4. 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
5. Definitions
“The scientific measurement of the bones of the cranium
and face, utilizing a fixed, reproducible position for lateral
radiographic exposure of skull and facial bones” -- Moyers
“ A scientific study of the measurements of the head with
relation to specific reference points; used for evaluation of
facial growth and development, including soft tissue
profile” -- Grabers
8. 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
9. 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
10. 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
12. Lateral cephalogram
Also referred to as lateral
“cephs”
Taken with head in a
standardized reproducible
position at a specific distance
from X-ray source
13. Posteroanterior (p-a)
cephalometric radiograph
This provides an anteroposterior
view of the skull.
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
14. 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, Pr, pt B, Pog, Me etc
2. Constructed: constructed or obtained secondarily
from anatomic structures in the cephalogram eg– Gn,
Go, Ptm, S
15. 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
18. 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
19. • 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
21. 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
25. 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
26. Vertical planes
Facial plane
A-Pog line
Facial axis
E. plane (Esthetic plane)
Ptm
Gn
N
Pog
A
E plane
27. 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
28. 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
29. 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
30. 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
31. 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
32. 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
33. 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
34. 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
35. Incisor occlusal plane
angle
Average value = 14.5°, range =
3.5 to 20°
Increase in the angle is
suggestive of increased lower
incisor proclination
36. 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
37. Limitations of Downs analysis
Too many landmarks and measurements
Since the study was restricted to the age group of 12 to
17 years, it may not be very well applicable to the adults
Time consuming
The location of the occlusal plane can also be
subjected to variations, -- Jacobson
38. 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
39. 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°
40. 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°
41. A.N.B angle
Denotes relative position of
maxilla & mandible to each
other.Mean value is 2 °
> 2° –- class 2 skeletal
tendency
< 2°–- skeletal class 3
tendency
A
N
B
Mean value = 2°
42. 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°
43. Occlusal plane angle
Mean value = 14.5°
Indicates relation of
occlusal plane to the
cranium & face
Indicates growth pattern
of an individual
S
N
44. 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
45. 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
46. Inter-incisal angle
Mean value is 130-131 °
< 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°
47. 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 °
48. Lower incisor to N-B
(linear)
Helps in assessing lower
incisor inclination
Increase in
measurement indicates
proclined lower incisors
Normal value– 4mm
N
B
50. Limitations
The reference plane here is the S-N plane which can be
subjected to discrepancies due to the points
constructing the plane
Considering the nasion point, in many cases it may
deviate from its mid sagital plane due to asymmetry of
the nasal bones
The point A varies invariably due to the outline of the
alveolar bone extending from the central incisor
The point B, also varies considerably in its vertical
relationship to the apex of the central incisor.
51. 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
53. 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
54. 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)
55. Limitations
This analysis takes into consideration the occlusal
plane to determine the antero posterior relationship of
the jaws.
This plane can vary with malpositioning of the teeth.
This is not a disgnostic aid and is only useful to
understand the A-P jaw relationship when angle ANB
doesn’t provide a clear image.
56. 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
57. 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
58. This analysis employs somewhat less traditional
measurements & reference points
This analysis employs somewhat less traditional
measurements & reference points
A6 – upper molar – a point on the
occlusal plane located perpendicular
to the distal surface of the crown of
the upper first molar;
B6 – lower molar – a point on the
occlusal plane located perpendicular
to the distal surface of the crown of
the lower first molar;
C 1 – condyle – a point on the
condyle head in contact with and
tangent to the ramus plane;
DT – soft tissue – the point on the
anterior curve of the soft tissue chin
tangent to the esthetic plane or E-
line;
CC – center of cranium – the
point of intersection of the
Basion- Nasion plane and the
facial axis;
59. CF – point from planes at
Pterygoid - the point of
intersection of the Pterygoid
root vertical to the FH plane;
PT – PT point – the junction of
the pterygomaxillary fissure and
the foramen rotundum;
DC – condyle – the point in the
center of the condyle neck along
the Ba-N plane;
En – nose – a point on the soft
tissue nose tangent to the
esthetic plane or E-line;
60. Gn – Gnathion – a point at the
intersection of the facial and the
mandibular planes (cephalometric
Gn as opposed to anatomic Gn);
Go – Gonion – a point at the
intersection of the ramus and the
mandibular plane;
Pm – suprapogonion – the point at
which the shapes of the symphysis
changes from convex to concave; also
known as protuberance menti.
