Every knowledgeable horse owner should be able to tell, with a glance at the horse's teeth, whether he or she is dealing with a young or an old horse. Narrowing a horse's age down to a year or two is more difficult, but with practice, it can be a useful skill when it comes to buying an unregistered horse.

Three substances enter into the composition of all teeth, the dentine, enamel and cement. The dentine is the yellow-white, bone-like material which makes up the grater part of the tooth and surrounds the pulp cavity. The enamel is the shiny white layer which extends over the exposed portion of tooth and which is seated upon the underlying dentine The cement is simply connective tissue converted into bone, and it is spread over parts of the exterior of the tooth.

Two sets of teeth are grown by the horse, the temporary or milk teeth, and the permanent teeth. An adult male horse has 12 molars, 6 incisors, 2 canines and occasionally one or two wolf teeth on each jaw. In the temporary teeth there are 6 incisors and only 6 molars (the first three on each side) on each jaw of the young horse. The incisors, the front three pair of teeth, are called the centrals, laterals, and corners. The canine teeth or tushes are placed a little further back in the space between the incisors and the check teeth or molars. They are usually present only in the male but small ones are common in the female. The canine teeth appear at 3 1/2 to 4 years of age and are fully developed at 4 1/2 to 5 years. They are absent in the 2 year old.

The teeth of the horse become worn on the top from the grinding action during chewing, and as the horse ages the neck of the tooth is pushed up out of the jaw bone. This goes on throughout the horse's life and at successive periods in the horse's existence, the crown, then the neck and lastly the fang of the tooth are in wear. In the aged horse the incisors appear to be very long due to the increase in length of their visible portion. But the actual length of the tooth has decreased, because much has been worn off the top portion and less of the tooth is imbedded in the jaw bone. The actual length of the horse's teeth do not increase after the horse is five years old.

Although the changes in horses' teeth vary somewhat with the health, breed and environment of the animal, the examination of the teeth still remains a fairly reliable method to determine the age.

•At birth the foal may have the two central incisors, but these may not appear until the 10th day. Three check teeth on each side are present.

•At 4 to 6 weeks the lateral incisors appear.

•At 6 to 9 months the corner incisors appear.

•At 1 year all 6 temporary incisors are present and 4 cheek teeth (3 premolars and the first permanent molar) on each side.

•At 2 years of age the cup-like cavities in the top of the incisors have disappeared and the surface becomes flat. The 2 year old now has five molars.

•At 2 1/2 years the central incisors are lost and the first permanent incisors grow through the gums.

•At 3 1/2 years the lateral temporary teeth are being replaced by the permanent laterals.

•At 4 1/2 hears the corner permanent incisors are cut, and these are well up and are level when the horse is 5 years old.

•At 6 years the corner incisors show some signs of wear. The depressions of the central incisors are much more shallow than those of the lateral, or corner incisors. At his age, a new feature presents itself on the tabular surface of the central incisors in the form of a blackish or brownish line which runs transversely between the disappering cavities and the front edge of the tooth . This is the first appearance of what is known as the edge of the tooth. This is the first appearance of what is known as the dental star, and it indicates that so much of the tooth has been worn away that the upper part of the pulp cavity filled with dentine can been seen.

•At 7 years the dental star is much better marked in the centrals, at 8 there should be no difficulty in seeing it. At age 7 a useful guide is furnished by the top corner incisor tooth, which does not wear evenly, as a result a hook develops at its rear edge. This hook and accompanying notch appears at 7 years; has worn away a little at 8 years: and has disappeared and the tooth has a level surface at 8 1/2 to 9 years. At 11 years the hook reappears and the notch becomes deeper, so that by the time the horse reaches 13 years of age it is very noticeable and usually persists for the rest of his life.

•From 8 years onwards it becomes more difficult to estimate the horse's age closely, but the experienced examiner can be close. At 8 years the cavity has disappeared from all incisors and the dental star is clearly apparent in the central incisors. At 9 years it appears in the laterals, and at 10 to 12 it is present all incisors. The shape of the surface of the horse's teeth varies from oval to triangular and then to round as the horse becomes older. In horses up to 7 years they are oval. From 9 to 13 years they are triangular, and after 13 years rounded with the dental star in the middle. As the horse ages, a well-marked longitudinal grove appears, first as a notch at the outer side of each upper corner tooth just below the gum, then it travels down; the tooth in a narrow longitudinal furrow. It is the so-called Galvayn's Grove named after a horse expert who first drew attention to it. This grove makes its appearance at 10 years, but quite often its faint beginning can be seen on close inspection at 9 years. When it reaches halfway down the tooth the horse is regarded as a 15 year-old, and when it has reached the bottom a 20 year-old. For those horses that really reach a ripe old age, at 25 years the grove has disappeared from the upper half of the tooth, and at 30 years it has disappeared completely.

A bit of practice while using this and information from other sources, will help you to determine the horse's age. Examine your own horse's teeth carefully, then have some fun by going to a friends stable and make an educated guess at the horses' ages. The owner can then tell you how close you have come to the right answer. One needs more than luck to keep from being duped by dishonest horse dealers, being familiar with the changes that take place in the horse's teeth is just one aid in helping you make a good decision while horse buying.