Temporomandibular joint /certified fixed orthodontic courses by Indian dental academy

TEMPOROMANDIBULAR JOINT
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


1

Temporomandibular joint


Types of joints
 Embryology
 Functional anatomy
 Muscles of mastication
 Biomechanics of TMJ
 Evolution

2

Types of joints
Depending on the types of tissues involved
1.

Fibrous joints

2.

Cartilaginous joints

3.

Synovial joints

3

Fibrous joints

1.

Sutures

2.

Gomphosis

3.

syndesmosis

4

Cartilaginous joints
1.

Primary

2.

secondary

5

Synovial joints


Permits significant movement
 Synovial cavity
 Synovial membrane
 Synovial fluid
 hyaline cartilage
 capsule

6

Synovial joints
•
•

Uniaxial/biaxial /multiaxial
Planar /ginglymoid
/pivot/condyloid/saddle/ball and socket

•

Hiltons law

•

Muscles acting upon a joint have same
nerve supply as joint

7

TMJ


GINGLYMOID



DIARTHROIDAL



SYNOVIAL



TRUE COMPOUND

8

TMJ

OTHER SYNOVIAL
JOINTS

2 BLASTEMA
-Temporal
-Condylar

Cavity formation within a
single blastema

Fibrous cartilage at the
articular surfaces

Hyaline cartilage at the
articular surfaces.

Cartilage acts as growth Does not
centre

9



Types of joints
 Embryology
 Evolution

10

Embryology


Primary Jaw joint
Homologous reptiles.



-maeckels cartilage
functions as the primary
joint.mouth opening
begins
 Persists till 4 months IUL
6 weeks iu.-Membranous
bone forms lateral to
meckels cartilage at-body
and ramus

11

Embryology
10th week-the joint forms
both malleo- incudal and
Definite jaw joint move
together in synchrony for 8
weeks in fetal life. The
accessory mandibular
condylar cartilage develops
as 1st blastema..
 Grows towards the later
developing temporal
blastema.



12

Embryology


-Lateral pterygoid develops medial to future
condyle and causes movement at through the
primary meckelian joint.
 Fossa
 Interposed connective tissue becomes thinner.


Two clefts develop in the fibrous connective
tissue forming two joint cavities.

13

Embryology
 1st

inferior compartment
 2nd superior compartment.
 Invading synovial membrane compartment.
 Cavitation.
 Early immobilization
 Early functional activity


14

Embryology
Formation of
condylar +
temporal
blastema and
ossification

Clefting and
formation of
joint cavity

15

Embryology


Articular disc-biconcave.
 Ventarally –lpm
 Dorsally –the superior laminae,inferior
laminae


16

Embryology
Fossa – flat
 Articular tubercle
 Absent condyle,no
fossa/tubercle



17



Types of joints
 Embryology
 Evolution

18

3 components that make up the masticatory
system
1. Maxillae
2. Mandible
3. Temporal bone


19

TMJ


GINGLYMOID



DIARTHROIDAL



SYNOVIAL



TRUE COMPOUND

20

FUCTIONAL ANATOMY


SQUAMOUS PART OF TEMPORAL
BONE



ARTICULAR DISC



CONDYLE


21

FUCTIONAL ANATOMY
condyle


Poles of condyle



Convex
articulating
surface



Articulating
surface –ant and
post

22

FUCTIONAL ANATOMY
Temporal bone


Squamous part



Concave-Glenoid fossa



Squamotympanic fissure



Articular eminence



Roof - thin

23

ARTICULAR DISC
SAGITTAL
VIEW
POSTERIOR
BORDER
INTERMEDIATE
ZONE

ANTERIOR
BORDER
ANTERIOR
VIEW

24

ARTICULAR DISC


Devoid of blood vessels and nerve



Flexible and adaptable to functional
demands


25

Attachments of the articular discRetrodiscal tissue

Loose connective tissue
 Rich blood and nerve
supply
 Bilaminar zone

Superior retrodiscal
lamina(elastic fibres)

Inferior retrodiscal
lamina(collagenous fibres)


26

Attachments of the articular disc -

Temporal bone

Retrodiscal
tissue

Capsular
ligament +
superior
LPM

condyle
Medially + laterally attached to the capsule which divides
27
joint cavity

ARTICULAR DISC


Articulating surfaces are covered with fibrous
tissue
Upper joint
cavity

Lower
joint cavity


Synovial lining /fluid

28

Functions of synovial fluid
I.

Nutrition

II.

Lubrication

1.
2.

Boundary lubrication (moving joint)
Weeping lubrication(compressive
forces)

•

Minimizes friction


29

Ligaments of TMJ

1.
2.
3.

4.
5.

Limit joint movement
Collateral ligaments
Capsular ligaments
Temporomandibular ligaments

Sphenomandibular ligaments
Stylomandibular ligaments

Functional
ligaments

Accessory
ligaments
30

Collateral (discal) ligament
1.
2.








