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INDIAN DENTAL ACADEMY Leader in continuing dental education


INTRODUCTION Dr James. A. McNamara.. described a method of cephalometric analysis which is used in the evaluation and treatment planning of orthodontic and orthognathic surgery patients The 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


Burlington Ann

Orthodontic Research Centre

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 In the decade from 1970 - 1980 Advent

of numerous Orthognathic surgery procedures which allow three dimensional repositioning of almost every bony structure in the facial region


appliance therapy which present new possibilities in the treatment of skeletal discrepancies

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


s po


Ptm Or

Ba A

Orbital- lowermost point on the orbit Basion- lowest point on the foramen magnum in the median plane Ptm-


Go Pog Me Gn

Landmarks And Planes : ANS- Tip of the bony anterior nasal spine Point A- Deepest point on the curved bony outline ( subspinale ) Pogonion- Most anterior point on the bony chin Menton- Lowest point on the outline of the symphysis Gonion- Constructed by intersection of the lines tangent to the posterior margin of the ascending ramus


s po


Ptm Or

Ba A


Go Pog Me Gn

Landmarks And Planes : Gnathion- Constructed by intersecting a line drawn perpendicularly to the line connecting Me and Pog Condylion- Most posterosuperior point on the outline of the condyle


s po


Ptm Or

Ba A


Mandibular plane – Go – Me Go Pog

Facial axis – Ptm – Gn

Me Gn

Craniofacial Skeletal Complex Is Divided Into Five Major Sections… 

Maxilla to Cranial base

Maxilla to Mandible

Mandible to Cranial base



Relating Maxilla To The Cranial Base N

Hard tissue evaluation: po

Linear distance is measured



1 mm

Between nasion perpendicular to point A 0 mm – in mixed dentition 1 mm – in adults

Maxillary Skeletal Protrusion

Maxillary Skeletal Retrusion With Obtuse Nasolabial Angle

Relating Maxilla To The Cranial Base Soft 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 Base Soft Tissue Evaluation: N Perpendicular

Cant Of Upper Lip : Female – 14 degree Male – 8 degree ( SD 8 0 )

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

Effective mandibular length : Measured from Condylion to gnathion

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

Small : 20 mm

Medium : 25 to 27 mm

Large : 30 to 33 mm

CLASS II DIV 1 Mandible 12 mm deficient

Relating Maxilla To The Mandible: Vertical Relationship : Lower Anterior Face Height : ď śMeasured

from ANS to Menton

ď śIncreases

with age and is correlated

With effective midfacial length

66 – 68 mm

60 – 62 mm

70 – 74 mm


maxillary excess can cause a downward and backward rotation of mandible resulting in an increase in lower anterior face height and vice – versa An

increase or decrease in the lower anterior face height can have a profound effect on the horizontal relationship of the maxilla and mandible If

the lower anterior face height is increased then the mandible will appear to be more retrognathic and vice - versa

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 Gn 900 < 900 â&#x20AC;&#x201C; ( -ve value ) excessive vertical development > 900 â&#x20AC;&#x201C; ( +ve value ) deficient vertical development

Relating Mandible To The Cranial Base Distance from Pog to the nasion Perpendicular

- 8 mm to â&#x20AC;&#x201C; 6 mm

- 4 mm to 0 mm

- 2 mm to 2 mm

Mandibular Skeletal Retrusion

Mandibular Prognathism

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


measurement of upper incisor to the N – A line is valid only if the maxilla is in neutral position anteroposteriorly relative to the cranial base



Relating upper Incisor to Maxilla : Anteroposterior position Position of the upper incisor can be located by using measurement that relate dental portion of maxilla to the skeletal portion Line parallel to nasion perpendicular through point A Distance from point A er To the facial surface of upper incisor is measured

Vertical position : The incisal edge of the upper incisor lies 2 â&#x20AC;&#x201C; 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 â&#x20AC;&#x201C; Pog line Normal : 1 mm to 3 mm anterior



ď śIf

there is a discrepancy in Anteroposterior or vertical positioning of the maxilla and the mandible then modifications in this measurement procedure is necessary

ď śTo

predict Anteroposterior position of the incisor after functional or surgical intervention

A second tracing of the mandible and the incisor is made The tracing is moved so that the mandible is in the desired position relative to the maxilla A new A â&#x20AC;&#x201C; Pog line is drawn The incisor is expected to lie 1 â&#x20AC;&#x201C; 2 mm anterior to the constructed line

Estimate the number of mm that the mandible will be brought forward relative to the maxilla at the end of the treatment Then a new point A is constructed the same number of mm in the opposite direction Post treatment A â&#x20AC;&#x201C; Pog line

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

Airway : Upper pharynx Width is measured from a point on the posterior outline of the soft palate to the closest point on the posterior pharyngeal wall Average : 15 - 20 mm

2 mm

Airway : Lower pharynx Width 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 wall Average : 10 â&#x20AC;&#x201C; 12 mm

Advantages : Linear measurements rather than angles Provides guidelines with respect to normally occurring growth increments The method is more sensitive to the vertical changes Easily explained to non specialist and lay persons such as patients and parents

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