When you figure out how to outsource going to the dentist, let us all know. That's one of those services that pg talks about that everybody needs but nobody wants to provide: great startup opportunity.
If you're just talking about, "we come to you", that doesn't seem like a real compelling service. Dentist visits are rare and important, so I'm willing to invest a little more, and it seems like dentistry in the back of a truck would be limited. Much of the equipment at a dentist's office can't exactly be thrown into a truck.
There would definitely have to be some great marketing for this to not seem shady.
A van wouldn't cut it - you would need a bus.
Can a hygienist practice independently?
I assume it shows up once or twice a month.