Do bruxism and temporomandibular disorders have a cause-and-effect relationship?

Controversy continues to exist over the putative role of bruxism in the etiology of temporomandibular disorders. A commonly held concept is that bruxism leads to signs and symptoms characteristic of one or more of the subdiagnoses of temporomandibular disorders, while another hypothesis suggests that bruxism is a temporomandibular disorder itself that sometimes coexists with other forms of temporomandibular disorders. Following a thorough review of the literature in this article, it is concluded that the relationship between bruxism and temporomandibular disorders is still unclear. Future research should examine longitudinal epidemiologic and clinical/experimental data to establish or refute a cause-and-effect relationship. In doing so, the existence of various sub-groups of temporomandibular disorders should be taken into account, and sleep-related bruxism should be discriminated from its daytime variant.