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1. EVOLUTION OF T.M.J
 INTRODUCTION
 Role of feeding in vertebrate evolution
 Role of locomotion for collection of
food

2. Early stages in the development of
functional activity of the jaws
D ism e m b e rin g
(c a rn ivo u ro u s ca n in e s)
C ro p p in g
(h e rb ivo ro u s in cis o rs )
T e a rin g
G n a w in g
(ro d e n t in c iso rs)
S licin g
(ca rn ivo ro u s ch e e k te e th )
G rin d in g
(ro d e n t a n d h e rb ivo ro u s ch e e k te e th )
C u ttin g
C ru sh in g
co m m in u tio n
P ie rc in g
P re h e n tio n

3. Nomenclature
 Jaw joint
 Primitive jaw joint or Reptilian jaw joint
or Quadrate articular articulation.
 Mammalian type of jaw joint or
Dentary- squamosal articulation.

4. Evolutionary history of dentary-
squamosal joint
 Hinge development in
the first viceral arch.
 Mobility of upper jaw
and lower jaw.
 Dentary squamosal
contact.
 Influence of muscle
activity upon jaw
development.
 Development of inter
-articulating disk.

5. Skulls Of Earlier And Later Mammal-like
Reptiles From South Africa

6. Progressive
upgrowth of the
dentary bone of
the lower jaw to
form a new
joint with the
skull.

7. Development of Inter-
articular disk

8. Variations Of Functional
activity Of T.M.J.
 PREHENSION
 Ability to grasp and
prevent the escape of a
slippery prey.
 Interlocking canines
 Development of hinged
articulation
 Development of
preglinoid process
laterally and post-glinoid
process mesially
prevents dislocation.

10. TEARING
 Simplest way of comminution
of food to make swallowing
possible and enable digestion
to occur.
 PULL developed by neck
musculature.
 Greater risk of DISLOCATION
of condyle ,leads to
development of preglenoid
process in carnivorous
animals.

11. CRUSHING IN PRIMITIVE MAMMALS
 Ability to bring post canine teeth
together.
 GIANT PANDA-A herbivorous
carnivorous
 Molar teeth richly covered with cusp
and tubercles.
 Transverse cylinder rotating with a
hinge movement in a deep groove.
 Articular disk thin.
 Level of occlution is lower than the
articulation which helps in antero-
posterior GRINDING movement to the
closing movement.
 This represent the adaptation for
herbivorous diet within the
carnivorous.

12.  CUTTING IN THE
CARNIVORE
 Condyle is cylindrical and at the same
level as the occlusal plane.
 Coronoid process is very large and
projects vertically.It provide large area
of insertion for the temporalis
muscle(prevent dislocation).
 Well developed masseter muscle with
large depression on the lat. side of
ramus.
 Prominent preglenoid and postglenoid
processes.
 Interarticular disk present with upper
and lower synovial cavities.
 Joint capsules and ligaments permits
slight lat. Translatory movement.

13.  CUTTING IN
RODENTS
 Sliding postero-anterior
movement of condyle with
relatively little hinge like
rotation present.
 Inter-articular disk well
developed.It helps in
gnawing activity of rodents.
GRINDING IN RODENTS
 GNAWING: Lower jaw
shifted forward to bring the
incisors together.
 SHIFTING: Mandible shift
posteriorly to bring molars
in contact.
 MASTICTION: Movements
bring molars together
without hampering the
incisors.

14.  Study of homonids
for feeding
mechanisms.
 Two forms of
AUTRALOPITHECINES
have been recognized:
 GRACIL FORM: Typified
by Australopithicus
africanus,there is
moderately developed
temporalis and masseter
muscles. This is suitable
for omnivorous diet.
 ROBUST FORM: Typified
by Australopithicus
bosei,there is great
increase in size of
masseter.This is suitable
for herbivorous diet.

15. Development of
Tempromandibular Joint
T.M.J - bilateral synovial
diarthrosis - one freely movable
joint on each side,left and right
surrounded by a capsule whose
internal lining produces a viscid
synovial fluid.

16. Prenatal Condylar Growth
 6TH
WEEK :condensation of
mesenchyme develops
lateral to meckel’s
cartilage.The development
of this mesenchymal
condensation within one
week,a complete
memberanous bony plate is
formed parallel and locally
envoloping the bilateral
meckel’s cartilage.
 At 10TH
WEEK, the bony
mandible has recognizable
form and meckel’s cartilage
starts to be resorbed. At the
same time condylar field
develop at the cranial end
of mandible.

17.  At 12th
week the
condylar process are
clearly recognizable
and secondary
cartilage production will
begun.
 At 14th
week
endochondral
ossification of new
cartilage will start
centrally in the ramus
proceeding upwards.
 From 20th
week ,
subsequent
replacement by a
bone,creating the
typical picture of
growing mandibular
condyle.

18. POST-NATAL GROWTH OF
CONDYLE
 Condyle grows in
harmony with the disk
and glenoid fossa as
the tubercle undergoes
development vertically
at the temporal region.
 Condyle relocate in
posterior direction by
deposition and
resorbtion in anterior
aspect(V-PRINCIPLE).
 Vertical growth of
condyle is by
endochondral bone
growth and bulk by
intramemberanous
bone growth.

19. Temporal Tubercle Growth
 PRE NATAL GROWTH
 In 8th
month human foetus, a straight Zygomatic
arch occurs before birth. Mandible slides
forward and backwards horizontally .this
situation will change quickly after tooth eruption
has started.
 This helps the infant for breast feeding.

20. Post-natal development of
temporal tubercle
 During 1st
year tubercle starts
developing.Temporal bone
anterior to the condyle is
lowered relative to posterior
part.it is characterised by the
increased slope.
 When primary teeth
develops,they permit forceful
chewing action,slope become
steeper and attain 10%of the
normal adult size.
 When 1st
premolar and ant.
Teeth – 70% of adult size.
 When molars erupt – 90%.
 Total change post-natally
amounts to about 40 degrees.

21. Class I
Class II
Class III
Fulcrum
Effort
Resistance
Moment
= load * distance

22. To overcome resistance
1. More Effort
2. Lengthening effort arm
3. Shortening resistance arm
Advantages of Class III lever
1.Less musculature lenthening
during movements
2. Easy and faster prehension
at canines
Disadvantage
1. Restriction on effort arm