U.S. patent application number 10/823278 was filed with the patent office on 2005-07-28 for method for the production of an oxide ceramic shaped part and a part produced by such method.
This patent application is currently assigned to Ivoclar Vivadent AG. Invention is credited to Holand, Wolfram, Rheinberger, Volker, Rothbrust, Frank, Van t'Hoen, Christian.
Application Number | 20050164045 10/823278 |
Document ID | / |
Family ID | 34638758 |
Filed Date | 2005-07-28 |
United States Patent
Application |
20050164045 |
Kind Code |
A1 |
Rothbrust, Frank ; et
al. |
July 28, 2005 |
Method for the production of an oxide ceramic shaped part and a
part produced by such method
Abstract
A method for producing an oxide ceramic shaped part includes
pressing a powder provided with a binding material or a powder
mixture of an oxide ceramic into a shaped part, pre-sintering the
shaped part at substantially atmospheric pressure and a temperature
of 600 to 1,300.degree. C., and evacuating a closed container in
which the pre-sintered shaped part is disposed with the shaped part
having a maximum density of 10 to 90%. The container is at an
absolute pressure of less than 40 mbar. Subsequently, an
infiltration material is applied onto the shaped part via
infiltration with the infiltration material operating to seal off
the shaped part relative to the surrounding atmosphere. The length
of time of the infiltration is preferably 1 to 10 minutes.
Inventors: |
Rothbrust, Frank; (Frastanz,
AT) ; Van t'Hoen, Christian; (Feldkirch, AT) ;
Holand, Wolfram; (Schaan, LI) ; Rheinberger,
Volker; (Vaduz, LI) |
Correspondence
Address: |
John C. Thompson
69 Grayton Road
Tonawanda
NY
14150
US
|
Assignee: |
Ivoclar Vivadent AG
|
Family ID: |
34638758 |
Appl. No.: |
10/823278 |
Filed: |
April 13, 2004 |
Current U.S.
Class: |
428/701 ;
264/101; 264/102; 264/109; 264/643; 264/666 |
Current CPC
Class: |
C04B 35/481 20130101;
Y10T 29/49568 20150115; C04B 35/488 20130101 |
Class at
Publication: |
428/701 ;
264/101; 264/102; 264/109; 264/643; 264/666 |
International
Class: |
B32B 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 2004 |
DE |
10 2004 004 059.1 |
Claims
What is claimed is:
1. A method for producing an oxide ceramic shaped part, comprising:
pressing a selected one of a powder provided with a binding
material and a powder mixture of an oxide ceramic into a shaped
part; following the pressing of the selected one of the powder and
the powder mixture into the shaped part, pre-sintering the shaped
part at substantially atmospheric pressure and a temperature of 600
to 1,300.degree. C.; following the pre-sintering of the shaped
part, evacuating a container and, in particular, a closed
container, in which the pre-sintered shaped part is disposed with
the shaped part having a maximum density of 10 to 90%, and the
container being at an absolute pressure of less than 40 mbar and,
in particular, at between 10 to 30 mbar; and following the
evacuation of the container, applying an infiltration material onto
the shaped part via infiltration, the infiltration material
operating to seal off the shaped part relative to the surrounding
atmosphere and the length of time of the infiltration being,
preferably, 1 to 10 minutes.
2. A method according to claim 1, wherein the organic binding
material is an ethylene wax, a polyvinyl resin, a polyvinyl
pyrrolidone, a polyvinyl acetate, a polyvinyl butyral and/or
cellulose.
3. A method according to claim 1, wherein the further material is
formed from a precursor of a non-metallic, inorganic phase or an
amorphous glass phase and a solvent, or a connection with a
hydrolyzable element of a metal, or an alcoholate of a metal chosen
from the group Al, Ti, Zr, and Si, or a precursor of a silicate
glass, especially a hydrolyzable silane.
4. A method according to claim 1, wherein, after the infiltration,
a further shaping of the shaped part is effected via a material
reduction working and/or etching.
5. A method according to claim 1, wherein, after the infiltration,
the shaped part is finish sintered to a theoretical density of
99.5% at a temperature from 1,300 to 1,550.degree. C.
6. A method according to claim 1, and further comprising, after a
selected one of the infiltration and a finish sintering of the
shaped part under environmental pressure, shaping the exterior of
the shaped part via at least one of a material reduction working
and etching.
7. A method according to claim 1, wherein the outer surface of the
shaped part is at least sectionally coated with at least one
coating of a mixture material that, in particular, is effected
after the application of a further thermal treatment.
8. A method according to claim 1, wherein an adhesive is applied at
least partially onto the outer surface of the shaped part and a
further material is secured to the part.
9. A method according to claim 1, and further comprising, following
the partial sintering of the part, shaping the shaped part via a
material reduction working with an excess of 10 to 50% and,
preferably, with an excess of 15 to 30%.
10. An oxide ceramic part, comprising a core or a region of a
crystalline oxide ceramic phase and a coating at least partially
enclosing the core or a region thereof, which is formed from the
crystalline oxide ceramic phase and a non-metallic, inorganic phase
(infiltration phase) following the crystalline oxide ceramic
phase.
11. A shaped part according to claim 10, wherein the crystalline
oxide ceramic phase is formed substantially of oxides or oxide
mixtures of the elements zirconium, aluminum, or titanium, in
particular, from a zirconium oxide mixture ceramic of zirconium
oxide and mixtures of metal oxides, the metal oxides of oxides of
the Groups IIIa, IIIb, and IVb of the periodic table of elements,
in particular, from oxides of the metals Hf, Y, Al, Ce, Sc, Er,
and/or Ti.
