Page 130 - My FlipBook

126 OPERATIVE DENTISTRY

the pyramids thus choking them to the entrance of the gold.
Again, it may be caused by changing to a plugger "with a less num-
ber of serrations to the millimeter, or one Avherein the serrations
are not as deeply cut, resulting in a collection of pyramids that do
not reach the bottom of the indentations made by the previous
plugger.
Plugger Points Should Have the Same Sized Serrations. Each
operator should have a set of gold plugger points same denomina-
tion as to the cuttings on the working point to use in the same fill-
ing. When forced to change to one of different sized serrations the
surface of the filling should be gone entirely over with the new plug-
ger to be used, before adding additional gold. This will create a new
set of facets to accommodate the gold added with the new instru-
ment. (See Figs. 176A and 176B.)
A little care in this respect will greatly increase the specific grav-
ity of the cohesive gold filling.
Rotating the Plugger in the Fingers Should Be Avoided. The ser-
rations are cut on the square and unless the point is rotated one-
fourth of a circle each time the pyramids will ride the crests of the
indentations, whereas if the shaft is held in one position as described,
the leverage produced by the plane on the surface of the plugger
point coming in contact with the plane on the surface of the filling,
will twist the plugger point to position with each blow of the mallet.
All this will prove plain to the vision if the field of operation is
viewed under a high power lens while operating with a serrated
plugger on the surface of gold in a technic block.
The Size of the Plugger Point. This depends entirely upon the
force with which it can be used. It would seem from all the facts
at hand that a point with the surface of one square millimeter should
be regarded as the maximum. The force required to properly con-
dense gold with a point of greater surface, is either not permissible
in many cases or often not possible with the operator. A point of
one square millimeter should receive a load of 15 pounds pressure at
each contacting of the point.
At the same time points of much less than one-half millimeter
will chop the surface by disturbing the gold close to the point with
each impact ; hence we are limited to a narrow range as to size of
points.
Preparation of the Foil. The gold foil may be used from the
book as it comes from the dealer, and shaped as desired by the oper-
ator, or it may be purchased as cylinders, squares, ropes and various
other forms.