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FITTING THE CROWN. 313

of the crown. This apparatus would be good, were it
not for the great difficulty of dressing porcelain teeth
with a file. By care, a very complete fit can be
made with a round file alone. Some coloring material,

as rose pink, for instance, may be put on the base of
the crown, and then the tooth, with the pivot inserted,
set in its place—when the root will be marked where
the crown has touched it, and this can be dressed at
the point of contact. This operation is repeated till a
perfect fit is attained. This method is to be recom-
mended to those who have had but little experience
in adjusting pivot teeth.
Another method of making the articulation is, to
dress the end of the root square, and then counter-
sink it about half a line deep with a square-ended

bur, about three fourths the diameter of the root.
The base of the crown is then ground down, by the
measure of the bur, perfectly round, so as exactly to
fit into the depression in the root. The bur used for
counter-sinking the root should have a center-point to
fit into the hole in the root, and thus guide the instru-
ment. This method of fitting on crowns is objection-

Fio;. 59.

able, by reason of its too great exposure of the root
of the tooth. Fig. 59 represents the bur used for