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Cephalometrics
Introduction
• Origin: ‘Cephalo’ means head and ‘Metric’ is measurement
• Discovery of X-rays measurement of the head from shadows
of bony and soft tissue landmarks on the roentgenographic image
,known as the Roentgenographic Cephalometry.
• Spawned by the classic work of Broadbent in
United States and Hofrath in Germany,
cephalometrics has enjoyed wide acceptance
Frankfort Horizontal (FH)
1) A plane passing through three points of the right and left porion and the left
orbitale.
2) First proposed at the Craniometric Congress held in Munich, Germany, 1877.
3) An orientation of skull in a consistent and reproducible position.
4) Comparisons: natural head position; horizontal visual axis; and horizontal plane.
Skull: Lateral View
Skull: Frontal View
Skull: Basal View
Head Position
Soft Tissues
Magnification
Occlusion
Lip position
Standardized Lateral Cephalogram Lateral X ray of Skull
Standardized PA Ceph
Cephalometric imaging system
• X- ray apparatus
• An image receptor
• Cephalostat
15 cm
Water – Current mA – Xray radiation
Height – Voltage
Diameter of Nozzle – Collimation
Filter – Filteration
Refining - Attenuation
Time of opening – Exposure time
Detergent – Intensifying screen
Exposure Time
Attenuation
Attenuation
Uses of cephalogram
• In orthodontic diagnosis & treatment planning
• In classification of skeletal & dental abnormalities
• In establishing facial types
• In evaluation of treatment results
• In predicting growth related changes & changes
associated with surgical treatment
• Valuable aid in research work involving the cranio-
dentofacial region
-- Moyers
Principle of Cephalometric analysis
• To compare the patient with a normal reference
group, so that differences between the patient’s
actual dentofacial relationships and those expected
for his/her racial or ethnic groups are revealed
-- Jacobson
Goals of Cephalometrics
To evaluate the relationships, both horizontally and
vertically, of the five major functional components
of the face:
• The cranium and the cranial base
• The skeletal maxilla
• The skeletal mandible
• The maxillary dentition and the alveolar process
• The mandibular dentition and the alveolar process
-- Jacobson
Types of cephalograms
• Lateral cephalogram
 Also referred to as lateral
“cephs”
 Taken with head in a
standardized reproducible
position at a specific distance
from X-ray source
Uses :
 Important in orthodontic growth analysis
 Diagnosis & Treatment planning
 Monitoring of therapy
 Evaluation of final treatment outcome
• Posteroanterior (p-a)
cephalometric radiograph
Image Receptor and Patient
Placement:
 Image receptor is placed in front
of the patient, perpendicular to
the midsagittal plane and parallel
to the coronal plane
 The patient is placed so that the
canthomeatal line is
perpendicular to the image
receptor
• Position of The Central X-Ray Beam:
 Central beam is perpendicular to the image receptor,
directed from the posterior to anterior parallel to the
patient’s midsagittal plane and is centered at the
level of bridge of the nose.
• Resultant Image: the midsagittal plane should divide
the image into two symmetric halves.
 Uses :
 Provides information related to
skull width
 Skull symmetry
 Vertical proportions of skull,
craniofacial complex & oral
structures
 For assessing growth
abnormalities & trauma
Cephalometric landmarks
• A conspicuous point on a cephalogram that serves as a
guide for measurement or construction of planes –
Jacobson
• 2 types :
1. Anatomic: represent actual anatomic structure
of the skull eg – N, ANS, pt A, etc
2. Constructed: constructed or obtained
secondarily from anatomic structures in the
cephalogram eg– Gn, Go, S
• Requisites for a landmark
 Should be easily seen on the roentgenogram
 Be uniform in outline
 Easily reproducible
 Should permit valid quantitative measurement of
lines and angles
 Lines and planes should have significant relationship
to the vectors of growth
• S
Sella: the midpoint of Sella Turcica
• N
Nasion: the extreme anterior point on the
frontonasal suture
• ANS – Anterior Nasal Spine
Spina nasalis anterior: the extreme anterior
point on the maxilla
• PNS – Posterior Nasal spine
Spina nasalis posterior: the extreme posterior
point on the maxilla
• Pt
Pterygoid point: the extreme superior point of
the pterygopalatine fossa
• A
Point A: the deepest point in the curvature of
the maxillary alveolar process
• B
Point B: the deepest point in the curvature of
the mandibular alveolar process
• Pg
Pogonion: the extreme anterior point of the
chin
• Me
Menton: the extreme inferior point of the chin
• Gn
Gnathion: the midpoint between pogonion and
menton
• Go
Gonion: the midpoint of the mandibular angle
between ramus and corpus mandibulae
• O
Opisthion: the posterior border of foramen
magnum
• Ba
Basion: the anterior border of foramen
magnum
• Cd
Condylion: the extreme superior point of the
condyle
Lateral Cephalogram
• Hard tissue landmarks
Soft tissue landmarks
Tracing technique
• Tracing supplies & equipments
 Lateral ceph, usual dimensions of
8 x 10 inches (patients with facial
asymmetry requires antero
posterior head film)
 Acetate matte tracing paper (0.003
inches thick, 8 X 10 inches)
 A sharp 3H drawing pencil or a very
fine felt-tipped pen
• Masking tape
• A few sheets of cardboard (preferably black), measuring
approximately 6 x 12 inches, and a hollow cardboard tube
• A protractor and tooth-symbol tracing template for drawing
the teeth (optional)
• Dental casts trimmed to maximal intercuspation of the teeth
in occlusion
• Viewbox (variable rheostat desirable, but not essential)
• Pencil sharpener and an eraser
Stepwise tracing technique
–Section 1 : soft tissue profile, external
cranium, vertebrae
soft tissue profile
external cranium
vertebrae
-- Jacobson
 Section 2 : Cranial base, internal border of
cranium, frontal sinus, ear rods
internal border of cranium
Trace orbital roofs
Sella turcica
Planum sphenoidale
Bilaterally present
frontal sinuses
Dorsum sella
Superior, midline of occipital
bone
Floor of middle cranial fossa
Ear rods
• Section 3 : Maxilla & related structures including
nasal bone & pterygomaxillary fissures
nasal bone
Thin nasal maxillary bone surrounding
piriform aperture
Lateral orbital margins
Bilateral key ridges
Bilateral pterygomaxillary fissures
ANS
Superior outline of nasal floor
PNS
Anterior outline of maxilla
