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30 THE TECHNICAL PROCEDUKES IN FILLING TEETH.

ferences in form. The general tendency noticed is toward smal-
ler and smaller working points in all cutting instruments and
pluggers. This has reference to those instruments in greatest
use by dentists, decade after decade. With this difference in
size has also come a difference in instrument grasps, and in the
method of handling instruments in dentistry. All of the older
instrument forms were based on the developments in fine carv-
ing and engraving. Carving was highly developed in very
ancient times. The instruments for all of the more delicate
work were adapted to manipulations in which the object being
cut could be turned to suit the hand and the instrument grasp.
In all of the books on dentistry more than one hundred years
old, the instrument handles were designed to be grasped in the
same way as instruments were grasped by persons doing fine
carving. The handles were large, the points were large and
rigid and they were used with the palm grasp, palm-and-thumb
grasp, or palm-thrust grasp. See instrument grasps, Figures
26-30. The dentist operating on the natural teeth could not
turn the tooth about to accommodate his hand. And as the con-
ception of the delicacy needed in this work grew in his apprecia-
tion, we find that he gradually changed the forms of his
instrument handles, making them suitable for the more delicate
pen grasp with its larger variety of applications, and reduced
the size of the working points in proportion to the reduction
of power in the form of grasp. This is clearly a case of the
survival of the fittest, or those forms and methods of use of
instruments best adapted to the objects designed. Enamel and
dentin are hard substances to cut, and in order to cut them
effectively, the force that can be exerted by the hand with the
grasp used must be concentrated upon a very short length of
blade. It is a mistake to use a broad blade, of a chisel for
instance, where much enamel is to be cut away. The length of
the cutting edge is too great for the power of the hand to do
effective work. Narrower blades and more careful direction
by the hand contribute to speed, because the whole force of the
hand is concentrated on the smaller area and becomes that much
more effective. The dentist should never lose sight of this fact.
At the present time and with the excollont quality of steel
that it is possible to put into instrument points, these should
always be small and the edge should be kept in the best condi-
tion. AVitli pro]K>r care, and es})e('ially with a ])roper ai^precia-
tion of the strength of steel, a liglit chisel or excavator, i)roperIy
tempered, is rarely broken. The breakage of instruments is