What is Temporomandibular Dysfunction?
The Temporomandibular Joint (TMJ) is located where the jaw bone, known as the mandible, meets the temporal bone of the skull. It is involved in breathing, chewing, making facial expressions, yawning and talking and is therefore the most used joint in your body. Signs of TMJ dysfunction can include pain and tenderness, jaw clicking and popping or even grinding, inability to fully close the mouth or alternatively, limited mouth opening. There is also an intra-articular disc within the joint capsule which can be a source of pain due to either inflammation or degeneration. Other symptoms linked to TMJ dysfunction can include pain on chewing, headaches, waking up with jaw soreness, tinnitus or ringing ears. During a dental check-up, the dentist may point out excess wearing of the teeth from clenching or grinding.
The movements that occur at the TMJ are
- Mandibular depression – jaw dropping down
- Mandibular elevation – jaw closing
- Lateral deviation to the left and right
- Mandibular protrusion – jaw coming forward
- Mandibular retrusion – jaw coming backwards
What causes TMJ Pain?
TMJ pain arises from dysfunction either within the muscles or the joint itself. The origin of the pain will be examined during a thorough subjective and objective examination conducted by your Physiotherapist. Some common causes of TMJ pain include:
- Overactive jaw muscles, including the muscles of mastication (the chewing muscles)
- Teeth grinding and jaw clenching, meaning there can be an element of stress
- Poor cervical posture and movement patterns
- Diet and gum chewing frequency
- Inflammatory changes in the joint which can be caused by a direct blow to the chin or jaw, causing swelling and bruising
- Fractures to the mandible which can occur with a direct blow to the jaw or the chin
- Indirect injury such as whiplash
- Dental or orthodontic procedures
- Degenerative arthritis can be seen on x-ray or MRI – may also present with some crepitus (grinding or cracking in the joint) – usually seen in over 50s or in those that have previously suffered an injury.
- Inflammatory Joint Diseases such as gout, Rheumatoid arthritis, infective arthritis and ankylosing spondylitis
- Hypermobility, excessive movement at the joint can create issues, often accompanied by crepitus and while initially not painful, over long term it can cause disc degeneration
Commonly referred to as “lock jaw”, trismus is an acute muscle spasm that causes pain and limited jaw movement. Lock jaw often affects the chewing muscles, known as the muscles of mastication and can be caused by prolonged mouth opening e.g. dental procedures, stress, infection, trauma, neurological conditions such as MS or from a side effect of medication. The decreased range of movement at the TMJ can make chewing, brushing your teeth and even swallowing difficult. While the definition varies, some classify trismus as a mouth opening of less than 40mm, although some studies consider it even as low as less than 20mm. Note that normal range is thought to be between 40-60mm, with men having a larger range than woman.
Trismus is prevalent in head and neck cancer patients, especially those who have undergone radiation therapy. In most severe cases it can cause aspiration of food/fluids and difficulty breathing. Management of trismus is best determined by the cause of the muscle spasm.
Treatment of Temporomandibular Joint Dysfunction
Physiotherapy is advised after initial acute phase to reduce swelling, increase joint range of movement, break down any scar tissue and improve muscle strength.
A physiotherapy assessment will commence with a thorough subjective interview. Posture will be assessed including neck posture, jaw and tongue position, palpation of the TMJ looking for any possible swelling, joint hypomobility or hypermobility, range of movement of the jaw and neck. If symptoms are inflammatory in nature, then pain is likely to be irritable and care should be taken not to aggravate symptoms during assessment or treatment.
Treatment should address any issues identified during the assessment. For inflammatory dysfunction, anti-inflammatories and avoidance of aggravating activities should be the initial course of action. For those who have difficulty chewing, they may require a modified diet including softer food while pain improves or using a straw instead of opening the mouth to drink. Patients should avoid resting their chin on their hand, avoid chewing gum and any other chewy foods as well as food that requires a large mouth opening such as taking a bite from an apple or a large hamburger.
Soft tissue work can be very effective at releasing tight muscles in the jaw, base of skull and surrounding areas. Treatment of the neck muscles and joints can be especially helpful in resolving TMJ pain including joint mobilisation of any stiff joints found on assessment as well as making any postural corrections.
Botulinum toxin- A has emerged as a sought after treatment option for muscular TMJ disorders including bruxism and hyperactive muscles of mastication. Botulinum toxin is a natural poisonous by-product of a bacterium. FDA approved, this neurotoxin acts by inhibiting the release of acetylcholine, disabling muscle function at the neuromuscular junction. Botox A is injected into the active target muscle under the guidance of electromyograph. Effects will start to take effect at 2-7 days and can last between 8 and 12 weeks. Systematic reviews and meta analysis compared Botox A to Physiotherapy techniques such as myofascial manipulation and dry needling without clinically significant differences in pain scores. Another review compared pain scores at 6 weeks post Botox or dry needling actually supported dry needling.
There is limited evidence for exercise therapy for bruxism or muscular related jaw pain or following head and neck cancer. Exercise therapy is a non-invasive intervention that in certain populations can reduce the intensity and severity of pain. The Rocabado exercises are 6 exercises that are completed 6 times per day. These exercises aim to improve head and jaw posture.
Other treatments to consider:
- Once any acute inflammation has settled, heat can be applied, either a heat pack or a hot damp towel over the area for 10-20 mins.
- Muscle relaxants may be prescribed by a medical professional if muscle spasm is present or similarly antibiotics may be required if infection is the source of pain and dysfunction.
- Seek a dental opinion for any tooth aches or cavities that may cause uneven chewing or resting posture of the jaw. Night splints and mouth guards may be able to resolve the issue.
- Stress management may have a large positive impact on TMJ pain, especially when caused by stress and teeth grinding. Relaxation techniques, meditation, sleeping posture including pillow selection can all be useful.
- Chewing gum can provide activity for the mouth and strengthen the muscles of mastication. Only do this if recommended by a physio and it’s best to choose sugar free gum to limit tooth decay.
- If there is any damage to the facial nerve, then it may respond to facial exercises and electrical stimulation
- Surgery may be indicated if the pain originates from an intra-articular point, or there is a presence of a foreign body.
- A. Sipahi Calis, Z. Colakoglu, S. Gunbay, The use of botulinum toxin-a in the treatment of muscular temporomandibular joint disorders, Journal of Stomatology, Oral and Maxillofacial Surgery, Volume 120, Issue 4, 2019, Pages 322-325, ISSN 2468-7855 https://doi.org/10.1016/j.jormas.2019.02.015.
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- Mor N, Tang C, Blitzer A. Temporomandibular Myofacial Pain Treated with Botulinum Toxin Injection. Toxins (Basel). 2015 Jul 24;7(8):2791-800. doi: 10.3390/toxins7082791. PMID: 26213970; PMCID: PMC4549724.
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