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DENTINAL ANESTHESIA BY CHEMICAL AGENTS. 207
When there is much adipose tissue on the face, the usual negative hand
electrode, covered with a small wet napkin to maintain close contact,
may be better than the application to the face ; but in general the nearer
the cathode is placed to the angle of the jaw, the quicker and surer is
the result of the administration.
The action of cocain administered in this manner is profound. The
effect is primarily upon the contents of the canaliculi, as is shown in
the cataphoric treatment of shallow cavities. After superficial anes-
thesia has been established much lateral cutting will later elicit a degree
of pain ; in deep cavities nearing the pulp, the effect extends to that
organ. The recurrence of sensitivity takes place within a few hours.
No injury appears to follow.
This method of treatment is little required where the degree of
hypersensitiveness is such as to yield to desiccation of the dentin or
the application of carbolic acid combined with caustic potassa (" Robin-
son's Remedy "). But when the pain attending excavation requires
active treatment, such as the employment of zinc chlorid or general
anesthesia, the cataphoric method is far preferable to either, and is
nearly certain of giving relief. Tlie results of successful cataphoresis
are marvellous, and it may be truly stated that no advance of
recent years in the therapeutic treatment of the teeth is comparable
to this.^
Cautious excavation is required after cataphoric treatment, as in the
absence of sensitivity indiscriminate cutting may needlessly encroach
upon the pulp. In case exposure really exists the action of cocain does
not prejudice conservative treatment of the pulp. AVhen devitalization
is determined upon, the anesthesia facilitates this procedure. As stated
in Chapter XVI. cocainization may be then continued either cata-
phorically or by instillation. Should arsenous acid be selected as the
devitalizing agent, cocainization may be used as a preparatory measure
to avoid arsenical irritation.
The Chemical Treatment.
Under tliis head are included the application of warmed air, the use
of coagulants, notably carbolic acid or zinc chlorid, and, in combination
with these, one of the essential oils, preferably oil of cloves, for reasons
stated below.
"Warmed Air.—This metliod is of great value in subacute cases.
It is especially serviceable for the cavities of incisors and biscuspids and
others of easy access. The effect here produced is due to the depriva-
^ For further study of this subject, see " International System of Electro-Thera-
peutics," Section C, p. 1 et seq., Peterson ; also, " Foundation Principles of Dental
Cataphoresis," by Dr. Price, Items of Interest, vol. xx. p. 345.