Lateral cephalometric analysis of hard tissues

Lateral Cephalometric
Analysis of Hard Tissue
Presented by :Malik Ashim Showkat
Bds final year
guided by : Dr.Hiten kalra
1

Contents
Introduction and definition
Development of cephalometric
analysis
Requirements of cephalometric
analysis
Overview of cephalometric
landmarks
Overview of cephalometric
planes
Classification of analysis
Downs analysis
Steiner’s analysis
Tweed analysis
Rickett’s analysis
Burstone analysis
Rakosi’s analysis
McNamara analysis
Bjork analysis
2

Introduction
• The introduction of radiographic cephalometrics in 1934 by Hofrath in
Germany and Broadbent in the United States provided a research as
well as clinical tool for the study of malocclusion and underlying
skeletal disproportions.
• The original purpose of cephalometrics was research on growth
patterns in the craniofacial complex which led to the derivation of
concepts of normal development.
• Cephalometric radiographs could be used to evaluate dentofacial
proportions and clarify the anatomic basis of malocclusion.
3

Definition of cephalometric analysis
• A collection of numbers intended to compress much of the
information from the cephalogram into a usable form for diagnosis,
treatment planning , and/or assessment of treatment effects.
• Perhaps the most important clinical use of radiographic
cephalometrics is in recognising and evaluating changes brought
about by orthodontic treatment.
• For diagnostic purposes, the major use of radiographic
cephalometrics is in characterising the patient’s dental and skeletal
relationships.
4

Development of cephalometric analysis
• Cephalometric analysis is commonly carried out, not on the
radiograph itself, but on a tracing or digital model that emphasises
the relationship of selected points.
• Cephalometric landmarks are represented as a series of points, which
are usually defined as locations on a physical structure(for e.g.. The
most anterior point on the bony chin), or occasionally constructed
points such as the intersection of two planes(for e.g.. The intersection
of the mandibular plane and a plane along the posterior margin of
the ramus).
5

Requirements of cephalometric analysis
• Use reference points that are clearly defined and easy to locate.
• Rely on more than one bone reference plane since these planes are
themselves variable.
• Consider natural head position because resulting values often reflect
the actual appearance of the patient
• Be clearly structured in skeletal and dentoalveloar assessments and
always distinguish between the different planes(sagittal, vertical,
transverse)
• Include as few measurements as possible, so that an optimal
overview is maintained at any time.
6

• Include graphical representation, which is useful for immediate
understanding and which enhances communication with non-
orthodontic colleagues and patients.
• Be structured so that it can be changed without difficulty when better
insight requires an adaptation.
7

Overview of cephalometric landmarks
8

Overview of cephalometric planes
9

Classification of analysis
Basic method of classification:
A) Methodological: basic units of classification are angles and distances
in mm.
Angular analysis:
Dimensional analysis: considers various angles in isolation comparing
them to standard norms. Eg. Down’s analysis
Proportional analysis: based on comparison of the various angles to
establish relation between the separate parts of the facial skeleton
.e.g.: Koski’s analysis
10

Analysis to determine position –angular measurements can also be
used to determine position of parts of facial skeleton. Eg. SNA and
SNB angles give relation between maxillary and mandibular bases and
the cranial base.
11

Linear analysis
Orthogonal analyses –a reference plane is established with various
reference points projected onto it perpendicularly after which distances
between the projections are measured.
Total orthogonal analysis:
a)Geometrical eg. De coster
b)Arithmetical: reference points projected onto horizontal and vertical
planes and distances between them measured. Eg. Cobens
Partial orthogonal analysis: involves assessment of only part of skull.
Archial analysis: which reference points are not projected perpendicularly ,
but by drawing arcs with the help of compass. eg: Sassouni analysis
12

 Dimensional linear analyses
- Direct method which gives distance between two reference lines eg.
Length of mandibular base
- Projected method which determines distance between certain
reference pts that have been projected onto a reference plane.
 Proportional linear analyses: based on relative rather than absolute
values, measurements compared to each other than to norms
13

B) Normative classification: according to concepts on which norms have
been based on
 Mononormative analyses- averages are norms
Arithmetical norms: figures based on angular, linear , and proportional
measurements.
Geometrical norms: average tracings on a transparent sheet assessment
consists of comparing these with the case under analysis .
Multinormative analyses: whole series of norms are used including age &
sex.
Correlative analyses- to asses individual variations of facial structures ,to
establish their mutual relationship
14

C)According to area of analyses:
Dento-skeletal analyses : analyze teeth and skeletal structures .
Soft tissue analyses : may involve whole profile or certain structures
 Functional analyses: functional relations such as occlusion to
interocclusal space relationship
15

List of cephalometric analysis
1. Downs analysis
2. Steiner’s analysis
3. Tweed analysis
4. Rickett’s analysis
5. Burstone analysis
6. Rakosi’s analysis
7. McNamara analysis
8. Bjork analysis
16

INTRODUCTION
• Given by WB Downs.
• When observing facial profiles, W.B. Downs noted that generally the
position of the mandible could be used to determine whether a face
was ‘balanced’.
• He recognized that facial profiles could be retrusive or protrusive, yet
still be harmonious in proportion.
• Since the Frankfort horizontal plane(FH) approximates a level position
when an individual stands in a posture of distant vision, Downs
elected to use this plane as a reference base from which to determine
the degree of Retrognathism, orthognathism, or Prognathism.
18

• Downs reduced his observation to four basic facial types:
 Retrognathic, a recessive mandible
Orthognathic, an ideal or average mandible
Prognathic, a protrusive mandible
True Prognathism, a pronounced protrusion of the lower face.
• Any or all of the above could possess a normal occlusion and
harmonious facial profile in form and position.
19

Orthognathic Retrognathic
Prognathic True
prognathism
20

Downs normal ranges
• The control material was derived from 20 white subjects ranging in 12
to 17 years, with an equal number of boys and girls.
• Dental casts, models, photographs, and cephalometric and intraoral
radiographs were taken of each.
• All individuals possessed clinically excellent occlusions.
21

• Skeletal pattern
Facial angle
Angle of convexity
A-B plane
Mandibular plane angle
Y growth axis
• Dental pattern
Cant of occlusal plane
Interincisal angle
Incisor-OP angle
Incisor-MP angle
Protrusion of maxillary incisors
22

o Skeletal pattern:
• FACIAL ANGLE :
 Used to measure the degree of
retrusion or protrusion of the mandible.
 The mean reading of this angle is 87.8
degree, with a range of 82 to 95
degrees.
 A prominent chin increases this angle,
whereas a smaller than average angular
reading suggests a retrusive chin.
23

• ANGLE OF CONVEXITY
 This angle measures the degree of the
maxillary basal arch at its anterior limit(point
A) relative to total facial profile.
 This angle is read in positive or negative
degrees from zero. If the line pog- point A is
extended, and located anterior to the NA
line, the angle is read as positive.
 A positive angle suggests prominence of the
maxillary dental base relative to the
mandible. A negative angle is associated
with a prognathic profile.
 The range extends from a minimum of -8.5
degrees to a maximum of 10 degrees, with a
mean reading of 0 degrees.
24

• A-B plane
The A-B plane is a measure of the relation of
the anterior limit of the apical bases to each
other relative to the facial line.
It represents an estimate of the difficulty in
obtaining the correct axial inclination and
incisor relationship when using orthodontic
therapy
The readings extend from a maximum of 0
degrees to a minimum of –9 degrees, with a
mean reading of -4.6 degrees.
25

• Mandibular plane
angle
 The mandibular plane, according to Downs,
is tangent to the gonial angle and the lowest
point of the symphysis. The MP angle is
established by relating the MP to the FH.
 High MP angles can occur in both retrusive
and protrusive faces and are suggestive of
unfavourable hyper divergent facial patterns.
 The range of readings extend from a
minimum of 17 degrees to a maximum of 28
degrees, with a mean reading of 21.9
degrees.
26

• Y-(growth) axis
 It is measured as the acute angle formed by the
intersection of a line from the sella tursica to
gnathion with the FH.
 The y axis indicates the degree of the forward,
downward and rearward position of the chin in
relation to the upper face.
 The range extends from a minimum of 53
degrees to a maximum of 66 degrees, with a
mean reading of 59.4 degrees.
 A decrease of y-axis angle indicates a greater
horizontal than vertical growth of the face or a
deepening of bite in orthodontic cases.
 An increase in y-axis is suggestive of vertical
growth or an opening of the bite during
orthodontic treatment. The y-axis reading also
increases with extrusion of the molars.
27

o DENTAL PATTERN
Cant of occlusal
plane
The cant of the OP is a measure of the
slope of the OP to the FH.
A parallel relationship of the planes would
provide a 0 degree reading. When the
anterior part of the plane is lower than the
posterior, the angle would be positive.
The minimum angular measurement is 1.5
degrees; the maximum is 14 degrees and
the mean 9.3 degrees.
Larger positive angles are found in class II
facial patterns. Long rami tend to decrease
this angle.
28

• Interincisal angle
It is established by passing a line through
the incisal edge and the apex of the root
of the maxillary and mandibular central
incisors.
This angle is relatively small in
individuals whose incisors are tipped
forward on the dental base.
The minimum angular reading is 130
degrees, the maximum 150.5 degrees
and mean 135.4 degrees.
29

