U.S. patent number RE33,099 [Application Number 06/870,427] was granted by the patent office on 1989-10-24 for dental crown, coping and method.
Invention is credited to Itzhak Shoher, Aharon Whiteman.
United States Patent |
RE33,099 |
Shoher , et al. |
October 24, 1989 |
Dental crown, coping and method
Abstract
The dental jacket crown of the present invention is prepared
from a thin metal foil substrate which is coated with a noble based
metal composition having a low fusing temperature and folded in a
predetermined manner to form a multiple number of triangular like
flaps or pleats. The folded foil represents the coping of the
present invention. The coping is mounted over a die of the prepared
tooth and the flaps wrapped in overlapping formation and then
adapted to the die. The die is removed and the structure heated
preferably under a bunsen burner. A veneering material such as
porcelain is then coated over the structure to form the crown.
Inventors: |
Shoher; Itzhak (Tel Aviv,
IL), Whiteman; Aharon (Petach Tikvah, IL) |
Family
ID: |
27022538 |
Appl.
No.: |
06/870,427 |
Filed: |
June 4, 1986 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
414415 |
Sep 2, 1982 |
04459112 |
Jul 10, 1984 |
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Current U.S.
Class: |
433/222.1;
433/218 |
Current CPC
Class: |
A61C
13/0003 (20130101); A61C 5/77 (20170201) |
Current International
Class: |
A61C
5/10 (20060101); A61C 5/08 (20060101); A61C
005/08 () |
Field of
Search: |
;433/222.1,223,218,227,208,207 ;264/19,20 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
"Theory and Practice of Crown and Bridge Prosthesis", by Stanley D.
T. Tylman, 1947, pp. 523-531..
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Primary Examiner: Wilson; John J.
Attorney, Agent or Firm: Lieberstein; E.
Claims
What we claim is:
1. A .[.jacket.]. .Iadd.dental .Iaddend.crown comprising a
composite body .[.including.]. .Iadd.formed from .Iaddend.a thin
foil of high fusing temperature metal having a surface geometry
conforming to a die to which it has been adapted .[.with the foil
having at least a minimum of three folded over pleats with each
pleat forming a triangular like flap in the unfolded position,.]. a
thin coating of a .[.noble.]. .Iadd.gold .Iaddend.based .Iadd.noble
.Iaddend.metal composition superimposed over one surface of said
.[.thin metal foil and disposed beneath the folded over pleats.].
.Iadd.high fusing temperature metal with said composite body having
a plurality of folded over sections which radially extend from an
axis through the center of the foil in a symmetrical arrangement
about the center of the foil .Iaddend.and a relatively thick outer
coating of a dental veneering material.
2. A .[.jacket.]. .Iadd.dental .Iaddend.crown as defined in claim 1
wherein said folded over .[.pleats overlap one another.].
.Iadd.sections constitute pleated sections with each pleated
section represented by fold lines which form a triangular like flap
in the unfolded position.Iaddend..
3. A .[.jacket.]. .Iadd.dental .Iaddend.crown as claimed in claim 2
wherein said thin foil is composed of platinum and wherein said
veneering material is fired on dental porcelain.
4. A .[.jacket.]. .Iadd.dental .Iaddend.crown as claimed in claim 2
wherein said .[.noble.]. .Iadd.gold .Iaddend.based .Iadd.noble
.Iaddend.metal composition comprises at least 50% gold and at least
one of the following elements selected from the group consisting
of: silver, palladium, iridium, copper and aluminum.
5. A .[.jacket.]. .Iadd.dental .Iaddend.crown as claimed in claim 4
wherein the weight of said noble based metal in said jacket crown
is between about 20 to 30 milligrams.
6. A dental coping for a .[.jacket.]. crown restoration comprising
a thin foil of high fusing temperature metal .[.arranged in a
prefolded geometrical configuration having at least a minimum of
three pleated sections with each pleated section represented by
fold lines which form a triangular like flap and a coating of a
noble based metal composition superimposed upon the surface of said
thin foil over said pleated sections.]. .Iadd.having a thin gold
based noble metal composition disposed upon the surface of said
thin foil with said thin foil arranged in a prefolded geometrical
configuration having a plurality of overlapping
sections.Iaddend..
