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

Mc Namara Analysis
Ricketts Analysis
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Introduction
Since the introduction of cephalometrics
by Broadbent in 1931, a number of
different analyses have been devised.
Most of the analyses were conceived
during the period (1940 to 1970) when
significant alterations in craniofacial
structural relationships were thought
impossible………...

But from 1970’s clinical orthodontics
has seen the advent of numerous
orthognathic surgery procedures which
allow three-dimensional repositioning of
almost every bony structure in the facial
region. Therefore, a need has arisen 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 jaw elements and
cranial base structures one to another.

Mc Namara Analysis

•
•
•
•

In this method of analysis described by
Mc Namara in his article on AJO-DO 1984
represents an effort to relate
teeth to teeth
teeth to jaws
each jaw to the other
the jaws to the cranial base.

Advantages
1. This method depends primarily upon
linear measurements rather than angles,
so that treatment planning (particularly
treatment planning for the orthognathic
surgery patient) is made easier.


Advantages (contd.)
2. This method of analysis is more sensitive to
vertical changes than is an analysis which relies
on the ANB angle, such as that of Steiner. The
use of the ANB angle can be misleading, since it
tends to be insensitive to the vertical component
of jaw discrepancies. Similarly, changes in
growth pattern, which include both horizontal
and vertical adaptations, may be completely
missed if only a change in the ANB angle is
measured.

Advantages (contd.)
3. This analytical procedure provides
guidelines with respect to normally
occurring growth increments. Therefore,
the norms derived from the Bolton
standards, the Burlington sample, and the
Ann Arbor sample and the composite
norms presented in this article can be
used to evaluate treatment results.

Advantages (contd.)
4. The principles of this analysis are easily
explained to nonspecialists and to lay
persons such as patients and parents.


Normative Standards
Normative standards were determined
by arbitrarily combining comparable
average values of three samples.
• The first sample contains normative data
derived from lateral cephalograms of the
children comprising the Bolton standards,
the longitudinal records of whom were
retraced and digitized by Behrents and
McNamara to include all the landmarks
necessary for the present analysis.

• The second sample contains selected
values from a group of normal children
from the Burlington Orthodontic Research
Centre who also were followed
longitudinally.
• The third group considered is the Ann
Arbor sample of 111 young adults who
had good to excellent facial configurations.
Patients in this latter group had a Class I
occlusion and good skeletal balance with
an orthognathic facial profile.

Contents
1.
2.
3.
4.

Relating Maxilla To Mandible
Relating Mandible To Maxilla
Relating the mandible to the cranial base
Relating the upper incisor to the maxilla

5. Relating the lower incisor to the mandible

6. Airway analysis


Relating Maxilla To Mandible
1. Hard Tissue Evaluation
2. Soft tissue Evaluation


Hard Tissue Evaluation
• The anteroposterior orientation of the
maxilla relative to the cranial base can be
determined by measuring the linear
distance between Nasion perpendicular
and point A.


HARD TISSUE EVALUATION:
NASION PERPENDICULAR

F-H Plane is drawn
Nasion Perpendicular
from superior aspect
is a veritcal line
of the external
Perpendicular to FHP
auditory inferiorly
extendingmeatus to
the nasion
fromlower border of
the orbit


Ajo-Do 1984

Cephalometric values from Ann Arbor sample

Composite Norms


Examples
Maxillary skeletal protrusion

Maxillary skeletal retrusion


Soft Tissue Analysis
The nasiolabial angle is formed
By drawing a line tangent to the
base of the nose and a line
tangent to the upper lip

The ideal value is 102° ± 8°


Examples
Maxillary protrution

Maxillary retrusion


Retrusion with normal
Nasolabial angle

The cant of the upper lip Should be
slightly forward to form an angle of
14°± 8° in females and 8°± 8° in
adult males with the
Nasion perpendicular


Relating Mandible To Maxilla
1. Anteroposterior Relationship
2. Vertical Relationship


Anteroposterior Relationship
Of Mandible With Maxilla
A geometric relationship exists between
the effective length of the midface and that
of the mandible.
Any given effective midfacial length
corresponds to a given effective
mandibular length.


