A removable, custom-fitted plastic appliance that fits between the upper and lower teeth to prevent them from grinding against each other. Night guards are also known as dental guards, mouth guards, nocturnal bite plates, or bite splints. They work by putting a barrier between your teeth. When you clench your jaw, the night guard helps to lighten the tension and give cushion to the muscles in the jaw. This cushioning not only helps to prevent face and jaw pain, but also protects the enamel of your teeth.