improvement in facings.
Year: 1895

page_text: Date of Application, 28th June, 1895-Accepted, 3rd Aug.. 1895
improvement in facings.
I, JEPTHA GIDEON HOLLINGSWORTH, of the City of Kansas City, County of
Jackson, State of Missouri, United States of America, Dentist, 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 :--
The object of my invention is to produce, as a new article of manufacture, a
tooth-face of porcelain or equivalent material, which will not crack or split under
the contracting strain exerted by the cooling solder employed to secure the backing
fitted upon the tooth-face, and crown permanently together.
All porcelain tooth-faces, up to the date of my invention, have been manufactured
with a flat back, and therefore had at the junction of the cervical, approximal
and cutting margins with the said flat back, decided angles, and as it was necessary
that the thin backing of gold or platinum should fit perfectly the lingual or
posterior surface of the facing, the dentist had to burnish the backing upon the
facing by hand, and as this was exceedingly particular and tedious work, owing to
the fact that he had to hold a small article of peculiar shape between the ends of
bis fingers and thumb, it is obvious that the backing was bent slightly around the
angles or corners of the facing by the burnishing operation. This slight bend
was desirable, also, in order that the backing should not pull or warp away from
the facing when said backing was united by solder with the crown, as hereinafter
more particularly referred to. Before burnishing the backing upon the facing it
was perforated, and fitted upon the ordinary pius projecting from the lingual
surface of the facing, in the customary manner. The facing with the said backing
was then applied to the crown, and the connection between the backing and the
crown made secure by hot or melting solder, which, contracting as it cooled, caused
the said bent portions of the backing to exert a great pressure upon the said angles
or corners of the facing. This pressure frequently cracked or split the facing,
and therefore rendered it valueless, without taking into consideration the time
employed by a skilled dentist upon it, and the loss of the time necessarily
employed in separating the gold backing and crown from the solder to be prepared
for future service.
Facings of porcelain originally sound, and constructed in accordance with my
invention, cannot be cracked or split by the contraction of the cooling solder, and
therefore are of great commercial value.
In the accompanying drawing, which illustrates my invention,―
Figure 1. is a side view.
Figure 2. is a top plan view.
Figure 3. is a back view.
Figure 4. is a top plan view of the facing, and shows, also, the backing in
section.
Figure 5. is a front view, or view of the concave side of the backing.
All of said figures are on a greatly enlarged scale. In the said drawing,
A designates a tooth-facing which comprises the front or labial face a, of the
required configuration and appearance, and the back or lingual face b, which is
rounded or curved, being what I term an oval or convex hack in trade. This
curvature preferably extends from the cervical to the cutting margin, and from
one approximal margin to the other. The ordinary pins c, project from the
lingual or posterior surface of the facing in the usual mauner, and temporarily

page_text: support the backing d, in its proper position relative to the facing. When solder
is applied to secure the backing and crown together it imbeds said pins, to make
the connection secure and permanent. I term the improved facing the "oval"
back in contradistinction to the straight or flat back facings, which, as herein-
before stated, and as illustrated in dotted lines in Figures 1, and 3, are provided
with the objectionable angles, b', around which the ends of the backing extend, as
also illustrated in dotted lines in Figure 4, at '.
With the flat back it is obvious
that as the solder, which is applied to the backing and crown (not shown) and not
in contact with the facing at all, begins to cool and contract, it causes the end-
portions of the backing to grip tightly the facing, so that the corners or angles of
the same are compelled to sustain practically all the strain. If the backing did
not overlap said angles or corners the contraction of the solder would not secure
the backing closely and snugly against the back of the tooth, but would rather
warp or bend it away so that it would be functionless.
With the oval or convex back, however, it is not necessary to cause the backing
to overlap the margin of the back, but comes flush with the same as shown clearly
in Figure 4. The facing is then applied to a crown of proper form (not shown)
with the backing fitting snugly into a correspondingly contoured opening in the
side of the crown, and the pins (which may be headed or nicked in the ordinary
manner to form a spur or a roughened surface) project into an internal cavity in
said crown, into which is now poured hot or melting solder, which, contracting as
it cools, exerts a gripping pressure upon the curved backing, which slides or
contracts slightly and is held firmly and suugly against the oval or convex surface
of the facing, so that when the tooth is finished up the margins of the backing do
not show, be it either a gold or platinum backing, and the tooth presents an
agreeable and sightly appearance. It also obviates the necessity of grinding the
margins of the tooth, as practiced by most dentists.
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:
As a new article of manufacture, a tooth-facing, having an oval or convex back.
Dated this Fifteenth day of June 1895.
JEPTHA GIDEON HOLLINGSWORTH.