True story: A woman bought a warmblood gelding and enjoyed a relatively low-maintenance first year of ownership, during which time she dutifully paid for routine veterinary, hoof, and dental care. She and her horse then moved to a neighboring state, and a short time later the horse began tossing his head vigorously in the left-lead canter. Puzzled and unable to eradicate the problem through training, she consulted her new veterinarian, who performed a thorough examination and announced his diagnosis: sharp-edged teeth—the result of insufficient or improper dental care—which were interfering with the action of the bit and causing pain.
"How could this be?" the owner insisted. After all, the horse had his teeth floated every six months, just as all the horse books and magazines recommend.
The veterinarian’s reply, "Not all equine dental practitioners are created equal."
I know the above story is true because it happened to me. Fortunately, my story has a happy ending: My horse’s teeth got a thorough and proper floating, the head-tossing ceased as if by magic, and my horse has since remained bitting-problem-free, thanks to biannual dental exams and routine floating. Other dentally neglected horses, however, might be less lucky, winding up malnourished, colicky, head-shy, impossible to ride on any sort of rein contact, or even chronic rearers as a result of teeth or mouth problems.