Bruxism during the day. The ICDS-R defined sleep bruxism as "a stereotyped movement disorder characterized by grinding or clenching of the teeth during sleep", classifying it as a parasomnia. The second edition (ICSD-2) however reclassified bruxism to a "sleep related movement disorder" rather than a parasomnia. Alternatively, bruxism can be divided into "primary bruxism" (also termed "idiopathic bruxism"), where the disorder is not related to any other medical condition, or "secondary bruxism", where the disorder is associated with other medical conditions. Secondary bruxism includes iatrogenic causes, such as the side effect of prescribed medications. Another source divides the causes of bruxism
Bruxism strong association between TMD and bruxism. A systematic review investigating the possible relationship concluded that when self-reported bruxism is used to diagnose bruxism, there is a positive association with TMD pain, and when stricter diagnostic criteria for bruxism are used, the association with TMD symptoms is much lower. In severe, chronic cases, bruxism can lead to myofascial pain and arthritis of the temporomandibular joints. The muscles of mastication (the temporalis, masseter, medial and lateral pterygoid muscles) are paired on either side and work together to move the mandible, which hinges and slides around its dual articulation with the skull at