U.S. patent application number 15/319138 was filed with the patent office on 2017-05-11 for process for producing a sintered lithium disilicate glass ceramic dental restoration and kit of parts.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Helmut Mayr, Gallus Schechner.
Application Number | 20170128174 15/319138 |
Document ID | / |
Family ID | 50979604 |
Filed Date | 2017-05-11 |
United States Patent
Application |
20170128174 |
Kind Code |
A1 |
Mayr; Helmut ; et
al. |
May 11, 2017 |
PROCESS FOR PRODUCING A SINTERED LITHIUM DISILICATE GLASS CERAMIC
DENTAL RESTORATION AND KIT OF PARTS
Abstract
The present invention is directed to a process for producing a
sintered lithium disilicate glass ceramic dental restoration out of
a porous 3-dim article, the process comprising the step of
sintering the porous 3-dim article having the shape of a dental
restoration with an outer and inner surface to obtain a sintered
lithium disilicate ceramic dental restoration, the sintered lithium
disilicate glass ceramic dental restoration comprising--Si oxide
calculated as SiO2 from 55 to 80 wt.-%, --Li oxide calculated as
Li2O from 7 to 16 wt.-%, --Al oxide calculated as Al2O3 from 1 to 5
wt.-%, and--P oxide calculated as P2O5 from 1 to 5 wt.-%, wt.-%
with respect to the weight of the dental restoration, the sintering
being done under reduced atmospheric pressure conditions, the
reduced atmospheric pressure conditions being applied at a
temperature above 600.degree. C. The present invention is also
directed to a kit of parts comprising a porous 3-dim article having
the shape of a dental milling block and a respective instruction of
use.
Inventors: |
Mayr; Helmut; (Kaufering,
DE) ; Schechner; Gallus; (Herrsching, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
50979604 |
Appl. No.: |
15/319138 |
Filed: |
June 15, 2015 |
PCT Filed: |
June 15, 2015 |
PCT NO: |
PCT/US2015/035734 |
371 Date: |
December 15, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61C 13/0006 20130101;
A61K 6/853 20200101; C03B 19/06 20130101; B33Y 10/00 20141201; C03C
4/0021 20130101; C03C 10/0027 20130101; C03C 2204/00 20130101; C03C
2205/06 20130101; A61C 13/083 20130101; A61K 6/15 20200101; A61K
6/818 20200101; B33Y 70/00 20141201; A61K 6/822 20200101; C03C
17/001 20130101; A61C 13/0022 20130101; C03C 8/08 20130101; C03C
2217/485 20130101; A61K 6/16 20200101; C03C 2218/111 20130101; A61C
5/77 20170201; C03C 3/097 20130101; C03C 2218/114 20130101; A61C
5/70 20170201; A61K 6/871 20200101; A61C 13/0004 20130101; A61K
6/78 20200101; B33Y 80/00 20141201; C03B 19/01 20130101; C03C 19/00
20130101 |
International
Class: |
A61C 13/00 20060101
A61C013/00; A61C 13/083 20060101 A61C013/083; C03B 19/01 20060101
C03B019/01; C03B 19/06 20060101 C03B019/06; C03C 19/00 20060101
C03C019/00; C03C 17/00 20060101 C03C017/00; B33Y 10/00 20060101
B33Y010/00; B33Y 70/00 20060101 B33Y070/00; B33Y 80/00 20060101
B33Y080/00; C03C 10/00 20060101 C03C010/00; C03C 4/00 20060101
C03C004/00; C03C 8/08 20060101 C03C008/08; C03C 3/097 20060101
C03C003/097; A61K 6/02 20060101 A61K006/02; A61K 6/06 20060101
A61K006/06; A61K 6/00 20060101 A61K006/00; A61C 5/77 20060101
A61C005/77 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 23, 2014 |
EP |
14173389.9 |
Claims
1. A process for producing a sintered lithium disilicate glass
ceramic dental restoration out of a porous 3-dim article, the
process comprising: sintering the porous 3-dim article having the
shape of a dental restoration with an outer and inner surface to
obtain a sintered lithium disilicate ceramic dental restoration,
the sintered lithium disilicate glass ceramic dental restoration
comprising: Si oxide calculated as SiO2: from 55 to 80 wt.-%; Li
oxide calculated as Li2O: from 7 to 16 wt.-%; Al oxide calculated
as Al2O3: from 1 to 5 wt.-%; and P oxide calculated as P2O5: from 1
to 5 wt.-%, wt.-% with respect to the weight of the dental
restoration, the sintering being done under reduced atmospheric
pressure conditions, the reduced atmospheric pressure conditions
being applied above a temperature of 600.degree. C.
2. The process of claim 1 comprising: providing a porous 3-dim
article, the 3-dim article having either the shape of a dental
milling block or of a dental restoration with an outer and inner
surface; and for porous 3-dim articles having the shape of a
milling block, machining the porous 3-dim article to obtain a
machined porous 3-dim article having the shape of a dental
restoration with an outer and inner surface.
3. The process of claim 1, the sintering of the porous 3-dim
article having the shape of a dental restoration being conducted
without supporting the inner surface of the dental restoration
during sintering.
4. The process of claim 1, the porous 3-dim article having the
shape of a dental crown, dental bridge, veneer, inlay, onlay or
part thereof.
5. The process of claim 1, the porous 3-dim article being
characterized by at least one of the following features: Pore
volume: 70 to 20%; Density: from 0.5 to 2 g/cm3; Flexural strength:
20 to 75 MPa according to ISO 6872.
6. The process of claim 1, the material of the sintered lithium
disilicate glass ceramic dental restoration being characterized by
at least one of the following features: Pore volume: 0 to 2%;
Density: from 2.1 to 3 g/cm.sup.3; Flexural strength: 250 to 450
MPa according to ISO 6872.
7. The process of claim 1, the porous 3-dim article being obtained
by a process comprising an additive manufacturing technology using
a glass powder, the process optionally comprising the step of
coloring the porous 3-dim article by using coloring components
during the additive manufacturing technology.
8. The process of claim 1, the porous 3-dim article being obtained
by a process comprising the steps of: providing a glass powder;
pressing the glass powder to obtain a 3-dim article; and conducting
a pre-sintering step to obtain the porous 3-dim article.
9. The process of claim 1, further comprising a coloring step, the
coloring step being conducted by: either applying a coloring
solution to only parts of the outer surface of the porous 3-dim
article having the shape of a dental restoration; or treating the
whole surface of the porous 3-dim article having the shape of a
dental restoration with a coloring solution,
10. The process of claim 9, the coloring solution comprising a
solvent and coloring ions selected from V, Mn, Fe, Er, Tb, Y, Ce,
Sm, Dy or combinations thereof or coloring pigments comprising any
of those coloring ions or combinations thereof.
11. The process of claim 1, the sintered lithium disilicate glass
ceramic dental restoration further comprising at least one, two,
three or all of the following components: K oxide calculated as
K2O: from 0.1 to 5 wt.-%; Zr oxide calculated as ZrO2: from 0.1 to
15 wt.-%; Zn oxide calculated as ZnO2: from 0 to 2 wt.-%; Ce oxide
calculated as CeO2: from 0 to 2 wt.-%; Cs oxide calculated as CsO2:
from 0 to 8 wt.-%; Coloring metal oxides calculated as MO2 or M2O3,
with M being a metal ion: from 0 to 5 wt.-%.
12. The process of claim 1, the lithium disilicate glass ceramic
dental restoration not comprising ZrO2 in an amount of more than 20
wt.-%.
13. The process of claim 1, the process not comprising at least one
or all of the following steps: machining the sintered lithium
disilicate 3-dim article; machining an article containing lithium
metasilicate as main crystalline phase; machining an article
containing lithium disilicate as main crystalline phase.
14. The process for producing a sintered lithium disilicate glass
ceramic dental restoration out of a porous 3-dim article of claim
1, the process comprising: providing a porous 3-dim article, the
3-dim article having the shape of a dental milling block, the
porous 3-dim article having a density from 0.5 to 2 g/cm3,
machining the porous 3-dim article to obtain a machined porous
3-dim article having the shape of a dental restoration with an
outer and inner surface, optionally coloring the porous 3-dim
article having the shape of a dental restoration, sintering the
porous 3-dim article having the shape of a dental restoration with
an outer and inner surface at reduced atmospheric pressure without
supporting the inner surface of the porous 3-dim article having the
shape of a dental restoration during sintering to obtain a sintered
lithium disilicate ceramic dental restoration, the sintering being
done under reduced atmospheric pressure conditions, the reduced
atmospheric pressure conditions being applied at a temperature
above 600.degree. C., the sintered lithium disilicate glass ceramic
dental restoration having a density from 2 to 3 g/cm3 and
comprising: Si oxide calculated as SiO2: from 55 to 80 wt.-%; Li
oxide calculated as Li2O: from 7 to 16 wt.-%; Al oxide calculated
as Al2O3: from 1 to 5 wt.-%; and P oxide calculated as P2O5: from 1
to 5 wt.-%, wt.-% with respect to the weight of the dental
restoration.
