U.S. patent application number 10/668552 was filed with the patent office on 2005-03-24 for aesthetic ceramic veneered restoration.
Invention is credited to Appelman, Petrus Gerardus, Cornelissen, Eric Marinus Hermanus, Gebhardt, Jurgen, Kler, Marcel Andre de, Zel, Joseph Maria van der.
Application Number | 20050064369 10/668552 |
Document ID | / |
Family ID | 31896939 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050064369 |
Kind Code |
A1 |
Zel, Joseph Maria van der ;
et al. |
March 24, 2005 |
Aesthetic ceramic veneered restoration
Abstract
The present invention relates to an aesthetic dental restoration
having a layered structure, which dental restoration has the
appearance of a natural tooth. In addition, the present invention
relates to a method for preparing such dental restorations.
Particularly, the invention is based on the control of interaction
between opalescence and fluorescence.
Inventors: |
Zel, Joseph Maria van der;
(Hoorn, NL) ; Appelman, Petrus Gerardus; (Opmeer,
NL) ; Cornelissen, Eric Marinus Hermanus; (Huizen,
NL) ; Kler, Marcel Andre de; (Alkmaar, NL) ;
Gebhardt, Jurgen; (Pegnitz, DE) |
Correspondence
Address: |
DENTSPLY INTERNATIONAL INC.
570 West College Avenue
York
PA
17405
US
|
Family ID: |
31896939 |
Appl. No.: |
10/668552 |
Filed: |
September 22, 2003 |
Current U.S.
Class: |
433/203.1 |
Current CPC
Class: |
A61K 6/822 20200101;
A61K 6/836 20200101; A61C 13/09 20130101; A61K 6/16 20200101; A61K
6/807 20200101; A61K 6/827 20200101 |
Class at
Publication: |
433/203.1 |
International
Class: |
A61C 013/08 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 20, 2003 |
EP |
02078949.1 |
Claims
1. Dental restoration comprising one or more opaque layers covered
by one or more other porcelain layers, the opaque layers being
situated closer to the core than the other porcelain layers,
wherein at least one of the opaque layers contains a fluorescent
material, and wherein the one or more other porcelain layers are
predominantly transparent and opalescent.
2. The dental restoration of claim 1, wherein the other porcelain
layers comprise at least one incisal layer, at least one dentin
layer, and optionally at least one opaque/dentin layer.
3. The dental restoration of claim 2, wherein between the incisal
layer and the dentin layer and/or between the dentin layer and the
opaque/dentin layer a modifier containing fluorescent material is
present.
4. Method of layering porcelain on a structure of metal or ceramic
comprising the steps of applying a first layer or first layers of
an opaque liner material containing a fluorescent material and in a
subsequent step applying one or more layers of a translucent,
opalescent material.
5. The method of claim 4, wherein at least 2 wt. % of a fluorescent
material is present in the liner material, drawn to the total
weight of the liner material.
6. The method of claim 5, wherein the fluorescent material
comprises and preferably consists of yttriumoxide.
7. The method of claim 4, wherein the translucent, opalescent
material contains less than 0.05 wt. % fluorescent material.
8. The method of claim 4, wherein at least 10% of an opal glass
frit is used as the translucent, opalescent material.
9. The method of claim 4, wherein the translucent, opalescent
material has a translucency of more than 30%.
10. The method of claim 4, wherein transparent porcelain layers are
applied which consist of 10-100 wt. % opal glass frit with the
following composition in wt. %: 45-70% SiO.sub.2, 0-20%
Al.sub.2O.sub.3, 0-20% K.sub.20, 0-15% Na.sub.2O, 0-5% CaO, 0-3%
MgO, 0-4% CeO.sub.2, 0-4% Tb.sub.2O.sub.3, 1-10% P.sub.2O.sub.5,
0-1% CaF.sub.2, 0-2% Li.sub.2O, and 0-5% Sb.sub.2O.sub.3.
