2. 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.
4. 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.
5. 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.
6.
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.
7.
8.
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
9.
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
10.
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
11. 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.
12. 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.
13.
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.
14.
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.
15.
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.
16. 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.
17.
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.
18.
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.
19. 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
