCLE
OF FILM SIDE EAR ROD IS REASONABLY CENTERED IN
BEAM SIDE ROD.

PATIENT POSITIONING IN LATERAL
CEPHALOGRAM
F-H PLANE IS KEPT PARALLEL TO THE FLOOR AND
MID SAGITTAL PLANE PARALLEL TO CASSETTE
AND PERPENDICULAR TO THE FLOOR. SOME
PREFER CANTHOMEATEL LINE AT 10DEGREE TO
FLOOR www.indiandentalacademy.com

•THE STANDARDISED F-H PLANE IS ACHIEVED BY
PLACING THE ORBITAL POINTER BELOW THE ORBIT
TILL POINTER AND EAR RODS ARE PARALLEL
•NASAL POSITIONER IS PLACED.
•USUALLY LEFT SIDE FACES CASSETTE.
•THE PATIENT CLOSES IN CENTRIC OCCLUSION WITH
TONGUE PLACED IN POSTERIOR AREA OF SOFT
PALATE. www.indiandentalacademy.com

NATURAL HEAD POSITION..WHY?
•NATURAL HEAD POSITION IS A STANDARDISED
AND REPRODUCIBLE POSITION OF THE HEAD IN AN
UPRIGHT POSTURE WHEN PERSON IS FOCUSSING
ON DISTANT OBJECT AT EYE LEVEL.(MOORREES)
•IN 1884 FRANKFORT AGREEMENT. FH PLANE WAS
CONSIDERED AS STANDARD PLANE FOR ALL
CRANIOMETRIC RESEARCH.
•BUT DOWNS SHOWED THE VARIATION IN CANT OF
F-H PLANE(1956)
•BJORK(1951) ALSO SHOWED IN TWO ADULT BANTU
MEN THE VARIATION IN S-N PLANE WHEN BOTH
WERE SHOWN TO HAVE SAME PROFILE WHEN
ALLIGNED IN IN NATURAL HEAD POSITION
•VERY FREQUENTLY LEFT AND RIGHT EARS ARE
ASSYMETRICALIN HORIZONTAL AND VERTICAL
DIRECTION www.indiandentalacademy.com

ORIENTATION OF NATURAL
HEAD POSITION
VARIOUS METHODS
•SOME ACCEPT MOST RELAXED POSITION OF THE
HEAD (SELF BALANCE POSITION)
•ORHAN PROPOSED “TARGET ON THE MIRROR
TECHNIQUE”
•SERDAR USUMEZ(2001) DEVICED AN INCLINOMETER
WHICH WAS VERY USE FUL IN REPRODUCING THE
NATURAL HEAD POSITION
•NATURAL HEAD POSTURE
IT’S THE ORTHOPOSITION OF THE
SUBJECTS NAMELY MOMENTARY INTERIM POSITION
WHEN TAKING THE FIRST STEP FROM STANDING TO
WALKING POSTURE.

NATURAL HEAD POSITION VS
NATURAL HEAD POSTURE
NOT INTERCHANGEABLE AS POSTURE IS
RECORDED IN DYNAMIC MOTION AND MORE
PHYSIOLOGIC IN CHARACTER AND
CHARCTERISTIC OF AN INDIVIDUAL WHERE AS
POSITION IS A STATIC AND IS MEASURED BY
STANDARDISED PROCEDURE APPLIED TO ALL
INDIVIDUALS.
MOORREES PROPOSES LATERAL CEPH TO BE
TAKEN IN STANDARDISED NATURAL HEAD
POSITION.
NATURAL HEAD POSTURE IS THE ONE IN WHICH
PATIENT PRESENTS HIMSELF TO THE WORLD SO
WHY NOT TO USE IT.

TRACING OF CEPHALOGRAM
ITEMS REQUIRED 1.A
1.LATERAL CEPHALOGRAM
2.ACETATE MATTE TRACING PAPER
3.SHARP 3H PENCIL
4.MASKING TAPE
5. A PROTRACTOR
6.SHEETS OF CARD BOARD
7. VIEW BOX

TRACING TECHNIQUE
Cephalogram is placed on
the view box and taped
and fixed
Place the matte acetate
film over the radiograph
and tape it securely.
The shining slide is placed
down.
Trace the three
registration crosses.