The effective midfacial length
is determined by measuring a
line from condylion to point A

Condylon is the most
Gnathion is the most
posterosuperior point
anteroinferior aspect of
on the outline
the mandibular of the
mandibular condyle
symphysis
The effective mandibular
length is derived by
constructing a line from
condylion to anatomic
gnathion

Composite Norms


Ajo-Do 1984

Ajo-Do 1984

Bolton Standards


Ajo-Do 1984

Burligton Values


• The effective lengths of midface and
mandible described in the analysis is not
age or sex dependent but related to size
of the component parts. So the term
"small” "medium," and "large" are used
rather than "mixed dentition," "adult
female" and "adult male."


Examples
Retrusive mandible

Protrusive mandible


Retrusive maxilla
Protrusive mandible

Vertical Relationship
lower anterior facial height is
measured from anterior nasal
spine to menton.
This linear measurement
increases with age and is
correlated to the effective length
of the midface


Composite Norms

Ajo-Do 1984

Mixed dentition

Adult Female

Adult Male


Examples
Increase in vertical height

Decrease in vertical height


The Mandibular Plane Angle

26° ± 4.5° at 9 years and decreases by 1°
every 3 years


The Facial Axis
Average value is 90 °± 3.5 ° .
Excessive vertical development is
indicated by negative values (values
less than 90°), and deficient vertical
facial development is indicated by
positive values (values greater than
90°).


Examples
Retrusive Mandible

Protrusive mandible


Relating the mandible to the
cranial base


• The relationship of the mandible to the
cranial base is determined by measuring
the distance from Pogonion to the Nasion
perpendicular.


EXAMPLES
Protrusive

Retrusive


Relating the upper incisor to
the maxilla
1. Anteroposterior position
2. Vertical position


Anteroposterior position
• The 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.


Ajo-Do 1984

This is accomplished by drawing a
vertical line through point A,
parallel to the nasion perpendicular.
The distance from this constructed
The measurement from
point AA to the facial surface
point perpendicular to the facial
surfaceupper incisor incisor is
of the of the upper horizontally
measured.

is 4 to 6 mm


Vertical
• The vertical position of the upper
incisor is best determined at the time of
the clinical examination.
• Typically, the incisal edge of the upper
incisor lies 2 to 3 mm below the upper
lip at rest.


It is in the range of 2 to 3 mm.
Women show more within this
range


Relating the lower incisor to
the mandible
1. Anteroposterior position
2. Vertical position


Anteroposterior position
• The anteroposterior position of the lower
incisor can be determined by using a
measurement of the facial surface of the
lower incisor to the A-pogonion line


Ajo-Do 1984

Composite Value is 1 to 3 mm


Airway analysis
1. Upper pharynx
2. Lower pharynx


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 measurement is taken on the anterior half
of the soft palate outline because the area
immediately adjacent to the posterior opening of
the nose is critical in determining upper
respiratory patency.

Average Value is approximately
15 to 20 mm in width


Lower pharynx.
Lower pharyngeal width is measured
from the intersection of the posterior
border of the tongue and the inferior
border of the mandible to the closest point
on the posterior pharyngeal wall.


Average Value is 11 to 14 mm.
A greater than average value
suggests anterior positioning
of the tongue


Ricketts Analysis


Relation of the Mandible
1. Facial axis
2. Facial(depth)angle
3. Mandibular plane

1. Facial Axis
• The angle formed between the basionnasion plane and the plane from foramen
rotundum (PT) to gnathion.


Facial axis isPt line
a point
extending from the the
The junction of
•A foramen rotundum (Pt) a
lesser angle suggests to
pterygomaxillary
gnathion
retropositioned chin, whereas
fissure and the
an angle greaterrotundum
foramen than a right
The outline of protrusive or
angle suggests athe
foramen rotundum
forward growing chin can
be angle formed
The approximated at the
10.30 (face basionbetween the of a clock)
position on and the
nasion plane the circular
outline of foramen
plane from the superior
border of the
rotundum (PT) to
pterygomaxillary fissure
gnathion is 90 ± 3.5°