Medial discal
Lateral discal
Divide joint medio laterally
Allows passive movement of
the disc
Permits anterior + posterior
rotation of disc on condyle
Blood vessels + nerves
Proprioception

31

Capsular ligament


Surrounds the TMJ
 Resists forces that
separate the
articulating
surfaces
 proprioception


32

Temporomandibular ligament
1.
2.



Outer oblique portion
Inner horizontal portion
Reinforces capsular
ligament
OOP- Prevents
excessive dropping of
condyle / limits extent of
mouth opening


IHP

33

Temporomandibular ligamentaction
• Limits rotational
opening
• Seen only in
humans – erect
posture
• Prevents damage
to submandibular /
retromandibular
structures

34

Temporomandibular ligament


IHP Limits posterior
movement of
condyle and disc
 Prevents damage
to the retrodiscal
tissue


35

Sphenomandibular ligament


Extents from
spine of
sphenoid to
lingula
 No significant
limiting effects
on mandibe

36

Stylomandibular ligament


Extends from the
styloid process to
the angle + post
border of ramus
 Limits excessive
protrusive
movement

37



Types of joints
 Embryology
 Evolution

38

Muscles of mastication


Masseter
 Temporalis
 Medial pterygoid
 Lateral pterygoid
 Digastric

Muscles of mastication


39

The masseter

Origin insertion &
direction

Function –elevation


40

The temporalis

Function –
Origin & insertion

elevation
retrusion

41

The medial pterygoid

Function 

Origin & insertion

elevation

Protrusion
Muscle sling with Masseter


U/l - mediotrusive

42

The lateral pterygoid- inferior
portion

Function-protrusion
Origin & insertion

U/l – mediotrusive


43
With depressors – downward+forward

The lateral pterygoid- superior
portion

Infratemporal surface
Active during
of greater wing of
power stroke
sphenoid – capsule
Closure with
,disc ,neck
elevators

44

The lateral pterygoids
Exert medial pull on disc & condyle


45

The digastricus

Function– b/L contraction depression of mandible
with fixed hyoid bone
Raises hyoid –swallowingwhen mandible is fixed

46

Other muscles coordinating
Mandibular movements


Coordinated
movements of Supahyoid
 Infrahyoid
 Posterior neck muscles


47

Summary of
mandibular
movements &
muscles
involved


48



Types of joints
 Embryology
 Evolution

49

Biomechanics of TMJ



•

Based on structure and function can be divided
into 2 systems
First joint system
-Inferior joint cavity
Second joint system
-Superior joint cavity


50

Biomechanics of TMJ


Articular disc as meniscus

1.

Not a determinant of joint movement
Attached on one side and unattached on
the other.
Freely extends into the joint space

2.

3.


51

Biomechanics of TMJ


TMJ - no attachment
 Yet stable due to muscles
 Resting stage – tonus
 Increase muscle activity - increase
interarticular pressure
 Absence of pressure - dislocate


52

Biomechanics of TMJ
Disc space varies with
pressure
 Increased – disc space
narrows
 Decreased – space widens
Condyle on anterior /
posterior zone


53

Biomechanics of TMJ
Mandibular opening and closing
SRL –retract the
disc
 Closed joint
position – relaxed
 Stretched – during
opening



54

Biomechanics of TMJ
Mandibular opening and closing
SLP – protractor of the
disc
 ILP – protractor of
condyle
 So forward movement
– articular cartilage –
disc morphology.


opening

closing

55







Biomechanics of TMJ
closed mouth resting
position

SLP - tonus
SLP > SRL
Resting position-interarticular pressure
reduced,disc space wide. Disc rotated anteriorly
Condyle contacts intermediate & post zone
Open mouth –SRL stretches , SRL > SLP Disc
rotated posteriorly


56

Biomechanics of TMJ


57

Biomechanics of TMJ
Power stroke / chewing









pressure reduced on biting side
Fulcrum around food
Pressure increased on contralateral side
Same side – separation – dislocation
SLP - active ,positions disc anteriorly on condyle
Stabilizes joint
Teeth approach intercuspation –pressure increases
Mechanical post rotation – intermediate zoneresting positionwww.indiandentalacademy.com
58

Biomechanics of TMJ


Points to remember

1.

Ligaments do not actively participate in
function of TMJ
Ligaments do not stretch
Articular surfaces must maintain constant
contact

2.
3.