11. The method of claim 4, wherein transparent porcelain layers are
applied which consist of 10-100 wt. % opal glass frit with the
following composition in wt. %: 45-70% SiO.sub.2, 0-20%
Al.sub.2O.sub.3, 0-20% K.sub.2O, 0-15% Na.sub.2O, 0-5% CaO, 0-3%
MgO, 0-4% CeO.sub.2, 0-4% Tb.sub.2O.sub.3, 0-2% P.sub.2O.sub.5,
5-15% CaF.sub.2, 0-2% Li.sub.2O, and 0-5% Sb.sub.2O.sub.3.
Description
[0001] The present invention relates to aesthetic ceramic veneered
dental restorations and to a process and system for producing such
restoration. More particularly, the present invention is based on a
process for the production of an aesthetic porcelain veneered
restoration on the basis of a new shade build-up, based on a
functional separation between two optical phenomena, opalescence
and fluorescence.
[0002] Dental restorations have been prepared in the prior art
which comprise a substructure of a metal or ceramic material, upon
which substructure layers of porcelain are applied. Generally, the
substructure is covered by a layer of opaque material to effect
that the substructure has not an adverse effect on the appearance
of the restoration in the mouth. It is described in, for instance,
U.S. Pat. No. 5,453,290 that a metal substructure is covered with
an opaque layer, and a dentin layer. Generally, nowadays, ceramic
or metal alloy substructures are first covered by an opaque layer,
followed by an opacious dentin layer, a dentin layer and finally an
incisal porcelain layer.
[0003] Especially the last decades, there is a tendency to prepare
dental restorations which have an appearance that differs as little
as possible from the natural teeth of a person needing a dental
restoration. It is also one of the primary aims of the present
invention to prepare a dental restoration that will blend in
naturally with the remaining dentition in the mouth of the
individual needing said restoration. That is, a primary aim
underlying the present invention is to provide dental restorations
which have the appearance of a natural tooth.
[0004] With this aim in mind, in the prior art the dental
technician has incorporated in the various layers of a dental
restoration, colouring agents with the aim to adapt the colour of
the restoration to the colour of the teeth in the mouth of the
individual for which the restoration is produced. Moreover, the
surfaces of the restorations were treated such that these gave the
impression of natural teeth.
[0005] However, such traditional veneering ceramics have a blocky
appearance, while the actual shade of the restoration comes from
the material itself.
[0006] More in particular, the skilled person appreciates that the
appearance of an artificial tooth is not only dependent on colour
and surface properties, but that also the transmission behaviour of
light is important. It is known that homogeneous transparent masses
of porcelain with a smooth surface give a reflecting and clear
appearance, while the addition of reflecting particles to the
porcelain mass or a rough surface create a diffuse light
scattering; the light transmission is hindered. Opalescence and
fluorescence are also important features.
[0007] Dental technicians generally add sufficient amounts of
fluorescent material, and particularly yttriumoxide in the
porcelain material, so that a "black hole" appearance under certain
lighting conditions is prevented. The fluorescent material,
however, also has a slightly opaquefying effect; it creates a
somewhat cloudy effect which hinders the transmission of light and
which has a negative influence on the translucency of the
restoration made. That is, light only partly penetrates the
veneering material and is diffusely distributed inside the
material, giving the restoration its "coloured tooth"
appearance.
[0008] Opalescense is an optic phenomenon, caused by the so-called
Tyndall-effect of light absorption by particle light scattering. To
introduce the impression of opalescence, it has been proposed to
add blue pigments. However, such blue pigments give under different
light conditions different effects.
[0009] Although the dental technician was confronted many times
with the goal to produce a dental restoration that will blend in
naturally with the remaining dentition, so far this goal has not
been totally reached. Exactly copying the shade of the adjacent
teeth is a painstaking trial-and-error task and does not always
lead to success because of the individuality of teeth.
[0010] The present invention aims to solve, or at least to reduce
the problems encountered in the prior art. It is based on the
control of opalescence and fluorescence properties in the porcelain
or ceramic material used in the preparation of dental
restorations.
