Can a dental appliance help sleep apnea?

Absolutely! According to 2006 american academy of sleep medicine practice parameters, oral appliances are indicated for use in patients with mild or moderate obstructive sleep apnea who prefer them over CPAP and should be completed by a dentist with advanced training in sleep medicine.
Yes. The recommendation from the american academy of sleep medicine for mild or moderate sleep apnea is CPAP or an oral appliance. For severe sleep apnea the recommendation is try CPAP first and only use an oral appliance if you can nit tolerate the cpap. The dentist must be experienced in treating osa.
Sleep apnea. A CPAP is the treatment of choice for sleep apnea. However, many people either don't like that apparatus, can't wear it or won't wear it. It is also difficult to travel with. An oral appliance fitted by a trained dentist can keep the airway open to eliminate sleep apnea. The appliance worn inside the mouth positions the lower jaw slightly forward thus keeping the airway open. It also stops snoring.