Judging Horse Age from Teeth

Galvayne relied on two other dental features to determine the age of mature horses. One is a hook that is supposed to appear on the outer edge of each upper corner incisor at seven, disappear at age eight and return age 11. The second is the yellow-brown groove called Galvayne's groove, said to appear at the gum line of the upper corner incisor at age 10 and lengthen as the horse ages, spanning the entire tooth by age 20, then leaving the gum line and advancing toward the bottom of the tooth until it wears out by age 30. A 1996 Belgian research study found that hooks apparent in only two of the 15 seven-year-old horses, and in both cases they appeared one side of the mouth only. As for the famous groove, Belgian researchers found no consistency in the size, length or even existence of? the trait in horses of the specified ages.

Common dental terms
arcade -- a row of teeth on one side of a horse's jaw.
bars -- the toothless spaces between the incisors and the cheek teeth. canine-the nonchewing teeth seen in males (and sometimes females) at the front of the bars area.
cement -- the comparatively soft material that (1) covers the outside of a tooth, (2) connects the tooth to the jawbone beneath the gum's surface and (3) fills the inside of the incisor cups.
cheek teeth -- taken together, the 12 premolars and 12 molars that are responsible for masticating food in a circular, grinding motion.
crown -- the part of the tooth that emerges above the gums.
cup (infundibulum) -- the dark-brown to black cement-lined "crater" in the biting surface of each permanent incisor tooth that is worn away by the time the horse is eight years old, leaving a flat mark called an enamel spot.
dental star -- the brownish dentin, exposed by wear, that appears between the enamel spot and the front of each permanent incisor, starting with the central incisors about age eight. Initially a straight line across the tooth, the dental star curves with age, and eventually becomes round and dark brown on all incisors.
dentin -- the bonelike material that makes up the greater part of the tooth below the surface layer of enamel. enamel-the calcium-rich substance that forms a thin layer over the incisor teeth and is complexly folded into the horse's molar teeth; the hardest tissue of the body.
enamel spot -- the white enamel tooth cup that is left visible when cement has worn away.
hypsodont -- teeth that have long crowns and short roots, in contrast to the crowned "brachyodont" teeth typical of other grazers, such as cows and? deer
hook -- a sharp projection on the surface of a tooth, often caused by uneven wear.
incisors -- front teeth used for cutting rather than grinding, Numbering six on the top and six on the bottom in adult horses, these are further distinguished in the central (first), intermediate (second) and corner (third) upper and lower incisors.
malocclusion -- abnormality in alignment of upper and lower teeth
milk teeth -- deciduous, or baby teeth; young horses have 24.
molars -- the 12 nondeciduous cheek teeth, three at the back of each arcade.
occlusal surface -- the biting surface of the tooth.
permanent teeth -- the long, large teeth that replace the original milk teeth by the time the horse is five years old
premolars -- the first three cheek teeth in each arcade, located directly behind the bars. They are replaced by permanent premolars between age 21/2 and four
profile -- the slant of the incisors. Profile angle changes from fairly upright in young horses to extremely slanted in old horses
pulp -- the living tissue at the heart of a tooth, including the nerves and the blood? vessels. As the pulp recedes over the years, it leaves behind stained dentin, which steadily emerges as the dental star.

EQUUS thanks Jack Easley, DVM, for his help in the preparation of this article. Easley, a 1976 graduate of theTuskegee University School of Veterinary Medicine, with postgraduate work at Oklahoma State University and Kansas State University, specializes in equine reproduction, surgery and dentistry at his practice in central Kentucky. He has published and lectured on equine dentistry and oral disease for more than 20 years, and presented equine dental short courses to both veterinarians and lay groups in the United States, Canada, Europe and Australia.

This article first appeared in the September 1998 issue of EQUUS magazine.