OTOH, if the "unnecessary" there just means "not satisfying the platonically correct cost/benefit analysis", and there's still some net benefit to the patient, and the government program didn't ask the dentists to use such CBA, then I wouldn't consider that abusive.
(I can imagine Frontline being equally outraged at dentists denying government-subsidized dental care on grounds of failing the platonic CBA too...)
A society cannot be run on expecting people to resist the powerful incentives set up for them.
You can see this effect in every aspect of government operations.
I haven't seen this episode and so don't know what qualifies as "major dental work." However, as someone who has had government dental insurance, I wanted to chime in with a possibly irrelevant anecdote.
This dental insurance covered few things, one of which was having teeth pulled. When I was having major pain and other issues with a molar, the only covered treatment was to have the tooth pulled. Anything else would have to be paid 100% out of my own pocket. So the only viable option for most people in my situation would have been to have the tooth pulled, which certainly seems like "unnecessary major dental work on poor people", through no fault of the dentist.
Frontline Dollars and Dentists season 2012 episode 13
and see for yourself.