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THE EXAMINATION. 177

silk should be slightly waxed in order to bind the fibers. Entire
reliance cannot be placed upon the use of silk, since it may in some
cases pass slightly carious spots without the fibers being displaced, but
it frequently furnishes indications for further procedures by which to
estabhsh certainty as to the state of approximal surfaces.
AVedges are used when neither explorers nor silk give positive indi-
cations of carious action but have raised doubts of the integrity of any
part. They may be of wood Avhere the teeth are not firmly fixed, when
the space may be immediately made ; otherwise, where the fixation is
firm, india-rubber or linen tape may be forced in.
Tvansilhnnination of the teeth and of the adjacent parts by the elec-
tric mouth lamp (Fig. 147) is extremely useful in cases where a question
has arisen as to the condition of any approximal surface. Superficial
changes of the enamel may frequently be detected by this means. It
is also of service in diagnosis of derangements of the antrum and to
test the vitality of the pulp.

The Examination.
The parts of the teeth most liable to carious action are those
which most easily retain deposits of sedimentary matter composed of
food debris, thickened mucus, and bacterial growths. These are the
labial and buccal surfaces, where the mechanical relations of the lips
and cheeks tend to retain sediment ; the sulci, which by the direct
force of mastication have food driven into them ; and the approx-
imal surfaces. The latter are the most important to consider.
The interproximal space is a serious predisposing cause of caries, be-
cause the counteraction of the tongue and cheek in adapting the food
between the occlusal surfaces of the teeth forces the finer particles of
the food into the interproximal spaces, where it is retained by capillary
attraction and by the apposition of the cheeks with the buccal surfaces
of the teeth. This space is usually triangular, the gum forming the
base of the triangle. The point where caries usually begins is at the
apex of this triangle, where there is the least movement and inter-
change of the contents of the space, as here the capillary force is the
greatest, so that the fermentative processes of food decomposition are
least interfered with.
The technique of examination is as follows : After a cursory in-
spection of the denture witli the mirror, the explorer is applied to the
previously indicated surfaces, particular care being used in determining
the condition of approximal surfaces, by introducing the instrument
into the triangular space, the ]ioint being directed toward the acute
angle. It should be drawn back and forth with a slight rotary move-
ment so as to impinge the point successively upon the whole a})proxi-
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