Page 357 - My FlipBook

SCREW. 353

SCREW.

This is a cone-shaped instrument, with a very
definite, sharp screw-thread; the manner of using
it in the operation of extraction is, to screw it into
the root. It will be required of various sizes to

correspond with those of the different roots to be
extracted. It is commonly attached to the handle
by a permanent shaft (Fig. 79) ; but, sometimes, it is
Fig. 79.

made with a square shaft fitted into a socket handle
(Fig. 80), by which arrangement the handle is used
only to introduce the screw ; and this serves only as
a support to a frail root, the forceps being then brought

Fig. 80.

e{&&*
to bear in connection with it, for the removal of the

root. A screw-tap, of the same form as the screw,
should accompany it.
When the screw is combined with the forceps, for
the purpose of supporting the root and preventing
it from crushing while it is removed with the forceps.