Page 33 - My FlipBook

INSTRUMENTS AND INSTRUMENTATION. 29

the labial enamel margins until the proper form has been
reached. The hatchet 12-5-6 performs the same office for the
gingival wall. Very often, in the more delicate of this cutting,
the middle sizes, i. e. , hoe 8-3-6 and hatchet 8-3-6, will serve
better and in many cases it will be found more convenient to use
the same sizes in the angle of 12 centigrades, or the hoe 12-5- 12
and hatchet 12-5- 12, etc., or the sizes 8-3. The smallest size,
or 6-2-6 and 12, are used only in shaping the internal parts of
cavities in the incisors and cuspids, and especially in squaring
out the axial line angles of these cavities so that they are sharp
and definite. The angles of 23 are convenient for reaching cer-
tain points not easily reached with the angles 6 and 12, but are
used much less than the latter.
The Specials.
The set of specials are so called because each instrument is
designed for a special use. The formulee of this set are upon a
different set of sizes, the plan of measurement being the same.
In these are also three widths and lengths of blade, three sizes
and one angle of blade of 12 centigrades for all except the
binangled chisels, which are 6 centigrades angle.

Formulas of the Specials.
Straight chisel, 20, width only given.
Straight chisel, 15.
Straight chisel, 10.
Binangle chisel, 20-9-6.
Binangle chisel, 15-8-6.
Binangle chisel, 10-6-6.
Enamel hatchets, rights and lefts, 20-9-12.
Enamel hatchets, rights and lefts, 15-8- 12.
Enamel hatchets, rights and lefts, 10-6- 12.
Spoons, rights and lefts, 20-9-12.
Spoons, rights and lefts, 15-8- 12.
.Spoons, rights and lefts, 10-6- 12.
Gingival margin trimmers, rights and lefts, 20 (95)-9-i2.*
Gingival margin trimmers, rights and lefts, 20 (8o)-9-i2.
* NoTK.^Whcii it becomes necessary to designate the angle of tlie cutting edge of
an instrument with its shaft, it is done by sliding it, without rotation, to the left, still
keeping it parallel with the longitudinal lines, until the angle of the cutting edge corre-
sponds with one of the lines of the larger numbers to the left. This number is then
entered in brackets following the width number. When not so designated the cutting
edge is at right angles with the length of the blade.