Bruxing is the act of chewing or grinding ones own teeth. Some 95% of all Americans brux to one degree or another. Factors that can increase the likelihood of bruxing are stress or bite misconfiguration. Most bruxing in humans is unconscious, and it is extremely common to brux while sleeping.
Bruxing can cause damage to teeth and dental work, as well as cause facial muscle pain or swelling of the temporomandibular joint (jaw joints). Because so much of human bruxing is unconscious, it is a difficult problem to prevent. Bite reconfiguration and protective sleeping gear are common treatment, but few chronic bruxers seek treatment.
In humans, chronic bruxing is considered a disorder, but in other mammals it is a survival adaption. Most rodents have teeth that grow indefinitely, and they need to continue to wear them down to prevent them from injuring their mouths. Rats often brux when content and relaxed, producing a slight clicking and grinding noise. Often rats will brux so powerfully that their jaw muscles will cause their eyes to vibrate or pulse in their sockets (termed "eye boggling" by fancy rat enthusiasts). Other rodents, such as the beaver, wear their teeth primarily through use, but do also brux "recreationally".