Page 106 - My FlipBook

102 INSTRUMENTS FOR FILLING.

sequently last much longer ; and it will cut much
more rapidly than the serrated bur. It is a very
valuable instrument for operating upon firm strong
teeth. It is represented in Fig. 12.

Fie. 12.

Common Drills.—Of other drills, Fig. 13, repre-
sents one with a square point, beveled from both

Fie. 13.

sides, measuring from a half to a whole line in length,
and attached to a small round shaft. The edges of
the drills should be very hard, so that they may cut
with the greatest celerity. Of this kind, there should
be about ten sizes, ranging in width from No. 12 to
No. 25 of Stubb's gauge. These are used mainly for

forming retaining-points in cavities.
Fig. 14.

Fig. 14 is the spear-shaped drill, the edges of which

or, it may be,
are formed by dressing from both sides ;
from only one, in which case it will cut only when