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THE RUBBER DAM. 79

rubber is to be released entirely at the end of its application to
each particular tooth and grasped anew for the next. In grasp-
ing it anew for this purpose, the fourth grasp will often l)e moi'e
convenient. The use of this grasp for placing the rubber over
the special clamps, which is really its most imx)ortant use, will
be given below.
It is just as important to know how to remove the fingers
from the rubber without pulling the rubber away with them after
it has been placed on the tooth as it is to place the rubber over
the tooth. Special attention should be given to the necessity of
noting very carefully the manner of doing this, and to the fact
that the dam should be allowed to fully close around the tooth
while the fingers are still pressed against the tooth and gums on
its buccal and lingual sides. When this is done, it will generally
be found that the margins of the hole in the rubber are turned
toward the gingival. This is especially what is needed to render
the rubber secure in its position on the tooth. This applies to all
grasps whatsoever that may be used in adjusting the rubber dam.
In using the fifth grasp, the operator can use the full length
of the forefingers for reaching back into the mouth, and yet have
full command of the rubber and readily place it on the tooth
where the contacts can be passed with a sawing motion of the
fingers ; and, in ordinary cases, it will hold without the aid of a
ligature while passing it over other teeth. Of course, there are
molar teeth around which the gums are so high that the rubber
can not be passed far enough onto the crown in this way for it
to hold. There are also tooth crowns so rounded that the dam
must be forced actually to the gingival line and tied down with
a ligature, or held by a clamp, before it can be induced to remain
in place. With these grasps, however, everything can be done
that it is possible to do with the unaided fingers.

Aids in Adjusting the Eubber Dam.
The ligature. There are many cases in which the rubber
can not be forced between the contact points of adjoining teeth
with the unaided fingers, and then it must be forced with the
ligature. This is done best by an assistant. However, by care-
ful practice, one may learn to do it successfully alone. The liga-
ture may be used with any of the five grasps. To accomplish
this, wrap the end of the ligature on the little finger of the left
hand, and catch a part of its length in the same grasp with the
rubber in the thumb and finger of the right hand, leaving just
sufficient length between so that the ligature may be tightly

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