• Incisor-OP angle
It relates the mandibular incisors to
their functioning surface at the OP.
The inferior inside angle is read as a
positive or negative deviation from a
right angle. The positive angle increases
as these teeth incline forward.
The minimum angle is 3.5 degrees, the
maximum 20 degrees and mean is 14.5
degrees.
The positive angle increases as these
teeth incline forward or proclined. The
values are least in class II div.2 cases
where the incisors are retroclined.
30

• Incisor-MP angle
It is formed by an intersection of the
MP with a line passing through the
incisal edge and the apex of the root
of the mandibular central incisor.
This angle is positive when the
incisors are tipped forward on the
dental base.
The minimum angular reading is -8.5
degree, maximum 7 degree and
mean 1.4 degrees.
31

• Protrusion of the
maxillary incisors
 It is measured as the distance between the
incisal edge of the maxillary central incisors to
the line from point A to Pog.
 This distance is positive if the incisal edge is
ahead of the point A-Pog line and indicates the
amount of maxillary dental protrusion.
 The reading is negative if the incisal edge lies
behind the point A-Pog line and suggests a
retruded position of the maxillary incisors.
 The minimum reading is -1mm, the maximum
5mm and mean 2.7mm.
32

Cephalometric polygon
• Because of the difficulty in developing a suitable mental picture of a
sizeable table of figures, Vorhies and Adams(1951) developed a
polygon or wiggle to express a large group of cephalometric readings
graphically.
• For this, they used the maximum and minimum figures(range) of each
of Downs measurements and plotted these figures on both sides of
the vertical mean,
• This produced a zigzag pattern.
• The polygon was further subdivided into two polygons: the skeletal
polygon was on top of the paper and dental polygon on the lower half
of the paper.
33

• The vertical arrows represent the average normal, and the solid lines
of the polygon represent the extremes of the range.
• The quantitative value of each horizontal marking is 1 degree or 1mm.
• The polygon is an effective method of quantitatively and qualitatively
illustrating a static cephalometric analysis.
• It enables clinicians to rapidly assimilate the collected data and also
serves as a great aid in case presentation as a graphic description is
generally more comprehensive and impressive than a verbal
description.
34

INTRODUCTION
• Cecil C. Steiner in 1953, selected what he considered to be the most
meaningful parameters and developed a composite analysis, which he
believed would provide the maximum clinical information with the
fewest number of measurements.
• Steiner proposed the appraisal of various parts of the skull, namely
the skeleton, dentition and soft tissues.
• By comparing the traced readings or measurements of patients with
malocclusions to those of “normal” occlusion, the degree of deviation
from the normal could be determined.
37

• The skeletal analysis entails relating the mandible and the maxilla to
the skull and to each other.
• The dental analysis involves relating the maxillary and mandibular
incisors to their respective jaws and to each other.
• Finally the soft tissue analysis provides a means of assessing the
balance and harmony of the lower facial profile.
38

Three way analysis
• Skeletal analysis
Maxilla (SNA)
Mandible (SNB)
Maxilla mandible relationship
(ANB)
Occlusal plane
Mandibular plane
• Dental analysis
Maxillary incisor position
Mandibular incisor position
Interincisal angle
Lower incisor-chin relationship
• Soft tissue analysis
39

Skeletal analysis
• The lateral cephalometric head film is traced, and the traditional
landmarks and planes are identified.
40

 S.N.A angle
 Determines whether the maxilla is
positioned anteriorly or posteriorly to the
cranial base.
 The mean SNA reading is 82 degrees.
 If angular reading is greater than 82
degrees, it would indicate a relative forward
positioning of the maxilla.
 If the reading is less than 82 degrees, it
would indicate a relative backward or
recessive location of the maxilla.
41

 S.N.B angle
To determine whether the mandible is
protrusive or recessive relative to the
cranial base, the SNB angle is read.
The mean reading is 80 degrees.
An angle less than 80 indicates a
recessive mandible. An angle greater
than 80 degrees suggests a prognathic
mandible.
42

 A.N.B angle
Provides information on the position
of the jaws relative to each other.
The mean reading for this angle is 2
degrees, a reading greater than 2
degree indicates a class II skeletal
tendency.
Angles less than 2 degrees and
readings less than zero indicate that
the mandible is located ahead of the
maxilla, suggesting a class III
relationship.
43

 Occlusal plane
The occlusal plane is drawn through
the region of the overlapping cusps of
the first premolars and the molars.
The angle of the occlusal plane to Sn is
measured.
The mean reading for normal
occlusions is 14 degrees.
 The angle is increased in long face or
vertically growing individuals and also
skeletal open bite cases. It may be
decreased in horizontal growers or
cases with skeletal deep bite.
44

 Mandibular plane
 It is drawn between the gonion and gnathion.
 The mandibular plane angle is formed by relating it to
the anterior cranial base.
 The mean reading is 32 degrees.
 Excessively high or low mandibular plane angles
suggest unfavourable growth patterns in individuals.
 Such patterns may affect the outcome of the
treatment and it is wise to anticipate such problems if
they occur.
45

DENTAL ANALYSIS
Maxillary incisor position
The relative location and axial inclination of the maxillary
incisors are determined by relating the teeth to the line
from nasion to point A.
Normal value is 22 degree.
The maxillary incisor to NA reading in degrees indicates
the relative angular relationship of maxillary incisors,
whereas the reading in millimetres provides information
on the forward or backward positioning of the incisors
relative to the NA line.
Normal value is 4mm.
46

 Mandibular incisor position
It is determined by relating the teeth to the line
from nasion to point B.
The mandibular incisor to NB measurement in
millimetres shows the forward or backward
positioning of the teeth relative to the NB line.
The most labial portion of the crown should be
located 4mm ahead of the NB line, whereas the
axial inclination of the tooth to this line should be
25 degrees.
47

 Interincisal angle
 It relates the relative position of the
maxillary incisor to that of the
mandibular incisor.
 If the angle is more acute or less than
the mean of 130 degrees, the maxillary
or mandibular teeth or both require up
righting.
 If angulation is more acute or less than
130 degree, then the anterior are
considered to be proclined. Conversely,
if the angle is greater than 130 degree or
more obtuse the incisors are considered
to be retroclined.
48

 Lower incisor-chin
relationship
 Since the chin contributes generously to the
facial outline, this area must be evaluated.
 The degree of prominence of the chin
contributes to the determination of the
placement of the teeth in the arch.
 The distance between the labial surface of the
lower incisor to the NB line should be equal
(4mm).
 A 2mm discrepancy is acceptable, 3mm less
desirable but more than 4mm indicates for
corrective measures.
49

SOFT TISSUE ANALYSIS
 It is basically a graphic record of the visual observations made in the clinical examination of
the patient.
 The soft tissue analysis includes an appraisal of the adaptation of the soft tissues to the bony
profile with consideration to the size, shape and posture of the lips as seen on the lateral
head film.
 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 is called as S line.
 Orthodontic correction usually entails advancing the teeth in the dental arches to build up the
lips to approximate the S line.
50

Steiner’s S line: a) lips in balance at rest. B) lips too protrusive C) lips or lower facial profile too recessive
51

Steiner's chevron
• Whereas the ideal ANB relationship of maxilla to mandible as
described by points A and B is 2degree, the chevrons describe
anticipated axial inclinations of the maxillary and mandibular
incisors to the NA and NB lines at various ANB relationships.
52

Steiner analysis chevrons with acceptable compromises. In all the chevrons, the top number in
degrees represents the ANB angle, followed by the angle of the maxillary central incisor to the NA line
and the distance in mm from the most labial profile surface of the maxillary central incisor to NA line,
and likewise for the inclination of the mandibular incisor and its distance from the labial profile
surface to the NB line.
53

INTRODUCTION
• Tweed devoted his professional career to the study of anterior limits
of the dentition.
• Used in concert with other cephalometric measurements, the
diagnostic triangle provides valuable information about a skeletal
pattern for diagnosis and treatment planning.
• The triangle is as appropriate for use today as it was when Tweed
presented it many years ago.
55

• Tweed developed this analysis as an aid to treatment planning,
anchorage preparation and determining the prognosis of orthodontic
cases.
• At that time a great emphasis was laid on the placement of the
mandibular incisors for the preservation of the orthodontically
achieved results.
• This analysis is based primarily on the deflection of the mandibular
plane angle (FMA) and the posture of the lower incisor.
56

• The analysis is done to determine the final position the lower incisor
should occupy at the end of treatment.
• Once the final position of these teeth has been determined, the space
requirements could be calculated and decisions regarding extractions
can be made.
• Dr. Tweed established that prognosis could be predicted relatively
accurately based on the configuration of the triangle.
57

Objectives:
To determine the final position of lower incisors should occupy at the
end of treatment so space requirement is calculated and decision
regarding extraction is made.
As an aid in treatment planning and anchorage preparation.
Determining the prognosis of orthodontically treated cases.
58

The analysis consist of the Tweed’s triangle formed by:
1. Frankfort horizontal plane
2. The mandibular plane
3. The long axis of lower incisor
The three angles formed are:
1. Frankfort-mandibular plane (FMPA).
2. Lower incisor to mandibular plane (IMPA).
3. Lower incisor to FH plane (FMIA).
59

