Page 52 - My FlipBook

20 THE TECHNICAL, PROCEDURES IN FILLING TEETH.

secting at right angles the plane of the angle or angles, or is at
right angles with the shaft.
Chisel. Straight blade with cutting edge formed by bevel-
ing from one side. The blade is usually straight with the shaft,
but may be slightly curved.
BiNANGLE chisel. A cMsel blade placed at a slight angle
with the shaft in the hoe form. They are contra-angled.
Enamel hatchets. Chisel blades placed in hatchet form
by the direction of the angles of the shank. They are made
rights and lefts by the bevel of the cutting edge ])eing placed on
opposite sides of the blades to constitute the pair. They are
intended to assist the chisels in chipping away overhanging
enamel and other work in the preparation of cavities.
Spoons. The spoons are always made in pairs. They are
first made in the form of enamel hatchets and then the blade of
the one is curved to the right and the blade of the other is curved
to the left, then the cutting edge is ground to a semi-circle and
sharpened to a thin edge. This curve of the blade is in a plane
that intersects at right angles the plane of the principal angle
or angles. This direction of the curve of the blades makes the
instruments true rights and lefts, i. e., lateral cutting instru-
ments.
Gingival margin trimmers. These instruments are formed
like the spoons both as to the curves of the blades and the dimen-
sions, but the angle of the cutting edges of one pair is arranged
for beveling of the cavo-surface angle of the gingival wall of a
mesial cavity, and the angle of the cutting edge of another pair is
arranged for beveling the cavo-surface angle of the gingival
wall of a distal cavity. For this work the cutting edge is
ground in a bevel instead of being ground to a thin edge as in
the spoons. They have no other use.
Discoid (Disc-like, circular). The blade is circular in form,
having a cutting edge extending around the whole periphery,
except that portion by which it is joined to the shank. This
circular blacle is placed at more or less of an angle with the
shaft.
Cleoid (Claw-like, in the form of a claw). Sharp pointed
blades in the form of a claw, with cutting edges on two sides of
the blade.
SUB-CLASS NAMES.
A sub-class name is one applied to, and is descriptive of the
angles and curves of the shank of an instrument wliich leads
to the blade or working point.