Why do horses have teeth that grow throughout their lives?
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The horse's teeth grow continuously because they are called hypsodont: the dental crown, very high, remains in reserve in the jaw and gradually rises to compensate for the constant wear caused by the grazing of abrasive fodder rich in fiber and silica.
A dental reserve for a tiring herbivorous diet
In the wild as well as domestically, the horse spends a large part of its day chewing herbs, hay or straw, foods loaded with silica phytoliths which act as a natural abrasive. Each chewing movement wears down the tooth surface by approximately 2 to 3 mm per year. Without compensation, the teeth would be reduced to nothing within a few years. The coronary reserve, buried under the gums in young horses, becomes exhausted with age: it eventually dries up, generally around 25-30 years of age, which explains why very old horses lose their chewing capacity.
This continuous growth is, however, not always perfectly regular: uneven chewing angles or a misaligned jaw can create overteeth, sharp points on the edges of the molars. They injure the cheeks or tongue and interfere with food intake. This is why a regular veterinary dental check-up, with filing ("floating") if necessary, is recommended for all adult horses.
Reading the age on the teeth
The progressive and predictable wear of the incisor teeth, as well as the appearance or disappearance of certain marks (such as the famous "dental star" or Galvayne's cup), allow veterinarians to estimate the age of a horse with correct precision in young animals, which are more approximate after 10-12 years. This is the origin of the expression "on a given horse, you don't look at the teeth": examining the mouth of a horse received as a gift amounted to discreetly checking its real age, a politeness considered inappropriate towards the donor.