The diagnostic facial triangle
• Tweed’s diagnostic triangle is composed of the Frankfort-mandibular
plane angle(FMA), the Frankfort-mandibular incisor angle(FMIA), and
the incisor mandibular plane angle(IMPA).
• The interrelationship of these three cephalometric angles gives
information about the patient’s vertical skeletal pattern, the
relationship of the mandibular incisors to the basal bone, and the
relative amount of protrusion or lack thereof, of the face.
• If the skeletal pattern has a normal vertical dimension, these
measurements will coincide closely with a pleasing facial profile.
60

A normal diagnostic facial triangle corresponds with a pleasing facial profile
61

• Frankfort-mandibular incisor angle
Tweed believed that the FMIA value indicated the degree of balance
and harmony between the lower face and the anterior limit of the
dentition.
He found that patients who exhibited pleasing facial aesthetics had
an FMIA of 62-60 degrees.
When FMA is 21 to 29 degrees, FMIA should be 68 degrees.
When FMA is 30 degrees or greater, FMIA should be 65 degrees.
When FMA is 20 degrees or less, IMPA should not exceed 92 degrees.
62

• Frankfort-mandibular plane angle
The significance of the FMA in this analysis is that it indicates the
direction of lower facial growth, both horizontally and vertically.
Normal range for this angle is 22 to 28 degrees.
An FMA above 30 degrees suggests greater vertical growth, whereas
an FMA below the normal range indicates less vertical growth.
This angle is an excellent barometer of vertical control during
mechanotherapy and therefore should be carefully monitored during
treatment.
63

• Incisor-mandibular plane angle
It establishes the position of the mandibular incisors in relation to the
mandibular plane.
It is used as a guide in maintaining or positioning the mandibular
incisor teeth in relation to the underlying basal bone.
The standard IMPA angle of 87 degrees indicates that the upright
position of the mandibular incisor is normal, suggesting balance and
harmony of the lower facial profile.
64

The basis is the FMA angle, and the following can be derived from the
change in its value as:
1. FMA 16 to 28: good prognosis.
• at 16, IMPA should be 95
• Approximately 60 percent of malocclusions have FMA between 16 and 28
2. FMA from 28 to 35: prognosis fair at 28, IMPA should be 85 extractions necessary in majority of
cases at 35, IMPA should be 80 to 85.
3. FMA above 35, prognosis bad, extractions frequently complicate problems. Tweeds stressed the
importance of the FMIA angle, recommending that it be maintained at 65 to 70.
65

Classification of growth trends
• A lateral cephalogram should be included in the records of all young
patients undergoing a pre orthodontic guidance program.
• Some 12 to 18 months later, a second head plate should be taken and
tracings made of both cephalogram.
• These tracings are superimposed on S-N with S as the reference point.
• The face of all children grow downward and forward in one of the
three ways. Therefore, facial growth trends may be classified as
Type A, Type B and Type C. each type having a subdivision.
66

TYPE A :-
Maxilla & mandible show forward & downward growth
ANB angle remains the same
Prognosis is good
If case is class I with ANB angle that does not exceed 4.5, Treatment is not indicated until the
full eruption of all four cuspid teeth
TYPE A Subdivision:-
If Molar relationship class II with ANB greater than 4.5 degrees.
Restrain maxillary growth with Kloehn cervical headgear .
This continues till Class II molar relationship is corrected or until all four permanent cuspid
teeth have fully erupted
 ANB relation is unchanged as mandibular incisors remain stable and free from crowding as
both dentures bases are growing forward in unison
Prognosis is good.
Treatment completed in 15 to 21 months.
67

TYBE B :-
 Maxilla & mandible grow downward & forward with maxilla growing more
rapidly than mandible.
 When ANB angle is 4.5 degree or less prognosis is favorable
 if the ANB ranges from 7- 12 degree , prognosis is poor
Extraction of all four first premolars is mandatory for patients with high ANB
angles.
Enormous posterior movement of the maxillary incisors .
 If treatment is concluded prior to completion of the growth processes, it is
advisable to use the Kloehn cervical gear following active treatment.
Treatment time 36 to 42 months
TYBE B Subdivision :-
ANB is large & found to be increasing
Undesirable growth trend, treatment long & difficult
69

TYPE C :-
 Maxilla & mandible grow downward & forward with mandible growing
more than maxilla with decreasing ANB
 Growth is favorable & treatment is facilitated by growth
Prognosis excellent
Mandibular incisor lingual tipping or maxillary incisor labial flaring can
occur
when the FMA ranges upward from 20 degree , growth is equal in the
vertical and horizontal dimensions ,and When the FMA is 20 or less growth
is predominantly horizontal
Treatment time 10 to 15 months
TYPE C Subdivision :-
• regardless of the size of the FMA, when growth is virtually confined to the
horizontal dimensions, with little vertical growth.
71

Tweed summarized his philosophy on which his appliance
therapy is based:-
 Normal occlusion is best maintained with the mandibular
incisors in their normal axial inclination when related to the F-H
plane approx. 65°(FMIA)
 The ultimate balance & harmony of facial esthetics is achieved
only when the mandibular incisors are positioned over the basal
bone
The normal relationship of the mandibular incisors to their
basal bone is the most reliable guide in diagnosis & treatment
of class I ,class II & bimaxillary protrusion cases and also in
attainment of balance & harmony of facial profile &
permanence of tooth position.
73

Tweed-Merrifield Diagnostic Analysis System
• The diagnostic facial triangle developed by Tweed is the foundation of
the Tweed-Merrifield Diagnostic Analysis System.
• Other cephalometric values that reflect anteroposterior relations,
vertical relations and soft tissue overlay must be used along with the
diagnostic facial triangle.
• Three factors influences the facial balance
 the position of teeth
 the skeletal pattern
 the soft tissue thickness
74

Sella-nasion-point A
(SNA)
 This angular value offers
guidance for determining the
relative anteroposterior position
of the maxilla relative to he
cranial base.
 A range of 80 to 84 degrees near
the end of growth and
development is considered
normal.
75

Sella-nasion-point B
(SNB)
 This value expresses the
horizontal relationship of the
mandible to the cranial base.
 A range of 78 to 82 degrees
indicated normal anteroposterior
mandibular position.
 A value of less than 74 deg
indicates that orthognathic
surgery would be a valuable
adjunct to treatment.
76

Point A-nasion-Point B
(ANB)
 This expresses a direct
anteroposterior relationship of the
maxilla to the mandible.
 The normal range is 1 to 5 degrees.
 As the class II malocclusion becomes
progressively difficult, the ANB value
increases.
 An ANB value greater than 10
degrees indicates that surgery
should be considered as possible
adjunct to treatment.
 A negative ANB value is more
indicative of horizontal facial
disproportion.
77

Point A/point B to
occlusal plane (AO-BO)
 This verifies the anteroposterior
relationship of the maxilla to the
mandible and is measured along the
occlusal plane
 Treatment becomes difficult if the
value is beyond the normal range of
0 to 4mm.
 AO-BO is affected by the steepness
or flatness of the occlusal plane
since the measurement is made
between perpendicular from point A
and point B to occlusal plane.
78

Occlusal plane(OP)
 This is a dentoskeletal relationship
value of the OP to the FH plane
 A normal range of 8 to 12 degrees
varies by about 2 degrees in male
and female patients.
 Values above and below the normal
range indicate difficulty in treatment
 The OP generally tends to return to
its original position following
treatment, resulting in an
unfavourable interdental relationship
if this plane was tipped during
corrective treatment.
79

Z angle
 The chin lip profile line related to FH
has an normal angular range of 70 to
80 degrees.
 The Z angle gives a guidance relative
to anterior tooth positioning as it
reflects the combined values of FMA,
FMIA, IMPA and soft tissue thickness.
 Tooth position can be subsequently
altered to favourably influence facial
balance.
80

Upper lip thickness
(UL)
 The upper lip influences the Z
angle.
 The upper lip usually thins with
maturation but thickens with
maxillary incisor retraction .
 Approximately 1mm of
thickening occurs with each 4mm
of incisor retraction.
81

Total chin thickness
(TC)
 The bony chin and its soft tissue
overlay at the pogonion greatly
influence the soft tissue profile and
the Z angle.
 The thickness of the soft tissue chin
should be equal to the UL.
 If this is not 1:1 ratio, the
orthodontist should compensate by
incisor positioning.
 A deficient total chin or excessive
value for total chin will be reflected
in the Z angle and will increase
difficulty of treatment management.
82

Posterior facial height
(PFH)
 It is a millimetre measurement of
ramus height measured from
articulare, tangent to the ascending
ramus.
 This vertical value is important in
cranial analysis.
 It influences facial form, both
vertically and horizontally
 Increase in PFH is essential for
counter clockwise or closing
movement of the mandible.
 Its relationship to the anterior facial
height determines the FMA angle
and lower facial proportion.
83

Anterior facial height
(AFH)
 It is a millimetre measurement that
is measured from the palatal plane
to menton.
 A value of about 65mm for a 12 year
old suggest that AFH is normal.
 This vertical measurement requires
careful monitoring if it exceeds or is
less than 5mm from normal value.
 In class II malocclusion it is essential
to limit the increase in AFH by
controlling maxillary and mandibular
molar extrusion using an intrusive
force on the anterior segment of the
maxilla.
84

