Bruxism is

Bruxism (teeth-grinding): The patient has an involuntary and forceful grinding of teeth during sleep. Though the bed paner repos loud sounds produced by grinding of teeth and destruction of the tooth enamel is obvious, the patient remains completely unaware of the episode(s). Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no. 140