Artificial Tooth Crowns and Manufacture of the same.
Year: 1887

page_text: Artificial Tooth Crowns and Manufacture of the same.
I, GEORGE EVANS of the City, County and State of New York, United States of
America, Dentist, 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 :-
This invention relates to improvements in contouring artificial crowns employed to
build upon the sound root of an imperfect tooth a grinding surface, corresponding in
character and form to the natural grinding surface of an original crown.
My invention consists in shaping hollow cup-shaped crowns of gold, silver,
platinum, or other suitable material into a form corresponding with greater accuracy
to the peculiarities which characterize the tooth to be replaced than has been
accomplished by methods heretofore employed; especially to contouring the sides of
the crown; and in order that others skilled in the art to which my invention relates
may be enabled to understand and use the same, I will proceed to describe the
distinctive features of its construction, explain the use of the same, and set forth in
the appended claims such characteristics as are novel.
Referring to the drawings in which like letters of reference indicate like parts
throughout the several views.
Fig. 1 is a sectional view of the usual crown blank made of one piece.
Fig. 2 a similar view of the component parts of a crown blank to be subsequently
completed by soldering.
Fig. 3 a blank having its grinding surface stamped upon it by former methods.
Fig. 4 an elevation, partly in section of the dies heretofore employed for imparting
to the blank the grinding surface.
Fig. 5 an exterior perspective view of a crown completed according to my
invention.
Figs. 6 and 7 sectional views and
Fig. 8, a plan view of a sectional die by means of which my improved process may
be carried into effect.
Figs. 9 and 10 a plan, and a longitudinal interior elevation respectively of a
modified sectional die.
Figs. 11, 12 and 13, perspective views of sectional moulds illustrating a modified
manner of using the same.

page_text: Fig. 14 a sectional view of a "contracting plate" commonly used in dentistry.
Fig. 15 a perspective view of a sectional contracting mandrel.
Fig. 16 a sectional view of a blank having had its aperture contracted by said plate
or sectional mandrel.
Fig. 17 a section of a contracting plate having a contouring cavity made according
to one form of my invention.
Fig: 18 a metal crown shaped in the contracting plate Fig. 17.
Fig. 19 a perspective view of a contoured contracting plate and crown mould shown
detached therefrom; and Fig. 20 a sectional view of the same, showing a crown in
position therein, being formed.
Fig. 21 a sectional view illustrating a method herein referred to of treating the
crown with filling before contouring.
Fig. 22 a sectional view of a modified construction of moulds.
Fig. 23 a side view of a crown, designating certain technical divisions of the
same.
Fig. 24 a side view of a sectional mandril.
Fig. 25 an end view of the same.
Fig. 26 an end view of a separate mandrel.
Fig. 27 a perspective view of a partially disconnected mandrel.
Fig. 28 a perspective view of a mandrel crown, and crown shaping device, and
Figs. 29 to 33 modified forms of dies and blanks hereinafter referred to.
Hitherto the blanks of metal having a grinding surface stamped thereon as in
Fig. 3, which represents a crown having a grinding surface approximating in shape
to a perfect molar tooth, have been adjusted to the cervical margins of the root by
bending the sides of the blank by imperfect means, such as the application of pliers,
and approximating the form so as to force the same into position; the form of said
grinding surface being produced by means of hammering the same between a pair of
dies of a construction shown in Fig. 4, which manifestly fail to impart to the sides of
the blank a form approaching a natural contour.
My process as practised in the manner illustrated by Figs. 1 to 10 inclusive, is as
follows:
An accurate impression of the tooth to be crowned is first taken by means of
pressing thereon a plastic material, such as Plaster of Paris, and dividing the same so
as to remove it from the tooth, and retain in it the counterpart cavities or impressions
corresponding to the surfaces of the tooth. This is allowed to harden, and from this
mould is obtained an exact duplicate of the tooth in regard to form by compressing
therein a plastic substance of any suitable composition, of a quality which will
afterwards resist heat.
The duplicate of the tooth thus produced is now used as a core for casting in a
mould a pair of dies of metal, or other suitable material, and having any convenient
exterior form, as shown in Figs. 6, 7 and 8. For these dies I prefer to use Babbitt's
metal, or other alloy fusible at low temperature may be likewise used.
The dies are preferably cast in two parts A B and matched by means of flanges, or
tongues and sockets a, cast on their edges, so that the interior surfaces of the mould
shall coincide when brought together.
Between the sections of the dies so obtained, 1 place a crown b, of platinum, gold,
or other suitable thin malleable metal, such as shown in Fig. 1, consisting of a plain
blank or like Fig. 3, a blank having a convenient grinding surface stamped thereon,
or in cases where the blank is composed of separate pieces as shown by Fig 2,
each part 6, 6, of the same may be applied separately, or together before or after
being soldered.
The dies A, B, are now brought together, or nearly together, and held by the hand,
or clamped in a suitable clamping device, in the position shown in Figs. 7 and 8,
during which operation the sides of the crown will be forced approximately into the
irregular cavities of the dies.
A suitable burnishing tool 62, such as commonly used in dentistry, or a revolving
burnisher, or other equivalent is now applied to the interior of the crown, and by

