Temporomandibular joint /certified fixed orthodontic courses by Indian dental academy

Temporomandibular joint
part 1
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

Temporomandibular joint
 Evolution
 Embryology
 Functional anatomy and histology
 Muscles of mastication
 Biomechanics of TMJ


EVOLUTION OF TMJ
 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


EVOLUTION OF TMJ
 increasing efficiency of the feeding
mechanism- critical factor in vertebrate
evolution
 Earliest functional activity of TMJ
prehension

Control size of mass
of food entering
alimentary tract

EVOLUTION OF TMJ
 Mammals
 Greater benefit from food source
 Modification in jaws, joint, dentition
 Humans
 Upright posture / bipedal locomotion
 Food collection shifted to jaws.

EVOLUTION OF TMJ
 Primitive jaw joint
– reptilian joint
1. Dentary
2. Quardate(incus)
3. Articulare(malleus)
 Dentary –
squamosal
joint/mammalian
jaw joint

EVOLUTION OF TMJ
 Relationship of primitive jaw and cranial base
 AMPHISTYLIC SUSPENSION
 upper jaw connected to cranium

Behind
eye

Hyomandibular
cartilage attached
to cranium

 HYOSTYLIC SUSPENSION
 Only lower jaw connected to cranium

EVOLUTION OF TMJ



STREPTOSTYLIC SUSPENSION

 Great degree of movement between upper and lower jaw
 Assists in swallowing
 Amphibians and reptiles
 Maxillary , pterygoid elements attached to the cranium


EVOLUTION OF TMJ
development of muscles
 Advanced reptiles –
capitii mandibularis
 Increased functional
activity
 Size of dentary
bone,heterodont
dentition
 Forces directed away
from the joint
 Alteration in orientation
of jaw muscles

EVOLUTION OF TMJ
Mammal like reptiles - Prehension
 Condyle
clamped by
glenoid
processes


EVOLUTION OF TMJ
Carnivore - cutting
 Well dev canines
 Coronoid – large
 Condyle encircled
in fossa
 Disc present
 Masseter
+temporalis –well
dev
 No forward
 Minimum lateral

EVOLUTION OF TMJ
Rodent - gnawing
 Incisors chisel
shaped
 Ant –post
oriented
glenoid fossa
 Forward
+upward
movement
 Well dev
Masseter

EVOLUTION OF TMJ
Herbivore - grinding
 Well dev molars
 Ascending ramus
increased height
 Condyle oval
 No articular eminence
 Post glenoid process
 Disc & capsule present
 Masseter + temporalis
well dev
 Lat pterygoid
 Lateral movements
prominent

Types of joints
 Depending on the types of tissues involved
 Fibrous joints
 Cartilaginous joints
 Synovial joints

Fibrous joints

1. Sutures
2. Gomphosis
3. syndesmosis

Cartilaginous joints
 Primary

 secondary

Synovial joints
 Permits significant movement
 Synovial cavity
 Synovial membrane
 Synovial fluid
 hyaline cartilage
 capsule

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

TMJ
 GINGLYMO
 DIARTHROIDAL
 SYNOVIAL
 TRUE COMPOUND

embryology
 Primary Jaw joint

 Between Incus and Malleus
 Persists till 4 months IUL

embryology
 Secondary jaw joint
 Between the condyle and temporal bone
 Differs from other synovial joints


embryology
Formation of
condylar +
temporal
blastema and
ossification

Clefting and
formation of
joint cavity

Embryology
TMJ - neonate
 Lax
 Stability –capsule
 Fossa – flat
 Articular tubercle
 absent condyle,no
fossa/tubercle

FUCTIONAL ANATOMY
 SQUAMOUS PART OF TEMPORAL
BONE
 ARTICULAR DISC
 CONDYLE

FUCTIONAL ANATOMY
condyle
 Poles of condyle
 Convex
articulating surface
 Post articulating
surface greater


FUCTIONAL ANATOMY
temporal bone
 Squamous part
 Concave-Glenoid
fossa
 Articular eminence
 Roof - thin

ARTICULAR DISC
SAGITTAL
VIEW

POSTERIOR
BORDER
INTERMEDIATE
ZONE
ANTERIOR
BORDER
ANTERIOR
VIEW

ARTICULAR DISC
 Articulating surfaces are covered with fibrous tissue
Upper joint
cavity

Lower
joint cavity

 Synovial lining /fluid

ARTICULAR DISC
 Devoid of blood vessels and nerve
 Morphology maintained
 Flexible and adaptable to functional demands


Functions of synovial fluid
 Nutrition
 Lubrication
1.
2.

