Oral appliances come in a number of different designs. In general, they fall into two categories: fixed and adjustable.
A fixed OA is made from a single piece of plastic that contains both the upper and lower dental traythe part that fits over your teeth.
With an adjustable OA, the upper and lower trays are separate pieces joined by a hinge. The adjustable design makes it possible to find the best extension for the jaw so you can get the most benefit out of treatment.
You can buy pre-made OAs, but for the best result, the appliance should be custom-made to fit your mouth. To get a fit that is comfortable and effective, a dentist must first make a cast of your mouth and use it to create the upper and lower trays. The dentist, preferably one with experience caring for patients with temporomandibular joint conditions, also needs to determine the maximum extension of the lower jaw to create the device.
With appliances made from a single piece, the extension is typically set at between 50 and 80 percent of the maximum potential extension. Adjustable appliances, however, are designed to provide a range of extensions.