What does this mean?
The jaw is a single bone, but it is slung from two joints. As your mouth opens, these two joints need to work in balance. If one side cannot take the whole path, the jaw turns around the sound side and moves away from the midline. When you look in the mirror, the centre of your lower front teeth moves away from the centre of your upper front teeth.
The distinguishing point is whether the shift lasts all the way. If your jaw goes to one side as it opens and then comes back to the midline, the path draws an S; this is often to do with the disc on that side slipping back into place during the movement, and a noise usually goes with it. If the shift stays on the same side all the way and does not come back, that joint is not taking the whole path.
In the second pattern, the mouth opening is often reduced as well. This change can settle in quietly; because the noise has stopped, it can be thought to have got better, whereas the disc may no longer be slipping back into place at all. For that reason, the noise disappearing does not on its own count as recovery.
Behind the shift there may be a change of position inside the joint, but there may also be one-sided muscle spasm, a blow in the past, or a habit of guarding that has grown out of pain on that side.
Likely causes
What helps at home?
- Open and close slowly in front of the mirror, and note whether the shift lasts all the way.
- Stay away from opening your mouth all the way, from large bites and from chewing gum for a while.
- Do not try to force your jaw back to the middle or to put it back in place.
- Measure your opening by placing your fingers vertically one above the other; a reduction in the opening is a change that needs following up.
- If you cannot open your mouth two fingers wide
- If the shift started after a blow
- If you notice that your bite has changed over the same period
- Pain increasing quickly, with swelling or fever alongside it
- Numbness in the lip or at the point of the chin
Frequently asked questions
- If there is a shift, does it always need treatment?
- Not every shift needs treatment. A deviation that is painless, does not restrict the mouth opening and has stayed the same for years is usually watched. The decision is made by looking at whether there is pain, whether the opening has reduced and whether the shift has only recently started.
- The noise has stopped but the shift continues, is it getting better?
- The noise stopping does not on its own mean recovery. In some cases the noise is no longer heard because the disc is not slipping back into place at all, and the mouth opening may have reduced in the meantime. It would be sensible to measure your opening, compare it with how it was before and pass this change on to your dentist.
- Could chewing on one side have caused this?
- Chewing on one side is often the result rather than the cause; people avoid the side that hurts or where a tooth is missing. Even so, long-standing one-sided use changes the load on the muscle and the joint on that side. Assessing the missing teeth and the source of the pain is needed to break this cycle.
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.