Limited mouth opening: what to check by cause and when to get care
Difficulty opening the mouth wide is called limited mouth opening (trismus). The most common cause is a problem with the jaw joint and chewing muscles, but it can also appear with inflammation around a wisdom tooth, infection after tooth removal and, rarely, tetanus, so when and how it started matters. In Korea, Seoul National University Hospital's medical information explains that limited mouth opening from temporomandibular disorder (TMD) can last a long time if left untreated, so if it does not improve, it is good to get an exam.
Key facts
| Symptoms of TMD | Limited jaw movement and asymmetry of the jaw shape (source: KDCA National Health Information Portal) |
|---|---|
| Trouble opening the mouth after wisdom tooth removal | If it continues after 3 days or swelling and pain increase, suspect infection (source: KDCA National Health Information Portal) |
| First symptom of tetanus | Trouble opening the mouth from contraction of the chewing muscles; incubation period 3 to 21 days (source: KDCA Immunization Helper) |
| Treatment of limited mouth opening | Jaw joint mobilization is done for acute or chronic limited mouth opening (source: Seoul National University Hospital) |
| Principle of jaw exercises | Do them as prescribed and do not do any one exercise for more than 1 minute (source: KDCA National Health Information Portal) |
What causes difficulty opening the mouth?
How limited mouth opening is handled differs greatly by cause. It is often caused by the articular disc inside the jaw joint catching or the chewing muscles stiffening, and in that case it is common for the area in front of the ear or the cheek muscle to hurt when the jaw moves.
There are also tooth-related causes. The wisdom tooth information on the National Health Information Portal explains that after a wisdom tooth is removed the mouth sometimes does not open well, and that if this persists or worsens, infection at the surgical site or a jaw joint problem should be checked. The typical causes are as follows.
- TMD, with the articular disc catching or the chewing muscles stiffened
- Gum inflammation around a wisdom tooth (pericoronitis) or infection after tooth removal
- Joint damage or dislocation after a jaw injury
- Tetanus after a wound infection (rare)
What does it look like when the jaw joint is why the mouth won't open?
The National Health Information Portal lists limited jaw movement and asymmetry of the jaw shape as symptoms of TMD. Typical signs are the lower jaw bending to one side when the mouth opens, or a feeling of catching at some point so that it will not open any further.
Some people who usually had jaw sounds find the sounds stop and the mouth opens less, so it is good to be sure to tell the clinician at the exam if you had jaw sounds before. Seoul National University Hospital's medical information explains that if TMD is left untreated, the range of muscle activity shrinks and the state of difficulty opening the mouth wide can last longer.
How do I tell whether it is a wisdom tooth or an infection?
If the gum around a wisdom tooth is swollen and sore and the mouth opens less, inflammation comes to mind first. The National Health Information Portal describes a wisdom tooth with pericoronitis as one of the cases in which removal is needed.
It is common for the mouth to open less for a short time along with swelling after removal, but if swelling or pain actually increases after 3 days or trouble opening the mouth continues, infection should be suspected. If you have a fever or the swelling makes it hard to swallow saliva, go straight to the dentist who did the removal or to emergency care.
If a wisdom tooth is half covered by gum, food and bacteria easily get trapped in the gap and inflammation tends to recur. If swelling and limited mouth opening repeat even after the inflammation settles, discuss with the dentist whether to leave the wisdom tooth or remove it.
What should I suspect if the jaw stiffens after a wound?
Though not common, tetanus also starts with inability to open the mouth. The KDCA Immunization Helper explains that tetanus starts with trouble opening the mouth from contraction of the chewing muscles and goes on to neck stiffness, difficulty swallowing and contraction of the abdominal muscles, with an incubation period of 3 to 21 days.
If the jaw stiffens and the neck gets stiff within this period after a puncture or scrape, you need emergency room care, not a dentist. At the visit, tell them when you were hurt, what the wound looked like and your tetanus vaccination history.
What is the treatment, and what should I watch for at home when the mouth won't open?
If the jaw joint is the cause, conservative treatment such as exercise therapy, physical therapy, an occlusal splint and medication comes first, and Seoul National University Hospital's medical information explains that jaw joint mobilization is done for acute or chronic limited mouth opening. If infection is the cause, treating the inflammation comes first, so confirming the cause is the first step in treating limited mouth opening.
At home, avoid forcing the jaw open with your fingers or pulling hard. The National Health Information Portal advises doing jaw exercises as prescribed and not doing any one exercise for more than 1 minute, so which exercises to do and how much is decided after the exam. In the meantime, avoiding hard foods and cutting food small can reduce strain on the jaw.
Even after limited mouth opening from the jaw joint improves, suddenly opening the mouth wide or the habit of chewing hard food for a long time can bring symptoms back. Even after recovery, be careful not to open the mouth suddenly wide, as Seoul National University Hospital's medical information advises.
Common myths and facts
Myth: If the mouth won't open, you should force it wide to loosen it.
The National Health Information Portal advises doing jaw exercises as prescribed and not doing any one movement for more than 1 minute. Seoul National University Hospital's medical information also advises being careful not to open the mouth suddenly wide.
Myth: Trouble opening the mouth is always caused by TMD.
Inflammation around a wisdom tooth, infection after tooth removal and, rarely, tetanus also cause trismus. If you have a fever, swelling or a recent wound, the cause may be different, so get an exam first.
Frequently asked questions
What should I do if my mouth won't close after opening it wide?
If the mouth will not close after a yawn or after eating large food, it may be a dislocation in which the jaw joint has slipped out of place. Seoul National University Hospital's medical information also lists dislocation as a condition to be distinguished in jaw joint diagnosis. Do not try to put it back by force yourself; get care at a dentist or emergency room.
Why does my mouth open less only in the morning and get better during the day?
If you ground or clenched your teeth during the night, the chewing muscles can be stiff in the morning so the mouth opens less. Teeth grinding during sleep is one of the factors for TMD named by the National Health Information Portal, so if limited opening recurs every morning, it is good to have the dentist look for signs such as tooth wear.
My mouth won't open well the day after a wisdom tooth was pulled. Is that okay?
Right after removal, it is common for opening the mouth to be uncomfortable because of swelling. If swelling and pain are decreasing day by day, keep watching the course, but if it gets worse after the third day or you get a fever, contact the dentist who did the removal right away to check for infection.
Can I take painkillers when my mouth won't open?
The National Health Information Portal introduces short-term anti-inflammatory painkillers and muscle relaxants as medication for TMD, and explains that they are prescribed after an accurate diagnosis. Over-the-counter painkillers can reduce pain briefly, but it is good to get an exam as well so that causes such as infection are not masked.
How long does treatment for limited mouth opening take?
The treatment period depends on the cause and severity. If infection is the cause, it often improves as the inflammation settles, and if the jaw joint is the cause, exercise and habit correction must be kept up steadily. Seoul National University Hospital's medical information also explains that repeating and continuing correct posture and exercise reduces recurrence.