A common cause of tooth wear, bruxism isn’t something to ignore. Bruxism (BRUK-siz-um) is a condition in which you grind, gnash or clench your teeth. If you have bruxism, you may unconsciously clench your teeth when you're awake (awake bruxism) or clench or grind them during sleep (sleep bruxism). Sleep bruxism is considered a sleep-related movement disorder.