Improvements in Dental Cemente.
Year: 1899

page_text: Date of Application, 7th Nov., 1899-Accepted, 9th Dec., 1899
Improvements in Dental Cemente.
I, ALBERT PAUL TSCHIRNER, a Citizen of the United States, residing at
No. 507, North Spring Avenue, in the City of St. Louis, State of Missouri,
United States of America, Dentist, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
It is well known that zinc phosphate dental cements contain more or less
glycerine, which is added for the purpose of obtaining a plastic, workable
mass, and to lessen the quick action of the phosphoric acid on the oxide of
zinc. As these glycerine compounds are very unstable, being unable to with-
stand the action of the saliva, it has been desirable to obtain a filling material
avoiding the use of glycerine or any soluble, foreign substance which would
deteriorate or waste away in the mouth.
It is the object of my present invention to produce an insoluble, phosphate
of zine cement, in which no glycerine or any other soluble substance is used.
My invention consists in a liquid compound, the base of which is an acid
phosphate of zinc, combined with a powder consisting mainly of oxide of zine,
with other busic oxides added in various proportions, for the purpose of
adapting my cement to the various operations required in dentistry.
In carrying out my invention, I have found the following formulas to
auswer admirably, but it is obvious that the proportions given can be changed,
and the ingredients also changed, without, in the least, departing from the
nature and principle of my invention: In a fluid ounce of phosphoric acid,
having approximately a specific gravity of 1.69, I dissolve 160 grains of oxide
of zinc, and then add two drams of aqua ammonia, after which the liquid is
evaporated to a density of about 1.945. The powder to be used in conjunction
with the above liquid is composed of four parts of oxide of zinc, six parts oxide
of tin, and two parts oxide of aluminium.
To use the cement, a desired quantity of powder is mado plastic by the
liquid compound, as is well understood.
ounce of
Another illustration of my invention is as follows: In a fluid
phosphoric acid, specific gravity 1.69, I dissolve 120 grains of oxide of zinc,
and forty grains of oxide of aluminium. The powder to be used in conjunction
with this compound is composed of four grains of oxide of zinc and six grains
of oxide of tin. In the last mentioned formula, the aluminium is introduced
into the liquid compound instead of the powder as stated in the first illustra-
tion. In both illustrations it will be noticed that the cement is formed of
insoluble basic phosphates, free of any substance soluble in water, such as
glycerine, gelatin, or other similar substances.
It will be noticed that in the above two formulas, both contain liquid and
powder constituents. The liquid constituents of the first formula are composed
of phosphoric acid and oxide of zinc, the ammonia being introduced to form
a union between the two and prevent hardening of the zinc, so that the phos-

page_text: phate of zine will remain liquid for a long time. The powder constituent
in this first mentioned formula containing the oxides of zinc, tin and aluminium,
is thoroughly mixed before the liquid is added to it, and after the addition of
the liquid, the basic phosphates are formed, and, being of the proper proportion,
will harden slowly, giving the operator ample time to manipulate it before the
hardening process is completed. In the last mentioned formula the liquid
constituents contain the oxide of aluminium in addition to the other ingredients,
and the powder constituent, the oxides of zine and tin. In this formula the
aluminium is merely transferred from the powder to the liquid constituent,
the proportion of the parts being substantially the same.
In the preparation of the powder constituent and after it is mixed I take
a small quantity of shellac and dissolve it in alcohol, of such quantity so that
when the shellae solution is mixed with the powder constituent, it makes a
sort of dry paste, which is then permitted to dry out, with the result that the
little particles of powder are enclosed in the coating of shellac. The object
and purpose of this is to render the oxides impervious to the atmosphere.
Were the oxides exposed, they would absorb carbonic acid gas, and the powder
constituent would deteriorate before it was used.
My cement has the following advantages: It is a perfect chemical compound
composed solely of insoluble basic phosphates, free of any substances which
are soluble in water: permanently insoluble has a high degree of density and
hardness is a non-conductor of heat, and, therefore, avoids irritation of the
dental nerve and is readily adaptable to the tooth cavity, thereby insuring
the exclusion of moisture and bacteria.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. The herein described dental cement composed of liquid and powder consti-
tuents, said constituents being made of phosphoric acid, ammonia, and metallie
oxides, such as zinc, tin, and aluminium: substantially as described.
2. A slow hardening cement free from substances soluble in water, the same
consisting, when hardened, of insoluble phosphates of zine, tin, and aluminium;
substantially as described.
Thated the 21st day of Ontation 1900
PHILIP M. JUSTICE,
Chartered Patent Agent, London, for the Applicant.