The document describes the Mc Namara analysis method for cephalometric analysis. It consists of 5 sections: 1) relating the maxilla to the cranial base, 2) relating the maxilla to the mandible, 3) relating the mandible to the cranial base, 4) analyzing the dentition, and 5) airway analysis. Each section involves measuring distances and angles on a lateral cephalogram and comparing values to established norms. The analysis aims to evaluate the structural relationships of the jaws and aid in orthodontic diagnosis and treatment planning.
Dental tissues and their replacements/ oral surgery courses
Mc namara analysis /certified fixed orthodontic courses by Indian dental academy
1. Mc Namara Analysis
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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2. According to him, “during the last 3 decades, clinical
orthodontics has seen the advent of numerous
orthognathic surgical procedures that allow 3-D
repositioning of almost every bony structure in the
facial region. Similarly, facial orthopedics has
become part of everyday clinical practice..Therefore
we perceived a need for a method of cephalometric
analysis that is sensitive not only to the position of
the teeth within a given bone, but also to the
relationship of the maxilla, mandible and cranial
base structures, one to another.”
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3. He asserts that his analysis method is
presented as a language, which can be
used by the clinician to better identify
and describe the structural
relationships of the jaws, as well as to
communicate easily with other
clinicians as well as lay persons.
This method of analysis is derived in
part from the principles of the Ricketts’
and Harvold analyses.
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4. Basis: The Mc Namara analysis is useful in
Basis:
diagnosis and treatment planning of the
individual patient when values derived from
the tracing of the patients’ head film are
compared to established norms; the norms
from 3 gps have been derived:
The Bolton study (4-18)
The Ann Arbor sample (200 adults)
The Burlington sample (6-30)
Composite norms.
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5. This analysis consists of 5 major
sections:
Relating maxilla to cranial base
Relating maxilla to mandible
Relating mandible to cranial base
The dentition
Airway analysis
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6. I.Relating the maxilla to
cranial base:
soft tissue evaluation:
As part of the
clinical examination as
well as during
evaluation of the lateral
cephalogram, the
nasolabial angle and the
cant of upper lip should
be examined.
A)Norms
110° (scheidemann
et al)
102° ± 8° (Ann Arbor
sample)
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7. Acute nasolabial angle= Dentoalveolar
Protrusion
Miyajima et al(1996 AJO) compared the
above figures with untreated japanese with
ideal occlusion and found
more acute Nasolabial angle
Greater Bilabial Protrusion
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8. B)Cant of upper lip:
14°± 8° in females
(Ann Arbor sample)
8°± 8° in males (adult)
with the nasion
perpendicular.
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9. Hard tissue evaluation:
The antero-posterior
position of the
maxilla is
determined by
Constructing the Nasion
perpendicular.
The Linear distance from
point A to Nasion
Perpendicular is Measured
Ann Arbor
Norm=0.4mm(male)
Comp
Norm=0mm(Mixed D)
.
1mm(adult)
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10. Usually, the hard, soft tissue findings correlate
well with each other. However, when a discrepancy
exists between the two, the findings from the
clinical examination (ie. Soft tissue findings) should
take precedence. Treating patient only to specific
cephalometric norms must be avoided.
Drawbacks:
1) It is affected by position of nasion, which is
itself affected by cranial base length.
2) There is displacement of point A labially when
the roots are anteriorly tipped.
Note: A measurement of the SNA angle is also
included in this category.
Ann Arbor norms for SNA: male= 82.4 °
female= 83.9°
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11. II) Relating the mandible to the maxilla
(midface):
A) Effective midfacial length and mandibular
length: determined by measuring a line from
condylion to point A.
Effective mandibular length is derived by
constructing a line from condylion to anatomic
gnathion.
There is a geometric relationship between the
above two values; any given effective midface
length corresponds to a given effective
mandibular length.
Maxillomandibular differential: it is the
difference between the effective mandibular
length and effective midface length.
