Mc namara analysis. /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


Mc NAMARA
ANALYSIS


INTRODUCTION
Dr James. A. McNamara..
described a method of cephalometric analysis which is
used in the evaluation and treatment planning of
orthodontic and orthognathic surgery patients
The analysis represents an effort to relate…


Teeth to teeth



Teeth to jaws



Each jaw to the other



Jaws to the cranial www.indiandentalacademy.com
base

Composite Normative Standards
Are Based On..
Bolton's

Standards

Burlington
Ann

Orthodontic Research Centre

Arbor sample of 111 young adults

(Female – 26 yrs 8 mon, Male – 30 yrs 9 mon )

The analysis method is derived in part from the
principles of cephalometric analyses of Ricketts
and Harvold

Why Another Analysis ?
1940 – 1970 : Significant alteration in the craniofacial
relationship were thought impossible
In the decade from 1970 - 1980
Advent

of numerous Orthognathic surgery procedures
which allow three dimensional repositioning of almost
every bony structure in the facial region

Functional

appliance therapy which present new
possibilities in the treatment of skeletal discrepancies

Landmarks And Planes :
Nasion- Most anterior point
on Nasofrontal Suture
Porion- Superior aspect of
the external auditory meatus

N

s
po

Co

Ptm
Or

Ba
A

Orbital- lowermost point on
the orbit
Basion- lowest point on the
foramen magnum in the
median plane

ANS

Go

Ptmwww.indiandentalacademy.com

Pog
Me Gn

ANS- Tip of the bony
anterior nasal spine
Point A- Deepest point on the
curved bony outline
( subspinale )
Pogonion- Most anterior point
on the bony chin
Menton- Lowest point on the
outline of the symphysis

N

s
po

Co

Ptm
Or

Ba
A

ANS

Go

Gonion- Constructed by
intersection of the lines
tangent to the posterior
margin of the ascending ramus

Pog
Me Gn

Gnathion- Constructed by
intersecting a line drawn
perpendicularly to the line
connecting Me and Pog

N

s
po

Condylion- Most
posterosuperior point on the
outline of the condyle

Co

Ptm
Or

Ba
A

ANS

Mandibular plane – Go – Me
Go
Pog

Facial axis – Ptm – Gn

Me Gn


Craniofacial Skeletal Complex Is
Divided Into Five Major Sections…


Maxilla to Cranial base



Maxilla to Mandible



Mandible to Cranial base



Dentition

Airway


Relating Maxilla To The Cranial
Base
N

Hard tissue evaluation:
po

Linear distance is measured

FH

or

1 mm

Between nasion
perpendicular to point A
0 mm – in mixed dentition
1 mm – in adults

Maxillary Skeletal Protrusion

Maxillary Skeletal Retrusion
With Obtuse Nasolabial Angle


Base
Soft Tissue Evaluation:
Nasolabial Angle:
Formed by line drawn tangent
to the base of the nose and a
line tangent to the upper lip


Base
Soft Tissue Evaluation:
N Perpendicular

Cant Of Upper Lip :
Female – 14 degree
Male – 8 degree
( SD 8 0 )


Relating Maxilla To The Mandible:
Anteroposterior Relationship:
Effective Midfacial Length :
Measured from Condylion to
point A

Effective mandibular length :
Measured from Condylion to
gnathion

Effective lengths are not age or sex related
but are related to size of component parts
Small - Mixed dentition
Medium - Adult female
Large - Adult male
Any given effective midfacial length corresponds to a
given effective mandibular length
Mandibular length – Midfacial length =
Maxillomandibular differential

Small : 20 mm

Medium : 25 to 27 mm

Large : 30 to 33 mm

CLASS II DIV 1
Mandible 12 mm deficient

Relating Maxilla To The Mandible:
Vertical Relationship :
Lower Anterior Face Height :
Measured

from ANS to Menton

Increases

with age and is correlated

With effective midfacial length


66 – 68 mm

60 – 62 mm

70 – 74 mm


Vertical

maxillary excess can cause a downward
and backward rotation of mandible resulting in an
increase in lower anterior face height and vice –
versa
An

increase or decrease in the lower anterior face
height can have a profound effect on the horizontal
relationship of the maxilla and mandible
If

the lower anterior face height is increased then
the mandible will appear to be more retrognathic
and vice - versa


Mandibular Plane Angle :
Angle between FH plane and
the Mandibular plane
( Gonion – Menton )
220 + 40


Facial Axis Angle :
Angle between a line from
basion to nasion and the
facial axis i.e. PTM to Gn
900
< 900 – ( -ve value ) excessive
vertical development
> 900 – ( +ve value ) deficient
vertical development


Relating Mandible To The Cranial
Base
Distance from Pog to the nasion
Perpendicular


- 8 mm to – 6 mm

- 4 mm to 0 mm


- 2 mm to 2 mm

Mandibular Skeletal

Mandibular Prognathism

Retrusion


Dentition :
In

cases of malrelationship between the maxillary
and mandibular skeletal structures, errors may result if
the position of the upper incisor is determined by any
measurement that uses mandible as a reference point
e.g. A – pogonion line

A

measurement of upper incisor to the N – A line is
valid only if the maxilla is in neutral position
anteroposteriorly relative to the cranial base


N

A


Relating upper Incisor to Maxilla :
Anteroposterior position
Position of the upper incisor can be located by
using measurement that relate dental portion of
maxilla to the skeletal portion
Line parallel to nasion
perpendicular through
point A
Distance from point A er
To the facial surface of
upper incisor is measured

Vertical position :
The incisal edge of the upper incisor lies 2 –
3 mm below the upper lip at rest

Vertical position of the upper lip is best
determined at the time of clinical
examination


Relating Lower Incisor To
Mandible :
Anteroposterior position :
Measurement of the facial
surface of the lower
incisor to the A – Pog line
Normal : 1 mm to 3 mm
anterior

A

Pog


If

there is a discrepancy in Anteroposterior or
vertical positioning of the maxilla and the
mandible then modifications in this measurement
procedure is necessary

To

predict Anteroposterior position of the incisor
after functional or surgical intervention


A second tracing of the mandible
and the incisor is made
The tracing is moved so that the
mandible is in the desired
position relative to the maxilla
A new A – Pog line is drawn
The incisor is expected to lie 1 – 2
mm anterior to the constructed
line


Estimate the number of mm that the
mandible will be brought forward
relative to the maxilla at the end of the
treatment
Then a new point A is constructed the
same number of mm in the opposite
direction
Post treatment A – Pog line


Vertical Position Of The Lower
Incisor :
Relating the lower incisor tip to the functional
occlusal plane
Evaluated on the basis of existing lower anterior
facial height
Excessive Curve of Spee…
LAFH is normal or excess – Intruded
LAFH is inadequate – Eruption of the
Molars

Airway :
Upper pharynx
Width is measured from a point on the
posterior outline of the soft palate to the
closest point on the posterior pharyngeal
wall
Average : 15 - 20 mm


2 mm


Airway :
Lower pharynx
Width is measured from intersection of
the posterior border of tongue and the
inferior border of the mandible to the
closest point on the posterior pharyngeal
wall
Average : 10 – 12 mm


Advantages :
Linear measurements rather than angles
Provides guidelines with respect to normally
occurring growth increments
The method is more sensitive to the vertical
changes
Easily explained to non specialist and lay
persons such as patients and parents


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