Temporomandibular Joint Disorder (TMD) describes conditions affecting the jaw joint and the muscles that control jaw movement. The temporomandibular joints are the complex sliding hinges connecting the lower jaw to the skull, located just in front of the ears. Symptoms include chronic pain or tenderness in the jaw, facial pain, limited movement, and audible clicking or popping sounds when moving the jaw.
A frequent contributing factor to TMD is the hyperactivity of the jaw muscles, often caused by unconscious clenching or grinding of the teeth, a habit called bruxism. This excessive strain can lead to inflammation and discomfort. An oral appliance, often called a mouth guard, is a non-invasive treatment designed to manage these symptoms by altering the bite and reducing muscle tension.
Terminology and Types of Oral Appliances
While many people use the term “mouth guard,” devices for treating TMD are accurately called oral splints or orthotics by dental professionals. Unlike generic, over-the-counter guards, effective TMD treatment requires a custom-fitted appliance. These custom devices are fabricated from hard acrylic and precisely molded to the patient’s teeth to ensure proper contact and stability.
Two primary categories of oral splints are used for TMD management. The most common is the stabilization splint, also known as a flat-plane splint, which covers all the teeth in one arch. Its design focuses on relaxing the jaw muscles and reducing the effects of clenching and grinding.
The second type is the repositioning splint, which guides the lower jaw into a new, predetermined position. This type is used when the joint’s internal structures, like the articular disc, are displaced. The choice depends on the specific diagnosis and the underlying cause of the patient’s jaw discomfort.
Disrupting the Bite Reflex to Relieve Muscle Strain
The primary function of a stabilization splint is to interrupt the muscle hyperactivity cycle that characterizes bruxism and contributes to TMD pain. The appliance provides a smooth, flat surface for the opposing teeth, preventing the cusps of the upper and lower teeth from interlocking. This elimination of occlusal interference is recognized as “deprogramming.”
By preventing the teeth from finding a familiar fit, the appliance sends a different signal to the central nervous system. This disruption inhibits the involuntary clenching reflex, forcing the jaw muscles to cease their hyperactive strain. This mechanism promotes the relaxation of the major muscles of mastication, such as the masseter and temporalis muscles.
The reduction in muscle tension is the cause of pain relief for many patients suffering from myofascial pain. The appliance allows fatigued muscles to find a more relaxed resting length, decreasing associated strain and chronic headaches.
Cushioning the Joint and Managing Pressure
Beyond muscle relaxation, the oral appliance serves a mechanical function as a shock absorber and physical barrier. It protects the teeth from the wear and tear (attrition) that results from nocturnal grinding and clenching. The appliance distributes bite forces evenly across the dental arch, preventing excessive pressure from concentrating on individual teeth.
The appliance slightly increases the vertical space between the jaws, which helps unload the temporomandibular joint. This cushioning effect reduces direct pressure on the joint’s internal components, including the articular disc and joint surfaces. By lessening this mechanical load, the splint helps manage inflammation within the joint structures.
The appliance provides a stable platform and minimizes forces generated during clenching, placing the jaw in a favorable position for healing. The splint is often worn primarily at night, when involuntary bruxism is most common, and consistent use helps maintain reduced muscle tension and joint pressure.