[0011] Particularly, in a first aspect, the present invention
relates to a dental restoration comprising one or more opaque
layers covered by one or more other porcelain layers, the opaque
layers being situated closer to the core than the other porcelain
layers, wherein at least one of the opaque layers contains a
fluorescent material, and wherein the one or more other porcelain
layers are predominantly transparent and opalescent. That is, the
fluorescence required to provide a natural appearance originates
from the deeper laying layers, while the required opalescence
originates from the layers closer to the surface of the dental
restoration.
[0012] In a second aspect, the present invention relates to a
method of layering porcelain on a structure of metal or ceramic
comprising the steps of applying a first layer or first layers of
an opaque liner material containing a fluorescent material and in a
subsequent step applying one or more layers of a translucent,
opalescent material.
[0013] U.S. Pat. No. 4,741,699 describes dental porcelain before
opalescense was introduced. In this document is it aimed to match
not only the colour but also the fluorescence of teeth in
restorations to that of natural teeth. Thereto, it requires that
the inorganic pigment that causes the fluorescent effect is lower
in the outer, more translucent layers, because of light absorbance
by the stained porcelain. It is well known that to obtain the same
fluorescent effect in porcelain it is necessary to increase the
fluorescence, when other pigments are increased because of light
absorption effects. The present invention, on the contrary, aims
for a maximum opalescent effect, instead of uniform UV
fluorescense. However, a minimum, but sufficient, amount of
fluorescent effect is still obtained in the restoration of the
present invention.
[0014] In accordance with the present invention, it was
surprisingly found that the transparent outer layer is responsible
for a deeper penetration of light to the fluorescent opaque layer
where the light reflects back through the more translucent outer
layer. This interaction gives a lively, natural effect, which makes
the acceptance or appearance of the restoration less dependent on
the obtaining of an exact copy of the shade of the adjacent teeth,
as is the case with traditional veneering materials.
[0015] The fluorescent material creates a glow from deep within;
the more light enters the artificial tooth, the stronger the
reflection and clarity of said tooth. The opaque layer required by
the present invention hence breaks light, reflects it and gives
fluorescence. The fluorescent materials used are excited by UV
light and send out VIS light. The light reflected and sent out by
the lower opaque layer or layers amplifies the opalescence in the
transparent upper layers.
[0016] By the present invention and particularly by the interaction
between opalescence and fluorescence, it becomes possible to
control the colour and light effects in the mouth.
[0017] The present invention will be further explained with
reference to the drawings in FIG. 1, wherein the principle of the
invention is illustrated for a preferred embodiment.
[0018] Particularly, FIG. 1 shows at the left-hand side a standard
layered restoration known from the prior art (traditional method),
and at the right-hand side a preferred embodiment of the invention.
In the traditional method most of the light that falls on the
restoration is diffusely dispersed into the ceramic. In the method
according to the present invention, the light is transferred much
deeper into the more transparent opalescent layers, and especially
the more transparent and opalescent incisal, dentin and
opaque/dentin layers and is for a great part reflected against the
strongly fluorescent opaque layer and on the strongly fluorescent
modifier, which is present between the dentin and opaque/dentin
layer, in such a way that it exits the ceramic, to give a very
"lively" and natural appearance.
[0019] That is, the present invention involves a specific layering
of porcelain on a structure of metal or ceramic to obtain a more
naturally looking opalescent and fluorescent effect by functionally
separating opalescence and fluorescence in that the opaque layer
and, if present, a modifier layer have relatively strong
fluorescence and the outer transparent layers give a strong
opalescense, and have little fluorescence. It appears that when the
veneering material was build-up in such a way a much more
acceptable blending-in process with the rest of the dentition is
experienced. The reflected light from a strongly fluorescent
modifier, when present, and opaque layer interacts with the shade
of the dentin layer, giving this effect.
[0020] In order to provide a sufficiently strong fluorescence, the
opaque layer that contains the fluorescent material should contain
said fluorescent material in a considerable amount. Preferably, the
fluorescent material is present in an amount of at least 2 wt. %,
preferably in an amount between 2 and 5 wt. %, drawn to the weight
of the porcelain material wherein it is incorporated, such as in
the opaque liner material.
