cephalometrics PPT

By

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.

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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.

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Cephalostat consists of two ear rods preventing movement of head.

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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.

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

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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

Downs analysis; 

It is one of the most frequently used cephalometric analysis.

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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.

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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. Positive in class III malocclusion.

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Mandibular plane angle; Intersection of mandibular plane with F.H. Plane. Average value; 21.9’ ( 17 to 28’)

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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.

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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.

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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 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 65.0 incisor angulation)

62.7

+- 6,97

IMPA (Lower incisor to mandibular plane)

91.5

+- 5.97

90.0

TWEEDS TRIANGLE

THE WITS APPRAISAL "Wits" Male mm ------------------------------------ 1.0 ---"Wits" Female mm ----------------------------------- 0.0 --

-2.9

+- 2.45

-2.5

+- 2.54

WITS APPRAISAL