Trismus is an inability to open the mouth in the normal range. Once it occurs, it is very difficult to treat. Prevention and early treatment are the better ways.

To locate the Orofacial Pain Specialist, go to American Academy of Orofacial Pain.

How trismus occurs:
  • Trauma to the jaw muscles and nerves
  • Jaw muscles spasm, provoke by injection on lower jaw (mandibular nerve)
  • Muscle stress due to prolonged mouth opening
  • After radiation to the head and neck 
  • Displacement of a segment of the temporomandibular joint; the most common one is the articular disc

Normal Jaw Function
The jaw is a pair of bones forming the framework of the mouth and teeth. The upper jaw is called a maxilla; lower jaw is called mandible. The lower jaw connects to the skull at the temporomandibular joint (TMJ).

Several muscles and nerves around the jaw area work together to open and close the mouth. Mouth opening ranges vary from person to person. Average is 35-55 millimeters that are equal to the width of three fingers.

Surgery and radiation can injure the tissues involved with opening the mouth.

Scarring (fibrosis) can cause muscle and other fibers shorten and tighten as the tissues begin to heal from surgery. Fibrosis can build up and become apparent years after radiation; results in difficulty in opening the mouth.

When you cannot open your mouth well; you may also have other problems such as:

• Cleaning your mouth and teeth; lead to bad breath, cavities, and infections

• Chewing and swallowing; make it difficult for you to eat and drink

• Talking

• Having a breathing tube placed if you ever need general anesthesia

• Difficulty in routine dental examination and treatment

How to prevent trismus
There are 4 ways to help prevent trismus.
• Maintain good oral hygiene.
• Maintain good posture.
• Massage your jaw muscles.
• Exercise your jaw muscles.

Maintain Good Oral Hygiene
• Brush your teeth and tongue after each meal and at bedtime.
• If you have removable dentures or a dental prosthesis, take it out and clean it each time you brush your teeth. Do not sleep with removable prostheses.
• Floss your teeth once daily at bedtime.

Maintain Good Posture
Good posture means sitting and standing with your ears, shoulders, hips, knees, and ankles aligned. To maintain good posture, you need to keep your neck and shoulders strong and flexible. The exercises listed below will help improve posture. Do these exercises twice a day.

Exercises and massage the muscles
During the exercises, breathe normally, without holding your breath. If any of these exercises cause pain, numbness, or tingling, stop them right away and call your doctor. If you have had surgery, check with your doctor before you begin these exercises.

Neck Stretching
Sit or stand with your arms at your side. Hold each stretch for 30 seconds.

1. Bend your head down
2. Extend your head backward
3. Rotate your head to the right
4. Rotate your head to the left
5. Bend your left ear to your left shoulder
6. Bend your right ear to your right shoulder

Chin Tuck
Sit or stand with your arms at your side. While looking forward tuck your chin. Pull your head back to line up your ears with your shoulders. Hold for 3 seconds, repeat slowly 10 times.

Shoulder Blade Pinch
Sit or stand with your arms at your side. Hold the chin tuck above. Pinch your shoulder blades together as tightly as possible. Hold for 3 seconds, repeat slowly 10 times.

Massage Your Jaw Muscle (Masseter Muscle)
Place your index and middle finger on your cheek bone. Run your fingers down over your Masseter muscle (located in front of your ear) ends at your bottom jaw. As you move your fingers, find points that feel tender or tight. Massage each area in a circular direction for 30 seconds.

To keep your jaw muscles relaxed, avoid clenching your jaw at all time.

Exercise Your Jaw Muscles
Use a mirror for these exercises to help you do them correctly. These movements should cause a stretching sensation but should not cause pain.

Active range of motion and stretching exercises
Position: Sit or stand with your head still during these activities.

1. Move your jaw as described, hold each position for 3 seconds and repeat 5 times:

• Open your mouth wide.
• Move your jaw to the left.
• Move your jaw to the right
2. Repeat each position once more. This time, stretch each for 30 seconds.

3. Combine these movements to move your jaw into a circle. Open and close your mouth as you rotate your jaw left to right. Make 5 circles.

4. Repeat another 5 circles in the opposite direction.

Passive stretching exercises
Place one thumb on your upper teeth in the middle of your jaw. Place the index finger of your other hand on lower front teeth at the middle of your jaw. Stretch your jaw opens by pushing your bottom jaw down with pointer finger. Hold this stretch for 30 seconds.

What to do if you develop tightness of muscle when Opening your mouth?

After above practicing If, you still notice any tightening in your jaw call your doctor right away. They can refer you to:

• Speech/Swallowing specialists and physical therapists. They can help you maintain and restore your ability to open your mouth using techniques such as exercise, stretching, and massage or using special devices to help to open your mouth.

• Rehabilitation doctors who will assess your ability to open your mouth. They may use medicine for pain or spasms or suggest other treatments. The earlier you start treatment for trismus the easier it will be to restore your jaw function.

Read more details concerning Temporo Mandibular Disorder (TMD) at the National Institute of Dental and Craniofacial Research (NIH).