UNIQUENESS OF TMJ
ANATOMY OF TMJ
ANATOMY OF MASTICATORY
BIOMECHANICS OF TMJ
ASSESSMENT AND EVALUATION
- Range of movements
- Pathway of jaw opening
- Maxillary and mandibular midlines
- TMJ palpation
- Masticatory muscles palpation
- Joint sounds
- Functional activities
The Temporomandibular joint is a
synovial diarthrodial joint.
Also called the ginglymodiarthrodial joint
Gingylmus means hinge joint
Diarthrodial means the joint space is divided into two
separate compartments by means of intra-articular
Both hinge action(rotation)
UNIQUENESS OF THE JOINT
Bilateral diarthrosis→right and left functions
Articular covered by fibrocartilage instead of
This reflects a non-load bearing functional role for
Covering of the condyle is derives from
intramembraneous ossification that normally lacks
the endochondral template from which hyaline
cartilage is derived.
The only joint in human body to have a rigid
endpoint of closure that of the teeth making
ANATOMY OF TMJ
Superiorly,the mandibular fossa of the temporal bone
articulates with the disc
Inferiorly,the disc articulates with the condyle of the
Basic components includes,
- mandibular condyle
- articular surfaces of temporal bone
- joint capsule
- synovial membrane
- intra-articular disc
- masticatory muscles
Envelops the articular disc
- superiorly to rim of glenoid fossa
- inferiorly to neck of condyle
anteriorly continous with
muscle attachment of lateral pterygoid.
- posteriorly,attached to bilaminar zone
Inner surface of the capsule comprises the synovial
Disc acts as the “shock absorber”
“At rest” mandibular positon .the condyle is separated
from the temporal bone by posterior band
As the head of the condyle moves forwards the
artiucular eminence.it is seperated from the temporal
bone by intermediate zone
As anterior movement progresses ,the head of the
condyle moves forwards until it is resting on the
The forward movement of the disc is permitted by the
loose fibroelastic tissue of bilaminar zone;
-Superficial portion-anterior 2/3rd of
lower border of zygomatic arch.
-Deep portion-medial surface of
-Lateral surface of the angle of
- Elevates mandible
Fan shaped muscle
-Coronoid process and anterior border of
-Elevates and retracts mandible
-Superior head-infratemporal surface of greater wing of
-Inferior head- lateral surface of lateral pterygoid plate.
-superior head-anterior part of capsule and intra-articular
-Inferior head-anterior portion of head of the condyle.
-depression of the mandible.
-protrusion of the mandible.
-lateral movements of mandible.
-Medial surface of lateral pterygoid
-medial surface of the angle of the
-elevation of the mandible.
-protrusion and lateral movements.
BIOMECHANICS OF TMJ
Complex combination activity.
Both left and right joints must function together in the
coordination of jaw movements.
3 motions occurs at the mandible
Rotation is the only physiologic movement that can
occur between the surfaces.
Rotation in the TMJ usually occurs in lower joint space
between the head of condyle and the undersurface of
intra articular disc
Occurs only during the opening of mouth upto 20 to
Translation or sliding movement occurs in the upper
joint space between the upper surface of the disc and
inferior surface of glenoid fossa.
Occurs when the mouth opens more than 25 mm
ASSESSMENT AND EVALUATION OF
- Opening and closing of the mouth
- alignment of the teeth
- symmetry of facial structures
RANGE OF MOVEMENT
Involves examining the interincisal opening and
Normal opening: female-35mm
Protrusion of mandible: 5mm
Lateral movement should be measured from midline
to midline,the patient moving the mandible to their
maximum extent,from one side to other.
Range of lateral excursion of mandible: 8 to 10mm
PATHWAY OF JAW OPENING
Mandibular pathway is observed by standing in front
of the patient and asking the patient to repeatedly
open and close the mouth.
Pain in the mandibular muscles or tmj
Physical obstruction to movement
If the pathway is straight
joints are acting
If there is deviation to one side
,then back to midline
alternating first to one side and then across another and
again back to midline
temporary obstruction to the movement
Disc displacement with reduction
If the mandible moves vertically during the first phase
of movement followed by an abrupt deviation
Disc displacement without reduction
In this case,mouth opens normally until the head of
the condyle on the affected side encounters the disc in
a displaced position
Further translation is prevention resulting in marked
MAXILLARY AND MANDIBULAR
Patient with straight pathway or transient deviation
at maximum opening upper and lower
Disc displacement without reduction
the midlines would coincide until a point at which the
head of the condyle encounters the displaced disc
Lateral shift occurs
discrepancy in the midlines are noted
IMMEDIATE PREAURICULAR AREA
IS PALPATED BY PRESSING GENTLY
OVER IT BOTH AT REST AND
INTRA – AURICULAR PALPATION
PLACE YOUR LITTLE FINGER IN THE
EXTERNAL AUDITOR MEATUS ON
ONE SIDE AT A TIME AND
PRESSURE,WHILE ASKING THE
PATIENT TO OPEN AND CLOSE
IT CAN BE PALPATED BIMANUALLY
BY PLACING ONE FINGER
INTRAORALLY AND ANOTHER
EXTERNALLY ON THE CHEEK
IT CAN BE EXAMINED BY PALPATING ITS
ORIGIN EXTRAORALLY.ASK THE
PATIENT TO CLENCH THE TEETH AND
THE OUTLINE OF THE MUSCLE ORIGIN
CAN BE IDENTIFIED.ESPECIALLY THE
DIGITAL PALPATION CAN BE
PERFORMED BETWEEN THE SUPERIOR
AND INFERIOR TEMPORAL LINES.
