cephalometrics PPT

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By

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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.

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Types

 Lateral cephalogram; provides lateral view of skull.

 _{Frontal cephalogram; provides} anteroposterior view of skull.

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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

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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.

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 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.

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 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

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 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

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 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

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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.

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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 anteroposterior positioning of mandible in relation to upper face. Angle is increased in skeletal class III with prominent chin while decreased in

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 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.

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 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.

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 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.

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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.

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 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.

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 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

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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

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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

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THE WITS APPRAISAL

"Wits" Male mm --- -- 1.0 -2.9 +- 2.45 "Wits" Female mm --- 0.0 -2.5 +- 2.54

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