INTRODUCTION
• Robert Ricketts, one of the pioneers of Orthodontics has contributed
greatly to the understanding of clinical Cephalometrics.
• He believed that cephalometric analysis was one of the most valuable
tools available for diagnosing and monitoring patients, as well as
evaluating their growth and development.
• In 1969, he developed a computerized analysis intended for routine
use by clinicians using a lateral and frontal cephalometric tracing and
a long range growth projection to maturity.
86

SAMPLE: 1000 CASES
The purpose of the analysis is objective and encompasses the 4 C’s of
cephalometrics :
To characterize or describe the existing conditions.
To compare one individual with another or the same individual
with himself at a later time.
To classify certain descriptions into various categories.
To communicate all these aspects to the clinician, to a fellow research
worker, or to a parent.
87

AIM:
• To clarify the science of cephalometrics and free it from some of the
confusion and misuse pervading the discipline.
• He also wanted to point out that the use of cephalometrics to
describe and classify a malocclusion was one thing (Analysis) and the
act of treatment planning as a result of this classification and
description was another thing (synthesis)
88

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.
89

This analysis employs somewhat
less traditional measurements &
reference points, which are as
follows:
 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.
 C1 – Condyle -- A point on the condylar
head in contact with & tangent to the
ramus plane.
 DT -- Soft tissue -- The point of anterior
curve of the soft tissue chin tangent to
the esthetic plane or E line.
90

 CC -- Center of cranium -- The point
of the intersection of Ba-Na plane &
the facial axis.
 CF - Points from plane at pterygoid --
The point of intersection of
pterygoid root vertical to the FHP.
 PT -- PT point -- The junction of the
pterygomax. Fissure & the foramen
rotundum.
 DC – Condyle -- The point in the
center of the condylar neck along
Ba-Na plane.
91

 En – Nose -- A point on the soft
tissue nose tangent to the esthetic
plane.
 Gn – Gnathion – A point on the
intersection of the facial & the
mandibular Plane.
 Go – Gonion -- A point at the
intersection of the ramus &
mandibular Plane.
 PM – Suprapogonion -- Point at
which the shape of the symphysis
mentalis changes from convex to
concave- also known as
protuberance menti.
92

 Pog – Pogonion -- Point on the bony
symphysis tangent to the facial plane.
 Po – Cephalometric -- Intersection of
facial plane & the corpus axis.
 Ti – Ti point -- Point of intersection of
occlusal Plane & the facial plane.
 Xi -- Xi point -- It is located at the center
of a rectangle enclosing the ramus, at
the intersection of its diagonals. First
FH plane & then pterygoid vertical is
drawn. The rectangle is constructed by
means of drawing 4 planes tangent to
points R1, R2, R3 & R4.
93

The location of the Xi point is keyed geometrically to the
Frankfort horizontal(FH) and the pterygoid root vertical
planes(PtV). This procedure follows:
1. Locate FH and draw PtV plane perpendicular to the
FH pane
2. Construct four planes tangent to point R1 R2 R3
and R4 on the borders of the ramus.
o R1—deepest point on the anterior border of the
ramus, located halfway between the superior and
inferior curves.
o R2– located on the posterior border of the ramus,
opposite R1
o R3– deepest point of the sigmoid notch, halfway
between the anterior and posterior curves
o R4– opposite R3 on the inferior border of the
mandible
3. The constructed planes form a rectangle enclosing
the ramus.
4. Xi point is located near the centre of the rectangle at
the intersection of the diagonals. 94

PLANES:
• Frankfurt horizontal -- Extends from
porion to orbitale.
• Facial plane -- Extends from nasion to
pogonion.
• Mandibular plane -- Extends from
cephalometric gonion to cephalometric
gnathion.
• Pterygoid vertical -- A vertical line drawn
through the distal radiographic outline of
the pterygomax. fissure & perpendicular
to FHP.
96

• Ba-Na plane -- Extends from basion to
the nasion. Divides the face and
cranium
• 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.
97

Occl.Plane
A-Pog/ Dental plane
99

Occl.Plane
A-Pog/ Dental plane
E-plane
100

AXIS
Facial axis - A line
extending from the
foramen rotundum( PT to
Gn )
Condylar axis – extends
from DC to Xi point
101

AXIS:
• Corpus axis - extends from Xi to
PM
102

Interpretation
• This consists of analyzing:
Chin in space.
Convexity at point A.
Teeth.
Profile.
103

CHIN IN SPACE
This is determined by
Facial axis angle.
Facial (depth) angle.
Mandibular plane angle.
Lower facial height.
Mandibular arc.
104

 FACIAL AXIS ANGLE
 The angle formed by the
intersection of the facial axes (
PT to Gn ) & cranial axes (Ba-
Na).
 Mean value is 90˚ ± 3˚.
 A lesser angle suggests a
retropositioned chin where as
angle greater than a right angle
suggests a protusive or forward
growing chin.
105

 FACIAL(DEPTH) ANGLE
 Angle formed by FH plane & facial
plane ( N-Pog )
 Changes with growth.
 Mean value is 87 + 3 with an
increase of 1˚ every 3 years.
 Indicates the horizontal position
of chin & therefore suggests
whether class II or class III pattern
is due to the position of the
mandible.
106

MANDIBULAR PLANE
• Measures an angle to FH.
• On average, this angle is 26 degrees at 9 years and decreases
approximately 1 degree every 3 years.
• A high or steep mandibular plane angle implies that an open bite may
be caused by the skeletal morphologic characteristics of the
mandible.
• A low mandibular plane suggest deep bite.
107

 CONVEXITY
 CONVEXITY AT POINT A
 The convexity of the middle face is
measured from point A to the facial
plane(N-Pog)
 The clinical norm at 9 years of age is
2mm and decreases 1 degree every 5
years.
 High convexity suggests a class II
skeletal pattern; negative convexity
suggests a class III pattern.
108

 TEETH
 MANDIBULAR INCISOR TO A-Pog
 This measurement is used to define the protrusion of the mandibular arch.
 Ideally the mandibular incisors should be located 1 mm ahead of the A-Pog line.
 Constant with age, any change would affect arch length.
109

 MAXILLARY MOLAR TO PtV
 This measurement is the distance
from PtV(back to the maxilla) to the
distal of the maxillary molar.
 On average, this measurement
should equal the age of the patient
plus 3mm.
 This assists in determining whether
the malocclusion is due to position
of maxillary or mandibular molar.
 It is also useful in deciding whether
extractions are necessary.
110

 MANDIBULAR INCISOR
INCLINATIONS( 1 TO Apog)
 Angle formed between A - PO
line & axis through the lower
central incisor
 On average, this angle should be
22+4 degrees.
 No age changes.
111

 PROFILE
LOWER LIP TO E-LINE
 The distance between the lower
lip and the esthetic (nose-chin)
line is an inclination of the soft
tissue balance between the lips
and the profile.
 The average norm for this
measurement is -2mm at 9 years
of age.
 The positive values are those
ahead of the E line.
112

Mean values of Ricketts analyses
113

INTRODUCTION
• Charles J. Burstone et all in 1978 developed an analysis specially
designed for patients requiring orthognathic surgery.
• Given in University of Connecticut.
• They used the landmarks and the measurements that can be altered
by common surgical procedures.
• This is also known as Cephalometrics for Orthognathic
Surgery(COGS)
115

COGS system describes the horizontal and vertical positions of the
facial bones by the use of constant coordinate systems as follows:
• Size of the bone are represented by direct linear measurements.
• Shape of the bones are represented by the angular measurements.
• Chosen landmarks and measurements can be altered by various
surgical procedures.
This analysis includes all the facial bones and a cranial base
reference.
• facial skeletal components are measured.
• Measurements used, can be readily transferred to mock surgery.
• This systemized approach to measurements can be computerized.
116

Sample:
From Child Research Council of the University of Colorado School of Medicine.
• Size: 30.
• 14 males and 16 females
• Race: Caucasian
• Age: 5 – 20 years
117

Landmarks used:
• SELLA (S)
• NASION (N)
• ARTICULARE (Ar)
• PTERYGO MAXILLARY FISSURE
(Ptm)
• SUBSPINALE (Pt A)
• POGONION (Pog)
• SUPRAMENTALE (B)
• ANTERIOR NASAL SPINE (ANS)
• POSTERIOR NASAL SPINE (PNS)
• MENTON (Me)
• GNATHION (Gn)
• GONION (Go)
118

Planes used:
Horizontal plane:
The base line for comparison for most the data in COGS analysis.
 Is a constructed plane called ‘Horizontal Plane’ which is a surrogate FH plane,
constructed by drawing a line 7º from SN plane.
Most measurements are made for projections either parallel or perpendicular to HP
Mandibular Plane: constructed from menton to gonion.
Nasal Floor: plane constructed from ANS to PNS.
Occlusal Plane: is a line drawn from the buccal groove of the permanent first molar
through a point 1mm with in the incisal edge of the central incisor in each arch.
119

ANALYSIS
Cranial base
 Ar- N:
 Skeletal base line for correlating
other measurements.
 Relatively stable anatomic plane.
 Can be changed by cranial surgery or
auto-rotation of mandible.
120

