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TMJ Pages
1, 2,
3,
4, 5,
6,
7
The causes of TMD
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There are two basic causes of the TMD
pain :
Traumatic injury and the parafunctional habits (habits that use the
teeth and supporting structures beyond their normal functional design limits).
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1. Trauma
Injury to the face or jaws during automobile
accidents, sporting accidents, fights or just about any activity in which the
jaws or the TM Joints suffer a direct hit can cause physical injury to the
joint, or to the muscles that make the jaws open, close and move side to side.
Injury to the joint itself can lead to swelling, tearing of the internal
ligaments and cartilage, and can, in rare instances, lead to long term
difficulties such as arthritis (chronic inflammation of a joint) or even
in extreme cases, ankylosis
(permanent welding of the otherwise separate structures of the joint).
Thankfully, the majority of traumatic TMD cases are temporary, caused by muscle
cramping, and will subside in several months. Some can hang on and be made
much worse by the second (and major) cause of TMD, parafunctional habits.
2.
Parafunctional habits--Bruxing, (nervous grinding,)
and clenching of the teeth)
The term "parafunctional" refers to any action
that goes beyond normal function. Habits of this nature stretch the normal
physiologic limits beyond the breaking point and thus cause pain, and often,
permanent physical damage to the joint and supporting structures of the jaws and
teeth.
Parafunctional habits
Parafunctional habits come in
numerous forms and depend on the nervous disposition and overall
daily activities of the individual. They may range from
grinding and clenching the teeth, to continuously tapping the
teeth together, holding the jaw in eccentric positions throughout
the day (see the discussion of
posture), working the jaw
muscles against each other without necessarily clenching or grinding
the teeth, or even forcing the tongue against the roof of the mouth
or the front teeth. Bruxing is defined as grinding the
teeth with considerable force for a prolonged period of time, and
clenching is defined as keeping the teeth together without
grinding for a prolonged period. Together, these two habits account for the
vast majority of the parafunction that leads to TMD. The one thing
that all these habits have in common
is that they overwork the muscles and overstress the teeth, the
joints and the gums. Ultimately overuse of the muscles causes
the patient headaches, neck aches, or earaches, while misuse of the
teeth, gums and joints damages those structures. Because these
habits are carried out unconsciously, the patient experiences pain
without understanding that he/she is causing it themselves.One
of the most common reasons that people begin bruxing is having extensive
dental work done. Every time a dentist changes a filling, or
extracts a tooth, this changes the way a patient bites. A patient can
feel, and react to changes in the height of a tooth that amount only to the
thickness of a piece of cellophane. Even tiny changes in the bite can
stimulate an unconscious habit of severe bruxing which can lead to serious
pain.
Before you can understand what parafunction of
the jaws actually means, it is important to understand what normal
functioning involves. (For the purposes of this article, I am limiting
the discussion to parafunction involving the forceful contact of the teeth -- bruxing
and clenching -- and its effect on the temperomandibular joints.)
The relationship of the bite to the joints
In ideal circumstances, when a person closes his
or her teeth together, each individual tooth should make even contact with one
or more teeth in the opposite arch (upper and lower teeth are arranged
in arches). When the teeth are in maximum contact, the ball portion of both
temperomandibular joints should rest
in a comfortable position at the highest point in their sockets.
 In
some people, however, there is a discrepancy in the positions of one or both
of the joints when the teeth are fully closed. This is especially
prevalent in patients who have lost back teeth. The ball of the joint
(the "condyle", colored blue in the diagram)
on one side may be pressed hard against the top or the back of its socket
(the socket, called the "fossa"
is colored green in the diagram), crushing the cartilage disk (the
Meniscus,
colored red) . This can stretch the
ligaments (yellow) that encapsulate the joint
(they are shown cut away on this view, but can be seen just below the blue
ball of the joint). In such an instance, one can see that
when the teeth are pressed together with some force, this action can
put considerable stress on the two joints. |
The graphic to the right
illustrates three different relationships between the ball and socket.