[0021] Because opalescence is an optic phenomenon, caused by the
Tyndall-effect of light absorption by particle light scattering, it
is only effective in optically transparent materials. Therefore the
opaquefying effect by addition of a fluorescent must possibly be
avoided. Hence, the layers of translucent, opalescent material
should in principle not contain fluorescent material. However, the
effects of the invention are still obtained if the amount of
fluorescent material in the transparent, opalescent layers is lower
than 0.1 wt. %, drawn to the weight of the layers forming said
translucent material. Preferably, these layers contain less than
0.05 wt. % fluorescent material
[0022] The fluorescent material used can in principle be any
material that is compatible with the opaque porcelain material and
that is able to send out visible light. In a preferred embodiment,
the fluorescent material comprises and preferably consists of
yttriumoxide.
[0023] The translucent, opalescent material should preferably have
a translucency of more than 30%. In a preferred embodiment the
translucent, opalescent material is made of porcelain containing at
least 10% of an opal glass frit. Particularly good results are
obtained with transparent porcelain layers which consist of 10-100
wt.-% opal glass frit with the following composition in wt.-% drawn
to the weight of the total composition: 45-70% SiO.sub.2, 0-20%
Al.sub.2O.sub.3, 0-20% K.sub.2O, 0-15% Na.sub.2O, 0-5% CaO, 0-3%
MgO, 0-4% CeO.sub.2, 0-4% Tb.sub.2O.sub.3, 1-10% P.sub.2O.sub.5,
0-1% CaF.sub.2, 0-2% Li.sub.2O, and 0-5% Sb.sub.2O.sub.3.
Alternatively, equally good results are obtained with transparent
porcelain layers which consist of 10-100 wt.-% opal glass frit with
the following composition in wt.-%: 45-70% SiO.sub.2, 0-20%
Al.sub.2O.sub.3, 0-20% K.sub.2O, 0-15% Na.sub.2O, 0-5% CaO, 0-3%
MgO, 0-4% CeO.sub.2, 0-4% Tb.sub.2O.sub.3, 0-2% P.sub.2O.sub.5,
5-15% CaF.sub.2, 0-2% Li.sub.2O, and 0-5% Sb.sub.2O.sub.3.
[0024] The dental restoration of the present invention comprises at
least one opaque layer that contains fluorescent material, and more
to the surface of the dental restoration other porcelain layers
which are translucent and opalescent. These other porcelain layers
comprise at least one incisal layer, at least one dentin layer, and
optionally at least one opaque/dentin layer. See in this respect,
FIG. 1.
[0025] In a particularly preferred embodiment, the dental
restoration of the invention has a modifier containing fluorescent
material present in an area between the incisal layer or layers and
the dentin layer or layers and/or between the dentin layer(s) and
the opaque/dentin layer(s). This modifier makes it possible to
provide an even better adapted natural looking tooth.
[0026] Suitably, the modifier layer contains at least 0.1 wt. %
yttriumoxide as fluorescent applied between the dentin and the
incisal layer.
[0027] In accordance with this aspect of the present invention,
when a transparent outer layer is used and when an internal highly
fluorescent material is used in-between the incisal and dentin
layer, the process of blending-in with the remaining dentition
takes place easily, even if the shade is not exactly copied. The
shade of the modifier layer interacts with the basic dentin
material to give a play of light and shades, which can also be seen
when teeth are observed under different light conditions (morning,
noon or evening; spring, summer, autumn or winter).
[0028] In the porcelains used to be applied to a substructure of
either ceramic or a metal or metal alloy, colouring agents can be
incorporated under the precondition that these do not interfere
with the interaction between opalescence and fluorescence.
[0029] In the method of the present invention, the preferred opal
glass frit containing composition for the translucent layers to be
applied, preferably have a firing temperature that is not lower
than 25.degree. C. than the firing temperature of the basic
veneering material on which it is applied. This should secure that
the two materials do not react with each other.
