Jaw joints (TMJs) are very complicated joints.
They move in four different ways:
- When we open our mouth up to about a centimetre, the knuckle part of the joint does a simple rotation in the socket.
- When we open further the knuckle slides downwards and forwards over a bump on the underside of the cheek bone.
- When we chew, say on one side, the joint on that side turns a little in a horizontal direction.
- When we chew, again on one side, the joint the other side orbits like a moon. To do this it moves forwards down the bump on the cheek bone but also turns a bit towards the other side.
Below is a piece of video with two Swedish nerds from the 1980s talking about TMJs - once you get past the hilarity and if you're not squeamish - it's done using real cadavers, it's rather good. You don't need to watch it all the way through, or know all the jargon to get the idea.
The bits you do need to know are as follows:
- The Condyle is the knuckle of the joint
- The Fossa is the socket
I hope you survived that!
Basically, the condyle (knuckle) has a cartilage sat on top of it. You know those white gristly bits you sometimes get on bacon? That's cartilage. The cartilage is a disc which is usually thicker at the edges with a thinner centre portion. This disc is then balanced on top of the joint and held in place with a ligament.
Imagine you're holding a doughnut on top of your head with a headscarf and you will be pretty close. When the joint opens, the disc is supposed to slide with it to protect the two bony surfaces, but if the "headscarf" is loose, the "doughnut" slides off and can slide off and bunch up. This causes a clunking sensation which can be loud enough to be heard by other people. If you're really unlucky it can completely slide off (reposition) and get stuck. If this happens it feels like you can't put your jaw back in the proper place.
Sometimes the disc has a ridge in it, so that as it slides over the top of the knuckle (actually called the "head of the condyle") it jumps, also producing a click or a clunk - I reckon that as many as one in three joints I've felt over the years (thousands!) have some evidence of a click, so it's very common but sometimes troublesome.
So, your joints click - what can you do to help them?
Think about the "headscarf" - if you can get it to tighten up, it'll hold the disc in place better. If the disc stays on top of the joint where it's supposed to be, then you've a better chance of a healthy joint. The idea is to not to stretch the "headscarf" so that it can tighten up and hold the disc. So try this -
Cut food up small - the idea is not to open your mouth more than about half an inch (1.5cm). Don't try to bite into an apple - slice it.
Consciously chew both sides - very difficult to do without thinking about chewing as we all have a favoured side. By chewing both sides we even up those rotating and orbiting movements.
Don't chew food that's hard work, for instance French bread. And don't eat chewing gum, or you're using the joint for the sake of it and loosening the ligament.
Yawn with your teeth together - the polite yawn, not the "hippo" yawn.
Remember that thing that young people do when they start a relationship? It's known as "snogging" in the UK! Half an hour with your face wrapped around somebody else's with your mouth wide open and you WILL do damage!
- Don't bite your nails - you have to push your jaw forwards to bring the edges of the teeth together on the nail. And don't chew the inside of your lips or cheeks.
- Don't chew a pen or pencil.
You may have to do this for a while to get things to settle. You'll probably work out along the way what sets your jaw joint off - if you do, stop doing it!
So, you've done this for a while and it's not improving - what next?
A visit to the dentist, that's what! Jaw joints that are difficult to settle may need us to intervene.
We usually start with the above advice. The next course of action is something called a bite guard. It's an appliance a bit like a simple brace, designed to separate the upper and lower teeth. It can be made of soft vinyl or hard acrylic. Making them is a bit of a black art! I remember the man who taught me about bite guards, in 1982.....
"50% of people you make a soft bite guard for will get better. 50% of people you make a hard bite guard for will get better. And 50% of people you do nothing for will get better!!!"
He didn't get a Knighthood for nothing!
The point of the appliance is to separate the teeth and allow the jaw to sit where it really wants to sit. That position is with the condyle (knuckle) as far back and up into the socket (fossa) as possible. When it sits there all the muscles that move the jaw are at their shortest. Muscles that are stretched "fire" all the time to try to shorten themselves. This produces lactic acid in the muscle and makes it sore - a bit like a low grade cramp.
If the disc has worn out and the two bones are rubbing against each other they also wear and produce a nasty grating noise/feeling. We call this "crepitus". Joints with crepitus get referred for specialist Maxillofacial advice. In general practice we can't really improve a joint with a worn out disc. It may also have bits of bone floating about in it, so the joint may need to be washed out to remove any schrapnel in the bag of fluid that lubricates the joint.
© Hesslewood Lodge Dental Practice, 16.11.2015