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the pit (indicating), is not liable to decay, because it is worn
smooth by mastication ; consequently, the treatment is very
simple. If we remove ever so little around that fissure, pro-
vided we remove all decay, and also find a smooth surface
for our finish, so as not to create another pit or fissure in
the margin of our filling, we have removed sufficient to pre-
vent recurrence of decay. But in the proximate surfaces the
case is different. Let this circle represent the contact point
of a bicuspid (indicating), and the immediate point of greatest
liability is just to the gingival of the contact point. Pass your
explorer in to the gingival of the contact point, turn its point
toward the contact point and then pass it across the tooth
just so that its point will come against the contact point and
just there is the point where you are most likely to find the
first beginning of caries in proximate surfaces. Now, that is
true of all the teeth. The interproximate gum tissue should
fill the space completely to the contact point, and so long as
it does this and is not forced away by food passed through, no
decay will occur, for it is the law that no decay
occurs upon any portion of a tooth's surface that is
habitually covered by healthy gum tissue. But, mind you, I
say healthy gum tissue, not diseased gum tissue. Now, this
gum tissue should come to the contact point, and it is only
when it is pushed away slightly that we get decay beginning,
and as the gum tissue recedes from the contact point, from
whatever cause, by reason of age, by reason of a bad con-
tact and food forced through, or what not, the area of liability
is extended just as the gum recedes from the contact point.
Ordinarily the area of liability extends along the margin of
the gum tissue in either direction from the central area of
liability, and just as the gum tissue recedes, from whatever
cause, so the area of liability is spread and becomes greater.
In this (indicating) we have shown the area of liability as be-
ing very large, extending to the buccal and to the lingual
of that particular surface, and it is extended because of the
shortening of the septum of gingival tissue, that septum of
tissue which should fill the space completely.
Now, in your operations it is a matter of extreme im-
portance that you hold this particularly in view and retain the
health of the septum of gum tissue as perfectly as it is pos-
sible to do.

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