59



Types of joints
 Embryology
 Evolution

60

Adaptive morphology is dependent upon

Locomotion



Feeding


61

EVOLUTION OF T.M.J

Primitive vertebrates
 Collection of food led to dev of jaws along
with fins
Amphibians and reptiles
 Greater demand on jaw mechanics to adjust
to new habitat


62

Mammals


Greater benefit from food source
 Modification in jaws, joint, dentition

Humans


Upright posture
 Bipedal locomotion
 Shrinkage of human face

63

Earliest functional activity of
TMJ
1.Prehension
2.Control size of mass of food entering
alimentary tract
-sharp cusps
-force in a direction effective
-sharp cutting edges

64

Jaw joint has been classified into1.Primitive
jaw
jointreptilian
jointquadrate-articular occlusion

jaw

2.Mamalian type of jaw jointdentary
squamosal articulationearly TMJ


65

Primitive jaw joint –reptilian
joint
Maxillae
 Palatoquadrate bar
Mandible
 Hyomandibular(stapes)
 Quardate(incus)
 Articulare(malleus)
 Dentary
Dentary –squamosal
joint/mammalian jaw
joint

66

Most primitive jaw


Flexible plate of fibrocartilage connects the
upper and lower cartilagenous jaws(shark)
 -1st arch no longer forms the gill and grows
under the brain as palatoquadrate bar.It extends
front to back under the base of the skull to join
the lower jaw(maeckels cartilage )at the
epiceratobranchial joint.
 The second arch modified to support the first
arch in its function-hyomandibular cartilage.

67

Relationship of primitive jaw and
cranial base
AMPHISTYLIC SUSPENSION
Upper jaw connected to cranium-2 places

Behind
eye

Hyomandibular cartilage attached to
cranium


68

cranial base
HYOSTYLIC SUSPENSION

. Hyomandibular element was the only
articulation between the jaws and the
cranial base


69

cranial base
Autostylic suspension
Upper jaws are firmly fused to the cranial base.eg
chimera


70

cranial base
STREPTOSTYLIC SUSPENSION
 Great degree of movement between jaws
and cranial base
 Assists in swallowing
 Reptiles and modern snakes
 The pterygopalatine component can remain
clamped onto the animal while other parts
shifted their grip

71

Mobility of upper and lower jaws
Amphibians and higher vertibrates


Maxillary palatine , pterygoid elements
attached to the cranium,but hyomandibular
(stapes) ,quadrate (incus) and articulare
(malleus) continued to form movable joint.


72

Bones dentine and enamel


Bones dentine and enamel first appeared in
fossil records as-dermal plates of primitive
creatures.
 In primitive sharks the denticles extend into
the jaws to give rise to teeth. The dermal
bones sank into the skin . They gained
attachment to muscles.

73

`
The bones at the margin of upper jaw



Pre maxillae-with ant teeth
Maxillae – with marginal teeth
Jugal bone-lower orbit
Quadrato-jugal
Quadrate



Squamosal bone






74

Lower jaw
Maeckels cartilage(core of the lower
jaw)became invested in 8 separate dermal
bony plates.







Dentary(with marginal row of teeth)
2 spenials
Angular
Surangular
Prearticular
2 coronoid bones

75

Development of muscles
Advanced reptiles – capitii
mandibularis and
pterygoid muscles.
 Well divided muscles
 Increased functional
activity
 Size of dentary
bone,heterodont dentition



76

Development of muscles


Alteration in orientation of jaw
muscles
 Forces directed away from the
joint


77

Development of inter-articular
disc


Primitive joint did not have any cartilage.
 Lateral part of the muscle that extended
from the pterygoid region to the maeckels
cartilage gives rise to the cartilage.


78

Functional activity of the
mamalian TMJ
 Prehension
 Tearing
 Crushing


79

Prehension


Condyle clamped by
glenoid processes
 Reptiles have enlarged
teeth at corners


80

Prehention
1.

Speed
-temporalis muscle
2. Constant reproduction of jaw closure
-interlocking canines
-hinge like tmj


81

Tearing


Combination of
–muscles controlling
the dentition and
movement of the jaws
–neck muscles
 Carnivore dentition
 Grazing activity of the
ungulate


82

Crushing
1.
2.

3.

Slicing (carnivores)
Gnawing (rodent incisors)
Grinding (herbivores)


83

Slicing in carnivore







Well dev canines
Condyle encircled in fossa
at level of occlusal surface
of mandibular teeth
Coronoid – large
Disc present
Right and left halves are
not united at the
symphysis.

84

Slicing in carnivore


Masseter +temporalis
–well dev
 Zygomatic arch-strong
 No forward
 Minimum lateral


85

Rodent - gnawing


Incisors chisel shaped
 Continuous erruption
 Differential wear
 Ant –post oriented
glenoid fossa
 No side to side
movement

86

Herbivore - grinding










Well dev molars
Ascending ramus increased
height
Condyle oval
No articular eminence
Slight post glenoid process
Capsule is present.
Anisognathous-do not
occlude simultaneously.

87

Herbivore - grinding


Disc & capsule present



Masseter + temporalis well dev
but not as much as the
carnivores.
 Lat pterygoid
 Lateral movements prominent


88

References


JEFFEREY P OKESON
 GUNNAR E CARLSSON
 RICHARD TEN CATE
 GRAYS ANATOMY


89

Thank you
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90

Temporomandibular joint /certified fixed orthodontic courses by Indian dental academy

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