McNamara Analysis / orthodontic courses by Indian dental academy

Mc NAMARA ANALYSIS

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

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 standards2. selected values from a group of untreated children from the Burlington Research Centre3. 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 analysis1. Maxilla to cranial bone 2. Maxilla to mandible3. Mandible to cranial bone4. Dentition5. 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 valuepost 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 MANDIBLEAnteroposterior relationship

Mid facial length- a line from condylion to pt A

Effective mandibular length-

a 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 dentitionmedium 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 inividuals- 20-23 mm

in medium sized individuals 27-30 mmin 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 angleAngle between the Frankfort horizontal & line drawn

along the lower border of the mandible (Go-Me) Avg 22 deg + 4 deg


Facial axis angleAngle 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)


DENTITIONHelps in determining the

anteroposterior position of both upper and lower incisors.

Maxillary Incisor PositionVertical 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.



93deg normal

-7mm Maxillary skeletal retrution

89

112-114 112 normal

89 normal

23

69 increased

33deg Vertically growing pattern

-2deg

Cant of upper lip102o + 8

0 – 1mm14o + 8 23o normal

65 + 4

26 + 4


-15mm Retrusive mandible

10mm

9mmForwardly placed

13mm

10mmdecreased

-5.5 + 4



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McNamara Analysis / orthodontic courses by Indian dental academy