Page 342 - My FlipBook

338 EXTRACTION OF TEETH.

rained by the line of power and the axis of the tooth,
is sixty degrees or more. The line of force is not
changed by any form the hook may assume —it may
;
be regularly cr irregularly curved, or be turned at
right angles, and yet the line of force is not changed.
Indeed, this line can not be changed, except by

changing the relative position of the hook and its at-
tachment. This application of the power constitutes
one of the prominent objections to the use of the in-
strument : the force is applied at too great an angle
with the axis of the tooth, and her.ce, in numerous
instances, it is broken off. The bolster of the key
rests, in the operation, on the gum, on which it
exerts great pressure, and which it always bruises,
and frequently lacerates in a cruel manner ; the press-
ure exerted by the bolsters of the variously con-
structed keys differs but little ; though, perhaps, the
bolster which has a broad base, and attached to
the shaft by a joint, would cause less pain to the

patient by its pressure, and be much less liable to
lacerate or cut the gum, than the small and perma-
nent one. The pressure of the bolster on the gum
and process is always greater than the power required
to extract a tooth ; and this extreme pressure and its
consequences constitute another strong objection to
the use of the key. The power being applied at a
disadvantage, much more is required than when
economically applied.