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INSTRUMENTS AND INSTRUMENTATION. 31

ments. In positions in which the access is direct it is a more
convenient instrument than the spoons, though generally the
spoons are better.
The cleoid is used most for trimming out the angles of pulp
chambers in order to reach the canals with the broach more
readily, especially the canals in the mesio-buccal roots of the
upper molars and the mesio-buccal and mesio-lingual angles in
the lower molars.
The two hatchets, 5-3-28 and 3-2-28, are used only for the
purpose of undercutting the incisal angle of proximate cavities
in the incisors and cuspids for the purpose of obtaining retention
form. They are designed for this special purpose and are used
for nothing else whatever.
Instrument Grasps and Rests.
The manner of holding instruments in performing dental
operations is very important. There are two principal grasps
:
The pen grasp and the thumb and palm grasp, with modifica-
tions of both.
The pen grasp is used for most operations. As implied in
the term, the instrument is held in the fingers in the position, or
with the same grasp with which we would hold a pen, and the
manipulation is carried on with the instrument held in that posi-
tion, whether in cutting with an excavator or packing gold with a
plugger. Perhaps nine-tenths of these operations should be done
with the instruments held in that way. Occasionally positions
are found in which the operation may be much facilitated by a
modification of this grasp, made by bending the fingers into, or
nearly into, the palm of the hand, thus inverting the position of
the instrument so that it points directly at right angles to the
length of the arm. This is called the inverted pen grasp.
In the use of these grasps certain rests for the fingers should
be sought and practiced until they are correctly obtained without
especial thought. By the use of these rests operations can be
much more accurately performed than without them, and they
gready limit the danger of injury to the patient by slips of the
instrument.
The rests are generally made by placing the third or fourth
finger, preferably the third, upon the teeth of the same jaw in
which the tooth operated upon is situated. In operating upon