Why send them directly?
Why not hook up with someone running a call center, get them to pre-screen the calls, qualify them and then sell the leads to more than one professional, after all it makes sense to get more than one quotation for work you want doing, right?
The call center (with your permission) can also do some upselling and you could do a revenue share on any sales, teeth whitening (for dentist leads) etc.
Just a thought