Improvements in Artificial Teeth.
Year: 1894

page_text: UMTAMIN DI MIFICATION.
Improvements in Artificial Teeth.
I, ELI THOMPSON STARR, residing at 4015 Baring Street, in the City of
Philadelphia, State of Pennsylvania, United States of America, Manufacturer of
Dental Appliances, do hereby declare the nature of my invention and in what
manner the same is to be performed to be particularly described and ascertained
in and by the following statement :—
The following is a Specification of my said invention, reference being had to
the accompanying drawings, which illustrate the improvements as applied to teeth
of the superior jaw.
In the manufacture of artificial teeth which are intended to be used in connection
with plates of vulcanite or similar plastic material, and where it is not considered
desirable to use metallic pins for securing the teeth to the plate, it has been
customary to provide a cylindrical cavity extending inward from the base of the
tooth, in order that the rubber, or other material, in a plastic condition might
flow into such cavity and, when hardened therein, secure the tooth against
displacement.
As heretofore made, teeth provided with such cavities have not embodied the
most efficient conditions for permanent attachment.
The rubber support contained within the cavity must of course be strong enough
to resist the maximum strain upon the tooth, and where the cavity is cylindrical,
the diameter thereof must therefore be in correspondence with such maximum
strain. Practically, however, the maximum strains upon the tooth lie approxi-
mately only in vertical planes which intersect both the inner and outer faces,
since strains in other directions are prevented, or minimized, by the presence of
the adjacent teeth. Hence any diameter or cavity which corresponds with the
degree of support required against strains in the former planes, is in excess of
that which is required for strains in other directions, and tends merely to
weaken the structure of the tooth itself, by the removal of an undue amount
of material. The proper proportioning, therefore, of the diameter of the
cylindrical cavity to the size of the tooth, is a matter of considerable difficulty,
since either the contained rubber support, or the tooth, is liable to fall short of
the standard of strength which the organism as a whole should present.
My invention has for its object the attainment of such a distribution of material
as will not render, either part substantially weaker than the other, for the work
which it has to do.
.
To this end I give the cavity within the tooth an oblong cross-section, the
longer axis being in the general direction of the greatest strain, i.e., in a sub-
stantially vertical plane intersecting both the inner and outer faces. Furthermore,
when the tooth is of relatively large diameter, as in the case of molars, I form a
plurality of such cavities with interposed bridges of the tooth material proper,
thus retaining, in the structure of the tooth itself, the normal or proper amount of
material, whilst affording space for the required amount of rubber.
Having thus explained the general nature of the invention, I will now proceed
to describe the same with reference to the accompanying drawings.
Fig. 1 represents a perspective view of a molar tooth, Figs. 2 and 3 being

page_text: "
respectively a plan view and a vertical section thereof on a plane substantially
at right angles to the buccal and palatal faces, the scale of these last two
figures being reduced below that of Fig. 1.
Fig. 4 is a perspective view of a bicuspid, Fig. 5 being an end view thereof
and Fig. 6 a section on a similar plane to that indicated in the case of the molar
tooth in Fig. 3. The scale of Figs. 5 and 6 is slightly reduced from that of
Fig. 4.
.
Referring now to Fig. 1, A indicates the tooth, which may be of any of the
well known materials used for artificial teeth. B and B' represent two parallel
cavities extending inward from the base of the tooth, the cross-section of said
cavities being oval and the longer axis lying in vertical planes which intersect the
buccal and palatal faces. Between the cavities B and B is a bridge or wall, a,
integral with the general structure of the tooth. A transverse duct, b, of small
diameter extends, preferably through the entire structure of the tooth, transverse
to the longer axis of the cavities, B and B¹.
In the bicuspid tooth shown in Figs. 4, 5 and 6, only a single oval cavity, D, is
required, but, as will be noted, the major axis of the oval is in a vertical plane which
intersects both the buccal and palatal faces of the tooth, C. A transverse duct, d,
of small diameter is also formed preferably through the entire tooth.
The operation of the device is as follows:
When the cavities, B and B', in the tooth, A, (or in like manner the cavity, D,
in the tooth, C,) are filled with the plastic material portions thereof will extend
into and completely or partially fill the transverse small ducts, bor d, thus
obtaining a locking action. When, now, the tooth is subjected to the strains of
use, the longer diameter of the rubber within the cavities will be sufficient to resist
any strain that the tooth structure itself is capable of sustaining; whereas, if the
cavity were cylindrical, and of sufficient diameter to give the rubber this degree of
strength, it will be obvious that the tooth structure would have been weakened
correspondingly, so that the organization as a whole would have presented a
relatively weak part, which it is the object of my invention to avoid.
"
It will be understood that for teeth of the inferior jaw, a similar mode of
construction is employed, and the terms "inner" and "outer which in describing
the upper teeth I use as convenient expressions for the palatal and buccal faces,
respectively, would in the case of the lower teeth apply respectively to the lingual
and buccal faces.
Having now particularly described and ascertained the nature of my inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :
1. An artificial tooth having a cavity in its base, the cross-section of said
cavity being oblong and the longer axis thereof lying in a substantially vertical
plane which intersects both the inner and outer faces, substantially as set
forth.
2. An artificial tooth having a plurality of cavities in its base, each of oblong
cross-section, the longer axes of said cavities lying in substantially vertical
planes which intersect the inner and outer faces of the tooth, a wall integral
with the tooth structure proper being interposed between said cavities, substantially
as set forth.
3. An artificial tooth having a cavity in its base, the cross section of said
cavity being oblong and the longer axis thereof lying in a substantially vertical
plane which intersects both the inner and outer faces, said cavity being also
provided with a duct or ducts extending laterally therefrom, substantially as set
forth.
4. An artificial tooth having a plurality of cavities in its base, each of oblong
cross-section, the longer axes of said cavities lying in substantially vertical planes
which intersect the inner and outer faces of the tooth, a wall integral with the

page_text: tooth structure proper being interposed between said cavities, and one or both of
said cavities being provided with a duct or ducts extending laterally therefrom,
substantially as set forth.
CARPMAEL & Co.,
Agents for the Applicant.