Outline of maxillary incisors
Maxillary first molars
• Section 4 : The mandible
Anterior border, symphysis
Marrow space of symphysis
Inferior border of mandible
Posterior aspect of rami
Mandibular condyles
Mandibular notches & coronoid process
Anterior aspect of rami
Mandibular first molars
Mandibular incisors
Averaging of bilateral images on tracing using a broken line
Cephalometric planes
• Are derived from at least 2 or 3 landmarks
• Used for measurements, separation of
anatomic divisions, definition of anatomic
structures of relating parts of the face to one
another
• Classified into horizontal & vertical planes
• Horizontal planes
 Frankfurt Horizontal plane
P
O
 Sella-Nasion plane
S N
• Basion-Nasion plane:
• Palatal plane:
• Occlusion plane:
Ba
N
ANSPNS
• Mandibular plane:
Different definitions are
given in different
analysis
1. Tweed- Tangent to
lower border of the
mandible
2. Downs analysis –
extends from Go to Me
3. Steiner’s anlysis –
extends from Go to Gn
Go
Gn
Me
Vertical planes
 Facial plane
• A-Pog line
• Facial axis
• E. plane (Esthetic plane)
Ptm
Gn
N
Pog
A
E plane
• STEINER ANALYSIS
 Developed by Steiner CC in 1930 with an idea
of providing maximal information with the
least no. of measurements
 Divided the analysis into 3 parts
 Skeletal
 Dental
 Soft tissue
• Skeletal analysis
 S.N.A angle
 Indicates the relative
antero-posterior
positioning of maxilla in
relation to cranial base
 >82° -- prognathic
maxilla (Class 2)
< 82°– retrognathic
maxilla (class 3)
S
N
A
Mean value -- 82°
 S.N.B angle
 Indicates antero-
posterior positioning of
the mandible in relation
to cranial base
> 80°-- prognathic
mandible
< 80°-- retrusive
mandible
S
N
B
Mean value-- 80°
 A.N.B angle
 Denotes relative
position of maxilla &
mandible to each other
> 2° –- class 2 skeletal
tendency
< 2°–- skeletal class 3
tendency
A
N
B
Mean value = 2°
Mandibular plane angle
Gives an indication of
growth pattern of an
individual
 < 32° -- horizontal
growing face
 > 32°– vertical growing
individual
S
N
Mean value = 32°
Occlusal plane angle
 Mean value = 14.5°
 Indicates relation of
occlusal plane to the
cranium & face
 Indicates growth
pattern of an
individual
S
N
• Dental analysis
 Upper incisor to N-A(angle)
 Normal angle = 22°
 Angle indicates relative
inclination of upper
incisors
 Increased angle seen in
class 2 div 1 malocclusion
N
A
Upper incisor to N-A (
linear)
 Helps in asssessing the
upper incisor
inclination
Normal value is 4 mm
Increase in
measurement –
proclined upper
incisors
N
A
 Inter-incisal angle
 < 130 to 131° -- class 2
div 1 malocclusion or a
class 1 bimax
 > 130 to 131° – class 2
div 2 malocclusion
Mean value = 130 to
131°
 Lower incisor to N-B
(angle)
 Indicates inclination of
lower central incisors
 >25 °-- proclination of
lower incisors
 < 25 °– retroclined
incisors
N
B
Mean value of 25 °
 Lower incisor to N-B
(linear)
 Helps in assessing lower
incisor inclination
 Increase in measurement
indicates proclined lower
incisors
 Normal value– 4mm
N
B
• Soft tissue analysis
 S line
QUESTIONS?
MEASUREMENT ANALYSIS
• DOWN’S ANALYSIS
 Given by WB Downs, 1925
One of the most frequently used cephalometric
analysis
 Based on findings on 20 caucasian individuals of
12-17 yrs age group belonging to both the sexes
 Consists of 10 parameters of which 5 are skeletal
& 5 are dental
• Skeletal parameters :
 Facial angle
 Average value is 87.8°, Range
82-95°
 Gives an indication of
anteroposterior positioning of
mandible in relation to upper face
 Magnitude increases in skeletal
class 3 cases, decreases in skeletal
class 2 cases
FH plane
N
Pog
Angle of convexity
 Reveals convexity or
concavity of skeletal
profile
 Average value 0°, Range =
-8.5 to 10°
 Positive angle or
increased angle –
prominent maxillary
denture base relative to
mandible
 Decreased angle , negative
angle – prognathic profile
N
A
Pog
A-B plane angle
 Mean value = -4.6°,
Range = -9 to 0°
 Indicative of maxillary
mandibular
relationship in relation
to facial plane
 Positive angle in class
3 malocclusion
Mandibular plane
angle
Mean value = 21.9°,
Range = 17 to 28°
Increased mandibular
plane angle
suggestive of vertical
grower with
hyperdivergent facial
pattern
FHplane
Go
Me
Y- axis (growth axis)
Mean value = 59° , range
= 53 to 66°
Angle is larger in class 2
facial patterns than in
class 3 patterns
Indicates growth pattern
of an individual
Angle greater than
normal – vertical growth
of mandible
Angle smaller than
normal – horizontal
growth of mandible
S
Gn
FH plane
• Dental parameters
 Cant of occlusal plane
 Mean value = 9.3° ,
Range = 1.5 to 14°
 Gives a measure of
slope of occlusal plane
relative to FH plane
FH plane
 Inter- incisal angle
 Average reading =
135.4° , range = 130 to
150.5°
 Angle decreased in
class 1 bimaxillary
protrusion & class 2 div
1 malocculsion
 Increased in class 2 div
2 case
 Incisor occlusal plane angle
 Average value = 14.5°, range =
3.5 to 20°
 Increase in the angle is
suggestive of increased lower
incisor proclination
 Incisor mandibular plane
angle
 Mean angulation is 1.4, range
= -8.5 to 7°
 Increase in angle is indicative
of lower incisor proclination
 Upper incisor to A-Pog
line
 Average distance is
2.7mm (range -1 to 5
mm)
 Measurement is more
in patients with upper
incisor proclination
Limitations of Downs analysis
• Too many landmarks
• Too many measurements
• Time consuming
-- Jacobson
• TWEED ANALYSIS
 Given by Tweed CH, 1950
 Used 3 planes to establish a diagnostic triangle --
1. Frankfurt horizontal plane
2. Mandibular plane
3. Long axis of lower incisor
 Determines position of lower incisor
• FMPA = 25 °
• IMPA = 90 °
• FMIA = 65 °
FH plane
Mand plane
 WITS APPRAISAL
 It is a measure of the extent to which maxilla &
mandible are related to each other in antero-
posterior or sagittal plane
 Used in cases where ANB angle is considered not so
reliable due to factors such as position of nasion &
rotation of jaws
• In males point BO is
ahead of AO by 1mm
• In females point AO &
BO coincide
• In skeletal class 2
tendency BO is usually
behind AO( positive
reading)
• In skeletal class 3
tendency BO is located
ahead of AO ( negative
reading)
– RICKETTS ANALYSIS
• Also known as Ricketts’ summary
descriptive analysis
• Given by RM Ricketts in 1961
• The mean measurements given
are those of a normal 9 year old
child
• The growth dependent variables
are given a mean change value
that is to be expected and
adjusted in the analysis.
