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136 THE TECHNICAL PROCEDURES IN FILLING TEETH.

oil then diffuses through the mass of the gutta-percha and is lost,
apparently, leaving the gutta-percha adhering firmly to the cavity
walls. Therefore, for this purpose the cavity -walls should
only be moistened. No excess of the oil should be allowed
to remain in the cavity, as the effect will be to soften the whole
mass of the filling.
Prepare the gutta-percha by gently warming it over
the flame of the alcohol lamp, or upon a warm tray. Care
should be had not to heat the gutta-percha too hot. This will
develop an inordinate stickiness of the mass, and it will not
again become fully hard; the quality of the material is per^
manently injured.
When it is made just plastic by heat, convey it to the cavity
in small pieces and build the filling up from the most convenient
angle or wall of the cavity piece by piece, sticking the warm
pieces to the mass in the cavity with a considerable pressure, and
condensing well against all walls and margins. In this work it is
well, if possible, to add no more of the material than will just fill
the cavity, having none to remove in trimming. If, however, a
surplus has been added, warm a small flat burnisher sufficiently
to quickly soften the gutta-percha upon contact, and with this
cut away the surplus, and immediately condense and adjust the
surface of the filling with a cold burnisher that has been laid
ready. The finish should generally be made entirely with the
burnisher, as we can not polish the surface of the filling by any
of the usual means. By waiting until the filling is fully hard it
may be trimmed with a sharp knife, but the edge must be very
sharp to cut smoothly. This is the best instrument for remov-
ing overlaps and making a good finish of margins.
Another plan of filling with gutta-percha that is useful in
many cases, especially cavities of easy access, is to form a mass
that will just fill the cavity and warm it only sufficiently to obtain
the necessary plasticity, (and insert the whole filling in one piece,
condensing with a broad, cold instrument, afterward finish as
before described.
Much experience is required to handle gutta-percha
well, but when once the manipulation has been learned it is not
difficult, and requires but little time. It should be the only
material used for sealing in dressings, and for the temporary
stoppings in connection with treatments.