Pog – Pogonion – the point on the
bony symphysis tangent to the facial
plane;
Po – cephalometric Pogonion – the
intersection of the facial plane and
the corpus axis;
TI – TI point – the point of
intersection of the occlusal and the
facial plane;
62. Planes
Frankfurt horizontal --
Extends from porion to
orbitale
Facial plane -- Extends from
nasion to pogonion
Mandibular plane -- Extends
from cephalometric gonion to
cephalometric gnathion
63. Pterygoid vertical -- A
vertical line drawn
through the distal
radiographic outline
of the pterygomax
fissure &
perpendicular to FHP
Ba-Na plane --
Extends from basion
to the nasion. Divides
the face and cranium.
64. 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 of nose to
the soft tissue chin
point.
69. Chin in Space
This is determined by :
Facial axis angle
Facial (depth) angle
Mandibular plane angle
70. 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 axis angle
71. Facial (depth) angle
Changes with growth
Mean value is 87˚± 3˚
Indicates the horizontal
position of the chin &
therefore suggests
whether class II or class III
pattern is due to the
position of the mandible
Facial (depth) angle
72. 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
73. 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
High convexity – Class II pattern
Negative convexity – Class III
pattern
74. 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
75. 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
76. Lower incisor
inclinations
Angle between long axis of
lower incisors & the A-Pog
plane
On average this angle
should be 28 degrees
Measurement provides
some idea of lower incisor
procumbency
77. 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
78. 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
79. 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
80. Cant of upper lip
Line is drawn from nasion
perpendicular to upper lip
14 degree in females
8 degree in males
81. 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
82. Maxilla to mandible
Anteroposterior relationship
The midfacial length is determined by
measuring a line from Condylion (the
posterosuperior point on the outline of
mandibular condyle) to point A
The effective mandibular length is derived by
constructing a line from Condylion to anatomic
Gnathion
Linear relationship exists between effective
length of midface & that of mandible
83. Any given effective midfacial
length corresponds to effective
mandibular length within a
given range
84. To determine maxillomandibular difference midfacial
length measurement is subtracted from mandibular
length
Small individuals (mixed dentition stage) : 20-23mm
Medium-sized : 27-30mm
Large sized : 30-33mm
86. 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
If lower anterior facial height is
increased the mandible will appear
to be more Retrognathic. If lower
anterior facial height is decreased,
the mandible will appear to be more
prognathic.
87.
88. 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
89. 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
90. 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
91. 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
93. 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.
A width of 2mm or less in this
region may indicate airway
impairment
94. 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
positioning of the tongue
95. Limitations
McNamara based his studies on 3 previous studies by
Bolton, Burlington and Ann Arbour; all of which
represent considerable variations between them.
Those studies were restricted to specific populations
and may not be applicable in every sense to different
populations.
96. 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
measurement Dr. Reed Holdaway
-- Jacobson
97. 1. Facial Angle (90
degree)
Ideally the angle should
be 90 to 92 degrees
>90 degree: mandible
too protrusive
<90 degree: recessive
lower jaw
98. 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
99. 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
Dictates dental relationships
needed to produce facial
harmony
100. 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 do not
approximate, facial
imbalance may be evident
101. 5. Nose tip to H-line
(12mm maximum)
Measurement should not
exceed 12mm in
individuals 14 yrs of age
6. Upper sulcus depth to
H line (5mm)
Short/thin lips -
measurement of 3 mm
may be adequate
Longer/thicker lips-
7mm may still indicate
excellent balance
102. 7.Upper lip thickness
(15mm)
Measured horizontally
from a point on outer
alveolar plate 2mm below
point A to outer border of
upper lip
103. 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)
Measurement less than
upper lip thickness – lips are
considered to be strained
104. 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
10. Lower sulcus depth to H
line (5mm)
105. 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 facial
harmony
106. Limitations
Takes into consideration soft tissue balance and
harmony. As with any other soft tissue landmarks,
identification is not very easy
The tonicity and muscular tensions cannot be assessed
easily.