12. A shaped part according to claim 10, wherein the crystalline
oxide ceramic phase is substantially formed of an in particular
doped zirconium oxide ceramic of zirconium oxide with an additive
of yttrium oxide, preferably in the range of 0.1 to 10 mole %.
13. A shaped part according to claim 10, wherein the crystalline
oxide ceramic phase is substantially formed of zirconium oxide
ceramic with an additive of yttrium oxide, in the range of 2 to 4
mole %, and, in particular, in the range of 2 to 10 mole % and/or
an additive of cerium oxide, preferably in the range of 2.5 to 15
mole % and/or an additive of erbium oxide, preferably in the range
of 2.5 to 5 mole % and/or an additive of scandium oxide, preferably
in the range of 2.5 to 5 mole % and/or an additive of titanium
dioxide, preferably in the range of 0.1 to 15 mole %.
14. A shaped part according to claim 10, wherein the crystalline
oxide ceramic phase is substantially comprised of an aluminum oxide
mix ceramic formed of aluminum oxide and a mixture of metal oxide
and/or predominately zirconium oxide.
15. A shaped part according to claim 10, wherein a core or a region
of a crystalline oxide ceramic phase with a theoretical density
>99.5% and a biaxial strength of not less than 800 MPa and a
fracture strength of more than 6.5 MPa m.sup.1/2 is effected.
16. A shaped part according to claim 10, wherein at least a portion
of the core is covered by a coating of an amorphous silicate phase
SiO.sub.2, a crystalline silicate phase, or a non-metallic,
inorganic phase, whereby the crystalline silicate phase is
comprised of SiO.sub.2 and other metal oxides, especially oxides of
the metals of the Groups Ia, Ib, IIa, IIb, IIIa, IIIb, IVa, IVb,
and in particular oxides of Al and Ce.
17. A shaped part according to claim 10, wherein the coating which
at least partially encloses the core is a crystalline phase and,
especially, is micro crystalline ZrO.sub.2.
18. A shaped part according to claim 10, wherein the thickness of
the coating that at least partially encloses the core is, at a
maximum, 90% of the thickness of the finish sintered part,
especially 2 to 30% of such thickness.
19. A shaped part according to claim 10, wherein the coating is at
least partially comprised of the crystalline oxide ceramic phase
and that, especially, the chemical resistance of this coating to
acid is substantially less than that of the crystalline oxide
ceramic phase in the core.
20. A shaped part according to claim 10, wherein the infiltration
phase coating comprises a greater translucence than the core or the
region comprised of the crystalline oxide ceramic phase.
21. A shaped part according to claim 10, wherein the finish
sintered part, in the region of its outer surface, comprises a
retentive design formed after an etching step in the region of the
coating that covers the core, whereby the etching depth is, in
particular, at a maximum equal to the thickness of the coating
covering the core.
22. A shaped part according to claim 10, wherein the shaped part is
configured as a selected one of a dental root post in the form of a
bracket or abutment, a dental implant, a three section bridge, a
multi-section bridge, a frame for a bridge, an alluvial material
shaped part, a crown, a partial crown, a partial component of an
inlay, a partial component of an onlay, a cap, a reduced crown, a
synthetic joint, an orthopedic implant, and a shaped part of an
orthopedic implant.
23. A shaped part according to claim 10, wherein the shaped part
comprises an at least single coated coating formed of a mixture
material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims foreign priority benefits under 35
U.S.C. .sctn.119 from German patent application Ser. No. 10 2004
004 059.1 filed Jan. 27, 2004.
TECHNICAL FIELD
[0002] The present invention relates to a method for producing an
oxide ceramic shaped part, as well as to an oxide ceramic shaped
part.
BACKGROUND OF THE INVENTION
[0003] Methods for the production of an oxide ceramic shaped part
have been known for a long time. For example, it is known from WO
95/35070 to produce a ceramic shaped part. In this approach, the
ceramic is infiltrated. The production of an oxide ceramic shaped
part of this type is, however, relatively time-consuming; the step
alone of the infiltration that is undertaken in connection with
this approach, requires, for example, 4 hours.
[0004] Furthermore, it is known from EP-A 1 834 366 to produce a
ceramic piece that is produced via the infiltration of a melted
matrix material into the hollow space of a blank. A particular
particle size with two different size gradations is provided for
the infiltration substance. In connection with this approach, a
covering material is used that is provided with a soluble salt that
must be removed after the infiltration and the solidification step.
The disadvantage of this approach is the need for the high process
temperature during the shaping and the complicated
hardware-intensive production.
[0005] The publication WO 88/02742 discloses the production of a
ceramic component having a hardened outer surface. A porous
AlO.sub.2 blank is infiltrated with a zirconium oxide infiltration
material so that the finished ceramic work piece comprises a volume
portion of 1 to 15% zirconium oxide and, thus, the so-formed
aluminum oxide ceramic is solidified. This process requires several
infiltration steps and is suitable if a relatively soft ceramic
such as aluminum oxide is to be hardened, while it is to be
understood that a zirconium oxide ceramic with a high critical
stress intensifying factor cannot be further hardened or
strengthened via the addition of zirconium oxide. A ceramic of this
type exhibits a strengthening only on its outer surface and, to
produce a suitable work piece via this approach, the process steps
must frequently be implemented in a serial manner.
