Page 188 - My FlipBook

156 FILLING MATERIALS

Intermediates

Sensations of heat and cold are rapidly transmitted, by
means of the dentinal fibrillae, to the pulp from the walls of
cavities, and as the permanent filling materials are conductors

of these physical forces, it becomes necessary in all cavities,
except extremely shallow ones, to place non-conducting
substances between the filling and the walls of the cavity.
These materials are known as intermediates, and the act of
placing them in position is known as Pulp Protection. The
substances most frequently used are Cement and Gutta-

percha. Cement itself is a slight conductor, so that in
extreme cases of hypersensitivity a thin layer of Gutta-percha,
Chloropercha, or one of the Cavity Linings, is applied, and
then covered with cement, when the balance of the filling is
placed in position. Cavity Linings are colorless, transparent
liquids, which, on evaporation, leave a thin, non-conducting

film on the walls of cavities. Prominent varieties of these
are Cavitine, Gilbert^ s and Caulk^s Cavity Lining.
Technical Exercises.
1. Carefully mix a batch of cement, according to the
directions given above, stirring in small amounts of the pow-

der at a time, and spatulating thoroughly to accomplish
mechanical and chemical union of powder and liquid. Roll
into a round mass.
2. Mix another batch by adding the powder in large

amounts, and avoiding thorough spatulation. Roll into a
mass as in No. i.
3. Place the two mixes in ink or aniline dye for twelve
hours, and then compare for cutting consistence as well as
amount and penetration of the stain.

4. Insert several cement intermediates in the cavities
already prepared, building some up in step form.