I cannot overstress the importance of proper dental care for horses. They should be examined and treated by a qualified equine DENTIST at least annually. By "qualified" I mean a dentist certified by the International Association of Equine Dentistry.
Now here's where I disagree with AAEP and AVMA, the two major equine veterinarian associations. I do not believe that a veterinarian is necessarily qualified to be mucking about in your horse's mouth. If he/she is certified by IAED, okay, but otherwise do we go to our family doctor for our dentistry? Of course not! We have had several horses come in that had received routine dental care from vets with teeth in atrocious condition. Dentistry was widely ignored in veterinary colleges until recently, when the horse owning public became more educated and the demand increased. The laws differ state to state regarding who can legally perform dental work. We are fortunate in Virginia in that they recognize IAED certified dentists. Even so I believe the law is imperfect, requiring certain procedures to be overseen by a veterinarian. That can be like an apprentice electrician supervising a master electrician. Some vets are going to the trouble to become certified by IAED, and I salute them.
We are also fortunate here at Idylwood to have the services of a Certified Master Equine Dentist. He has done wonders for us with elderly horses suffering from years of incorrect or nonexistent dental care.