[0006] Furthermore, DE-A1 198 52 740 discloses the configuration of
a cap, or the configuration of other dental pieces, of aluminum
oxide ceramic. The pre-sintered shaped part is infiltrated in the
heated condition with a glass, which melts upon the introduction of
the shaped part into the sintering oven. The infiltration requires,
in connection with this approach, a timeframe of approximately 4
hours and a high press temperature. On top of this, the process is
decidedly difficult to control and the mechanical properties of the
dental piece are correspondingly poor.
[0007] Additionally, DE-A1 100 61 630 discloses the production of a
full ceramic dental restoration piece comprised of a dental ceramic
of zirconium oxide and aluminum oxide, whereby an infiltration with
glass in a volume range of 0 to 40% is undertaken. This approach
additionally requires, in connection with the deployment of such a
dental restoration piece, the use of a mixture ceramic. A
disadvantage of this approach is the reduced securement properties
of the ceramic, which has been solidified via the glass phase.
[0008] Moreover, EP-A1 1 025 829 discloses the production of a cap
of a ceramic material infiltrated with glass. In order to provide
the desired translucence, two additional coatings are provided,
which are applied onto the cap. In connection with the preparation
of the dental restoration pieces, it is, due to aesthetic reasons,
critical that the natural dental enamel be simulated, such natural
dental enamel having an increased translucence while the dentine
has a reduced translucence. In this connection, the coatings 7 and
6 are provided in accordance with the disclosed approach. In a
process of this type, the detailed further working involving the
grinding of the infiltrated fixed body into a powder is
disadvantageous, but, additionally, the reduced securement property
of the ceramic solidified via the glass phase is also
disadvantageous.
[0009] DE-A1 101 07 451 discloses a process for the production of
an oxide ceramic shaped part that is formed from a zirconium or
aluminum oxide ceramic via milling with a large CAD/CAM technology
system after pre-sintering. Thereafter, the milled blank is
sintered under no pressure at 1200 to 1650.degree. C. The thus
produced oxide ceramic phase exhibits a reduced translucence as
compared to a high-temperature isostatically pressed ceramic, the
mechanical properties are worse than those of a high-temperature
pressed ceramic, and such ceramics are difficult to etch.
[0010] CH-A5 675 120 discloses zirconium oxide mixture ceramics,
which comprise 7 to 12% by weight PiO.sub.2 and other grain growth
limiting and stabilization suitable additives. These can also
comprise 0 to 30% by weight Al.sub.2O.sub.3. The powder mixture is
sintered at a temperature from 1100 to 1300.degree. C. The
disadvantage of this ceramic is that the achievable thickness lies
at only 98% of the theoretical thickness (TD) and, consequently, is
less than that of a high-temperature pressed ceramic. The
production of a retentive design on the outer surface is, with this
ceramic, possible only with difficulty.
[0011] Additionally, the publication "Hei.beta.isostatisches
Pressen" from D. W. Hofer (Hei.beta.isostatisches Pressen, in:
Technische Keramische Werkstoffe, Fachverlag Deutscher
Wirtschaftsdienst, Hrsg. Kriegesmann J., Kap. 3.6.3.0, pp. 1-15.
January 1993) discloses that work pieces can be produced via
high-temperature pressed processes in which the structures thereof
scarcely exhibit any defect locations and the thicknesses of which
are nearly those of the theoretically possible values. In order to
achieve these properties, however, a pressure of between 30 to 200
MPa is required for the sintering temperatures. Moreover, an inert
gas atmosphere follows the step of the pressure treatment.
Correspondingly, this technique and the attendant
hardware-intensive work require considerable effort and outlay.
This process is thus disadvantageous in that it is costly and
involves complicated processing technologies and their attendant
high capital and energy costs so that, for example in connection
with small enterprises, such as dental laboratories, it is not
possible for such enterprises themselves to perform this
process.
OBJECTS AND SUMMARY OF THE INVENTION
[0012] In contrast, the present invention offers a solution to the
challenge of providing a method for the production of an oxide
ceramic shaped part as well as an oxide ceramic shaped part itself,
that is more suitable for the realization of a dental restoration
piece and that permits a cost-optimized production with a
simultaneously improved aesthetic appearance without degrading the
use properties of the thus-produced shaped part and offering,
especially, the possibility to produce a retentive design and to
ensure the securement of the shaped part on the natural tooth.
[0013] Surprisingly, the inventive configuration of an infiltration
coating or covering on the relevant regions of the oxide ceramic
part permits the realization of an increased securement of the
entire oxide ceramic part. Evidently, the covering, or the at least
partial covering of the oxide ceramic part with the coating
imparted by the infiltration, stabilizes the oxide ceramic shaped
part to such an extent that a clearly improved fracture strength
approaching 6.5 MPa m.sup.1/2 can be achieved.
[0014] In a surprising manner, the inventive solution also leads to
an improvement of the aesthetic appearance of a dental restoration
piece if the inventive oxide ceramic shaped part is used as the
dental restoration piece. The infiltration coating has a higher
translucence while the infiltration-free inner region or core of
the oxide ceramic has a reduced translucence and, in connection
with the realization of a zirconium oxide ceramic, the coating is
practically white. This simulates the human tooth in a surprisingly
simple manner and is achieved without any need to deploy mixture
ceramics, if such is desired.