15. A kit of parts comprising: a porous 3-dim article having the
shape of a dental milling block; an instruction of use comprising
the following process steps: machining a porous dental restoration
out of the 3-dim porous article having the shape of a dental
milling block; optionally coloring the porous dental restoration
with a coloring solution; conducting the sintering of the porous
dental restoration under reduced atmospheric pressure conditions,
the reduced atmospheric pressure conditions being applied at a
temperature above 600.degree. C.; optionally sintering the porous
dental restoration without using a support structure during
sintering; the porous 3-dim article having a pore volume from 70 to
20 vol.-% and comprising: Si oxide calculated as SiO2: from 55 to
80 wt.-%; Li oxide calculated as Li2O: from 7 to 16 wt.-%; Al oxide
calculated as Al2O3: from 1 to 5 wt.-%; and P oxide calculated as
P2O5: from 1 to 5 wt.-%; wt.-% with respect to the weight of the
porous 3-dim article.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a process for producing a sintered
lithium disilicate glass ceramic dental restoration out of a porous
3-dim article. The process comprises the step of sintering the
porous 3-dim article having the shape of a dental restoration with
an outer and inner surface to obtain a sintered lithium disilicate
ceramic dental restoration.
BACKGROUND ART
[0002] Lithium disilicate glass ceramics are widely used in the
dental industry since many years, because the material is said to
have a sufficient strength (e.g. about 400 MPa) and good aesthetic
properties (mainly high translucency) after sintering.
A dental milling block out of that material is typically provided
as follows: A powder mixture of oxide and colorants, if desired, is
melted, casted into a mould, and cooled, resulting in a dense glass
body.
[0003] The dense glass body is then heat treated in a first
crystallization step resulting in a dense part containing lithium
metasilicate as main crystalline phase. Pre-colored blocks are also
available allowing the manufacturing of dental restorations in
different tooth colors.
A dental article (e.g. crown) can be ground out of this block. This
is typically done in a dental lab.
[0004] Due to presence of lithium metasilicate as main crystalline
phase in the dental milling block, applying a dry milling process
for producing a dental restoration is not possible. The respective
block has to be shaped by applying a grinding process. A second
heat treatment/crystallization step is needed to give the dental
restoration its final optical and mechanical properties. If
desired, the obtained dental restoration can be further
individualized by applying e.g. a veneering material.
[0005] The current process has a limited productivity due to its
restriction to wet grinding and offers only limited possibilities
for the dental technician to individualize the desired dental
article especially with respect to colors and their
distribution.
[0006] EP 2 450 000 (3M IPC) describes the use of an open celled
glass or glass ceramic article, produced by a rapid prototyping
method, which is sintered on a ceramic framework. A process for
producing a dental article is described comprising Part A and Part
B, Part A and Part B each having a 3-dim. Structure and an outer
and an inner surface, the outer surface of Part A having a shape
which essentially corresponds to the shape of the inner surface of
Part B, Part B comprising a material with a porous section and
being produced with the aid of a rapid-prototyping technique, the
process comprising a heating step, wherein Part A is serving as
support structure for Part B during said heating step.
[0007] EP 0 916 625 (Ivoclar) describes a process for producing
molded translucent lithium disilicate glass ceramic products, the
process comprising the steps of a) providing a melt of a glass
comprising certain metal oxides, b) forming an cooling the melt to
a desired shape, c) tempering the formed glass-product in a range
from 400 to 1100.degree. C. to obtain a glass ceramic product. Step
b) is typically conducted by applying pressure to increase the
density.
[0008] US 2010/0248189 (3M IPC) describes the use of an open celled
block consisting of glass or glass ceramic for use as a facing. US
2014/0070435 (Vita) describes a porous, silicate, ceramic body with
a first density which can be sintered into a silicate, ceramic body
with a second density mainly used as a veneering U.S. Pat. No.
6,517,623 (Jeneric/Pentron Inc.) describes the use of crystallized
lithium disilicate as a pressing material. U.S. Pat. No. 8,444,756
(IvoclarVivadent) describes the use of the material as a veneering
material on zirconia after being crystallized in the powder state.
U.S. Pat. No. 8,557,150 (IvoclarVivadent) describes the established
two step process (lithium metasilicate containing
block-grinding-crystallization) for producing a lithium disilicate
glass ceramic dental article. DE 19 647 739 (IvoclarVivadent)
describes the use of lithium disilicate ingots.
[0009] U.S. Pat. No. 6,455,451 (Jeneric/Pentron Inc) describes
various compositions for lithium disilicate glass ceramic ingots
and the process for pressing dental articles. U.S. Pat. No.
7,452,836 and U.S. Pat. No. 7,816,291 (IvoclarVivadent) describe
compositions and process for lithium delicate glass ceramic. DE 10
2009 060 (DeguDent, Vita Zahnfabrik, Fraunhofergesellschaft)
describes different compositions for lithium disilicate glass
ceramics where coloring is done in the melting process and the
material is machined in the lithium metasilicate state.
[0010] WO 2013/053863 (IvoclarVivadent) describes possible
compositions for lithium disilicate glass ceramics that are
processed by machining in the lithium metasilicate state and
subsequent crystallization.
[0011] US 2009/0042717 (Apel et al.) describes lithium silicate
materials which are said to be easily millable and having a high
strength. The lithium silicate materials contain Me(II)O being
selected from CaO, BaO and SrO and less than 0.1 wt.-% ZnO.
[0012] U.S. Pat. No. 6,420,288 B2 (Schweiger et al.) deals with a
process for the preparation of shaped translucent lithium
disilicate glass ceramic products, which comprises producing a melt
of a starting glass containing SiO2 (57.0 to 80.0 wt.-%), Al2O3 (0
to 5.0 wt.-%), La2O3 (0.1 to 6.0 wt.-%), MgO (0 to 5.0 wt.-%), ZnO
(0 to 8.0 wt.-%) and Li2O (11.0 to 19.0 wt.-%). It is mentioned
that the additional incorporation of ZrO2 led to an increase in
translucency.
[0013] WO 2013/167723 A1 (Ivoclar) relates to pre-sintered blanks
on the basis of lithium disilicate glass-ceramic which are
particularly suitable for the production of dental restorations. To
avoid distortion it is suggested that the sintering should be
conducted using a supporting material having the same chemical
composition.
DESCRIPTION OF THE INVENTION
[0014] However, there is still a desire for a simplified process
for the production of dental restorations based on lithium
disilicate material resulting after sintering to a highly aesthetic
product. It would also be desirable to be able to produce dental
restorations based on a lithium disilicate material by applying a
dry milling process. It would also be desirable, to be able to
produce dental restorations based on a lithium disilicate material
by applying a simplified sintering process.
[0015] It would also be desirable, to be able to produce dental
restorations based on a lithium disilicate material wherein the
dental restorations can easily be individualized e.g. with respect
to color.
[0016] The invention described in the present text solves at least
some of the above needs.
[0017] According to one aspect, the invention relates to a process
for producing a sintered lithium disilicate glass ceramic dental
restoration out of a porous 3-dim article, the process comprising
the step of [0018] sintering the porous 3-dim article having the
shape of a dental restoration with an outer and inner surface to
obtain a sintered lithium disilicate ceramic dental restoration,
the sintered lithium disilicate glass ceramic dental restoration
comprising [0019] Si oxide calculated as SiO2 from 55 to 80 wt.-%,
[0020] Li oxide calculated as Li2O from 7 to 16 wt.-%, [0021] Al
oxide calculated as Al2O3 from 1 to 5 wt.-%, and [0022] P oxide
calculated as P2O5 from 1 to 5 wt.-%, wt.-% with respect to the
weight of the dental restoration, the sintering preferably being
done under reduced atmospheric pressure conditions, the reduced
atmospheric pressure conditions being applied at a temperature
above 600 or 700.degree. C., but not below. In a further aspect,
the invention relates to a kit of parts comprising [0023] a porous
3-dim article having the shape of a dental milling block, and
[0024] an instruction of use comprising the following process
steps: [0025] machining a porous dental restoration out of the
3-dim porous article having the shape of a dental milling block,
[0026] optionally coloring the porous dental restoration with a
coloring solution, [0027] conducting the sintering of the porous
dental restoration under reduced atmospheric pressure conditions,
the reduced atmospheric pressure conditions being applied at least
in a temperature range from 600 to 800.degree. C., [0028]
optionally sintering the porous dental restoration without using a
support structure during sintering, [0029] the porous 3-dim article
having a pore volume from 70 to 20 vol.-% and comprising the
following oxides: [0030] Si oxide calculated as SiO2 from 55 to 80
wt.-%, [0031] Li oxide calculated as Li2O from 7 to 16 wt.-%,
[0032] Al oxide calculated as Al2O3 from 1 to 5 wt.-%, and [0033] P
oxide calculated as P2O5 from 1 to 5 wt.-%, [0034] wt.-% with
respect to the weight of the porous 3-dim article.
DEFINITIONS
[0035] The term "3-dim dental article" means any solid article
having a volume above 0.5 ml which can and is to be used in the
dental field. Examples of 3-dim dental articles include dental mill
blanks, dental restorations and parts thereof.
