286 DENTAL FISSURES AND CAVITIES. 



enamel by lactic acid, is produced by fermentation of the fluids of 

 the mouth, or of carbohydrates remaining between the teeth. This 

 process is caused by micro-organisms, and may involve several teeth 

 at the same time. In animals caries probably depends on similar 

 causes, but it is exceedingly rare. It is not known whether this 

 rarity is due to the more rapid wear of the teeth in animals, or to 

 some peculiar property of the saliva. Stockfleth considers that a 

 predisposition to caries is often inherited. 



Prognosis depends entirely on the extent of the caries. In man 

 its extension can be checked by " stopping " the tooth. With this 

 object the cavity is drilled, cleared of all carious matter, thoroughly 

 disinfected, and rilled with some material which will protect the still 

 healthy parts from further attack. The " filling " consists either of 

 metal, like gold or amalgam, or of some other hard substance, such 

 as cement. Very rarely, however, can this be done in animals, least 

 of all in horses. It is, therefore, seldom possible to save a tooth 

 when once attacked, the more so as the condition is usually only 

 noted when disease is extensive. It then becomes a question whether 

 the animal is able to masticate sufficiently with the teeth that will 

 remain after those which are diseased have been extracted. In the 

 horse, caries seldom affects a number of teeth, hence this question 

 is usually determined in the affirmative. Varnell states having used 

 a stopping of gutta-percha, Wulff a resin composition, and others 

 an amalgam. The details of these cases are, however, so meagre 

 that it is impossible to say whether the condition was really one of 

 caries. No doubt caries can be arrested by thoroughly cleansing 

 and properly filling the carious cavity. Stoppings are sometimes 

 used to replace lost teeth. 



Treatment consists in early extraction. Care, however, is required 

 in using the forceps, as the softened crown is liable to break off. The 

 " Universal " forceps (Fig. 294) must not be screwed up too tightly, 

 and if the tooth be loose particular care is necessary. Extraction 

 is easiest where purulent alveolar periostitis exists, or where the 

 tooth is splintered. In such case Giinther's pointed forceps are 

 sometimes sufficient. Where the crown is broken off but the fang 

 remains firm it can only be removed by punching. 



FISSURES AND CAVITIES IN THE TEETH. 



Fissuring is commonest in the horse's molars. It is rarer in oxen, 

 not because these animals less frequently pick up stones, nails or 

 similar hard bodies— the contrary is the case— but because they 



