The dog, like all other animals that give suck to their offspring, has two sets of teeth, the first or milk or deciduous teeth, and the second or permanent teeth, says a writer in Field and Fancy. The first set of teeth are shed about three and a-half to five or six .months in the larger breed of dogs, and from five to seven months in the smaller or Toy breeds. Frequently Toy dogs have a good deal of trouble in shedding their teeth, and some, such as the canines or tushes, are often never shed at all, thus leaving the dog with two sets of tushes, the first being placed behind the second.

The number of teeth varies according to the class of dog. The typical number of permanent teeth is forty-two. As a rule, if there should be any variation, they are excess in those dogs having long jaws, and are fewer in the short-faced dogs, such as Bulldogs, Pugs, Griffons, Toy Spaniels, etc. In the longer-faced dogs there may be as many as forty-four, while the short-faced dogs may have as few as twenty-eight, and rarely more than thirty-eight. In the hairless dogs they are usually even fewer still.

When the young puppy cuts his first teeth it does not cause any trouble, but it is the opposite when it sheds the first and cuts the second teeth. It is a critical time with him, and predisposes him to take various diseases, such as fits, skin diseases, distemper, etc. In case the first teeth are not shed, so as to prevent the shooting up of the second teeth, it may be necessary to extract them. When the temporary tushes are not shed and the second or permanent ones are up in front of them, the former should be extracted carefully, so that they are not broken and the roots in consequence left in the jaw.

Between the ages of four and seven months Toy dogs should have their mouths frequently examined in order to discover if the second teeth are coming up properly and the temporary ones being shed in due order. If this is not watched an ugly mouth may result. To assist the falling of the first teeth and the regulation of the new or second teeth, young puppies should have large, uneven, raw bones given them to gnaw and tear at.

The earliest disease of the teeth is erosion of the enamel, which causes the teeth to have a worm-eaten or cankered appearance. It is usually considered as a guide that the dog has had distemper either just before or at the time or after the second teeth have appeared. Although it may be taken that the dog has had distemper if this appearance of the teeth is present, it cannot be said that the dog will not have another or future attack of this disease, as cases are encountered with this appearance in second attacks of distemper. When the enamel of the teeth is eaten into, no treatment is of any use to restore the teeth to their proper appearance.

The commonest disease of the teeth is a collection of tartar just around the neck of the tooth just above the gum, and which may after some time insinuate itself between the gum and most of the tooth, and set up inflammation of the tooth socket, and in consequence loosen the tooth. Frequently the material encases the whole of the tooth, which looks blackish, greenish, yellowish or brownish in color, often giving off a repulsive odor when the animal is suffering from some ailment. It is due to microbes settling on the teeth and manufacturing a calcereous material out of the saliva and debris of food collecting on the teeth. It originates in consequence of the animal being deprived of tearing food, such as lumps of raw meat on a bone. Dry bones or hard biscuits do not supply the absence of this tearing food. The dog's teeth by nature are intended for biting and tearing much more than crushing. Nearly all pet dogs living In towns as they approach old age suffer from this collection of tartar, whereas those dogs who live in the country and are used for sporting purposes, shepherding, watching, etc., are almost, if not always, free from it. Again, if the dog does not use his teeth for chewing, the salivary glands in the mouth are limited or put out of action and in consequence proper digestion does not take place, the chemistry of the mouth is upset, the secretions form a suitable pabulum for microbes to act upon and manufacture tartar.

Therefore, from what has been said above, if one wishes to prevent the formation of tartar, one must feed a dog on tearing food that gives the mouth and teeth work to do. If this precaution be neglected and tartar should form, it ought to be removed by scraping off and brushing the teeth with some suitable wash, or powder, or soap, daily after food. When the mouth gives off a bad odor, five to ten drops of dilute hydrochloric acid should be given with the food daily as it assists digestion and rectifies the faulty secretions.

The most serious diseases of the dog's teeth is inflammation of the covering of the fang of the tooth, together with that of the tooth-socket or alveoius, which brings about receding of the gum and loosening of the tooth, the root of which is bathed in pus, particles of food, and saliva. The gums are spongy, bleed on the least touch, and the mouth gives off a repulsive odor. It may or may not be associated with tartar. It frequently arises after distemper, typhus, or other debilitating disease. It may be arrested for a time in young dogs, but usually the teeth fall out or have to be extracted. As this disease is a progressive one, and mostly occurs in dogs that have their food cut up finely or have soft puppy food given them and teeth are not essential, should any of them become loosened they should be extracted. If the gum has receded in young dogs after some debilitating disease, it should be brushed with peroxide of hydrogen to see if it will arrest its progress. Prevention should be aimed at by giving dogs tearing food.

The rarest disease of the dog's teeth is true dental disease, caries, or properly called decayed teeth. As not one in twenty or more, thousand dogs suffer from it, it need not be discussed, beyond mentioning, should It arise, the tooth should either be stopped or extracted.

An associated disease of the carnassial, sometimes precarnassial or cutting molar or back tooth of the upper jaw is an abscess or swelling on the cheek just below and a little in front of the eye, which bursts and gives rise to a discharge and then heals up, to break out again and again, forming a fistula, etc. As it is mostly due to some disease of the tooth or teeth, which should be extracted, as no other treatment is of permanent use. It is also seen in cats.

There are several defects in the position of the teeth in the jaws, and also defects of the jaw itself, so that the teeth do not meet properly; and as these are not diseases, but only faulty or arrested developments, they will not be discussed, but only mentioned here. The commonest defect is undershot, where the lower jaw protrudes in advance of the upper jaw; and overshot, where the upper jaw protrudes in front of the lower jaw. All degrees of deformity are encountered, that of the upper jaw sometimes advancing several inches. In some cases of chorea, affecting the head and jaws after distemper during youth, when the bones of the skull are still yielding to pressure, the teeth protrude from the mouth outward at right angles, so that the inner surface of the upper teeth meet the inner surface of the lower ones, and not touching at the points.