A "dental restoration" means an article to be used for restoring a
missing or defective tooth structure. Dental restorations typically
comprise at least two parts: a dental support structure (sometimes
also referred to as frame or coping) and a dental facing. Examples
of dental restorations or parts thereof include crown(s),
bridge(s), veneer(s), facing(s), abutment(s), dental support
structure(s), inlay(s), onlay(s), full arch prosthese(s) and
monolithic structures.
[0036] The material the dental article is made of should not be
detrimental to the patient's health and thus free of hazardous and
toxic components being able to migrate out of the article. Dental
articles are typically of small size and may comprise sections
having a wall thickness in the range of about 100 .mu.m to 2,000
.mu.m or in the range of about 100 .mu.m to about 500 .mu.m. The
total volume of a dental article is typically below about 100 ml or
below about 50 ml or below about 10 ml or below about 5 ml. A
"support structure" is to be understood as a structure being
suitable to support or stabilize another article, especially during
a sintering process. A "dental support structure" is to be
understood as the part of a dental restoration which is typically
adhered to a tooth stump or inserted into the patients mouth and
suitable for being veneered by a dental facing or dental veneer. A
dental support structure has typically sufficient strength to
withstand chewing forces. Dental support structures are often made
of or comprise polycrystalline oxide ceramic materials including
ZrO.sub.2, and Al.sub.2O.sub.3, metals or alloys. Compared to other
framework such as pottery or paving stones, the dental framework is
small and filigree and of high strength. The thickness of the
dental framework can vary from very thin, e.g. at the edges and
rims (below about 0.1 mm) to considerably thick, e.g. in the biting
area (up to about 7 mm). However, dental frameworks may also be
made of or comprise metal or metal alloys.
[0037] The term "dental facing" or "dental veneer" refers to the
aesthetic part of a dental restoration, meaning the part comprising
an outer surface of the finished restoration. The dental facing is
further adapted to be applied to a frame or dental support
structure which forms another part of the dental restoration, and
the dental restoration is in turn applied to a tooth. The dental
facing is preferably arranged at those parts of the dental support
structure that are likely to be visible in a patient's mouth, or
that in particular functionally co-operate with the adjacent or
opposed teeth of a patient, for example. Dental veneers are also
small and filigree objects. The strength of dental veneers,
however, is typically lower compared to dental frameworks. Dental
veneers are typically made of or comprise glass or glass ceramic
materials.
[0038] A dental support structure or a dental veneer usually has a
3-dimensional inner and outer surface including convex and concave
structures. The outer surface of the dental framework typically
corresponds essentially to the inner surface of the dental veneer.
The inner surface of the dental framework typically corresponds
essentially to the outer surface of a prepared tooth stump, whereas
the outer surface of the dental veneer typically corresponds
essentially to the final dental restoration.
[0039] By "dental milling block" is meant a solid block (3-dim
article) of material from which a dental article can be machined. A
dental milling block may have a size of about 20 mm to about 30 mm
in two dimensions, for example may have a diameter in that range,
and may be of a certain length in a third dimension. A block for
making a single crown may have a length of about 15 mm to about 30
mm, and a blank for making bridges may have a length of about 40 mm
to about 80 mm. A typical size of a block as it is used for making
a single crown has a diameter of about 24 mm and a length of about
19 mm. Further, a typical size of a block as it is used for making
bridges has a diameter of about 24 mm and a length of about 58 mm.
Besides the above mentioned dimensions, a dental milling block may
also have the shape of a cube, a cylinder or a cuboid. Larger mill
blanks may be advantageous if more than one crown or bridge should
be manufactured out of one blank. For these cases, the diameter or
length of a cylindric or cuboid shaped mill blank may be in a range
of about 100 to about 200 mm, with a thickness being in the range
of about 10 to about 30 mm.
[0040] An "ingot" means a block of material which can be melted.
Such a block is typically used in a so-called "hot pressing
technique". The ingot, which is usually embedded in an investment
material, is heated to a certain temperature and the material
converted into a viscous state. The viscous material is
applied/pressed to the desired shape of a dental article or on the
outer surface of a support structure. A "powder" means a dry, bulk
solid composed of a large number of very fine particles that may
flow freely when shaken or tilted. A "particle" means a substance
being a solid having a shape which can be geometrically determined.
The shape can be regular or irregular. Particles can typically be
analysed with respect to e.g. grain size and grain size
distribution.
[0041] "Glass" means an inorganic non-metallic amorphous material.
Glass refers to a hard, brittle, transparent solid. Typical
examples include soda-lime glass and borosilicate glass. A glass is
an inorganic product of fusion which has been cooled to a rigid
condition without crystallizing. Most glasses contain silica as
their main component and a certain amount of glass former. Glasses
usually show an amorphous or diffuse X-ray pattern or diffraction.
"Glass-ceramic" means an inorganic non-metallic material where one
or more crystalline phases are surrounded by a glassy phase so that
the material comprises a glass material and a ceramic material in a
combination or mixture. Thus, a glass ceramic is a material sharing
many properties with both glass and crystalline ceramics. Usually,
it is formed as a glass, and then made to crystallize partly by
heat treatment. So, glass ceramics are made of a glassy phase with
crystals, which typically have no pores in the glassy phase or
between crystals. Glass ceramics can mainly refer to a mixture of
lithium-, silicium-, and aluminium-oxides. "Ceramic" means an
inorganic non-metallic material that is produced by application of
heat. Ceramics are usually hard and brittle and, in contrast to
glasses or glass ceramics, display an essentially purely
crystalline structure. A "ceramic article" is to be understood as
an article comprising a ceramic, glass or glass ceramic
material.
[0042] A "lithium silicate glass ceramic" means a material
comprising quartz, lithium dioxide, phosphorous oxide and alumina.
A lithium silicate glass ceramic may comprise lithium metasilicate
crystals (Li2SiO3), lithium disilicate crystals (Li2Si2O5) or a
mixture of both crystals. Lithium silicate glass ceramic comprising
mainly lithium metasilicate crystals has typically a low strength
and toughness compared to lithium silicate glass ceramic comprising
mainly lithium disilicate crystals. Lithium silicate glass ceramic
comprising mainly lithium metasilicate crystals can typically be
machined easily. After a machining step, the material can be
converted into a lithium disilicate glass ceramic material by a
heating step.
[0043] A "lithium disilicate glass ceramic" means a material
comprising mainly lithium disilicate crystals (e.g. content of
crystalline lithium disilicate phase above about 50 or above about
55 or above about 60 or above about 65 vol.-%; typical ranges
include from about 50 to about 90 or from about 55 to about 85 or
from about 60 to about 80 vol.-%).
The chemical composition of glasses, ceramics and glass ceramic
compositions is typically given by referring to the respective
oxides, e.g. SiO2, Li2O, etc.
[0044] "Density" means the ratio of mass to volume of an object.
The unit of density is typically g/cm.sup.3. The density of an
object can be calculated e.g. by determining its volume (e.g. by
calculation or applying the Archimedes principle or method) and
measuring its mass. The volume of a sample can be determined based
on the overall outer dimensions of the sample. The density of the
sample can be calculated from the measured sample volume and the
sample mass. The total volume of the ceramic material can be
calculated from the mass of the sample and the density of the used
material. The total volume of cells in the sample is assumed to be
the remainder of the sample volume (100% minus the total volume of
material).
[0045] An article is classified as "absorbent" if the article is
able to absorb a certain amount of a liquid, comparable to a
sponge. The amount of liquid which can be absorbed depends e.g. on
the chemical nature of the article, the viscosity of the solvent,
the porosity and pore volume of the article. E.g. a pre-sintered
ceramic article, that is an article which has not been sintered to
full density, is able to absorb a certain amount of liquid.
Absorbing of liquids is typically only possible if the article has
an open-porous structure.
[0046] A "porous material" refers to a material comprising a
partial volume that is formed by voids, pores, or cells in the
technical field of ceramics. Accordingly an "open-celled" structure
of a material sometimes is referred to as "open-porous" structure,
and a "closed-celled" material structure sometimes is referred to
as a "closed-porous" structure. It may also be found that instead
of the term "cell" sometimes "pore" is used in this technical
field. The material structure categories "open-celled" and
"closed-celled" can be determined for different porosities measured
at different material samples (e.g. using a mercury "Poremaster
60-GT" from Quantachrome Inc., USA) according to DIN 66133. A
material having an open-celled or open-porous structure can be
passed through by e.g. gases. Typical values for an "open-celled"
material are between about 15% and about 75% or between about 18%
and about 75%, or between about 30% and about 70%, or between about
34% and about 67%, or between about 40% to about 68%, or between
about 42% and about 67%. The term "closed-celled" relates to a
"closed porosity". Closed cells are those cells which are not
accessible from the outside and cannot be infiltrated by gases
under ambient conditions. The "average connected pore diameter"
means the average size of the open-celled pores of a material. The
average connected pore diameter can be calculated as described in
the Examples section.