THE PATIENT IS ASKED TO OPEN
THE MOUTH.THE EXAMINERS
HAND IS PLACED UNDER THE
PATIENTS CHIN AND PRESSURE IS
APPLIED TO TRY TO CLOSE THE
MOUTH WHILE THE PATIENT
TRIES TO RESIST
PLACING THE FOREFINGER OR
THE LITTLE FINGER,OVER THE
BUCCAL AREA OF THE
MAXCILLARY THIRD MOLAR
REGION AND EXERTING
PRESSURE IN A POSTERIOR
,SUPERIOR AND MEDIAL
GENTLY PALPATE THEM ON THE MEDIAL
ASPECT OF THE JAW,SIMULTANEOUSLY
FROM BOTH INSIDE AND OUTSIDE THE
CLINCICAL CONSIDERATIONS OF
There is a palpable difference between the affected
side and the unaffected side
Unaffected side:muscle has a soft rubbery consistency
and the margin is less easy to define.
Affected side:muscle tends to be bunched up,quite
easy to palpate and tenderness may be noted
Masseter is found to be tender in patients who clench
The anterior,more vertical fibres are the main elevator
muscles of the jaw and commomly tender on
Posterior fibres,horizontal fibres are less frequently
tender because their main function is to retrude the
Temporalis is tender in patients who grind their teeth.
Most commonly involved muscle in MPDS.
Unilateral failure of lateral pterygoid to contract
results in deviation of mandible towards the affected
side on opening.
Bilateral failure results in limited opening.loss of
protrusion and loss if full lateral deviation.
It can be palpated only intra-orally
Trismus following IANB is due to medial pterygoid
Also involved in MPDS.
“Single explosive noise”
Felt by the patient but inaudible to examiner
Can be felt by palpating the TMJ in the preauricular
region or by intra- auricular palpation
Auscultation can be done using stereo-stethoscope.
Reciprocal click is seen in disc displacement with
No click is seen in disc displacement without
WHY DO TMJ’S CLICK?
Joint is damaged or overloaded
increased tonicity in the pterygoid muscle
Disc is pulled forward
Rotational phase of mouth opening occurs
As the translation phase starts,the head of condyle
slides forwards and encounters disc in displacement
Friction is then built up until the head of the
condyle’jump past’ this portion of the disc.
Audible release of energy is produced which is the
“CONTINUOUS GRATING SOUND”
Indicates degenerative joint disease.
It can be auscultated using stereo-stethoscope
Assess the chewing,swallowing,talking
Ask the patient to demonstrate the task or ask for
Usede to explore the electrical activity of the muscle by
recording a electromyogram from a volunteer.
The skeletal muscle fibre is innervated by branch of
Under normal circumstances,a neuronal action
potential activates all of the muscle fibres
Contraction of muscle takes place.
The electrical signal recorded from a contracting
muscle is called electromyogram.
MANDIBULAR TRACKING DEVICES
If a jaw tracking devices are used the exact movement
of the mandible can be recorded.
Drawback: many disorders create deviation in
Because a particular deviation may not be
specific for a particular disease.
so it has to be used in conjunction with
history and examination
Used for diagnosing internal derangement in
This technique measures minute vibrations made by
the condyle and it translates
It is reliable.
Used to record and graphically demonstrate joint
Audio amplifying devices or ultrasound echo
recordings[doppler ultrasonography] are used.
Drawback: cannot distinguish from the normal sound.
Records and graphically illustrates surface skin
Various temperatures are denoted by different colours
which produces a map that represent the surface being
Normal subjects are said to have bilateral symmetric
If they are not symmetric suggests a problem.
Nature has blessed us with a marvelously dynamic
masticatory system , allowing us to function and
Articulatory system is an important part of the
masticatory system of our body.
So as a dental care provider to treat the patients of
TMDs before knowing the pathology, this is essential
to know the normal anatomy and evaluation and
assessment of tmj.
TEMPOROMANDIBULAR DISORDERS: A PROBLEM
BASED APPROACH- ROBIN GRAY.
MANAGEMENT OF TEMPOROMANDIBULAR
DISORDERS – OKESON.