AJEESHA NAIR

McNamara Analysis

Dr JAMES A McNAMARA

1984

INTRODUCTION

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.

In short, the method of analysis described here represents an effort to relate teeth to teeth, teeth to jaws, each jaw to the other, and the jaws to the cranial base.

Skeletal and dental components of the face in normal occlusion

Maxillary skeletal protrusion

Maxillary dentoalveolar protrusion

The method of analysis described here

represents an effort to relate

teeth to teeth,

teeth to jaws,

each jaw to the other, and

the jaws to the cranial base.

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 111young adults from Ann Arbor, having good to excellent facial and dental configurations and good skeletal balance with an orthognathic facial profile

THE COMPOSITE NORMATIVE STANDARDS DERIVED FROM 3 SAMPLES

CR

AN

IOFA

CIA

L S

KELETA

L

CO

MP

LEX

MAXILLA TO CRANIAL BASE

MAXILLA TO MANDIBLE

MANDIBLE TO CRANIAL BASE

DENTITION

AIRWAY

MAXILLA TO CRANIAL BASE

Soft tissue evaluation

Hard tissue evaluation

NASOLABIAL ANGLE

CANT OF UPPER LIP

DRAWING A LINE TANGENT TO THE BASE OF THE NOSE AND A LINE TANGENT TO THE UPPER LIP

FORMS THE NASOLABIAL ANGLE

CANT OF UPPER LIP

FH

NP

.A

Hard tissue evaluation

Relationship of point A to nasion perpendicular

0 mm in mixed dentition 1 mm in adult male& female

Ant position of pt A -- +ve value

Post position of pt A -- -ve value

In well – balanced faces,this measurement is:

0 mm in mixed dentition1 mm in adult females and males.

Exceptions

MAXILLA TO MANDIBLE

Maxilla To Mandible

Anteroposterior relationship

Midfacial length Effective mandibular length Maxillomandibular differential

Any effective midfacial length corresponds to an effective mandibular length .

MID-FACIAL LENGTH

measuring a line from Condylion to point

A.

Condylion- most posterosuperior point

on the outline of mandibular condyle

MANDIBULAR LENGTH

-measuring a line from Condylion to

anatomic Gnathion

Gnathion – most anteroinferior aspect of

the mandibular symphysis.

Point A

Gnathion

Condylion

The effective lengths of 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

The Maxillomandibular Difference : In small individuals: 20-24 mm,

In medium sized individuals: 25-28 mm In large individual : 29-33 mm

Gn

•A

VARIATIONS

LOWER ANTERIOR FACIAL

HEIGHT

MANDIBULAR PLANE ANGLE

FACIAL AXIS ANGLE

VERTICAL RELATIONSHIP

If LAFH - retrognathic mandible.

If LAFH prognathic mandible

measured from). anterior nasal spine(ANS) to

Menton(Me

Increases with age.

Correlated to the effective length of the

midface.

Lower anterior facial height

It is the angle between anatomic FH and the line drawn along the lower border of the mandible through constructed Gonion(Go) and Menton(Me).

Average is 22 ± 4 degrees.

- Excessive lower facial height

- Deficiency in lower facial height.

MANDIBULAR PLANE ANGLE

It is formed by a line constructed from the posterosuperior aspect of the pterygomaxillary fissure (PTM) to gnathion(Gn) and a line perpendicular to cranial base (ie a line from basion(Ba) to nasion(N).

An ideal relationship is when PTM-Gn lies on the perpendicular(0 degrees).

If PTM-Gn lies anterior to the perpendicular, the angle is positive, suggesting deficient vertical development of face and vice versa.

Facial Axis Angle of Ricketts

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 0-4 mm (behind N per)

In adult male 2 mm(behind to 5 mm fwd of N per)

DENTITI0N

Helps in determining the antero-posterior position of both upper and lower incisors

Ideal distance measured horizontally from point A to the facial surface of maxillary incisors is 4 to 6 mm

Relating the upper incisor to maxilla

Anteroposterior position:

Measurement of the

facial surface of the lower

incisor to the A-Pogonion

line.

Normal = 1 - 3 mm

Relating lower incisor to mandible

In vertical position mandibular incisors are related to functional occlusal plane.

If curve of Spee is excessive incisors intruded or molars ExtrudedLAFH is the determining factor

AIRWAY ANALYSIS

Upper pharynx

Two measurements are used to examine the possibility of airway impairment.

Lower pharynx

It is measured from a point on the posterior outline of the soft palate to the closest point on the posterior pharyngeal wall.

Normal(adults) - 17.4 mm

Increases with age

UPPER PHARYNGEAL WIDTH

It 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.

Normal – 10 – 12mm

Does not change with age

LOWER PHARYNGEAL WIDTH

SIGNIFICANCE

Adenoid obstruction of upper airway –

upper pharyngeal width decreases.

Lower pharyngeal width –greater than

15 mm

-anterior positioning of tongue –

habitual or

enlargement of tonsils .

McNamara Analysis

1. Maxilla to cranial base

Normal Patient Inference

Nasolabial Angle 102±8˚ 110˚ Normal upper lip

Cant of upper lip 14±8˚ 8˚ Normal upper lip

Point A to N-perpendicular

0-1mm -9mm retrusive maxilla

2.Maxilla to mandible

Normal Patient value

Inference

Anteroposterior

Maxillary Length

100.9 103mm

Maxillary length normal

Mandibular Length

131mm 127mm(136-139)

decreased mandibular length

Maxillomandibular differential

30mm 24mm decreased

Vertical

LAFH(ANS-Me) 71.6mm

67mm Reduced

Mandibular Plane Angle(FH-Go-Me)

22± 4˚ 34˚ VGP

Facial Axis Angle

0±3.5˚ -7˚ VGP

Normal Patient Value

Inference

3.Mandible to cranial base

Pog to N-perpendicular

0-4mm -13mm

Backwardly placed chin

4.Dentition

Maxillary incisor to point A

4-6mm 7mm Protrusive upper incisor

Mandibular incisor to A-p0g

1-3mm 5mm Protrusive lower incisor

5.Airway

Upper pharynx 15-20mm

17mm Normal upper pharyngeal width

L0wer pharynx 11-14mm

12mm Normal lower pharyngeal width

ReferencesRadiographic Cephalometry-Jacobson

2nd editionAJO-DO 1984 Dec (449-469)-McNamara

Thank you…….