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332 PLASTIC FILLING MATERIALS.
indicates a lowrring of the standard heat, it may he cjuickly restored
by a moment's holding of the heater over tlie llaine, -wliich will again
fuse the metal.
"When the flame is a])plied directly under the metal, as in the illus-
tration, the material placed at 1 will, when the metal is seen to be fused,
be at the heat of near 208° F., while the pellets at 2 will be heated to
about 200°, those at 3 and 4 to near 194° and 180° respectively. Of
course the location of the heat-source will |)r()(lu('e corresponding varia-
tions in the relative temperatures of the materials as severally situated \
but with a visibly definite standard such as the metal A, having a known
fusing-point, the desired degree of heat may repeatedly be produced at
any place on the receiving surface of the heater. A few seconds' contin-
uance of the heater over the flame, after the metal has melted, will raise
the surface heat to 212° or 215°, as the case may be ; but as a suitable
indicator for a high-heat stopping, a button {B) of metal fusing at 230°
is provided as a substitute for A, which is first melted and poured out
on a piece of clean paper, the heater cavity being undercut so that
when cold the metal cannot be shaken out. The boiling of a few
drops of water in the heater cavity will likewise serve to indicate
the proper temperature, but the fusible metal is in every way pref-
erable. The best plan is to hold the heater over the flame until the
^ „,,^ metal melts, set down the heater, blow hot air
Fig. 307. '
, . ^ ^ \ • -i
luto the previously prepared and dry cavity until
_^,^j^^^^,siw- -ri^^
yC/^ the tooth is sensibly warm, hold the heater again
j I
/ // over the flame to melt the metal, and then with a
,
I I ~^ I
~~^""^/^/ suitable broad and cold instrument pick from the
heater a pellet or group of pellets suificient to a little
/
more than fill the cavity, and by a quick, firm, rock-
/J
Trimming margins of iug pressure force the mass into the cavity as if it
gutta-percim filling. ^^r^rQ^^Q sought to take an impression of the same.
Then dip the instrument into ice-water, wipe dry, and hold it firmly
against the filling for one or more minutes, after which with a keen-
edged thin blade pare off* the surplus, cutting from the centre obliquely
toward the margin, as in Fig. 307, taking great care that the filling B
shall be flush with the cavity margin at every point, as at A, A', Figs.
308 and 309.
" Access to approximal cavities, as C, C, Figs. 298 and 299, will
seldom permit the instantaneous mass-method just described, but in
many such cases a warm, broad, flat blade, as stiff as the space will
admit, can by repeated quick pressures be made to squeeze the soft mass
into the cavity of the warmed tooth, and be instantly followed by a very
thin strip of metal held tightly in both hands and wrapped with hard
pressure over the filling around that side of the tooth, to both condense
332 PLASTIC FILLING MATERIALS.
indicates a lowrring of the standard heat, it may he cjuickly restored
by a moment's holding of the heater over tlie llaine, -wliich will again
fuse the metal.
"When the flame is a])plied directly under the metal, as in the illus-
tration, the material placed at 1 will, when the metal is seen to be fused,
be at the heat of near 208° F., while the pellets at 2 will be heated to
about 200°, those at 3 and 4 to near 194° and 180° respectively. Of
course the location of the heat-source will |)r()(lu('e corresponding varia-
tions in the relative temperatures of the materials as severally situated \
but with a visibly definite standard such as the metal A, having a known
fusing-point, the desired degree of heat may repeatedly be produced at
any place on the receiving surface of the heater. A few seconds' contin-
uance of the heater over the flame, after the metal has melted, will raise
the surface heat to 212° or 215°, as the case may be ; but as a suitable
indicator for a high-heat stopping, a button {B) of metal fusing at 230°
is provided as a substitute for A, which is first melted and poured out
on a piece of clean paper, the heater cavity being undercut so that
when cold the metal cannot be shaken out. The boiling of a few
drops of water in the heater cavity will likewise serve to indicate
the proper temperature, but the fusible metal is in every way pref-
erable. The best plan is to hold the heater over the flame until the
^ „,,^ metal melts, set down the heater, blow hot air
Fig. 307. '
, . ^ ^ \ • -i
luto the previously prepared and dry cavity until
_^,^j^^^^,siw- -ri^^
yC/^ the tooth is sensibly warm, hold the heater again
j I
/ // over the flame to melt the metal, and then with a
,
I I ~^ I
~~^""^/^/ suitable broad and cold instrument pick from the
heater a pellet or group of pellets suificient to a little
/
more than fill the cavity, and by a quick, firm, rock-
/J
Trimming margins of iug pressure force the mass into the cavity as if it
gutta-percim filling. ^^r^rQ^^Q sought to take an impression of the same.
Then dip the instrument into ice-water, wipe dry, and hold it firmly
against the filling for one or more minutes, after which with a keen-
edged thin blade pare off* the surplus, cutting from the centre obliquely
toward the margin, as in Fig. 307, taking great care that the filling B
shall be flush with the cavity margin at every point, as at A, A', Figs.
308 and 309.
" Access to approximal cavities, as C, C, Figs. 298 and 299, will
seldom permit the instantaneous mass-method just described, but in
many such cases a warm, broad, flat blade, as stiff as the space will
admit, can by repeated quick pressures be made to squeeze the soft mass
into the cavity of the warmed tooth, and be instantly followed by a very
thin strip of metal held tightly in both hands and wrapped with hard
pressure over the filling around that side of the tooth, to both condense
