1. To describe the different structures of TMJ.
2. To describe the biomechanics related to
Why TMJ is a unique Joint
1.It functions bilaterally in harmony
Parts Of The Joint:
2.The articular disc is movable during joint
3.The articular surfaces are covered by
fibrocartilage and not hyaline cartilage
4.The fibrocartilage is considered as the
growth center for the mandible
A raised area located on the articulated
surface of the temporal bone.
The part of the temporal bone which mates to
the upper surface of the disk is the glenoid (or
The part of the mandible which mates to the
under-surface of the disc.
The condylar head is about 20 mm wide
mediolaterally and 10 mm thick
The capsule is a fibrous membrane that
There are three ligaments associated with the
surrounds the joint and incorporates the
TMJ: one major and two minor ligaments.
The major ligament:
The Temporomandibular Ligament, is
It attaches to the articular eminence, the
actually the thickened lateral portion of the
articular disc and the neck of the mandibular
capsule, and it has two parts: an outer oblique
portion and an inner horizontal portion.
The two minor ligaments:
The sphenomandibular ligament runs from
The stylomandibular ligament separates the
infratemporal region (anterior) from the
the spine of the sphenoid bone to the lingula
parotid region (posterior), and runs from the
styloid process to the angle of the mandible
The synovial fluid is a derivative of plasma
These ligaments are important in that they
define the border movements or the farthest
extents of movements of the mandible.
Movements of the mandible made past the
extents functionally allowed by the muscular
attachments will result in painful stimuli, and
thus, movements past these more limited
borders are rarely achieved in normal
and contains low-molecular weight
molecules, including glucose, urea, uric acid
and proteins. The level of these molecules
varies depending on the degree of
inflammation in the joint. Total protein in
normal synovial fluid is approximately 1.5 to
1.8 g/dl. In the inflamed state, this level
The articular disc is a fibrous extension of the
Movie 1.1 Normal TMJ movement
capsule in between the two bones of the joint.
The disc functions as articular surfaces
against both the temporal bone and the
condyles and divides the joint into two
sections. It is biconcave in structure and
attaches to the condyle medially and laterally.
The anterior portion of the disc splits in the
vertical dimension, coincident with the
insertion of the superior head of the lateral
pterygoid. The posterior portion also splits in
the vertical dimension, and the area between
the split continues posteriorly and is referred
to as the retrodiscal tissue.
Different structures in harmony
The disc features three zones of varying
thickness. A prominent posterior thickening
sits atop the condyle and fills the mandibular
fossa above when the mandible is at rest.
A less prominent anterior thickening lies just
Unlike the disc itself, this piece of connective
below the posterior of the articular eminence,
tissue is vascular and innervated, and in some
and a relatively; thin intermediate zone lies
cases of anterior disc displacement, the pain
felt during movement of the mandible is due
The resulting configuration is a biconcave
disc that serves to provide reciprocal articular
to the condyle compressing this area against
the articular surface of the temporal bone.
surfaces between its inferior aspect and the
Joint Cavities. The disc effectively divides
condyle and between its superior surface and
the joint cavity into two distinct upper and
the mandibular fossa and eminence. Only the
lower compartments that allow two types of
peripheral attachments of the disc contain
joint movement, a hinge movement in the
blood vessels; the disc its is avascular, getting
lower compartment and a translatory
its nourishment by diffusion from the
movement in the upper compartment.
periphery and from synovial fluid.
Innervation and vascularization
Had there been any nerve ﬁbers or blood vessels, people would
Sensory innervation of the TMJ is derived from the
auriculotemporal and masseteric branches of V3.
bleed whenever they moved their jaws; however, movement itself
would be too painful
The posterior and posterolateral regions of the joint capsule
contain free nerve endings of C and A delta types ﬁbers that
conduct pain impulses from the joint. This is a part of a feedback
mechanism that limits excessive mandibular movements. The
re t ro d i s c a l i n f e r i o r l a m e l l a c o n t a i n s p ro p r i o c e p t i v e
mechanoreceptors that detect condylar movement and position.
Its arterial blood supply is provided by branches of the external
carotid artery, predominately the superﬁcial temporal branch.
Other branches of the external carotid artery namely: the deep
auricular artery, anterior tympanic artery, ascending pharyngeal
artery, and maxillary artery- may also contribute to the arterial
blood supply of the joint.
