The jaw can lock either open or closed. The two carry different urgency; here is what to do in the first hours, and what not to do.
A locked jaw is one of the situations that alarms patients most, because it arrives suddenly and outside their control. The urgency depends on the direction: if the mouth is stuck open the situation is pressing; if it is stuck closed it is usually assessed the same day.
Two different kinds of locking
Open locking is when the head of the lower jaw slips forward out of the socket and cannot return. The mouth will not close, speech becomes difficult and control of saliva is lost. It usually follows a wide yawn, a long dental appointment or loud laughter.
Closed locking is limited opening because the disc has slipped forward and does not reseat. The patient typically says they can open about one finger's width instead of two, and there has often been a click for a long time beforehand.
What to do when the jaw is locked open
This needs prompt assessment. The longer the joint stays displaced, the greater the muscle spasm and the harder it becomes to reduce. Attending within the first few hours makes the procedure far easier.
While waiting, do not attempt to reduce the jaw yourself or let a relative try. Untrained manoeuvres can damage the joint surface and surrounding tissue. Support the jaw with a cloth, keep it still and avoid opening further.
The first hours of a closed lock
A closed lock is usually painful but not life-threatening. It should not be delayed all the same; with simple manoeuvres and treatment applied early, opening is regained in most patients.
- Do not try to force the mouth open
- Move to soft food that needs no chewing
- Apply a warm compress over the joint
- Stop chewing gum and hard foods entirely
- Arrange an appointment the same day
Other causes of limited opening
Limited opening is not always due to the joint, and the distinction matters because some causes genuinely require urgent intervention. Inflammation around a lower wisdom tooth prevents opening once it spreads to the chewing muscles.
A spreading abscess, bleeding into muscle after an injection, a jaw fracture following trauma and, rarely, tetanus can produce the same picture. Where there is fever, difficulty swallowing, neck swelling or breathing difficulty, the situation belongs in emergency care and must not wait.
How it is resolved in the surgery
In an open lock the dentist repositions the head of the bone into its socket with a specific manual manoeuvre. Where muscle spasm is marked, a muscle relaxant or local anaesthetic may be used first. The procedure usually takes a few minutes.
In a closed lock the muscles are relaxed first and controlled manipulation is then attempted. Once opening is achieved, a night guard and an exercise programme are planned to prevent recurrence.
What to observe afterwards
Once a joint has dislocated, the chance of recurrence rises, so the following weeks matter. Supporting the chin with a hand while yawning, avoiding very wide opening and eating soft food for two or three weeks are the standard recommendations.
Breaks should be requested during lengthy dental appointments. Patients must tell the dentist about a previous locking episode; that information changes how the session is planned.
What if it keeps happening
Recurrent locking points to underlying joint laxity or a long-standing disc displacement. In this group a splint and physiotherapy are the first step; further assessment follows where there is no response.
Where such patients undergo procedures under general anaesthetic, the team should be informed; the wide opening required for intubation can trigger a fresh episode.
Can it be prevented?
Not entirely, but the risk can be reduced. Controlling night clenching, managing stress and not overloading the chewing muscles are the most effective measures. Cracking hard shells, chewing ice and nail biting should stop.
Sleep patterns play a larger part here than they appear to. Clenching happens largely during sleep and increases with disturbed sleep; where snoring or sleep apnoea is suspected, assessing it directly affects the jaw symptoms too.
It is best for patients who have had a click for a long time and whose opening has recently reduced to be assessed before a lock develops. This picture rarely arrives without warning.
