Limited Mouth Opening: Causes, Symptoms and Treatment Options

Jaw opening disorders (trismus) is a painful condition in which the jaws do not fully open. In addition to pain, trismus can lead to problems with eating, speaking, and oral hygiene, as a person cannot open their mouth wide. Trismus occurs when a person cannot open their mouth more than 35 millimeters. It can occur as a result of jaw injury, oral surgery, infection, cancer or radiation therapy, and due to TMJ (temporomandibular joint) inflammation.

Why does jaw locking occur?

Jaw opening disorders are any condition that prevents normal wide mouth opening. Often these problems are associated with temporomandibular joint (TMJ) dysfunction – the joint that connects the lower jaw to the skull. It is this joint and the surrounding masticatory muscles that provide jaw movement during talking, chewing, and yawning.

If the functioning of this complex system is disrupted, temporomandibular dysfunction (TMD) occurs. This is a generalized name for a group of dozens of conditions that cause pain and improper functioning of the TMJ and masticatory muscles.

With normal functioning, the condylar head moves smoothly in the articular fossa, while with dysfunction it can shift or lock, causing pain and movement restriction.

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 seems to lock, and it cannot move freely.

Trismus can be short-term or chronic. In mild cases, discomfort and jaw stiffness may pass on their own, but sometimes the problem becomes prolonged and requires treatment. According to data from the National Institute of Dental and Craniofacial Research, approximately 10-12 million adults in the US have pain in the TMJ area, and in women aged 35-44 this occurs twice as often as in 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 indicating TMJ dysfunction:

• Inability to fully open the mouth. There is a feeling as if something is interfering or “holding” the jaw. Such restriction is often accompanied by muscle tension.
• Pain and discomfort in the jaw, near the ear or in the head. Often the pain intensifies when trying to move the jaw or when chewing or moving the jaw. A person may find it painful to open their 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 other people can hear these sounds. If clicking is not accompanied by pain or locking, usually specific treatment is not needed.
• Feeling of locking, jaw blocking. May occur episodically, the mouth may remain either in a half-open state or it will be difficult for the person to unclench clenched jaws. The patient may not control jaw movement, and then it suddenly falls into place with a click.
• Lower jaw displacement during movements. When trying to open the mouth wide, the lower jaw may not move smoothly down, but deviate to the side. This can be noticed by looking in a mirror: the chin shifts to the left or right.

The above symptoms can occur both in combination and separately. If you have at least one of these symptoms and they do not go away, you should consult a doctor.

What are the causes?

Problems with mouth opening can be caused by several conditions:

• TMJ dysfunction (TMD syndrome). This is the most common cause of mouth opening problems. Dysfunction can be caused by displacement of the articular disc, stretching of ligaments, inflammation or microtrauma in the joint. Normally, each TMJ has a cartilaginous disc that regulates jaw movements. If the disc is displaced, jaw movement is disrupted. This causes pain, difficulty opening the mouth, and jaw clicking. Temporomandibular dysfunction is often accompanied by muscle spasm around the joint.
• Jaw or facial injuries. Any damage in the area of the joint or lower jaw can cause problems with its movement. This includes blows to the chin or jaw, falls, traffic accidents, sports injuries, etc. For example, TMJ dislocation leads to the fact that a person cannot close their mouth or, conversely, open it. Lower jaw fractures also cause significant movement restrictions. Disturbances in joint function may remain even if some time has passed after the injury.
• Bruxism (teeth grinding). Chronic nighttime grinding or daytime unconscious teeth clenching creates excessive load on the TMJ and masticatory muscles. Bruxism is often associated with stress and anxiety. Constant muscle overstrain leads to their painful spasm, which complicates mouth opening and causes morning jaw stiffness. In addition, strong pressure when clenching teeth can damage the articular disc and cartilage. Stress itself also contributes to jaw muscle tension. Thus, stress and bruxism are significant factors in the development of TMJ dysfunction.
• Joint arthritis. Degenerative or inflammatory diseases can also affect the temporomandibular joints. For example, osteoarthritis (age-related “wear” of cartilage) can cause crunching and limited mobility. Rheumatoid arthritis – a systemic inflammatory disease also sometimes affects the TMJ, leading to pain and stiffness. Arthritic changes damage cartilage, deform articular surfaces, so problems may occur when opening the mouth.
• Bite disorders and dentofacial anomalies. Incorrect relationship of upper and lower jaw teeth or a sharp change in bite that occurs after tooth loss is sometimes associated with TMD development. In some cases, a strong imbalance in the mouth can overload the joint. For example, if the jaw is displaced and moves incorrectly, over time this can cause pain and clicking.
• Tumors and other diseases. A rare but serious cause of mouth opening problems may be tumor processes in the maxillofacial area. Benign or malignant tumors in the masticatory muscles, parotid gland, mandibular bone, or the joint itself can interfere with jaw movement or cause muscle spasm. In addition, patients with malignant head and neck tumors often face trismus after treatment. According to research in the Journal of Clinical Oncology, up to 40% of people undergoing radiation therapy have mouth opening problems. Radiation causes fibrosis (scarring) of muscles and joint tissues, which limits their mobility.

In 60% of cases, the cause of mouth opening problems is TMD, in 20% – injuries, in 15% – bruxism, in 5% – other factors.

Other diseases that can lead to trismus:

• tetanus;
• infections in the pharynx area, tonsils or masticatory muscles;
• purulent abscesses of the lower jaw;
• scar changes after operations on the maxillofacial area.

Such conditions are not common, but should be kept in mind, especially if mouth opening problems appeared after oncological disease treatment, severe infection, or surgical intervention.
In young patients, TMJ dysfunction and bruxism are more common, while in older patients – arthrosis. There are cases when it is difficult to establish the exact cause of disorders, especially when the patient has several factors combined. For example, a person with arthritis develops muscle spasm due to stress. A qualified doctor will pay attention to all possible factors, as the success of treatment depends on the correct determination of the cause.

