If fables are meant to be explaining how we think about the world then they should not directly contradict reality as we experience it. I understand that you're trying to paint a picture here but there is very little upside to the dentist profession in the picture you paint but plenty of upside for capital providers. As such it is a counter-example. A good example would show a win-win for the dentists and for the capital providers (and preferably the start-up founders too).
Many business models these days are 'x' on the web, where 'x' really does not improve by being on the web and practice management is a prime example of that. If you don't believe that try to explain to a dentist why they need redundant internet access to keep their practice running in case they have internet problems when right now they can do so just fine without any access at all.
Web apps have lots of upside but they also come with a set of requirements that is not always practical or even desired.
On top of that you discount domain knowledge which I think is a very important part of any successful business in an area like the one you describe.
Isn't part of what happens is that the expectations of customers change, so these providers (in this case, dentists) have to make these changes? It's not necessarily about providing a better experience for the provider (though it does do that in many cases), but a better, or 'expected' experience for the customer?
If customers expect to be able to book online (and as a user of services like ZocDoc, FreshDirect, Instacart, and Homejoy I do expect these things now), then providers who do (theoretically) provide these things will have an advantage of those who don't.
Not going to argue for or against the 'upside' part, as I do think that is debatable, at least in the short-term. A big part of this is avoiding 'downside' by not adapting, IMO.
The whole point is that expectations do change but so slowly that there is 0 incentive for a dentist to switch their practice over from what they know and what works well to your shiny new software which works with mobiles, tablets and so on.
You do have a market: new dentists. But old ones are just happily going to roll along with their gear until either they or the gear dies of old age. And then they or their heirs will sell the practice to a new dentist, who will have to wonder about re-keying all the old data into your shiny new software or to focus on what he's best at: dentistry.
