Short answer: Trismus is the inability to open the mouth to its normal width because of a spasm of the jaw muscles or a problem in the surrounding tissues. Its most common causes are inflammation around a partially erupted wisdom tooth, dental abscesses, a muscle reaction after dental treatment, trauma and jaw joint disorders. Treatment targets the cause; difficulty swallowing or breathing and rapidly growing swelling require emergency care.
Trismus is a condition in which the mouth cannot be opened to its normal width because of a spasm of the jaw muscles or a problem in the surrounding tissues. People often describe it as "lockjaw" or the complaint "I can't open my mouth". Trismus is not a disease in itself but a symptom of an underlying cause. In this article we explain the common causes of trismus, its symptoms, treatment and exercise approaches, and when emergency care is needed.
What is trismus?
Trismus is when mouth opening falls below the usual limits, and this restriction is often accompanied by pain. In a healthy adult, the opening between the upper and lower front teeth is usually between 35 and 50 millimeters; in practice, this is described as being able to fit three stacked fingers into the mouth. When this distance is markedly reduced, eating, speaking, brushing the teeth and the dentist's examination of the inside of the mouth all become difficult.
The structures most often affected in trismus are the chewing muscles. After an infection, inflammation, trauma or injury, the muscles contract as a protective reflex and have difficulty relaxing. In some cases, however, the problem comes not from the muscles but from the temporomandibular joint itself, known as the jaw joint.
Causes: infection, wisdom teeth, trauma, the jaw joint
The most common causes of trismus are infections in the mouth and jaw area, impacted or partially erupted wisdom teeth, dental treatments and jaw trauma, and jaw joint disorders.
Wisdom teeth and pericoronitis
Food and bacteria can build up under the flap of gum covering a partially erupted lower wisdom tooth. Inflammation developing in this area is called pericoronitis. Because the inflammation is close to the chewing muscles, it can restrict mouth opening; swelling, pain, a bad taste and pain radiating to the ear may accompany it.
Tooth-related infections and abscesses
An infection developing at the root of a tooth whose nerve tissue has died due to advanced decay can spread to the spaces around the jawbone. Abscesses originating from the lower molars in particular can affect the muscles and cause marked trismus.
After dental treatment
Temporary restriction of mouth opening may occur after some local anesthetic injections in the lower jaw or after procedures that keep the mouth open for a long time, such as a difficult wisdom tooth extraction. This usually decreases within days; however, if pain and restriction are increasing, a check for infection is needed.
Trauma
Blows to the jaw, fractures of the lower jaw or cheekbone, and bruising of the muscles can restrict mouth opening.
Jaw joint disorders
Displacement of the disc in the temporomandibular joint, joint inflammation, or muscle fatigue due to clenching and grinding at night can cause restricted mouth opening and a feeling of the jaw catching. Some people notice that their jaw is "locked" when they wake up in the morning.
Other causes
Tissue hardening after radiotherapy to the head and neck, some tumors, systemic diseases and, rarely, infections such as tetanus can also cause trismus. For this reason, restricted mouth opening that cannot be explained and increases over time must be evaluated.
Symptoms
The main symptom of trismus is not being able to open the mouth as wide as usual; this is often accompanied by jaw pain, difficulty chewing and muscle tension. Depending on the underlying cause, other symptoms may also appear:
- Difficulty biting into food, or eating a large sandwich or an apple
- A cramping feeling in the jaw muscles, pain in the temples and in front of the ear
- Not being able to reach the back teeth when brushing
- Difficulty speaking, a muffled voice
- If there is an infection, swelling in the face or under the jaw, fever and bad breath
- If the joint is the cause, clicking or catching in the jaw, or the jaw shifting to the side when opening
When the symptoms started and what they are associated with provide important clues for diagnosis. Did it start after a tooth extraction, had a tooth been hurting for a long time, was there a blow to the jaw? Sharing this information with your dentist during the examination helps find the cause more quickly.
How is it diagnosed?
The diagnosis of trismus is based on measuring mouth opening and identifying the cause. The dentist measures mouth opening with a ruler or caliper, examines the jaw muscles and the joint, and checks the teeth and gums. A panoramic X-ray can show the position of the wisdom teeth and possible sources of infection. When the joint is suspected or a widespread infection is considered, advanced imaging such as CT or MRI may be requested.
Treatment and jaw exercises
Trismus treatment is based on eliminating the underlying cause and safely regaining mouth opening; there is no single standard treatment.
- If caused by infection: The inflamed tooth is treated, the abscess is drained if necessary, and medication is given as the dentist considers appropriate. If pericoronitis keeps recurring, extraction of the wisdom tooth may be considered.
- For trismus after a procedure: Cold in the first days, followed by warmth as recommended by the dentist, and a soft diet usually bring relief.
- If caused by the joint and muscles: Resting the jaw, avoiding hard foods and foods that require a lot of chewing for a while, night guards, physical therapy and stress management may be part of the plan.
- After trauma: If there is a fracture, treatment is planned by oral and maxillofacial surgery.
Jaw exercises
Once an acute infection has been brought under control, gentle exercises recommended by the dentist can help gradually increase mouth opening. For example, methods such as slowly opening the mouth up to the point of pain and holding for a few seconds, moving the jaw from side to side in a controlled way, or gradually increasing the opening over time with stacked tongue depressors can be used. It is important to do the exercises regularly and without forcing; if a movement markedly increases pain, it should be stopped and the dentist consulted. Trying to force the mouth open while there is an active infection is not recommended.
When is it an emergency?
If restricted mouth opening is accompanied by difficulty swallowing or breathing, rapidly growing swelling of the face or neck, high fever and a deterioration in general condition, you need to go to the emergency department without delay. These symptoms may indicate that the infection has spread to the deep spaces of the neck and require rapid intervention.
You should also see a dentist promptly in the following situations:
- Pain and restriction that increase rather than decrease within a few days after a tooth extraction
- Swelling, a bad taste and pain radiating to the ear in the wisdom tooth area
- Teeth not closing together as before after a blow to the jaw
- Restricted mouth opening that slowly increases over weeks without an obvious cause
For other frequently asked topics, you can also take a look at our frequently asked questions page.
Examination for restricted mouth opening in Ankara
If you cannot open your mouth as wide as usual or feel pain or catching in your jaw, finding the cause early makes treatment easier. At our clinic in Park Oran Ofis, next to Panora Mall in Çankaya, if a dental cause is identified after the examination, its treatment is planned, and when necessary you are referred to the relevant specialty. To make an appointment, you can use our contact page.
Frequently asked questions
How many days does trismus last?
The duration depends on the cause. Temporary restriction after a tooth extraction usually decreases within days. With trismus caused by infection or the jaw joint, recovery may take longer, depending on treatment of the cause and the exercises.
What should I do if I can't fit three fingers in my mouth?
Not being able to fit three stacked fingers into your mouth suggests that mouth opening is reduced. If pain, swelling or fever accompany it, see a dentist promptly. If you have difficulty swallowing or breathing, go to the emergency department.
Can a wisdom tooth cause trismus?
Yes, pericoronitis developing around a partially erupted lower wisdom tooth in particular can affect the chewing muscles and restrict mouth opening. In recurring cases, the dentist may recommend extracting the tooth.
Can I do exercises at home for trismus?
Once an acute infection has been brought under control, gentle opening exercises recommended by the dentist can be helpful. Trying to force the mouth open while there is an active infection is not recommended; if the exercises increase pain, they should be stopped and the dentist consulted.
