Year: 1887

page_text: Date of Application, 31st May, 1887.
Specification Accepted, 19th July, 1887.
WAS
I HENRY HARRIS LAKE of the firm of Haseltine Lake & Co. Patent Agents,
Southampton Buildings, in the County of Middlesex, do hereby declare the nature of this
invention and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement :-
This invention relates chiefly to the removal of plaster of Paris from dental plates.
In the manufacture of dentures of vulcanized india rubber the mould in which they
are vulcanized is usually formed of plaster, that being the most convenient material
for obtaining the counterpart of the wax model which is obtained directly from the
mouth.
In vulcanizing in plaister moulds it frequently happens that the india rubber and
plaster so adhere to each other that portions of the plaster are torn from the mould in
the act of separation, and adhere to the vulcanized plate with great tenacity.
Hitherto it has been exceedingly difficult to separate the plaster from the plate
without injuring either the plate or the teeth.
My invention consists of a process by which plaster is readily aud quickly
disintegrated and may be removed with great rapidity.
I take the plate with adhering plaster and the fingers of the operator being protected
from casual spattering by an india rubber glove or finger cots, I brush upon the
plaster with a small brush a solution of hydro-fluoric acid, which can now be obtained
commercially the principal use of which hitherto has been in the etching of glass. 1
have discovered that the commercial solution has very slight effect upon the enamel of
artificial teeth the fact being that a contact of several hours hardly does more than to
affect the surface polish. I use for this purpose a small common bristle or camel
hair brush. The hydro-fluoric acid immediately disintegrates the plaster as if by a
process of wet calcination and the dental plate being taken to a sink and scrubbed
TDA7

page_text: with an ordinary tooth brush, and washed, preferably with running water, the plaister
is immediately removed much as if it were simply adherent dust or mud. And the
polish and colour of the vulcanized plate are not interfered with. Something which
will do this has long been a desideratum with dentists.
It is obvious that for any purpose where the disintegration of plaster is desirable
substantially the same process can be employed.
Having now particularly described and ascertained the nature of the said invention
and in what manner the same is to be performed as communicated to me by my foreign
correspondent I declare that what I claim is :-
First. That improvement in the art of dentistry, which consists in the rapid disin-
tegration and removal of the plaster which adheres to vulcanized dental plates after
vulcanization, by disintegration caused by the application of an aqueous solution of
hydro-fluoric acid, and subsequent washing and scrubbing in water substantially as
described.
Second. The process of removing adherent plaster of Paris from objects to which it
adheres by means of an application of hydro-fluoric acid to the plaster substantially as
described.
Dated this 31st day of May 1887.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.