An occlusal splint or night guard has many uses; it is used to treat bruxism (teeth grinding), teeth clenching and symptoms of TMD (temporo-mandibular joint disorders). An occlusal splint is an acrylic oral appliance that is custom made to fit over the top or bottom teeth and is usually worn while sleeping. It may also be worn during the day in severe cases. It is used to reduce grinding and clenching behaviours, prevent damage to the teeth, and reduce muscle and joint pain. An occlusal splint takes the brunt of the pressure that would otherwise be directed at your teeth—the splint is worn down while your teeth remain protected. An occlusal splint is designed to keep your jaw in a more relaxed position while you sleep.

Bruxism (grinding) is when you slide your teeth back and forth over each other, eventually wearing down your teeth. Grinding can be noisy enough at night to bother sleeping partners. Grinding puts pressure on the muscles, tissues, and other structures around your jaw. This can lead to jaw pain and soreness, headaches, earaches, and damaged teeth. Teeth may become shortened due to extensive grinding; tooth enamel can wear away causing teeth to become more sensitive to hot and cold; as well, the pressure from grinding can fracture teeth and crack fillings. Grinding also exacerbates any periodontal issues.

Clenching means you tightly hold your top and bottom teeth together, especially the back teeth. Like grinding, clenching can lead to jaw pain and other tooth related problems.

People can grind and clench subconsciously during both the day and night, although sleep-related bruxism is often the bigger problem because it is harder to control. The cause of bruxism is not completely agreed upon, but daily stress may be a trigger in many people.

Clenching and grinding can worsen existing dental or TMJ (temporo-mandibular joint) problems. The TMJ is the small hinge-like joint that connects the lower jaw to the upper jaw allowing you to chew and talk. There are a variety of approaches for treating TMD. One of first treatments recommended is the use of an occlusal splint because it is a non-invasive, reversible treatment. It often resolves the TMD without the need for surgery (which is a last resort).