Temporomandibular
joint (TMJ) syndrome or TMJ joint disorders are medical problems
related to the jaw joint. The TMJ connects the lower jaw to
the skull (temporal bone) under your ear. Certain facial muscles
control chewing. Problems in this area can cause head and neck
pain, a jaw that is locked in position or difficult to open,
problems biting, and popping sounds when you bite.
The
TMJ is comprised of muscles, blood supplies, nerves, and bones.
You have 2 TMJs, one on each side of your jaw.
Muscles involved in chewing (mastication) also open and close
the mouth. The jawbone itself, controlled by the TMJ, has 2
movements: rotation or hinge action, which is opening and closing
of the mouth, and gliding action, a movement that allows the
mouth to open wider. The coordination of this action also allows
you to talk, chew, and yawn.
• If you place your fingers just in front of your ears and open
your mouth, you can feel the joint and its movement. When you
open your mouth, the rounded ends of the lower jaw (condyles)
glide along the joint socket of the temporal bone. The condyles
slide back to their original position when you close your mouth.
To keep this motion smooth, a soft disc lies between the condyle
and the temporal bone. This disc absorbs shock to the temporomandibular
joint from chewing and other movements. Chewing creates a strong
force. This disc distributes the forces of chewing throughout
the joint space.
TMJ
can be caused by trauma, disease, wear due to aging, or habits.
•
Trauma: Trauma is divided to microtrauma and macrotrauma. Microtrauma
is internal, such as bruxism (grinding the teeth) and clenching
(jaw tightening). This continual hammering on the temporomandibular
joint can change the alignment of the teeth. Muscle involvement
causes inflammation of the membranes surrounding the joint.
Teeth
grinding (bruxism) and clenching are habits that may be diagnosed
in people who complain of pain in the temporomandibular joint
or have facial pain that includes the muscles involved in chewing
(myofascial pain). Macrotrauma, such as a punch to the jaw or
impact in an accident, can break the jawbone or damage the disc.
o Bruxism: Teeth
grinding as a habit can result in muscle spasm and inflammatory
reactions, thus causing the initial pain. Changes in the normal
stimuli or height of the teeth, misalignment of the teeth, and
changes in the chewing muscles may cause temporomandibular joint
changes. Generally, someone who has a habit of grinding his
or her teeth will do so mostly during sleep. In some cases,
the grinding may be so loud that it disturbs others.
o
Clenching: Someone who
clenches continually bites on things while awake. This might
be chewing gum, a pen or pencil, or fingernails. The constant
pounding on the joint causes the pain. Stress is often blamed
for tension in the jaw, leading to a clenched jaw.
•
Osteoarthritis:
Like other joints in the body, the jaw joint is prone to have
arthritic changes. These changes are sometimes caused by breakdown
of the joint (degeneration) or normal aging. Degenerative joint
disease causes a slow progressive loss of cartilage and formation
of new bone at the surface of the joint. Cartilage destruction
is a result of several mechanical and biological factors rather
than a single entity. Its prevalence increases with repetitive
microtrauma or macrotrauma, as well as with normal aging. Immunologic
and inflammatory diseases contribute to the progress of the
disease.
• Rheumatoid arthritis:
Rheumatoid arthritis causes inflammation. As it progresses,
the disease can cause destruction of cartilage and erode bone,
deforming joints. It is an autoimmune disease involving the
antibody factor against immunoglobulin G (IgG). Chronic rheumatoid
arthritis is a multisystem inflammatory disorder with a persistent
symmetric joint involvement. Certain
