TMJ appliances may reduce the symptoms of TMD by reducing pressure on the jaw joints or realigning the bite. The standard TMJ appliance is a stabilization splint, which is also called a bite guard or bite plate. As The TMJ Association (TMJA) explains, a splint is a hard dental appliance made of acrylic resin that fits over the upper or lower teeth. The device prevents contact between the teeth, and when the teeth touch the splint, they're in the least harmful and most correct position, according to Cleveland Clinic . Splints are generally worn 24 hours a day, but dentists may also prescribe night guards that the patient wears while sleeping.