Bruxism of bruxism. Clenching the teeth is generally displayed by humans and other animals as a display of anger, hostility or frustration. It is thought that in humans, clenching the teeth may be an evolutionary instinct to display teeth as weapons, thereby threatening a rival or a predator. The phrase "to grit one's teeth" is the grinding or clenching of the teeth in anger, or to accept a difficult or unpleasant situation and deal with it in a determined way. In the Bible there are several references to "gnashing of teeth" in both the Old Testament, and the New Testament, where
Bruxism in research declined from over 60% of publications in the period 1966–86 to about 10% in the period 1997–2007. In the 1960s, a periodontist named Sigurd Peder Ramfjord championed the theory that occlusal factors were responsible for bruxism. Generations of dentists were educated by this ideology in the prominent textbook on occlusion of the time, however therapy centered around removal of occlusal interference remained unsatisfactory. The belief among dentists that occlusion and bruxism are strongly related is still widespread, however the majority of researchers now disfavor malocclusion as the main etiologic factor in favor of a more multifactorial, biopsychosocial model