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Fig. 5, C, represents different shapes of Arkansas stones that may be
used in finishing the margins and cavities. It is not intended that they be
used for grinding to any considerable extent, but to poHsh the margins.
Fig. 6 sliows two forms of hoe excavators that are useful in
shaping the walls of cavities and giving to them definite angles. A
represents that form which is useful in shaping the gingival wall, while
B represents the form that is useful in shaping the axial walls.

FIG. 6.

Cavities on the Cabial and Buccal Surfaces.
If the cavity extend beneath the gum margin,
the gum should be forced from the cavity with
Torcina
the Gum from the base plate gutta percha. The gingival and approx-
eaoity. imal walls should be prepared with an inverted cone
bur so that they form a slight undercut. The gutta
percha should be packed in such manner that sufficient pressure to cause
the gum to recede will be made upon it so that it will not interfere
with the preparation of the gingival margin. In case it is inadvisable
to form undercuts in any of the walls of the cavity, the gutta percha
should be packed tightly into the cavity and secured with a silk ligature.
While cavities on the labial surfaces of many
marginal teeth are usually found in the gingival region, they
Outlines. occur also in the middle and incisal thirds of the
labial surfaces of many teeth. Cavities on the labial
and buccal surfaces of teeth usually assume some of the forms shown
in Figs. 7 and 8. The circular form is usually found in the middle and
incisal thirds of teeth. In the preparation of most cavities in the gin-
gival region on these surfaces, the other forms of marginal outline
should be used.

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