[0015] Due to the possible or optional omission of an additional
mixed ceramic, the therewith connected problems also drop out such
as the longer process time, the securement problems, and the
required coating thickness of the mixture ceramic. In contrast, the
inventive solution is suitable for the realization of small-scale
or closely-spaced members, yet nonetheless aesthetically very
attractive, dental restoration pieces. In particular, if the
infiltration coating comprises a silicate phase, this can, for
example, be etched away with HF and an adhesive binding with other
work pieces can be realized.
[0016] The inventive solution permits, in a surprisingly simple
manner, the achievement of the same securement properties that can
be achieved with hot isostatic presses, whereby the time consuming
hot-press process can be avoided. The biaxial securement property
is, in connection with one embodiment of an oxide ceramic
connection part, not less than 800 MPa. The fracture mechanism
properties of the pure crystalline oxide ceramic phase are
approximately 6.95 MPa m.sup.1/2, as determined in accordance with
the Indenter process and calculations in accordance with Evans
& Charles critical tension intensification factors IIC and, in
fact, lie comparatively higher than even those of corresponding
high-temperature pressed ceramics. It is surprising in this
connection that the properties of the hot-pressed materials, even
those with predominantly tetragonal zirconium oxide as the
crystalline oxide ceramic phase, have been duplicated. Preferably,
the thickness of the inventive infiltration coating is between 2 to
30%; in an advantageous configuration between 5 and 20%; and, for
practical purposes, between approximately 10 to 15%, each
respective selected thickness being a function of the respective
largest diameter of the oxide ceramic part.
[0017] The coating that at least partially covers the core formed
of a non-metallic, inorganic phase is relatively less resistant to
acids than the pure crystalline oxide ceramics in the core. The
coating can thereby be easily etched. The chemical resistance is,
however, not substantially less than that of the core, if the
covering coating comprises only micro-crystal zirconium oxide.
[0018] Due to the reduced chemical resistance of the coating that
at least partially covers the core, a retentive design can be
achieved there at via etching. The depth of this retentive design
can be determined via the etching means, its concentration and the
application time during the etching process. This depth corresponds
in an inventive manner to, at the most, the thickness of the
covering coating, as the core is substantially more resistant to
chemical attacks than the covering coating.
[0019] In the realization of the inventive process, a pre-sintering
to achieve 50% of the theoretical thickness in atmospheric air is
undertaken at no pressure following the pressing of the oxide
ceramic blank. In the realization of the inventive process, a
powder or a powder mixture is provided as the outlet material,
which is formed out of the corresponding oxide ceramic or mixture
ceramic. The powder is preferably in the form of a granulate and is
mixed with a binding material. Preferably, the binding material can
be comprised of ethylene wax material, polyvinyl alcohol, polyvinyl
pyrrolidone, polyvinyl acetate, polyvinyl butyral, or
cellulose.
[0020] The pre-sintering temperature amounts to clearly less than
the sintering temperature and can lie, for example, between 600 and
1300.degree. C. and, preferably, between 1000 and 1200.degree.
C.
[0021] To achieve the inventive solution, it is advantageous to
evacuate the partially sintered part. In this connection, in
accordance with the invention, less than 50 mbar, such as, for
example, 20 mbar, is preferred. The low pressure is applied, for
example, for 1 minute up to 4 hours such that a pressure
equalization in the sense of the formation of a vacuum in the
interior of the partially sintered oxide ceramic shaped part is
formed. In connection with this evacuation, the gases are removed
from the porous, partially sintered in-process part body. During
this time, the inventive sol. to be deployed for preparing the
further materials that are to be formed, is mixed. In a
conventional manner, the formation of these further materials is
undertaken following the evacuation in a low pressure
atmosphere.
[0022] It is particularly advantageous, in connection with the
inventive method, that the penetration of a precursor of a
non-metallic, inorganic phase has shown its worth, such precursor
comprising, for example, a precursor of a vitreous-amorphous phase
and a solvent.
[0023] In accordance with the present invention, it is particularly
advantageous if the infiltration material is available as a sol.
and is further reacted into a gel. These are preferably precursor
products of a glass or ceramic material. Via the low pressure, the
mixed sol. is suctioned into the low pressure chamber and there
follows a penetration over an inventive, decidedly short time, such
as, for example, preferably, 1 minute. In this manner, there is
achieved an infiltration coating with the desired coating
thickness, which permits the setting or adjustment thereof via the
infiltration time, the viscosity of the solution, but as well, the
porosity of the partially-sintered ceramic part.
[0024] Surprisingly, the formation of the infiltration coating in a
simple manner permits the realization of a decidedly uniform
coating. Due to the short infiltration time, the infiltration fluid
only has time for the outer surface of the in-process part body to
be covered. Via aeration of the low pressure chamber, the
infiltration material is practically suctioned in. It is to be
understood that the viscosity of the preferably gel-formed
infiltration material substantially influences the penetration
depth. A reduced viscosity produces, due to the reason of the
capillary working of the pores of the in-process part body, a large
coating thickness of the infiltration coating, while a high
viscosity reduces the penetration depth. Preferably, the coating
thickness amounts to approximately 0.5 mm. In a modified
embodiment, the coating thickness of the infiltration coating is
approximately 1.5 mm, which corresponds to the coating thickness of
the dental enamel, but this coating thickness can be adjusted to
more or less, as well.
