What is it?
Wear in the jaw joint is a process in which the cartilage covering the joint surfaces thins and the bone beneath it changes shape. Because the surfaces are no longer as smooth as they were, a sound like grit rubbing is heard during movement; this sound is different from a click heard at a single moment.
The process is not explained by age alone. Loading the joint beyond what it can carry, a disc that has been out of place for a long time, past trauma and inflammatory rheumatic conditions can all set it up. In conditions such as rheumatoid arthritis the mechanism is different, and management is carried out together with rheumatology.
If the height of the condyle decreases, the back teeth start to meet first, while the front teeth may stay apart. Wear in the joint is therefore not only a question of pain; it is a finding that has a direct effect on planning for orthodontics, prosthetic work and implants. If you notice your bite changing on its own, it needs to be assessed.
Signs
You will not necessarily have all of these at once.
Why does it happen?
- 01
An increase in the load on the joint
Constant clenching, grinding, chewing on one side and gaps left by missing back teeth all raise the pressure on the joint surface. When the surface is under a load greater than its rate of repair for a long time, it starts to thin.
- 02
A history of disc displacement
The disc acts as a cushion between the condyle and the socket. Where a disc has been out of place for a long time, the two bony surfaces work closer together and wear develops more easily.
- 03
Trauma and previous joint procedures
A blow to the jaw, a fracture of the condyle and joint surgery in the past can spoil the smoothness of the surface. In these people the changes may be seen at a younger age.
- 04
Inflammatory rheumatic conditions
Rheumatoid arthritis, juvenile idiopathic arthritis and psoriatic arthritis can involve the jaw joint as well. Several joints hurting and morning stiffness lasting a long time are clues in this direction; diagnosis and treatment are the field of rheumatology.
How does it progress?
- 1
Early phase
The grating sound has recently started; the pain comes on while chewing and goes with rest. A clear change may not yet be visible on an X-ray.
- 2
Active phase
Pain and morning stiffness become marked and mouth opening decreases. Flattening and irregularities on the joint surface may be found on imaging.
- 3
Settling phase
The pain eases while the sound continues. As the bone adapts to its new shape the symptoms lessen; the surface is not expected to return to how it was.
- 4
Established phase
The process has quietened; what remains is the change in shape and, most of the time, a difference in the bite. Decisions about permanent prosthetic work and orthodontics can be made more safely in this phase.
How is it treated?
The aim is not to make the joint what it was; it is to reduce the load, control the pain and preserve function. During painful periods a soft diet, avoiding opening wide, applying heat and resting the jaw come to the fore. An exercise programme is carried out to the extent your dentist shows you; any decision about medication is for your dentist to make.
A splint can be used to spread the load; and because leaving gaps from missing back teeth unrestored for a long time raises the load on the joint, those gaps are assessed too. While the joint is in the active phase, procedures that permanently change the bite, such as grinding down teeth, crowns and orthodontics, are usually postponed; planning can be done more soundly once the picture has quietened.
If pain and restriction carry on, options such as washing out the joint and injections into the joint are assessed in oral and maxillofacial surgery; open surgery is kept for selected cases. Where several joints are involved and morning stiffness is prolonged, a rheumatology assessment is requested.
- Your bite changing rapidly over a few weeks and your front teeth no longer meeting
- Swelling, redness and a fever around the joint
- Your mouth opening less than the width of a finger
- Several joints hurting together and morning stiffness lasting more than an hour
How is it prevented?
- Notice the habit of clenching during the day and make keeping your teeth apart a habit instead.
- Spread your chewing between both sides; avoid very hard foods that take a long time to chew.
- Do not leave gaps from missing back teeth for a long time, and keep to your check-ups.
- Before orthodontics or prosthetic work is planned, tell your dentist about the sound from the joint and any change in your bite.
Frequently asked questions
- Will a worn jaw joint go back to how it was?
- A worn joint surface is not expected to return to how it was. On the other hand, as the bone adapts to its new shape the pain lessens in most people and function is largely preserved. Treatment therefore does not aim to repair the surface; it aims to reduce the load, control the pain and keep an eye on the change in your bite.
- What is the difference between a grating sound and a click?
- A click is a short sound heard at a single moment and is most often linked to the disc slipping back into place. A sound like grit rubbing carries on throughout the movement and suggests that the joint surfaces have lost their smoothness. Because the two sounds point to different conditions, they are asked about separately during the examination.
- If I have wear in the joint, can I have orthodontics or an implant?
- The decision depends on the state of the joint. In the active phase, while pain and change are continuing, procedures that permanently set the bite are usually postponed, because if the joint carries on changing shape the newly built bite can change as well. Once the picture has quietened, planning can go ahead, and the joint is monitored regularly throughout.
This content is for general information and does not replace an in-person examination. Symptoms overlap between conditions, and a diagnosis can only be made clinically.