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72 THE TECHNICAL PBOCEDURES IN FILLING TEETH.

64 the longer reach of the rubber is toward the upper lip instead
of the lower as in Figure 62. The reason for this is sufficiently
obvious. A broader reach of the rubber in that direction is
essential to cover the mouth. It should be distinctly understood
that the primary and principal object of the rubber dam is to
keep the field of operation dry and clean, and it should reach
far enough in every direction to do this. When this has been
accomplished, more is a nuisance. It requires only good reason-
ing with sufficient care in practice to arrange the positions of
the holes correctly for the case in hand. While, in general, two
teeth to either side of the one operated is best, and all things
considered, most convenient and most cleanly, there will be many
cases in which one tooth to either side, as in Figures 97, 99, will
be most available. Yet the former should be the rule. To under-
take to operate with only one tooth exposed, is generally a bad
arrangement.
When the first molars are operated, the rubber should always
include the second. Generally, when the second molar is oper-
ated, the third molar should be exposed. When any of the bicus-
pids are operated, the rubber dam clamp should be on the first
molar, etc.