107. Serial cephalogram
SERIAL CEPHALOGRAM OR CEPHALOMETRIC
SUPERIMPOSITION IS AN ANALYSIS OF LATERAL
CEPHALOGRAMS OF THE SAME PATIENT TAKEN AT
DIFFERENT TIMES
CEPHALOMETRIC SUPER IMPOSITIONS INVOLVE THE
EVALUATION OF:
♦ Changes in the overall face
♦ Changes in the maxilla and its dentition
♦ Changes in the mandible and its dentition
♦ Amount and direction of condylar growth
♦ Mandibular rotation
108. TO PERFORM ACCURATE SUPER
IMPOSITION
o Consecutive cepholograms should be taken under identical
condition of magnification head position, and radiological
exposure
o The tracing of the superimpositions must be accurate
o It is of great importance that exactly the same structures
and their corresponding radiographic shadows be traced in
the consecutive cepholograms
o One should have the thorough knowledge of anatomy of
dentofacial & cranial structures as well as radiographic
interpretation
o They have to be registered on stable reference areas in the
face.
109. Colour coding for tracing:
In order to facilitate identification of consecutive
cephalograms the following colour code has been
suggested by the American Board of Orthodontists
(1990)
Pretreatment – Black
Progress- Blue
End of treatment- Green
110. SUPERIMPOSITION OF THE
MAXILLA
Evaluates
1. Movement of maxillary teeth
2. Rotation of maxilla
Two method for superimposing the maxillary structutres
are recommended- the structural method and a modified
best fit method.
Structural Method : - Suggested by Bjork & Skieller in 1976
is recommended if the details of the zygomatic process of
the maxilla are clearly identified in both cephalograms.
Modified best fit method : - If the details of zygomatic
process of maxilla are not identified in both cephalograms.
111. Structural method of superimposition of maxilla
On each cephologram, trace the contours
of palate, maxillary 1st molar, central
incisors, zygomatic process of maxilla,
floor of the orbit N-S line and the
construction line.
Modified best fit method
On each cephologram trace the outline of
the palate, 1st permanent molars and
central incisors. Following structures are in
a best fit alignment. Contour of the oral
part of the palate and Contour of the nasal
floor
112. MANDIBULAR SUPERIMPOSITIONS
Evaluates
Movement of the mandibular teeth
Mandibular rotation
Amount & direction of condylar growth
Stable structures for superimposition on the mandible:
According to Bjork and Skieller (1983).
o The anterior contour of the chin .
The inner contour of the cortical plates at the inferior border of the
symphysis.
Posteriorly, the contours of the mandibular canal .
Lower contour of a mineralized molar germ before root formation.
113. Evaluation of the overall changes in
the face
Nelson’s (1960) and Melsen (1974) identified certain
stable structures for superimposition.
1. The anterior wall of sella turcica;
2. The contour of the cribiform plate of the ethmoid
bone (lamina cribrosa);
3. Details in the trabecular system in the ethmoid cells;
4. The median border of the orbital roof; and
5. The plane of the sphenoid bone (planum
sphenoidale)
114. Ten angle analysis
The search for a simpler cephalometric analysis for
dentists who have an occasional need for their practices
and for students beginning the study of cephalometrics led
to the development of 10-angle analysis.
The basic ten angles are selected from Steiner ,Downs and
Tweeds analysis.
116. 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
117. 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
118. 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
119. 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
120. 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
121. 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 radiological errors
and clinician’s experience
122. 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
123. 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
Editor's Notes
Glabella (G) - the most prominent anterior point in the midsagittal plane of the forehead.
Nasion (N) – the most anterior point of the nasofrontal suture in the median plane.
Sella (S) – the midpoint of the hypophysial fossa.
Orbitale (Or) – lowermost point of the orbit in the radiograph.
Anterior nasal spine (ANS) – the tip of the bony anterior nasal spine, in the median plane.
Posterior nasal spine (PNS) – 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.
Articulare (Ar) – the point of intersection of the posterior margin of the ascending ramus and the outer margin of the cranial base.
Point A (A) – the deepest midline point in the curved bony outline from the base to the alveolar process of the maxilla.
Point B (B) – most posterior point in the outer contour of the mandibular alveolar process
Pogonion (Pog) – most anterior point of the bony chin,
Gnathion (Gn) – most anterior and inferior point of the bony chin.
Gonion (Go) – the intersection of the lines tangent to the posterior margin of the ascending ramus and the mandibular base.
Menton (Me) – the lower most point of the mandible
Porion (po)- Most superior point of outline of external auditory meatus
Basion (ba) -Most anterior point on foramen magnum
soft tissue nasion (N′)Point on soft tissue over nasion
Subnasale (Sn) - the point at which the nasal septum merges with the upper cutaneous lip in the midsagittal plane.
Labrale Superius (Ls) -a point indicating the mucocutaneous border of upper lip.