[0047] The term "calcining" refers to a process of heating solid
material to drive off at least 90 percent by weight of volatile
chemically bond components (e.g., organic components) (vs., for
example, drying, in which physically bonded water is driven off by
heating). Calcining is done at a temperature below a temperature
needed to conduct a pre-sintering step.
[0048] The terms "sintering" or "firing" are used interchangeably.
A pre-sintered ceramic article shrinks during a sintering step,
that is, if an adequate temperature is applied. The sintering
temperature to be applied depends on the ceramic material chosen.
For ZrO.sub.2 based ceramics a typical sintering temperature range
is about 1100.degree. C. to about 1550.degree. C. Sintering
typically includes the densification of a porous material to a less
porous material (or a material having less cells) having a higher
density, in some cases sintering may also include changes of the
material phase composition (for example, a partial conversion of an
amorphous phase toward a crystalline phase).
[0049] "Isotropic sintering behaviour" means that the sintering of
a porous body during the sintering process occurs essentially
invariant with respect to the directions x, y and z. "Essentially
invariant" means that the difference in sintering behaviour with
respect to the directions x, y and z is in a range of not more than
about +/-5% or +/-2% or +/-1%.
[0050] A "solution" shall mean a composition containing solvent
with soluble components dissolved therein. The solution is a liquid
at ambient conditions. A "solvent" is any solvent which is able to
dissolve the coloring agent. The solvent should be sufficiently
chemically stable if combined with the coloring agent. That is, the
solvent shall not be decomposed by the other components present in
the composition.
"Soluble" means that a component (solid) can be completely
dissolved within a solvent. That is, the substance is able to form
individual molecules (like glucose) or ions (like sodium cations or
chloride anions) when dispersed in water at 23.degree. C. The
solution process, however, might take some time, e.g. stirring the
composition over a couple of hours (e.g. 10 or 20 h) might be
required.
[0051] "Coloring ions" shall mean ions which have an absorption in
the spectrum visible to the human eye (e.g. from about 380 to about
780 nm), which results in a colored solution (visible to the human
eye), if the coloring ions are dissolved in water (e.g. about 0.6
mol/l) and/or cause a coloring effect in the article which has been
treated with the coloring solution and sintered afterwards.
[0052] By "machining" is meant milling, grinding, cutting, carving,
or shaping a material by a machine. Milling is usually faster and
more cost effective than grinding. "Additive manufacturing" or
"Build-up technology" means rapid-prototyping techniques which can
be used for producing 3-dim. articles by processes including ink
jet printing, 3d-printing/powder bed printing, multijet plotting,
robo-casting, fused deposition modelling, laminated object
manufacturing, selective laser sintering or melting,
stereolithography, photostereolithography, or combinations
thereof.
[0053] Those and other techniques are e.g. described in U.S. Pat.
No. 5,902,441 (Bredt et al.), U.S. Pat. No. 6,322,728 (Brodkin et
al.) and U.S. Pat. No. 6,955,776 (Feenstra) and U.S. Pat. No.
7,086,863 (Van der Zel). The disclosure of these patents as it
regards the description of rapid-prototyping techniques is herewith
incorporated by reference and regarded as part of this
application.
Commercially available examples of rapid-prototyping equipment
which can be used include printers from ZCorp. company like the
printer ZPrinter.TM. 310 plus.
[0054] "Reduced atmospheric pressure conditions" means conditions
where the atmospheric pressure is willfully lowered by applying
technical means like a vacuum pump.
[0055] A composition is "essentially or substantially free of" a
certain component within the meaning of the invention, if the
composition does not contain said component as an essential
feature. Thus, said component is not wilfully added to the
composition either as such or in combination with other components
or ingredient of other components. A composition being essentially
free of a certain component usually contains the component in an
amount of less than about 1 wt.-% or less than about 0.1 wt.-% or
less than about 0.01 wt.-% with respect to the whole composition.
Ideally the composition does not contain the said component at all.
However, sometimes the presence of a small amount of the said
component is not avoidable e.g. due to impurities.
[0056] As used herein, "a", "an", "the", "at least one" and "one or
more" are used interchangeably. The terms "comprises" or "contains"
and variations thereof do not have a limiting meaning where these
terms appear in the description and claims. Also herein, the
recitations of numerical ranges by endpoints include all numbers
subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75,
3, 3.80, 4, 5, etc.).
[0057] Unless otherwise indicated, all numbers expressing
quantities of ingredients, measurement of properties such as
contrast ratio and so forth used in the specification and claims
are to be understood as being modified in all instances by the term
"about", especially if single values are concerned.
DESCRIPTION OF FIGURES
[0058] FIG. 1 shows a sample of a non-colored lithium disilicate
ceramic disc.
[0059] FIG. 2 shows a sample of a colored lithium disilicate
ceramic disc.
[0060] FIG. 3 shows crown machined from a dental milling block made
of a pre-sintered lithium silicate material.
[0061] FIG. 4 shows a crown based on a lithium disilicate
material.
[0062] FIG. 5 shows an inlay based on a lithium disilicate
material.
[0063] FIG. 6 shows a sintered crown according to the invention
placed on an artificial tooth stump.
[0064] FIG. 7 shows a sintered crown according to the prior art
placed on an artificial tooth stump.
[0065] FIG. 8 shows a diagram containing suitable reduced
atmospheric pressure and temperature conditions.
DETAILED DESCRIPTION
[0066] The process described in the present text is advantageous in
a number of aspects: It was found that highly aesthetic dental
restorations based lithium disilicate material can be obtained,
when during a certain temperature range the sintering is conducted
under reduced atmospheric pressure conditions.
[0067] Applying the reduced atmospheric pressure conditions during
a temperature range which is too low, the desired translucency of
the resulting dental restoration cannot be obtained.
[0068] Further, if desired, the porous 3-dim article can easily be
individualized in an early stage, e.g. by applying a coloring
solution to its absorbing surface. As the 3-dim article is in a
porous stage, it can also be machined easily, e.g. by using a dry
milling process. In addition, the final dental restoration can be
obtained in a one-step sintering process. There is no need to
isolate a product having lithium metasilicate as main crystalline
phase.
[0069] In contrast to the process described in EP 2 450 000 (3M
IPC), there is also no need to support the inner surface of the
dental restoration during sintering. It has been found that the
porous dental restoration described in the present text is
self-supporting during sintering. Thus, the porous 3-dim article
can be sintered to its final stage without distortion of its
geometry during sintering.
[0070] It was found, that in particular those dental restorations
were suitable to be sintered without support during the sintering
step, which were obtained from porous 3-dim articles having been
manufactured by using a build-up technology.
[0071] Previously, the veneering of e.g. a zirconia dental support
structure with a facing out of lithium disilicate material was
either done by applying a hot-pressing technique or by grinding the
veneer out of a solid dental milling block containing lithium
metasilicate as main crystalline phase and conducting a
crystallizing step. The process described in the present text
simplifies this procedure to a great extend.
[0072] The dental restoration (e.g. veneer) can now be machined
(e.g. milled) out of a pre-sintered and thus porous milling block
in an efficient way and sintered to its final shape without
supporting the dental restoration during sintering.
[0073] Further, according to the process described in the present
text it is now possible to provide the porous 3-dim article in
different shapes. The shape is not restricted by the available
pressing equipment. Any shape which can be obtained by applying a
build-up technology is now possible.
[0074] It was also found that conducting the sintering under
reduced atmospheric pressure can be beneficial for obtaining a
self-supporting 3-dim porous article, in particular a 3-dim porous
article having the shape of a dental crown, dental bridge, veneer,
inlay, onlay or part thereof and is advantageous for the
translucency and the color.
[0075] The invention relates to a process for producing a sintered
lithium disilicate glass ceramic dental restoration.
[0076] The process comprises the step of sintering a porous 3-dim
article having the shape of a dental restoration with an outer and
inner surface without using a support structure during the
sintering process, i.e. support less. The sintering is done under
reduced atmospheric pressure, in particular during a temperature
range from 600 to 800.degree. C. After sintering a sintered lithium
disilicate ceramic dental restoration is obtained.
[0077] According to a further embodiment, the process comprises the
steps of [0078] providing a porous 3-dim article, the 3-dim dental
article having either the shape of a dental milling block or of a
dental restoration with an outer and inner surface, [0079] for
porous 3-dim articles having the shape of a milling block,
machining the porous 3-dim article to obtain a machined porous
3-dim article having the shape of a dental restoration with an
outer and inner surface, [0080] sintering the porous 3-dim article
having the shape of a dental restoration with an outer and inner
surface to obtain a sintered lithium disilicate glass ceramic
dental restoration.
[0081] Thus, according to one embodiment, the porous 3-dim article
has the shape of a dental milling block. According to another
embodiment, the porous 3-dim article has the shape of a dental
restoration with an outer and inner surface. In any case, the
sintering step is applied to a porous 3-dim article having the
shape of a dental restoration with an outer and inner surface, but
not the 3-dim article in the shape of a dental milling block.
