It was first made in the 1930s. Its research was started in the 1980s for the treatment of sleep apnea.
It holds the jaw forward to prevent the back of the throat from collapsing. There are currently over 70 different designs and a dentist delivers them. Some are not approved for sleep apnea, only snoring.
It can be effective especially in patients having mild to moderate obstructive sleep apnea. It is less effective than cPAP but most people find it much more comfortable.
Since sleep apnea is potentially a life threatening condition, a physician best treats it and if an oral appliance is the treatment of choice it is best provided by a dentist with extensive experience and education in the area of sleep medicine.