Page 284 - My FlipBook

should not be overlooked. Caries never makes a beginning
on a portion of the tooth surface covered by a healthy gum
septum or gum margin. All such portions are strictly im-
mune. A margin of a filling so laid that it will be continu-
ously protected by healthy gum tissue is as safe as if laid
upon a surface fully exposed to the friction of mastication.
Therefore the preservation of the health of the septum of
gum which normally fills the interproximate space to the
contact point is one of the important factors in treatment.
It follows, therefore, logically, that in the preparation of
these cavities, they must, in order to be curative, be cut so
far into the embrasures both to the buccal and to the lingual
that the excursions of food in the act of mastication will
sweep their marginal lines and keep them constantly cleaned,
and the gingival margin must be so laid that it will be cov-
ered by the gum septum. Then if the form of the proxi-
mate surface, and especially of the contact point, is so made
that it will protect this gum septum, and sufficiently prom-
inent to preserve the full mesio-distal breadth of the tooth,
•the permanence of the filling made with technical skill is
assured. This is termed extension for prevention. It ap-
plies to all proximate cavities. '
For the development of the highest skill in carrying out
these procedures the conditions should be carefully studied
from mouth to mouth in the cases presented in practice.
In persons belonging to highly susceptible families and who
present a number of beginning decays close examination
will show, when the surfaces are cleaned and dried, whitened
areas of enamel leading away from the central area of pen-
etration to the buccal (or labial) and to the lingual close
to the margin of the gum. This is really incipient decay
and it should be carefully noted, and the form of the area
studied with reference to the proximating teeth and to the
marginal edge of the gum tissue. The directions taken by
food in its excursions over the neighboring parts during
mastication and its effect in cleaning the parts should re-
ceive especial attention. By this kind of study carried on
from mouth to mouth the operator will learn to appreciate
the areas of the surfaces of the teeth liable to decay and
become able to lay the margins of cavities on lines of com-
parative immunity.

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