Dr. RM Ricketts
-- Jacobson
Landmarks
• This is a 11 factor summary analysis that
employs specific measurements to
Locate the chin in space
Locate the maxilla through the convexity of
the face
Locate the denture in the face
Evaluate the profile
• This analysis employs somewhat less traditional
measurements & reference points
En = nose
DT = soft tissue
Ti = Ti point
Po = Cephalometric
Gn = Gnathion
A6 = upper molar
B6 = Lower molar
Go = gonion
C1 = condyle
DC = condyle
• Xi point --
Planes
• Frankfurt horizontal --
Extends from porion to
orbitale
• Facial plane -- Extends
from nasion to pogonion
• Mandibular plane --
Extends from
cephalometric gonion to
• Pterygoid vertical -
- A vertical line
drawn through the
distal radiographic
outline of the
pterygomax
fissure &
perpendicular to
FHP
• Ba-Na plane --
• Occlusal plane --
Represented by line
extending through
the first molars &
the premolars.
• A-pog line -- Also
known as the dental
plane.
• E-line -- Extends
from soft tissue tip
Axis
Facial axis
Ptm
Gn
Condylar axis
Corpus axis
Interpretation
• This consists of analyzing:
– Chin in space
– Convexity at point A
– Teeth
– Profile
Chin in Space
This is determined by :
• Facial axis angle
• Facial (depth) angle
• Mandibular plane angle
• Facial axis angle
 Mean value is 90˚ ± 3˚
 Does not changes with
growth
 Indicates growth pattern of
the mandible & also
whether the chin is upward
& forward or downward &
backwards
• Facial (depth) angle
 Changes with growth
 Mean value is 87˚± 3˚ with an
increase of 1˚ every 3 years
 Indicates the horizontal
position of the chin &
therefore suggests whether
cl.II or cl.III pattern is due to
the position of the mandible
Facial (depth) angle
• Mandibular plane angle
 Mean -- 26˚± 4˚at 9 yrs
with 1˚decrease every 3
yrs
 High angle -- open bite –
vertically growing
mandible
 Low angle – deep bite –
horizontally growing
mandible
 Also gives an indication
about ramus height
Po
O
Convexity at point A
• This gives an indication
about the skeletal profile
• Direct linear measurement
from point A to the facial
plane
• Normal at 9 yrs of age is
2mm & becomes 1mm at
18 yrs of age, since
mandible grows more than
maxilla
Teeth
• Lower incisor to A-Pog
 Referred to as denture plane
 Useful reference line to measure
position of anterior teeth
 Ideally lower incisor should be
located 1 mm ahead of A-Pog line
 Used to define protrusion of lower
arch
• Upper molar to PtV
 Measurement is the distance
between pterygoid vertical to
the distal of upper molar
 Measurement should equal
the age of the patient
+3.0mm
 Determines whether the
malocclusion is due to
position of upper or lower
molars
 Useful in determining
whether extractions are
necessary
• Lower incisor
inclinations
 Angle between long axis of
lower incisors & the A-Pog
plane
 On average this angle this
angle should be 28 degrees
 Measurement provides
some idea of lower incisor
procumbency
Profile
• Lower lip to E plane
 Distance between lower lip &
esthetic plane is an indication of
soft tissue balance between lips
& profile
 Average measurement is -
2.0mm at 9 yrs of age
 Positive values are those ahead
of E- line
Mc NAMARA ANALYSIS
• Given By Mc Namara JA, 1984
• In an effort to create a clinically useful
analysis, the craniofacial skeletal complex is
divided into five major sections.
1. Maxilla to cranial base
2. Maxilla to mandible
3. Mandible to cranial base
4. Dentition
5. Airway
Dr. Mc Namara JA
-- Jacobson
MAXILLA TO CRANIAL BASE
• Soft tissue evaluation
 Nasolabial angle
 Acute nasolabial angle –
dentoalveolar protrusion,
but can also occur because
of orientataion of base of
nose
Cant of upper lip
 Line is drawn from
nasion perpendicular to
upper lip
 14 degree in females
 8 degree in males
• Hard tissue evaluation
 Anterior position of point A =
+ve value
 Posterior position of point A =
-ve value
 In well-balanced faces, this
measurement is 0 mm in the
mixed dentition and 1 mm in
adult
Maxillary skeletal protrusion
Maxillary skeletal retrusion
Maxilla to mandible
 Anteroposterior
relationship
 Linear relationship exists
between effective length
of midface & that of
mandible
• Any given effective
midfacial length
corresponds to effective
mandibular length within a
given range
• To determine maxillomandibular differential midfacial
length measurement is subtracted from mandibular
length
• Small individuals (mixed dentition stage) : 20-23mm
• Medium-sized : 27-30mm
• Large sized : 30-33mm
• Vertical relationship
 Vertical maxillary excess –
downward & backward
rotation of mandible,
increasing lower anterior
facial height
 Vertical maxillary
deficiency – upward &
forward rotation of
mandible, decreasing
lower anterior facial height
a) Lower Anterior Face Height
(LAFH)
 LAFH is measured from ANS to Me
 In well balanced faces it correlates
with the effective length of
midface
b) Mandibular plane
angle
• On average, the
mandibular plane angle is
22 degrees ± 4 degrees
• A higher value 
excessive lower facial
height
• lesser angle Lower
facial height
c) The facial axis angle
• In a balanced face --90
degrees to the basion-
nasion line
• A negative value 
excessive vertical
development of the face
• Positive values  deficient
vertical development of
the face
MANDIBLE TO CRANIAL BASE
• In the mixed dentition - pogonion on the average is
located 6 to 8 mm posterior to nasion perpendicular, but
moves forward during growth
• Medium-size face - pogonion is positioned 4 to 0 mm
behind the nasion perpendicular line
• Large individuals- the measurement of the chin position
extends from about 2 mm behind to approximately 2 mm
forward of the nasion perpendicular line
Dentition
a) Maxillary incisor position
• The distance from the point A
to the facial surface of the
maxillary incisors is measured
• The ideal distance  4 to 6
mm
b) Mandibular incisor
position
 In a well-balanced face,
this distance should be 1
to 3 mm
AIRWAY ANALYSIS• Upper Pharynx
Width measured from
posterior outline of the
soft palate to a point
closest on the pharyngeal
wall
The average nasopharynx
is approximately 15 to
20mm in width.
