TMJ- disorders, anatomy, physiology,function; dislocation of jaw

1. TMJ DISORDERS

2. TMJ- DEFINITION
The temporomandibular joints (TMJ)
are the two joints connecting the
jawbone to the skull.
It is a bilateral synovial articulation
between the temporal bone of the
skull above and the mandible below;
it is from these bones that its name
is derived.
This joint is unique in that it is a
bilateral joint that functions as one
unit.
Since the TMJ is connected to the
mandible, the right and left joints
must function together and
therefore are not independent of
each other

3. STRUCTURE
The main components are the joint capsule,
articular disc, mandibular condyles, articular
surface of the temporal bone,
temporomandibular ligament, stylomandibular
ligament, sphenomandibular ligament, and
lateral pterygoid muscle.

5. FUNCTION
Each temporomandibular joint is classed as a "ginglymoarthrodial" joint since it is both a ginglymus (hinging joint)
and an arthrodial (sliding) joint. The condyle of the mandible articulates with the temporal bone in the mandibular
fossa. The mandibular fossa is a concave depression in the squamous portion of the temporal bone.
These two bones are actually separated by an articular disc, which divides the joint into two distinct compartments.
The inferior compartment allows for rotation of the condylar head around an instantaneous axis of rotation,
corresponding to the first 20mm or so of the opening of the mouth. After the mouth is open to this extent, the mouth
can no longer open without the superior compartment of the temporomandibular joints becoming active.

7. FUNCTION
At this point, if the mouth continues to open, not only are the condylar heads rotating within the lower compartment of the temporomandibular joints, but the
entire apparatus (condylar head and articular disc) translates.
Although this had traditionally been explained as a forward and downward sliding motion, on the anterior concave surface of the mandibular fossa and the
posterior convex surface of the articular eminence, this translation actually amounts to a rotation around another axis. This effectively produces an evolute which
can be termed the resultant axis of mandibular rotation, which lies in the vicinity of the mandibular foramen, allowing for a low-tension environment for the
vasculature and innervation of the mandible.
The necessity of translation to produce further opening past that which can be accomplished with sole rotation of the condyle can be demonstrated by placing a
resistant fist against the chin and trying to open the mouth more than 20 or so mm.
The resting position of the temporomandibular joint is not with the teeth biting together. Instead, the muscular balance and proprioceptive feedback allow a
physiologic rest for the mandible, an interocclusal clearance or freeway space, which is 2 to 4 mm between the teeth.

8. JAW MOVEMENT
Normal full jaw opening is 40-50 millimeters as
measured from edge of lower front teeth to
edge of upper front teeth.
When measuring the vertical range of motion,
the measurement must be adjusted for the
overbite. For example, if the measurement
from the edge of the lower front teeth to the
edge of the upper front teeth is 40 millimeters
and the overbite is 3 millimeters, then the jaw
opening is 43 millimeters.
During jaw movements, only the mandible
moves.
Normal movements of the mandible during
function, such as mastication, or chewing, are
known as excursions. There are two lateral
excursions (left and right) and the forward
excursion, known as protrusion. The reversal of
protrusion is retrusion.

9. Sagittal section of the articulation of
the mandible
Dynamics of temporomandibular joint during voluntary mouth opening and closing
visualized by real-time MRI

10. CLINICAL SIGNIFICANCE- PAIN
• Temporomandibular joint pain is generally due to one of four reasons:
1. Myofascial pain dysfunction syndrome, primarily involving the muscles of
mastication. This is the most common cause.
2. Internal derangements, an abnormal relationship of the disc to any of the other
components of the joint. Disc displacement is an example of internal derangement.
3. Osteoarthritis of the temporomandibular joint, a degenerative joint disease of the
articular surfaces.
4. Temporal arteritis, for which it is considered a reliable diagnostic criteria.

11. TMD
• Pain or dysfunction of the temporomandibular joint (TMJ) is sometimes referred to as
temporomandibular joint dysfunction or temporomandibular joint disorder (TMD). This
term is used to refer to a group of problems involving the temporomandibular joints
and the muscles, tendons, ligaments, blood vessels, and other tissues associated with
them.
• Although rare, other pathologic conditions may also affect the function of
temporomandibular joints, causing pain and swelling. These conditions include
chondrosarcoma, osteosarcoma, giant cell tumor, and aneurysmal bone cyst.

