Page 23 - My FlipBook

Instrument NOMENcLATUitE . 19
Formula Names. Sonic instriuuents have the formula stamped
on the handle in figures. There are generally three numbers given.
The first is the Avidth of the blade in tenths of a millimeter. The
second is the length of the blade given in millimeters. The third
is the angle of the blade with its handle given in the hundredths
of a circle.
When a four-number formula is given, as with gingival marginal
trimmers, the second number in the name designates the angle of
the cutting edge of the blade with shaft or handle. This is also
given in the hundredths of a circle.
A plugger is an order of instrument for the packing of material
in the making of a filling. Those for gold are serrated on the work-
ing point in such shape as to result in a surface made up of prisms.
These prisms should be of exactly the same size on all the points
used in any individual filling when packing cohesive gold, as the
interchange of points of different-sized serrations causes bridging.
(See manipulation of cohesive gold, Chapter XX.)
The dental engine is almost indispensable and when properly used
is a blessing to our patients and a time-saver to the dentist. How-
ever, it is all too frequently used, especially by students and young
practitioners, to do things which can properly be done only with
the hand instruments. The misuse of the dental engine has caused
the public to regard it asthe climax of all pain-producing instru-
ments in the dental office, v.hen in reality, if that which should be
done with the engine is properly done, only a few seconds of pain is
induced in the preparation of a very severe cavity.
The engine bur is the working point of the engine and is made
ill many shapes and sizes. However, those which are round and in-
verted cones, whose diameter is smaller than one millimeter, are
most frequently indicated. The tendency of the beginner is to use
too large burs. Burs are primarily intended to cut dentine in out-
lining cavity walls, and for undermining enamel to facilitate the
use of hand instruments and they should rarely come in contact
with the enamel.
The most indispensable use of the engine is for the polishing and
grinding necessary to the successful termination of many varied
operations, both in and out of the mouth.
The sharpening of instruments is of the utmost importance and
is by no means accomplished without skill. No better can a dentist
execute finished work than can a tradesman whose tools must be
keen of edge if he is to produce that which is worthy of his craft.
Again, dull instruments cause an undue amount of pain at each at-