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12. A given effective
midfacial length
corresponds to an
effective mandibular
length within a given
range. “these are not
directly related to
patient’s age or sex”
Mid Face
Length=91mm
Range for
Mandible=115-118mm
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13. B) Vertical Dimension:
The clinical appearance of the relation between
upper and lower jaws is affected greatly by lower
anterior facial height (measured from ANS to
mention).
This linear measurement increases with age and
is correlated to the effective length of the
midface .
Eg: In Mixed dentition Analysis
Mid face Length= 85mm
Lower Anterior Facial Height= 60-62mm
In Medium sized individuals
Mid face Length= 94
Lower Anterior Facial Height= 65-67mm
In Large sized individuals
Mid face Length= 100
Lower Anteriorwww.indiandentalacademy.com 70-73mm
Facial Height=
14. Significance: Increase in Lower anterior
Facial Height -- Mandible appears retrognathic
Decrease in Lower anterior Facial Height
Mandible appears prognathic
In growing persons, an increased LAFH
camouflages a similar increase in mandibular
length, resulting in the appearance that the
chin is in the same position A-P, with respect
to cranial base structures.
This analysis also includes two other
measurements:
· 1)Mandibular plane angle:
1)
2)Facial axis angle of Ricketts:
2)
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15. Mandibular Plane
Angle: Angle between
F-H plane
Go-Me
N
S
Normal Value:22°+/- 4°
Go
Gn
Higher Vaue: Excessive
Lower Facial height
Lower Vaue: Deficiency
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16. Facial axis Angle: Angle between
a)Posterosuperior
aspect of pterygomaxillary fissure to gnathion
b)Line joining Basion to Nasion
Balanced Face =90°
Excessive vertical development , Anti clockwise
growth =Less than 90°(negative value)
Deficient vertical development, Clock wise
growth =Higher than 90°(positive value)
Thomas and Valiathan (June 1993) reported
normal directed growth of chin
90.65+/- 3.33
89.64 +/- 5.06 (Adult South Indians )
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90.07 +/- 3.16 (Adult North Indians)
18. III. Relating the mandible to the cranial
base:
The relationship of the mandible to the
cranial base is determined by measuring the
distance of the pogonion to the Nasion
perpendicular.
According to the composite norms:
In a mixed dentition (balanced face) pog lies
8mm to 6mm (ie, posterior) with respect to
Nasion
In adult male the chin position is usually
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-2mm to +2,, relative to Nasion perpendicular.
20. Dentition Analysis:
A.Relating Upper Incisor To
maxilla
A vertcal line is drawn through point
A parallel to nasion ⊥
The distance from point A to the
facial surface of Upper incisor is
measured
A-P position of Upper incisor
Comp Norms=
4-6mm(MixedD)
4-6mm(Adults)
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22. VERTICAL POSITION Upper Incisor
Clinically, and typically, the incisal edge of
upper incisor lies 2-3 mm below upper lip at rest.
This is subject to adjustment depending on
functional state of lip musculature and axial
inclination of the tooth prior to treatment.
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23. B. Relating the lower incisor to
the mandible:
Anteroposterior positionof Lower
Incisor:
Determined by using a
traditional version of the
Ricketts measurement of the
facial surface of the lower
incisor to the A-Pog line.
Bolton study Norms:
1.5 mm anterior to the
A Pog. Line.
Ann Arbor Norms:
2.3-2.7mm anterior to
the A Pog. Line.
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25. Vertical position Lower Incisor
Evaluated on basis of existing lower
anterior facial height.
First, the lower incisor tip is related
to the functional occlusal plane.
If curve of Spee is excessive:
a)lower incisor is to be intruded (if
LAFH is normal/excess) OR b)lower
molar is allowed to erupt and lower
incisor extruded. (when LAFH is
inadequate).
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26. V. Airway analysis:
Two measurements are used to
examine airway impairment.
Upper pharynx:
The upper pharyngeal width is
measured from a point on the
posterior outline of the soft palate
to the closest point on the posterior
pharyngeal wall. This is because the
area immediately adjacent to the
posterior opening of the nose is
critical
in
determining
upper
respiratory patency.