[0082] The porous 3-dim article can be characterized by one or more
or all of the following parameters: [0083] Pore volume: from 20 to
70% [0084] Density: from 0.5 to 2 g/cm3, [0085] Flexural strength:
from 20 to 75 MPa or from 30 to 60 MPa according to ISO 6872. If
desired, the parameters can be measured as described in the Example
section below. The porous 3-dim article comprises the same oxides
as the sintered lithium disilicate ceramic article.
[0086] The porous 3-dim article can be provided by using different
technologies. According to one embodiment, the porous 3-dim article
is provided by using an additive manufacturing technology. Suitable
additive manufacturing technologies are given in the definition
section above. Using an additive manufacturing technology allows
the manufacturing of basically any desired shape of the porous
3-dim article. Using an additive manufacturing technology also
allows the manufacturing of fully or only partially colored porous
3-dim articles.
[0087] In particular, using an additive manufacturing technology
allows the manufacturing of a porous 3-dim article having the shape
of a dental restoration and containing coloring components (e.g.
ions or pigments), which after sintering result in a tooth-colored
dental restoration.
[0088] The coloring components can be applied in liquid or solid
form during the additive manufacturing process. Suitable coloring
components include those as described for the coloring solutions in
the text further down below.
[0089] If desired, a heating or pre-sintering step can be applied
to strengthen the structure of the porous 3-dim article. According
to one embodiment, the build-up technology makes use of a glass
powder. The particles in the glass powder typically have a particle
size below about 70 .mu.m or below about 60 .mu.m or below about 25
.mu.m. If desired, the particle size can be measured with laser
diffraction. The adjustment of the particle size can be done using
a sieve having the desired maximum mesh size.
[0090] If larger particles are used for producing the article (e.g.
particles having a particle diameter above about 70 .mu.m or above
about 80 .mu.m), the surface resolution of the final product might
be reduced.
[0091] The nature and structure of the glass powder is not
particularly limited unless it is detrimental to the desired
performance of the composition.
[0092] The glass powder is preferably selected to be compatible for
use in human bodies. Furthermore, the glass powder is preferably
selected to provide good aesthetic appearance for the dental
restoration, in particular when combined with a dental framework.
Glass powder which can be used can typically be characterized by at
least one of the following features: [0093] comprising: [0094] Si
oxide calculated as SiO2: from 55 to 80 wt.-%, or from 59 to 72
wt.-%; [0095] Li oxide calculated as Li2O: from 7 to 20 wt.-%, or
from 10 to 16 wt.-%; [0096] Al oxide calculated as Al2O3: from 1 to
5 wt.-%; [0097] P oxide calculated as P2O5: from 1 to 5 wt.-%;
[0098] coefficient of thermal expansion: about 8*10.sup.-6K.sup.-1
to about 15.8*10.sup.-6K.sup.-1 or 8*10.sup.-6K.sup.-1 to about
9*10.sup.-6K.sup.-1 or about 12*10.sup.-6K.sup.-1 to about
13.6*10.sup.-6K.sup.-1 or from about 15*10.sub.-6K.sup.-1 to
15.8*10.sup.-6K.sup.-1; [0099] melting temperature (range): around
or less than about 1000.degree. C.; [0100] density: about 2.0 to
about 3.0 or about 2.2 to about 2.6 g/cm.sup.3 and/or [0101] glass
transition temperature: 500 to 600.degree. C. or 520 to 580.degree.
C., preferably about 550.degree. C.
[0102] According to another embodiment, the porous 3-dim article is
provided by using a technology comprising a pressing step and
heating step or pre-sintering step.
According to this embodiment, a glass powder is provided first and
pressed to a 3-dim article (sometimes also referred to as "green
body").
[0103] In a further step, the 3-dim article is heated or
pre-sintered to obtain a porous 3-dim article (sometimes also
referred to as "white body").
[0104] The temperature is adjusted to a range so that the porous
3-dim article does not contain lithium metasilicate or lithium
disilicate as main crystalline phase. Instead, the 3-dim article is
mainly still in an amorphous state.
[0105] Suitable pressure ranges for the pressing step include: from
0.1 to 20 MPa or from 0.5 to 15 MPa or from 1 to 10 MPa.
[0106] Suitable temperature ranges for the heating or pre-sintering
step include: from 400 to 700.degree. C. or from 450 to 650.degree.
C. or from 500 to 600.degree. C.
[0107] The sintering of the porous 3-dim article having the shape
of a dental restoration is typically conducted within a temperature
range from 800 to 1000.degree. C. or from 850 to 975.degree. C. or
from 900 to 950.degree. C.
[0108] It was found that conducting the sintering under reduced
atmospheric pressure is beneficial, in particular, if a
self-supporting porous 3-dim article and a high translucent and
tooth colored restoration is desired.
[0109] Without wishing to be bound to a certain theory, it is
assumed that reducing the atmospheric pressure during sintering may
help to reducing the number of voids which may be present in the
sintered article
[0110] "Reduced atmospheric pressure" means that the pressure is at
least 80% or at least 90% or at least 95% below the ambient
conditions.
[0111] Suitable conditions include the following ranges: from 200
to 5 hPa or from 100 to 10 hPa or from 50 to 25 hPa.
[0112] Applying reduced pressure only during certain time and/or
temperature regimes during sintering may also help to reduce or
avoid the formation of higher porosities, improves the
translucency, may help to reach the desired coloration, and may
help to reduce the overall sintering time.
[0113] It can be preferred, if the reduced atmospheric pressure
conditions are applied not from the beginning of the sintering
process, but later, e.g. after having conducted a first heat
treatment.
[0114] It can also be preferred, if the reduced atmospheric
pressure conditions are applied not until end of the cooling down
period, but stopped at the temperature obtained by conducting the
first heat treatment.
[0115] According to one embodiment, the sintering process is
conducted as follows: [0116] Conducting a first heat treatment to
obtain a first temperature T1 at an atmospheric pressure P1, T1
being preferably in the range of 600 to 800.degree. C. or 700 to
800.degree. C., P1 being in the range of 900 to 1100 hPa, [0117]
Holding temperature T1 and applying reduced atmospheric pressure
conditions P2, P2 being preferably in the range of 20 to 50 hPa,
[0118] Conducting a second heat treatment to obtain a second
temperature T2, T2 being preferably in the range of 850 to
1,000.degree. C., [0119] Holding at that temperature T2 for a
defined time t, t being preferably in the range of 180 to 1,800 s,
[0120] Conducting a first cooling treatment until T1 is reached,
[0121] Increasing the atmospheric pressure until P1 is reached,
[0122] Conducting a second cooling treatment until room temperature
(e.g. 23.degree. C.) is reached.
[0123] At the end of the sintering step a sintered litihium
disilicate glass ceramic dental article in the shape of a dental
restoration is obtained. That is, the obtained dental restoration
comprises lithium disilicate as main crystal phase (i.e. more than
50 vol.-%).
[0124] The sintering of the porous 3-dim article having the shape
of a dental restoration is typically done without supporting the
inner surface of the dental restoration during sintering.
[0125] This is a great benefit compared to other processes
described in the art, which typically require that at least the
inner surface of the porous dental restoration is supported during
sintering to avoid distortion, e.g. as described in US 2013 224688
(3M IPC).
[0126] In that document, the outer surface of the corresponding
support structure is used to support the inner surface of the
porous dental restoration.
[0127] Likewise, WO 2013/167723 A1 suggests conducting the
sintering step by supporting the article to be sintered.
[0128] During sintering, the material of the porous 3-dim article
having the shape of a dental restoration undergoes a sintering and
a crystallization process with the result that at the end the
material contains lithium disilicate as main crystalline phase
(i.e. above 50 vol.-%).
[0129] The obtained sintered lithium silicate glass ceramic
material may fulfill at least one or more or all of the following
parameters: [0130] Translucency: from 0.03 to 0.60 or from 0.1 to
0.4 (Mac Beth TD 932 sample thickness 1.50+/-0.05 mm polished with
9 .mu.m sandpaper); a translucency of 0.0 means that the sample is
fully transparent. [0131] Radiopacity: of more than 200%, or more
than 300% (according to ISO 6872); [0132] Coefficient of thermal
expansion: from 8.0 to 12*10.sup.-6/K or from 8.0 to 11*10.sup.-6/K
or from 9.0 to 10.4*10.sup.-6/K (according to ISO 6872); [0133]
Vickers hardness: at least 500 or at least 520 or at least 550 (HV;
0.2 kg); [0134] Flexural strength: of at least 250 MPa or at least
350 or at least 400 (according to ISO 6872); [0135] Refractive
index: in the range of 1.545 to 1.525 or in the range of 1.530 to
1.540 (measured with an Abee Refractometer).
[0136] If desired, the respective parameters can be determined as
outlined in the example section below.
[0137] The sintered lithium disilicate glass ceramic material is
characterized by comprising the following components: [0138] Si
oxide calculated as SiO2: from 55 to 80 wt.-%, or from 59 to 72
wt.-%; [0139] Li oxide calculated as Li2O: from 7 to 20 wt.-%, or
from 10 to 16 wt.-%; [0140] Al oxide calculated as Al2O3: from 1 to
5 wt.-%; [0141] P oxide calculated as P2O5: from 1 to 5 wt.-%.
