E Q U I N E D E N T I S T RY — A N I N T R O D U C T I O N
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deciduous precursor and erupt at one year for the 1st molar (09 triadan system) 2yrs for the second molar (10
triadan system) and 3 and half years for the third molar (11 triadan system). Adult premolars erupt at two and
a half years for the second premolar (06 triadan system), three years for the third premolar (07 triadan system)
and four years for the fourth premolar (08 triadan system)
The surface of the last three cheek teeth curve upward in the caudal direction this is referred to as the Curve of
Spee This curvature is most marked in Arab-type breeds, which often have a similar curvature on their (dished)
nasal and frontal bones. It is important that during oral examination, this normal feature is not mistaken as an
overgrowth of 311 and 411 (last lower cheek teeth).
Rule of Thumb
By examining the incisor teeth it is possible to determine if all the adult incisors are present and in wear, if so
the horse is probably at least five years of age. Now by assessing the lateral or corner incisor we can establish
some benchmarks. If the lateral incisor when viewed from the side of the horse is wider than it is long ( i.e less
then square) the horse is probably less then ten years. If the lateral incisor is approxiamately square the horse
is around ten and if the tooth is longer then it is wide then the horses is older than ten. This feature will continue
to increase for many years, hence the term long in the tooth.
Occlusal Surface
The occlusal surface of the incisors is oval in appearance in younger horses and triangular in older horses. The
infundibulae or “cups” in the incisors are gradually worn away. The times that this occurs are quite variable and
should not be used as the sole indicator of age. Cups disappear first from the lower central incisors at between
6-8yrs then the lower middle incisors between 7-9yrs then the lower lateral incisors between 8-10yrs. The cups
are lost from the upper central incisors between 9-11yrs the upper middle incisors between 10-12yrs and the
upper lateral incisors between 11-13yrs.
Age indicators
When ageing a horse do not forget the basics such as brands. Thoroughbred brands will provide a single digit
indicating the year, i.e you will not know if the horse was a 87, 97 or 07 foal, but from external exam, history
and dental ageing you should then be able to accurately age the horse. Standardbreds are branded with their
year of birth as well as an individual ID number. To read these brands is simple but requires a key.
Indicators of age include the length and wear patterns to incisors, the angle of incisors, the cupping of cheek
teeth and Galvayne’s groove. As horses age their incisor angles change. The occlusal surface is displaced more
labially. As the cheek teeth age they lose enamel and their appearance alters to a hollow “cup” with brittle edges.
The upper ‘9s or 4th cheek teeth are usually the first to show this and it usually occurs in the late teens to mid
twenties.
Galvayne’s groove is a groove that some horses have in the lateral incisor. It appears at the gumline of the upper
incisor at about 10yrs, by 15yrs it extend about halfway down the tooth and by 20yrs it reaches the occlusal
surface. By 25yrs it begins halfway down the tooth and extends to the occlusal surface and by thirty it is no
longer present.