In order to work properly, there is neither innervation nor
vascularization within the central portion of the articular disc.
Biomechanics of the joint during
Different Jaw Movements
1. To discus different muscles action in
relation to Jaw movement.
The two movements that occur at this
When the mandible is depressed during opening of
the mouth, the head of the mandible and articular
disc move anteriorly on the articular surface until
the head lies inferior to the articular tubercle.
The mandible is moved primary by the
Movie 2.1 Lateral movement
four muscles of mastication: the
masseter, medial pterygoid, lateral
pterygoid and the temporalis.
Movie 2.2 Medial pterygoid action
These four muscles, all innervated by V3,
work in different groups to move the
mandible in different directions.
Contraction of the lateral pterygoid acts
to pull the disc and condyle forward
within the glenoid fossa and
mandible and the temporalis by pulling
Movie 2.3 Muscle action during opening
up on the coronoid process.
down the articular eminence; thus,
action of this muscle serves to open the
mouth. The other three muscles close
the mouth; the masseter and the medial
pterygoid by pulling up the angle of the
Jaw Movements: Muscle Action
Depression (Open mouth)
Elevation (Close mouth)
Protrusion (Protrude chin)
Masseter (superficial fibres)
Retrusion (Retrude chin)
Masseter (deep fibres)
Side-to-side movements (grinding and
Temporalis on same side
Pterygoid muscles of opposite side
What is Internal Derangement
1. Deﬁne Internal Derangement.
2. Describe signs & Symptoms
related to it.
3. Identify patients with disc
4. Differentiate between the two
types of disc displacement.
5. Choose the correct line of
It is deﬁned as an abnormal positional and
functional relationship between the disk and
Emshoff R. and Rudisch A. (2003) deﬁned internal
derangements of the temporomandibular joint as
an abnormal relation of the articular disc to the
mandibular condyle and the articular eminence.
Jaw pain, clicking of the joint, irregular and limited
movement of the jaw are the characteristic
symptoms of this disorder.
Internal derangement and associated
complications are the most common
pathologic entities affecting the jaw.
Solberg W.K. (1979)
82% of patients presenting with pain
and functional disturbance of their
TMJ will have displaced disks when
examined with magnetic resonance
imaging. The overall prevalence of
symptomatic disk displacement or
internal derangement may range
between 20% and 30%, making them
frequently encountered conditions.
Anterior disk displacement of the TMJ
Movie 3.1 Disc displacement with reduction
is a malrelationship of the disk to the
condylar head and articular eminence.
Although the disk may displace
m e d i a l l y, l a t e r a l l y, o r ( r a r e l y )
posteriorly to the condyle, it generally
First stage in the sequence of events
leading to osteoarthritis.
TMJ morphology, have shown a path
of progression that includes changes
The video indicates the altered
not only in the disc position, but also
relation between the condyle and the
in its conﬁguration.
disc during opening and closing.
Internal derangements can be divided
into 2 categories: anterior disk
displacement with reduction and
anterior disk displacement without
Signs & Symptoms:
Disc displacement is considered to be
associated with clinically noticeable
clicking noises on opening and
closing of the mouth as long as the
condition in which the disk is
located anteriorly and slips back into
its normal position during opening of
the mouth is called anterior disk
displacement with reduction; the
opposite condition is known as
anterior disk displacement without
disc reduces to its normal position on
Disc Displacement With Reduction:
2.Joint sounds (single, short duration)
3.Catching sensation during mouth
4.Deviation in opening pathway
Disc Displacement Without Reduction:
1.Limited mandibular opening
TMJ disc displacement results from
2.Normal eccentric movement to the
3.Restricted eccentric movement to
the contralateral side.
its inability to slide smoothly due to
increased friction or degenerative
changes in the joint surfaces.
The sequence of events, starting with
increased friction in the upper joint
compartment and culminating in disc
5.J o i n t s o u n d s ( l o n g d u r a t i o n
Activation of various parafunctions,
such as clenching, compromises the
lubrication system in the upper TMJ
The resulting increased friction
displaced disc is shared between two
p re v e n t s t h e d i s c f ro m s l i d i n g
vectors, one of which is directed
together with the condyle.
f o r w a rd . A p p a re n t l y, o n m o u t h
On jaw opening, the condyle is pulled
away from the disc by the inferior
head of the lateral pterygoid muscle.
closure, the superior belly of the
lateral pterygoid muscle pulls the disc
As a result, the ligaments joining the
Subsequently, during mouth opening,
disc to the condyle are gradually
the condyle, which is now posterior to
stretched, and the ‘mobilized’ disc
the loose disc, gradually pushes it
gravitates slightly downward and
down the slope of the eminence,
displacing it further forward.
