The adult dog has forty-two teeth, twenty in the superior, and twenty-two in the inferior jaw. They are divided into incisors, canine, and molars.

There are six incisors in each jaw at the front part. Of these teeth, the central are the smallest and weakest, and the corner ones the longest and strongest. The cutting edge of the incisor teeth presents three lobes. The middle one is large and prominent, and forms the top of the tooth; whilst the lateral lobes are cut out from the side, and the three taken together have a flew-de-lis shape, which becomes obliterated from wearing.

The canine teeth or tusks are four in number, two in each jaw. The upper tusks are stronger than the lower, and are separated from the corner incisors by a space which receives the lower tusks when the jaws are approximated. The tusks are pointed and adapted for holding and tearing purposes.

There are twelve molars in the upper jaw, six on each side. The first three are small and pointed, and are called the false molars; the next tooth has two cutting lobes, and the two others, or true molars, are flat on the crown for crushing.

There are fourteen molars in the lower jaw, seven on each side. The first four are called false, the fifth is flat posteriorly, and the last two are the true molars, with tuberculated crowns.

(1.) Cutting The Teeth

The first set, or milk teeth, appear through the gums shortly after birth, and are all cut within periods varying from three to eight weeks. Some pups cut their teeth much sooner than others. At about the fourth to the sixth month the first set is superseded by the permanent teeth, which, when drawn or worn down, are never replaced. In some exceptional cases, a dog may not have cut his permanent set at the ninth or tenth month. In fact, the process of dentition varies much according to the breed, temperament, and general health of the animal, and the kind of food on which he lives. Every thing being equal, the early appearance of the teeth may be accepted as evidence of the dog being endowed with good powers of growth and development.

Some dogs cut their teeth without any trouble; others, especially delicate or highly bred dogs, suffer more or less from the irritation caused by the passage of the tooth through the gum. This irritation, unless attended to, may lead to more serious disease in some other organ. The dog is feverish, and altogether out of sorts; refuses to eat, and evidently suffers from pain somewhere, and may have one or more fits. If, on examination, the gum at a certain part be found red, swollen, and tender, it will be necessary to cut down crosswise over the tooth for the purpose of facilitating the appearance of the tooth, and thus relieving the irritated gum.

A dose of Belladonna may also be given every three hours; and if there be, from some constitutional defect, a tardiness in shedding the teeth, a dose of Calcarea three times a-day will generally promote the process of dentition.

At a later period, the temporary teeth loosen, preparatory to their places being occupied by the permanent set. Such loose teeth should be drawn - a painless operation when properly performed - because, if allowed to remain, they either set up considerable irritation and pain, until they fall out of themselves, or they re-attach themselves to the gum close to the permanent tooth. In the latter case, there is not only irregularity of the teeth, but food lodges between the two teeth, and the result is, irritation followed by inflammation of the gum, and so much pain that the animal refuses to eat.

The tusks are particularly liable to become again attached to the gum, and, indeed, to the bone, and the difficulty of overcoming the irritation by extracting the offending tooth is obviously greatly increased. A little attention to these matters at first may obviate much future suffering. Still, it is not impossible, with proper tools and with proper management, to draw a temporary tooth fixed to the bony jaw; and the operation should always be performed whilst the animal is under the influence of chloroform.

(2.) Tartar On The Teeth

Deposits of tartar are often found on dogs' teeth. When a dog is not allowed to have exercise, and when he is fed on stimulating food, unnatural to canine tastes and requirements, the stomach gets out of order, and the teeth become more or less incrusted with tartar. Some diseases, and even mere age, induce the same condition of the teeth; although some dogs, even at an advanced age, have their teeth sound, white, and free from much deposit. About the second year of the dog's age, a yellowish-coloured deposit begins to appear on that part of the canine teeth which is close to the gum, - the deposit being thicker at the root, and thinner towards the apex of the teeth. This deposit on the enamel consists of phosphate and carbonate of lime, organic matter, and oxide of iron, which latter is the cause of the discoloration. On the removal of this deposit by means of a brush, the enamel is seen to be deprived of its characteristic smoothness and polish; it is slightly irregular on its surface, and one's finger-nail grates on it The gum in contact with the incrusted teeth is unusually red, swollen, spongy, and easily bleeds when slightly touched. As the dog becomes older, the deposit gradually forms on all the teeth, the incisors first, the molars afterwards.

