Teeth grinding (bruxism) is the involuntary clenching, grinding and gnashing of the teeth. It is thought that about half of the population bruxes from time to time, while around five per cent are habitual and forceful tooth grinders. Bruxism can be a physical expression of stress; for example, susceptible people may tend to grind their teeth when they are angry, concentrating hard on a particular task or feeling anxious. Generally, the person doesn’t realise that they grind their teeth in their sleep. The spouse or partner who shares their bed (and hears the grinding noises at night) is often the first to notice the problem.