40 
DENTAL FISSURES AND CAVITIES. 
though it is commoner at nine or ten ; but in older horses it is less 
frequent. 
Causes. In man, caries is caused by decomposition of the fluids of 
the mouth, or of food remaining between the teeth. This process, without 
doubt, is assisted by micro-organisms, perhaps by the Leptothrix buccalis, 
and may extend to neighbouring teeth. In animals the disease 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 filled 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, impossible 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 suffi¬ 
ciently 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, and Wulff a resin com¬ 
position. The details of both cases are, however, so meagre that it 
is impossible to say whether the condition was really one of caries. 
Possibly the stoppings served to replace lost teeth. Stoppings can 
certainly be used for this purpose. 
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. 26) 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 Gunther’s pointed forceps are sometimes sufficient. Where 
the crown is broken but the tooth remains firm it can only be removed 
by punching. 
(b) 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 swallow them 
directly, without attempts at mastication, and because such objects 
are then retained in one or another of the stomachs. The fourth 
molar, which stands in the centre of the curved row, and suffers most 
