An oral appliance is a small device, similar to an orthodontic retainer or an athletic mouthguard. It is worn in the mouth during sleep to prevent the soft throat tissues from collapsing and obstructing the airway. Some appliances hold the lower jaw forward during sleep while others have direct effect on tongue position. Oral appliances relieve snoring and may treat OSA by realigning the jaw and/or tongue in relation to the head. Although oral appliances do not work on everybody, a well-made, well-fitted appliance may reduce or eliminate snoring, and may significantly relieve symptoms of OSA.