Possible associations
TMD has been suggested to be associated with other conditions or factors, with varying degrees of evidence and some more commonly than others. E.g. It has been shown that 75% of people with TMD could also be diagnosed with fibromyalgia, since they met the diagnostic criteria, and that conversely, 18% of people with fibromyalgia met diagnostic criteria for TMD. A possible link between many of these chronic pain conditions has been hypothesized to be due to shared pathophysiological mechanisms, and they have been collectively termed "central sensitivity syndromes", although other apparent associations cannot be explained in this manner. Recently a plethora of research has substantiated a causal relationship between TMD and Obstructive Sleep Apnea (OSA). Severe TMD restricts oral airway opening, and can result in a retrognathic posture that results in glossal blockage of the oropharynx as the tongue relaxes in sleep. This mechanism is exacerbated by alcohol consumption, as well as other chemicals that result in reduced myotonic status of the oropharynx. Obstructive sleep apnea. Headache. Chronic neck pain. Chronic back pain. Systemic joint laxity. Rheumatoid arthritis. Irritable bowel syndrome. Interstitial cystitis. Regular scuba diving. Pathophysiology
Anatomy and physiology
Temporomandibular joints
The temporomandibular joints are the dual articulation of the mandible with the skull. Each TMJ is classed as a "ginglymoarthrodial" joint since it is both a ginglymus (hinging joint) and an arthrodial (sliding) joint, and involves the condylar process of the mandible below, and the articular fossa (or glenoid fossa) of the temporal bone above.
Normally splints are only worn during sleep, and therefore probably do nothing for people who engage in parafunctional activities during wakefulness rather than during sleep. There is slightly more evidence for the use of occlusal splints in sleep bruxism than in TMD. A splint can also have a diagnostic role if it demonstrates excessive occlusal wear after a period of wearing it each night. This may confirm the presence of sleep bruxism if it was in doubt. Soft splints are occasionally reported to worsen discomfort related to TMD. Specific types of occlusal splint are discussed below. A stabilization splint is a hard acrylic splint that forces the teeth to meet in an "ideal" relationship for the muscles of mastication and the TMJs. It is claimed that this technique reduces abnormal muscular activity and promotes "neuromuscular balance". A stabilization splint is only intended to be used for about 2–3 months. It is more complicated to construct than other types of splint since a face bow record is required and significantly more skill on the part of the dental technician. This kind of splint should be properly fitted to avoid exacerbating the problem and used for brief periods of time. The use of the splint should be discontinued if it is painful or increases existing pain.