 Ar-Ptm:
 Determines horizontal distance
between maxilla and mandible
posteriorly.
 More the distance between Ar-
Ptm, more the mandible lies
posterior to maxilla.
 Male- 37.1 ± 2.8mm
 Female- 32.8± 1.9mm
121

Ptm-N:
Determines the horizontal end of
maxilla.
Its less in cases of mid facial
deficiency, Class III and Cleft Palate.
Male- 52.8 ± 4.1mm
Female- 50. ± 3mm
122

• Horizontal Skeletal Profile Analysis
A few simple measurements should be made on the skeletal profile
to assess the amount of discrepancy in anteroposterior direction.
It is called as Horizontal Skeletal Profile analysis because all the
measurements in this set of analysis are made parallel to HP.
123

 N-A-Pg:
Angle of convexity.
Drawback: does not indicate the jaw involved.
positive –convex profile, clockwise angle.
negative – concave profile, counterclockwise angle.
Male: 3.9º ± 6.4º
Female: 2.6º ± 5.1º
124

N-A:
Horizontal distance from Pt A to
perpendicular from HP through N.
Describes whether anterior part of
maxilla is protrusive / retrusive
Male:0.0 ± 3.7mm
Female: - 2 ± 3.7mm
125

N-B:
The horizontal distance of Pt B to the line
perpendicular to HP through N gives N-B
measurement.
 Gives horizontal position of the apical base
of mandible in relation to N in AP direction.
positive value when Pt B is ahead.
negative value when Pt B is behind the
perpendicular line.
Male: -5.3±6.7 mm
Female: -6.9±4.3 mm
126

N-Pg:
Indicates the prominence of the chin.
Used in planning of genial augmentation
or genial reduction.
Male: -4.3±8.5mm
Female: -6.5±5.1mm
127

Horizontal skeletal profile represents the facial convexity, the
horizontal relationship of the apical base A and B points, and the chin
as related to N.
Each separate measurement should be viewed as it relates to other
horizontal measurements.
After all the measurements are considered, the surgeon has a
quantitative skeletal cephalometric description of the horizontal
anterior facial discrepancy
128

• Vertical Skeletal Analysis
A Vertical skeletal discrepancy may reflect an anterior, posterior or
complex dysplasia of the face
It is divided into two components :
Anterior component and Posterior component
129

Anterior component
• N-ANS:
Represents middle 1/3rd facial
height.
Male:54.7±3.2mm
Female:50.0±2.4mm
• ANS-Gn:
Represents lower 1/3rd facial height.
Male:68.6±3.8mm
Female: 61.3±3.3mm
130

Posterior component:
PNS-N:
 Represents posterior maxillary height.
 males:53.9±1.7mm
 Female:50.6±2.2mm
MP-HP:
 Represents posterior facial divergence with
anterior facial height.
 Males:23.0º±5.9º
 Females:24.2º±5.0º
131

Vertical skeletal measurement of the anterior and posterior
components of the face helps in diagnosis of anterior and posterior or
total vertical maxillary hyperplasia or hypoplasia, and clockwise or
counterclockwise rotations of the maxilla and mandible., the surgical
corrections of these problems includes total max. advancement or
reduction, posterior max. augmentation or reduction and mandibular
ramus rotation and ramus height reduction.
132

Vertical dental analysis
ANTERIOR COMPONENT
Upper CI- NF: distance b/w the incisal edge of the upper
central incisor and the palatal plane measured on the
perpendicular to the palatal plane intersecting the incisal
edge.
Represents anterior maxillary dental height.
 Male: 30.5 ± 2.1mm
 Females: 27.5 ± 1.5mm
Lower CI-MP: distance b/w the incisal edge of the lower
central incisor and the mandibular plane measured on the
perpendicular to the mandibular plane intersecting the
incisal edge.
represents total vertical dimension of anterior mandible.
 Male: 45.0 ± 2.1mm
 Female: 40.8 ± 1.8mm
133

POSTERIOR COMPONENT
 Upper 1st molar-NF: distance b/w the tip of the mesiobuccal
cusp of upper first molar to the palatal plane on the
perpendicular to the palatal plane intersecting the MB cusp
 Represents posterior maxillary dental vertical height.
 Males:26.2±2mm
 Female:23.0±1.3mm
 Lower 1st molar-MP: distance b/w the tip of mesiobuccal
cusp of lower 1st molar and the mandibular plane, measured
on the perpend. To the mandibular plane, intersecting the
cusp.
 Represents Posterior vertical mandibular dental height.
 Males: 35.8±2.6mm
134

Maxilla and mandible
Maxilla:
• PNS-ANS:
Gives the effective length of maxilla.
This distance with the ANS-N and PNS-N
measurements gives a quantitative description
of the maxilla in the skull complex
Males:57.7±2.5mm
Females:52.6±3.5mm
135

Mandible:
Ar-Go (linear):
 Gives quantitative length of mandibular ramus.
 Males:52.0±4.2mm
 Females:46.8±2.5mm
Go-Pg (linear):
 Linear measurement of mandibular body.
 Males:83.7±4.5mm
136

Ar-Go-Gn: (gonial angle)
 Represents relation between mandibular ramus and body.
 Males:119.1º ±5.1º
 Females:122.0º±6.9º
B-Pg:
 Describes mandibular chin prominence with respect to
mandibular denture base.
 Males:8.9±1.7mm
137

• These measurements are helpful in the diagnosis of variations in
ramus height that effect open bite or deep bite problems, increased
or decreased mandibular body length acute or obtuse Go angle that
can contribute to skeletal open or closed bite and finally as an
assessment of chin prominence
• These mandibular problems may be isolated or may occur in any
combination.
138

Dental
Occlusal plane angle
Angle formed between OP plane and HP. If the
teeth overlap anteriorly to produce an overbite,
the OP can be drawn as a single line.
If an anterior open bite is present then, Op passes
through a point 1 mm within the incisal edge the
two Op must be drawn and measured separately
for the angle with HP.
Each OP is assessed as to its steepness or flatness
Vertical facial and dental height must be assessed
to determine which OP should be corrected.
139

Increased OP-HP may be associated
with skeletal open bite, lip
incompetence, increased facial
height and retrognathic mandible.
Decreased OP-HP seen in deep bite,
decreased facial height.
Male:6.2 º±5.1º
Females:7.1º±2.5º
140

 AB-OP (linear):
Gives relationship of maxillary and
mandibular apical bases to OP.
Males:-1.1±2mm
Females: -0.4±2.5mm
141

 Upper CI- NF (angle):
This is constructed from a line drawn
from the incisal edge of incisors
through the tip of the root to the point
of intersection with NF.
Males:111.0º±4.7º
142

Lower CI-MP (angle):
Represents the angulation of lower CI
to MP.
Determines the procumbence /
recumbence of the incisors.
Males:95.9º±5.2º
143

Summary
 This cephalometric analysis is one step in diagnosis and treatment
planning for a surgical case.
 It gives the clinician an insight into the quantitative nature of the
skeletodental and also soft tissue dysplasia.
 COGS analysis uses linear dimensions to describe the size and
positions of facial bones and this is practical because surgeon thinks
more in millimetres than in angles for planning and accomplishing
procedures.
144

INTRODUCTION
• The Rakosi's analysis is an important diagnostic tool in planning
functional appliance therapy.
• It consists of:
1. Analysis of facial skeleton
2. Analysis of mandibular and maxillary base.
3. Dento-alveolar analysis
146

Analysis of facial skeleton
SADDLE ANGLE
 ARTICULAR ANGLE
GONIAL ANGLE
 FACIAL HEIGHT
 EXTENT OF ANTERIOR AND POSTERIOR CRANIAL BASE LENGTH
147

 Saddle angle
Angle formed by joining points N S and Ar.
The normal value is 123° + 5°.
The saddle angle is large in Retrognathic
faces and is small in prognathic faces.
Thus a large saddle angle signifies posterior
condylar position and mandible that is
posteriorly placed in relation to cranial base
and maxilla.
148

Articular angle
It is formed by joining the points S Ar and Go.
 It is the constructed angle between the upper
and lower contours of the facial skeleton. It
depends on the position of the mandible .
Mean = 143 + 6°
It decreases with anterior positioning of the
mandible, deep bite and mesial migration of
the posterior segment.
Increases with posterior relocation of the
mandible , opening of the bite and distal
deviation of posterior segment.
149

Gonial angle:
The angle formed by the tangents to the body
of the mandible and posterior border of the
ramus .
It not only gives the form of the mandible but
also gives information about the direction of
growth of the mandible.
 If the angle is small it signifies horizontal
growth pattern and is favourable condition for
anterior positioning of the mandible using an
activator.
If the angle is large it signifies vertical growth
pattern.
Mean value is 128± 7°.
150

Upper and lower gonial angle of Jarabak:
The gonial angle may be divided by a line
drawn from nasion to gonion.
This gives an upper and lower gonial angle of
Jarabak.
The upper angle is formed by the ascending
ramus and the line joining nasion and gonion.
A larger upper angle indicates horizontal
growth.
151

The lower angle is formed by the line joining nasion and gonion and
the lower border of the mandible.
A larger lower angle indicates vertical growth pattern.
The mean value is 72-75°.
Gonial angle has marked influence on:
 direction of growth
 profile changes
 position of lower incisors
152

