Dental appliance used to treat sleep apnea is also called Mandibular Advancement Device. As the name implied, the device literally pushes your lower jaw forward freeing more space at the back of your throat allowing air to go throughout and into your lung.
75% to 80% of patients with obstructive sleep apnea have their airway restricted at the level of your tongue. There fore, for those who have simple mild or moderate obstructive sleep apne would benefit from the dental appliance.
However, it is important to have those devices made and adjusted by trained dentist to avoid long term TMJ and bite problem