[0025] Immediately after this step, there follows an aeration of
the low pressure chamber and the solidification of the applied
solution into a gel is undertaken via heating at the pre-selected
sintering temperature in an ambient atmosphere. The sintering
temperature is, for example, 1300 to 1550.degree. C. and the
sintering follows under an ambient pressure at an ambient
atmosphere. Via the inventive process, the sintering properties of
the pure crystalline oxide ceramic phase are improved while, via a
covering coating formed from a non-metallic, inorganic phase of the
previously evacuated, partially-sintered shaped part, the
penetration of gases into the porous structure of the
partially-sintered part is prevented, whereby a complete dense
sintering of the ceramic is achieved.
[0026] The inventive oxide ceramic shaped part can be pre-pressed
in a desired form. It is also, however, possible to undertake a
milling or another type of cutting or machining in order to produce
a shaped part from the ceramic in-process part body and, in fact,
to accomplish such, either after the pre-sintering or after the
sintering. With respect to such an undertaking after the
pre-sintering, the advantage is gained that the shaping is possible
in a relatively easy manner in that the final hardness has not yet
been reached. In contrast, in connection with such an undertaking
after the sintering, a very hard work piece such as a
diamond-cutting disc must be used whereby, to be sure, the shape
integrity is not degraded by a further shrinking process.
[0027] In accordance with the present invention, an oxide ceramic
shaped part with a theoretical thickness of 99.9% is produced via,
for example, sintering at 1480.degree. C., whereby it is
advantageous that, during the sintering in an ambient atmosphere,
the shaped part is worked so that the shrinkage factor is less than
that of a high-temperature isostatic press process.
[0028] The inventive process permits the preparation of a
substantially tetragonal phase with reduced cubical phase
components, provided that a sintering temperature of 1500.degree.
C. is not exceeded. In accordance with the present invention, in a
surprising manner, a translucence profile is realized that
heretofore could only be realized via a hot-press process.
Additionally, in contrast to a hot-press ceramic, the advantage is
obtained that an adhesion via etching on the infiltration coating
is possible without further effort.
[0029] The present invention is particularly advantageous in
connection with zirconium oxide ceramic or mixture ceramics having
a high zirconium oxide portion, whereby, as well, suitable
doping--such as with yttrium--and mixing--in can be advantageous.
In connection with such hard ceramics, the bending strength in the
core is high, the fracture strength, in contrast, is particularly
good in the infiltration coating, which is formed from the
crystalline oxide ceramic phase and the infiltration phase that
penetrates the crystalline oxide ceramic phase--also called
infiltration.
[0030] The thus-produced inventive oxide ceramic composite shaped
part comprises, consequently, in its pure crystalline oxide ceramic
core, the optical and mechanical properties which even equal the
values of those properties in the high-temperature isostatic
pressed materials. The properties of the pure crystalline oxide
ceramic phase are, evidently, realized by the reason of the
thickness of the structure.
[0031] In one embodiment, following the finish sintering, there is
effected, to inventively produce an oxide ceramic composite shaped
part, a process in which a material reduction working occurs that
is, preferably, performed by CAD/CAM technology. In this
connection, the covering coating is completely or partially reduced
away and the translucent core comes to the outer surface. In this
manner, the final shaping of the oxide ceramic composite shaped
part can subsequently occur. If the covering coating remains in a
partially covering manner on the outer surface, this can be removed
in a following step via etching.
[0032] A retentive design can be maintained in the regions where
the outer coating still remains. At the same time, a thick,
translucent structure appears on those portions of the outer
surface at which the coating has been removed. In this manner,
there is produced, in a surprisingly simple manner, an aesthetic
appearance that corresponds to that produced in connection with
comparable hot isostatic press work pieces. Due to the high density
of the structure, a high light transmission capability
(translucence) is achieved that corresponds to that of hot
isostatic pressed ceramic.
[0033] To configure a dental restoration piece, a single coat
mixture is subsequently applied in order to produce an even more
improved aesthetic appearance. In the regions in which a retentive
design was produced, the use of suitable desired adhesive systems
is possible. Preferably, an adhesive system is deployed. In
accordance with the present invention, an adhesive securement is
possible in a surprisingly simple manner which is not possible with
respect to corresponding hot isostatic pressed work pieces. In
connection with the securement materials, chemical,
light-hardenable, or dual hardenable material are preferred.
Cementing materials are, for example, zinc phosphates. The
inventive oxide ceramic composite shaped part offers, in this
manner, an improved adhesive procurement possibility with the same
aesthetic appearance as hot isostatic pressed, comparable
materials. Moreover, the sintering process is substantially simpler
and is, consequently, in contrast to the hot isostatic press
process, considerably more cost favorable.
[0034] The inventive solution permits a plurality of oxide ceramic
parts to be produced. In this connection, dental restoration pieces
are produced such as inlays, onlays, crowns, partial crowns,
veneers, facets, bridges, caps, brackets and abutments, but also
alluvial materials, and alluvial material components and
frameworks.
[0035] Also, it is basically possible to exploit the advantages of
the inventive process in connection with other deployed ceramic
pieces such as, for example, the preparation of synthetic joints,
whereby the outer surface infiltration coating offers favorable
properties in view of the reduced abrasion with, at the same time,
good hardness and a glass-hard outer surface; however, surgical
implants or components thereof are equally amenable to such
preparation. Also, endodontic parts such as root posts can be
produced by the inventive process whereby the good adhesion on
other parts can be exploited.