• Lower Pharynx
Width – point of intersection
of posterior border of
tongue & inferior border of
mandible to closest point on
posterior pharyngeal wall
 The average measurement is 11 to 14
mm, independent of age
 Greater than average lower
pharyngeal width-- possible anterior
THE HOLDAWAY SOFT TISSUE
ANALYSIS
• Given by Dr. Reed
Holdaway, 1984
• Dr. Reed Holdaway in
series of two articles
outlined the parameter of
soft tissue outline
• Analysis consists of 11
Dr. Reed Holdaway
-- Jacobson
1. Facial Angle (90
degree)
 Ideally the angle should
be 90 to 92 degrees
 >90 degree: mandible too
protrusive
 <90 degree: recessive
lower jaw
2. Upper lip curvature
(2.5mm)
 Depth of sulcus from a line
drawn perpendicular to FH
& tangent to tip of upper
lip
 Lack of upper lip curvature
– lip strain
 Excessive depths could be
caused by lip redundancy
or jaw overclosure
3. Skeletal convexity at
point A (-2to 2mm)
Measured from point A
to N’-Pog’ line
Not a soft tissue
measurement but a
good parameter to
assess facial skeletal
convexity relating to lip
position
4. H-Line Angle(7-15 degree)
 Formed between H-line &
N’-Pog’ line
 Measures either degree of
upper lip prominence or
amount of retrognathism of
soft tissue chin
 If skeletal convexity & H-line
angles donot approximate,
facial imbalance may be
evident
5. Nose tip to H-line
(12mm maximum)
 Measurement should not
exceed 12mm in individuals
14 yrs of age
6. Upper sulcus depth
(5mm)
 Short/thin lips -
measurement of 3
mm may be
adequate
 Longer/thicker lips-
• 7.Upper lip thickness
(15mm)
 Measured horizontally from
a point on outer alveolar
plate 2mm below point A to
outer border of upper lip
• 8. Upper lip strain
 Measured from
vermillion border of
upper lip to labial
surface of maxillary CI
 Measurement should
be approx same as the
upper lip thickness
(within 1mm)
• 9. Lower lip to H-
line(0mm)
 Measured from the most
prominent outline of the
lower lip
 Negative reading – lips are
behind the H line
Positive reading – lips are
ahead of H line
 Range of -1 to +2mm is
regarded normal
11. Soft tissue-chin
thickness (10-12mm)
• Measured as distance
between bony & soft
tissue facial planes
• In fleshy chins, lower
incisors may be
permitted to stay in a
more prominent
position, allowing for
Clinical implication of Cephalogram
• CVMI (Cervical Vertebrae maturity indicators)
Given by Hassel & Farman in 1985
Shapes of cervical vertebrae were seen at
each level of skeletal development
Provides a means to determine skeletal
maturity of a person & thereby determine
whether possibility of potential growth existed
 6 stages
• Stage 1
Stage of initiation
Corresponds to beginning of
adolescent growth with 80-
100% adolescent growth
expected
Inferior borders of C2,C3,C4
were flat
Vertebrae were wedge
shaped
• Stage 2
 Stage of acceleration
 Growth acceleration
begins with 65-85% of
adolescent growth
expected
 Concavities developed in
the inferior borders of C2
& C3
 Inferior border of C4 was
• Stage 3
 Stage of transition
 Corresponds to acceleration
of growth toward peak height
velocity with 25-65%
adolescent growth expected
 Distal concavities seen in
inferior borders of C2 & C3
 Concavity begin to develop in
inferior border of C4
• Stage 4
 Stage of deceleration
 Corresponds to
deceleration of adolesecent
growth spurt with 10% to
25% of adolescent growth
expected
Distinct concavities seen in
inferior borders of C2,C3,C4
 Vertebral bodies of C3 & C4
become more square in
• Stage 5
 Stage of maturation
 Final maturation of
vertebrae takes place
 5-10% adolescent growth
expected
 More accentuated
concavities seen in the
inferior borders of C2, C3
& C4
• Stage 6
 Stage of completion
 Little or no adolescent
growth could be
expected
 Deep concavities seen in
inferior borders of
C2,C3,C4
Bodies of C3 & C4 were
square & were greater in
Limitations of cephalometrics
• It gives two dimensional view of a three
dimensional object
• It gives a static picture which does not takes
time into consideration
• The reliability of cephalometrics is not always
accurate
• Standardization of analytical procedures are
difficult
Sources of error in Cephalometry
Error
Radiographic
projection errors
Causes of error How to minimize
the error
A) Magnification :
Enlargement
X ray beams are not parallel with
all points of the object
By using a long focus-
object distance & a short
object- film distance
B) Distortions:
Head being 3D
causes different
magnifications at
different depths of
field
Landmarks & structures not
situated in the midsaggital plane
are usually bilateral & may cause
dual images in radiographs
May be overcome by
recording the midpoint of
2 images
Rotation of patient’s head in any
plane of space in cephalostat may
produce linear/angular distortions
By standardized head
orientation using ear rods,
orbital pointer & forehead
rest
Error :
Errors within the
measuring system
Causes of error How to minimize the
error
Error may occur in the
measurement of various
linear & angular
measurements
Human error may creep in
during the tracing
measurements
Use of computerized
plotters & digitizers to
digitize the landmarks &
carry out the various linear
& angular measurements
has proved to be more
accurate
Error :
Errors in landmarks
identification
Causes of error How to minimize the error
A) Quality of radiographic
image
Poor definition of radiographs
may occur due to use of old
films & intensifying screen
although radiation dose is
reduced
Movement of object, tube or
film may cause a motion blur
Blurring of radiograph due to
scattered radiation that fogs
the film
Recommended films should
be used to avoid poor
definition radiographs
Stabilizing the object, tube,
film. By increasing the current
exposure time is reduced,
minimizing motion blur
Can be reduced by use of grids
Error :
Errors in landmarks
identification
Causes of error How to minimize the
error
B) Precision of landmark
definition & reproducibility
of landmark location
May occur if landmark is not
defined accurately, causes
confusion in identification of
landmark
In general certain landmarks
are difficult to identify such
as porion
Landmarks have to be
accurately defined. Certain
landmarks may require
special conditions to identify
which should be strictly
followed
Good quality radiography
C) Operator bias Variations in landmarks
identification between
operators
Advisable for the same
person to identify & trace
the patients
Conclusion
• There are numerable cephalometric analysis
given by different people each expressing
their ideas and ways to analyse, classify, and
treat the face
• All these analysis are still a two dimensional
representation of the three dimensional
structure
• Each has inherent deficiencies associated with
the analysis itself and those because of
• The future of cephalometrics depends on the
three dimensional analysis, their accuracy,
validity and reproducibility
• Still the value of the information and insight
given by these traditional analyses should not
be ignored or taken lightly
References
• Radiographic Cephalometrics – Alex
Jacobson
• Orthodontic Cephalometry – Athanasios E
Athanasiou
• Contemporary Orthodontics – William
Proffit
• Practice Of Orthodontics, Volume 1 &
Volume 2 - J. A. Salzmann
• Clinical Orthodontics, Volume 1 - Charles H
Tweed
• Orthodontics, The art & science – SI Balajhi

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lateral cephalometry in orthodontics

  • 2. Introduction • Origin: ‘Cephalo’ means head and ‘Metric’ is measurement • Discovery of X-rays measurement of the head from shadows of bony and soft tissue landmarks on the roentgenographic image ,known as the Roentgenographic Cephalometry. • Spawned by the classic work of Broadbent in United States and Hofrath in Germany, cephalometrics has enjoyed wide acceptance
  • 3. Frankfort Horizontal (FH) 1) A plane passing through three points of the right and left porion and the left orbitale. 2) First proposed at the Craniometric Congress held in Munich, Germany, 1877. 3) An orientation of skull in a consistent and reproducible position. 4) Comparisons: natural head position; horizontal visual axis; and horizontal plane.
