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BASIC ZINC CEMENTS. 339
precaution to line the latter witli one of the quick-drying ethereal var-
nishes, to protect the dentinal walls from contact with acid sodium
phosphate Avhich may be present in the cement. In some cases the
placing of the cement in proximity to a non-exposed pulp is productive
of marked suffering. Should the cavity
Fig. 316. Fig. .318.
be very deep it is the usual practice to
place a softened disk of gutta-percha
over the wall nearest the pulp. The
rubber dam should always be adjusted
before the insertion of a phosphate fill-
ing, to insure dryness not only during
the insertion, but during the period of
hardening, at least fifteen minutes.
MixiXG OF Cement.—This is an
operation of equal, if uot greater, im-
portance than any other in the manipu-
lation of zinc phosphate. Dr. Henry
Weston has demonstrated how, almost
entirely, the mixing of cement gov-
erns its stability. Specimens of the
Dropper.
same powder and fluid mixed after dif-
ferent methods gave entirely different
results, not only in the ajipearance but
also in the hardness, texture, and solu-
bility. The method of mixing set forth
is that of the same experimenter. As- Fig. 317.
sumiug for illustration that an approx-
imal cavity is to receive a contour filling,
or a large occlusal cavity is to be filled,
Fig. 3M
^ip~
Glass mixing tablet, with rubber feet.
or an extensive cavity is to be three-
fourths filled with cement hiiiiii
Scoop. Spatula.
A drop, or, where a large mass of
cement is required, two drops of fluid are placed upon a scrupulously
clean glass (Fig. 315) by means of the dropper shown in Fig. 316, and
BASIC ZINC CEMENTS. 339
precaution to line the latter witli one of the quick-drying ethereal var-
nishes, to protect the dentinal walls from contact with acid sodium
phosphate Avhich may be present in the cement. In some cases the
placing of the cement in proximity to a non-exposed pulp is productive
of marked suffering. Should the cavity
Fig. 316. Fig. .318.
be very deep it is the usual practice to
place a softened disk of gutta-percha
over the wall nearest the pulp. The
rubber dam should always be adjusted
before the insertion of a phosphate fill-
ing, to insure dryness not only during
the insertion, but during the period of
hardening, at least fifteen minutes.
MixiXG OF Cement.—This is an
operation of equal, if uot greater, im-
portance than any other in the manipu-
lation of zinc phosphate. Dr. Henry
Weston has demonstrated how, almost
entirely, the mixing of cement gov-
erns its stability. Specimens of the
Dropper.
same powder and fluid mixed after dif-
ferent methods gave entirely different
results, not only in the ajipearance but
also in the hardness, texture, and solu-
bility. The method of mixing set forth
is that of the same experimenter. As- Fig. 317.
sumiug for illustration that an approx-
imal cavity is to receive a contour filling,
or a large occlusal cavity is to be filled,
Fig. 3M
^ip~
Glass mixing tablet, with rubber feet.
or an extensive cavity is to be three-
fourths filled with cement hiiiiii
Scoop. Spatula.
A drop, or, where a large mass of
cement is required, two drops of fluid are placed upon a scrupulously
clean glass (Fig. 315) by means of the dropper shown in Fig. 316, and
