Page 230 - My FlipBook

202 THE MICRO-ORGANISMS OF THE HUMAN MOUTH.

colored, render it still more difficult to perceive small cavities
here than in horses' teeth.*
I have examined a few pig
Fig. 103. skulls and found hut one small
point of decay. Since pigs eat
much fermentable food, we
should expect decay more fre-
quently, in spite of the alkalin-
ity of their saliva, if the teeth
were not so compact, and par-
ticularly if the animals were not
slaughtered at so early an age
(two to three years).
The conditions which explain
the comparatively rare appear-
ance of decay in animal teeth
are, in my opinion :
1. The firm structure of ani-
Dkcated Dextise from a Horse's mal teeth.
Tooth, showing the destruction of the
2. The nature of their food
tissue by bacteria. 800 : 1.
(but little fermentable).
3. The alkalinity of their saliva.
4. The comparatively short time during which the teeth are
exposed to the causes that produce decay.

SPOTANEOUS HEALING OF DENTAL DECAY.
The process of decay, if not retarded by the proper treatment,
usually results in the complete destruction of the crown. Cases,
however, occur (comparatively seldom) which strangely deviate
from the usual course, in that the destruciive process ceases spon-
taneously, and the already softened dentine becomes hard again.
This process is most frequently observed in the permanent first
molars, but it also occurs in milk-teeth. Some years ago I ex-
amined the mouths of a boy and girl (twins, three years old)

*In more than one hundred skulls I could not establish with certainty the
presence of any trace of decay. I was, on the other hand, astonif^hed at the fre-
quency of exostoses and destructive processes on the roots of sheep teeth.