They aren't employers of the NHS. They are either self-employed, a partnership or a limited company. So they get paid according to the formula of treatments and patients on the books (the thing they are currently arguing about). Some bright spark has worked out that the average gross income from an NHS Trust to a dentist is �80k per year, and from that all expenses of the practice have to be paid by the dentist. That not only includes the assistants, but the buildings and equipment costs.