What Is My TMJ?

(Originally posted on bcotoronto.com on Nov 15th, 2012)

The SkullThis week we’re going to head back into a topic that not many people think about in relation to chiropractic (can you tell those are my favourites yet?). We are going to explore your jaw! That’s right! Chiropractors can look after your jaw! Now I’m not saying that we are going to give you a thorough teeth cleaning or perform a root canal. That is still firmly the purview of a Dentist. What I am talking about is HOW the jaw moves. It’s got a hinge in either side that help it open and close to allow us to chew and talk and whistle and many other wonderful things. These joints are called the “Temporomandibular Joints” or TMJs.

Each TMJ is a saddle joint (one concave surface and one convex) that sits high up in your cheek right in front of that little flat in the middle of your ear (called the Tragus). Between the two surfaces of the joint is a little rubbery disc that helps the bones and cartilage glide through the movements they are supposed to make. The two bones coming together in this joint are the Mandible (the jaw itself) from the bottom and the Temporal bone from above (thus the really long name). The temporal bone (the concave part of the joint) acts as a guide to the moveable mandible portion. It can slide forward and back and side to side allowing the jaw’s many complicated movements.

The Skull

The Skull

The Temporomandibular Joint

The Temporomandibular Joint

There are 4 muscles around each of these joints which pull the mandible in different directions to create these movements. The Temporalis muscle stretched up from the joint in a fan and acts to pull your mandible up to close your mouth and provides some of the power for chewing. The majority of the chewing strength comes from the muscle called the Masseter. This muscle sits on the outside of the jaw and is the easiest to feel when biting down. The last two muscles are on the inside of the mouth. They are the “Medial and Lateral Pterygoids” (Tear-i-goy-d) and they run up and down (Medial) and front to back (Lateral) between the Temporal bone and the Mandible.

The Masseter MuscleThe Temporalis MuscleThe Pterygoid Muscles

To assess the function of a jaw there are two ways. The first is fairly simple and can be done anywhere. Place your fingertips in front of your ears on both sides, then very slowly open and close your mouth. You should be able to feel a bump moving beneath your fingers. This is the head of the Mandible. Each side should be moving in concert but when they move differently this means that there is a muscular imbalance between the sides. This can cause uneven wear and tear on the TMJ and the teeth and lead to problems down the road.

The other method requires a mirror. Stand facing the mirror and look directly at your chin. Very slowly open your mouth as wide as you can then close it again. If everything is working correctly your chin should stay in the midline of your face as you open and close. If something is off then your chin will wobble from side to side. You can place one finger in front of your mouth like you are about to “Shh” someone while you open and close to get a better visual indication of midline. You can even do this with a ruler to have a clean, straight reference line.

As I said above, this imbalance can cause wear and tear on the joint and the teeth through uneven pressures but that is not all. The jaw is not floating around by itself. There are a tonne of other muscles that attach to it that are not involved in the movement of the TMJ. There are muscles in the tongue, muscles to the larynx, muscles to the back of the throat, and many more. So when there is muscular imbalance in the TMJ, tension can be transferred to other areas of the body such as the neck, the scalp, and the collar bone. In this way, TMJ issues can cause referred symptoms like headaches and neck pain even without the presence of jaw pain.

One of the first symptoms that people notice when TMJ issues arise is a clicking in their jaw. This is the little disc we discussed earlier. When the joint is not moving properly, this throws off the mechanics the disc was designed for. It starts to catch and slip and makes that clicking sound as it deforms under pressure and escapes the tension. Eventually this will wear down the disc and create holes and starts the slow progression towards arthritis.

This little disc is also responsible for that horrible condition, lock-jaw (not the one from tetanus, that’s different). Lock-jaw happens when the disc gets stuck between the two bones of the joint and cannot get free. The pain of this then causes the muscles of the jaw to spasm and tighten the joint around the jammed disc. So the muscles need to be relaxed and the joint mobilized to free the disc again. Most dentists can do this but you really want someone who knows joints and muscles, and who do you think that might be? That’s right! Your friendly neighbourhood Chiropractor! Chiropractors are trained to assess and treat conditions of the TMJ and help maintain a healthy joint to relieve and avoid pain and problems.

So if you have pain that keeps returning take a look at your jaw and see if this might be your problem and seek the right care for your problem.

Happy and healthy chewing to all and as always, thanks for reading.
Dr. Ben

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