[0036] The length of time of the production of an inventive ceramic
blank is strongly dependent upon the length of time required for
the desiccation--that is, the creation of the low pressure
environment. The preparation of the infiltration material requires,
in connection with one advantageous embodiment of the invention, a
not inconsiderable mixing time and standing time. The determination
of the time frame can, however, be favorably influenced by the
mixing of the infiltration material already before the process has
begun--that is, for example, while the blank is pressed or, at the
latest, during the pre-sintering, so that this mixing time does not
add onto the cycle time for the preparation of a finished oxide
ceramic part.
[0037] The pure infiltration time can, for example, amount to 1 or
2 minutes and can last, in any event, typically less than 10
minutes while the finish infiltration occurs in accordance with the
respective selected temperature curve of, for example, 30 to 60
minutes.
[0038] Further advantages, details, and features are described in
the hereinafter following descriptions of several embodiments of
the present invention with reference to the drawings.
BRIEF DESCRIPTION OF THE FIGURES
[0039] FIG. 1 is a schematic perspective view of an arrangement for
performing the inventive infiltration method for preparing an
infiltration coating on an oxide ceramic part;
[0040] FIG. 2 is a graphical view of the infiltration coating
thickness versus the infiltration time;
[0041] FIG. 3 is a schematic perspective view of a sintering oven
for use in connection with the inventive infiltration method for
preparing an infiltration coating on an oxide ceramic part;
[0042] FIG. 4 is a flow chart of the steps of one implementation of
the method of the present invention; and
[0043] FIG. 5 is a flow chart of the steps of another
implementation of the method of the present invention.
DETAILED DESCRIPTION
[0044] FIG. 1 schematically illustrates an arrangement for
performing the inventive infiltration method for preparing an
infiltration coating on an oxide ceramic part. The blank 10, which
subsequently forms the oxide ceramic part, is pre-sintered and is
disposed in a beaker 12. The beaker 12 is disposed in a desiccator
14 on whose cover a drip funnel 16 is mounted.
[0045] Moreover, the desiccator comprises, in a conventional
manner, a low-pressure connection hose 18 that is connected with a
low-pressure pump. In a conventional manner, the polished sealing
edge 20 of the desiccator closes upon the creation of a low
pressure environment in the desiccator and can be opened after the
venting of the desiccator. The drip funnel does not have a pressure
compensation but is, however, provided with a stopcock 22 that
permits a fine adjustment of the drip rate.
[0046] The infiltration is effected in a manner such that a
prepared brine 22 is introduced as the infiltration material into
the drip funnel 16, after which the desiccator 14 is brought to a
low pressure of, for example, 20.times.10.sup.-3 bar.
[0047] As soon as the desired pressure is reached, the stopcock 22
is opened in the desired manner. The beaker 12 is filled up to a
maximum fill level 24 with infiltration material that later
penetrates into the blank 10. The penetration is effected
principally from the topside and the side walls while the
underside, which is disposed on the beaker 12, is somewhat less
strongly infiltrated.
[0048] Although FIG. 1 illustrates a cylindrical blank 10, it is to
be understood that, in practice, predetermined shaped parts are
produced which are disposed on the base of the beaker 12 and are
wetted with infiltration material. After an infiltration time of 1
minute, an infiltration coating in a thickness of 0.3 to 0.6 mm has
already been formed therefrom.
[0049] FIG. 2 is a graphical illustration of the infiltration
coating depth as a function of the infiltration time. In accordance
with the present invention, it is advantageous that the coating
thickness in many regions can be accommodated to the requirements.
Thus, very fine-sectioned and thin oxide ceramic parts with a
decidedly low infiltration coating thickness which, however, offers
a certain translucence but, as well, offers a good securement of
the core, can also be worked.
[0050] It is advantageous, for example, in connection with an
infiltration depth of 1 mm or somewhat less, to simulate the
natural tooth enamel. The preferred region for the infiltration
depth is, however, greater than 0.4 mm.
[0051] FIG. 3 is a schematic illustration of a sintering oven 26.
The sintering oven comprises a plurality of heating elements 28 and
a crucible 30 that receives therein the blank 10 after
infiltration. Preferably, in a conventional manner, the crucible is
provided with a powder coating and there follows a heating or a
finish infiltration of the blank 10 to form the oxide ceramic part
within less than 1 hour, including the heating up time.
[0052] In the hereinafter following descriptions, various
embodiments are described in more individual detail.
EXAMPLE 1
[0053] A dry press granulate of ZrO.sub.2 powder is used for the
raw material for the blank 10. It is doped with yttrium and
comprises other components such as Al.sub.2O.sub.3. The dry press
granulates can be, for example, those available from the TOSOH
company with the commercial designation TZ-3YB and TZ-8YB and
having a primary crystal size of 280-400 nm and a granulate size of
50 .mu.m but, as well, can be the granulate available under the
commercial designation of TZ-3Y20AB that is characterized by the
addition thereto of 20% Al.sub.2O.sub.3 and that otherwise
corresponds to the other granulates.
[0054] In accordance with the following table, powdery oxidized raw
materials in predetermined mole portions are added to the zirconium
oxide ceramics.
