CEPHALOMETRICSBy

Shameel ahmed shariff

Introduction Assessment of cranio-facial structures forms a

part of orthodontic diagnosis. Craniometry can be said to be the forerunner

of cephalometry. Craniometry involved measurements of cranio

facial dimensions of skulls of dead persons. This method was not practical in living

individual due to soft tissue envelope that made direct measurement difficult and far reliable.

Types

Lateral cephalogram; provides lateral view of skull.

Frontal cephalogram; provides anteroposterior view of skull.

Uses

Helps in orthodontic diagnosis. Helps in classification of skeletal and

dental abnormalities. Helps in planning treatment of an

individual. Helps in evaluation of treatment results. Helps in predicting growth related

changes.

Technical aspect Cephalometric radiographs are taken using

an apparatus that consist of an x ray source and an head holding device called cephalostat.

Cephalostat consists of two ear rods preventing movement of head.

Vertical stabilisation of head is by orbital pointer contacting lower border of orbit.

Upper part of face is supported by forehead clamp positioned above the region of nasal bridge.

The distance between the x ray source and mid saggital plane of the patient is fixed at 5 feet.

Thus the equipment helps in standardising the radiographs.

S Sella: the midpoint of Sella Turcica N Nasion: the extreme anterior point on the

frontonasal suture sna Spina nasalis anterior: the extreme anterior point

on the maxilla snp Spina nasalis posterior: the extreme posterior

point on the maxilla Pt Pterygoid point: the extreme superior point of the

pterygopalatine fossa

A

Point A: the deepest point in the curvature of the maxillary alveolar process

B

Point B: the deepest point in the curvature of the mandibular alveolar process

Pg

Pogonion: the extreme anterior point of the chin Me

Menton: the extreme inferior point of the chin Gn

Gnathion: the midpoint between pogonion and menton

Go

Gonion: the midpoint of the mandibular angle between ramus and corpus mandibulae

O

Opisthion: the posterior border of foramen magnum Ba

Basion: the anterior border of foramen magnum Cd

Condylion: the extreme superior point of the condyle Fc

Fossa cranialis: the intersection between the sphenoidal plane and the larger wing of the sphenoid

L

Lambda: the midpoint of the lambdoid suture on the external cranial contour

Downs analysis;

It is one of the most frequently used cephalometric analysis.

Downs analysis consists of ten parameters of which five are skeletal and five are dental.

Skeletal parameters;

Facial angle;

it is the inside inferior angle formed by intersection of nasion-pogonion plane and F.H. plane.

average value; 87.8’ ( 82 – 95’)

significance; indication of antero- posterior positioning of mandible in relation to upper face. Angle is increased in skeletal class III with prominent chin while decreased in skeletal class II.

Angle of convexity;

Nasion-point A to point A – pogonion.

Average value; 0’ ( -8.5 to 10’).

Significance; A positive angle suggest a prominent maxillary denture bace in relation to mandible.

Negative angle is indicative of prognathic profile.

A-B plane angle;

point A – point B to nasion – pogonion.

Average value; -4.6’ ( -9 to 0’)

Significance; indicative of maxillo mandibular relationship in relation to facial plane.

Negative since point B is positioned behind point A.

Positive in class III malocclusion.

Mandibular plane angle;

Intersection of mandibular plane with F.H. Plane.

Average value; 21.9’ ( 17 to 28’)

Y-Axis;

Sella gnathion to F.H. plane.

Average value; 59’ ( 53’ to 66’)

Angle is larger in class II facial patterns. Indicates growth pattern of a individual.

DENTAL PARAMETERS Cant of occlusal plane;

OCCLUSAL PLANE TO F.H. Plane

Average value; 9.3 ( 1.5 to 14’)

Gives a measure of slope of occlusal plane relative to F.H. Plane.

Inter incisal angle;

Angle between long axes of upper and lower incisors.

Average value: 135.4’ ( 130 to 150.5’)

increased in class I bimaxillary protrusion.

Incisor occlusal plane angle;

This is the inside inferior angle formed by the intersection between the long axis of lover central incisor and the occlusal plane and is read as a plus or minus deviation from a right angle

Average value: 14.5” ( 3.5 to 20’)

An increase in this angle is suggestive of increased lover incisor proclination.

• Incisor mandibular plane angle:

This angel is formed by intersection of the long axis of the lower incisor and the mandibular plane.

Average value: 1.4’(-8.2 to 7’)

An increase in this angle is suggestive of increased lower incisor proclination.

Upper incisor to A-pog line:

This is a linear measurement between the incisal edge of the maxillary central incisor and the line joining point A to pogonion. This distance is on an average 2.7 mm(rang-1 to 5 mm)

The measurement is more in patients presenting with upper incisor proclination.

Steiners analysis

SNA (Maxillary position)  82.0

SNB (Mandibular position)  80

ANB (Maxillary/Mandibular relation)  2

l to NA (Upper incisors to NA mm) 4mm

l to NA (Upper incisors to NA degree)  22

l to NB (Lower incisors to NB mm)  4mm

l to NB (Lower incisors to NB degree) 25

l to l (lnter-incisal angle)  131

SN to GoGn (Mandibular plane angle 32

SN to occlusal plane  14

TWEED ANALYSIS

FMA (Frankfurt plane to mandibular plane) 

25.0 25.8 +- 5.19

FMIA (Frankfurt plane to lower incisor angulation) 

65.0 62.7 +- 6,97

IMPA (Lower incisor to mandibular plane) 

90.0 91.5 +- 5.97

TWEEDS TRIANGLE

THE WITS APPRAISAL

"Wits" Male mm -----------------------------------------

1.0 -2.9 +- 2.45

"Wits" Female mm --------------------------------------

0.0 -2.5 +- 2.54

WITS APPRAISAL