Chapter 7. Teeth

The teeth of the horse are divided into two main groups:

(1) Molars or grinding teeth.

(2) Incisors or biting teeth.

There are also the tushes or canine teeth, which are two in number on each jaw and would appear to be of no use in the horse.

Tushes are usually entirely absent in mares, and in geldings are cut at about four and a half years old. They occupy a position between the incisors and the molars.

Between the tushes and the molars is a space without teeth, and this part of the mouth is known as the bar and is the part where the bit rests.

There are twelve molars or grinders in each jaw, and these teeth perform the work of grinding the food and are of great importance to digestion. Anything wrong with these teeth impedes not only digestion but also affects the condition and disposition of the horse.

The method of determining the age of a horse is by an examination of the incisors.

Incisors

As in man the first teeth are milk teeth, and these give place to permanent teeth as a horse is reaching maturity. The permanent teeth are distinguishable from the milk teeth as they are larger and longer and give the gum the appearance of having receded.

At birth the foal has no teeth, although the central milk incisors are visible under the gum and are cut at about ten days old.

The next pair or lateral incisors are cut at four to six weeks old, and the third pair (the corner incisors) are cut at six to nine months.

FOUR-YEAR-OLD MOUTH SHOWING  THE RESPECTIVE SIZES OF MILK AND PERMANENT INCISORS.

At two and a half years old the central milk teeth are pushed out by the central permanent incisors, which come into wear at three years old. At four years old the lateral permanent incisors come into wear and at five years old the corner permanent incisors do the same.

At five years old the horse is said to have a full mouth.

Looking down into the incisor teeth of the lower jaw of a five-year-old horse, the enamel round the outside of the teeth is seen to be higher than the black centres of the teeth, giving them a hollow appearance. Wear on the teeth gradually reduces this cavity, and at six years old the cavity in the central permanent incisors has disappeared.

At seven years old the same has occurred in the lateral incisors, and at eight years old the corner incisors are also filled up. The horse is then said to be aged, and after eight years old the exact age of a horse is difficult to determine.

The incisors of the upper jaw fill up rather more slowly than those of the lower jaw.

At nine years old a well-marked groove appears close to the gum on the upper corner incisors and this groove, called Galvayne's groove, extends gradually downwards, reaching half-way down the tooth at about fifteen years and extending the whole length of the tooth at about twenty years.

After twenty years old Galvayne's groove gradually disappears and cannot be seen in a thirty-year-old horse.

Galvayne's groove is not infallible, but it is about the only indication of age apart from the length and shape of teeth.

The cavity in the teeth of a five-year-old horse is bean-shaped and black.

As a horse gets older the black centre gets rounder and smaller.

The teeth also become longer, more obliquely set in the jaw and rounder in shape with age.

Hard food from youth tends to hasten the maturity and wear of teeth, and any abnormality in the jaw will also affect the wear, as for example a horse with a parrot mouth.

Wolf Teeth

Are small rudimentary teeth which may occur just in front of the first molars on the upper jaw. They interfere with the bit and should be removed.

Molars

The upper jaw is wider than the lower. The upper molars grow downwards and outwards, the lower molars upwards and inwards. Hence the outer side of the upper molars and the inner side of the lower never get any wear, and the enamel on these sides grows to very sharp points which may lacerate the cheeks and tongue. A molar may also become split and decayed, which allows the opposite one to grow to a superfluous length and causes great pain.

THE MOUTH OF AN OLD HORSE, SHOWING THE LENGTH AND OBLIQUE SETTING OF THE TEETH.	A PARROT MOUTH, SHOWING AN OVERSHOT JAW, CAUSING UNEVEN WEAR.

Horse dentistry is now becoming a specialist's work. Many horse masters have a periodic examination made of their horses' teeth. Mr. W. Vahey is an expert who has stimulated the interest in horse dentistry in this country.

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