Level of care provided was what I was trying to get at in my first reply in this thread. Most typical dental care areas probably would not need any emergency power other than maybe egress lighting just like any other public access building, if the patient is unconscious during the procedure that is likely to change, but those types of procedures are usually done in specialty clinics and not your typical general dental care clinics.
The first paragraph is not real clear, the facility management can desire to have standby power for particular areas, and I guess they can become part of the essential system, but they are not legally required outlets of the essential system as determined by other codes or AHJ's.
I agree with the rest mentioned here.