Now the
bilateral
structures are
first traced
independently
and average is
drawn by visual
approximation,
represented by
broken line.

Stepwise Tracing Technique
Section 1; Soft tissue profile, external
cranium and vertebra
1. Draw three registration crosses
2Trace Soft Tissue Profile
3.Trace external contour of cranium
4. Trace outline of atlas and axis
vertebra


Section 2; Cranial base internal border of cranium,
frontal sinus than ear rods
, 5.Trace internal border of cranium
    6.Trace orbital roof
    7.Trace outline of pituitary fossa or sella
turcica
.    8. Trace planum sphenoidale .
9 .Trace frontal sinus
10 Trace dorsum sella
11 Trace occipital bone
12 Trace outline of floor of middle cranial
fossa

Section 3: Maxilla
14 Trace outline of nasal bone
15 Trace piriform aperture
16 Trace lateral orbital margins and infra orbital
ridges
17. Trace outline of key ridges
18. Trace Pterygomaxillary fissure
19. Trace anterior nasal spine
20. Trace superior outline of nasal floor
separating oral and nasal cavity

21.      Trace posterior nasal spine
22.      Trace outline of maxillary first
molars
23.      Trace anterior outline of maxilla
from ANS inferiorly, overlying roots of
maxillary incisors.
24Trace outline of maxillary incisors
Section 4; Mandible
25      Trace anterior border of symphysis
of mandible


    26  Trace internal marrow space of
symphysis                                              27
Trace inferior border of mandible        28

29.      Trace mandibular condyles
30.      Trace mandibular notches
31.      Trace anterior aspect of
RAMI interiorly
32.      Trace mandibular first
molars.
33.      Trace most anteriorly
placed lower incisors

Landmarks and reference points
CEPHALOMATRIC LANDMARKS
TYPES
ANATOMIC REPRESENT ANATOMIC STRUCTURES
OF SKULL (ANTHROPOLOGICAL )
DERIVED LAND MARKS THAT HAVE BEEN OBTAIN
SECONDARILY FROM ANATOMIC STRUCTURES
(CONSTRUCTED)

PROPERTIES OF REFERENCE
POINTS
EASE OF LOCATION
ACCORDING TO MOYERS : IT DEPENDS UPON,
QUALITY OF THE RADIOGRAPHS
OVERLAPPING ANATOMICAL CONTOURS
OBSERVER EXPERIENCE
CONSTANCY OF CONTOURS
THIS STRUCTURES OF SKULL SHOWS DEPENDENCE ON AGE,
SEX, RACE, GROWTH ETC. THUS CONSTANCY IS NOT
RELIABLE IN CONTRA DISTINCTION TO THE POINTS
LOCATED CLOSE TO THE BASE OF SKULL, WHERE
VARIATION IS MINIMAL.

REQUIREMENTS OF REFERENCE
POINTS
EASILY SEEN
UNIFORM IN OUTLINE AND SHOULD BE
REPRODUCIBLE
LAND MARKS SHOULD PERMIT VALID
QUANTITATIVES MEASUREMENT OF LINE AND
ANGLE PROJECTED FROM THEM

No.             Code Definition
    1                N    Nasion. The most
         anterior point of the nasofrontal suture in
the median plane.  The skin nasion (N1
) is
located at the point of maximum convexity
between nose and forehead.
    2              S Sella. The sella point
(S) is defined as the midpoint of the hypohysial
fossa.  It is a constructed (radiological) point in
the median plane.

3             Se Midpoint of the entrance
to the sella, according to A.M.Schwarz at the
same level as the jugum
sphenoidale,independent of the depth of the
sella.  This point represents the midpoint of the
line connecting the posterior clinoid process and
the anterior opening of the sella turcica.
  4            Sn Subnasale, A skin point;
the point at which the nasalseptum merges
mesially with the integument of the upper lip
• 5         A              Point A, subspinale.  The
deepest midline point in the curved bony outline
from the base to the alveolar process of the
maxilla, i.e. at the deepest point between the
anterior nasal spine and prosthion. In
anthropology, it is known as subspinale
•

6 APMax The anterior landmark for
determining the length of the maxilla. It is
constructed by dropping a perpendicular
from point A to the palatal plane.