In some cases, in old dogs, the tartar forms a very thick crust, greenish in colour, the seat of microscopic growths, and giving rise to a most disgusting foetor. The gums in contact with this decomposing and putrid sediment become irritated and ulcerated, and shrink from the teeth; the sides of the cheek, constantly fretted with the tartar, take on inflammation, followed by ulceration; saliva, secreted in great abundance, dribbles from the mouth; the dog refuses, and is even afraid to eat, and accordingly loses flesh; the breath stinks horribly; the teeth become loose and fall out, from inflammation and suppuration of the alveolar membrane. The dog evidently suffers much pain. The only way of treating such a case as this is, to remove the tartar, which is always most thickly deposited at the roots of the teeth, by means of scaling instruments similar to those used in human dentistry, or to brush the teeth with water acidulated with hydrochloric acid. To prevent re-deposition, the teeth should be daily cleaned with a soft brush, using soap and water as the best dentifrice. If this be not done, the tartar is sure to be deposited again, and the same scaling process will have to be resorted to. At the same time, the dog should have proper food and daily exercise; luxuries must be avoided. Any defect in the general health, such as disorder of the stomach, may be corrected by giving the suitable remedies.

(3.) Decayed Teeth

This is another common trouble amongst dogs, causing them much pain and annoyance, and making them a domestic nuisance from the breath being intolerably offensive. The same dog that has tartar on his teeth has generally one or more rotten, and perhaps broken down to the gum, and the same causes beget the two conditions.

The dog may suffer from paroxysms of toothache, as indicated by his demeanour; he eats little or nothing for several days together, and consequently gets thin and weak; he may attempt to chew food, but the morsel is speedily dropped out, and on examining the mouth the teeth are found decayed. When the tooth has broken down to a mere stump, that stump acts as a foreign body and sets up irritation in the gums; inflammation of the gum and then of the bone follows, and the upshot is, that "canker" of the mouth is established. The stumps are best detected by feeling for them with a probe.

Of course, the only treatment is extraction of the stamps, and of all teeth that are decaying or decayed.

(4.) Management Of The Teeth

As a rule, the teeth retain their whiteness and polish up to about the second year; they then become slightly crusted with tartar, even when they have been properly looked after, and when the dog has had good health. At the same time, the front teeth lose their "fleur-de-lis" shape and become rounded off. The degree of wear and tear greatly depends on the kind of food which the dog is accustomed to eat; if fed on bones or other hard meat, the teeth sooner exhibit marks of wear, whereas, when fed on soft meat, the teeth preserve for a longer period their serrated sharp edge. The appearance of the teeth at different periods of life is a fallacious test of the dog's age, or, at least, subject to so many exceptions as to be of little practical utility, and of no scientific value.

Nothing wears down the teeth so much as grasping hard or heavy substances with the teeth, or permitting the dog to grind bones. For the sake of the teeth, dogs should not be taught to run after and carry back stones, sticks, etc. Such tricks may be amusing, but the dog is sooner or later the sufferer. Bones may be allowed to dogs - not to crunch and swallow - but to pick and polish.

Another cause of bad teeth is disorder of the stomach induced by improper food. This is a matter that can be put right. The simpler the food, the better for the dog. Of course, teeth become worn and decayed as a result of the general decay which attends old age, although healthy dogs properly cared for have often sound teeth at a very advanced age. Petted dogs are the earliest and the greatest sufferers from diseases of the teeth.

The abuse of mercury, pushed to salivation, is alone more destructive to the dog's teeth than all other causes put together; and it unfortunately happens that this animal is peculiarly susceptible to the action of that poison.