Page 122 - My FlipBook

118 THE TECHNICAL PROCEDURES IN FILLING TEETH.

Therefore, the teeth are abundantly strong, unless we happen
to catch them on a bit ot gravel or a large bit of sand, or some-
thing of that kind that is extremely hard. Half a dozen stu-
dents who tried the force of their bite on the Knatho-dyna-
mometer* during one of my lectures last year, registered
respectively, 155, 190, 250, 220, 225 and 150 pounds. This
represents very fairly the usual amount, and the variations in the
stress persons with fairly good teeth, and of ordinary habits in
their use, can exert. A few will exert a greater stress, as much
as 275 or 300 pounds. Many people who use their teeth deli-
cately will stop at 100 pounds or less.
Often persons have registered 100, 130, and, occasionally,
200 pounds and over on the central incisors. Generally per-
sons biting upon the instrument stop because it hurts the peri-
dental membranes; they do not register the full power of the
muscles of the jaws. A few tell me they have exerted the full
power of the muscles without pain, and in these cases I suppose
the full power of the muscles is registered.
In chewing food we use, as a rule, very much more stress
than is actually required to crush the food. By trying the
crushing strength required, with the phago-dynamometer f we
may find the crushing power required for the various foods.
Filberts that school children are in the habit of crushing with
their teeth give a register of from 100 to 150 pounds, occa-
sionally more. In chewing meats much difference in the required
stress is shown, good beefsteak requires from forty to sixty
pounds, tough beefsteak from sixty to eighty pounds, occa-
sionally more. Mutton chops usually require from thirty to
forty pounds, pork chops (loin) twenty to twenty-five pounds,
broiled ham from forty to sixty pounds, etc. If any one in
chewing a piece of beefsteak will notice it he will hear a crack-
ling sound just at the time the fiber of the flesh is breaking up.
We can notice that also in the phago-dynamometer, and just at
the time that the fiber is breaking up we find that the meat
crushes out from between the teeth and the teeth pass through
it and come together. Most person in chewing meats of any
kind crush their teeth through it at a dash. A person who
* An instrument for measuring the force with which the jaws may be closed.
t An instrument for measuring the crushing force necessary in chewing different
articles of food.