Night Guards are helpful for bruxism (teeth grinding) caused by sleep disorder, crooked or missing teeth or stress. Night Guards are custom made by your dentist from soft material to fit your teeth these tend to be of a higher quality and superior fit, as they are made in a special laboratory from an impression of your mouth carefully taken by a dental professional. This is generally a more expensive device than one purchased over-the-counter, but can be more comfortable to wear. The night guard slips over the upper and lower teeth and prevents contact between them. It helps relieve some pressure of grinding or clenching, which can damage delicate jaw joints. Regardless of where a night guard is purchased, its main function is to prevent the surfaces of your teeth from grinding together, causing you to chip and crack your teeth and strain your jaw muscles.