Sum of posterior angle:
Sum of posterior angles is Saddle angle +
Articulare angle + Gonial angle
 If the sum is more than 396° then it is
clockwise direction of growth.
 If the sum is less than 396° then it is
anticlockwise direction of growth.
If the sum is less than 396° then it is
favourable for functional appliance therapy.
153

Facial height
POSTERIOR FACIAL HEIGHT is measured from
S to Go.
It is more in patients having horizontal growth
pattern than patients having vertical growth
pattern.
 ANTERIOR FACIAL HEIGHT is measured from
N to Me.
 It is more in patients having vertical growth
pattern than patients having horizontal
growth pattern.
154

Jarabak’s ratio:
• It is given by the formula : Posterior facial height x 100
Anterior facial height
• A ratio of less than 62% expresses a vertical growth pattern whereas
more than 65% expresses a horizontal growth pattern.
155

Extent of anterior cranial base length:
Measured between center of superior
entrance to N point.
 Used to compare length of jaw bases
Increases ¾ mm annually
18yr = 75.4 mm ( males)
70.1 mm (females)
156

Extent of posterior cranial base length:
 Sella to articulare
Mean 32-35mm increase of 8mm from 8-
16yrs
Short cranial base seen in vertical growth
pattern ,skeletal open bite, poor prognosis
for functional appliance therapy
Midface appears prognathic, secondary
decrease in AFH
157

Analysis of jaw bases:
• SNA
• SNB
• BASE PLANE ANGLE
• INCLINATION ANGLE
• EXTENT OF MAXILLARY BASE
• EXTENT OF MANDIBULAR BASE
• LENGTH OF ASCENDING RAMUS
158

SNA
 SNA expresses the sagittal
relationship of the anterior limit of
the maxillary apical base to the
anterior cranial base.
 It is large in prognathic maxilla and
small in retruded maxilla.
Mean value is 81°. In cases of very
large SNA, like in Class II Div 1,
Activator therapy is contraindicated.
159

SNB
SNB expresses the sagittal
relationship between the anterior
extent of the mandibular apical base
and anterior cranial base.
It is large with a prognathic mandible
and small with a retrusive mandible.
If SNB is small and mandible is
retrognathic functional appliance
therapy is indicated.
Mean=79°
 >82=prognathic mandible
 <77°=retrognathic mandible
160

ANB
• Mean is 2 degrees.
161

SN- Pog:
 determines basal position of mandible. If the chin projects to a
marked degree, the difference b/t SNB and SN-Pog is large.
76° at 6yr ; 80° at 16yr
SN –Pr and SN- Id:
Relation b/t alveolar process of maxilla and mandible with the cranial
base
These above angles determine relationships in sagittal plane.
162

Base plane angle:
• The base plane angle is the angle between the
palatal plane and the mandibular plane.
• Defines the angle of inclination of mandible to
maxillary base
• Angle also serves to determine the rotation of
mandible
• It is large in vertical growth pattern and small
in horizontal growth patterns. Mean value is
25° .
• The base plane angle is divided into 2: Upper
– between the palatal plane and the occlusal
plane. Mean value is 11°. lower – between the
occlusal plane and the mandibular plane .
Mean value is 14°.
163

 Inclination angle: J angle (Schwarz)
• It is the angle formed by the
perpendicular line dropped from
N- Se at N and the palatal plane.
• A large angle expresses upward
and forward inclination whereas
small angle indicates down and
back tipping of the anterior end
of the palatal plane and maxillary
base.
• Mean value is 85° .
164

SN-MP
• Gives the inclination of the mandible to
Anterior cranial base.
• Mean- 32°
>32°=posterior inclination
<32°= anterior inclination
• The angle registers vertical dysplasia, changes
b/t sella and fossa and below fossa.
e.g.: open bite with large SN-MP indicates
that the molars have erupted in disproportion
to incisors.
165

Y-axis
• Determines position of the mandible
relative to cranial base as an additional
check.
• Mean= 66°
• >66° = mandible posterior position
• <66° = mandible anterior position
relative to Cranial base
166

Linear measurements of the jaw bases
EXTENT OF MANDIBULAR BASE
EXTENT OF THE MAXILLARY BASE
 LENGTH OF ASCENDING RAMUS
167

Extent of the mandibular base:
• The extent of the mandibular base is
determined by measuring the distance
between Go and Pog.
• More in patients having horizontal
growth pattern than patients having
vertical growth pattern.
• Ideally it should be 3mm more than the
anterior facial height until 12 yrs. and
3.5mm more after 12 yrs.
• Mean = 68mm at 8 yrs.
• Annual increase of 2mm for boys
1.4 mm for girls
168

Extent of the maxillary base:
• It is determined by measuring
the distance between the PNS
and a perpendicular drawn from
point A to the palatal plane.
• The difference of the
measurement between
horizontal and vertical growth
pattern is slight
• Mean = 45.5mm at 8yr
• Annual increase:
1.2 in boys
0.8mm in girls
169

Length of ascending ramus
 measured Go – Condylion
mean at 8yr is 46mm
Annual increase of 2mm for
boys 1.2 mm for girls up to 16yrs
170

Width of ascending ramus:
Determined at height of occlusal plane
Mean- 27mm at 8yr
At 16yr 32.5mm for boys
30.5mm for girls
171

Analysis of the dentoalveloar relationship:
• UPPER INCISORS
• LOWER INCISORS
• POSITION OF THE INCISORS
172

Axial inclination of upper incisors
Long axis of maxillary incisor extended to incisor
extended to intersect SN line and posterior angle is
measured. mean=102° , attained 2yr after eruption
Also angle formed with palatal plane
measured. Enlarged angle signifies very upright
Incisors, smaller than average angle indicates
protrusion
mean = 70+/- 5°
These 2 measurements used in treatment planning
E.g.: regarding need for root torqueing.
173

Lower incisors:
 Posterior angle between MP and long
axis of lower Incisor
 Mean 90 + 3°
 From 6 to 12 years, angle increases
from 85-94 degrees.
174

Position of incisors
• Upper incisor to Npog line:
Mean: 4+/- 2mm
• Lower incisor position:
mean: - 2 to +2mm
• Inter incisal angle:
between long axis of maxillary & mandibular incisor
Mean value 135degree.
175

Position of the incisors:
Upper incisor to N pog line
Mean: 4+/- 2mm
Lower incisor position
Mean: - 2 to +2mm
176

Introduction
 This method of analysis represents an effort to relate teeth to teeth, teeth
to jaws, each jaw to the other, and the jaws to the cranial base.
 The analysis method is derived, in part, from the principles of the
cephalometric analyses of Ricketts and of Harvold's, although other
aspects, such as the construction of the nasion perpendicular and the
point A vertical, are presumed to be original composite normative
standards based on three cephalometric samples are taken.
 These are Burlington, Bolton, and Ann Arbor samples. These values have
been empirically tested and redefined, and have been found useful in
determining treatment protocols. Retrospectively, these protocols appear
to have been appropriate.
178

Analysis
• In the analysis of a single film, the positions of the maxilla and mandible are
related to cranial structures as well as to each other.
• In an effort to create a clinically useful analysis, the craniofacial skeletal complex
is divided into five major sections:
Maxilla to cranial base
Maxilla to mandible
Mandible to cranial base
Dentition
Airway
179

Sample
• The composite normative standards used in the McNamara analysis
were derived from three sources:
1. Lateral cephalogram of the children comprising the Bolton
standards
2. Selected values from a group of untreated children from the
Burlington Research centre
3. A sample of young adults from Ann Harbor,Michigan with good to
excellent facial and dental configurations
180

Maxilla to Cranial base
oSoft tissue
a. Nasolabial angle
b. Cant of upper lip
oHard tissue
a. Relating pt. A to nasion perpendicular
181

NASOLABIAL ANGLE:
• It is formed by drawing a line tangent to base
of the nose and a line tangent to the upper lip.
• Its average value in adult male and females
with well balanced jaws is 102 + 8 degrees.
• An acute angle may be a reflection of dento-
alveolar protrusion , but also occur because of
the orientation of the base of the nose.
182

CANT OF UPPER LIP
• The cant of upper lip should be
slightly forward to form an angle of
14 + 8 degrees in adult women and 8
+ 8 degrees in adult men with the
nasion perpendicular.
• Nasion perpendicular is a vertical line
drawn from nasion , perpendicular to
Frankfurt horizontal
183

Na PERP. TO POINT A
• The linear distance is measured between nasion perpendicular and point A.
• It determines the antero-posterior position of maxilla relative to the cranial base.
• An anterior position of point A is a positive value , indicating maxillary skeletal
protrusion. A posterior position of point A is taken as a negative value, indicating
maxillary skeletal retrusion.
• The measurement is 0mm in mixed dentition and 1mm in adults (males &
females).
184

RELATING MAXILLA TO MANDIBLE: (MIDFACE)
MAND. & MAX. LENGTH
• Maxillary length or the mid-facial
length is measured from Co to point A
• Mandibular length is measured from
Co to Gn.
• A linear relationship exists between
the two. Any given effective Midfacial
length corresponds to an effective
mandibular length within a given
range.
186

