2938 Vet. Med. Basic Sciences Bldg.
2001 S. Lincoln Ave.
Urbana, Illinois 61802
By Sarah Probst
University of Illinois
College of Veterinary Medicine
"One of the first objectives in a pre-purchase exam is determining the age of the horse. If the horse is supposed to be seven and the teeth say the horse is eleven, often buyers quit right there," says Dr. Jon Foreman, a veterinarian in equine medicine and surgery at the University of Illinois College of Veterinary Medicine Teaching Hospital. The economic value of a horse is directly related to its age. Seventy-five years ago, aging teeth was a common skill among horse owners. Today most horse owners rely on veterinarians to age a horse.
"It is possible to put a range on the age of the horse by looking at the incisors of the lower jaw," says Dr. Gerald Pijanowski, veterinarian and anatomy professor at the college. "We use two criteria to get a handle on the age of the horse: eruption dates and wear. We can rely on wear because as the tooth erupts it is worn down; the characteristics we see on the chewing surface of the tooth are going to change."
The first step is deciding whether the teeth are deciduous or permanent. Horses lose "baby teeth" just like humans do, and these deciduous teeth are replaced by permanent teeth. "Permanent teeth have a smooth tapering shape from crown to root while deciduous teeth have necks, a definite restriction between the crown and the root. Looking at the rest of the horse can give you a hint as to whether you should expect deciduous or permanent teeth. If the horse is 18 hands, 1500 lbs, and graying, it is probably a permanent tooth," explains Dr. Pijanowski.
After a tooth erupts, it takes 6 months to reach a state
of full use by the opposing teeth for grinding and chewing. The
term "in wear" means that the tooth has reached this
state of full use. When horses are able to use a tooth, they grind
enamel-the hardest substance in the body-off the chewing surface.
In the process, dentin is exposed. At this point, the tooth is
level. Level teeth appear with a complete ring of enamel around
the tooth and darker yellow dentin exposed in the center.