[0142] The sintered lithium disilicate glass ceramic may further
comprise: [0143] K oxide calculated as K2O from 0 to 0.1 wt.-% or
from 0.001 to 0.002 wt.-%; [0144] Zr oxide calculated as ZrO2 from
0.0 to 4.0 wt.-% or from 0.01 to 0.05 wt.-%; [0145] Zn oxide
calculated as ZnO from 0 to 0.2 wt.-% or from 0.002 to 0.01 wt.-%;
[0146] Ce oxide calculated as CeO2 from 0.0 to 3.0 wt.-% or from
0.1 to 2.0 wt.-%; [0147] Cs oxide calculated as Cs2O from 6 to 30
wt.-% or from 10 to 15 wt.-%; [0148] Coloring components calculated
as the respective oxides: from 0 to 10 wt.-% or from 0.25 to 8
wt.-% or from 0.5 to 6 wt.-%.
[0149] Suitable coloring oxides comprise the oxides of V, Mn, Fe,
Er, Tb, Y, Ce, Sm, Dy and mixtures thereof.
[0150] The lithium disilicate glass ceramic material does typically
not comprise Zr oxide calculated as ZrO2: more than 20 wt.-%, more
than 15 wt.-% or more than 12 wt.-%.
[0151] According to another embodiment, the sintered lithium
disilicate glass ceramic material may have the following
composition, wherein the content of the various ions is calculated
based on the respective oxide:
[0152] Si oxide calculated as SiO2 from 55 to 80 wt.-% or from 60
to 65 wt.-%,
Al oxide calculated as Al2O3 from 1 to 5 wt.-% or from 1 to 2
wt.-%, B oxide calculated as B2O3 from 0 to 5 wt.-% or from 0 to 2
wt.-%, Li oxide calculated as Li2O from 7 to 16 wt.-% or from 8 to
13 wt.-%, Na oxide calculated as Na2O from 0 to 1 wt.-% or from
0.05 to 0.2 wt.-%, Cs oxide calculated as Cs2O from 6 to 30 wt.-%
or from 10 to 15 wt.-%, P oxide calculated as P2O5 from 1 to 5
wt.-% or from 1.5 to 3.0 wt.-%.
[0153] According to a further embodiment, the following components
might be present either alone or in combination with others.
Sr oxide calculated as SrO from 0.0 to 5 wt.-% or from 0.1 to 3.0
wt.-%; Ba oxide calculated as BaO from 0.0 to 7 wt.-% or from 0.1
to 3.0 wt.-%; Ti oxide calculated as TiO2 from 0.0 to 2 wt.-% or
from 0.1 to 3.0 wt.-%; Zr oxide calculated as ZrO2 from 0.0 to 4.0
wt.-% or from 0.01 to 0.05 wt.-%; Hf oxide calculated as HfO2 from
0.0 to 5.0 wt.-% or from 2.0 to 4.0 wt.-%; Fe oxide calculated as
Fe2O3 from 0.0 to 0.5 wt.-% or from 0.1 to 0.3 wt.-%; V oxide
calculated as VO2 from 0.0 to 0.5 wt.-% or from 0.01 to 0.3 wt.-%;
Y oxide calculated as Y2O3 from 0.0 to 1.5 wt.-% or from 0.1 to 1.0
wt.-%; Ce oxide calculated as CeO2 from 0.0 to 3.0 wt.-% or from
0.1 to 2.0 wt.-%; Sm oxide calculated as Sm2O3 from 0.0 to 2.0
wt.-% or from 0.0 to 1.0 wt.-%; Er oxide calculated as Er2O3 from
0.0 to 2.0 wt.-% or from 0.01 to 0.4 wt.-%; Dy oxide calculated as
Dy2O3 from 0 to 1.0 wt.-% or from 0.1 to 0.2 wt.-%; K oxide
calculated as K2O from 0 to 0.1 wt.-% or from 0.001 to 0.002 wt.-%;
Mg oxide calculated as MgO from 0 to 0.2 wt.-% or from 0.002 to
0.01 wt.-%; Zn oxide calculated as ZnO from 0 to 0.2 wt.-% or from
0.002 to 0.01 wt.-%; La oxide calculated as La2O3 from 0 to 0.1
wt.-% or from about 0.0001 to 0.01 wt.-%; wt.-% with respect to the
weight of the lithium silicate glass ceramic.
[0154] Certain of these oxides may fulfill specific functions
during the production process: [0155] SiO2 may function as a
network former and lithium silicate precursor. [0156] Al2O3 may
increase the chemical stability of the glass matrix. [0157] Li2O
may act as lithium silicate precursor. [0158] Cs2O may function as
fluxing agent and may help to control the phase separation and
increase the radiopacity. [0159] P2O5 may function as nucleating
agent. [0160] CeO2 may act as oxidative coloring stabilizer. [0161]
Er2O3 may act as a color adjusting agent (e.g. to reduce the
greenish color fault). [0162] BaO, SrO, Y2O3, ZrO2 and HfO2 can be
used to adjust the refractive index of the glass matrix. [0163] The
inventive lithium silicate glass ceramic does typically not
comprise K.sub.2O, MgO, ZnO, La2O3 or a mixture of those in an
amount above 0.5 wt.-% or above 0.4 wt.-% or above 0.3 wt.-% or
above 0.2 wt. % or above 0.1 wt.-% with respect to the weight of
the ceramic. [0164] According to a particular embodiment, the
lithium silicate glass ceramic does not comprise K2O in an amount
0.4 wt.-% or above 0.3 wt.-% or above 0.2 wt.-% or above 0.1 wt.-%
with respect to the weight of the ceramic. [0165] The Li2O content
is typically below 17 wt.-% or below 16 wt.-% with respect to the
weight of the glass ceramic. [0166] Reducing the amount of either
of oxides K2O, MgO, ZnO, La2O3 may facilitate the production of a
translucent ceramic material having the desired CTE value.
[0167] The lithium disilicate glass ceramic material described in
the present text does typically not comprise either of the
following crystal phases in an amount above 50 or above 40 or above
30 or above 20 or above 10 or above 5% (at room ambient conditions;
e.g. 23.degree. C.): apatite, tetragonal or cubic leucit,
[0168] If desired, the porous 3-dim article in the shape of a
dental restoration can be colored using a suitable coloring
solution.
[0169] According to one embodiment, the coloring solution is used
for being selectively applied to parts of the surface of the porous
3-dim article. That is, the solution is only applied to parts of
the surface of the 3-dim article but not to the whole surface.
[0170] According to another embodiment the solution is used for
being applied to the whole surface of the porous 3-dim article.
This can be achieved, e.g. by dipping the article completely into
the coloring solution.
[0171] The porous 3-dim article is usually treated with the
solution for about 0.5 to about 5 minutes, preferably from about 1
to about 3 minutes at room temperature (about 23.degree. C.).
Preferably no pressure is used. A penetration depth of the solution
into the article of about 5 mm is considered to be sufficient.
[0172] If a coloring solution is used, the process of producing the
dental restoration comprises the following steps: [0173] providing
a porous 3-dim article, the 3-dim article having either the shape
of a dental milling block or of a dental restoration with an outer
and inner surface, [0174] for porous 3-dim articles having the
shape of a milling block, machining the porous 3-dim article to
obtain a machined porous 3-dim article having the shape of a dental
restoration with an outer and inner surface [0175] applying a
coloring solution as described in the present text to the surface
of the porous 3-dim article, [0176] optionally drying the porous
3-dim article to which the coloring solution has been applied,
[0177] sintering the porous 3-dim article having the shape of a
dental restoration with an outer and inner surface to obtain an at
least partially colored and sintered lithium disilicate ceramic
dental restoration.
[0178] Coloring solutions which can be used typically comprise a
solvent and coloring ions.
Suitable solvents include water, alcohols (especially low-boiling
alcohols, e.g. with a boiling point below about 100.degree. C.) and
ketons.
[0179] The solvent should be able to dissolve the coloring ions
used.
[0180] Specific examples of solvents which can be used for
dissolving the cations contained in the solution include water,
methanol, ethanol, iso-propanol, n-propanol, butanol, acetone,
ethylene glycol, glycerol and mixtures thereof.
[0181] The solvent is typically present in an amount sufficient to
dissolve the components contained or added to the solvent.
[0182] Suitable coloring ions include the ions of V, Mn, Fe, Er,
Tb, Y, Ce, Sm, Dy or combinations thereof. Besides those cations
the solution may contain in addition coloring agent(s) selected
from those listed in the Periodic Table of Elements (in the 18
columns form) and are classified as rare earth elements (including
Ce, Nd, Sm, Eu, Gd, Dy, Ho, Tm, Yb and Lu) and/or of the subgroups
of the rare earth elements and/or salts of transition metals of the
groups 3, 4, 5, 6, 7, 9, 10, 11.
[0183] Anions which can be used include OAc.sup.-, NO.sub.3.sup.-,
NO.sub.2.sup.-, CO.sub.3.sup.2-, HCO.sub.3.sup.-, ONC.sup.-,
SCN.sup.-, SO.sub.4.sup.2-, SO.sub.3.sup.2-, gluturate, lactate,
gluconate, propionate, butyrate, glucuronate, benzoate, phenolate,
halogen anions (fluoride, chloride, bromide) and mixtures
thereof.