 The two measurements are not age or sex dependent but are related to the size
of component parts.
 Thus the terms ‘small’ , ‘medium’ & ‘large’ are used.
 The maxillomandibular differential is determined by subtracting the midfacial
length from the effective mandibular length.
 In small individuals : 20 to 23 mm
 In medium sized individuals: 27 to 30 mm
 In large sized individuals : 30 to 33 mm
 In the event of any discrepancy, the next step would be to identify which jaw is
too large or small , or whether both are at fault.
187

LOWER ANTERIOR FACIAL HEIGHT
• It is measured from ANS to Me. This
dimension correlates with the effective
length of midface .
• Small individuals: 60-62mm (midface
length of 85mm)
• Medium sized individuals: 66-68mm
(midface length of 94mm)
• Large sized individuals: 70-74mm
(midface length of 100mm)
188

• An increase or decrease in the lower anterior facial height can have a
profound effect on the horizontal relationship of the maxilla and
mandible.
• For example, if the mandible is rotated downward and backward
concomitant with a increase in lower anterior facial height , the chin
point moves away from the Na perpendicular. If the lower anterior
facial height is shortened, autorotation of the mandible will move the
chin point forward.
• 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.
189

MANDIBULAR PLANE ANGLE
• Angle between Frankfort horizontal and
Go-Me.
• Average value: 22 + 4 degrees.
• Inference: a higher angle is suggestive of
excessive LAFH . Conversely, a lesser
angle tend to indicate a deficient LAFH.
• However, higher or lower values can also
be a result of shorter or longer average
mandibular ramus heights, respectively
(or posterior facial height).
190

FACIAL AXIS ANGLE (RICKETTS)
• Angle between PTM to Gn , relative to
the cranial base (Ba-Na)
• In a balanced face, this value is 90
degrees.
• A negative value i.e. 90 degrees
subtracted from the measured angle,
is suggestive of excessive vertical
development of the face. Deficient
vertical development of the face is
indicated by positive values.
191

RELATION OF MANDIBLE TO
CRANIAL BASE
• Pog TO Na PERPENDICULAR: measuring the
distance from Pog to nasion perpendicular.
• For small individuals (mixed dentition): -8
to -6mm Pog lying posterior to Na
PERPENDICULAR)
• For medium size face(adult women): -4 to
0mm
• For large size face(adult men): -2 to +2 mm
192

DENTITION
MAXILLARY INCISOR POSITION
• The anteroposterior position of the upper
incisor can be located by using measurements
that relate the dental portion of the maxilla to
the skeletal portion of the maxilla.
• A vertical line is drawn through point A parallel
to nasion perpendicular. The distance from
point A to the facial surfaces of the upper
incisors is then measured.
• Average value = 4 – 6mm
• Greater values are suggestive of protruding
incisors and lesser values indicate
retruded upper incisors.
194

• The vertical position of the upper incisor is best determined at the
time of the clinical examination, although a head film taken with the
lips at rest may also be useful.
• Typically, the incisal edge of the upper incisor lies 2 to 3 mm below
the upper lip at rest.
195

MANDIBULAR INCISOR POSITION
• The anteroposterior position of lower
incisors is also determined in relation to its
bony base.
• The distance between the edge of the
mandibular incisor and a line drawn from
point A to Pog (A-Pog line) is measured.
• The facial surface of the lower incisor lies 1
mm to 3 mm anterior to the A-pogonion
line.
196

VERTICAL POSITION:
In the assessment of the vertical position of the lower incisor, the
incisal tip is related to the functional occlusal plane.
If the curve of Spee is excessive a decision must be made as to
whether the lower incisors should be intruded or the molars erupted.
The determining factor is the lower anterior facial height. If the lower
anterior facial height is normal or excessive (determined by relating it
to effective midface length), the lower incisor should be intruded.
Should lower anterior facial height be deficient, the lower incisor
should be extruded, or the buccal segments further erupted.
197

Airway
Upper pharynx:
• Upper pharyngeal width is
measured from a point on the
posterior outline of the soft palate
to the closest point on the
pharyngeal wall
• This measurement is taken on the
anterior half of the soft palate
• The average nasopharynx is 15 to
20mm in width
• A width of 2mm or less in this
region may indicate airway
impairment.
198

Lower pharynx
• Lower pharyngeal width is measured
from the point of intersection of the
posterior border of the tongue and
the inferior border of the mandible to
the closest point on the posterior
pharyngeal wall
• The average measurement is 11 to
14mm, independent of age.
199

INTRODUCTION
• Bjork conducted extensive studies on 322 Swedish boys, 12 years of
age and 281 young adults 21 to 23 years of age and included almost
90 different measurements.
• This analysis was done by Bjork to investigate the effects of variations
of jaw growth and the relationship between facial form and occlusion.
• The profile analysis, is similar to Steiner analysis in that it uses the SN
as the reference and SNA, SNB along with Go- Gn.
• This was published in his book “The face in profile”.
201

Sample
origin: Group II - boys from the town of Vasteraas, Sweden
Group III - army conscripts (n=215) from the Dalkarlia Regiment
drawn from the entire population of this area and voluntary high
school graduates (n=66)
size and age-
• Group 1-20 twelve-year-old
• Group II - 322 twelve-year-old
• Group III - 281 conscripts and high school graduates
Sex-males
Race –Scandinavian
202

Clinical characteristics-Group II - very good condition of the teeth,
only single permanent teeth decayed or single teeth missing, no
orthodontic treatment
Group III - cases with fixed bridges, removable dentures and
completely decayed bite were excluded.
None of the conscripts had received orthodontic treatment
Purpose- to investigate the effects of variations of jaw growth and
the relationship between facial form and occlusion.
203

• Bjork used the angle N-S-Ar (saddle angle), S-Ar-Go (Articular Angle)
and Ar-go-Gn (gonial angle) to predict the growth change in face.
• Bjork felt that at the age of 11years the length of anterior cranial
base (S-N) should be equal to mandibular body length (go-me)
• He stated that the ideal ratio of posterior cranial base length to ramus
height is 3:4.
• This gives the basic skeletal evaluation and the incisor axis to A-Pog
relates the denture to the skeletal base.
204

Reference planes
NSL: line joining sella-nasion
Nasal line(NL): Line joining Sp and snp
206

Mandibular line (ML): Tangent
through lower border of mandible
through Go
207

Occlusal line superior(Ols): Line
through incision superius (is) and
molar superius(ms)
208

Occlusal line inferior(Oli): Line
through incision inferius(ii) and molar
inferius(mi)
209

Chin line(CL): Tangent to chin to
infradentale
210

ANALYSIS
DENTOBASAL RELATIONSHIP
Sagittal:
 Dentoalveolar
a.Maxillary alveolar Prognathism (Pr-n-
ss)
Mean is 2+1 degree.
211

b)Mandibular alveolar prognathism
(ML/CL)mandibular line / chin line
Mean- 70+6 degree
212

c) Maxillary incisor inclination:
(ils/NL)
Mean: 110+6 degrees
D. Mandibular incisor inclination:
(iLi/ML)
Mean: 94+6 degrees
213

BASAL
Sagittal jaw relationship
a) ss-n-Pg
Mean:2+2.5degrees
b) ss-n-sm
Mean: 3+2.5degrees
214

VERTICAL
1.Dentoalveolar
a) Maxillary zone(NL/oLs)
Mean :10+4 degrees
b) Mandibular zone(ML/oLi)
Mean : 20+5 degrees
215

BASAL
Vertical jaw relationship(NL/ML)
Mean : 25+6
216

Cranial relationships
• Sagittal
• BASAL
a. Maxillary Prognathism
S-n-ss
Mean: 82+3.5 degrees
b. Mandibular Prognathism
S-n-pg
Mean : 80+3.5 degrees
217

 Vertical
obasal
a) Maxillary inclination
NSL/NL
Mean: 8+3
b) Mandibular inclination
NSL/ML
Mean: 33+6
218

GROWTH ZONES
CRANIAL BASE
a) n-s-ar(saddle angle)
Mean: 124+5 degrees
b) n-s-ba
Mean: 131+4.5
219

MANDIBULAR MORPHOLOGY
a) B angle ( to Ar)
• Mean: 19+2.5 degrees
• B angle is formed by Mp and a line
from Ar intersecting the Mp at a point
where a line perpendicular to Mp and
tangent to the most anterior point on
symphysis intersects the Mp
b) Jaw angle:
• Ar-Go-Me
• Mean: 126+6 degrees
220

Bjork’s Polygon:
In this analysis a polygon is used to
assess the anterior and posterior
facial height relationships and also
to predict the direction of growth
change in the lower face.
 The basis of this is the
relationship of the 3 angles.
 Saddle angle (N.S Ar), Articulare
angle (S-Ar-Go), Gonial Angle (Ar-
Go_me) and the length of the sides
of the polygon.
221

It says, Anterior cranial base (S-N) should be equal to the mandibular
body length (Go-Me).
 The ideal ratio of the posterior cranial base length (S-Ar) to the
ramus height is 3:4
If the sum total of the 3 angles, Saddle angle, Articular angle, Gonial
angle exceeds 396, there would be tendency towards “clockwise”
growth change in mandible.
In case with the total less than 396 there would be a tendency of
"counter clock-wise” growth change in the mandible.
222

Clockwise change:
 Indicates that the anterior facial
height is increasing more rapidly
than posterior facial height and it
could be associated with backward
growth at the symphysis leading to
anterior open bite tendency.
223