7 Pr Prosthion. Alveolar rim of the
maxilla; the lowest most anterior point on
the alveolar portion of the premaxilla, in the
median plane, between the upper central
incisors.
8 Is (or Is⊥) Incisor superius. Tip of
the crown of the most anterior maxillary
centrals.

9 AP⊥ Apicale ⊥. Root apex of the
most anterior maxillary central incisor.

10 Ii (or IsT) Incisor inferius. Tip of the
crown of the most anterior mandibular
central incisor.

11 AP T Apicale T. Root apex of the most
anterior mandibular central incisor.

12 Id Infradentale. Alveolar ridge of the
mandible; the highest, most anterior point
on the alveolar process, in the median plane,
between the mandibular central incisors.

13 B PointB, supramentale. Most
anterior part of the mandibular base. It is the
most posterior point in the outer contour of the
mondibular alveolar process, in the median
plane. In anthropology, it is known as
supramentale, between infradentale and
pogonion.
14 Pog Pogonion, Most anterior point
of the bony chin, in the median plane.


15 Gn Gnathion. This point is
defined in a number of ways.
According to Martin and Saller (1956),
it is located in the median plane of the
mandible, where the anterior curve in
the outline of he chin merges into the
body of the mandible. Many authors
have located gnathion between the
most anterior and the most inferior
point of the chin. Graig defines it with
the aid of the facial and the mondibular
plane; according to Graig, gnathion is
the point of intesectin of these two
planes. Muzi and May give it as the
lowest point of the chin (A.M.Schwarz
uses the same definition) and therefore
synonymous with Menton

16 Go Gonion. A constructed point, the
intersection of the lines tangent to the posterior
margin of the ascending ramus and the mandibular
base.
• 17 Me Menton. According to Krogman and
Sassouni, Menton is the most caudal point in the
outline of the symphysis; it is regarded as the lowest
point of the mandible and corresponds to the
anthropological gnation.
•
• 18 APMan The anterior landmark for determining the
length of the mandible. It is defined as the
perpendicular dropped from Pog to the mandibular
plane.
•
•

19 Ar Articulare. This point was
introduced by Bjork (1947). It provides
radiological orientation, being the point of
intersection of the posterior margin of the
ascending ramus and the outer margin of
the cranial base.
20 Cd Condylion. Most
superior point on the head of the condyle
21 Or Orbitale. Lowermost point of
the orbit in the radiograph
22 Pn/2 A constructed point. It
is obtained by bisecting the Pn vertical,
between its intersectin with the palatal
plane and point N’.


23 Int.FH/ Intersection of the ideal
Frankfurt horizontal and the
R.asc. posterior margin of the
ascending ramus.

24 ANS Anterior nasal spine. Point ANS is
the tip of the bony anterior nasal spine, in
the median plane.
It corresponds to the
anthropological acanthion.
25 PNS Posterior nasal spine. This is a
constructed radiological point, the
intersection of a continuation of the
anterior wall of the pterygopalatine fossa
and the floor of the nose. It marks the
dorsal limit of the maxilla.


26 S’ Landmark for assessing the length of the
maxillary base, in the posterior section. It is defined as
a perpendicular dropped from point S to a line
extending the palatal plane.
27 APOcc Anterior point for the occlusal plane.
A constructed point, the midpoint in the incisor
overbite in occlusion.
28 PPOccPosterior point for the occlusal plane. The
most distal point of contact between the most posterior
molars in occlusion.
29 Ba Basion. Lowest point on the anterior
margin of the foramen magnum in the median
plane.

3 30 Ptm Pterygomaxillary fissure.
The contour of the fissure projected onto the palatal
plane. The anterior wall represents the maxillary
tuberosity outline, the posterior wall the anterior curve of
the pterygoid process.
This point corresponds to PN

SOFT TISSUE PROFILE
ANATOMY
The visible surface of the soft tissue facial
profile extends from the hairline (trichion) (1)
to the superior cervical crease (2)
The three superposed level may be
differentiated:
   The upper, frontal level, which belongs to
the cranium and is located between the
hairline (1) and the supraorbital ridge(3);
        The middle, maxillary level, which is
situated between the supraorbital ridge (3)
and the occlusal plane; and
·        The inferior, mandibular level, which is
located between the occlusal plane and the
superior cervical crease.