7. A dental coping as defined in claim .[.6.]. .Iadd.20
.Iaddend.wherein each .[.pleated section is of a size such that
upon folding it will overlap an adjacent pleated section.].
.Iadd.section is pleated and represented by fold lines which form a
triangular like flap in the unfolded configuration..Iaddend.
8. A dental coping as defined in claim .[.7.]. .Iadd.6
.Iaddend.wherein said thin foil was circular in shape before
folding.
9. A dental coping as defined in claim 8 wherein said fold lines
radially extend from an unfolded area substantially in the center
of said coping with the unfolding area being small compared to
total area of the foil.
10. A dental coping as defined in claim 9 wherein said thin foil is
composed of platinum.
11. A dental coping as defined in claim 10 further comprising a
plurality of small slotted opening arranged about the periphery of
said coping.
12. A method of forming a dental .[.jacket.]. crown comprising
preparing a thin metal foil of high fusing temperature metal into a
substantially circular substrate;
coating one surface of the foil substrate with a noble based metal
composition having a low fusing temperature of below about
1070.degree. C.;
forming a multiple number of fold lines in said coated foil
substrate with each two adjacent fold lines substantially defining
a triangular like flap;
mounting said coated foil substrate over a die of the prepared
tooth with the coated surface exposed;
partially overlapping each flap about said die in a clockwise or
counterclockwise sequence with the foil tightly wrapped about said
die;
adapting said tightly wrapped foil to said die;
removing said die for providing an inner structure for said jacket
crown;
heating said inner structure above the low fusing temperature of
said noble based metal composition; and
coating a veneering material over said inner structure.
13. A method as claimed in claim 12 further comprising the step of
forming small slotted openings about the periphery of said coated
foil substrate following the folding step.
14. A method as claimed in claim 13 wherein said slotted openings
are formed along the fold lines.
15. A method as claimed in claim 14 wherein said veneering material
is a fired on procelain.
16. A method as claimed in claim 15 wherein said heating step is
performed by placing said inner structure under the flame of a
bunsen burner for between 5 to about 30 seconds. .Iadd.
17. A method of forming a dental coping for a dental crown
comprising the steps of forming a thin foil metal composite of a
high fusing temperature metal and a superimposed low fusing
temperature metal, prefolding said foil to form a plurality of
foldable sections which radially extend from an area in the center
of the foil adapted to be mounted over the occlusal surface of the
tooth to be restored in a symmetrical arrangement with respect to
the center of the foil, folding the sections over, adapting said
composite foil to a die of the tooth to be restored, removing said
composite foil from said die and heating said composite foil to a
temperature above the low fusing metal temperature so as to cause
said low fusing temperature metal to melt for forming a compact
matrix between said high fusing temperature metal layer, the folded
over sections of foil, and the melted gold based low fusing
temperature metal. .Iaddend. .Iadd.18. A method as defined in claim
17 wherein said composite body is heated by subjecting it to the
flame of a bunsen burner or in a furnace at a temperature of about
1020.degree. C. to 1070.degree. C. .Iaddend. .Iadd.19. A method as
defined in claim 18 wherein the folded over sections of said
composite body are folded to overlap one another. .Iaddend.
.Iadd.20. A dental coping as defined in claim 9, wherein said
folded over sections overlap. .Iaddend.
Description
This invention relates to the field of dental restorations and more
particularly to the jacket crown restoration, a jacket crown coping
for a jacket crown restoration and to a method for forming a jacket
crown.
Dental porcelain, a conventional material composed of a mixture of
heldspar, quartz and kaolin is commonly used in fabricating dental
restorations. The most prevalent crown construction for dental
restorations is the porcelain veneer cast metal crown. The cast
metal crown is fabricated using a relatively thick metal
understructure formed from casting an investment of a wax or
plastic pattern of the prepared tooth. Dental porcelain is then
applied in layers over part or all of the understructure and fired
at high temperature to form a veneer. The metal understructure is
preferably formed from a noble based metal or alloy predominantly
of gold. The thickness of the cast metal understurcture ranges from
typically 0.3 to 0.5 mm. The cast metal understructure is expensive
and particularly so for a noble based metal understructure. The
weight of a precious metal cast crown is from one to three grams.
