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FILLING CANALS • 233

or mixed with salol, aristol, or iodoform; salol; Prinz' root

canal filling (composed principally of bismuth and paraffin).
Chloro-percha preparations, as well as the resin solution, for
canal filling should have a small percentage of bismuth sub-nitrate
added to them, else they do not show properly under the X-ray.
Making Gutta-percha Points.—These may be obtained
ready prepared. An excellent method of making them in the

laboratory of various sizes and shapes is as follows: Warm a
clean, smooth cement slab. Cut off a small section of Gutta-
percha base-plate, and after heating it over the alcohol lamp,
roll into a cone between the clean thumb and forefinger.

Lay it on the warm slab, and with a warmed, broad, clean
cement spatula, roll it out quickly into a long rope. As the
rope gets longer and longer it will be convenient to hold one
end by pressing it on the slab while using the spatula in the
other hand, and working it with a back and forth movement.

The roll, as it approaches the proper size, may be cut into
sections, and then each section may be rolled separately into
any size desired. These sections may then be cut into
convenient lengths, with the hot spatula or a knife.

Technical Exercises

1. Open the pulp chambers and canals of the teeth pre-
pared under Pulp Treatments, the presence of the wax cover-
ing the apices of the roots serving as a guide to prevent the
passage of the canal instruments too far.
2. Seal in the pulp chamber and canals several cotton

dressings containing anodyne, antiseptic and formo-cresol
treatments.
3. Remove the dressings, dry and fill the canals after the
methods described.