Lecture #6 - Temporomandibular Joint

The temporomandibular joint (TMJ) is a joint on

each side of the head that allows for movement of the mandible for mastication, speech, and respiration

A joint is

a site of junction or union between two or more bones

TMJ has its sensory innervation by…

V3 cranial nerve external carotid artery

The TMJ is the articulation of…

the temporal bone and the mandible

The temporal bone is

a cranial bone that articulates with the mandible at the TMJ by way of the joint disc

Temporal bone articulating area is on the…

squamous part

• includes articular eminence and articular fossa

The articular eminence (aka articular tubercle)…

consists of a rounded protuberance the on the inferior aspect of zygomatic process

The articular fossa (aka glenoid/ mandibular fossa)…

• is posterior to the articular eminence

• consists of an oval-shaped depression on the temporal bone, which is posterior and medial to the zygomatic process of the temporal bone

The postglenoid process

A sharp ridge posterior to the articular fossa

Mandible articulation is

• The joint disc working with the knuckle-shaped posterosuperior process of the mandibular ramus

• The head of this process is the mandibular condyle, and its superior surface is the articulating surface of the condyle

The articulating surface of the condyle is

strongly convex in the anteroposterior direction and only slightly convex mediolaterally

A fibrous joint capsule…

completely encloses the TMJ

The fibrous joint disc or meniscus is located…

between the temporal bone and mandibular condyle on each side, allowing articulation between the two bones

The joint disc is not attached to

the temporal bone anteriorly except indirectly through the joint capsule

Upper division of joint disc is

attached to the temporal bone’s post glenoid process

Lower division of joint disc is

attached to the neck of the condyle

The disc completely divides the TMJ into two compartments or synovial cavities:

the upper and lower synovial cavities

The membranes lining the inside of the joint capsule secrete

synovial fluid that helps lubricate the joint and fills the synovial cavities

A ligament is

a band of fibrous tissue that connects bones

The mandible is joined to the cranium by

Three paired ligaments are associated with the TMJ:

1) temporomandibular ligaments

2) stylomandibular ligaments

3) sphenomandibular ligaments

The TMJ ligament prevents

the excessive retraction or moving backward of the mandible

The stylomandibular ligament runs from

the styloid process of the temporal bone to the angle of the mandible

• it becomes taut when the mandible is protruded

The sphenomandibular ligament is not strictly considered

part of the TMJ but is located on the medial side of the mandible, at some distance from the joint

The TMJ allows for the movement of the mandible during

speech and mastication by way of each muscle attached to the cranium and mandible

There are two basic types of movement performed by the TMJ joint and its associated muscles:

1) gliding (or sliding)

2) rotational (or hinge) movements

The gliding movement of the TMJ occurs mainly between the

disc and the articular eminence of the temporal bone in the upper synovial cavity, with the disc plus the condyle moving forward or backward, and down and up the articular eminence

The gliding movement allows the lower jaw to

move forward or backward

Bringing the lower jaw forward involves

protrusion of the mandible

Protrusion involves the bilateral contraction of both of the…

lateral pterygoid muscles

Lateral Pterygoid muscles: Origin

sphenoid (both the superior head and inferior head) 

Lateral Pterygoid muscles: Insertion

Both heads - neck of mandibular condyle

Superior head - TMJ capsule 

Bringing the lower jaw backward involves

retraction of the mandible

The contraction of the posterior parts of both ________ are involved during retraction of the mandible

temporalis muscles

Temporalis Muscles: Origin

Temporal fossa

Temporalis Muscles: Insertion

coronoid process of mandible

Temporalis Muscles: Action

elevate & retract mandible

The rotational movement of the TMJ occurs mainly between the

disc and the mandibular condyle in the lower synovial cavity

• The axis of rotation of the disc plus the condyle and their movements accomplish the depression or elevation of the mandible

Depression of the mandible

is the lowering of the lower jaw

Elevation of the mandible

is the raising of the lower jaw

The muscles of mastication involved in elevating the mandible during closing of the jaws include the

• bilateral contractions of the masseter

• temporalis

• medial pterygoid muscles

Clinical note: Temporomandibular Disorder (TMD)

• The patient may experience chronic joint tenderness, swelling, and painful muscle spasms.

• Also present may be difficulties of joint movement such as a limited or deviated mandibular opening

Crepitus describes

any grinding, creaking, cracking, grating, crunching, or popping that occurs when moving a joint

Internal Problems of the TMJ: Sounds (Popping and Clicking)

• Popping or clicking occurs when the disk is pulled too far forward when opening.

  • Posterior band gets caught between the head of the condyle and the articular eminence.

  • The band may pop forward or posteriorly, makes a reciprocal popping sound.

• Possible that the sound will be too faint to hear, but can be felt on palpation

• Frequently visible if only a problem on one side

• Treatment includes ultrasonography, physical therapy, and plastic splint

Internal Problems of the TMJ: Sounds (Disk Derangement)

Constant anterior displacement of the disk leads to permanent damage to the disk components

• Requires surgery

Internal Problems of the TMJ: Subluxation

• When a person opens his or her mouth too wide and cannot close it or when closing causes popping

• When the condyle glides too far forward and moves anterior to the articular eminence

• Condyle cannot reposition in its proper place.

• Possible causes:

  • Depth of condylar fossa and height of articular eminence

    • Treatment is surgery to decrease the height of the articular eminence

Internal Problems of the TMJ: Bruxism

• Tooth grinding 

  • Usually during sleep

  •  Creates tenderness in the TMJ area

  • Muscles of mastication become tired, but pain is felt in the joint.

• Treatment: plastic night guard that covers the upper teeth

  • Eliminates wear on teeth and tenderness of teeth from stress on the periodontal ligamen

Internal Problems of the TMJ: Arthritis and Other Pain

• Cortisone can relieve arthritis but pain remains a problem.

• Some patients report a grinding sensation in the joint.

  • Might be the result of excessive wear on the disk

  • Occlusal surfaces wear away over time which leads to TMJ pain.

• Rebuilding teeth to original height eases the pain

  • Most pain is actually not in the joint but in muscles

Not all patients with TMD have

abnormalities in the joint disc or the joint itself

• Most symptoms seem to originate from the muscles supporting the joint

With TMD, when the patient tries to close and elevate the mandible, the condylar heads cannot move posteriorly because the muscles of mastication have become spastic…

The patient now has trismus, which refers to reduced opening of the jaws

• Trismus can also occur with odontogenic infections

• Can also from an inferior alveolar nerve block injection

Most cases of TMD improve over time with inexpensive and reversible conservative treatments, including…

patient-based or prescription pain control, relaxation therapy, stress management, habit control, moderate muscle exercises, and orofacial myology

Clinical Note: Myofascial Pain Dysfunction (MPD)

increased pain at the TMJ due to muscle tension and spasm

• Believed that it is a physical manifestation of psychologic stress.

•  No primary disorder of the joint itself is present