12. EXAMINATION
• The temporomandibular joints can be felt in front of or within the external acoustic
meatus during movements of the mandible. Auscultation of the joint can also be done.

13. SIGNS AND SYMPTOMS
• Signs and symptoms of temporomandibular joint disorder vary in their presentation.
The symptoms will usually involve more than one of the various components of the
masticatory system, muscles, nerves, tendons, ligaments, bones, connective tissue, or
the teeth. TMJ dysfunction is commonly associated with symptoms affecting cervical
spine dysfunction and altered head and cervical spine posture.
• The three classically described, cardinal signs and symptoms of TMD are:
1. Pain and tenderness on palpation in the muscles of mastication, or of the joint itself
2. Limited range of mandibular movement
3. Noises from the joint during mandibular movement, which may be intermittent

14. OTHER SIGNS AND SYMPTOMS
Headache e.g. pain in
the occipital region or
the forehead
Pain elsewhere, such
as the teeth or neck
hearing loss
Tinnitus Dizziness
Sensation of
malocclusion

15. TMD CLASSIFICATION
MUSCULAR:
• Hyperactivity, spasm, and trismus
• Inflammation (myositis)
• Trauma
• Myofascial pain and fibromyalgia
• Atrophy or hypertrophy
ARTHROGENIC:
• Disc displacement (internal derangement)
• Hypomobility of the disc (adhesions or
scars)
• Dislocation and subluxation
• Arthritis
• Infections
• Metabolic disease (gout,
chondrocalcinosis)
• Capsulitis, synovitis
• Ankylosis (fibrous or bony)
• Fracture
• Absent, large, or small condyloid process

16. DISLOCATION OF JAW
Dislocations occur when two bones that originally met at the joint detach. Dislocations should not be confused with
Subluxation. Subluxation is when the joint is still partially attached to the bone.
When a person has a dislocated jaw it is difficult to open and close the mouth. Dislocation can occur following a series
of events if the jaw locks while open or unable to close. If the jaw is dislocated, it may cause an extreme headache or
inability to concentrate. When the muscle's alignment is out of sync, a pain will occur due to unwanted rotation of the
jaw.
If the pain remains constant, it may require surgery to realign the jaw. Depending on the severity of the jaw's
dislocation, pain relief such as paracetamol may assist to alleviate the initial chronic pain. If the pain relief is taken for
an extended period of time, it may negatively affect the person while talking, eating, drinking, etc.

17. DISLOCATION OF JAW- SYMPTOMS
The symptoms can be numerous depending on the severity of the dislocation injury and how long the person is inflicted with the injury. Symptoms of a dislocated jaw include a
bite that feels “off” or abnormal, hard time talking or moving jaw, not able to close mouth completely, drooling due to not being able to shut mouth completely, teeth feel they are
out of alignment, and a pain that becomes unbearable
The immediate symptom can be a loud crunch noise occurring right up against the ear drum. This is instantly followed by excruciating pain, particularly in the side where the
dislocation occurred.[citation needed]
Short-term symptoms can range from mild to chronic headaches, muscle tension or pain in the face, jaw and neck.
Long-term symptoms can result in sleep deprivation, tiredness/lethargy, frustration, bursts of anger or short fuse, difficulty performing everyday tasks, depression, social issues
relating to difficulty talking, hearing sensitivity (particularly to high pitched sounds), tinnitus and pain when seated associated with posture while at a computer and reading books
from general pressure on the jaw and facial muscles when tilting head down or up. And possible causing subsequent facial asymmetry.
In contrast, symptoms of a fractured jaw include bleeding coming from the mouth, unable to open the mouth wide without pain, bruising and swelling of the face, difficulty eating
due to the constant pain, loss of feeling in the face (more specifically the lower lip) and lacks full range of motion of the jaw

