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THE EOKCE USED IN MASTICATION. 161

THE FORCE USED IN MASTICATION IN RELATION TO
THE STRENGTH AND HEALTH OF THE
PERIDENTAL MEMBRANE.

The Foece Used in Chewing Foods.
ILLUSTRATIONS: FIGURES 162-165.
Until recently there was no accurate knowledge of the force
used in mastication. Inquiry was begun in 1893, and in my
articles on "Physical Characters of the Human Teeth," etc.
(Dental Cosmos, 1895), a pretty full exhibit of the subject was
given. Since that time, the subject has frequently been under
investigation. The results then given underwent severe question-
ing, but have not been materially changed by further examination.
There have, however, been published some results obtained with
rudely constructed instruments that have been different, evi-
dently through inaccuracy of observation, and others apparently
different through misconceptions of the nature or of the condi-
tion of material used.
The force of the bite, or the pounds force with which the
jaws may be closed upon any object, varies greatly among differ-
ent persons, and is dependent in larger degree upon the condi-
tion of the peridental membranes and upon personal habits in
the use of the teeth in mastication than upon muscular power.
It has been my habit to make a trial of the force of the bite
every year among the students of my classes and record the
results. In these tests a familiarity with the instrument was
brought out and rivalry was pretty sure to occur among those
of the highest strength which served to develop the full power
of the occlusion. In a tabulation of results in one thousand
persons, the average force exerted was 171 pounds on the molar
teeth, and considerably less on bicuspids and incisors. In this,
there was no selection of persons, further than a careful exclu-
sion from the trials of persons whose teeth were so badly weak-
ened by caries as to cause danger of injury by breakage. In
spite of this prohibition, there were a few accidents to cusps
of teeth that had very large fillings. The variation was from
25 pounds to 275 pounds. Two hundred and seventy-five pounds
is the full register of the instrument used and among the trials
there were seventeen persons who made this full register. A