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Tig. 170.

Fig. IVI.

Fig. 173.

Figs. 170-173. A sciies illustmtiiig the cutting of convenience points, which, in the proximal
cavities in the bicuspids and niohirs, arv intended to prevent movement of the gold in the building
of the proximal portion of the filling. These are not intended for any especial service as resistance
or retention anchorage for the filling in after use.
Fig. 170. The most common form of the convenience point, showing only a small portion
of the bucco-axio-gingival region of the cavity as seen complete in Figure 173. When the cavity
is otherwise completed, an inverted cone bur 8 or 10 is pressed into the angle, cutting mostly
into the buccal wall without sinking into the gingival wall, and then drawn toward the occlusal
for a short space. It is then replaced and the cut repeated a sufficient number of times to make a
cut a little less than the width of the bur head in depth, which thins away and runs out toward
the occlusal.
Fig. 171. In positions in which special difficulty in this first building is expected, the first
pieces of gold will hold a little stronger if the bur head is sunk just a little, one-half the length of
the bur liead, into the gingival wall.
Fig. 172. The convenience point as prepared with a chisel. This is the best form for operators
who have as much as eighteen or twenty pounds hand pressure, otherwise the cut with the bur is
best.
Fig. 173. A cavity with the convenience points cut in the axio-bucco-gingival, and the axio-
linguo-gingival angles.