Bruxism, or the "gnashing of teeth" is an oral habit that occurs in most humans at some time in their lives, usually during stressful times. In most people, bruxism is mild enough not to be a health problem and only causes minor discomfort.
Bruxism can occur both during the day or night, but it is during sleep that the majority of health issues can occur, this includes during short naps. Bruxism is one of the most common sleep disorders which accompanies Sleep Apnea. Some bruxism activity is rhythmic (like chewing), and some is sustained such as clenching. Researchers classify bruxism as "a habitual behaviour", and also a sleep disorder.