Cephalometric landmarks
G – glabella – the most prominent point in the
midsagittal plane of forehead;
• Ils- inferior labial sulcus-the point of greatest than
cavity in the midline of the low lip between labrale
inferius and mention;
• Li – Labrale inferius –the median point in the
lower margin of he lower membranous lip;
• Ls – labrale superius – the median point in the
lower margin of the upper margin of the upper
membranous lip;
• Ms – menton soft tissue – the constructed point
of intersection of a vertical co-ordinate from menton
and the inferior soft tissue contour of the chin;
•

Ns- nasion soft tissue-the point of deepest
con-cavity of the soft tissue contour of the root of
the root of the nose;
·        Pn – pronasale – the most prominent point of
the nose;
·        Pos – pogonion soft tissue – the most
prominent point o n the soft tissue contour of the
chin;
Ns- nasion soft tissue-the point of deepest con-
cavity of the soft tissue contour of the root of the
root of the nose;
·        Pn – pronasale – the most prominent point of
the nose;
·        Pos – pogonion soft tissue – the most
prominent point o n the soft tissue contour of the
chin; www.indiandentalacademy.com

Sls – superior labial sulcus – the point of
greatest concavity in the midline of the upper lip
between subnasale and labrale superius;
·        Sn –subnasale – the point where the lower
border of the nose meets the out contour of the
upper lip;
·        St – stomion – the midpoint between stomion
superius and stomion inferius;
·        Sti – stomion inferius – the highest point of
the lower lip;
·        Sts – stomion superius – the lowest point of
the upper lip


DENTITION (Cephalometric landmarks)
APOcc – anterior point for the occlusal plane – a
constructed point, the midpoint of the incisor
overbite in occlusion;
· Iia – incision inferius apicalis – the root apex
of the most anterior mondibular central incisor; if
this point is needed only for defining the long axis
of the tooth, the midpoint on the bisection of the
apical root width can be used;
· Iii – incision inferius incisalis – the incisal
edge of the most prominent mandibular central
incisior;
Isa – incision superius apicalis – the root
apex of themost anterior maxillary central incisor;
if this point is needed only for defining the long
axis of the tooth, the midpoint on the bisection of
the apical root width can be used;www.indiandentalacademy.com

•       Isi – incision superrius incisalis –the incisal
edge of the maxillary central incisor;
·        L1 – mandibular central incisor – the most
labial point on the crown of the mandibular
central incisor;
·        L6 – mondibular first molar – the tip of the
mesiobuccal cusp of the mandibular first
permanent molar;
·        PPOcc – posterior point for the occlusal
plane – the most distal point of contact between
the most posterior molars in occlusion (Rakosi);
·        U1 – maxillary central incisor – the most
labial point on the crown of the maxillary central
incisor;
U6 – maxillary first molar – the tip of the
mesiobuccal cusp of the maxillary first

PHARYNX
• ans – anterior nasal spine;
·        apw – anterior pharyngeal wall;
·        hy – hyoid;
·        pns – posterior nasal spine;
·        ppw – posterior pharyngeal wall;
·        pt – posterior point of tongue
·        ptm – pterygomaxillary fissure;
·        spw – superior pharyngeal wall;
·        U – tip of uvula;
·        Uo- point on the oral side of the soft
palate;
·        Up – point on the pharyngeal side of the
soft palate;
·        Ut – upper point of tongue.www.indiandentalacademy.com

cervical vertebrae
The cervical vertebrae make up the upper
part of the vertebral column. There are seven
cervical vertebrae. A typical cervical
vertebra consists of a body and a vertebral
arch.

