The majority of dental equipment these days have a plug with a tag or stamp that says "must be used with hospital grade receptacle." Many panoramic x-rays, a bunch of the chair brands, and almost every sterilizer and autoclave will say this on the tag. Sometimes the equipment manual will even state that the warranty is voided if not used with a hospital grade plug.
Hardly any dental offices that have med gas fall under 517.61(C)(2) as it opens up a whole other can of worms for the dentists from a legal, paperwork and licensing perspective. Around here, the dentist has to write out an affidavit stating that the med gas is to be used for sedation purposes only, and not for general anesthesia, before plans review will even accept a set of drawings for a dental office.