  • 7. Head Position Soft Tissues Magnification Occlusion Lip position Standardized Lateral Cephalogram Lateral X ray of Skull
  • 9. Cephalometric imaging system • X- ray apparatus • An image receptor • Cephalostat
  • 10. 15 cm
  • 11. Water – Current mA – Xray radiation Height – Voltage Diameter of Nozzle – Collimation Filter – Filteration Refining - Attenuation Time of opening – Exposure time Detergent – Intensifying screen
  • 15.
  • 16.
  • 17. Uses of cephalogram • In orthodontic diagnosis & treatment planning • In classification of skeletal & dental abnormalities • In establishing facial types • In evaluation of treatment results • In predicting growth related changes & changes associated with surgical treatment • Valuable aid in research work involving the cranio- dentofacial region -- Moyers
  • 18. Principle of Cephalometric analysis • To compare the patient with a normal reference group, so that differences between the patient’s actual dentofacial relationships and those expected for his/her racial or ethnic groups are revealed -- Jacobson
  • 19. Goals of Cephalometrics To evaluate the relationships, both horizontally and vertically, of the five major functional components of the face: • The cranium and the cranial base • The skeletal maxilla • The skeletal mandible • The maxillary dentition and the alveolar process • The mandibular dentition and the alveolar process -- Jacobson
  • 21. • Lateral cephalogram  Also referred to as lateral “cephs”  Taken with head in a standardized reproducible position at a specific distance from X-ray source
  • 22. Uses :  Important in orthodontic growth analysis  Diagnosis & Treatment planning  Monitoring of therapy  Evaluation of final treatment outcome
  • 23. • Posteroanterior (p-a) cephalometric radiograph Image Receptor and Patient Placement:  Image receptor is placed in front of the patient, perpendicular to the midsagittal plane and parallel to the coronal plane  The patient is placed so that the canthomeatal line is perpendicular to the image receptor
  • 24. • Position of The Central X-Ray Beam:  Central beam is perpendicular to the image receptor, directed from the posterior to anterior parallel to the patient’s midsagittal plane and is centered at the level of bridge of the nose. • Resultant Image: the midsagittal plane should divide the image into two symmetric halves.
  • 25.  Uses :  Provides information related to skull width  Skull symmetry  Vertical proportions of skull, craniofacial complex & oral structures  For assessing growth abnormalities & trauma
  • 26.
  • 27. Cephalometric landmarks • A conspicuous point on a cephalogram that serves as a guide for measurement or construction of planes – Jacobson • 2 types : 1. Anatomic: represent actual anatomic structure of the skull eg – N, ANS, pt A, etc 2. Constructed: constructed or obtained secondarily from anatomic structures in the cephalogram eg– Gn, Go, S
  • 28. • Requisites for a landmark  Should be easily seen on the roentgenogram  Be uniform in outline  Easily reproducible  Should permit valid quantitative measurement of lines and angles  Lines and planes should have significant relationship to the vectors of growth
  • 29. • S Sella: the midpoint of Sella Turcica • N Nasion: the extreme anterior point on the frontonasal suture • ANS – Anterior Nasal Spine Spina nasalis anterior: the extreme anterior point on the maxilla • PNS – Posterior Nasal spine Spina nasalis posterior: the extreme posterior point on the maxilla • Pt Pterygoid point: the extreme superior point of the pterygopalatine fossa
  • 30. • A Point A: the deepest point in the curvature of the maxillary alveolar process • B Point B: the deepest point in the curvature of the mandibular alveolar process • Pg Pogonion: the extreme anterior point of the chin • Me Menton: the extreme inferior point of the chin • Gn Gnathion: the midpoint between pogonion and menton
  • 31. • Go Gonion: the midpoint of the mandibular angle between ramus and corpus mandibulae • O Opisthion: the posterior border of foramen magnum • Ba Basion: the anterior border of foramen magnum • Cd Condylion: the extreme superior point of the condyle
  • 32. Lateral Cephalogram • Hard tissue landmarks
  • 34. Tracing technique • Tracing supplies & equipments  Lateral ceph, usual dimensions of 8 x 10 inches (patients with facial asymmetry requires antero posterior head film)  Acetate matte tracing paper (0.003 inches thick, 8 X 10 inches)  A sharp 3H drawing pencil or a very fine felt-tipped pen
  • 35. • Masking tape • A few sheets of cardboard (preferably black), measuring approximately 6 x 12 inches, and a hollow cardboard tube • A protractor and tooth-symbol tracing template for drawing the teeth (optional) • Dental casts trimmed to maximal intercuspation of the teeth in occlusion • Viewbox (variable rheostat desirable, but not essential) • Pencil sharpener and an eraser
  • 36. Stepwise tracing technique –Section 1 : soft tissue profile, external cranium, vertebrae soft tissue profile external cranium vertebrae -- Jacobson
  • 37.  Section 2 : Cranial base, internal border of cranium, frontal sinus, ear rods internal border of cranium Trace orbital roofs Sella turcica Planum sphenoidale Bilaterally present frontal sinuses Dorsum sella Superior, midline of occipital bone Floor of middle cranial fossa Ear rods
  • 38. • Section 3 : Maxilla & related structures including nasal bone & pterygomaxillary fissures nasal bone Thin nasal maxillary bone surrounding piriform aperture Lateral orbital margins Bilateral key ridges Bilateral pterygomaxillary fissures ANS Superior outline of nasal floor PNS Anterior outline of maxilla Outline of maxillary incisors Maxillary first molars
  • 39. • Section 4 : The mandible Anterior border, symphysis Marrow space of symphysis Inferior border of mandible Posterior aspect of rami Mandibular condyles Mandibular notches & coronoid process Anterior aspect of rami Mandibular first molars Mandibular incisors
  • 40. Averaging of bilateral images on tracing using a broken line
  • 41. Cephalometric planes • Are derived from at least 2 or 3 landmarks • Used for measurements, separation of anatomic divisions, definition of anatomic structures of relating parts of the face to one another • Classified into horizontal & vertical planes
  • 42. • Horizontal planes  Frankfurt Horizontal plane P O
  • 44. • Basion-Nasion plane: • Palatal plane: • Occlusion plane: Ba N ANSPNS
