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58 INSTRUMENTS AND APPLIANCES

The hatchet excavator (Fig. 60; 1 2-5-1 2) has the edge of
the blade running in a direction parallel with the handle, and

is bi-beveled. In the hoe excavator (Fig. 60; 8-3-23) the edge
of the blade is beveled on the side distal (away from) to the
shaft and runs at right angles to it. The hatchet and hoe are
used for the removal of the harder varieties of decay and to
give form to the internal parts of cavities. The spoons (Fig.
60; 10-6-12) and discoids (round spoons) are intended especi-

ally for the scooping out of soft decay, and are beveled only

12 12 12 8 12 12 8 15 15 10 10 15 15 10
5 5 5 3 5 5 3 8 8 6 6 S5 9S 6
6 12 23 23 6 12 23 12 12 12 12 8 8 6
L R
L R 12 \Z
L R
Fig. 60.—Black cutting instruments. Hatchet, hoe and spoon excavators
enamel hatchets, gingival margin trimmers and a bin-angle chisel. Formula names
are shown.

on the distal (far) side. Cleoid means claw-like, the instru-
ment having a sharp point, with two rounded edges running

from it—really a spoon excavator with the bl5,de running to
a sharp point. It is especially designed for deepening the
angles of pulp chambers at the canal entrances.
(b) Chisel.—An instrument designed after the ordinary

carpenter's tool, and intended for cutting enamel. It is
beveled on only one side, and the shank may be straight or
bin-angled (Fig. 61). Enamel hatchet is a variety of chisel
in which the blade (bevelled on one side) is placed in hatchet
5-8-1
form by contra-angling the shank (Fig. 60; 1 2). It is