It requires electricity. Oral appliances resemble an athletic guard, but have more sophisticated features that enable them to dilate your airway by supporting the lower jaw in a slightly forward position. I separate appliances into two broad types. It allows you to breathe naturally either through your nose or mouth. There are now at least two oral appliances that connect to a CPAP when a nasal mask can't be tolerated, but the additional breathing assist is indicated.
Oral appliances enjoy a much higher acceptance, but they also have limitations.
There are trade-offs, but a detailed description is more useful when applied to a specific situation and need. First generation oral appliances had limited success in treating OSA and earned a poor reputation in sleep disorder medicine. They were one-piece, held the jaws rigidly and were not adjustable. Technology, research and creative design have produced some two-piece adjustable appliances with high success rates. They allow a slight lateral jaw movement while holding the mandible in the prescribed forward and vertical position.