  • 45. • Mandibular plane: Different definitions are given in different analysis 1. Tweed- Tangent to lower border of the mandible 2. Downs analysis – extends from Go to Me 3. Steiner’s anlysis – extends from Go to Gn Go Gn Me
  • 46. Vertical planes  Facial plane • A-Pog line • Facial axis • E. plane (Esthetic plane) Ptm Gn N Pog A E plane
  • 47. • STEINER ANALYSIS  Developed by Steiner CC in 1930 with an idea of providing maximal information with the least no. of measurements  Divided the analysis into 3 parts  Skeletal  Dental  Soft tissue
  • 48. • Skeletal analysis  S.N.A angle  Indicates the relative antero-posterior positioning of maxilla in relation to cranial base  >82° -- prognathic maxilla (Class 2) < 82°– retrognathic maxilla (class 3) S N A Mean value -- 82°
  • 49.  S.N.B angle  Indicates antero- posterior positioning of the mandible in relation to cranial base > 80°-- prognathic mandible < 80°-- retrusive mandible S N B Mean value-- 80°
  • 50.  A.N.B angle  Denotes relative position of maxilla & mandible to each other > 2° –- class 2 skeletal tendency < 2°–- skeletal class 3 tendency A N B Mean value = 2°
  • 51. Mandibular plane angle Gives an indication of growth pattern of an individual  < 32° -- horizontal growing face  > 32°– vertical growing individual S N Mean value = 32°
  • 52. Occlusal plane angle  Mean value = 14.5°  Indicates relation of occlusal plane to the cranium & face  Indicates growth pattern of an individual S N
  • 53. • Dental analysis  Upper incisor to N-A(angle)  Normal angle = 22°  Angle indicates relative inclination of upper incisors  Increased angle seen in class 2 div 1 malocclusion N A
  • 54. Upper incisor to N-A ( linear)  Helps in asssessing the upper incisor inclination Normal value is 4 mm Increase in measurement – proclined upper incisors N A
  • 55.  Inter-incisal angle  < 130 to 131° -- class 2 div 1 malocclusion or a class 1 bimax  > 130 to 131° – class 2 div 2 malocclusion Mean value = 130 to 131°
  • 56.  Lower incisor to N-B (angle)  Indicates inclination of lower central incisors  >25 °-- proclination of lower incisors  < 25 °– retroclined incisors N B Mean value of 25 °
  • 57.  Lower incisor to N-B (linear)  Helps in assessing lower incisor inclination  Increase in measurement indicates proclined lower incisors  Normal value– 4mm N B
  • 58. • Soft tissue analysis  S line
  • 60. MEASUREMENT ANALYSIS • DOWN’S ANALYSIS  Given by WB Downs, 1925 One of the most frequently used cephalometric analysis  Based on findings on 20 caucasian individuals of 12-17 yrs age group belonging to both the sexes  Consists of 10 parameters of which 5 are skeletal & 5 are dental
  • 61. • Skeletal parameters :  Facial angle  Average value is 87.8°, Range 82-95°  Gives an indication of anteroposterior positioning of mandible in relation to upper face  Magnitude increases in skeletal class 3 cases, decreases in skeletal class 2 cases FH plane N Pog
  • 62. Angle of convexity  Reveals convexity or concavity of skeletal profile  Average value 0°, Range = -8.5 to 10°  Positive angle or increased angle – prominent maxillary denture base relative to mandible  Decreased angle , negative angle – prognathic profile N A Pog
  • 63. A-B plane angle  Mean value = -4.6°, Range = -9 to 0°  Indicative of maxillary mandibular relationship in relation to facial plane  Positive angle in class 3 malocclusion
  • 64. Mandibular plane angle Mean value = 21.9°, Range = 17 to 28° Increased mandibular plane angle suggestive of vertical grower with hyperdivergent facial pattern FHplane Go Me
  • 65. Y- axis (growth axis) Mean value = 59° , range = 53 to 66° Angle is larger in class 2 facial patterns than in class 3 patterns Indicates growth pattern of an individual Angle greater than normal – vertical growth of mandible Angle smaller than normal – horizontal growth of mandible S Gn FH plane
  • 66. • Dental parameters  Cant of occlusal plane  Mean value = 9.3° , Range = 1.5 to 14°  Gives a measure of slope of occlusal plane relative to FH plane FH plane
  • 67.  Inter- incisal angle  Average reading = 135.4° , range = 130 to 150.5°  Angle decreased in class 1 bimaxillary protrusion & class 2 div 1 malocculsion  Increased in class 2 div 2 case
  • 68.  Incisor occlusal plane angle  Average value = 14.5°, range = 3.5 to 20°  Increase in the angle is suggestive of increased lower incisor proclination
  • 69.  Incisor mandibular plane angle  Mean angulation is 1.4, range = -8.5 to 7°  Increase in angle is indicative of lower incisor proclination
  • 70.  Upper incisor to A-Pog line  Average distance is 2.7mm (range -1 to 5 mm)  Measurement is more in patients with upper incisor proclination
  • 71. Limitations of Downs analysis • Too many landmarks • Too many measurements • Time consuming -- Jacobson
  • 72. • TWEED ANALYSIS  Given by Tweed CH, 1950  Used 3 planes to establish a diagnostic triangle -- 1. Frankfurt horizontal plane 2. Mandibular plane 3. Long axis of lower incisor  Determines position of lower incisor
  • 73. • FMPA = 25 ° • IMPA = 90 ° • FMIA = 65 ° FH plane Mand plane
  • 74.  WITS APPRAISAL  It is a measure of the extent to which maxilla & mandible are related to each other in antero- posterior or sagittal plane  Used in cases where ANB angle is considered not so reliable due to factors such as position of nasion & rotation of jaws
  • 75. • In males point BO is ahead of AO by 1mm • In females point AO & BO coincide • In skeletal class 2 tendency BO is usually behind AO( positive reading) • In skeletal class 3 tendency BO is located ahead of AO ( negative reading)
  • 76. – RICKETTS ANALYSIS • Also known as Ricketts’ summary descriptive analysis • Given by RM Ricketts in 1961 • The mean measurements given are those of a normal 9 year old child • The growth dependent variables are given a mean change value that is to be expected and adjusted in the analysis. Dr. RM Ricketts -- Jacobson
  • 77. Landmarks • This is a 11 factor summary analysis that employs specific measurements to Locate the chin in space Locate the maxilla through the convexity of the face Locate the denture in the face Evaluate the profile
  • 78. • This analysis employs somewhat less traditional measurements & reference points En = nose DT = soft tissue Ti = Ti point Po = Cephalometric Gn = Gnathion A6 = upper molar B6 = Lower molar Go = gonion C1 = condyle DC = condyle
  • 79.