Counter Clockwise Change
 Indicate that the posterior face
height is increasing more
rapidly giving rise to forward
growth of chin and anterior
deep bite tendency.
224

 Bjork along with the Skieller (1977) in order to study growth, applied
implants studies in animals and human beings.
 It involves the implanting of small bits of inert alloy into the bone as
radiographic reference points.
The areas where the implants were placed :
 Maxilla : Hard palate behind the deciduous canines. Below the
anterior nasal spines. Two on each side of the zygomatic process
Mandible : One in the mid line of the symphysis Two under the first
and the second pre molar One under the external aspect of the
ramus.
225

Their study revealed:
 Maxilla :They stated that maxilla undergoes extensive remodeling
during the growth period Resorption occurs in the lower part of the
lower part of the nasal floor more anteriorly than posteriorly.
 Mandible :Mandibular growth occurs essentially at the condyle and
the direction of the growth generally forward Thickening of the
symphysis was found to be attributable to growth on posterior
surface and on the lower border. The apposition and resorptive
processes result in individual shaping of the lower border of the
mandible, characterizing its growth.
227

Their results showed that the maxilla grows downward from the
cranial base at the rate of about 0.7 mm per year.
 Maxillary tooth eruption increases dentoalveolar height about 0.9
mm per year.
Mandibular eruption is about 0.75 mm annually.
The nasomaxillary complex descends around 1.5 to 2 mm per year of
the eruption of the mandibular teeth is added to this.
There is a total vertical development between 2 & 3 mm per year.
228

Jarabak Skeleto Dental Cephalometric Analysis
• Jarabak introduced a new measurement by adopting and modifying
the Bjork’s analysis.
• The following is a description of the linear and angular
measurements of the Jarabak Skeleto-Dental Analysis.
• The means of these angles is based on an average for Caucasian boys
and girls at age 11 years.
229

SKELETAL ANALYSIS
SADDLE ANGLE: This angle is formed
by the junction of the N.S. line
meeting with the a-S line at the
centre of the sella. The small “a” is
the articulare.
The mean of the saddle angle is
123+ 5deg.
230

ARTICULARE ANGLE: This is referred
to as the joint angle and is an angle
that can be changed by orthodontic
treatment.
It is the angle formed by the line from
the S to “a” and the line from “a” to
Go
 The mean value for this angle is 143+
6degrees.
231

GONIAL ANGLE: This angle is
formed by the body of the mandible
and the ascending ramus meeting at
extended Go point.
 The mean value of this angle is
130+ 7degrees.
232

• SUMTOTAL
 This total is obtained by adding the
saddle, articular and gonial angles.
The mean total of this skeletal
angles is 396degrees .
Any skeletal angle with the total of
403 – 405deg or greater is a
clockwise (posterior) grower.
 Any skeletal angle below 394deg is
a counter clockwise (anterior)
growing face.
233

• ANTERIOR CRANIAL BASE:
 This is the S-N line measured
linearly.
According to Bjork the linear
measurement for twelve year olds is
68.75 mm with a standard deviation
of 2.97
The mean for this measurement
established by Jarabak, is 71 mm +
3mm.
234

• POSTERIOR CRANIAL BASE:
 This is the linear measurement from
point S to point “a”.
 The mean for this line is 32 mm.
 This line is related to ramal height (a-
Go) in a 3 : 4 ratio.
235

• GONIAL ANGLE AND ITS PARTS:
 In order to estimate growth direction
more accurately, we must go beyond
accepting the gonial angle as a single
factor of mandibular morphology.
 If the upper angle is large 58deg to
65deg the remaining growth increment
will be sagittal.
236

• In the facial structures if the upper half of the gonial angle is small (43
to 48deg ) the remaining mandibular growth increment will be
downward and backward.
• Growth in the ramus will make the lower face more prognathic.
237

• RAMUS HEIGHT:
 This linear measurement is from the
articulare to extended gonion angle.
The Bjork sample height is 43.48 mm +
0.26mm.
In the Jarabak sample the mean length
is 44 mm.
This measurement (44 mm) is related
to the posterior Cranial Base Length (32
mm) in a 3 : 4 ratio
. The ramus height increased in length
with growth.
238

• MANDIBULAR BODY LENGTH
(CORPUS):
 The mandibular body length mean is
77mm.
It is in a 1:1 ratio with anterior cranial
base.
This value is the same as the Bjork
sample (73.58 mm + 0.31 mm).
239

• SNA ANGLE:
The maxilla can be related to the
cranium in one of three ways: Normal
relation Maxilla posterior to normal
Maxilla anterior to normal.
 The criteria which is used to
determine which one of the three
possibilities is present in the angle is
described by two planes. Sella to
nasion (SN) and Nasion to point A(NA).
 The Jarabak mean for the SNA angle is
78degrees.
240

• SNB ANGLE:
 The mandibular apical base is also
related to the cranium in of the three
ways; Normal relation Mandible
posteriorly related to cranium. Mandible
anteriorly related to cranium.
The mandibular apical base is identified
by the letter B. the angle between
mandibular base and cranium is SNB.
The Jarabak mean is 76 to 78deg .
241

• SN-gome ANGLE (ANTERIORCRANIAL BASE AND MANDIBULAR
BODY LENGTH)
 The mean of this angle is formed by the extended junction of
the SN line with GoMe line is 32degrees.
242

• FACIAL DEPTH– N.Go:
 This is a line measured from the nasion (N) to the extended gonion
and is listed in millimetres.
243

• FACIAL LENGTH ON ‘ Y AXIS:
This is a line measured from
the sella to a point at the
lowest portion of the most
prominent part of the
pogonion.
244

• Y AXIS TO SN:
This angle is formed by the junction of
the facial length with anterior cranial
base line (N-S).
The mean range for this angle is 64 to
68deg.
245

• POSTERIOR FACE HEIGHT (S-
Go):
 This is also known as the
Jarabak axis and contribute
s along with anterior face
height in forming the Face H
eight Ratio.
246

• ANTERIOR FACE HEIGHT ( N-Me):
 This line is measured from nasio
n to the lower border of the man
dible at menton.
247

• POSTERIOR AND ANTERIOR FACE HEIGHT RATIO:
This ratio is indicated by percentage is determined by dividing the a
nterior face height (mm) into the posterior face height (mm).
This will then give the direction the face will grow, either clock
wise or counter clockwise.
In this both the anterior and posterior facial heights are expressed in
the form of a ratio as follows Anterior facial height x 100
Posterior facial height.
 The mean range for clockwise growers is 54 to 58% or less. In the co
unter clockwise grower the mean range is 64 – 80%.
248

• FACIAL PLANE (N-Pog):
The mean angle of this plane is 8
1 to 82degrees
This compares favourably with Do
wn’s value for an orthognathic fa
ce
249

• DENTAL ANALYSIS: OCCLUSAL PLANE TO BODY OF MANDIBLE
This is measured at the junction of the occlusal plane line where it
meets the Go-Me line to form an angle.
The mean of this angle is 12degrees.
250

• DENTAL CONVERGENCE OF MAXILLARY AND MANDIBULAR INCISORS
 This angle is the junction of a line drawn through the long axis of the
maxillary and mandibular incisors.
 The mean of this angle is 133degrees.
251

• MANDIBULAR INCISOR TO BODY OF MANDIBLE
A line is drawn through the long axis of the mandibular incisor t
ooth which meets the line of the body of mandible gives the angle of
the forward or backward position of the incisors.
252

• MAXILLARY INCISOR RELATED TO SN LINE:
 The mean angle of the junction of the long axis of the maxillary incis
or where it meets the SN line is 102+ 2degrees.
253

• MAXILLARY AND MANDUBULAR INCISORS TO FACIAL PLANE (N-Po):
The mean for the maxillary incisors to facial plane is 5 mm + 2 m
m.
 The mean for the mandibular incisors to the facial plane is –
2 mm to + 2mm.
254

 FACIAL ESTHETIC LINE (RICKETTS):
 The Rickett’s facial aesthetic line is used by Jarabak because of its si
mplicity, reliability and because it can be used at the chairside w
ithout depending on the cephalogram.
Method : -
Placing a straight edge on the tip of the nose and the tip of the chin i
n the midline, assuming the lips are not too forward, the relationship
of the lips to the straight edge can be determined readily.
The mean range, taken from a cephalogram, is –
1 to 0.4 for the upper lip and 0 to +2 for the lower lip.
255

References
1. Radiographic Cephalometry – Alexander Jacobson
2. Orthodontic Cephalometry- Athanasios E Athanasiou
3. Current principle & technique – Grabers
4. Assessment of A-P dysplasia AJO1947
5. Rapid evaluation of facial dysplasia in vertical plane AJO 1952
6. Variation in facial relationships their significance in treatment & prognosis AJO
1948 34;812-40
7. A quadrilateral analysis of lower face skeletal AJO 1970
8. A serial cephalometric Roentgegraphic analysis of craniofacial form & growth
AJO June 1955
9. A roentgenographic cephalometric analysis of cephalo-facio-dental relationship
AJO 1955
10. The relation of maxillary structures to cranium in malocclusion and in normal
occlusion AJO1952
256

Lateral cephalometric analysis of hard tissues

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Lateral cephalometric analysis of hard tissues

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