1 Raw Material TZ3YB TZ3YB TZ3YB TZ3YB TZ8YB TZ8YB TZ8YB Oxide
CeO.sub.2 /mol-% 2.5 5 8 10 15 -- -- Er.sub.2O.sub.3 2.5 5 -- -- --
-- -- CeO.sub.2 + Er.sub.2O.sub.3 /mol-% 3 + 3 -- -- -- -- -- --
Sc.sub.2O.sub.3 /mol-% 3 -- -- -- -- -- -- TiO.sub.2 /mol-% 10 15
-- -- -- 10 15
[0055] In this inventive experiment, cylindrical press forms with
inner diameters of 12 and 16 mm were used. The pressing of the
blank 10 was effected in a conventional manner with pressures of
500, 600 to 1100 bar, whereby the press pressure was reached in 5
seconds, then held for 15 seconds at the maximum pressure, and then
reduced within a further 5 seconds.
[0056] Thereafter, there followed the pre-solidification step
during which, at the same time, the release was effected and this
is shown in the following table, which shows the serially following
time segments of the pre-sintering process with the slopes
indicated in the left hand column.
2 .degree. C..sub.Rn/ .degree. C..sub.Rn + 1/ Heat rate/ Slope
.degree. C. .degree. C. K min.sup.-1 K h.sup.-1 Time/min Time/h 1 0
320 2.5 150 128 2:08 2 320 470 1 50 150 2:30 3 470 1100 2.5 150 252
4:12 4 1100 1100 0 0 20 0:30 560 9:20
[0057] The powder comprises a binder in the form of a press
assistance material and, via the dry pressing in the following bond
release, the introduced binding material was burnt out and the
blank was thus formed with a porous structure. Thereafter, the
pre-sintering was performed. After the pre-sintering, a part with
50% thickness depth (TD) was achieved.
[0058] The evacuation of the blank 10 was performed in the
desiccator 14 with a finish pressure of approximately 20 mbar. Due
to the comparatively long evacuation time, which, in any event,
amounted to more than 1 hour, the gas enclosed in the porous blank
was substantially removed.
[0059] Infiltration material based upon
tetraethoxysilane/tetraethylorthos- ilicate (TEOS) was used. TEOS
was, together with water with a catalyst of aluminum nitrate
nonhydrate(Al(NO.sub.3).sub.3).times.9 H.sub.2O), mixed with a sol.
As a function of the mixing time and the subsequent standing time,
the sol. reacted slowly into a gel and condensed into a
glass-similar structure. Cerium nitratheydrate was also introduced
to the actual catalyst.
[0060] It was attempted to prepare the infiltration material so
that, after the infiltration into the infiltration coating, a firm
gel was quickly formed which converted after the sintering into a
silica glass phase. The infiltration coating was comprised, in
accordance with the invention, principally of tetragonal
crystalline zirconium oxide phases as well as an amorphous glass
phases, substantially from condensed TEOS, while the core of the
inventive oxide ceramic piece was substantially comprised of
zirconium oxide with the previously noted doping, which was, in any
event, predominantly in tetragonal phase.
[0061] The attempts with various mixing relationships of TEOS,
(Al(NO.sub.3).sub.3).times.9 H.sub.2O) as well as
Ce(NO.sub.3).sub.3.time- s.9 H.sub.2O revealed the tendency, in
connection with longer mixing times, that the solidification
time--that is, the standing time until solidification--decreased.
The sums or totals of the times amounted to typically 6 to 7 hours,
whereby the omission of the cerium nitratehydrate in certain mixing
relationships was able to produce solidification after a mixing
time of 3 hours.
[0062] The prepared infiltration material was then introduced into
the drip funnel and the stopcock 22 was opened and, in fact, was
opened to the extent that the blank was, in any event, fully
covered following the introduction of the sol., but not so far as
to permit an excess of infiltration material to flow through the
drip funnel, as such would have delayed the venting of the
desiccator.
[0063] The venting followed the complete opening of the stopcock,
after which the drip funnel 16 became empty.
[0064] The infiltration material that had been introduced through
the desiccator and thereafter placed under low pressure initially
foamed, whereby the low pressure was maintained.
[0065] As can be seen in FIG. 2, the infiltration depth is
dependent not only upon the viscosity of the introduced
infiltration material but, as well, is, in particular, dependent
upon the mixing time and the standing alone time of the
infiltration material (the difference between ZIO15 and
ZIO16b).
[0066] It is contemplated that the time for the process is to be
selected such that the solidification of the infiltration material
occurs after or during the infiltration. It is not critical if the
infiltration material has already solidified, whereby, as well, in
connection with fluid infiltration material, a thickening of the
coating is anticipated in that, as well, a fluid infiltration
material closes the pores of the blank 10.
[0067] Infiltration material remainders on the ceramic blank were
then removed easily with a towel and there followed an air-drying
step, whereby the inventive examples were subjected to an
air-drying of 1 to 2 hours.
[0068] The finished sintering followed in the same sintering oven
which had been deployed for the pre-sintering and the sintering
curve is shown in the following table in 3 time segments.
3 .degree. C..sub.Rn/ .degree. C..sub.Rn + 1/ Heat rate/ Slope
.degree. C. .degree. C. K min.sup.-1 K h.sup.-1 Time/min Time/h 1 0
1000 5 300 200 3:20 2 1000 1480 2.5 1450 192 3:12 3 1480 1480 0 0
30 0:30 422 7:02
[0069] In this connection, the blank was sealed in a quartz
frit--or Al.sub.2O.sub.3--powder bed in an aluminum oxide
crucible.
[0070] The results showed that the sintered blank comprises an
infiltration coating thickness which, in dependence upon the
infiltration time, is of varying thickness.