  • 81. Planes • Frankfurt horizontal -- Extends from porion to orbitale • Facial plane -- Extends from nasion to pogonion • Mandibular plane -- Extends from cephalometric gonion to
  • 82. • Pterygoid vertical - - A vertical line drawn through the distal radiographic outline of the pterygomax fissure & perpendicular to FHP • Ba-Na plane --
  • 83. • Occlusal plane -- Represented by line extending through the first molars & the premolars. • A-pog line -- Also known as the dental plane. • E-line -- Extends from soft tissue tip
  • 87. Interpretation • This consists of analyzing: – Chin in space – Convexity at point A – Teeth – Profile
  • 88. Chin in Space This is determined by : • Facial axis angle • Facial (depth) angle • Mandibular plane angle
  • 89. • Facial axis angle  Mean value is 90˚ ± 3˚  Does not changes with growth  Indicates growth pattern of the mandible & also whether the chin is upward & forward or downward & backwards
  • 90. • Facial (depth) angle  Changes with growth  Mean value is 87˚± 3˚ with an increase of 1˚ every 3 years  Indicates the horizontal position of the chin & therefore suggests whether cl.II or cl.III pattern is due to the position of the mandible Facial (depth) angle
  • 91. • Mandibular plane angle  Mean -- 26˚± 4˚at 9 yrs with 1˚decrease every 3 yrs  High angle -- open bite – vertically growing mandible  Low angle – deep bite – horizontally growing mandible  Also gives an indication about ramus height Po O
  • 92. Convexity at point A • This gives an indication about the skeletal profile • Direct linear measurement from point A to the facial plane • Normal at 9 yrs of age is 2mm & becomes 1mm at 18 yrs of age, since mandible grows more than maxilla
  • 93. Teeth • Lower incisor to A-Pog  Referred to as denture plane  Useful reference line to measure position of anterior teeth  Ideally lower incisor should be located 1 mm ahead of A-Pog line  Used to define protrusion of lower arch
  • 94. • Upper molar to PtV  Measurement is the distance between pterygoid vertical to the distal of upper molar  Measurement should equal the age of the patient +3.0mm  Determines whether the malocclusion is due to position of upper or lower molars  Useful in determining whether extractions are necessary
  • 95. • Lower incisor inclinations  Angle between long axis of lower incisors & the A-Pog plane  On average this angle this angle should be 28 degrees  Measurement provides some idea of lower incisor procumbency
  • 96. Profile • Lower lip to E plane  Distance between lower lip & esthetic plane is an indication of soft tissue balance between lips & profile  Average measurement is - 2.0mm at 9 yrs of age  Positive values are those ahead of E- line
  • 97. Mc NAMARA ANALYSIS • Given By Mc Namara JA, 1984 • In an effort to create a clinically useful analysis, the craniofacial skeletal complex is divided into five major sections. 1. Maxilla to cranial base 2. Maxilla to mandible 3. Mandible to cranial base 4. Dentition 5. Airway Dr. Mc Namara JA -- Jacobson
  • 98. MAXILLA TO CRANIAL BASE • Soft tissue evaluation  Nasolabial angle  Acute nasolabial angle – dentoalveolar protrusion, but can also occur because of orientataion of base of nose
  • 99. Cant of upper lip  Line is drawn from nasion perpendicular to upper lip  14 degree in females  8 degree in males
  • 100. • Hard tissue evaluation  Anterior position of point A = +ve value  Posterior position of point A = -ve value  In well-balanced faces, this measurement is 0 mm in the mixed dentition and 1 mm in adult Maxillary skeletal protrusion Maxillary skeletal retrusion
  • 101. Maxilla to mandible  Anteroposterior relationship  Linear relationship exists between effective length of midface & that of mandible
  • 102. • Any given effective midfacial length corresponds to effective mandibular length within a given range
  • 103. • To determine maxillomandibular differential midfacial length measurement is subtracted from mandibular length • Small individuals (mixed dentition stage) : 20-23mm • Medium-sized : 27-30mm • Large sized : 30-33mm
  • 104.
  • 105. • Vertical relationship  Vertical maxillary excess – downward & backward rotation of mandible, increasing lower anterior facial height  Vertical maxillary deficiency – upward & forward rotation of mandible, decreasing lower anterior facial height
  • 106. a) Lower Anterior Face Height (LAFH)  LAFH is measured from ANS to Me  In well balanced faces it correlates with the effective length of midface
  • 107.
  • 108. b) Mandibular plane angle • On average, the mandibular plane angle is 22 degrees ± 4 degrees • A higher value  excessive lower facial height • lesser angle Lower facial height
  • 109. c) The facial axis angle • In a balanced face --90 degrees to the basion- nasion line • A negative value  excessive vertical development of the face • Positive values  deficient vertical development of the face
  • 110. MANDIBLE TO CRANIAL BASE • In the mixed dentition - pogonion on the average is located 6 to 8 mm posterior to nasion perpendicular, but moves forward during growth • Medium-size face - pogonion is positioned 4 to 0 mm behind the nasion perpendicular line • Large individuals- the measurement of the chin position extends from about 2 mm behind to approximately 2 mm forward of the nasion perpendicular line
  • 111.
  • 112. Dentition a) Maxillary incisor position • The distance from the point A to the facial surface of the maxillary incisors is measured • The ideal distance  4 to 6 mm
  • 113. b) Mandibular incisor position  In a well-balanced face, this distance should be 1 to 3 mm
  • 114. AIRWAY ANALYSIS• Upper Pharynx Width measured from posterior outline of the soft palate to a point closest on the pharyngeal wall The average nasopharynx is approximately 15 to 20mm in width.
