TMJ

To define the term.
TMJ stands for Temporo Mandibular Joint.

The joint itself is located directly in front of the ears. Place your finger tips about 1/4 inch in front of the ear opening and open your mouth.............you’ll feel the TMJ move under your finger tips. This joint moves in a very unusual manner......... first it simply hinges open (like most all the other joints in your body), then it glides forward and down (unlike any other joint) to complete its full cycle
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The way our muscles, teeth and joint work together is extremely complicated. In fact the TMJ is the most complicated joint in your body. No other joint you have moves in the intricate ways that they do. Think about one simple aspect.................what other bone in your body has the right and left side joints connected and moving at the same time?

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BASIC ANATOMY

MANDIBLE – the lower jaw.
CONDYLE – the “ball” end of the mandible.
DISC – a dense connective tissue pad that acts as a cushion between the condyle and the socket that it fits into. (Somewhat like the cartilage in your knees).




Labeled anatomy, TMJ beginning to open - rotating against disc


TMJ beginning to move down the slope (fossa).


TMJ still moving down and opening more.


TMJ at maximum extension.

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MUSCLES – there are numerous muscles that “power” the TMJ.
The two illustrated here are the two most frequently involved in soreness / pain.


Temporalis Muscle


Masseter Muscle

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Intra-articular disease vs Myofascial pain disease (MPD

Intra-articular disease - this is the damaging changes that occur directly to the jaw joint, such as degenerative joint disease (DJD), unusual growth and development, and other rarer changes. These are changes to the bony and soft tissue components of the joint - changes that for the most part are irreversible. These are the developments that most often are considered for surgery.

Myofascial pain disease (MPD) - in a very simple explanation - the muscular and ligamental pains that occur due to overuse and tearing. This is quite often reversible

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TMJ SYMPTOMS

When people exhibit a problem with their TMJs, it is most often exhibited as;

Problems associated with the jaw joint itself. 1

Quite often, the disc is displaced to a position in front of the condyle. This results in first a “clicking” or “popping” sound. The disc at this stage is still able to slip or pop back onto the top position on the condyle during the open / close cycle.





Some people may then experience “locking” of the jaw joint. This occurs because the disc is no longer able to slip or pop back on top of the condyle during the opening or closing cycle. (It is perpetually trapped forward). Because this occurs, the mandible opens only in the first part of its motion and is not able to complete a full cycle - the person often exhibits a limited opening of their mouth.





2. Pain emanating from the jaw joint itself

usually either an inflammatory response within the joint and /or
highly innervated tissue being compressed.
3. Problems associated with the muscles.

Sore muscles (usually in the temple or cheek areas). Headaches that can be actually muscle soreness.
Limited opening.
4. Problems with the teeth.

Loose teeth.
Sore teeth.
Excessively worn teeth.
Loss of bone support.
5. Ear problems.

Hissing or ringing.
Ear pain, ear ache (in the absence of infection).
Vertigo, dizziness


CAUSES

There can be numerous causes for TMJ to occur, but the most common is the simple fact that when the teeth come together, the TMJs are not in socket. This can be a hard concept to understand......some basic thoughts may help explain this.

Move your lower jaw forward.....now left.....now right......as you can see, the jaw joint can move in and out of socket freely. This is an unusual movement for a joint (what if your knees could come out of socket?). Now that you can see there is movement allowed in the joint it is important to understand that there is actually one position when closed that is a correct and stable socket position. In this position the powerful muscles that move the joint are at 'rest' and there exists no damaging forces being applied to the joint, teeth or muscles. Now throw in the teeth.......what if in the position of maximum tooth contact the jaw joint had to come out of the 'rest' position to accommodate? The result is that the jaw joint is not in its 'rest' position when the teeth come together and the muscles 'know' this. The muscles will try to get the joints to the 'rest' position but in this scenario they can't. Most commonly this results in muscle hyperactivity usually exhibited as bruxing (nightgrinding) and day clenching.

People do not notice that they have this discrepancy present. The reason for this is that the muscles that control the joint position shift the jaw down (out of socket) just before the teeth make contact. This is known as an "avoidance pattern" - the muscles move the joint so that the teeth won't crash into each other.


Therefore the determining factors for which symptoms or problems a person may acquire is usually a combination of several factors....

How far their teeth are misdirecting their TMJs. 1
How much they brux (grinding of the teeth at night while sleeping). 2
How much stress they're under - stress increases bruxing DRAMATICALLY. 3
How much clenching they do during the day. 4
How genetically susceptible they are. Many people have a bite that is "off", yet they do not show any TMJ symptoms. 5

It is VERY common to find that a person with TMJ problems exhibits a MOLAR FULCRUM

The following images and narratives will attempt to explain and demonstrate this condition.


In this image a correct position for the jaw joint and teeth is demonstrated. Here the teeth make simultaneous and equal contact at the exact moment that the jaw joint is seated in its most stable 'rest' position. The black arrows show that the force being applied to the joint is directly across the disc. Also, in this stable position, the muscles are at 'rest' (not firing) and there exists no damaging forces to either the disc, the bony components of the joint nor the teeth.



This is where most TMD patients find themselves, the teeth are in a position where they make simultaneous and equal contact, BUT the jaw joint is pulled out of socket to make this happen. This position for the jaw joint leads to increased bruxing (night grinding), increased muscular activity and damage to some or all of the following - the disc, bony components of the joint, teeth or bone supporting the teeth



In this image the jaw joint pivots into a correct joint position with the forces now directed correctly across the disc and bony components of the joint, BUT the teeth do not strike together correctly. NOTE that the point of contact (green area) is at the last molar and therefore the term - "molar fulcrum".


Molar fulcrums are revealed through splint therapy .During splint therapy, the muscles will relax and the "avoidance pattern" will diminish over time until the "true" occlusion (bite) is revealed.


SOLUTIONS

So what is the solution? What will make TMJ problems go away?? If you have followed the discussion above on 'CAUSES' then the answer is most often to provide an occlusion (bite) so that when the teeth come into full contact, the joints are not forced out of their 'rest' position.

A very important aspect of this type of therapy is to understand that TMJ therapy is not a CURE ! It is much more a MANAGEMENT of the problem. The jaw joint is easily damaged and NO ONE is going to ever make it perfect again. If a person has sustained joint damage successful treatment means that the damaged joint is put into the least traumatic position so that future damage will be minimized. If the symptoms are primarily muscular pain, therapy can be most often 100% effective.


SPLINTS
If someone is truly having a problem that is associated with their TMJs..........then ..........providing a correct bite would be a big step in the right direction. A bite such that the "molar fulcrum" is eliminated and the TMJs remain in the 'rest' position. This is where splint therapy comes into the picture. A splint (when made correctly) is a physiologically correct bite. In other words..........when the splint is placed over the upper teeth it instantly provides a bite where the muscles, joint and teeth do not antagonize each other, rather they work in harmony with each other as nature intended. So.........IF symptoms diminish while wearing a splint, then it can be assumed that the problem truly was TMJ in nature, and definitive treatment can be performed to minimize future problems.