Since the bulk of the restoration is no greater than that of the
tooth structure which originally occupied the space, the use of a
thick metal understructure minimizes the permissible thickness for
the translucent porcelain veneer. Moreover, exposure of the metal
understructure will detract from the esthetics of the
restoration.
It is well known that the full porcelain or porcelain jacket crown
is esthetically superior to all other crown restorations and is
virtually impossible to visually distinguish from a natural tooth.
Accordingly, it should be commonplace but is, in general, indicated
for use only as a full coverage for an anterior tooth where
esthetics is the prime consideration. The limited use of the
porcelain jacket crown is attributable to its present method of
construction with the strength of the jacket crown dependent upon
the strength of the porcelain material composition. Porcelain is
inherently structurally weak and fragile. In addition, the present
day method of construction requires a high degree of proficiency to
establish accurate marginal fit and finish and to avoid poor
seating of the crown occlusally relative to the preparation. An
improper fit at the gingival margin results in a cement line which
readily washes away inviting decay and loosening the crown
attachment.
In the conventional process for preparing a porcelain jacket crown
a platinum foil is swaged about the prepared die of the tooth to
form a mold substrate upon which the porcelain may be fired. The
foil is then removed from the substrate before the crown is
cemented to the tooth preparation. The latter requirement is
considered a principle failing of the conventional porcelain jacket
crown preparation. An improved porcelain jacket crown construction
in which the swaged foil substrate is itself included as an
integral component of the finished porcelain jacket crown is taught
and described in U.S. Pat. No. 4,273,580 issued to the Applicants
herein, the disclosure of which is herein incorporated by
reference. In the latter patent the metal foil substrate forms the
core of the jacket crown. A coating of a predetermined noble based
metal composition is sintered to the foil substrate whichis then
adapted to the die in a manner similar to that in the conventional
preparation of a porcelain jacket crown. Although this jacket crown
construction will exhibit substantially improved physical
properties, its method of construction is still dependent upon the
skill and dexterity of a superior dental technician.
The present invention utilizes an entirely new technique for
constructing a porcelain jacket crown which overcomes all of the
shortcomings of the conventional porcelain jacket crown in
mechanical properties, construction and preparation. In fact the
preformed coping of the present invention is readily adaptable by a
technical novice without any special skills. Use of the preformed
coping in accordance with the presesnt invention simplifies
construction of a porcelain jacket crown and significantly
contributes to uniformity in result without the dependency on the
skill of the dental technician.
The porcelain jacket crown of the present invention may be prepared
more quickly and more accurately relative to conventional methods
of preparation. Moreover, the dental laboratory does not have to
wax, invest, cast or polish the final metal structure as is done in
making a porcelain veneer cast metal crown.
In addition, the present invention may be used with any
conventional tooth margin preparations such as: chamfer, shoulder,
chamfer bevel, shoulder bevel, knife edge and feather edge. The
margin may also be reinforced if desired. The porcelain jacket
crown may also be reinforced if desired. The porcelain jacket crown
prepared in accordance with the present invention will have an
almost invisible metal line at the gingiva. An even further
distinct advantage of the present invention lies in the reduction
in the weight of the metal in a jacket crown of the present
invention which is only 20 to 30 milligrams.
Accordingly, it is the principle object of the present invention to
provide a porcelain jacket crown having a high resistance to
fracture comparable with or even greater than the conventional
porcelain veneer cast metal crown.
Another object of the present invention is to provide a preformed
coping for forming the porcelain jacket crown of the present
invention.
An even further object of the present invention is to provide a
method for constructing a jacket crown.
