Page 123 - My FlipBook

STRENGTH OF THE BITE. 119

chews feebly will not do this. A person who is chewing with
artificial teeth generally can not. A person who can use 40
pounds pressure upon artificial teeth is doing very well, and such
persons will often find their beefsteak very tough ; but a per-
son who can crush down 200 pounds can eat any beefsteak. In
the ordinary chewing of beef or flesh, great force is not required,
we may say, and yet, if we catch upon a bone, or in game, upon
a shot, we will get a terrible jolt upon the teeth, for we actu-
ally use much more than the necessary force. That is as likely
to come upon fillings as upon any other part of the tooth, and,
of course, will give the strength of the filling a sore trial.
In chewing meats the motion is directly up and down ; we do
not use the lateral movement in chewing meats. In this we
copy the motions of the carnivorous animals. The carnivorous
animals have their jaws hinged so that they have but the up-and-
down motion used in crushing. We crush our meats ; we do
not grind them. In chewing bread, or any of the grains — the
cereal foods— we do use the lateral motion ; we grind them ,-
we can not crush them. The more we crush upon bread the
more we pack it between the cusps of the teeth. A little lateral
motion will cause it to go to pieces quite readily, but we can not
crush even a comparatively soft bread crust with all the force
that we can put upon it ; it will simply pack into the sulci be-
tween the cusps of the teeth and remain there. This is shown
very readily with the phago-dynamometer. If I put a piece of
comparatively soft crust in the instrument and put on a pressure
of 60, 80 or 100 pounds it is simply packed between the teeth
and has not been cut through at all, A litde lateral stress will
grind it. Patients used to come to me saying that they had
broken the cusp off of a bicuspid, for instance, "just biting a
piece of soft bread." Sometimes I thought it was a kind of a
joke, and sometimes I felt that it was absolute dishonesty I did
;
not know the facts until I began to try the artificial chewing of
food. Then
I found that there was a substantial reason for it,
for in taking a piece of bread crust between the teeth, without
having it wet, we may crush with all the force of the muscles and
simply pack it between the cusps of the teeth and bring to bear
a powerful splitting force, calculated to throw off a cusp from a
tooth. In this way we lose the cusps of a good many teeth,
and teeth are broken from plates, crowns are broken, bridges