Oral appliances are usually covered under medical plans, not dental plans. Most benefit plans will cover treatment of moderate-severe sleep apnea with an oral appliance. Each plan is individual in their coverage amount, and a pre-approval can be done for you to check exactly what your coverage would be before committing to the therapy. Most plans will no longer cover treatment for mild sleep apnea, although there are exceptions for people who are replacing an oral appliance that was previously approved by their insurance.