io9 provides an in-depth explanation of sleep bruxism.
According to Maria Clotilde Carra, a Doctor of Medicine in Dentistry at Rothschild Hospital in Paris, “bruxers” grind their teeth at least two to four times per hour of sleep. When grinding reaches this level of frequency, it gets diagnosed as a sleep disorder. As an important distinction, some 60% of the population exhibits a less intense chewing-like activity when they sleep, but this isn’t sleep bruxism—it’s actually a psychological sleep related movement.
“Bruxism is a nightmare for dentists who see their beautiful restorative work being rapidly destroyed by their patients who keep grinding over it,” says Carra. “Of course this is a problem, and not only for the dentists, but also for the patient who keep losing masticatory function and need to repeat or repair the dentition many many times.”