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SINGLE PIVOT TEETH AND CROWNS 39

If the roots be in so bad a condition that they
cannot be preserved, and if their loss might affect the
arch, they should be replaced by artificial roots, into
which the lower ends of the pivots of the teeth extend.
Roots of this kind may be obtained by cutting off
the lower ends of tube teeth, and building up roots
by means of prosthetic compound.

Single Pivot Teeth and Grow^ns.
For fastening front and single pivot teeth the use
of S. S. White's plate-pins are the most suitable.
As to durability, no difference has been noted by
me between pure platinum and base metal pivots.
A root is prepared for these pivots so as to give it
the form of a dowel crown. Only when the root is
very weak should a gold collar be fitted.
As a rule, collarless roots are of greater durability
than those fitted with collars, a point which is due
to the irritation of the soft tissues collars may cause.
It will therefore be better not to grind off the root
above the gum.
In case of extensive decay in a root, the tooth should
be cut at this place, and by fusing on to the tooth
the root is given a dovetail-shaped support ; on the
opposite surface the same operation should be per-
formed (Fig. 29).
The length of the pivot is a factor of less importance
than the exact grinding of the plate and its perfect fit
to the root. This may be obtained by putting per-