^ But no regulations or standards in training or licensing. That, coupled with the whole "against the law" aspect, is enough to make me shy away from any equine dentist.
Before I knew better, I used a self-taught, highly-recommended equine dentist. He did an OK job, but also missed a lot. And also very nearly killed a pony at the same boarding barn through faulty administration of sedation. Some other boarders used a different, "natural" dentist. He "sedated" the horses by--wait for it--chewing herbs and mints and blowing the fragrance in the horses' nostrils. He was also terrible at floating teeth.
Mark has a point that a lot of vets really aren't all that qualified to float, either, so look for one that is! The use of hydraulic equipment is generally a good sign. I'm fortunate enough to have a local veterinarian who has made dental work his specialty and only practice.