·        cv2ap – the apex of the odontoid
process of the second cervical
vertebra;
·        cv2ip – the most inferoposterior point on
the body of the second cervical
vertebra;
·        cv2ia – the most inferoanterior point on
the body of the second;d
vertical vertebra;

·        cv3sp - the most superopostrior point on the
body of the third
cervical vertebra;
·        cv3ip – the most inferoposterior point on the
body of the third cervical
vertebra;
·        cv3sa – the most superoanterior point on the
body of the third cervical
vertebra;
·        cv3ia – the most inferoanterior point on the body
of the third cervical
vertebra;
·        cv4sp – the most suproposterior point on the
body of the fourth cervical
vertebra;
·        cv4ip – the moswt inferoposterior point on the
vertebra;
·        cv4sa – the most superoanterior poijnt on the
vertebra;

cv4ia – the most inferoanterior point on the
body of the fourth cervical·

cv5sp – the most suproposterior point on
the body of the fifth cervical
vertebra
       cv5ip - the most inferoposterior point on
the body of the fifth cervical
vertebra;
·       cv5sa – the most superoanterior point
on the body of the fifth cervical
vertebra;
the body of the fifth cervical vertebra;


• cv6sp – the most superoposterior point
on the body of the sixth cervical
vertebra;
·        cv6ip – the most inferoposterior point
vertebra;
·        cv6sa – the most superoanterior poijnt
vertebra;
the body of the sixth cervical
vertebra;

LINES AND PLANES IN
CEPHALOMETRICS
CAN BE OBTAINED BY CONNECTING
TWO LAND MARKS
BASED ON ORIENTATION, THEY CAN
BE
VERTICAL
HORIZONTAL

HORIZONTAL PLANES
S.N. PLANE
IT IS THE CRANIAL LINE BETWEEN THE CENTER OF SELLA
TURSICA (SELLA) AND THE ANTERIOR POINT OF THE
FRONTO-NASAL SUTURE (NASION). IT REPRESENTS THE
ANTERIOR CRANIAL BASE.
FRANKFORT HORIZONTAL PLANE
THIS PLANE CONNECTS THE LOWEST POINT OF TE ORBIT
(ORBITALE) AND THE SUPERIOR POINT OF THE EXTERNAL
AUDITORY MEATUS (PORTION).

PALATAL PLANE
IT IS A LINE LINKING THE ANTERIOR
NASAL SPINE OF THE MAXILLA AND THE
POSTERIOR NASAL SPINE OF THE PALATINE
BONE.
OCCLUSAL PLANE
IT IS A DENTURE PLANE BISECTING THE
POSTERIOR OCLUSION OF THE PERMANENT
MOLARS AND PREMOLARS (OR DECIDUOUS
MOLARS IN MIXED DENTITION) AND
EXTENDS ANTERIORLY.

MANDIBULAR PLANE
SEVERAL MANDIBULAR PLANES ARE
USED IN CEPHALOMETRICS, BASED ON
THE ANALYSIS BEING DONE. THE MOST
COMMONLY USED ONES ARE:
TANGENT TO THE LOWER BORER OF THE
MANDIBLE (TWEED).
A LINE CONNECTING GONION AND GNATHION
(STEINER)
A LINE CONNECTING GONION AND MENTON
(DOWNS)

REFERNCE PLANES

REFERENCE PLANES

BASION – NASION PLANE
IT IS A LINE CONNECTING THE BASION AND NASION.
IT REPRESENTS THE CRANIAL BASE.
BOLTON’S PLANE
THIS IS A PLANE THAT CONNECTS THE BOLTON’S
POINTS POSTERIOR TO THE OCCIPITAL CONDYLES
AND NASION.
VERTICAL PLANES
A. POG LINE
IT IS A LINE FROM POINT A ON THE MAXILLA TO
POGONION ON THE MANDIBLE.
FACIAL PLANE
IT IS A LINE FROM THE ANTERIOR POINT OF THE
FRONTO-NASAL SUTURE (NASION) TO THE MOST
ANTERIOR POINT OF THE MANDIBLE (POGONION).
FACIAL AXIS
A LINE FROM PTM POINT TO CEPHALOMETRIC
GNATHION. www.indiandentalacademy.com

