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DENTINAL ANESTHESIA BY ELECTRICAL OSMOSIS. 203
amperemeter also aids in detecting leakage of current, as Mdiere the
indicated amperage exceeds five-tenths milliampere there is reason to
suspect imperfection of the insulation of the tooth. In this case a
longer period than usual will be required to effect the anesthetization,
and the decree of this effect mav be less.
The use of the direct current generated by the dynamo is of ques-
tionable utility as compared with the current from a battery. The
current from the dynamo is subject to changes of voltage and the
amperage is liable to fluctuations consequent upon alterations of the
load in the general circuit. This instability causes a series of pulsat-
ing shocks upon sensitive dentin and the pulp, which react with the
expression of pain. The possibility of the transmission of severe
shock through accidental grounding or defective apparatus where such
excessive voltage is used is another and sufficient reason why the
steady and low-voltage current of a battery is preferable for this class
of operations.
TECHNIQUE OF THE ADMINISTRATION.
At the present period cocain has been found to be the most effective
anesthetic for obtunding dentinal sensitivity by electrical osmosis. It
is used in strength varying from 12 to 24 per cent., and by some as
high as 40 per cent, has been used ; li grain of one of the salts of
cocain added to 5 minims of water procures a solution of 24 per cent.
to 7|- minims, 18 per cent. ; to 10 minims, 12 per cent.
The salts of cocain which have been used are the hydrochlorid and
the citrate. Each is efficient in the strength stated. The resistance of
cocain citrate is for 12 percent, solution 234 ohms; for 24 percent.
153 ohms. The resistance of cocain hydrochlorid is for 12 per cent,
solution 80.85; for 24 per cent. 61.25. These provings indicate that
the hydrochlorid is the better salt of cocain for the purpose.^
The tooth to be operated upon is isolated by means of a rubber dam
and is ligated at the cervix to prevent leakage of current. If there are
metallic fillings in the tooth, these should be covered with a coat of
varnish carefully laid on and dried. Tin's precaution docs not alwavs
possess the value claimed for it, as the dentin beneath a metal filling,
because of its density or lack of porosity, will not convey the current
as well as the carious matter and the softer dentin of the fresh cavity.
In some cavities where caries has occurred at the cervix above srold
fillings, and which do not permit of complete isolation of the fillings,
the cataphoric influence is not interfered witli.
The carious matter should not be completely removed and need onlv
be partially dried. The cavity is loosely filled with a small pledget
'The writer is indebted for the determination of these resistances of cocain sohitions,
etc., to Mr. A. AV. Schramm, of the University of Pennsylvania.
DENTINAL ANESTHESIA BY ELECTRICAL OSMOSIS. 203
amperemeter also aids in detecting leakage of current, as Mdiere the
indicated amperage exceeds five-tenths milliampere there is reason to
suspect imperfection of the insulation of the tooth. In this case a
longer period than usual will be required to effect the anesthetization,
and the decree of this effect mav be less.
The use of the direct current generated by the dynamo is of ques-
tionable utility as compared with the current from a battery. The
current from the dynamo is subject to changes of voltage and the
amperage is liable to fluctuations consequent upon alterations of the
load in the general circuit. This instability causes a series of pulsat-
ing shocks upon sensitive dentin and the pulp, which react with the
expression of pain. The possibility of the transmission of severe
shock through accidental grounding or defective apparatus where such
excessive voltage is used is another and sufficient reason why the
steady and low-voltage current of a battery is preferable for this class
of operations.
TECHNIQUE OF THE ADMINISTRATION.
At the present period cocain has been found to be the most effective
anesthetic for obtunding dentinal sensitivity by electrical osmosis. It
is used in strength varying from 12 to 24 per cent., and by some as
high as 40 per cent, has been used ; li grain of one of the salts of
cocain added to 5 minims of water procures a solution of 24 per cent.
to 7|- minims, 18 per cent. ; to 10 minims, 12 per cent.
The salts of cocain which have been used are the hydrochlorid and
the citrate. Each is efficient in the strength stated. The resistance of
cocain citrate is for 12 percent, solution 234 ohms; for 24 percent.
153 ohms. The resistance of cocain hydrochlorid is for 12 per cent,
solution 80.85; for 24 per cent. 61.25. These provings indicate that
the hydrochlorid is the better salt of cocain for the purpose.^
The tooth to be operated upon is isolated by means of a rubber dam
and is ligated at the cervix to prevent leakage of current. If there are
metallic fillings in the tooth, these should be covered with a coat of
varnish carefully laid on and dried. Tin's precaution docs not alwavs
possess the value claimed for it, as the dentin beneath a metal filling,
because of its density or lack of porosity, will not convey the current
as well as the carious matter and the softer dentin of the fresh cavity.
In some cavities where caries has occurred at the cervix above srold
fillings, and which do not permit of complete isolation of the fillings,
the cataphoric influence is not interfered witli.
The carious matter should not be completely removed and need onlv
be partially dried. The cavity is loosely filled with a small pledget
'The writer is indebted for the determination of these resistances of cocain sohitions,
etc., to Mr. A. AV. Schramm, of the University of Pennsylvania.