2.Facial(depth)angle
• The angle between the facial plane (NPog) and the Frankfort horizontal.
• This angle provides some indication of the
horizontal position of the chin.
• It also suggests whether a skteletal Class
II or III pattern is due to the position of the
mandible


This angle is 87 ± 3° at 9 years
of age and it has to be
Facial plane
increased by 1 every 3 years
Extends from Nasion to
Pogonion
Facial angle is formed between
facial plane (N-Pog) and the
Frankfurt horizontal line


3.Mandibular Plane
• A high or steep mandibular plane angle
implies that an open bite may be due to
the skeletal morphologic characteristics of
the mandible. A low mandibular plane
suggests the opposite (ie, a deep bite).


Mandibular plane
Extends from gnathion to gonion

26. 60° ± 4.5° at 9 years and decreases by 1°
every 3 years


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 2.0 mm and
decreases 1 degree every 5
years


II.Convexity At Point A
• High Convexity implies a Class II skeletal
pattern. Negative Convexity suggests a
Class III skeletal pattern.


Dentition


Lower incisor to A-Pog
• The A-Pog plane is referred to as the
denture plane and is a useful reference
line from which to measure the position of
the anterior teeth.


A-Pog Line
Extends from point A to Pogonion

Ideally, the lower incisor should be
located 1.0 ± 2 mm ahead of the APog line . This measurement is used to
define the protrusion of the lower arch.


A-Pog Line
• If the measured value of lower incisor to
A-Pog line is more than the average value
then extraction is indicated.


Upper Molar To PtV
• This measurement assists in determining
whether the malocclusion is due to the
position of the upper or lower molar. It is
also useful in deciding whether extractions
are necessary.


Pterygoid Vertical(PtV)
A vertical line drawn throgh distal
radiographic outline of the
pterygomaxillary fissure and
perpendicular to FHP

The distance from the pterygoid
vertical (back of the maxilla) to
the distal of the upper molar.
On average is measured,
This measurement should equal
the age of the patient +3.0 mm
(eg, a patient 11 years of age
has a norm of 11 + 3 = 14 mm).

Lower incisor to A-Pog
• This measurement provides some idea of
lower incisor procumbency


The angle between the long axis of the
lower incisor and the A-PO plane (1 to APO) is measured.
On the ayerage, this angle should be 28
± 4°.


Profile


Lower lip to E-plane
• The distance between the lower lip and
the esthetic (nose-chin) plane is an
indication of the soft tissue balance
between the lips and the profile


Esthetic line (E-line)
Extends from soft tissue tip of
nose(En) to soft tissue Chin
point(DT)
• The average norm for this
measurement is -2.0 mm at 9
years of age. The positive
values are those ahead of the Eline.


Condylar Axis and
Corpus Axis
• These are used to describe the morphology
of the mandible


Xi Point
Locate FHP and Draw PtV Plane
R1 is the deepest point on the
perpendicular to the FHP and anterior
R2 is located on the posterior border
borderfour R1, R2, R3,
of the ramus
locateramus ,opposite & R4
of thethe deepest pointR1 the
R3 is
of
sigmoid notch R3 on the
R4 is opposite
inferior border of the mandible
Construct four Planes tangent to thes
Xipoints can beforms a rectangle enclosing
point and it located at the center
ofthe ramus
the rectangle at the intersection
of the diagonals


Condyle (Dc) point
The point In the center of the
the condyle neck along the
Ba-N plane
Condylar Axis extends
from Xi to Dc

Suprapogonion (PM) point
Corpus axis extends shape
The point at which thefrom
Xi to symphysis
of the PM point mentalis
changes from convex to concave


Thank you


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

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