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THE RUBBEB DAM. 77

The third grasp is a modification of the second, in which the
two hands are simply inverted, so that the thumb of the left is
on the occlusal side of the rub1)er and the thumb of the right is
on the gingival side. In every other way, the grasp is the same.
This is suited to placing the rubber on the lower teeth of the left
side of the mouth as far back as the second bicuspid, and on the
upper teeth of the right side as far back as the second bicuspid,
the operator standing on the right side behind. Figure 72 shows
the position of the rubber in the hands with the hole stretched
open a little. The rubber dam is then carried over the tooth and
the first movement completed, as shown in Figure 73. The grasp
on the rubber is then released to allow it to close around the
tooth while held against the gingivae with the finger and thvunb
nails, as shown in Figure 74.
The fourth grasp is a complete inversion of the first. In
this the thimibs are both placed on the gingival side of the rub-
ber, and both forefingers on the occlusal side. The rubber is
grasped with the thumbs opposite the first joint of the forefin-
gers, or thereabouts. The ends of the forefingers come together
over the hole to be used, not directly end to end, but in the form
of a letter V, the finger-ends forming the angle. The rubber is
now stretched so as to open the hole slightly, while the finger-
ends are close against its margins. Figure 77. Then it is carried
over the tooth, stretching the rubber sufficiently by spreading the
fingers apart, made to pass the contact points between the teeth,
one after the other by a slight sawing motion, and the finger-ends
(the nails next to the tooth) carried hard against the gingivae,
one on the buccal side and one on the lingual side of the tooth.
This completes the first movement. Figure 75, upper, and Fig-
ure 78, lower teeth. Then the grasp of the thumbs is released
while maintaining the position of the fingers, and the rubber
allowed to close around the tooth. If the rubber is felt to close
on the finger-ends, which it will often do, and fails to close on the
tooth, make a slight oscillating motion of the fingers, which will
allow it to slip past them and hug to the tooth before removing
the fingers. This completes the second movement. Figure 76,
upper, and Figure 79, lower teeth. The rubber is now grasped
anew and in the same way, to be passed over the next tooth, being
careful to place the finger-ends very close on either side of the
hole to be used in each instance.
This grasp is particularly suited to the upper bicuspids and
first molars, the oi^erator standing on the right side behind the
patient. For this, the head of the patient should be thrown well
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