Stomion superius (Stms) - the lowermost point on the vermillion border of upper lip.
Stomion inferius (Stmi) - the uppermost point on the vermillion border of the lower lip.
Labralae inferius (Li) - a point indicating the mucocutaneous border of the lower lip.
Mentolabial sulcus (Si) - the point of greatest concavity in the midline between the lower lip and chin.
Soft tissue pogonion (Pg’) - the most anterior point on the soft tissue chin.
Soft tissue gnathion (Gn’) - the constructed midpoint b/w soft tissue pogonion and soft tissue menton.
Soft tissue menton (Me’) - lowest point on the contour of the soft tissue chin.
Line drawn from porion to orbitale
Line drawn from sella to nasion
Basion nasion plane – line drawn from basion to nasion
Palatal plane – line drawn from anterior nasal spine to posterior nasal spine
Occlusal plane –line drawn through overlapping cusp of molars and central incisor
Facial plane- it extends from nasion to pogonion
A- pog plane – extends from point A to pogonion
Facial axis – ptm point to gnathion
E. Plane – tangent drawn from tip of the chin to tip of the nose
Angle formed by the intersection of nasion pogonion plane and FH plane
Angle formed by the intersection of line from nasion to Point A and line from point A to pogonion.
The angle is formed between a line from point A and point B and a line joining nasion to pogonion .
Angle formed by the intersection of the mandibular plane with Fh plane.
Angle formed by joining sella-gnathion line with the FH plane.
Angle formed between Occlusal plane and FH plane.
Angle formed between long axis of upper and lower incisors.
Angle formed between long axis of lower central incisor and occlusal plane
This is linear measurement between the incisal edge of the maxillary central incisor and the line joining Point A to pogonion.
Angle formed by the intersection of SN plane and a line joining Nasion to Point A.
Angle formed between the SN plane and a line joining nasion to point B.
Angle formed by the intersection of lines joining nasion to point A and nasion to point B .
Angle formed between SN plane and the mandibular plane.
Angle formed between the occlusal plane and the SN plane .
Angle formed by the intersection of long axis of the upper central incisors and the line joining nasion to point A.
It is the linear measurement between the labial surface of the upper central incisor and the line joining nasion to point A.
Angle formed between the long axis of the upper and lower central incisors.
Angle formed between the N-B plane and the long axis of the lower incisor.
Linear distance between the labial surface of lower central incisor and line joining nasion to point B.
the lips in well balanced faces, should touch a line extending from the soft tissue contour of the chin to the middle of an “S” formed by the lower border of the nose. This line is referred to as the “S-line”.
Lips located beyond this line tend to be protrusive.
If
the lips are positioned behind this line, it is generally
interpreted that the patient possesses a “concave’ profile.
A functional occlusal plane is drawn and perpendiculars are drawn to the occlusal plane from points A and B .
The procedure is as follows
Locate FH and draw PtV plane perpendicular to FH plane.
Construct 4 planes tangent to points R-1, R-2, R-3, and R-4 on the borders of the ramus.
R-1 – Deepest point on the anterior border of the ramus and located half away between the superior and inferior curves.
R-2 - Located on the posterior border of the ramus opposite R1.
R-3 – Deepest point on the sigmoid notch, and halfway between the anterior and posterior curves.
R-4 – Opposite R3 on the inferior border of the mandible.
The constructed planes form a rectangle enclosing the ramus.
Xi point is located in the center of the rectangle at the intersection of the diagonals.
a line extending from the point Pt to Gnathion (PT to Gn).
extends from DC to Xi point; used to describe the morphologic features of the mandible.
extends from Xi to PM(supra pogonion) ; used to describe the morphology of the mandible to evaluate dentition changes.
The angle formed between Basion – Nasion plane and the plane from point Pt to Gnathion.
: The angle between the facial plane (N –Pog) and the FH plane
Angle formed between mandibular plane and FH plane .
Drawing a line tangent to the base of the nose and a line tangent to the upper lip forms the nasiolabial angle
Linear distance is measured between N perpendicular and point A.
is the angle between anatomic Frankfort horizontal and the line drawn along the lower border of mandible
Angle formed between line constructed from basion to nasion and pterygomaxillary fissure to gnathion.
The relationship of mandible to the cranial base is determined by measuring the distance from Pogonion to N perpendicular.
Distance measured from point a to facial surface of lower incisor
Angular measurement from line drawn through soft tissue nasion to soft tissue pogonion and FH plane