LOW-FUSING TEMPERATURE PORCELAIN

PORCELAINE A BASSE TEMPERATURE DE FUSION

English Abstract

A low-fusing temperature porcelain composition for use in dental prostheses is
disclosed having a fusing temperature of about 700
°C ~ 50 °°C and a coefficient of thermal expansion
compatible witha substrate of metal or ceramic. The composition includes, in
weight
percent of the composition, SiO2 at 57-61, Al2O3 at 6.5-11.5, Na2O at 10-11,
K2O at 8-16, Li2O at 1-3, CaO at 1.5-4, BaO at 1.5-2.5, CeO2
at 0.5-2, and Tb2O3 at 0.5-2.

French Abstract

Composition de porcelaine à basse température de fusion destinée à être utilisée dans des prothèses dentaires, qui possède une température de fusion d'environ 700 DEG C +/- 50 DEG C et un coefficient de dilatation thermique compatible avec un substrat de métal ou de céramique. Ladite composition comporte, en pourcentage en poids, SiO2 à 57-61, Al2O3 à 6,5-11,5, Na2O à 10-11, K2O à 8-18, Li2O à 1-3, CaO à 1,5-4, BaO à 1,5-2,5, CeO2 à 0,5-2 et Tb2O3 à 0,5-2.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A low-fusing temperature porcelain composition for
use in a dental prosthesis, consisting essentially of, in
weight percent of the porcelain composition:
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said porcelain having a fusing temperature of about 700°C ~
50°C and a coefficient of thermal expansion compatible with a
substrate of metal or ceramic suitable for a dental
prothestic.
2. The porcelain of claim 1, having a coefficient of
thermal expansion of about 12-13 µm. K -1 measured at 20° to
500°C.
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3.~The porcelain of claim 1, further comprising up to
about 2 weight percent by weight of B2O3.
4.~A low-fusing temperature porcelain composition for
use in a dental prosthesis, comprising:
a glass frit, having a processing temperature of about
705°C and a coefficient of thermal expansion of about 12-13
µm.K -1 measured at 20° to 500°C and, in weight percent
(~ 0.5) of the composition:
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5.~A dental prosthesis, comprising the low-fusing
temperature porcelain of claim 4, fused to a ceramic
substrate.
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6. A dental prosthesis, comprising the low-fusing
temperature porcelain of claim 1, fused to a substrate of
metal or ceramic.
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Description

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WO 96118373 PCTIUS95/15626
LOW-FUSING TEMPERATURE PORCELAIN
FTFT,n OF THE TNVRNTTON
The invention relates to porcelains used in dental
prostheses. More particularly the--invention relates to
a low-fusing temperature porcelain suitable for use in
combination with metal or porcelain substrates.
A dental prosthesis often comprises a crown or
bridge restbration in which a dental porcelain is fused
to a supporting metal or ceramic substrate. Dental
porcelains are generally a mixture of glass frit
components or-natural feldspars or the like. There are
a number of, key considerations in selecting frit
components to form a porcelain that will be compatible
with the selected substrate.
For example, the porcelain must have a coefficient
of thermal expansion that is as close ~s possible to _
that of the substrate. Otherwise, a porcelain fused to