[0030] Finally, the present invention foresees in an easy-to-use
ceramic system build-up for use in the method of the present
invention. This easy-to-use system ensures that the dental
technician achieves the benefits and advantages mentioned for the
invention without exactly needing to know all the specific effects
of each separate layer. This system is embodied in TABLE A and is
based on the colour indications used by the dental technicians
(A1-D4). In this TABLE A, the action i dentin refers to the colour
of the modifier layer used in the preferred embodiment of the
invention, and the x-tra-incisals refer to the high opalescent
layers according to the invention.
[0031] The present invention will now be further illustrated by
means of the following non-limiting examples. In these examples
describing the method and products of the present invention the
following basis ceramic compositions were used. The first ceramic
composition used is veneering porcelain C as described in U.S. Pat.
No. 5,453,290. This product is sold under the tradename "Carrara"
(registered tradename of Elephant Dental B.V., Hoorn, The
Netherlands). The second ceramic material used is veneering
porcelain A used for standard ceramic alloys and is sold under the
name "Antagon" (registered trade name Elephant Dental B.V., Hoorn,
The Netherlands). Another basis veneering material S is sold under
the name "Sintagon" (registered trade name Elephant Dental B.V.,
Hoorn, The Netherlands) and is used for the veneering of Y-PTZ
zirconia structures. In table 1, the composition of the three basic
veneering materials is given.
1TABLE 1 Composition in wt.-% of three basic veneering materials
Component Material C Material A Material S SiO.sub.2 65.1 64.1 67.0
Al.sub.2O.sub.3 12.5 14.2 11.0 K.sub.2O 11.6 11.1 10.1 Na.sub.2O
7.2 6.6 8.6 CaO 0.7 1.1 0.8 BaO 0.9 0.4 1.3 Sb.sub.2O.sub.3 1.5 1.4
2.1 Li.sub.2O 0.3 0.2 0.2 F.sub.2 0.6 0.6 0.0 Translucency (%) 520
nm 1x 68.0 73.0 80.0 Translucency (%) 520 nm 5x 65.0 70.0 80.0
Firing temperature, .degree. C. 860 900 830 Glass transition
temperature, .degree. C. 460 460 480 TEC .mu.m/m.K (25 to
400.degree. C.) 13.7 12.4 9.4 TEC .mu.m/m.K (25 to 500.degree. C.)
14.7 12.7 9.7
[0032] The translucency values in the present application are
determined using light of a wavelength of 520 nm that passes
through a disk of material with a thickness of 2.20-2.30 mm. The
references "1.times." and "5.times." in respect of the
translucencies refer to the number of firing steps, required to
apply the materials. The TEC is the thermal extension coefficient,
which is determined either in the temperature range of
25-400.degree. C. or in the range of 25-500.degree. C. as described
in U.S. Pat. No. 5,453,290.
EXAMPLES 1 AND 2
[0033] To obtain an opalescent effect, basic veneering materials A,
C and S are blended with an opal glass frit (vide infra) in a
proportion of 20 to 40 weight percent. The translucency of the
basic veneering materials is inversely related to the expansion of
the frit, which is caused by the presence of a crystalline leucite
phase. Basic material A contains approximately 22 vol. % leucite
and basic material C about 30 vol.-% leucite, while composition S
is leucite-free.
[0034] Two different opal glass frits were produced by blending
several mixtures of powdered metal oxides, carbonates or nitrates
in the appropriate proportions. The blended powders were fused to
form a glass melt followed by quenching, drying, ball milling and
seeving using means known in the art (Table 2). The powders formed
from either one of these two glasses having a particle size of less
than 106 .mu.m are pigmented to obtain a toothlike appearance.
2TABLE 2 Composition in wt.-% of two opalescent glass frits.