[0184] The solution may also contain organic components. By adding
organic molecules, the properties (e.g. viscosity, vapor pressure,
surface tension, stability, etc) can be modified.
[0185] Organic components which can be added include PVA, PEG,
ethylenglycol, surfactants or mixtures thereof.
[0186] The solution may also contain one or more complexing
agent(s). Adding a complexing agent can be beneficial to improve
the storage stability of the solution, accelerate the dissolving
process of salts added to the solution and/or increase the amount
of salts which can be dissolved in the solution.
[0187] The solution may also contain marker substance(s). Adding a
marker substance(s) can be beneficial in order to enhance the
visibility of the solution during use, especially, if the solution
is transparent and color-less.
[0188] Examples of marker substance(s) which can be used include
food colorants like Riboflavin (E101), Ponceau 4R (E124), Green S
(E142).
[0189] Suitable coloring solutions are also described in WO
2004/110959 (3M), WO 00/46168 A1 (3M), WO 2008/098157 (3M), WO
2009/014903 (3M) and WO 2013/022612 (3M).
[0190] The coloring solution is typically applied to the surface of
the porous 3-dim article with a suitable application device
comprising a reservoir and an opening, the reservoir containing the
coloring solution as described in the present text.
[0191] According to a particular embodiment, the device may have
the shape of a pen, the pen comprising a housing, a brush tip, a
removable cap and a reservoir for storing the solution described in
the present text.
[0192] The brush tip is typically attached or fixed to the front
end of the housing. The reservoir is typically fixed or attached to
the rear end of the housing. The removable cap is typically used
for protecting the brush tip during storage.
[0193] Using a pen may facilitate the application of the coloring
solution and will help the practitioner to save time.
[0194] According to one embodiment, the process can be described as
follows:
[0195] A process for producing a sintered lithium disilicate glass
ceramic dental restoration out of a porous 3-dim article, the
process comprising the step of [0196] a) providing a porous 3-dim
article, the 3-dim article having the shape of a dental milling
block, the porous 3-dim article having a density from 0.5 to 2
g/cm3, [0197] b) machining the porous 3-dim article to obtain a
machined porous 3-dim article having the shape of a dental
restoration with an outer and inner surface, [0198] c) optionally
coloring the porous 3-dim article having the shape of a dental
restoration, [0199] d) sintering the porous 3-dim article having
the shape of a dental restoration with an outer and inner surface
without supporting the inner surface of the porous 3-dim article
having the shape of a dental restoration during sintering to obtain
a sintered lithium disilicate ceramic dental restoration, the
sintering preferably being done under reduced atmospheric pressure
conditions, [0200] the sintered lithium disilicate glass ceramic
dental restoration having a density from 2 to 3 g/cm3 and
comprising [0201] Si oxide calculated as SiO2 from 55 to 80 wt.-%,
[0202] Li oxide calculated as Li2O from 7 to 16 wt.-%, [0203] Al
oxide calculated as Al2O3 from 1 to 5 wt.-%, and [0204] P oxide
calculated as P2O5 from 1 to 5 wt.-%, [0205] wt.-% with respect to
the weight of the dental restoration.
[0206] According to another embodiment, the process can be
described as follows:
[0207] A process for producing a sintered lithium disilicate glass
ceramic dental restoration out of a porous 3-dim article, the
process comprising the step of [0208] producing a porous 3-dim
article having the shape of a dental restoration with an outer and
inner surface using a build-up technology, the porous 3-dim article
having a density from 0.5 to 2 g/cm3, [0209] optionally coloring
the porous 3-dim article having the shape of a dental restoration,
[0210] sintering the porous 3-dim article having the shape of a
dental restoration with an outer and inner surface without
supporting the inner surface of the porous 3-dim article having the
shape of a dental restoration during sintering to obtain a sintered
lithium disilicate ceramic dental restoration, [0211] the sintering
being done under reduced atmospheric pressure conditions, the
reduced atmospheric pressure conditions being applied at a
temperature above 600 or 700.degree. C., [0212] optionally
sintering the porous dental restoration without using a support
structure during sintering, [0213] the sintered lithium disilicate
glass ceramic dental restoration having a density from 2 or 2.1 to
3 g/cm3 and comprising [0214] Si oxide calculated as SiO2 from 55
to 80 wt.-%, [0215] Li oxide calculated as Li2O from 7 to 16 wt.-%,
[0216] Al oxide calculated as Al2O3 from 1 to 5 wt.-%, and [0217] P
oxide calculated as P2O5 from 1 to 5 wt.-%, [0218] wt.-% with
respect to the weight of the dental restoration.
[0219] According to a further embodiment the present invention is
directed to a process for producing a sintered lithium disilicate
glass ceramic dental restoration out of a porous 3-dim article, the
process comprising the step of [0220] sintering the porous 3-dim
article having the shape of a dental restoration with an outer and
inner surface to obtain a sintered lithium disilicate ceramic
dental restoration, [0221] the sintered lithium disilicate glass
ceramic dental restoration comprising [0222] Si oxide calculated as
SiO2 from 55 to 80 wt.-%, [0223] Li oxide calculated as Li2O from 7
to 16 wt.-%, [0224] Al oxide calculated as Al2O3 from 1 to 5 wt.-%,
and [0225] P oxide calculated as P2O5 from 1 to 5 wt.-%, [0226]
wt.-% with respect to the weight of the dental restoration, the
sintering of the porous 3-dim article having the shape of a dental
restoration being conducted without supporting the inner surface of
the dental restoration during sintering, wherein the description of
the process conditions and formulations and shapes of the article
are as described in the present text.
[0227] The invention is also directed to a kit of parts comprising
[0228] a porous 3-dim article having the shape of a dental milling
block, [0229] an instruction of use comprising the following
process steps: [0230] machining a porous dental restoration out of
the 3-dim porous article having the shape of a dental milling
block, [0231] optionally coloring the porous dental restoration
with a coloring solution, [0232] sintering the porous dental
restoration, the sintering being done under reduced atmospheric
pressure conditions, the reduced atmospheric pressure conditions
being applied at least above a temperature of 600 or 700.degree.
C., the porous 3-dim article having a pore volume from 20 to 70
vol.-% and comprising the following oxides: [0233] Si oxide
calculated as SiO2 from 55 to 80 wt.-%, [0234] Li oxide calculated
as Li2O from 7 to 16 wt.-%, [0235] Al oxide calculated as Al2O3
from 1 to 5 wt.-%, and [0236] P oxide calculated as P2O5 from 1 to
5 wt.-%, wt.-% with respect to the weight of the porous 3-dim
article.
[0237] The porous 3-dim article, the dental milling block, the
dental restoration, the coloring solution, the machining step, the
coloring step, the sintering step and the other process conditions
are as described in the present text above.
[0238] All components used for producing the dental restoration
described in the present text should be sufficiently biocompatible
either from the beginning or in its final state (e.g. due to
incorporation in a matrix); that is, the composition should not
produce a toxic, injurious, or immunological response in living
tissue.
[0239] The dental restoration described in the present text does
not contain components or additives which jeopardize the intended
purpose to be achieved with the invention. Thus, components or
additives added in an amount which finally results in a
non-tooth-colored dental article after sintering are usually not
contained. Typically, a dental article is characterized as not
being tooth colored, if it cannot be allocated a color from the
Vita.TM. color code system, known to the person skilled in the art.
Additionally, components which will reduce the mechanical strength
of the dental restoration to a degree, where mechanical failure
will occur, are usually also not included in the dental
article.
[0240] The process described in the present text does typically not
comprise either or all of the following process steps: [0241]
machining a sintered lithium disilicate 3-dim article; [0242]
machining an article containing lithium metasilicate as main
crystalline phase; [0243] machining an article containing lithium
disilicate as main crystalline phase. The complete disclosures of
the patents, patent documents, and publications cited herein are
incorporated by reference in their entirety as if each were
individually incorporated. Various modifications and alterations to
this invention will become apparent to those skilled in the art
without departing from the scope and spirit of this invention. The
above specification, examples and data provide a description of the
manufacture and use of the compositions and methods of the
invention. The invention is not limited to the embodiments
disclosed herein. One skilled in the art will appreciate that many
alternative embodiments of the invention can be made without
departing from the spirit and scope of thereof.
[0244] The following examples are given to illustrate, but not
limit, the scope of this invention.
[0245] Unless otherwise indicated, all parts and percentages are by
weight.
EXAMPLES
[0246] Unless otherwise indicated, all parts and percentages are on
a weight basis, all water is de-ionized water, and all molecular
weights are weight average molecular weight. Moreover, unless
otherwise indicated all experiments were conducted at ambient
conditions (23.degree. C.; 1013 mbar).
Measurements
Quantitative Rietveld Phase Analysis/Crystalline Content
[0247] If desired, a quantitative Rietveld phase analysis can be
done with a Bruker (Germany) AXS Type: D8Discover spectrometer.