18. DISLOCATION OF JAW-
PATHOPHYSIOLOGY
• There are four different positions of jaw dislocation: posterior, anterior, superior and lateral. The most common position is
anterior, while the other types are rare.
• Anterior dislocation shifts the lower jaw forward if the mouth excessively opens. This type of dislocation may happen
bilaterally or unilaterally after yawning. The muscles that are affected during anterior jaw dislocation are the masseter and
temporalis which pull up on the mandible and the lateral pterygoid which relaxes the mandibular condyle. The condyle can
get locked in front of the articular eminence.
• Posterior dislocation is possible for people who get injured by being punched in the chin. This dislocation will push the jaw
back affecting the alignment of the mandibular condyle and mastoid. The external auditory canal may be fractured.
• Superior dislocations occur after being punched below the mandibular ramus as the mouth remains half-open. Since great
force occurs in a punch, the angle of the jaw will be forced upward moving towards the condylar head. This can result in a
fracture of the glenoid fossa and displacement of the condyle into the middle cranial fossa, potentially injuring the facial and
vestibulocochlear nerves and the temporal lobe.
• Lateral dislocations move the mandibular condyle away from the skull and are likely to happen together with jaw fractures.
• Posterior, superior and lateral dislocations are uncommon injuries and usually result from high-energy trauma to the chin. By
contrast, anterior dislocations are more often the result of low-energy trauma (e.g. tooth extraction) or secondary to a
medical condition that affects the stability of the joint (e.g. seizures, ligamentous laxity, degeneration of joint capsule).

19. DISLOCATION OF JAW-
PATHOPHYSIOLOGY
Side view of the
skull with
anterior
dislocation of
jaw.
Side view of
the skull with
posterior
dislocation of
jaw.
Side view of the
skull with superior
dislocation of jaw.
Front view of
the skull with
lateral
dislocation
of jaw.

20. DISC DISPLACEMENT
Temperomandibular joint displacement also known as internal disc derangement is an
abnormal relationship between the articular disc and the mandibular condyle and the
mandibular fossa. The general consensus is that the posterior band of the disc generally lies
in front of the condyle and that the condyle functions on the posterior attachment. Imaging
studies have demonstrated that disc displacements are relatively common.
Stages of TMJ disc displacement:
Stage I: Disc displacement with reduction DDWR (hearing and palpating joint noises during
opening and closing, protrusive opening and closings stops the reciprocal click)
Stage II: Disc displacement without reduction DDWoR (history of clicking and popping with or
without intermittent locking, complaint of limited mouth opening)
Stage III: Chronic disc displacement without reduction (hearing multiple noises during
opening and closing (crepitus), with normal or near normal mandibular dynamics)

22. Temporomandibular Joint (TMJ) Anatomy and Disc
Displacement Animation

23. MANDIBULAR FRACTURE
Mandibular fracture, also known as
fracture of the jaw, is a break through
the mandibular bone. In about 60% of
cases the break occurs in two places. It
may result in a decreased ability to fully
open the mouth.
Mandibular fractures are typically the
result of trauma. This can include a fall
onto the chin or a hit from the side.
Rarely they may be due to
osteonecrosis or tumors in the bone.

24. MANDIBULAR FRACTURE- SIGNS AND
SYMPTOMS
• By far, the two most common symptoms described are pain and the feeling that teeth no longer correctly meet (traumatic
malocclusion, or disocclusion). The teeth are very sensitive to pressure (proprioception), so even a small change in the
location of the teeth will generate this sensation. People will also be very sensitive to touching the area of the jaw that is
broken, or in the case of condylar fracture the area just in front of the tragus of the ear.
• Other symptoms may include loose teeth (teeth on either side of the fracture will feel loose because the fracture is mobile),
numbness (because the inferior alveolar nerve runs along the jaw and can be compressed by a fracture) and trismus
(difficulty opening the mouth).
• Outside the mouth, signs of swelling, bruising and deformity can all be seen. Condylar fractures are deep, so it is rare to see
significant swelling although, the trauma can cause fracture of the bone on the anterior aspect of the external auditory
meatus so bruising or bleeding can sometimes be seen in the ear canal. Mouth opening can be diminished (less than 3 cm).
There can be numbness or altered sensation (anesthesia/paraesthesia in the chin and lower lip (the distribution of the
mental nerve).
• Intraorally, if the fracture occurs in the tooth bearing area, a step may seen between the teeth on either side of the fracture
or a space can be seen (often mistaken for a lost tooth) and bleeding from the gingiva in the area. There can be an open
bite where the lower teeth, no longer meet the upper teeth. In the case of a unilateral condylar fracture the back teeth on
the side of the fracture will meet and the open bite will get progressively greater towards the other side of the mouth.

25. MANDIBULAR FRACTURE

26. SOURCES
• https://www.physio-pedia.com/TMJ_disc_displacements
• https://en.wikipedia.org/wiki/Temporomandibular_joint#Function
• https://en.wikipedia.org/wiki/Temporomandibular_joint_dysfunction#Disc_displacemen
t
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4444699/
• https://www.slideshare.net/UDDent/tmj-diagnosis