Your lower jaw is connected to your skull on each side of your head, just in front of your ear, by a very complex joint, called the temporo-mandibular joint (or TMJ for short). Possibly the most complex joint in the body, the TMJ is a sliding ball and socket joint, cushioned by a moving shock-absorber disk of cartilage, with 4 major muscles giving you the ability to open and close your mouth, push your lower jaw forward and back, and slide it from side to side. These movements mean you can talk, chew and swallow. The TMJ is supplied by the largest nerve in the head, which also supplies the face, teeth and sinuses, and meets the spinal cord in the neck.
Any disorder in the TMJ could therefore lead to difficulty or pain in moving the lower jaw; and could give rise to headaches, toothache, sinus pain and neck pain. As the joint is so close to the ear the pain could also be felt as earache.
Of course there can be many causes leading to headaches, neck pain and so on; however your dentist may ask you to bite hard and if the pain is increased this suggests that the TMJ is involved.
While the most common symptom is pain, you may also experience
While many external factors cause strain on the TMJ, the most likely causes of TMJ disorder are
If your teeth do not sit together properly when you bite, it causes unusual stresses and strains on the jaw joint and jaw muscles when you talk, chew and swallow. As these actions are occurring all day, every day, those stresses and strains can affect the muscles, ligaments and nerves of the TMJ.
Misaligned teeth are more difficult to clean and the result may be poor oral hygiene which can lead to tooth decay and gum disease. Severe cases can result in poor nutrition as chewing can be affected; speaking difficulties may also occur. Teeth (especially back teeth) may wear out quickly or fracture if the biting forces are uneven or wrongly directed.
Your dentist may help to improve the problem by supplying a custom-made nightguard (splint) or plastic appliance that fits over your upper or lower teeth. This appliance needs to be measured and fitted very accurately so that when you bite on it, all your teeth meet at exactly the same time in a position where your muscles are relaxed. You may have to wear this all the time or, just at night. If the appliance relieves your symptoms then your bite may need to be corrected permanently.
Permanent correction may involve:
As with any joint pain, it can help to put less stress on the joint. So a soft diet can be helpful, as can corrective exercises, relaxation therapy and external heat.
Clenching and grinding your teeth puts pressure on the muscles, ligaments and nerves, and grinding with lateral movements shortens and blunts the teeth being ground and may lead to myofascial muscle pain, temporo-mandibular joint dysfunction and headaches.
The grinding of the teeth can wear away the enamel on the tooth surfaces and expose the softer inner dentine. This can allow tooth decay and also make the teeth vulnerable to fracture and collapse, especially if they have been previously weakened by fillings or other dental procedures.
In severe cases, bruxism can lead to arthritis of the TMJ.
Since teeth grinding is often an unconscious activity carried out during sleep, it can cause problems not only for the grinder but also for anyone trying to sleep alongside them, and become a quality of life issue.
It is not always clear why people grind their teeth, although many people do: the condition affects approximately 8% of the population. There seem to be correlations between bruxism and stress and anxiety; the condition is found more frequently in people who have sleep problems such as snoring or Obstructive Sleep Apnoea and certain lifestyle factors such as the excessive use of tobacco, alcohol and caffeine are associated with teeth grinding.
The most common and effective treatment involves protecting the teeth during sleep with a bite guard (sometimes called splints, occlusal bite guards, bruxism appliances, bite plates, or night guards). Bite guards are typically made of plastic and fit over some or all of upper and/or lower teeth. The guard protects the teeth from being worn down and can reduce muscle strain by allowing the upper and lower jaw to move easily with respect to each other. It also reduces the noise of grinding. Bite guards are only a method of control and will not cure the condition.
Behavioural treatments such as hypnosis, relaxation techniques and meditation may also be helpful.
There is some evidence that biofeedback techniques may reduce the incidence of teeth grinding: biofeedback systems automatically detect the start of grinding and provide a conscious or subconscious signal – such as a quiet sound that increases in volume until the grinding stops, or a mild electrical impulse - to the user so that they can stop grinding. After daytime practice, users learn to relax in their sleep when the signal occurs, without waking up.