[0071] There was also obtained a good translucence of the oxide
ceramic part and, in the interior of the blank, a tetragonal phase
with an average crystal size of 0.4 to 0.5 micrometers was
present.
[0072] The smallest achieved infiltration depth, in connection with
the above-noted infiltrate based upon TEOS, amounted to
approximately 180 micrometers.
EXAMPLE 2
[0073] In a modified example, in lieu of TEOS, a zirconium (IV)
propylate (Zr(IV)Pr) was deployed. This zirconium (IV) propylate
was used in lieu of TEOS and, when subjected to atmospheric
pressure with water, was driven as zirconium oxide particles out of
the pores of the blank. Also, in this connection, the pores could
be closed, whereby the crystalline particles in the pores
precipitate out, which corresponds to the actual base material. The
thus achieved minimal coating thickness of the infiltration coating
amounted to approximately 50 micrometers.
EXAMPLE 3
[0074] In total, the inventive process produced an oxide ceramic
composite shaped part with high fracture strength, whereby the
translucence properties corresponded to those of zirconium oxide
ceramic (TZP) which are deployed in connection with the
high-temperature isostatic press process.
4 Density Light K.sub.ic-Value (in the Transmission (Evans &
Ptr/ t.sub.Inf./ (core)/ Capability HV 10/ Charles)/ Sample bar min
V.sub.Br/C g cm.sup.-3 (comparison) % MPa MPa m.sup.1/2 A1235 1000
1 1480 6.08 70.7 -- -- A1237 1000 5 1480 6.10 75.0 -- -- A1240 1000
2 1480 -- -- 13220 6.95 A1245 900 1 1480 -- -- 13055 6.55 A1246 900
1 1480 6.08 72.2 -- -- Mexoxit unknown unknown unknown 6.07 70.3
12850 6.65 Bio-HIP ZeO.sub.2 (comparison measurement) Denzir
unknown unknown unknown 6.10 76.4 12830 6.70 DO HIP-ZrO.sub.2
(comparison measurement) A1253 900 Not 1480 5.88 56.4 -- --
infiltrated A1254 900 Not 1480 -- -- 12900 6.17 infiltrated
[0075] As can be seen in the foregoing, it is clear that the
conventional sintered examples not produced in accordance with the
present invention exhibit considerably worse properties with
respect to light transmission capability and fracture strength.
EXAMPLE 4
[0076] Additionally, several attempts were made in connection with
the inventive process to effect the etching with HF and an etching
retentive design was produced in correspondence with the length of
time. Etching attempts were undertaken by which the outer coating
was completely etched away and only the inner oxide ceramic core
remained. By covering the infiltration coating with wax or a
polymer coating, it is also possible that selected locations can
remain unetched.
EXAMPLE 5
[0077] In correspondence with the above noted type and manner of
shaped part handling, a cylindrical part with a diameter of 12 mm
and a height of 25 mm was produced via pressing of a granulate
obtained from the Tosoh company (TZ 3YB) and subsequent
pre-sintering at 1100.degree. C. To perform thereafter a shaping of
the part, a CEREC Inlab milling machine available from the Sirona
Company was deployed, whereupon the thus-produced shaped part was a
crown having excess material. The excess material had to be removed
so that, following the shrinking which occurs in connection with
the sintering and the partial etching away of the covering coating,
an optimal size accommodation or fitment to the model frame was be
produced. In accordance with the present invention, the thus
obtained partially sintered and milled part was then provided with
a covering coating in a vacuum-configured environment, whereby the
applied material generally penetrated into the outer surface of the
porous partially sintered part. During the subsequent sintering
process in ambient air at ambient pressure, a finished sintered
crown was produced that, following partial etching away of the
covering coating, exhibited, on the one hand, a retentive design
and, on the other hand, a good size accommodation or fitment to the
model frame.
[0078] FIGS. 4 and 5 each show respective illustrations of the
results of the process steps in various configurations of the
inventive method. The thus-depicted configurations of the inventive
method differ from one another with respect to the timing of the
machining or trimming step: with respect to the configuration
"Technology II" depicted in FIG. 5, the machining or trimming step
is performed before the infiltration step while, with respect to
the configuration "Technology I" depicted in FIG. 4, the trimming
step is performed after the finish sintering step. The respective
configuration of the inventive method shown in FIG. 4 requires
greater tooling efforts in view of the high degree of securement of
the substantially completely finished sintered dental restoration
piece; however, this configuration of the inventive method offers a
somewhat greater degree of precision.
[0079] In all, the demonstrations conducted with respect to the
inventive method resulted in an oxide ceramic part having a high
fracture strength of 6.95 MPa m.sup.1/2, whereby the translucence
properties were correspondingly satisfactory and corresponded to
those of oxide ceramic parts that have been produced by
high-temperature isostatic press processes.
[0080] The present invention is, of course, in no way restricted to
the specific disclosure of the specification and drawings, but also
encompasses any modifications within the scope of the appended
claims. While a preferred form of this invention has been described
above and shown in the accompanying drawings, it should be
understood that applicant does not intend to be limited to the
particular details described above and illustrated in the
accompanying drawings, but intends to be limited only to the scope
of the invention as defined by the following claims. In this
regard, the term "means for" as used in the claims is intended to
include not only the designs illustrated in the drawings of this
application and the equivalent designs discussed in the text, but
it is also intended to cover other equivalents now known to those
skilled in the art, or those equivalents which may become known to
those skilled in the art in the future.
* * * * *