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28. Apparent airway obstruction, as indicated by an
opening of 2mm or less in the upper pharyngeal
measurement is only an indicator of possible airway
impairment.
For a more accurate diagnosis, an ENT
examination is required.
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29. Lower pharynx:
Lower pharyngeal width is measured from the
intersection of the posterior border of the tongue
and inferior border of the mandible to the closest
point on the posterior pharyngeal wall.
Ann Arbor sample =10-12mm ( average value)
does not change appreciably with age.
Smaller than average values are not
significant,
Greater than average value,15mm suggests
anterior positioning of the tongue, either as a
result of habitual posture, or due to
enlargement of tonsils.
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30. Certain conditions associated with
greater than average Lower
pharyngeal width are:
Mandibular prognathism
Dento-alveolar anterior crossbite
Bialveolar protrusion of teeth
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32. Bhat M, Sudha P, Tandon S.(June 2001)
Used Computerised cephalometrics, in measuring
skeletal and dental relationship in order to establish
norms for Bunt and Brahmin children of Dakshina
Kannada using McNamara's analysis.
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35. The purpose of this analysis is to
describe a method of cephalometric
analysis that has evolved over the past
two decades and which is designed
specifically to measure the dental and
skeletal effects that combine to produce
the occlusal changes that are the goals
of treatment.
The change in the molar and incisor
relationship can be expressed as an
exact algebraic sum
positive= If it reduces overjet/
corrects a class II
Negative = If it increases the overjet
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36. Accordingly, this accounting can support
comparisons of change between treatments
and between treatment phases, not only with
respect to magnitude, but also source (i.e.
skeletal or dental).
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38. Note: Apical base change (ABCH), the sum of
maxillary and mandibular translatory growth
relative to cranial base, represents the net
effect of skeletal growth, usually the amount
that the mandible has out-grown the maxilla.
Thus, ABCH plus upper and lower molar
movement equals the change in molar
relationship; ABCH plus upper and lower
incisor movement equals change in overjet.
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39. The pitchfork analysis thus requires that
we measure skeletal change as actual
physical displacement, rather than apparent
change in the position of a landmark due to
surface remodelling. Thus, our
measurements must be executed with
respect to landmarks that have a good
chance of being physically the same at both
time-points. All too often, this requirements
is not met.
The present analysis of occlusal change
employs three general superimpositions –
a)cranial base, b) maxilla, and c) mandible.
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40. Cranial base superimposition
S and Na under go change by local
remodeling during the growth period (Ford,
1958;Melsen, 1974). In contrast, the literature
argues that the bony anatomy from the
anterior half of sella turcica to the region of
foramen caecum and the internal outline of the
frontal bone is sufficiently stable to support
meaningful anterior cranial base
superimposition (De Coster, 1951; Bjork and
Skieller, 1983;).
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41. Specifically, Bjork and Skieller (1983)
suggest that the following ‘natural reference
structures’ be employed:
a)the anterior wall of sella turcica (and its
point of intersection with the lower contours
of the anterior clinoids),
b)the greater wings of the sphenoid,
c) thecribriform plate,
d)the orbital roofs
e)the inner surface of the frontal bone
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43. Maxilla
Best-fit registration for the maxilla is
both the
a)zygomatic process of the maxilla (right and
left sides averaged) and
b)on the bony anatomical details superior to
the incisors. The superior and inferior
surfaces of the posterior hard palate assist
in orientation, and to minimize the
probability of gross errors in anteroposterior registration
NOTE: PTM fissure of the older tracing
should lies at or behind that of the younger.
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45. Mandible
For the purposes of measuring tooth
movement relative to basal bone, mandibular
regional superimposition commonly is
effected via a mandibular-plane orientation
and a lingual-symphysis registration.
Implant studies, however, suggest that
greater validity can be achieved by using the
mandibular canal, tooth germs (prior to the
initiation of root formation), and the
individual bony architecture in the labial
aspect of the symphysis (Bjork and Skieller, 1983 )
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.