ERRORS OF CEPHALOMETRIC
MEASUREMENTS
RADIOGRAPHIC PROJECTION ERRORS

ERRORS WITHIN THE MEASRUING SYSEM

ERRORS IN LANDMARK IDENTIFIATION

RADIOGRAPHIC PROJECTION ERRORSRADIOGRAPHIC PROJECTION ERRORS

MAGNIFICATION
OCCURS BECAUSE THE X-RAY BEAMS ARE
NOT PARALLLEL WITH ALL THE POINTS IN
THE OBJECT

THE MAGNITUDE OF ENLARGEMENT IS
RELATED TO THE DISTANCES BETWEEN THE
FOCUS THE OBJECT AND THE FILM

LONG FOCUS-FILM DISTANCES ARE
FAVOURABLE

USE OF ANGULAR RATHER THAN LINEAR
MEASUREMENTS IS A CONSISTENT WAY TO
ELIMINATE THE IMPACT OF MANGIFICATION

DISTORTIONDISTORTION OCCURS BECAUSE OF DIFFERENT
MAGNIFICATION BETWEEN DIFFERENT PLANES.

SOME LANDMARK ARE USEFUL FOR
SUPERIMPOSING RADIOGRAPHS ARE AFFECTED BY
DISTORTION, OWING TO THEIR LOCATION IN A
DIFFFERENT DEPTH OF FIELD.

BOTH LINEAR AND ANGULAR MEASUREMENTS
WILL BE VARIOUSLY AFFECTED.
A COMBINATION OF INFORMATION FROM LATERAL
AND FRONTAL FILMS HAS BEEN PROPOSED.
MISALIGNMENT OR TILTING OF THE
CEPHALOMETRIC COMPONENTS (E.G. THE FOCAL
SPOT), THE CEPHALOSTAT, AND THE FILM WITH
RESPECT TOEACH OTHER, AS WELL AS ROTATIONS
OF THE PATIENTS’S HEAD IN ANY PLANE OF
SPACE, WILL INTRODUCE ANOTHER FACTOR OF
DISTORATION www.indiandentalacademy.com

ERRORS WITHIN THE MEASURING SYSTEMERRORS WITHIN THE MEASURING SYSTEM

BECAUSE OF PARALLAX AND MECHANICAL
ERRORS.

ERRORS RELATED TO THE RECORDING
PROCEDURE HAVE TWO COMPONENTS.

1. PRECISION WITH A MARKED POINT ON
THE FILM OR TRACING CAN BE IDEENTIFIED BY
THE CROSS-HAIR OF THE RECORDING DEVICE
AND

2. THE ERRORS OF THE DIGITZING SYSTEM.

AN ACCURACY OF 0.1MM IS DESIRABLE,
WITHOUT ANY DISTORTION OVER THE SURFACE
OF THE DIGITIZER (HOUSTON, 1979).


ERRORS IN LANDMARK IDENTIFICATION

LANDMARK IDENTIFICATION ERRORS ARE
CONSIDERED THE MAJOR SOURCE OF
CEPHALOMETRIC ERROR.

FACTORS INCLUDE

1.THE QUALITY OF THE RADIOGRAPHIC
IMAGE
2.THE PRECISION OF LANDMARK DEFINTION
AND THE REPRODUCIBILITY OF LANDMARK
LOCATIONS; AND
3. THE OPERATOR AND THE REGISTRATION
PROCEDURE.

QUALITY OF RADIOGRAPHIC IMAGE

EXPRESSED IN TERMS OF SHARPNESS – BLUR
AND CONTRAST – AND NOISE.

SHARPNESS IS THE SUBJECTIVBE PRECEPTION
OF THE DISTINCTNESS OF THE BOUNDARIES OF
A STRUCTURE IT IS RELATED TO BLUR AND
CONTRAST.

BLUR IS THE DISTANCE OF THE OPTICAL
DENSITY CAHNGE BETWEEN THE BOUNDARIES
OF A STRUCTURE AND ITS SURROUNDINGS .

