C.J.Equine Dentistry
Evolution and domestication
The horse's oldest found ancestor lived about 55 million years ago and was only about 10-20 inches tall (the size of a small dog). It originally dwelled in the forest where it lived off of fruits, plants and leaves. It had low-crowned brachydont teeth (like humans), which were designed to deal with the soft composition of its diet. The horse has dramatically evolved from its ancestor over this time, due to changes in the climate which resulted in the formation of large grassland plains. The horse had to evolve into the grazing animal we see today; which feeds on coarse, abrasive grasses. The changes in the diet, consequently caused changes to the teeth, as the equine teeth now have to breakdown these high cellulose grasses efficiently in order for its digestive system to be able to utilise the energy correctly. The teeth therefore evolved from being brachydont to hypsodont. The hypsodont tooth erupts continuously throughout the horse's life, at a rate of about 2-3mm a year, which should be the same as the rate at which the teeth get worn down by the silica in its natural diet. This allows the teeth to remain efficient at grinding down the high cellulose diet, which in turn helps to release the energy from the grass or hay which the horse needs.

The horse has also evolved to have a specific mastication (or eating) cycle which helps with this particular diet. It eats in a circular motion, with only one side of its mouth being in contact at one time. The horse is also evolved to eat for approximately 18 hours a day. In a horse that is living in its natural environment and had a perfect mouth, all the teeth would gain even wear during this mastication cycle, maintaining a balanced oral cavity. However, due to the domestication of the horse, humans have imposed certain restrictions on the horse which have had a direct impact on the equine oral cavity. Horses also evolved to graze with their heads down at ground level eating grasses for many hours a day. By altering their living and feeding conditions we also alter the way their teeth wear: by forcing them to eat with their head up; providing short feeding times; feeding grains, chaffs and pelleted feeds. When we do this we must be aware of the effects these changes have on the horses' dentition.

Horses have been selectively bred over the years by humans for certain traits such as movement or temperament. When looking at a horse's conformation for selective breeding, the teeth were not taken into consideration. Therefore we have actually been breeding horses with more dental problems than if they lived naturally in the wild. When combined with a change to their diet and environment due to domestication, this has led to the development of the equine dental industry. A diet high in concentrates has been shown by scientific research not to promote complete side to side movement of the horse's mastication cycle, allowing the development of sharp points to develop on the outside edge of the upper cheek teeth and inside edge of the lower cheek teeth.