Impaired Mouth Opening: What It Is and How It Is Treated

Impaired mouth opening, or trismus, is a painful condition in which the jaws do not open fully. In addition to pain, trismus can lead to problems with eating, speaking, and maintaining oral hygiene, since a person cannot open the mouth widely. Trismus occurs when a person cannot open the mouth more than 35 millimeters. It may develop as a result of jaw trauma, oral surgery, infection, cancer or radiation therapy, as well as inflammation of the TMJ — the temporomandibular joint.

Why Does Jaw Locking Occur?

Impaired mouth opening is any condition that prevents a person from opening the mouth normally and widely. These problems are often associated with dysfunction of the temporomandibular joint, or TMJ — the joint that connects the lower jaw to the skull. This joint, together with the surrounding masticatory muscles, enables jaw movement during speaking, chewing, and yawning.

If the function of this complex system is disturbed, temporomandibular dysfunction, or TMD, occurs. This is a general term for a group of dozens of conditions that cause pain and improper function of the TMJ and masticatory muscles.

During normal joint function, the condylar head moves smoothly within the joint fossa, whereas in dysfunction it may shift or become locked, causing pain and limited movement.

In a healthy person, the lower jaw opens approximately 40–60 mm. If you cannot open your mouth more than 20–30 mm, this is trismus: the jaw feels as if it is locked and cannot move freely.

Trismus may be short-term or chronic. In mild cases, discomfort and jaw stiffness may resolve on their own, but sometimes the problem becomes prolonged and requires treatment. According to the National Institute of Dental and Craniofacial Research, about 10–12 million adults in the United States have pain in the TMJ area, and among women aged 35–44 this occurs twice as often as among men. The average age of patients with TMD is 35–40 years.

Fortunately, most TMJ disorders are treatable and rarely lead to irreversible consequences.

What Are the Main Symptoms?

Signs that may indicate TMJ dysfunction include:

• Inability to fully open the mouth. There is a sensation as if something is preventing or “holding” the jaw. This limitation is often accompanied by muscle tension.
• Pain and discomfort in the jaw, near the ear, or in the head. The pain often worsens when trying to move the jaw, during chewing, or with jaw movement. It may be painful for a person to open the mouth or chew hard food.
• Crunching or clicking in the jaw joint. When opening the mouth, a person may hear characteristic sounds — clicking, crackling, or crunching. Sometimes these sounds may also be heard by other people. If clicking is not accompanied by pain or locking, specific treatment is usually not required.
• A sensation of jaw locking or blockage. This may occur episodically. The mouth may remain in a half-open position, or it may be difficult for the person to separate clenched jaws. The patient may feel unable to control jaw movement, and then the jaw suddenly returns to its place with a click.
• Deviation of the lower jaw during movement. When trying to open the mouth widely, the lower jaw may not move smoothly downward but may deviate to one side. This can be noticed by looking in the mirror: the chin shifts to the left or right.

The symptoms mentioned above may occur together or separately. If you have at least one of these symptoms and it does not go away, it is worth consulting a doctor.

What Are the Causes?

Problems with mouth opening may be caused by several conditions:

• TMJ dysfunction, or TMD syndrome. This is the most common cause of problems with mouth opening. Dysfunction may be caused by displacement of the articular disc, ligament stretching, inflammation, or microtrauma in the joint. Normally, each TMJ contains a cartilaginous disc that regulates jaw movements. If the disc becomes displaced, jaw movement is disturbed. This causes pain, difficulty opening the mouth, and jaw clicking. Temporomandibular dysfunction is often accompanied by muscle spasm around the joint.

• Jaw or facial trauma. Any injury in the area of the joint or lower jaw can cause problems with its movement. This includes blows to the chin or jaw, falls, road traffic accidents, sports injuries, and similar trauma. For example, TMJ dislocation may result in a person being unable to close the mouth or, conversely, unable to open it. Fractures of the lower jaw also cause significant limitation of movement. Joint dysfunction may persist even if some time has passed since the trauma.
• Bruxism, or teeth grinding. Chronic nighttime grinding or unconscious daytime clenching of the teeth creates excessive load on the TMJ and masticatory muscles. Bruxism is often associated with stress and anxiety. Constant muscle overstrain leads to painful spasm, which makes mouth opening difficult and causes morning jaw stiffness. In addition, strong pressure during teeth clenching may damage the articular disc and cartilage. Stress itself also contributes to tension in the jaw muscles. Thus, stress and bruxism are significant factors in the development of TMJ dysfunction.