RESULTS FROM THREE FACORS GEOMETRIC
UNSHARPNESS,RECEPTOR UNSHARRPNESS
MOTION UNSHARPNESS

• CONTRAST IS THE MAGNITUTDE OF
THE OPTICAL DESNITY DIFFERENCES
BETWEEN A STRUCTURE AND ITS
SURROUNDINGS.
INCREASED CONTRAST ENHANCES
THE SUBJECTIVE PERCEPTION OF
SHARPNESS.
CONTRAST IS DETERMINED BY
1.THE TISSUE BEING EXAMINED
2.THE RECEPTOR AND
3.THE LEVEL OF Kv USED.
MOST IMPORTANT BEING
THE FILM-CASSETTE SYSTEM AND THE
KV LEVEL USED.

NOISE REFERS TO ALL FACTORS THAT
DISTURB THE SIGNAL IN A RADIOGRAPH.
RELATED TO
1. THE RADIOGRAPHIC COMPLEXITY OF THE
REGION
2. RECEPTOR MOTTLE OR QUANTUM NOISE.
THESE TYPES OF ERRORS CAN BE
MINIMIZED BY FILMS OF HIGH QUALITY.

PRECISION OF LANDMARK DEFINITION AND
REPRODUCIBILITY OF LANDMARK LOCATION.
BAUMRIND AND FRANTZ POINTED OUT THAT
ERRORS IN LANDMARK LOCATIONS ARE
FUNCTION OF THREE VARIABLES

1.                  THE ABSOLUTE MAGNITUDE OF THE
ERROR IN LANDMARK LOCATION.
2.                  THE RELATIVE MAGNITUDE OF THE
LINEAR DISTANCE ANGULAR OR LINEAR
MEASUREMENT.
3.                  THE DIRECTION FROM WHICH THE
LINE CONNECTING THE LANDMARKS
INTERCEPTS THEIR ENVELOPE OF ERRORS.

ENVELOP IS THE PATTERN OF THE TOTAL
ERROR DISTRIBUTION.

• ADVANTAGES OF THE CEPHALOMETRY

1. ONLY AVAILABLE METHOD THAT PERMITS THE
INVESTIGATION OF THE SPATIAL RELATIONSHIPS
BETWEEN CFRANIAL STRUCTURES AND BETWEEN
DENTAL AND SURFACE STRUCTURES
2. MODER ECONOMICAL22 IN COMPARISON TO
COMPUTED TOMOGRAPHY AND MRI.
3. NON-INVASIVE AND NON-DESTRUCTUVE THUS
PRODUCING A RELATIVELY HIGH INFORMATION YELD AT
RELATIVELY LOW PHYSIOLOGIC COST.
4. STANDARDIZED CAN BE USED FOR SERIOAL
ASSEMENTS OF GROWTH AND ONGOING PRCOESSES OF
TREATMENT
5. CEPHALMETRICS PRODUCES TANGIBLE
PHYSICAL RECORDS THAT ARE RLEATIVELY
PERMANENT.
6. THE SAM SETS OF CEPHALOGRAMS CAN BE
USED FOR TESTING DIFFERENT THEORIES AND
HYPOTHESES.
7. THEY ARE RELATIVELY EASY TO STORE
REPRODEUCE AND TRANSPORTwww.indiandentalacademy.com

LIMITATIONS OF CEPHALOMETRY

RADIATION EXPOSURE ARE REAL

CEPHALOMETRICS IS CHARACTERIZED BY A
NUMBER OF TECHNICAL LIMITATIONS.

THE ABSENCE OF ANATOMICAL REFERENCES
WHOSE SHAPE AND LOCATION REMAIN CONSTANT
THROUGH TIME

INHERENT AMBIGUITY IN LOCATING ANATOMICAL
LANDMARKS AND SURFACES ON X-RAY IMAGES
SINCE THE IMAGES LACK HARD EDGES, SHADOWS,
AND WELL DEFINED OUTLINES.

THEY ARE TWO DIMENSIONAL IMAGES OF THREE
DIMENSIONAL . THIS CONTRADICTION LEAD TO
DIFFERENTIAL PROJECTIVE DISPLACEMENT OF
ANATOMICAL STRUCTURES LYING AT DIFFERENT
PLANES WITHIN THE HEAD.

CONCLUSION
Indispensable diagnostic aid but
requires proper skill and technique
and an eye of an expert to
interpret ate.

Cephalometrics

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