  • 115. • Lower Pharynx Width – point of intersection of posterior border of tongue & inferior border of mandible to closest point on posterior pharyngeal wall  The average measurement is 11 to 14 mm, independent of age  Greater than average lower pharyngeal width-- possible anterior
  • 116. THE HOLDAWAY SOFT TISSUE ANALYSIS • Given by Dr. Reed Holdaway, 1984 • Dr. Reed Holdaway in series of two articles outlined the parameter of soft tissue outline • Analysis consists of 11 Dr. Reed Holdaway -- Jacobson
  • 117. 1. Facial Angle (90 degree)  Ideally the angle should be 90 to 92 degrees  >90 degree: mandible too protrusive  <90 degree: recessive lower jaw
  • 118. 2. Upper lip curvature (2.5mm)  Depth of sulcus from a line drawn perpendicular to FH & tangent to tip of upper lip  Lack of upper lip curvature – lip strain  Excessive depths could be caused by lip redundancy or jaw overclosure
  • 119. 3. Skeletal convexity at point A (-2to 2mm) Measured from point A to N’-Pog’ line Not a soft tissue measurement but a good parameter to assess facial skeletal convexity relating to lip position
  • 120. 4. H-Line Angle(7-15 degree)  Formed between H-line & N’-Pog’ line  Measures either degree of upper lip prominence or amount of retrognathism of soft tissue chin  If skeletal convexity & H-line angles donot approximate, facial imbalance may be evident
  • 121. 5. Nose tip to H-line (12mm maximum)  Measurement should not exceed 12mm in individuals 14 yrs of age 6. Upper sulcus depth (5mm)  Short/thin lips - measurement of 3 mm may be adequate  Longer/thicker lips-
  • 122. • 7.Upper lip thickness (15mm)  Measured horizontally from a point on outer alveolar plate 2mm below point A to outer border of upper lip
  • 123. • 8. Upper lip strain  Measured from vermillion border of upper lip to labial surface of maxillary CI  Measurement should be approx same as the upper lip thickness (within 1mm)
  • 124. • 9. Lower lip to H- line(0mm)  Measured from the most prominent outline of the lower lip  Negative reading – lips are behind the H line Positive reading – lips are ahead of H line  Range of -1 to +2mm is regarded normal
  • 125. 11. Soft tissue-chin thickness (10-12mm) • Measured as distance between bony & soft tissue facial planes • In fleshy chins, lower incisors may be permitted to stay in a more prominent position, allowing for
  • 126. Clinical implication of Cephalogram • CVMI (Cervical Vertebrae maturity indicators) Given by Hassel & Farman in 1985 Shapes of cervical vertebrae were seen at each level of skeletal development Provides a means to determine skeletal maturity of a person & thereby determine whether possibility of potential growth existed  6 stages
  • 127. • Stage 1 Stage of initiation Corresponds to beginning of adolescent growth with 80- 100% adolescent growth expected Inferior borders of C2,C3,C4 were flat Vertebrae were wedge shaped
  • 128. • Stage 2  Stage of acceleration  Growth acceleration begins with 65-85% of adolescent growth expected  Concavities developed in the inferior borders of C2 & C3  Inferior border of C4 was
  • 129. • Stage 3  Stage of transition  Corresponds to acceleration of growth toward peak height velocity with 25-65% adolescent growth expected  Distal concavities seen in inferior borders of C2 & C3  Concavity begin to develop in inferior border of C4
  • 130. • Stage 4  Stage of deceleration  Corresponds to deceleration of adolesecent growth spurt with 10% to 25% of adolescent growth expected Distinct concavities seen in inferior borders of C2,C3,C4  Vertebral bodies of C3 & C4 become more square in
  • 131. • Stage 5  Stage of maturation  Final maturation of vertebrae takes place  5-10% adolescent growth expected  More accentuated concavities seen in the inferior borders of C2, C3 & C4
  • 132. • Stage 6  Stage of completion  Little or no adolescent growth could be expected  Deep concavities seen in inferior borders of C2,C3,C4 Bodies of C3 & C4 were square & were greater in
  • 133. Limitations of cephalometrics • It gives two dimensional view of a three dimensional object • It gives a static picture which does not takes time into consideration • The reliability of cephalometrics is not always accurate • Standardization of analytical procedures are difficult
  • 134. Sources of error in Cephalometry Error Radiographic projection errors Causes of error How to minimize the error A) Magnification : Enlargement X ray beams are not parallel with all points of the object By using a long focus- object distance & a short object- film distance B) Distortions: Head being 3D causes different magnifications at different depths of field Landmarks & structures not situated in the midsaggital plane are usually bilateral & may cause dual images in radiographs May be overcome by recording the midpoint of 2 images Rotation of patient’s head in any plane of space in cephalostat may produce linear/angular distortions By standardized head orientation using ear rods, orbital pointer & forehead rest
  • 135. Error : Errors within the measuring system Causes of error How to minimize the error Error may occur in the measurement of various linear & angular measurements Human error may creep in during the tracing measurements Use of computerized plotters & digitizers to digitize the landmarks & carry out the various linear & angular measurements has proved to be more accurate
  • 136. Error : Errors in landmarks identification Causes of error How to minimize the error A) Quality of radiographic image Poor definition of radiographs may occur due to use of old films & intensifying screen although radiation dose is reduced Movement of object, tube or film may cause a motion blur Blurring of radiograph due to scattered radiation that fogs the film Recommended films should be used to avoid poor definition radiographs Stabilizing the object, tube, film. By increasing the current exposure time is reduced, minimizing motion blur Can be reduced by use of grids
  • 137. Error : Errors in landmarks identification Causes of error How to minimize the error B) Precision of landmark definition & reproducibility of landmark location May occur if landmark is not defined accurately, causes confusion in identification of landmark In general certain landmarks are difficult to identify such as porion Landmarks have to be accurately defined. Certain landmarks may require special conditions to identify which should be strictly followed Good quality radiography C) Operator bias Variations in landmarks identification between operators Advisable for the same person to identify & trace the patients
  • 138. Conclusion • There are numerable cephalometric analysis given by different people each expressing their ideas and ways to analyse, classify, and treat the face • All these analysis are still a two dimensional representation of the three dimensional structure • Each has inherent deficiencies associated with the analysis itself and those because of
  • 139. • The future of cephalometrics depends on the three dimensional analysis, their accuracy, validity and reproducibility • Still the value of the information and insight given by these traditional analyses should not be ignored or taken lightly
  • 140. References • Radiographic Cephalometrics – Alex Jacobson • Orthodontic Cephalometry – Athanasios E Athanasiou • Contemporary Orthodontics – William Proffit • Practice Of Orthodontics, Volume 1 & Volume 2 - J. A. Salzmann • Clinical Orthodontics, Volume 1 - Charles H Tweed • Orthodontics, The art & science – SI Balajhi