page_text: means of this instrument, the malleable metal is pressed or forced into the more
minute recesses of the sectional cavities, by continued pressing and burnishing of
every part of its interior surface.
The dies being separable the finished crown may be readily removed, its inner part
or irregularities of the same being usually of a size in excess of the aperture of the
mould.
The grinding surface of the crown is formed from the smooth cap of the blank,
Figs. 1 or 2, or altered from the stamped shape shown in Fig. 3, during this
operation to conform with the peculiarities of the tooth corresponding to the
mould.
Should the top and sides of the crown be applied in separate pieces, within the
sectional dies Figs. 6, 7, 8 they may be soldered subsequently to the operation herein
described. For convenience of forming the sides of the metal in a separate piece, a
modified pair of dies such as shown in Figs. 8 and 9, may be employed; the feature
of said modification consisting in having the cavities or mould of the dies open at
either end and permitting easier access to, and observation of the interior while the
burnishing instrument is being applied to form the said portions of the metal.
In the instance of Figs. 8 and 9, compound dies are illustrated, which additional
feature is equally applicable to the preceding forms of dies; the several cavities or
moulds bearing no relation to one another, but corresponding to various teeth, the
said construction being intended for purposes of convenience in casting, or rapidity of
forming the several crowns at one operation.
The dies A and B shown by Figs. 11, 12 and 13 may also be used for forming the
opposite sides of the crown separately, in the manner illustrated by Fig. 13; said dies
being conveniently modified in exterior form for the purpose.
My invention further comprises certain improved devices which are analogous
in some features, to those known in dentistry as *6 contracting plates" used for
contracting and shaping the aperture, and converging the sides of crowns by forcing
the same into converging holes in the contracting plates, and adapting them thereby,
to fit the sound root of the imperfect tooth as required.
These devices are illustrated by Figs. 11 to 23, inclusive, and combine in a single
device, the functions of a contracting plate, and of a contouring mould for forming
the sides of the crown blank into a natural form. An elementary construction of this
improvement is shown, exaggerated in a certain degree, in Fig. 17; the feature
therein being the reversed curved profile of the contracting aperture as appears in
section at c and d. The curves d, impart to the opening of the crown an elongated
lap upon the cervical margins of the root (d¹, Fig. 18) while the curves c impart to
the sides of the crown a convex contour c¹ as illustrated.
The perfect conformation of the metal to the mould may be effected by the
introduction of a suitable compressing tool to the interior of the crown, preferably a
burnishing tool. This mould may be used to contract and contour a blank (Fig. 1)
directly to the form of Fig. 18; but preferably the original blank is first subjected to
contraction by forcing it into the converging hole e, of an ordinary contracting plate
Fig. 14, or by spinning and reducing its aperture upon a sectional mandrel Fig. 15,
the said mandrel being afterwards removed by dropping it out in pieces. This
operation imparts to the blank the preparatory form, Fig. 16, the same having straight
converging sides.
The blank, in case of having a grinding surface already stamped thereon, may, as
illustrated in Fig. 21, be reinforced by gutta percha, lead, or other suitable filling f
prior to the contracting operation for the purpose of sustaining the contour of said
grinding surface.
To facilitate contouring, the sides of the crown may be slit, as at g, Fig. 23, or a
narrow shaped section removed, so as to permit the more ready contraction of the
cervical part, or expansion of the remaining part of the sides, or both, the same being
subsequently soldered.
It will be observed that the curvatures of the mould Fig. 17, are located so as to
produce a concavity of profile upon that portion of the crown ( Fig. 23) known in

