DENTAL TARTAR. 
41 
under the severe friction of one grinding surface on the other, is most 
frequently affected. Without doubt want of hardness, which is often 
produced by caries, greatly favours splitting, while other causes may 
lower the resistance of the tooth. Such conditions may possibly 
originate during foetal life, a view which receives confirmation fiom 
corresponding teeth on either side being often splinteied. Hard 
substances accidentally present in the food also produce. splitting, 
especially in animals which masticate energetically. Sometimes only 
a piece of the crown breaks off, but very frequently the crack extends 
as far as the root. The tooth may be broken 
into several pieces, which separate, injure the 
tongue or cheek, and make chewing painful. 
While Assuring is confined to the crown no 
serious consequences ensue; hut should the 
fracture extend to the alveolus, particles of food 
and fluids may enter and inflame the alveolar 
periosteum. 
Treatment consists in removing the splintered 
tooth, and is seldom difficult. Sometimes the 
pieces are too small to be grasped by ordinary 
forceps, and in such cases Gunther s pointed 
forceps are useful. (Fig. 28.) 
(c) DENTAL TARTAR (CREMOR DENTIUM). 
Alike in animals and men the fluids of the 
mouth deposit on the teeth a grey-biown 
coating called tartar. It is commonest in dogs 
and vegetable feeders, but very rare in cats. 
Pet dogs suffer oftener than others. According 
to Fiirstenberg’s investigations tartar in dogs 
and horses consists principally of phosphate 
of calcium, carbonate of calcium, carbonate of 
magnesium, and organic substances. lion and 
manganese have also been detected. Microscopical examination shows 
that the material is formed chiefly of vegetable particles, various 
bacteria, epithelium from the cavity of the mouth, and several salts 
of calcium held together by salivary mucus. The deposit is oftenest 
seen on the outer surface of the crown, turned towaids the cheek. 
It commences in the neighbourhood of the gums, and gradually spreads 
upwards and downwards. Incisors and molars are alike affected, the 
latter more frequently, but in horses the tushes are the commonest seat. 
A pale yellow or greenish brown chalk-like substance, rather rough on 
the surface, covers that portion of the crown lying nearest the gum. In 
Fig. 18 .—Teeth scalers for 
dogs. 