Further objects and advantages of the present invention will become
apparent from the following detailed description of the invention
when read in conjunction with the accompanying drawings of
which:
FIG. 1 is an enlarged perspective of a segment of the preferred
metal foil starting material of the present invention in its
preferred circular geometry;
FIG. 2 is a perspective of a dental coping prepared in accordance
with the present invention from the metal foil starting material of
FIG. 1;
FIG. 3 is a transparency in perspective of the dental coping of
FIG. 2 in the initial stage of being molded to a die of the
prepared tooth;
FIG. 4 is another transparency in perspective of the dental coping
in FIG. 3 in its final stages of being adapted to the die of the
prepared tooth; and
FIG. 5 is an illustration in perspective of the dental coping of
FIG. 3 as a standing structure after having been adapted to the
die.
Referring now to FIG. 1 in which a metal foil segment 10 is shown
representing the starting material for preparing the jacket crown
in accordance with the present invention. The metal foil segment 10
is preferably circular in geometry and composed of a thin foil
metal substrate 12 of platinum or another high fusing temperature
metal and a thin coated layer 14 superimposed on the foil metal
substrate 12. The coated layer 14 should be of a noble metal based
composition preferably with gold as its major constituent. There
are numerous gold based compositions shown to those skilled in the
dental arts for use in the preparation of a dental restoration and
upon which a veneering material such as porcelain may be fired. The
preferred composition of the coated layer 14 should have a
relatively low melting temperature characteristic and contain at
least 50% gold with one or more of the following elements in
combination: silver, palladium, platimum, iridium, copper and
aluminum. A conventional binder may be added to the composition so
that it may spread more readily over the platinum foil substrate 12
to form the coated layer 14. The coated layer 14 should form a
bonded matrix with or without the application of heat which has the
physical properties of being flexible, malleable and spongy. The
gold based composition should have a low temperature fusing
characteristic such that it flows after sufficient heat is applied
for reasons which will be explained in greater detail
hereafter.
The thickness of the platinum foil substrate 12 should be in the
range of between 15 to 50 microns with an optimum thickness of 25
to 27 microns. The thickness of the gold based layer 14 should be
between 10 to 50 microns and preferably between 20 to 25
microns.
The metal foil segment 10 is preferably round although any geometry
may be used in which multiple folds may be made which will
partially overlap one another when adapted to a die as hereinafter
explained. When the metal foil segment 10 is circular its diameter
for a typical die is between about 22 to 28 mm.
The metal foil segment 10 of FIG. 1 is folded into a predetermined
geometrical shape having a multiple number of fold lines 18 as
shown in FIG. 2 for forming the dental coping 16 of the present
invention. The multiple fold lines 18 may be formed by hand or by
machine. The technique or mechanism employed to perform the folding
operation is not critical to the present invention. It is the
arrangement of multiple fold lines in a predetermined array to form
multiple flaps or pleats which forms the underlying theory in the
preparation of a jacket crown in accordance with the present
invention.
An example of a hand folding operation that may be used for forming
a preferred arrangement of fold lines 18 from the metal foil
segment 10 involves placing the metal foil segment 10 over one end
of a cylindrical support bar (not shown) and squeezing the segment
10 into fold lines 18 using the thumb and forefinger of one hand
while holding the segment 10 in place over the support bar. In such
case each fold line 18 will radially extend from a central unfolded
area 20. The central unfolded area 20 will conform in dimension to
the support bar upon which it was placed in forming the fold lines
18. The diameter of the unfolded area is not significant provided
it is small relative to the total area of the segment 10.
Another hand folding operation simply involves folding the segment
10 in half and then in quarters until the desired number of fold
lines 18 are formed. This is a somewhat less desirable procedure
since the fold lines will extend radially from a central point or
apex without forming an unfolded area 20 in the center of the
segment 10. It should however be understood that forming an
unfolded area 20 is not critical to the invention.
The fold lines 18 form substantially triangular like flaps or
pleats 22 with a curved base line 24 shown as a straight line in
FIGS. 2 and 3 for simplicity. Each triangular angular like flap 22
has two fold lines 18 with a common fold line 18 between adjacent
pairs. The number of flaps 22 that should be formed may vary with
four to sixteen being preferred and with eight being the optimum
number for most typical jacket crown preparations.
