A flexible mask substrate (MS) with a rigid front plate (FP) which may be a viewing window (VW) causing the mask substrate to extend forward from a patient's face, forming a chamber in front of the patient's mouth. Instrument ports (IP) allow instruments to be introduced through the mask into the patient's oral or nasal cavity to perform dental or medical procedures. An elastic band (CE) on the mask substrate to conform the mask to contours of the patient's face. A malleable metal strip (MM) for conforming the mask to the patient's nose. Methods of fabricating the mask. The mask, and variations thereof, may be used to perform various treatments, including non-oral procedures. Using a nebulizer in conjunction with the mask, wherein the nebulizer is supported independently of the mask.