Page 245 - My FlipBook

USE OF RUBBER DAM. 213

Generally where the case under treatment is an approximal surface
the necessary preparatory separation makes easy the immediate open-
ing of any interstices near the operation. In cases of extreme fixa-
tion of the teeth a piece of rubber dam placed for a day or so in a
coujile of the neighboring spaces makes it easy to enter the margin of
the interstices. The passage of a silver tape with a little benne oil or
cosmolin on it often answers as an equivalent means. In the front
teeth a thin wedge inserted just above a tight point permits an easy
entrance.
The preliminary silking of the adjoining spaces, particularly if the
silk be coated with cosmolin or its equivalent, also facilitates the
passage of the rubber, and for this purpose soaping the under surface
of the rubber adjacent to the holes is recommended.
At tirst the novice finds difficulty in making application of the dam,
but practice cultivates facility. In general it is better to commence
with the anterior hole and proceed posteriorly until all the intended
teeth are included. Thus fi)r the left lower teeth the rubber is taken
with the index fingers applied to the upper surface, the other fingers to
the under surface, and is grasped near the hole for the front bicuspid ; the
hole is extended ; the edge of the rubber is inserted in the mesial inter-
stice and is carried down to the gum. It is then drawn over the tooth
and passed into the next interstice in the same manner. This method
is pursued with each tooth until all are included. The passage of the
rubber is facilitated by helping it downward l)v the insertion of floss
silk, Avhich is held taut, and with a firm and gently sliding movement
the rubber is conveyed toward the cervix.
When the most distant tooth is the lower third molar, it is generally
best when the cavity is on either side of the last interstice to pass the
jaws of a dam clamp through the posterior hole ; the clamp is then made
to grasp the tooth, the dam is conveyed to the gum by silking, and the
adjustment is then carried forward from tooth to tooth. The same pro-
cedure is sometimes applicable with short third molars in the upper
denture, or in case any of the posterior teeth are so shaped as not to
retain the rubber.
When the rubber is adjusted over the teeth the purpose of the dam
is eifected by directing the edge of the dam under the free margin of
the gum. This is done by passing a silk thread around the tooth, and
crossing the ends, Avhen by a drawing movement of the thread it travels
down the inclined surface of the cervix, carrying the dam with it, thus
making a more secure formation of the valve.
This method avoids the needless paining of the patient caused by
pushing the threads against the gum with instrimicnts. Whenever
necessary for securement the ligature should be tied. This should be