The preferred geometry of the dental coping 16 includes a multiple
number of fold lines 18 which radially extend from a centrally
located unfolded area 20 in an arrangement which form
triangular-like flaps 22. The dental coping 16 should preferably be
modified to include a plurality of small slotted openings 26. These
openings 26 may be made as an integral part of the manufacturing
operation of the dental coping 16 or as part of the procedure of
the dental technician in the preparation of the jacket crown as
will hereinafter be explained in greater detail. The slotted
openings 26 are slits formed in the segment 10 preferably along the
fold lines 18. Neither the position of the slotted openings 26,
their size or number are critical. Their primary function is to
provide access for the noble metal composition to flow to the
underside or uncoated surface of the platinum foil substrate 12
when heat is applied to the finished coping 16 during the final
preparatory step in the preparation of a jacket crown.
FIGS. 3-6 illustrate the preferred sequence of steps in the
preparation of a jacket crown in accordance with the present
invention. The preformed coping 16 is placed over a die 28 of a
prepared tooth with the unfolded area 20 seated upon the top or
occlusal end 29 of the die 28. The die 28 is conventionally
prepared from an impression of the prepared tooth and is a replica
thereof. The unfolded area 20 facilitates centering the dental
coping 16 over the die 28 and makes the coping 16 easier to adapt
to the die 28 as is more readily apparent from FIG. 4.
Each of the flaps 22 are wrapped tightly around the die 28 in a
uniform clockwise or counter clockwise oriented sequence resulting
in an arrangement of overlapping flaps 22 as shown in FIG. 4. The
coping 16 should also extend over the gingival margin 31. The die
28 and coping 16 is then placed in a swaging device (not shown) or
pressure is applied by hand to adapt it to the die 28. The coping
16 is then removed from the die leaving a free standing structure
33 as shown in FIG. 5. Heat is then applied to the free standing
structure 33 by placing it over the flame of a bunsen burner for
between five to thirty seconds based on flame temperature until the
structure 33 gets cherry red and shiny. Alternatively the free
standing structure 33 can be placed in a furnace and sintered at a
temperature of about 1020.degree. to 1070.degree. C. until the same
result is achieved. The low fusing preferably gold based
composition of the metal layer 14 will flow through the slotted
openings 26 to form a compact matrix between the foil substrate 12
and the gold based composition on the undesirable thereof without
any air pockets.
After the heating step, porcelain can be directly applied in a
conventional manner to form the jacket crown of the invention. It
is however desirable but not essential, to coat the outside surface
of the free standing foil structure 33 using a bonding composition
to achieve an unbreakable bond between the porcelain layers and the
foil structure 33. A preferred bonding composition is disclosed in
a copending U.S. patent application Ser. No. 171,255 entitled
Bonding Material and Method For Bonding A Ceramic To A Nobel Based
Metal, and now abandoned, the disclosure of which is herein
incorporated by reference. The bonding material disclosed in this
application includes a nobel based metal composition in combination
with a halide of a noble metal preferably a noble metal halide. The
bonding material must be sintered to the foil structure 33 at a
temperature above 1600.degree. F. This can be achieved
simultaneously with the firing of the required porcelain outer
layers. Any number of porcelain layers may be applied and fired for
forming the jacket crown of the invention. Generally, three or more
layers of varying dental porcelain composition starting with an
opaque layer are built up and fired at temperatures in a range from
about 1600.degree. to 1820.degree. F. Before firing the final glaze
the area below the gingival margin is cut and the porcelain shaped
and finished to the correct gingival margin for the prepared
tooth.
After the final glaze the crown is ready to be inserted into the
mouth and cemented to the tooth using any conventional dental
cement composition. It is suggested practice to roughen the
interior of the crown i.e. the unerside of the inner substrate
layer 12 before the crown is cemented to the tooth. The roughness
maybe achieved by sand blasting.
Although the invention was described in connection with the
application of porcelain for forming a porcelain jacket crown it is
equally applicable to the use of any polymer veneering material
such as conventional dental acrylics in substitution of the
porcelain ceramic material for the superstructure of the jacket
crown.
* * * * *