The top illustration shows a normal anatomical arrangement, with the
teeth together (in occlusion) and the condyle and the fossa in a
normal relationship, separated by the meniscus. The two lower
illustrations show situations in which the teeth are also together, but
the condyle and fossa are pressed closer together, damaging the meniscus
in the middle diagram, and crushing the meniscus in the lower diagram.
Left untreated, continual bruxing causes both situations to deteriorate
further causing more damage to the joint. Note that in all three
diagrams, the teeth are together. What is different in each
situation is the position of the condyle within the fossa. Since
teeth move continuously throughout a person's life, constant bruxing and
clenching can
create a dynamic in which the pressure placed on the teeth can cause the teeth to shift position. This, in turn causes a
corresponding shift in the position of the condyle. This is
how a single patient may progress from the normal anatomy seen in the
top illustration, through the situation in the middle diagram to the
situation in the lower diagram.  This
is especially likely to happen if any of the back teeth are removed
early in life. The loss of back teeth causes the remaining
teeth to shift position over time. In order to understand this
phenomenon better, click the icon above.
Dental students, as well as students of other dental and health related
professions may wish to consult my page on
occlusion
which is the companion page to this piece. |
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The good news
No matter how bad the arrangement of the teeth, or how
seriously the joints are misaligned when the teeth are forced together,
if the teeth are not
pressed together with force, and are kept slightly separated, the joints tend to
fall back into their normal positions, and no stress is placed on them at all.
This is the case with most people and is the reason that minor discrepancies in
the joint/teeth arrangement do not cause the average person much pain and agony.
The people who DO develop serious TMD problems are those with the nervous
predisposition to brux (grind) and/or clench their teeth.
The most important thing to remember about
Normal function is this:
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Under normal circumstances, the upper and lower teeth almost
never touch with any real force! |
This is true even when chewing food.
You can prove this to yourself the next time you chew something. You will
note that your own teeth barely touch each other when chewing gum or just about
anything else. The only time the upper and lower teeth actually brace
against each other with any force is when swallowing, and this is only for a
fraction of a second, and they touch lightly at that! Nature designed the
entire system; teeth, gums, joint and muscles to work under NORMAL
circumstances. Thus, under NORMAL function, even discrepancies between the
way the teeth come together and the way the joints sit in their sockets are not
of practical importance. No stress on the teeth means no stress on the
joints or the muscles! Unfortunately, Nature didn't take the stress of
civilization into account.
Now, it is perfectly normal for children 12 and
under to grind their teeth while sleeping, so when you walk into their room at
night and hear them grinding away, don't worry. This is a natural,
built-in mechanism to help us shed the baby teeth and to help the adult teeth
erupt into the most stable positions within the dental arches. However,
after the adult teeth are in place, the habit of grinding and clenching is
supposed to disappear. Unfortunately, civilization is full of stress
(as if you didn't already know). And under stressful conditions, various
infantile habits such as biting the nails, sulking, crying, screaming, throwing
fits and grinding and clenching the teeth tend to return and manifest as stress
relievers. Bruxing and clenching are socially acceptable while the other stress relievers are not, so people
often resort to bruxing when they can't scream at the top of their lungs!
Everyone bruxes or clenches!
Here lies the real root of 95% of all TMJ
associated pain. All those headaches, ear aches, sensitive teeth and other
symptoms mentioned above are the result of stress induced bruxing. What's
that?? You don't grind or clench your teeth?? Yes you do!!! These
habits are usually entirely unconscious. Everyone does it once in a
while, but some people do it to such an extent that they make themselves sick,
and they aren't even aware that they are causing their own symptoms by
unconscious bruxing habits.
Before proceeding further, it is important to
understand that bruxing and clenching together constitute one of the
three major factors that
effect the health of the teeth. For the entire perspective
on why some people never seem to have trouble with their teeth and jaws, while
others never seem able to win the daily battle, read the entire article.
The TMJ section used to occupy a single page on this website,
but due to its extreme length, it has been broken up into seven separate pages.
A good understanding of the Temperomandibular joint, occlusion and their
associated disorders may be gained by reading them in order.
Next page==>The
signs and symptoms of TMJ
TMJ Pages
1,
2,
3,
4,
5,
6,
7
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