• Arthritis of the joint. Degenerative or inflammatory diseases can also affect the temporomandibular joints. For example, osteoarthritis, or age-related “wear” of cartilage, may cause crunching and limited mobility. Rheumatoid arthritis, a systemic inflammatory disease, also sometimes affects the TMJ, leading to pain and stiffness. Arthritic changes damage the cartilage and deform the joint surfaces, which may cause problems when opening the mouth.
• Malocclusion and dentofacial abnormalities. An improper relationship between the teeth of the upper and lower jaws, or a sudden change in the bite that occurs after tooth loss, may sometimes be associated with the development of TMD. In some cases, a severe imbalance in the mouth may overload the joint. For example, if the jaw is displaced and moves incorrectly, this may eventually cause pain and clicking.
• Tumors and other diseases. A rare but serious cause of problems with mouth opening may be tumor processes in the maxillofacial area. Benign or malignant tumors in the masticatory muscles, parotid gland, mandibular bone, or the joint itself may interfere with jaw movement or cause muscle spasm. In addition, patients with malignant tumors of the head and neck often experience trismus after treatment. According to a study in the Journal of Clinical Oncology, up to 40% of people who undergo radiation therapy experience problems with mouth opening. Radiation causes fibrosis, or scarring, of the muscles and joint tissues, which limits their mobility.

In 60% of cases, the cause of problems with mouth opening is TMD; in 20% — trauma; in 15% — bruxism; and in 5% — other factors.

Other diseases that may lead to trismus include:

• tetanus;
• infections in the throat, tonsils, or masticatory muscles;
• purulent abscesses of the lower jaw;
• scar changes after maxillofacial surgery.

Such conditions are uncommon, but they should be kept in mind, especially if problems with mouth opening appeared after cancer treatment, a severe infection, or surgery.

In younger patients, TMJ dysfunction and bruxism are more common, whereas in older patients arthrosis is more frequent. There are cases when the exact cause of the disorder is difficult to determine, especially when several factors are combined. For example, a person with arthritis may develop muscle spasm against the background of stress. A qualified doctor will pay attention to all possible factors, because the success of treatment depends on correctly identifying the cause.

Clicking in the joint is observed in 75% of patients with TMD, whereas complete jaw locking occurs in only 15–20% of cases.

When to See a Doctor

Minor problems with mouth opening often do not require medical intervention. However, there are situations when medical help is necessary.

Consult a dentist or maxillofacial surgeon in the following cases:

• pain in the jaw or temple area is constant, has sharply worsened, or interferes with eating;
• you cannot fully open your mouth or close your jaws;
• the jaw is locked in an open or closed position;
• it is difficult to speak and eat, and this affects quality of life;

• symptoms do not disappear within several days or become worse;
• there is swelling, high fever, or other signs of inflammation in the joint area;
• facial trauma occurred, after which impaired mouth opening developed.

Remember that early medical attention can prevent the condition from worsening. If treatment is delayed, complications may occur — from chronic pain to irreversible joint damage.

How TMJ Pathology Is Diagnosed

Proper diagnosis is the key to successful treatment of TMJ pathology. The doctor will begin with a detailed medical history, asking when and how the symptoms appeared, what provokes the pain, and whether there has been trauma, crunching, or locking.

Next, a clinical examination will be performed, during which the doctor will:

• palpate the areas around the joints and masticatory muscles to identify painful points;
• determine whether there is clicking or friction during jaw movement;
• assess how widely the patient can open the mouth and whether there is any jaw deviation.

What Instrumental Examination Methods Are Used?

To clarify the causes of the disorder, imaging studies may be prescribed:

• X-ray or panoramic dental and jaw image:
  provides a general idea of the condition of the bones, the presence of arthritic changes, dislocations, or fractures.
• Computed tomography, or CT, of the TMJ: allows detailed layered images of the bony structures of the joint to be obtained and is good at detecting bone changes, such as deformities of the condylar process, consequences of trauma, or arthritis. CT is effective for bone changes in 90% of cases.
• Magnetic resonance imaging, or MRI, of the TMJ: is the optimal method for evaluating the soft tissues of the joint: the articular disc, ligaments, and muscles. MRI shows whether the disc is displaced or damaged and whether there is inflammation in the joint. MRI detects disc displacement with 95% accuracy.
• TMJ arthroscopy: a minimally invasive procedure in which a tiny video camera is inserted directly into the joint cavity through a puncture. This examination is prescribed only in complex cases and allows the doctor to inspect the internal structures of the joint and even perform therapeutic manipulations.

