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BLEACHING BY HYDROGEN DIOXID. 551
mucus, albumin, and in fact almost every kind of dead organic matter,
its decomposition takes place, evolving oxygen and decomposing the
organic matter either wholly or in part. Hydrogen dioxid does not
bleach all of the decomposition-products of hemoglobin with equal
facility. It quickly removes the pink discoloration following the initial
extravasation of hemoglobin into the dentin, but when the brown stage
has been reached indicative of the formation of hematin its action is but
slight. Later, however, it bleaches more readily. The refractory
nature of hematin with respect to hydrogen dioxid has been experimen-
tally tested upon the substance out of the mouth.
In bleaching discolored teeth with hydrogen dioxid the ethereal 25
per cent, solution known as pyrozone is directly applied to the internal
portions of the tooth upon small pledgets of cotton or cotton wisps
rolled upon a fine flexible canal instrument. After each application
the ethereal menstruum is evaporated by blasts of warmed air from a
hot-air syringe, and the applications similarly made are repeated until
the desired effect is produced. It has been found in practice that more
rapid and permanent effects are produced when the pyrozone solution
is rendered alkaline. This may be readily done by the addition of a
few drops of liquor ammonite fortior or by a solution of one of the
caustic alkalies, e. g. sodium or potassium hydroxid or sodium dioxid,
A very satisfactory method of securing the alkaline effect in this pro-
cess is that suggested by Dr. D. N. INIcQuillen, His method is to
first treat the pulp chamber and canals with applications of Schreier's
Kalium-natrium preparation and after the debris from its action has
been mechanically removed with instruments and cotton twists, with-
out washing the canal, an application of pyrozone is made. The
bleaching action follows with great rapidity, and has apparently greater
permanence than where the pyrozone is used alone. In cases where
the action proceeds very slo^vly, for example when at the end of a thirtv
minutes' continuous treatment the bleaching is not complete, it is Avell
to seal an application of pyrozone upon cotton in the canal and allow it
to remain for twenty-four hours, when a second treatment will usually
complete the operation.
In this as in all bleaching operations it is advisable to fill the tooth
temporarily with some easily removable filling in order to test the per-
manence of the operation, and after the lapse of a reasonable time if
there is no tendency to a return of the discoloration the canals and
cavity may be permanently filled.
Dr. Harlan's method, consists in acting upon hydrogen dioxid by
aluminum chlorid. The aluminum salt is packed in the cavity and
moistened with the dioxid. The technique of the procedure is the
same as for the methods already described. This process was origin-