Component Ex. 1 Ex. 2 SiO.sub.2 62.0 62.6 Al.sub.2O.sub.3 10.8 11.2
K.sub.2O 9.6 7.6 Na.sub.2O 7.4 7.6 CaO 3.3 0.1 MgO 2.0 0.0
CeO.sub.2 1.8 0.0 Tb.sub.2O.sub.3 1.9 2.3 P.sub.2O.sub.5 2.0 0.0
CaF.sub.2 0.0 9.9 Translucency (%) 520 nm 1x 57.8 66.3 Translucency
(%) 520 nm 5x 49.3 56.3 Opalescence 1x 17.5 24.7 Opalescence 5x
20.8 24.7 Firing temperature, .degree. C. 900 835 Glass transition
temperature, .degree. C. 590 525 TEC .mu.m/m.K (25 to 400.degree.
C.) 8.5 9.7 TEC .mu.m/m.K (25 to 500.degree. C.) 8.8 9.3
[0035] The opalescence is measured as the calculated difference
(.DELTA.C) between the a*- and b*-values according to the CIELAB
colour space, whereby the sample is measured against a white and
against a black background using an artificial D65 light source.
Particularly, the opalescence is calculated as the square root of
[(a*).sup.2+(b*).sup.2].
[0036] The opalescence found for example 1 is based on the
crystallisation of a fine phosphate phase, while in example 2
calcium fluoride crystals with an average size of 300 nm are
generating the opalescence.
[0037] Both opalescent glass frits had the same or a better
opalescence after they were fired 5 times at their firing
temperature. However, their translucency suffers from the light
absorption caused by the increase in crystalline phase volume.
COMPARATIVE EXAMPLE 3
[0038] In the present example, dental restorations prepared
according to the traditional method and using the method of the
present invention with the materials described in examples 1 and 2
are compared. The results are depicted in Table 3.
3TABLE 3 Composition of ceramic C of transparent, incisal,
modifier, and opaque ceramic with opal frit Example 1 and Example 2
Component Transparent Incisal Modifier Opaque Traditional Wt.-%
Y.sub.2O.sub.3 0.05 0.05 0.05 0.0 Translucency (%) 520 nm 1 60.0
25.0 25.0 0.0 Translucency (%) 520 nm 5 60.0 25.0 25.0 0.0
Fluorescence 8 8 4 0.0 Opalescence 1x 0 10.0 0 N.A. Opalescence 5x
0 10.0 0 N.A. Method of Wt.-% Y.sub.2O.sub.3 0.03 0.05 0.4 3.0
invention Translucency (%) 520 nm 1 60.0 40.0 25.0 0.0 (Ex. 1 opal
Translucency (%) 520 nm 5 58.0 40.0 25.0 0.0 frit, 29%)
Fluorescence 2 4 10 Opalescence 1x 10.4 8.0 0 N.A. Opalescence 5x
12.7 8.0 0 N.A. Method of Wt.-% Y.sub.2O.sub.3 0.03 0.05 0.4 3.0
invention Translucency (%) 520 nm 1 62.4 40.0 25.0 0.0 (Ex. 2 opal
Translucency (%) 520 nm 5 60.7 40.0 25.0 0.0 frit, 29%)
Fluorescense 2 4 10 Opalescense 1x 11.7 8.0 0 N.A. Opalescense 5x
8.1 6.0 0 N.A.
[0039] The degree of fluorescence is determined using a
fluorescence indicator which was specially adjusted for this
purpose. The indicator contains 10 discs numbered from 1 to 10
whereby disc 1 has the lowest concentration of fluorescent and disc
10 the highest concentration of fluorescent material.
[0040] Opal glass frit ex. 1 gave an increase in opalescence after
5 firings.
[0041] The firing temperature of basic veneering material C is
860.degree. C. and this is 40.degree. C. lower than the firing
temperature of ex. 1. The likelyhood that ex. 1 will react with the
basic veneering material C is therefore small.
[0042] Opal glass frit ex. 2 gave a decrease after repeated firings
because the firing temperature is 25.degree. C. lower than the
basic veneering material C.
[0043] For both opal frits the translucency decreases after 5
firings due to a decrease of translucency in the basic veneering
material.
COMPARATIVE EXAMPLE 4
[0044] In the present example, dental restorations prepared
according to the traditional method and using the method of the
present invention with the materials described in examples 1 and 2
are compared. The results are depicted in Table 4.
