The temporomandibular joint – the TMJ – is
the joint between the lower jawbone – the mandible – and the temporal bone of the skull.
The TMJ is responsible for jaw movement and enables chewing, talking and yawning. Temporomandibular
disorders, or TMD, refer to a group of conditions characterized by pain in the jaw area and
limited movement of the mandible. TMD may be caused by problems in the joint itself
or in the muscles surrounding the joint. Problems in the joint include: arthritis, inflammation
and internal derangements. When the problem is in the muscles, the condition is called
myofascial pain syndrome. Myofascial pain syndrome is very common and
can occur in patients with a normal temporomandibular joint. The syndrome is characterized by presence
of hyperirritable spots located in skeletal muscles called trigger points. A trigger point
can be felt as a nodule of muscle with harder than normal consistency. Palpation of trigger
points may elicit pain in a different location. This is called referred pain.
Trigger points are developed as a result of muscle overuse. Commonly, the muscles of chewing,
or mastication, are overworked when patients excessively clench or grind their teeth unconsciously
during sleep. The medical term for this condition is “nocturnal bruxism”. A trigger point
is composed of many contraction knots where individual muscle fibers contract and cannot
relax. The sustained contraction of muscle sarcomeres compresses local blood supply,
resulting in energy shortage of the area. This metabolic crisis activates pain receptors,
generating a regional pain pattern that follows a specific nerve passage. The pain patterns
are therefore consistent and are well documented for various muscles.
Trigger points in the masseter refer pain to the cheeks, lower jaw, upper and lower
molar teeth, eyebrow, inside the ear and around the TMJ area. Trigger points in the temporalis
are also associated with headache and toothache from upper teeth. The main culprits of myofascial
pain in the TMJ area are the pterygoid muscles. Trigger points in medial pterygoid refer pain
to the TMJ region in front of the ear, inside the mouth and upper outside of the neck. They
may also manifest as sore throat and difficulty swallowing. Pain from lateral pterygoid trigger
points can be felt in front of the ear and on the upper jaw.
Treatments aim to address bruxism, to relieve muscle spasm and release trigger points. Treatment
options include: – Therapies: stress management, behavior therapy,
biofeedback – to encourage relaxation. – Dental night guards: Splints and mouth guards
– to protect the teeth from damage. – Medication: pain relievers, muscle relaxants,
botox injections. – Trigger points release techniques such as
needling and “spray and stretch”.