Neuroplasticity and Central Sensitization in Orofacial Pain and TMD

Abstract

Temporomandibular disorders (TMD) are a group of musculoskeletal and neuromuscular conditions that involve the temporomandibular joint (TMJ), the masticatory muscles, and branches of the trigeminal nerve. TMD is the most common chronic oral facial pain disorder. Pain associated with TMD can be clinically expressed as myogenous or arthrogenous in etiology. The myogenous variant of TMD is characterized by pain in the muscles of mastication. The arthrogenous form of TMD is caused by pain in the joint leading to synovitis, capsulitis, or arthritis. Classically, mastication activity aggravates musculoskeletal pain. TMD pain is frequently associated with biomechanical dysfunction of the temporomandibular joint. This includes clicking or locking of the TMJ due to an anterior displaced disk, resulting in limited range of motion of the mandible. The diagnosis is based on the presence of symptoms such as periauricular pain related to mastication, joint noises (popping/clicking), limited mandible opening, jaw locking, and headaches. Orofacial pain includes several diagnoses: odontogenic, musculoskeletal, neurovascular, persistent idiopathic facial pain (PIFP), neuropathic pain, neuralgia, TMD, and headache. When there is a persistent and intense nociceptive input in a sensitized central nervous system, the patient becomes more reactive and experiences more pain with less provocation. Practitioners should have knowledge of this type of heterotopic pain when determining the origins of orofacial pain. Without deep understanding of the trigeminal system and mechanisms differentiating nociceptive and non-nociceptive pain, clinicians will most likely treat the reported symptoms instead of the underlying cause.