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APPROXIMAL CAVITIES IN IXCISORS. 113

this instance it would be especially so, since it weakens the incisive
end of the tooth, the very point which must sustain the full and first
strain of mastication.
It follows, then, that we may depend entirely upon the labio- and
palato-gingival extensions, together with the labial and palatal groov-
to retain contours such as shown in this
ing, approximal figure.
When the depredation becomes so extensive that the grooves would
encroach upon the living pulp, we are compelled to adopt new methods.
Fig. 119 shows a cavity of this nature. Strictly speaking, the line
of the original pulp-chamber has here been passed, the pulp having
receded before the approach of the decay, a common occurrence.
Sometimes we may even see the plain outline of what was once the
chamber now filled with secondary dentine. To make the lateral
grooves here would be hazardous. To arrange the cavity as described
in Fig. 115, depending only upon the upper retainers, might prove
ineffectual. In this dilemma the screw comes to our assistance, ar-
ranged as in the illustration. Up to the point where the screw be-
comes a necessity there is no imaginable cavity which cannot be shaped
and in teeth from which the have been removed
to retain a filling, pulps
we are seldom driven even to this extremity. I have built down from
the gum line complete crowns on centrals, laterals, cuspids, and bicus-
pids, without resorting to screw or post, and yet have obtained durable
(though according to present standards and in the presence of the
crown unsightly) results.
porcelain
Where we use the screw to retain such a filling as would be needed
in Fig. 119, we still have the labio- and palato-gingival extensions,
the screw passing upward along the median line. My method of fill-
ing is to pack my gold solidly into my upper retainers first, connecting
them. Then I drill through the gold thus placed and into the tooth-
substance beyond. The drill-hole is then tapped, the screw turned
tightly into place, and cut off just short enough
not to reach to the line of the incisive edge, after
which the filling is completed with small pieces, care
being taken to properly surround the screw.
In 1 20 we have the extreme condition where
Fig.
but one corner is involved. These cases are usu-
the result of fracture, though they sometimes
ally
occur where such a cavity as Fig. 119 has been
improperly filled, with the result of subsequent
decay and destruction along the incisive edge. As the latter would be
the I will speak only of such as result from accidental blows.
simpler,
These cases are frequently very puzzling. They most often occur
during childhood. When they do, unless the pulp be exposed, as
sometimes occurs, or unless the should die as the
unfortunately pulp
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