4TABLE 4 Composition of ceramic A of transparent, incisal,
modifier, and opaque ceramic with opal frit exp.1 and exp. 2
Component Transparent Incisal Modifier Opaque Traditional Wt.-%
Y.sub.2O.sub.3 0.05 0.05 0.05 0.0 Translucency (%) 520 nm 1 50.0
25.0 25.0 0.0 Translucency (%) 520 nm 5 50.0 25.0 25.0 0.0
Fluorescence 8 8 4 0.0 Opalescence 1x 0 10.0 0 N.A. Opalescence 5x
0 10.0 0 N.A. Method of the Wt.-% Y.sub.2O.sub.3 0.03 0.05 0.4 3.0
invention Translucency (%) 520 nm 1 70.2 40.0 25.0 0.0 (Ex. 1 opal
Translucency (%) 520 nm 5 66.3 40.0 25.0 0.0 frit, 29%)
Fluorescence 2 4 10 Opalescence 1x 10.7 8.0 0 N.A. Opalescence 5x
14.3 8.0 0 N.A. Method of the Wt.-% Y.sub.2O.sub.3 0.03 0.05 0.4
3.0 invention Translucency (%) 520 nm 1 65.3 40.0 25.0 0.0 (Ex. 2
opal Translucency (%) 520 nm 5 67.0 40.0 25.0 0.0 frit, 29%)
Fluorescence 2 4 10 Opalescence 1x 11.0 8.0 0 N.A. Opalescence 5x
7.7 6.0 0 N.A.
[0045] Opal glass frit ex. 1 gave an increase in opalescence after
5 firings. The firing temperature of basic veneering material C is
900.degree. C. and this the same as the wring temperature of ex 1.
The likelyhood that ex 1 will react with the basic veneering
material A is therefore small.
[0046] Opal glass frit ex. 2 gave a strong decrease after repeated
firings because the firing temperature is 65.degree. C. lower than
the basic veneering material A.
COMPARATIVE EXAMPLE 5
[0047] In the present example, dental restorations prepared
according to the traditional method and using the method of the
present invention with the materials described in examples 1 and 2
are compared. The results are depicted in Table 5.
5TABLE 5 Composition of ceramic S of transparent, incisal,
modifier, and opaque ceramic with opalfrit exp.1 and exp. 2
Component Transparent Incisal Modifier Opaque Traditional Wt.-%
Y.sub.2O.sub.3 0.05 0.05 0.05 0.0 Translucency (%) 520 nm 1 80.0
25.0 25.0 0.0 Translucency (%) 520 nm 5 80.0 25.0 25.0 0.0
Fluorescence 8 8 4 0.0 Opalescence 1x 0 10 0 N.A. Opalescence 5x 0
10 0 N.A. New method Wt.-% Y.sub.2O.sub.3 0.03 0.05 0.4 3.0 (Ex. 1
opalfrit, Translucency (%) 520 nm 1 72.0 40.0 25.0 0.0 29%)
Translucency (%) 520 nm 5 70.0 40.0 25.0 0.0 Fluorescence 2 4 10
Opalescence 1x 10.4 9.0 0 N.A. Opalescence 5x 12.7 10.0 0 N.A. New
method Wt.-% Y.sub.2O.sub.3 0.03 0.05 0.4 3.0 (Ex. 2 Translucency
(%) 520 nm 1 68.0 40.0 25.0 0.0 opalfrit, 29%) Translucency (%) 520
nm 5 66.0 40.0 25.0 0.0 Fluorescence 2 4 10 Opalescence 1x 11.7 8.7
0 N.A. Opalescence 5x 12.8 9.7 0 N.A.
[0048] Both opal glass frits ex. 1 and ex. 2 gave an increase in
opalescense after 5 firings. The firing temperature of basic
veneering material S is 830.degree. C., which for ex. 1 is
70.degree. C. and for ex. 2 30.degree. C. lower than the firing
temperature basic veneering material S. The likelyhood that ex 1
and ex. 2 will react with the basic veneering material S is
therefore small.
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