As hard as it is, I would try to get an evening job a couple of nights a week. There is also something called Care Credit that is a credit card specifically for dental work.
Also I would raise as much as I could through saving - setting up a per diem household budget and every penny saved would get set aside for the work. Then when I had some set aside, I would put the balance on a card, or try to find a dentist that will allow you to make payments.
Also I would see another dentist just to get a second opinion.