Anatomy and physiology<unk><unk> s The<unk><unk> s are the dual articulation of the mandible with the skull. Each TMJ is classed as a "ginglymoarthrodial"<unk>  since it is both a ginglymus (hinging<unk>  and an arthrodial (sliding)<unk> , and involves the condylar process of the mandible below, and the articular fossa (or glenoid fossa) of the temporal bone above. Between these articular surfaces is the articular disc (or meniscus), which is a biconcave, transversely oval disc composed of dense fibrous connective tissue. Each TMJ is covered by a fibrous capsule. There are tight fibers connecting the mandible to the disc, and loose fibers which connect the disc to the temporal bone, meaning there are in effect 2<unk>  capsules, creating an upper<unk>  space and a lower<unk>  space, with the articular disc in between. The synovial membrane of the TMJ lines the inside of the fibrous capsule apart from the articular surfaces and the disc. This membrane secretes synovial fluid, which is both a lubricant to fill the<unk>  spaces, and a means to convey nutrients to the tissues inside the<unk> . Behind the disc is loose vascular tissue termed the "bilaminar region" which serves as a posterior attachment for the disc and also fills with blood to fill the space created when the head of the condyle translates down the articular eminence. Due to its concave shape, sometimes the articular disc is described as having an anterior band, intermediate zone and a posterior band. When the mouth is opened, the initial movement of the mandibular condyle is rotational, and this involves mainly the lower<unk>  space, and when the mouth is opened further, the movement of the condyle is translational, involving mainly the upper<unk>  space. This translation movement is achieved by the condylar head sliding down the articular eminence, which constitutes the front border of the articular fossa. The function of the articular eminence is to limit the forwards movement of the condyle. The ligament directly associated with the TMJ is the<unk>  ligament, also termed the lateral ligament, which really is a thickening of the lateral aspect of the fibrous capsule. The stylomandibular ligament and the sphenomandibular ligament are not directly associated with the<unk>  capsule. Together, these ligaments act to restrict the extreme movements of the<unk> . Muscles of mastication The muscles of mastication are paired on each side and work together to produce the movements of the mandible. The main muscles involved are the masseter, temporalis and medial and lateral pterygoid muscles. File:Gray383.Left medial and lateral pterygoid muscles File:Gray382.Left temporalis muscle File:Gray378 (masseter highlight).Left masseter muscle (red highlight) They can be thought of in terms of the directions they move the mandible, with most being involved in more than one type of movement due to the variation in the orientation of muscle fibers within some of these muscles. * Protrusion – Lateral and medial pterygoid. * Retraction – Posterior fibers of temporalis (and the digastric and geniohyoid muscles to a lesser extent). * Elevation – Anterior and middle fibers of temporalis, the superficial and deep fibers of masseter and the medial pterygoid. * Lateral movements – Medial and lateral pterygoid (the ipsilateral temporalis and the pterygoid muscles of the contralateral side pull the mandible to the ipsilateral side). Each lateral pterygoid muscle is composed of 2 heads, the upper or superior head and the lower or inferior head. The lower head originates from the lateral surface of the lateral pterygoid plate and inserts at a depression on the neck of mandibular condyle, just below the articular surface, termed the pterygoid fovea. The upper head originates from the infratemporal surface and the infratemporal crest of the greater wing of the sphenoid bone. The upper head also inserts at the fovea, but a part may be attached directly to the<unk>  capsule and to the anterior and medial borders of the articular disc. The 2 parts of lateral pterygoid have different actions. The lower head contracts during mouth opening, and the upper head contracts during mouth closing. The function of the lower head is to steady the articular disc as it moves back with the condyle into the articular fossa. It is relaxed during mouth closure. Mechanisms of symptoms<unk>  noises Noises from the TMJs are a symptom of dysfunction of these<unk> s. The sounds commonly produced by<unk>  are usually described as a "click" or a "pop" when a single sound is heard and as "crepitation" or "crepitus" when there are multiple, grating, rough sounds. Most<unk>  sounds are due to internal derangement of the<unk> , which is instability or abnormal position of the articular disc. Clicking often accompanies either jaw opening or closing, and usually occurs towards the end of the movement. The noise indicates that the articular disc has suddenly moved to and from a temporarily displaced position (disk displacement with reduction) to allow completion of a phase of movement of the mandible. If the disc displaces and does not reduce (move back into position) this may be associated with locking. Clicking alone is not diagnostic of<unk>  since it is present in high proportion of the general population, mostly in people who have no pain. Crepitus often indicates arthritic changes in the<unk> , and may occur at any time during mandibular movement, especially lateral movements. Perforation of the disc may also cause crepitus. Due to the proximity of the TMJ to the ear canal,<unk>  noises are perceived to be much louder to the individual than to others. Often people with<unk>  are surprised that what sounds to them like very loud noises cannot be heard at all by others next to them. However, it is occasionally possible for loud<unk>  noises to be easily heard by others in some cases and this can be a source of embarrassment e.g. when eating in company. Pain Pain symptoms in<unk>  can be thought of as originating from the<unk>  (arthralgia), or from the muscles (myofascial), or both. There is a poor correlation between<unk>  pain severity and evidence of tissue pathology. Generally, degenerative<unk>  changes are associated with greater pain. Myofascial pain Pain originating from the muscles of mastication as a result of abnormal muscular function or hyperactivity. The muscular pain is frequently, but not always, associated with daytime clenching or nocturnal bruxism. Limitation of mandibular movement The jaw deviates to the affected side during opening, and restricted mouth opening usually signifies that both TMJs are involved, but severe trismus rarely occurs. If the greatest reduction in movement occurs upon waking then this may indicate that there is concomitant sleep bruxism. In other cases the limitation in movement gets worse throughout the day. The jaw may lock entirely. Limitation of mandibular movement itself may lead to further problems involving the TMJs and the muscles of mastication. Changes in the synovial membrane may lead to a reduction in lubrication of the<unk>  and contribute to degenerative<unk>  changes. The muscles become weak, and fibrosis may occur. All these factors may lead to a further limitation of jaw movement and increase in pain. Degenerative<unk>  disease, such as osteoarthritis or organic degeneration of the articular surfaces, recurrent fibrous or bony ankylosis, developmental abnormality, or pathologic lesions within the TMJ. Myofascial pain syndrome. Referred<unk>  pain Sometimes<unk>  pain can radiate or be referred from its cause (i.e. the TMJ or the muscles of mastication) and be felt as headaches, earache or toothache. Due to the proximity of the ear to the<unk><unk> , TMJ pain can often be confused with ear pain. The pain may be referred in around half of all patients and experienced as otalgia (earache). Conversely,<unk>  is an important possible cause of secondary otalgia. Treatment of<unk>  may then significantly reduce symptoms of otalgia and tinnitus, as well as atypical facial pain. Despite some of these findings, some researchers question whether<unk>  therapy can reduce symptoms in the ear, and there is currently an ongoing debate to settle the controversy.
Temporomandibular joint dysfunction
Impacted wisdom teeth
Facial nerve paralysis
Eustachian tube dysfunction
Orofacial myofunctional disorders
Barodontalgia
Ear pain
Orofacial pain