Subsequently, on clenching, the
Since the lateral articular disc bears
unstable disc is propelled forward by
the bulk of the shearing and
pressure from the condyle. At this
compressive loads, persistent loading
point, the force on the slightly
tends to drive it in a medial direction,
which is the ‘path of least resistance’.
Gallery 3.1 MRI
4.MASTICATORY MUSCLE SPASM
Disc displacement with reduction
(arrows pointing to the disc)
technique marked an evolution
et al (1991) described a
towards less surgical treatment.
technique of irrigation of the upper
Arthrocentesis is the most recent
compartment of the TMJ with Ringer's
s u rg i c a l a p p ro a c h f o r i n t e r n a l
lactate solution to treat limited mouth
derangement of the TMJ.
opening due to internal derangement.
The authors called this technique
In the past many cases of anterior
displacement of the disc or closed
lock that did not improve with medical
They reported an increase in mouth
t re a t m e n t ( b i t e p l a t e s , m u s c l e
opening from a range of 12±30 mm
relaxants, diet and physical therapy)
prior to the procedure, to 35±50 mm
were initially treated with surgical
following it. On a visual analogue
repositioning of the disc and
scale of 0±15, the pain decreased
arthroplasty of the mandibular fossa.
from a mean rating of 8.75 to 2.3. This
Arthrocentesis has an intermediate
the vacuum effect within the joint
place between the medical and the
surgical forms of treatment. Ease,
lower cost of materials and excellent
published results so far include this
technique in the international protocol
In 2003, Reston and Turkelson
performed a meta-analysis of surgical
Gallery 3.2 Arthrocentesis technique
for the treatment of TMJ dysfunction.
A r t h ro c e n t e s i s i s a s i m p l e y e t
effective treatment of TMJ disorders,
and it requires minimal invasion.
Signiﬁcant improvements in width of
mouth opening have been reported
with proven long-term results. It is
speculated that the increase in mouth
opening results from the elimination of
treatments for TMJ articular
disorders. They concluded that among
patients refractory to nonsurgical
Mechanism of Action:
I. Reduction in pain level:
therapies, surgical arthrocentesis and
Arthrocentesis reduces pain by removing
arthroscopy were most effective for
inﬂammatory mediators from the joint.
patients with disc displacement
The combined treatment of
arthrocentesis and Sodium Hyaluronate
It is suspected that lavage under
sufﬁcient hydraulic pressure could
widen the narrowed joint space and
release adhesion in the joint space.
Arthrocentesis with sufﬁcient
pressure could be effective for closed
injection may improve the results due to
the long-term lubricating effect of
Sodium Hyaluronate, which prevents the
onset of inﬂammatory mediators that are
responsible for pain.
II. Maximal Mouth Opening:
lock cases with adhesions in the
Arthrocentesis under high pressure is an
upper joint compartment.
effective method to regain normal mouth
opening in closed lock cases. This effect
the anterior margin of the bony external
is usually due to elimination of the
auditory canal as it crosses over the
adhesions around the disc. Also the
posterior aspect of the zygomatic arch (a
lubricating effect of Sodium Hyaluronate
range of 8 to 35mm). The main trunk of
which either maintains lubrication and
the bifurcation of the facial nerve is
minimizes wear and tear mechanically, or
located a mean distance of 23 mm (a
plays a role in nutrition of the avascular
range of 15 to 28 mm) inferior to the
parts of the disc and condylar cartilage.
lowest concavity of the bony external
III. Clicking :
Usually disappears due to decreased
friction and lubricating effect.
Greene MW et al found the tympanic
plate to be located at a range of 6 to 9
mm anterior to the posterior tragus and
Nearby Vital Structures:
perpendicular to the skin at a mean
The frontal branch of the facial nerve is
depth of 25.4 mm (range = 19 to 32 mm).
located a mean distance of 20 mm from