Why dental care is so important for horses
The horses mouth is a dynamic phenomenon in which the mandible moves up and down as well as from side to side, so these two movements combine as a rotating grinding motion. In addition, horse teeth are forever erupting and wearing, resulting in wear patterns and geometrical changes which cause riding and nutritional problems.
Video (courtesy of doctorhorse.it): The movements of the lower jaw when chewing.
So the horse's teeth are extremely important to the horse's health. Balance is critical to the performing horse, correct equilibration of the mouth can assist the overall balance of the horse. Bits and all mechanical devices should be fitted to the head with considered thought for basic anatomy and comfort to the horse.
Video: Equine Dentist Leith Ryan at work.