46. Unifortunately, many of these bony
details are often absent, difficult to
see, or distorted by among-series
variation in head placement
mandibular plane can be used as a
substitute orientation line, especially if
there has been minimal growth
between cephalograms
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47. The pattern of craniofacial growth
The main purpose of fiducial lines is to provide a
permanent record of the regional superimpositions used
in the measurement of skeletal and dental change.
When each tracing has been executed in appropriate
detail, ‘fiducial lines’ (arbitrary straight lines several
inches long with registration crosses) are drawn
adjacent to cranial base, maxilla, and mandible of one
tracing.
The fiducial lines have been transferred throughout the
series, they serve not only to record the
superimpositions
to
facilitate
the
process
of
measurement (and, if necessary, re-measurement), but
also to provide a greatly simplified picture of change
seen from the vantage point of any of the three facial
areas.
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48. Eg: the cranial base
fiducial lines are
superimposed, the
separation of the
mandibular and
maxillary fiducial lines
represents the
translatory growth –
both in amount and
angulation – of the jaws
relative to cranial base.
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49. Measurement of change
Although the face undergoes
widespread change during orthodontic
treatment, only effects that are felt at the
level of the occlusion can have a direct
impact on the molar and incisor
relationships.
The occlusion, therefore, represents the
‘bottom line’, the site at which change in the
upper and lower jaws comes together and is
integrated. For this reason, the pitchfork
analysis measures change projected onto
the plane of occlusion.
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50. When a two-film series is to be analysed, the
maxillae are superimposed, and the two FOP(similar
to that of jenkins 1955) then are averaged by
inspection to yield a mean functional occlusal plane
(MFOP), which is passed through to each tracing.
Once the MFOP has been established and
transferred to all tracings in the series, regional
superimposition within cranial base, maxilla, and
mandible is used to measure the various
components of anteroposterior change that make
up the times of the pitchfork.
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51. A)Jaw Growth/ Displacement relative to
Cranial Base
In the anterior cranial base, “wing point” (W, the point
; Wieslander, 1963; SE, Riolo et al., 1974) commonly
serves as a registration point and is used here as the
cranial-base reference point from which maxillary and
mandibular displacement are measured.
To measure displacement of the maxilla relative to
cranial base (MAX), the maxillary fiducial lines are
superimposed and the separation of the W points is
measured parallel to MFOP
Mandible: The separation of D-points (standardized in
the two tracings by mandibular regional
superimposition) is measured parallel to MFOP. This
measurement represents the mandible relative to
maxillary basal bone.
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53. Since the mandible ‘outgrows’ the
maxilla, ABCH commonly is positive
Note: displacement of D-point can be due to
growth, a functional shift, or, more probably,
some mixture of the two.
So Unfortunately, the cephalometric technique
offers no reliable means of differentiating
between the two types of change.
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54. Whatever
its
sign
(and
cause),
mandibular displacement relative to
cranial base (MAND) then can be
estimated by subtraction:
MAND = ABCH – MAX.
Eg:
if the maxilla underwent 3 mm of
forward translatory growth, and the
mandible out-grew it by 4 mm,
MAND = 4 – (-3) = 7 mm.
These three measuerments abstract the
sagittal growth of the jaws and together
with tooth movement account for change
in molar relationship and overjet.
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55. Tooth movement relative to basal bone
The change in overjet and the molar relationship
obtained from summing the individual tines of the
pitchfork
should
be
compared
with
direct
measurements
obtained
from
an
MFOP
superimposition.
The change in molar relationship is measured by
registering on the mesial contact point of one molar
(upper or lower) and then measuring the separation of
the contact point of the other :
The change in overjet, by registering on the averaged
incisal edge of the upper or lower incisors and then
measuring the displacement of the averaged incisal
edge in the other arch.
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56. If the individual components of growth and
tooth movement do not add up to the direct
measurements of change executed at the
occlusal plane (say, to within 0.2-0.3 mm), the
measurements are re-done.
