The following mask The Oracle was cleared for sale in the USA by the FDA.

This mask fits into your mouth, and has you plug your nose with nose plugs. That's the mouthpiece up there in the picture. The mask is is supplied with the nasal plugs - and they are mandatory, not optional for the first 2 weeks.
http://www.fphcare.co.nz/osa/pdf/HC452/185043485.pdf
1) Attach Headgear by re-connecting one of the clips (J).
2) Pull the SnapFlapTM Cover (A) back to the retracted position.
3) Insert the SoftSeal (B) into the mouth, one side at a time. It should sit in the gum region between the cheeks and the teeth. Move your lips around so they fit comfortably all the way over the
SoftSeal.
4) Return the SnapFlapTMCover (A) back to its normal position, and adjust the mask tightness by rotating the Dial (C) as shown.
5) With Headgear (I) sitting loosely around base of neck, re-connect clip.
6) Adjust Headgear with VelcroTM tab (l1) to remove slack.
7) Use Nasal Plugs (H) for first two weeks of use. Refer to Nasal Plug Instructions.
Look at that mouthpiece and headgear. Look at the instructions for putting the mask in your mouth, and tying it around you neck. Imagine adding nasal plugs, and ask yourself which is easier for a concious, otherwise healthy person to deal with: that, or a piece of tape with pull off flaps.Nasal Plugs
Nasal Plugs are used to aid in the training of natural mouth breathing. It is optional to discontinue use after the first two weeks. However, use Nasal Plugs if you experience any of the following:
Oral dryness Nasal leak Poor sleep Quality
Instructions for Use
1) Your Nasal Plugs (H) come in three sizes, S / M / L, as indicated on the joining strip.
2) Pull medium sized silicone Nasal Plugs from the central joining strip and insert into nose so that
the base of the plugs are just inside the nostrils.
3) The plug should fit comfortably inside the nose and should seal off the flow of air.
If not content, try the other sizes.
4) Use the OracleTM Oral Mask as you normally would, with the Nasal Plugs inserted.
Thanks for caring enough to warn us. We care enough to let you know that you may want to re-think that warning.
Hang around!
O.