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TMJ
/ Bruxism Overview
What
is TMJ?
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
CAUSES
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
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