Such an analysis allows e.g. the determination of the content of
crystalline phases.
Flexural Strength
[0248] If desired, the flexural strength can be measured with a
Zwick (Germany) type Z010 machine according to ISO 6872.
X-ray Opacity
[0249] If desired, x-ray opacity can be measured with an X-ray
machine (60 kV; sample thickness: 2 mm) according to ISO 6872.
Coefficient of Thermal Extension (CTE)
[0250] If desired, CTE can be determined with a Netzsch (Germany)
Type DIL 402 C dilatometer according to ISO 6872 (sample size:
4.5*4.5*26 mm; heating rate: 5.00 K/min).
[0251] If desired, the CTE value(s) can also be calculated similar
to refractive indices by using additive factors as described in the
literature known to the skilled person (e.g. Appen, A. A., Ber.
Akad. Wiss. UDSSR 69 (1949), 841-844).
Chemical Stability
[0252] If desired, chemical stability can be tested according to
ISO 6872. Test specimens having a surface of 30-40 cm.sup.2; (50*30
mm; 1-4 mm thickness) are typically cut and stored for 18 h in 4%
acetic acid (80.degree. C.).
Translucency/Contrast Ratio (CR)
[0253] If desired, the translucency can be determined with a
Macbath TD 932 System. Samples are cut into slices (thickness:
1.50+/-0.05 mm), polished (surface roughness: 9 .mu.m) and the
translucency is measured.
Milling Properties
[0254] If desired, milling experiments can be done on a Sirona,
Cerec.TM. Inlab machine. Blocks from sample GK 79
(14.times.12.times.18 mm) were pressed and an anterior crown was
milled out of a porous presintered block (650.degree. C./20 min).
The porous presintered block could easily be milled.
Particle Size
[0255] If desired, the mean particle size can be determined using a
commercially available granulometer (Laser Diffraction Particle
Size Analysis Instrument, MASERSIZER 2000; Malvern Comp.) according
to the instruction of use provided by the manufacturer.
Porosity
[0256] If desired, the porosity or open porosity can be measured
using a mercury porosimeter in accordance with DIN 66133 as
available under the designation "Poremaster 60-GT" from
Quantachrome Inc., USA.
Density
[0257] If desired, the density can be determined by determining the
weight and the dimension of the sample and calculating the
density
Example 1 (Non-Colored Lithium Disilicate Ceramic Disc)
[0258] The following amounts of powder were mixed in a bottle: 72.1
wt.-% SiO2, 15.1 wt.-% Li2CO3, 3.4 wt.-% Li3PO4, 3.5 wt.-% Al(OH)3,
3.2 wt.-% K2CO3 and 2.7 wt.-% ZrO2.
In a next step the powder mixture was melted in a platinum crucible
at 1500.degree. C. and fitted in water. This was repeated three
times. Afterwards the frit was milled. The resulting glass powder
had the following particle size distribution: d50: 13.5 .mu.m (d10:
2.5 .mu.m, d90: 49.6 .mu.m).
[0259] The powder was mixed with 10 wt.-% water and pressed to
discs (dimensions: 20 mm.times.1.5 mm) or blocks (dimensions: 12
mm.times.14 mm.times.18 mm) by applying a pressure of 7.5 MPa).
[0260] Glass ceramic bodies with 98-100% theoretical density were
achieved with the following one step crystallization and sintering
program: [0261] Heating with 5 K/min to 730.degree. C.; [0262]
Holding at 730.degree. C. till Vacuum on; [0263] Heating with 10
K/min to 930.degree. C.; [0264] Holding time 10 min; [0265] Cooling
with 10 K/min to 730.degree. C.; [0266] Holding at 730.degree. C.
Vacuum off; [0267] Cooling within furnace.
[0268] Conducting these processing steps resulted in dense glass
ceramic discs with the following properties: [0269] Density: 2.43
g/cm3 [0270] Crystallinity: 54% [0271] Bending strength: 250 MPa
[0272] Opacity: 55%.
[0273] The obtained sample is shown in FIG. 1.
Example 2 (Colored Lithium Disilicate Ceramic Disc)
[0274] A disc as described in Example 1 was prepared. The disc was
pre-sintered at 550 to 650.degree. C. to obtain a porous body.
[0275] The porous body was colored by immersing it in commercially
available coloring liquids or by applying commercially available
coloring liquids with a brush to its surface (Lava.TM. Plus
Coloring Liquids and/or Lava.TM. Plus Effect Shades; 3M ESPE).
[0276] After sintering, a colored lithium disilicate glass ceramic
was obtained, which has been colored in the amorphous and porous
state (i.e. before sintering). The sample obtained is shown in FIG.
2 on the right side. For comparison, the left disc is
non-colored.
Example 3 (Dental Restorations)
[0277] A crown was machined out of a pre-sintered dental milling
block obtained as described in Example 1 using a Lava.TM. CNC 500
milling machine (3M ESPE). A picture of the crown machined from a
dental milling block made of a pre-sintered lithium silicate
material is shown in FIG. 3.
[0278] Similarly, an inlay was machined out of a pre-sintered block
obtained as described in Example 1 using a Sirona CEREC.TM.
inLab.
[0279] In FIG. 4 a sintered lithium disilicate crown is shown. The
crown was produced by machining it out of a pre-sintered block,
coloring the obtained crown in a pre-sintered stage as described in
Example 2 and sintering the crown in one step applying the
conditions described in Example 1.
[0280] The crown was sintered without using a sintering support.
The obtained sintered dental restoration did not show any relevant
distortion.
[0281] FIG. 5 shows an inlay produced in the same manner as the
crown above.
Example 4 (Comparison)
[0282] An artificial tooth stump was provided, the surface of the
tooth stump was scanned and a dental crown designed for that tooth
stump using Lava.TM. Design 7 software 3M ESPE). One dental crown
was machined out of a pre-sintered lithium disilicate block--Crown
A. One dental crown was machined out of a pre-sintered Lava.TM. DVS
block (3M ESPE)--Crown B. Crown A was sintered according to the
process described in Example 1 without supporting the inner surface
of the dental crown during sintering.
[0283] Crown B was sintered as described in the instruction of use
provided by the manufacturer, but without supporting the inner
surface of the dental crown during sintering.
[0284] The sintered crowns were placed on the artificial tooth
stump and inspected visually for fit. The results are shown in
FIGS. 6 and 7. Crown A fitted nearly perfectly on the artificial
tooth stump (FIG. 6), whereas Crown B did not fit (FIG. 7).
Example 5 (Reduced Atmospheric Pressure Conditions)
[0285] Discs as described in Example 1 were prepared. Different
conditions of heating rate and duration of vacuum were applied. The
sintering temperature was 925.degree. C. and the dwell time at this
temperature was 600 s. The respective conditions are shown in Table
1.
TABLE-US-00001 Temperature range T1 Appearance during which reduced
(determined by atmospheric pressure Heating inspecting with Nr
conditions were installed rate human eyes) 1 730.degree.
C.-730.degree. C. 5 K/min Clear white, translucent (see FIG. 1) 2
500.degree. C.-500.degree. C. 5 K/min grayish 3 450.degree.
C.-300.degree. C. 5 K/min grayish 4 23.degree. C.-23.degree. C. 5
K/min grayish 5 23.degree. C.-23.degree. C. 25 K/min more
grayish
Table 1
[0286] It was found that a sufficiently translucent article can
only be obtained when the reduced atmospheric pressure conditions
are applied above a certain temperature range. Applying the reduced
atmospheric pressure conditions already below a certain temperature
resulted in articles having a grayish appearance.
[0287] Further the heating rate should be not too fast. It was
found that a moderate heating rate (e.g. 2 to 10 K/min) may be
further beneficial for achieving an aesthetic article.
[0288] FIG. 8 visualizes the reduced pressure and temperature
conditions applied in the Examples 1-4 described above. The level
of vacuum corresponds to the levels which can be adjusted according
to the instruction of use provided by the manufacturer. Level 0
means no vacuum (i.e. ambient conditions); level 10 means maximum
vacuum possible.
Example 6 (Additive Manufacturing)
[0289] If desired, a porous 3-dim article having the shape of a
dental restoration can also be produced by applying an additive
manufacturing technology, e.g. using a 3d-printing technique. A
suitable process can be described as follows: An STL computer file
describing the 3-dim. shape of the dental restoration to be
produced (e.g. dental veneer) is loaded into the software of the
printer (ZCorp 310 plus printer; ZCorporation, Burlington,
USA).
[0290] The printing is done as described in the instruction for use
provided by the manufacturer of the printer, wherein parameters
like shrinkage and layer thickness are additionally taken into
account.
[0291] A water based binder (obtainable from ZCorporation,
Burlington, USA) is jetted onto specific sections of the uppermost
layer of the powder as calculated by the software of the printer.
The binder component on the surface of the powder is partly
dissolved. The respective particles will stick together. This step
is repeated until the shape of the desired article is obtained.
After drying, the printed article is removed from the powder-bed
and excessive powder is removed (e.g. using pressurized air).
* * * * *