Dental malpractice insurance is way, way less expensive than medical malpractice insurance.
As Daurang has eluded to, with the coverage that many dentists choose, 1,000,000/3,000,000 and a few years experience under your belt, your premiums tend to end up in the 1,200 to 1,500 a year range. Slightly more if your a specialist(especially oral surgeons with their sedation usage). A couple of the larger dental malpractice insuarnce companies are The Medical Protective Company (a subsidiary of GE financial) and Fortress Insurance Company.