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

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


INTRODUCTION
Described by James A McNamara in 1984
Jr Professor of Orthodontics, Centre for Human
Growth and development, University of
Michigan.
This analysis helps in the evaluation and
treatment planning of orthodontic and
orthognathic surgery patients



In a normal well balanced occlusion, the skeletal
and dentoalveolar components of jaw
are well related to each other.

Need for this analysis
 It

relates teeth to teeth, teeth to jaws, each
jaw to the other and jaws to the cranial base.
 This analysis can be easily communicated to
lay persons ,such as patients and parents,
and to other dental professionals who do not
have detailed knowledge of cephalometrics.


 The

composite normative standards used in
this analysis were derived from 3 sources;
1. lateral cephalograms 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 Arbor,
having good to excellent facial and dental
configurations and good skeletal balance with
an orthognathic facial profile

LANDMARKS
 ANS

- ant tip of the sharp bony process of
maxilla in the midline of the lower margin of
ant nasal opening
 Co - the most posterosuperior pt on the outline
of mand condyle
 Ba – median pt of the ant margin of the
foramen magnum
 Ptm – contour of pterygomaxillary fissure
formed ant by retromolar tuberosity of maxilla
& posteriorly by ant curve of pterygoid
processof sphenoid bone

 The

craniofacial skeletal complex is divided
into 5 major sections – to create a clinically
useful analysis
1. Maxilla to cranial bone
2. Maxilla to mandible
3. Mandible to cranial bone
4. Dentition
5. Airway


MAXILLA TO CRANIAL BASE
 Soft

tissue evaluation.
1. nasolabial angle
2. cant of upper lip
 Nasolabial angle
is formed by drawing a line tangent to
the base of the nose and a line tangent to the
upper lip
 In adult males & females
102 deg (SD of 8)
 Acute angle due to dentoalv protrusion or
orientation of base of nose

Nasolabial Angle

Cant of upper lip
 Should be slightly
forward to form an
angle with nasion
perpenticular
 14 (SD of 8 )in
women


8 (SD of 8 ) in man


Hard tissue evaluation
 To

determine the anteroposterior orientation
of maxilla, relative to cranial base –linear
distance between N perpendicular and pt A
 Ant position of pt A -- +ve value
post position of pt A -- -ve value
In well balanced face,
0 mm in mixed dentition
1 mm in adult male& female


 Exceptions:
 Nasion

perpenticular variability:
cl III malocclusion – short cranial base.
backward position of N gives an
appearance of excessively anteriorly
positioned max &mand
 Pt A variability:
In cl II div 2 case - excessive lingual
tipping of crowns of upper incisors,so pt A
is 1-2 mm labially placed.

MAXILLA TO MANDIBLE
Anteroposterior relationship
Mid facial length- a line
from condylion to pt A
Effective mandibular lengtha line from Co to Gn
Any effective midfacial
length corresponds to an
effective mand length



The effective lengths max &mand are related to
the size of the component parts .
thus termed ,
small for mixed dentition
medium for adult female
large for adult male
To determine the maxillomandibular difference
the mid facial length is substracted from mand
length (Co-Gn)-(Co-A)
in small inividuals20-23 mm
in medium sized individuals 27-30 mm
in large individuals
30-33 mm


 Vertical

relationship
- lower ant face height
- mand plane angle
- facial axis angle

 Lower

anterior face height
-measured from ANS - Me
-it correlates with the length of midface
-forwardly or backwardly placed chin point
attribute to deficient or excessive lower face
height respectively.

Mandibular plane angle
Angle between the Frankfort horizontal & line drawn
along the lower border of the mandible (Go-Me)
Avg 22 deg + 4 deg


 Facial

axis angle
Angle formed by line constructed from the
posterosuperior aspect of the
pterygomaxillary fissure to Gnathion relative
to the Cranial base (Ba-Na).
In a balanced face- Facial axis angle is
perpendicular.
A –ve value means excessive vertical
growth of face.
A +ve value means deficient vertical
growth of face.

Facial Axis Angle

MANDIBLE TO CRANIAL BASE
 Is

determined by measuring distance from
pogonion to nasion perpendicular.
In mixed dentition
6-8 mm (behind N per)
In adult female
4-0 mm (behind N per)
In adult male
2 mm
(behind or fwd of N per)


DENTITION
Helps in determining the
anteroposterior position of
both upper and lower incisors.
Maxillary Incisor Position
Vertical line is drawn through pt
A parellel to nasion
perpendicular. The distance
from pt A to facial surface of
upper incisor is measured.
The normal value is 4-6 mm.

Mandibular Incisor Position
The distance between
the edge of the
mandibular incisor and a
line drawn from pt A to
pog is measured.
In a well-balanced
face it is 1-3 mm.


AIRWAY ANALYSIS
The purpose of this analysis is to find out the
possibility of any airway impairment.
Upper Pharynx
Is measured from a pt on the post outline of
the soft palate to the closest point on the
pharyngeal wall. The avg nasopharynx is
15-20 mm. A width of 2 mm or less indicate
airway impairment.

Lower Pharynx
Is measured from the pt of intersection of the
post border of the tongue and the inferior
border of the mandible to the closest pt on
the post pharyngeal wall. Avg measurement
is 11-14 mm.


Cant of upper lip

102o + 8
14o + 8
0 – 1mm

112-114
89
26 + 4

65 + 4

93deg
23o

-7mm

112
89
23

69
33deg
-2deg


normal
normal
Maxillary skeletal
retrution

normal
normal

increased
Vertically
growing
pattern

-5.5 + 4

-15mm

10mm
9mm
13mm
10mm


Retrusive
mandible

Forwardly
placed
decreased

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

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