page_text: "
dentistry as the "cervical third
a reverse curve at the beginning of the "middle
third" ( Fig. 23); and a convexity of surface from thence to and upon the
"occluding third" (h Fig. 23).
These features are likewise applicable to the plate, Figs. 19 and 20, the same
differing from Fig. 17, in having its cavity e, of a form corresponding more. precisely
to the peculiar irregularities of an original tooth. The same is obtained by reproducing
from the original tooth a facsimile in plaster; the latter being moulded from plaster
impressions taken from the tooth, in the manner hereinbefore described; and using
said fac-simile as a core for casting the plate D, with its converging aperture e; the
said plate being for convenience cast of metal fusible at low temperature.
In the plate D, a metal crown with or without a grinding surface stamped thereon,
or a crown collar, may be contracted and formed in the manner described with
relation to Fig. 17; but furthermore, I may employ in conjunction with the plate D,
a mould C, having a cavity for imparting or altering a grinding surface upon the cap
of the crown, at the time of forming or contouring said crown within the moulds,
by a suitable tool when the moulds are brought together as in Fig. 20. Furthermore,
the mould C, may be constructed with an opening i Fig. 22, through which the
forming tool can be introduced as illustrated, when it is desired to form a crown
collar extending partly over the grinding surface of "occluding third" of the
crown; the collar being designed to have a separate grinding surface soldered
thereon.
The seamless band b, Fig. 31 (having straight sides), may furthermore be contoured
in the form shown in Fig. 32, by "striking up" in a die, Fig. 29, similar to Fig. 5,
but embodying only the contouring moulding surface thereof corresponding to the
"cervical" and the middle third of the tooth; the said mould being adapted so
that the "cervical third" (or end of the band to be enlarged) is uppermost in the
female mould; and may therefore be removed, and the crown blank 61 similarly
"struck up
in an inverted position in another die, Fig. 30, of similar character
adapted therefor; the two parts being subsequently united by soldering as shown in
Fig. 33 and as hereinbefore referred to.
"
The means represented in Figs. 24 to 28 inclusive are employed as follows:-
From the tooth to be crowned an accurate impression is taken by applying to its
surface, a plastic material, such for instance as "plaster of Paris," and afterwards
dividing the same so as to remove it in parts from the tooth without disturbing the
impression therein corresponding to the irregularities of said tooth. This mould
being now placed together, and allowed to harden, is used as a cavity in which
to cast a mandrel of easily fusible alloy, or other material of suitable stability when
hardened.
The mandrel thus produced is now divided into several convenient parts or sections a,
such as are represented by Figs. 4 to 27 inclusive; one of which sections is shown
detached in Fig. 27; or they may be thus separately cast by interposing suitable
partitions in the mould preparatory to casting.
The sections a¹, are held in proper relation when assembled together, by means
of a suitable clamping device, or by the hand, applied to their extended portions or
shanks b³.
Into the cup shaped cap or blank b, Fig. 1, of platinum, gold, or other suitable
thin malleable metal, or component parts b, b¹ of a similar blank, Fig. 2, to be soldered
into one piece, are now introduced the crown ends of the several sections composing
the sectional mandrel; preferably the exterior sections first, and the central one
having parallel or wedging sides last, the exterior of said mandrel being thus expanded
into the blank; or should the tooth be narrow as in the instance of a bicuspid tooth,
the mandrel may be forced into the blank after being assembled, or the mandrel may
be made solid.
The crown is now formed by exterior application of a suitable burnishing tool,
working the metal into the recesses and irregularities peculiar to the surface of the
mandrel, whereby a contoured shape such as represented by Fig. 4, is produced. The
sectional mandrel is after completion of the blank dropped out in pieces; the central

page_text: piece or pieces being removed first, which is obviously necessary in order to avoid
disturbance of the contoured sides of the crown, which converge variously toward its
reduced aperture.
The crown shaping device Fig. 28, consists of a sleeve d, of metal which being bell
mouth shaped at its lower end, will when placed over the mandrel shank 63, and
forced toward the blank b, contract the aperture of the same against the diverging
sides of the mandrel, from the shape shown by dotted lines, approximately into the
contoured shape, facilitating thereby the subsequent operation of burnishing.
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. In the manufacture of artificial metallic tooth crowns, the process of forming or
pressing the same into moulds or cavities between sectional dies having a conformation.
corresponding to that of the natural tooth crown to be replaced, by the application of
pressure substantially as described upon the interior of said metallic crown, while
within said dies.
2. In a contracting plate for contracting the aperture of hollow metallic tooth
crowns, the construction substantially as described of convex and concave curvatures
located as shown in the contracting hole of said plate for the purpose of contouring
said crowns therein, in the manner described.
3. In a contracting plate for contracting the aperture of hollow metallic tooth
crowns, the construction in the manner described, of contouring surfaces in the
contracting hole of said plate, said contouring surfaces having a contour accurately
corresponding to that of a natural tooth crown to be fitted or replaced.
.
4. The combination with a contracting plate for contracting the aperture of
hollow metallic tooth crowns, and having a contoured contracting hole substantially
as described, of a supplemental mould having a contoured cavity for imparting to said
crowns a grinding surface when said crowns are formed therein in the manner
described.
5. The combination with a contracting plate for contracting hollow metallic tooth
crown collars, and having a contoured contracting hole substantially as described, of a
supplemental mould having a cavity contoured at that portion which is employed for
contouring the margins of the grinding surface upon the edge of said collar, said
cavity being open to the exterior of the mould at its central portion for the introduction
of a forming tool in the manner described.
6. A sectional mandrel for forming a hollow metallic tooth crown, said mandrel
having a contour corresponding to that of an original tooth to be fitted or replaced,
and composed of separable sections so divided as to permit the removal of the same,
subsequent to the forming process herein described.
7. In a device for forming metallic tooth crowns, the combination with a sectional
mandrel having diverging acting surfaces as shown, of a compressing sleeve having
corresponding converging acting surfaces for compressing the open end of said
metallic tooth crowns substantially as described, upon said mandrel.
8. As an improved article of manufacture, a seamless metallic tooth crown sub-
stantially as herein described, having the external conformation corresponding to the
cervical, middle and occluding third, of a natural tooth to which said inetallic crown
is to be applied or substituted for.
Dated this 15th day of November 1987