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THE RUBBER DAM. 4?j

on the second molar. In all cases there should be as clear a
field and as much room for operating as practicable.
The holes in the rubber should be placed in such position
that when applied it will cover the upper lip, lower lip and chin,
but should not cover the nostrils of the patient and interfere
with the breathing. The distance between the holes is an
important consideration. They should always be as far apart as
the mesio-distal breadth of the teeth to be included. In case of
bicuspids and lower incisors that have thin necks mesio-distally,
the distance should be a little greater. This is necessary to
prevent the septum of rubber between the teeth from stretching
into so narrow a band that it will fail to hug so closely to the
necks of the teeth as to exclude moisture.
Rubber Dam Grasps.
The particular manner of grasping the rubber dam when
about to apply it is very important, and should be studied with
much care in the beginning of the student's experience. Cer-
tain ways of grasping the rubber dam are particularly suited to
the application of it in certain positions in the mouth, or to cer-
tain teeth ; also to certain positions of the operator when apply-
ing it. If these are well learned in the beginning it will save
much time, and much of the difficulty in attaining facility in
this work.
In considering these grasps the side of the rubber which,
when applied, will be next the gingivre is called the gingival
side, and that which will be toward the occlusal surfaces of the
teeth is called the occlusal side.
The first grasp is used when tlie dam is to be applied to
the upper front teeth. Grasp the rubber between the thumb
and finger of each hand, with the ends of the thumbs on the
occlusal side of the rubber and their ends touching together
immediately over the hole to be first used, and the finger-ends
midway the balls of the thumbs. .Stretch the rubber a litde
with the thumbs still touching end to end. Then stretch the
rubber a little more, and, standing to the right and in front of
the patient, pass the hole o\ er the tooth; the right thumb on
the lingual and the left on the labial side. In doing this, first
place the free edge of the rubber at one side of the hole between
the teeth, and with a slight sawing motion force it past the