Joint clicking is observed in 75% of patients with TMD, while complete jaw blockage – only in 15-20% of cases.

When to see a doctor

Minor mouth opening disorders 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, sharply increased, or interferes with eating;
• cannot fully open the mouth or close the jaws;
• the jaw is locked in an open or closed position;
• difficulty speaking and eating, and this affects quality of life;
• symptoms do not disappear for several days, or worsen;
• swelling, high temperature, or other signs of inflammation in the joint area;
• facial injury after which mouth opening disorders occurred.

Remember that early seeking help can prevent worsening of the condition. If you delay, you can get complications – from chronic pain to irreversible joint damage.

How TMJ pathology is diagnosed

Proper diagnosis is key to successful treatment of TMJ pathology. The doctor will begin with detailed history taking, asking when and how symptoms appeared, what provokes pain, whether there were injuries, crunching or locking.

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

• palpates areas around the joints and masticatory muscles to identify where it hurts;
• detects whether there is clicking or friction during jaw movement;
• assesses how wide the patient can open their mouth and whether there is jaw displacement.

What instrumental examination methods exist

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

• radiography or panoramic image of teeth and jaws: gives a general idea of the condition of bones, presence of arthritic changes, dislocations, fractures;
• computed tomography (CT) of TMJ: allows obtaining detailed layered images of bone structures of the joint, and well detects bone changes, for example, deformations of the articular process, consequences of injuries or arthritis, CT is effective for bone changes in 90% of cases;
• magnetic resonance imaging (MRI) of TMJ: is the optimal method for assessing soft tissues of the joint: articular disc, ligaments, muscles. MRI shows whether the disc is displaced or damaged, whether there is inflammation in the joint. MRI detects disc displacement with 95% accuracy;
• TMJ arthroscopy: minimally invasive procedure in which a tiny video camera is inserted directly into the joint cavity through a puncture. Such examination is prescribed only in complex cases, and allows examining the internal structures of the joint and even performing therapeutic manipulations.

During diagnosis, it is also important to exclude other conditions that may affect jaw functions, namely otitis, neuralgias, dental problems. Only after a comprehensive examination is a final diagnosis established and a treatment plan developed.

What is the treatment

Treatment of mouth opening disorders 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-help. If symptoms are moderate, the doctor may limit themselves to monitoring the condition without serious interventions. The patient will be recommended to “unload” the joint and give it rest: not eat hard food and try not to open the mouth wide during yawning. You can also independently do light massage of the masticatory muscles. Such conservative methods are often sufficient, as according to research, in many cases TMD symptoms disappear without any complex procedures.
• Therapeutic gymnastics and physiotherapy. Special exercises for the jaw help restore its normal movement and strengthen muscles. A doctor or physiotherapist will select a complex that will include exercises such as smooth mouth stretching, jaw movement forward-backward and sideways, etc. Physiotherapeutic procedures are used to reduce pain and muscle spasm. Some patients are helped by the ability to control jaw muscle tension through conscious relaxation. These methods are especially useful if the cause of the ailment is stress and the habit of clenching jaws. Physiotherapy is aimed not only at symptoms, but also at eliminating functional blockage: manually the therapist can stretch and knead the masticatory muscles, which improves joint mobility. According to research in Physical Therapy Journal, physiotherapy reduces pain by 60-70% within 4-6 weeks.
• Mouthguards. One of the main treatment methods for bruxism and jaw overstrain is the use of special mouthguards. A mouthguard is an individual plastic overlay that is put on teeth at night. During uncontrolled nighttime teeth clicking, the mouthguard protects not only the teeth themselves, but also reduces overload of joints and muscles. There are different types of mouthguards: soft silicone or hard acrylic, upper or lower. It is worth noting that mouthguards do not treat structural changes, but are a means of protection and unloading.
• Drug treatment. Medications are used to relieve pain, inflammation, and muscle spasm. The most commonly used are non-steroidal anti-inflammatory drugs, such as ibuprofen or naproxen. For severe pain, more powerful painkillers or muscle relaxants that relax the masticatory muscles may be prescribed for a short course. Sometimes low doses of tricyclic antidepressants or sedative drugs are used, which helps break the “pain – tension – pain” cycle, improve sleep and reduce bruxism symptoms. It is important to follow the doctor’s prescriptions and not self-medicate, as some of these drugs may have side effects.
• Surgical treatment. Used only if conservative therapy did not give results. TMJ operations are performed rarely, only with strict indications, as they have risks, like any operation.

Modern surgical techniques are minimally invasive:

• arthrocentesis: joint lavage to remove inflammatory fluid and increase mobility;
• arthroscopic surgery: instruments are inserted through a small puncture with which the surgeon can remove scars, release a pinched disc, or eliminate minor defects;
• open joint surgery: arthroplasty, reconstruction, or joint prosthetics – this is an extreme step that is taken only when other methods do not help.

In the treatment of TMD and mouth opening disorders, a comprehensive approach is often used. For example, wearing a mouthguard is combined with exercises and periodic physiotherapy procedures, and if necessary – with prescription of an anti-inflammatory drug. Patient habits also matter greatly: it is worth giving up bad habits of biting nails, holding the phone with your shoulder near your ear, sleeping face down, propping your chin with your hand, etc.

Joint actions of the doctor and patient usually give good results. In most cases, it is possible to achieve pain reduction, restoration of normal mouth opening amplitude, and improvement of 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, seek help in time, and follow recommendations. Your health is worth it to return yourself a free and painless smile without any jaw “locking”!

This article does not replace a doctor’s consultation. If you have symptoms, consult a dentist.