Mc Namara Analysis. / orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY

Leader in continuing dental education www.indiandentalacademy.com

www.indiandentalacademy.com

Mc NAMARAMc NAMARAANALYSISANALYSISwww.indiandentalacademy.com

INTRODUCTIONINTRODUCTIONDr James. A. McNamara.. described a method of cephalometric analysis which is used in the evaluation and treatment planning of orthodontic and orthognathic surgery patientsThe analysis represents an effort to relate… Teeth to teeth Teeth to jaws Each jaw to the other Jaws to the cranial base


Composite Normative Standards Are Based On..Bolton's StandardsBurlington Orthodontic Research CentreAnn 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

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

In the decade from 1970 - 1980


s

po

Ba

Co

Or

N

ANSA

Ptm

Me GnPog

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

Orbital- lowermost point on the orbitBasion- lowest point on the foramen magnum in the median planePtm-

Go


s

po

Ba

Co

Or

N

ANSA

Ptm

Me GnPog

Landmarks And Planes : ANS- Tip of the bony anterior nasal spinePoint A- Deepest point on the curved bony outline ( subspinale )Pogonion- Most anterior point on the bony chinMenton- Lowest point on the outline of the symphysisGonion- Constructed by intersection of the lines tangent to the posterior margin of the ascending ramus & the lower border

Go


s

po

Ba

Co

Or

N

ANSA

Ptm

Me GnPog

Landmarks And Planes :Gnathion- Constructed by intersecting a line drawn perpendicularly to the line connecting Me and PogCondylion- Most posterosuperior point on the outline of the condyleMandibular plane – Go – Me Facial axis – Ptm – Gn

Go


Craniofacial Skeletal Complex Is Divided Into Five Major Sections… Maxilla to Cranial base Maxilla to Mandible Mandible to Cranial base DentitionAirway


Relating Maxilla To The Cranial BaseHard tissue evaluation:

Linear distance is measured Between nasion perpendicular to point A

0 mm – in mixed dentition1 mm – in adults

po or

N

1 mm

FH


Maxillary Skeletal Protrusion

Maxillary Skeletal RetrusionWith Obtuse Nasolabial Angle www.indiandentalacademy.com

Relating Maxilla To The Cranial BaseSoft Tissue Evaluation:

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


Relating Maxilla To The Cranial BaseSoft Tissue Evaluation:Cant Of Upper Lip :Female – 14 degreeMale – 8 degree( SD 8 0 )

N Perpendicular


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

Effective mandibular length :Measured from Condylion to gnathion www.indiandentalacademy.com

Any given effective midfacial length corresponds to a given effective mandibular lengthMandibular length – Midfacial length = Maxillomandibular differential

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


Small : 20 mm Medium : 25 to 27 mm

Large : 30 to 33 mmwww.indiandentalacademy.com

CLASS II DIV 1Mandible 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 www.indiandentalacademy.com

60 – 62 mm

66 – 68 mm

70 – 74 mmwww.indiandentalacademy.com

Vertical maxillary excess can cause a downward and backward rotation of mandible resulting in an increase in lower anterior face height and vice – versaAn increase or decrease in the lower anterior face height can have a profound effect on the horizontal relationship of the maxilla and mandibleIf the lower anterior face height is increased then the mandible will appear to be more retrognathic and vice - versa www.indiandentalacademy.com


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 Gn900

< 900 – ( -ve value ) excessive vertical development> 900 – ( +ve value ) deficient vertical development www.indiandentalacademy.com

Relating Mandible To The Cranial BaseDistance from Pog to the nasionPerpendicular


- 8 mm to – 6 mm

- 4 mm to 0 mm

- 2 mm to 2 mmwww.indiandentalacademy.com

Mandibular Skeletal

Mandibular PrognathismRetrusion


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 basewww.indiandentalacademy.com

N

A


Relating upper Incisor to Maxilla :Anteroposterior positionPosition of the upper incisor can be located by using measurement that relate dental portion of maxilla to the skeletal portionLine parallel to nasion perpendicular through point A Distance from point A

er

To the facial surface of upper incisor is measuredwww.indiandentalacademy.com

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 lineNormal : 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 madeThe tracing is moved so that the mandible is in the desired position relative to the maxillaA new A – Pog line is drawnThe incisor is expected to lie 1 – 2 mm anterior to the constructed linewww.indiandentalacademy.com

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


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

rswww.indiandentalacademy.com

Airway :Upper pharynxWidth is measured from a point on the posterior outline of the soft palate to the closest point on the posterior pharyngeal wallAverage : 15 - 20 mm


2 mm


Airway :Lower pharynxWidth 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 wallAverage : 10 – 12 mm



Advantages :Linear measurements rather than anglesProvides guidelines with respect to normally occurring growth incrementsThe method is more sensitive to the vertical changesEasily explained to non specialist and lay persons such as patients and parents



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Mc Namara Analysis. / orthodontic courses by Indian dental academy