Boundary lubrication
Weeping lubrication

•

Minimizes friction


Retrodiscal tissue
 Loose connective tissue
 Rich blood and nerve
supply
Superior retrodiscal lamina
Inferior retrodiscal lamina

 Bilaminar zone

ARTICULAR DISC attachments
Temporal bone

Retrodiscal
tissue

Capsular
ligament +
superior
LPM

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

Histology of TMJ

cartilage associated with the joint


Ligaments of TMJ
 Collateral ligaments
 Capsular ligaments
 Temporomandibular ligaments

Functional
ligaments

 Sphenomandibular ligaments
 stylomandibular ligaments

Accessory
ligaments


Collateral (discal) ligament






Medial discal
Lateral discal
Divide joint medio laterally
allows passive movement
Permits anterior + posterior
rotation of disc on condyle
 Blood vessels + nerves
 proprioception

Capsular ligament
 Surrounds the TMJ
 Retains synovial fluid
 Resists medial ,lateral
inferior forces that
separate the
articulating surfaces
 Nerves +
proprioception

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

IHP

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

Temporomandibular ligament
 IHP Limits posterior
movement of
condyle and disc
 Prevents damage
to the retrodiscal
tissue


Sphenomandibular ligament
 Extents from
spine of sphenoid
to lingula
 No limiting
effects on
mandibe


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

Muscles of mastication
 Masseter
 temporalis
 Medial pterygoid
 Lateral pterygoid
 digastric


The masseter

Origin & insertion

Function –elevation
U/ L- Mediotrusive


The temporalis

Function –
Origin & insertion

elevation
retrusion

The medial pterygoid

 Origin & insertion

Function -

elevation

Protrusion
Muscle sling with Masseter
U/l - mediotrusive


The lateral pterygoid- inferior
portion

Function-protrusion
Origin & insertion

U/l – mediotrusive
With depressors – downward+forward


The lateral pterygoid- superior
portion

Infratemporal surface
of greater wing of
sphenoid – capsule
,disc ,neck

Active during
power stroke

Closure with
elevators

The lateral pterygoids

Exert medial pull on disc & condyle


The digastricus

Function– b/L contraction
depression of mandible with
fixed hyoid bone
Raises hyoid -swallowing

Other muscles coordinating
Mandibular movements


Summary of
mandibular
movements &
muscles involved


Biomechanics of TMJ

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Biomechanics of TMJ


1.
2.
3.
•
1.
2.
3.

Based on structure and function can be divided
into 2 systems
ONE JOINT SYSTEM
Condyle disc complex
Inferior joint
Tightly bound
cavity
Rotation
SECOND JOINT SYSTEM
Condyle disc with mandibular fossa
Superior
Not tightly bound
joint cavity
translation

Biomechanics of TMJ
 Articular disc as meniscus
1. Freely extends into the joint space
2. does not divide the joint cavity
3. Not a determinant of joint movement


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

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

Biomechanics of TMJ

Mandibular opening and closing

 SRL –retract the
disc
 Closed joint
position – relaxed
 Stretched – during
opening

Biomechanics of TMJ
Mandibular opening and closing
 SLP – protractor of
the disc
 Dual attachment
 ILP – protractor of
condyle
 SLP –active during
closure with elevators

opening

closing

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


Biomechanics of TMJ


Biomechanics of TMJ
Power stroke / chewing

 Resistance met on closure –pressure reduced on
biting side
 Fulcrum around hard food
 Pressure increased on contralateral side
 Same side – separation – dislocation
 SLP - active ,positions disc anteriorly on condyle
 Stabilizes joint
 Teeth approach intercuspation –pressure increases
 Post rotation – intermediate zone-resting position

Biomechanics of TMJ
 Points to remember
1. Ligaments do not actively participate in
function of TMJ
2. Ligaments do not stretch
3. Articular surfaces must maintain constant
contact

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Temporomandibular joint /certified fixed orthodontic courses by Indian dental academy

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Temporomandibular joint /certified fixed orthodontic courses by Indian dental academy