sassouni's archial analysis

1. Tanvi Andrade

2. Introduction
• Dr. Viken Sassouni, an American, was born in
Iran in 1922.
• He studied dentistry in the University of Paris,
France and graduated in 1951.
• He received his doctorate in dentistry from
University of Pennslyvania in 1958 and
doctorate in dental surgery in 1960.
• He became professor and chairman of
orthodontic department in West Virginia
University.
• In 1964 he joined the orthodontic department in
University of Pittsburg which he retained till his
death.
• He wrote seven books and numerous papers.
• He developed a system of identification based
on cranio-facial x-rays for the U.S. Dept of
Defense.
• He was a pioneer in computerized orthodontic
diagnosis and treatment planning.
1922-1983

3. The skull: A battleground of
forces
 The architecture of the skull is a result of
many forces on the adaptable bony
substance
 Eg. Genetic forces in racial of familial
patterns, growth forces, muscular forces
at rest(static), functional muscle
forces(dynamic), and environmental
forces(health, diet).
 At each period of life the skull is the end
result of the interaction of theses forces.

4.  Sassouni based his analysis on a study
conducted on tracings of 100 lateral
head x-ray films.
 The sample included 51 girls and 49
boys.
 They were White children, primarily of
Mediterranean origin.
 The chronological age ranges from 7 to
15 years.
 The aim of the study was to find some
acceptable constant relationships in
architecture of the face and use it for

5. Terminology
 He constructed a series of
planes, arcs and axes on
a profile/ lateral
cephalostat.
PLANES
 Mandibular base plane-
OG
 Occlusal plane- OP
 Palatal plane –ON
 Anterior cranial base
plane
or Basal plane –OS’
 Ramal plane –RX’

6. POINT O
The relationship
between
1. Mandibular base
plane
2. Occlusal plane
3. Palatal plane
4. Anterior cranial base
plane
In a well-proportioned
face, if these planes are
prolonged, they all meet
posteriorly at the same
point i.e O

7. ARCS
 Anterior arc: the arc of
a circle, between
anterior cranial base
plane and mandibular
plane, with
O as the center and
O-ANS as radius.
 Posterior arc: the arc
of a circle, between
anterior cranial base
plane and mandibular
plane with
O as center and OSp

8. The relationship
between point O and
bony profile of a well-
proportioned face
 The anterior arc
passes through:-
pogonion, incisal
edge of upper central
incisor, anterior nasal
spine,nasion & fronto-
ethmoidal junction
 All these points are
equidistant from point
O

9. The posterior
relationship well-
proportioned face
The posterior arc should
also pass through the
gonion.
Thus: the gonion and Sp
are equidistant from O

10. AXES
1. Axis of 6
2. Axis of 1
3. Axis of 6
4. Axis of 1

11. Relationship between
anterior arc and posterior
arc
The face is limited:
Above- by anterior cranial
base plane
Below- by mandibular base
plane
Anteriorly- by arc passing
through ANS
Posteriorly- by arc passing
through Sp
Proportion given by
1. Angle S’OG
2. Ratio of Radii- Ra
/ Rp
3. Combination gives

12. Analysis
 Sassouni’s analysis was the first
cephalometric method to categorise
vertical as well as horizontal
relationships, and also the interaction
between vertical and horizontal
proportions of the face.
 He examined, in sequence, the
mandible, the palate and the anterior
cranial base.

13. THE MANDIBLE
Three main types:
1. Curved: traction
forces at Go &
pulling forces at Me
are in equilibrium
2. Oblique: traction
& pulling forces
are so strong that
there is a notch
anterior to gonial
insertion of
masseter
3. Horizontal:
traction is greater

14. THE PALATE
1. Horizontal: line connecting ANS & PNS passes
through bony structure
2. Convex: line passes above the bony structure
3. Concave: line passes below the bony structure

15. Relationship between palate and
mandible
Generally
 Curved mandible → horizontal
palate
 Oblique mandible→convex palate
 Horizontal mandible→concave
palate

16. Classification of facial types
 Type I: OS does not
pass through point O
 Type II: ON does not
pass through point O
 Type III: OP does not
pass through Point O
 Type IV: OG does not
pass through point O
Subdivision:
A- passes above point O
B- passes below point O
(Eg: Patient X shows
facial pattern
Type IIB)

18. Sassouni found( in 100 subject sample):
 16 with well proportioned faces
 Type II as most frequent
 A well-proportioned face has normal occlusion; but
normal occlusion is necessary but not sufficient for a
well-proportioned face.

19. Vertical proportions
Comparing lower face to upper
face:
 Equal: distance from ANS to
OG = distance from ANS to
OS
 Minus: lower face is smaller
than upper face
 Plus: lower face is larger
than upper face
Use PNS for posterior face

20. Classification of profile
Based on anterior arc and
reference points: Na,
ANS, upper incisor &
pogonion
1. Archial: anterior arc
passes through all
points
2. Prearchial: arc passes
through Na. ANS,
uppper incisor & Pog
are anterior to it
3. Postarchial: same
points posterior to arc
4. Convex: ANS & upper
incisor anterior to arc
passing through Na &
Pog
5. Concave: Same

22. Dental axes
Maxilla
 Axes of U6 & U1
intersect at level of bony
orbital contour- point X
 Form a triangle with
palatal plane
 Angle M’= angle I’ + 10˚
Mandible
 Ramal plane & axis of
L1 form a triangle with
occlusal plane
 Angle R= angle i

23. Thus :
Complete, well-proportioned face, as seen on
lateral ceph, is one in which
1. Four planes meet at point O
2. Upper anterior & lower anterior faces are equal
3. Upper posterior & lower posterior faces are
equal
4. Profile is archial
5. Posterior arc passes through gonion

24. Diagnosis • Occlusion: class II, div 1
• Facial pattern: type IIB (ON)
• Anterior arc: is in front of Pog,
posterior to upper incisor & Na.
thus major malposition is in
pogonion
• Posterior arc: intersects OG
anterior to gonion
• Vertical balance:
 At ANS: upper is shorter than lower
 At PNS: upper equal to lower
• Palatal shape: convex
So,
Horizontally- class II
malocclusion due to posterior
position of mandible

25. Skeletal deep bite & open bite

27. Conclusion
There is no norm that can be applied
indiscrminately to everybody. The concept
of “normal” is not absolute but is relative to
individuality. Thus “absolute measurements,
averages and mean values are less
significant than proportions”.

28. References
 Orthodontics- diagnosis and management of
malocclusion and dentofacial deformities- O P
Kharbanda
 Viken Sassouni -- A roentgenographic
cephalometric analysis of cephalo-facio-dental
relationships -
American Journal of Orthodontics Volume 41 issue
10 1955