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59. This method of cephalometric analysis is
designed to provide an integrated accounting of
the source – skeletal growth or tooth movement .
Each of the components is measured
separately; however, as a group, they sum to
provide a complete ‘explanation’ of changes in
overjet and molar relationship.
Thus it answers to most of the controversies
such as
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61. 1.Do treatments with functional appliances feature
more skeletal change than do conventional fixedappliance treatments?
2.Does anchorage preparation preserve anchorage?
3.Do ‘Straight wire’ appliances ‘burn’ anchorage?
4.What are the penalties incurred by a failure to use
extra-oral traction? How does the effect of a given
appliance differ in children and adults?
5. Does premolar extraction ‘dish in’ the profile? If so,
how much?
6. What is the apparent impact of normal growth (i.e. of
excess mandibular growth) on tooth movement during
and after treatment. www.indiandentalacademy.com
62. Rush forth, Gordon and Arid (BJO June 1999)
Did a retrospective study involving analyses of preand post-treament cephalograms of 63 Class II
division 1 patients treated with the FR to demonstrate
the relative maxillary, manidibular, incisor, and molar
movements during treatment compared with normal
growth within a control group of untreated 39 Class II
division 1 cases drawn from the same demographic
population.
All cephalograms were digitized and subjected to a
Pitchfork analysis
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63. It was shown that the FR was effective in treating
Class II division 1 cases with the studied group being
corrected to a clinically acceptable overjet and
overbite of 2-3 mm.
The majority of the correction came from dental
movements, the most significant being the
retroclination of the upper incisor teeth (mean
4.1mm, 95 per cent CI ±0.44) and proclination of the
lowers (mean 2.2 mm 95 per cent CI ± 0.57).
As regards skeletal correction, the most significant
contribution was the restraint of normal maxillary
forward growth (mean -0.2mm, 95 per cent CI ± 0.62)
with forward manidiblar growth not being a significant
factor.
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64. Mannchen (switzerland), Ejo
2001
Compared the PFA with the conventional Bjorks
method.
The pitchfork analysis consistently provided an
overestimation of the skeletal effects and an
under-estimation of the dental changes. The
pitchfork analysis is not sufficiently sensitive to
distinguish between the skeletal and dental
effects of orthodontic treatment.
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65. Lysle Johnston, Ejo 2002
Reported that Mannchen was wrong in
his finding because he used the frankforts
horizontal plane (as he was forced by
computerisation) to measure the skeletal
change rather than the MFOP and the
dental change was measured using the
MFOP
Thus the sum of the individual elements
did not equal the molar and Overjet
correction
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66. References:
1. Thomas G M, Valiathan A: A Cephalometric
comparison of South Indian and North Indian
population using six analysis. Dissertation
submitted to mangalore university, June 1993
2.Bhat M, Sudha P, Tandon S: Cephalometric
norms for Bunt and Brahmin children of
Dakshina Kannada based on McNamara’s
analysis. J Indian Soc Pedo Prev Dent ,June
2001 pg 41- 51
3. Johnston LE Jr: An objective evaluation of the pitchfork
analysis (PFA), EJO 2002 vol 24 page 121- 123
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67. 4. R Mannchen: A critical evaluation of the pitch fork
analysis , EJO 2001 vol 23 pg 1- 14
5. CDJ Rushforth, PH Gordon, JC Arid: Skeletal and
Dental changes following the use of Frenkel
Functional Regulator , BJO June 1999 pg 127- 134
6. Johnston LE Jr :Balancing the Books on
Orthodontic Treatment: An integrated Analysis of
Change, BJO 1996 pg 93- 102
7. McNamara, J A Jr: A method of Cephalometric
evaluation. AJO 1984, Dec Vol 86 pg 449- 469
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68. 8.William Proffit: Contemporary Orthodontics
3rd Edition, 2000pg 179- 181
9. Athanasio E Athanasiou: Orthodontic Cephalometry,
1995 pg 269
10. A Jacobson, PW Caufield: Introduction to
Radiographic Cephalometry, 1985
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69. Thank you
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