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the substrate will tend to crack and separate from its
supporting structure.
Another--key factor in selecting a porcelain
component is its effect upon processing temperature of
the porcelain; that is, the temperature that must be
utilized in fusing the porcelain to the substrate.
Fusing temperatures of porcelain materials of the prior
art have generally been on the order of 900°C-or higher.
Such elevatedtemperatures limit the composition of the
substrate that may be used since some alloys or ceramic
compositions will distort or otherwise suffer
detrimental compositional changes under such processing
conditions.
In selecting glass components and their amounts in
the porcelain composition to achieve low-fusing
temperatures and appropriate coefficients of thermal
expansion, care also must be exercised to insure that
the changes in composition do not otherwise adversely
effect the qualities of the resulting fired porcelain
with respect to its performance in a dental
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WO 96118373 PCTIUS95I15626
environment. Such characteristics of concern are acid
resistance, hardness, flexural strength and the like.
Thus, heretofore, it has remained the goal of
researchers to- produce a porcelain glass frit
a
composition that has a low-fusing or processing
temperature and a coefficient of thermal expansion such--
that it can be used in combination with both metal and
porcelain substrates in dental prostheses. Such a
composition would have improved versatility for use in
making, repairing or improving crowns, bridges, linings
for dentures or as finish porcelains-and stains.
A low-fusing temperature porcelain composition for
' use in a dental prosthesis is provided. The porcelain
composition comprises:
Frit Components Weight Percent
Si02 57-61
A1Z03 6.5-11.5
Na20 10-I2
Kz0 8-16
LizO 1-3
Ca0 1.5-4
Ba0 1.S-2-.5
Ce02 0.5-2
' TbzO; 0.5-2
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The porcelain -of the invention has a fusing
temperature of -about 700°C ~ 50°C-and a coefficient of
thermal expansion compatible with a substrate of metal
or ceramic. Preferably, the coefficient of thermal
expansion is about 12-13 wm.K 1 [20 to 500°C).
The invention is a low-fusing temperature
porcelain composition that is a mixture of oxides such
that the -resulting frit has a fusing temperature of
about 700°C + 50°C and -a coefficient of thermal
expansion of 12-13 ~tm.R 1 [20 to 500°C] . The low fusing
porcelain may be employed in dental crowns, bridges,
restorations and dentures wherein- it is fused to a
substrate or coping of metal or- conventional
porcelains, such as Ceramco II~, and dental alloy
copings, such as Ceramco- II~ Silver, both manufactured
by Dentsply International Inc. of York, Pennsylvania.
The compositional range for the low-fusing
temperature dental porcelains of the invention, having
processing temperatures of less than about 705°C and a
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WO 96118373 ' PCTIC1S95/15626
coefficient of f.hermal expansion (CTE) of 12-13 ~m.K 1
[20 to 5.00°CI. is -a mixture of oxides having the
following composition:
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Table-1
Oxide Weight Percent
SiOz 57-61
A1203 6.5-11.5
NaZO 10-12
K20 8-lfi
Li20 1-3
Ca0 1.5-4
Ba0 1.5-2.5
Ce02 0.5-2
Tbz03 0.5-2
An optional ingredient is B203 at about 0-2°s by
weight of the composition.
The _- following examples describe preferred
compositions and characterize the resulting dental
porcelain qualities.
Example 1
A single glass, frit, low temperature fusing
porcelain is made by combining and --fusing oxides, and
then forming a pulverized mixture,-as-is well known in

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WO 96118373 PCTfUS95/15626
the art, of the composition indicated in Table 1. The
resulting porcelain has a firing temperature of 705°C
and a CTE of 12.5 Pm.K 1. Samples of the resulting
mixture have the characteristics and properties shown
in Table 2.
Table 2
Oxide Weight Percent
Ex.l
SiO~ 59
A1z03 7
Na20 10.5
K20 13 . 5
Li20 2
Ca0 2
Ba0 2
8203 2
Ce02 1
Tb40y 1
Total 100
CTE ()xm.K
1 12.5
(30-500C) 705
Firing 1300
Temp.
(C)
(F)
Samples of the low-fusing glass of the invention
are also characterized by their low chemical
solubility. Chemical solubility was determined by
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W0 96118373 PCTlUS95115626
boiling the porcelain samples in acetic acid for
sixteen hours. The maximum allowable weight loss per
ISO standards is 1. 0 ug/mm' . The measured weight loss
of the glass frit of example 1 of the. invention is 0.26
~g/mm'. The weight loss of a competitive low-fusing
porcelain - in the marketplace (Durceram-LFC,
manufactured by Degussa of Germany is 0.47 ~g/mm2.
EXAMPLES 2-4
Low-fusing porcelains of the invention are made in
the same manner as Example 1, having the composition
indicated in -'Table 3 below, and the desired
characteristics within the scope ofthe invention.
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W0 96118373 PCT/US95/15626
Table 3
Oxide Weight Percent
Ex.2 Ex.3 Ex.4
Si02 59 59 57.7
AlzO~ 7 7 11.5
NazO 10 10 12
K20 16 14 8
Li20 2 2 3
Ca0 2 2 3.8
Ba0 2 2 2
Bz03 - 2 -
Ce02 1 1 1
Tb,O~ 1 1 1
Total 100 100 100
CTE (~tm.K'')
(30-500C) 12.6 12.5 12.6
Firing Temp.
(C) 705 705 690
(F) - 1300 1300 1270
The examples ofthe invention when utilized in
forming dentalprostheses are characterized by having
an easier polishability due to the reduced hardness
compared to conventional porcelains. The amounts of
Ce02 and Tbz03 are adjusted to. provide desired
fluorescence characteristics, ranging from bluish to
white fluorescence.
Variations and modifications of the composition
are within those skilled in the art, for example, to
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adjust the coefficient of thermal expansion to match
the desired value of 12-13 ~tm.R 1, depending upon the
substrate to which the porcelain will be applied.
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