During diagnosis, it is also important to rule out other conditions that may affect jaw function, such as otitis, neuralgia, and dental problems. Only after a comprehensive examination is the final diagnosis established and a treatment plan developed.

What Treatment Is Available?

Treatment of impaired mouth opening depends on the cause and severity of the condition. In most cases, doctors use a step-by-step approach: from the simplest conservative methods to more complex ones. Conservative therapy is effective in 85% of TMD cases.

• Observation and self-care. If symptoms are moderate, the doctor may limit treatment to monitoring the condition without serious interventions. The patient will be advised to “unload” the joint and allow it to rest: avoid hard foods and try not to open the mouth widely when yawning. Light massage of the masticatory muscles may also be performed independently. Such conservative methods are often sufficient, since, according to studies, in many cases TMD symptoms disappear without any complex procedures.
• Therapeutic exercises and physiotherapy. Special jaw exercises help restore normal movement and strengthen the muscles. A doctor or physiotherapist will select a set of exercises, which may include smooth mouth stretching, forward-backward jaw movements, side-to-side movements, and so on. Physiotherapeutic procedures are used to reduce pain and muscle spasm. Some patients benefit from learning to control jaw muscle tension through conscious relaxation. These methods are especially useful if the cause of the condition is stress and the habit of clenching the jaws. Physiotherapy is aimed not only at symptoms but also at eliminating functional blockage: manually, the therapist can stretch and knead the masticatory muscles, improving joint mobility. According to a study in the Physical Therapy Journal, physiotherapy reduces pain by 60–70% within 4–6 weeks.
  • Mouthguards. One of the main methods of treatment for bruxism and jaw overstrain is the use of special mouthguards. A mouthguard is an individual plastic appliance worn on the teeth at night. During uncontrolled nighttime teeth grinding, the mouthguard protects not only the teeth themselves but also reduces overload on the joints and muscles. There are different types of mouthguards: soft silicone or hard acrylic, upper or lower. It should be noted that mouthguards do not treat structural changes, but they are a means of protection and unloading.

  
• Medication treatment. Medications are used to relieve pain, inflammation, and muscle spasm. The most commonly used are nonsteroidal anti-inflammatory drugs, such as ibuprofen or naproxen. In cases of severe pain, stronger painkillers or muscle relaxants that relax the masticatory muscles may be prescribed for a short course. Sometimes low doses of tricyclic antidepressants or sedative medications are used, which helps interrupt the “pain — tension — pain” cycle, improve sleep, and reduce symptoms of bruxism. It is important to follow the doctor’s prescriptions and avoid self-medication, since some of these medicines may have side effects.
• Surgical treatment. Surgery is used only when conservative therapy has not produced results. TMJ operations are performed rarely and only according to strict indications, because they carry risks, like any surgery.

Modern surgical techniques are minimally invasive:

• arthrocentesis: joint lavage to remove inflammatory fluid and improve mobility;
• arthroscopic surgery: instruments are inserted through a small puncture, allowing the surgeon to remove scar tissue, release an entrapped disc, or correct minor defects;
• open joint surgery: arthroplasty, reconstruction, or joint replacement is the final step and is used only when other methods do not help.

In the treatment of TMD and impaired mouth opening, a comprehensive approach is often used. For example, wearing a mouthguard is combined with exercises and periodic physiotherapy procedures, and, if necessary, with the prescription of an anti-inflammatory medication. The patient’s habits are also very important: it is worth giving up harmful habits such as biting nails, holding the phone between the shoulder and ear, sleeping face down, supporting the chin with the hand, and so on.

Joint efforts by the doctor and patient usually produce good results. In most cases, it is possible to reduce pain, restore the normal range of mouth opening, and improve quality of life. With timely treatment, 90% of patients restore normal jaw function within 3–6 months.

The main thing is not to ignore the problem, to seek help in time, and to follow medical recommendations. Your health is worth regaining a free and painless smile without any jaw “locking.”

This article does not replace a medical consultation. For complete and personalized information, please consult your dentist.