Many people grind their teeth at night. Grinding of teeth is more common at night while you are asleep. Grinding of teeth, which is also known as Bruxism, can cause loss of enamel and overall loss of tooth height which can lead to other problems such as jaw pain. Night guard is a moulded plastic appliance which acts as a barrier between upper and lower teeth. The guard will be inserted into the mouth to prevent teeth from grinding against one another.