I recently went to a dentist to investigate the potential for an oral appliance.  I had researched appliances, and had seen that some let you close your mouth all the way and others do not.  I am interested in one that does permit full closure, because before my apnea was diagnosed and I was placed on CPAP, I was apparently breathing through my mouth at night, causing extreme dry mouth in the morning.  The dentist said that the device he uses and has had success with, Snore Guard, does not permit full closure.  I am concerned that the dentist limits himself to one brand.  It may be because he finds that one brand words best, and it may be because he has a deal with the manufacturer.  Is my concern reasonable?

Yes, your concern is very reasonable.  These things do cost a lot of money.  If I were you, I would ask him why he only offers one type.  My dentist has 2 types - the TAP and Somnodent.  I checked the Snore Guard website - this is NOT  a mandibular advancement device and is mainly used to treat snoring rather than sleep apnea.  I would check out the American Academy of Dental Sleep Medicine website for dentists in your area that sell these appliances.  You can call around and see which appliances they offer and their cost.  I have tried both TAP and Somnodent so far.  You can close your more with the Somnodent but I couldn't do so with the TAP 1 but there are newer TAP versions that I have yet to try.