Dental porcelains

Details Dental porcelains Dental porcelains

2000-06-29

2002-08-06

Koslow, C. Melissa (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Dental

C433S202100, C433S212100, C433S206000, C501S017000, C501S018000, C501S021000, C501S025000, C501S026000, C501S032000, C501S057000, C501S067000, C501S070000

Reexamination Certificate

active

06428614

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to low fusing high-expansion dental porcelain especially useful for the fabrication of both all-ceramic and porcelain-fused-to-metal (PFM) restorations.
BACKGROUND OF THE INVENTION
Porcelains are typically designed to be used in the manufacture of either all-ceramic dental restorations or in PFM restorations, but are not normally functional with both types of restorations due to the differences in properties of ceramics and metals. One such porcelain, OPC® Low Wear™ porcelain, available from Jeneric/Pentron Inc., Wallingford, Conn. and covered in copending, commonly assigned patent application Ser. No. 09/133,582 filed Aug. 13, 1998, now U.S. Pat. No. 6,120,591, which is hereby incorporated by reference, was initially designed to be used as overlay for pressed all-ceramic restorations as well as for the fabrication of porcelain jacket crowns and veneers. However, OPC®Low Wear™ porcelain is not currently used for PFM restorations despite its wear resistance, forgiveness to natural dentition and strength being superior to those of conventional PFM porcelains as shown in the Table 1 below:
TABLE 1
OPC ®
Low Wear ™
Conventional Porcelain
Property
Porcelain
for PFM
Leucite average grain
About 2-3
About 5-8
Size, &mgr;m
Leucite volume fraction, %
35-40
20-25
Enamel wear*, × 10
−2
mm
2
7.69 ± 3.20
18.23 ± 5.20 
Wear of ceramics*, × 10
−2
0.16 ± 0.04
0.49 ± 0.11
mm
3
CTE, 10
−6
/° C., 25° C.-
About 17
About 13
500° C.
The major obstacle preventing use of the OPC® Low Wear™ porcelain in PFM restorations is the absence of an opaque/alloy combination compatible with this porcelain having relatively high expansion of about 17×10
−6
/° C. (25° C.-500° C.).
There exists a Golden Gate System™ for PFM restorations available through Degussa™ (Dental Division, South Plainfield, N.J.) which combines Duceragold™ porcelain and Degunorn™, type IV crown and bridge alloy (CTE=16.4×10
−6
/° C., 25° C.-500° C.). This system requires rather tedious multistep alloy preparation procedures including a necessary wash bake step prior to application of the opaque; and an excessively long (16-20 min) and complex first dentine bake to assure proper bonding and compatibility of the Duceragold™ porcelain to the Degunorm™ alloy. In particular, the cooling segment (3-4 min between 720° C. and 680° C.) in the first dentine bake is required by the manufacturer to grow additional leucite and may be an indication of instability of leucite in this porcelain. The following Table 2 below sets forth the various properties of the Duceragold™ porcelain.
TABLE 2
Duceragold ™
Firing Temperature, ° C.
770-790
Glass Transition
490
Temperature, ° C.
Softening Temperature, ° C.
595
CTE 25°-500° C., 10
−6
/° C.
15.8
Recommended alloy
Degunorm
Alloy CTE 25° C.-500° C.,
16.4
10
−6
/° C.
U.S. Pat. No. 5,453,290 to Van der Zel is directed to a dental porcelain for use with a dental alloy. The porcelain described therein must be fabricated from three frits, making it more difficult and costly to control the expansion and the glass transition temperature of the final product. Moreover, the CTE of the porcelain must be below the CTE of the alloy by 0.5-1.5 limiting the components to be used together. There is a need to provide a porcelain-fused-to-metal system for dental restorations having simple manufacturing procedures. It is desirable to provide a porcelain that is compatible with alloys of relatively high expansion. It is desireable to provide a two-frit porcelain for use in PFM restorations.
SUMMARY OF THE INVENTION
These and other objects and advantages are accomplished by opaque porcelains for use with metal cores in the manufacture of PFM restorations. The porcelains exhibit a coefficient of thermal expansion (CTE) substantially equal to or slightly above the CTE of the metal to which it is applied. In a preferred embodiment, the porcelains exhibit a CTE equal to or up to about 1.0×10
−6
/° C. higher than the dental alloys to which they are applied as the opaque. The porcelains are fabricated from a mixture of two frit compositions. A high expansion, leucite containing frit is combined with a low fusing glass frit to provide a porcelain having an expansion in the range of 16.9 to about 18.5×10
−6
/° C. in the temperature range of 25°-500° C. By combining two frits, the expansion and fusing temperature can be controlled to the values stated above.
DESCRIPTION OF THE INVENTION
The invention relates to a porcelain material for use in all-ceramic restorations and PFM restorations. The porcelains exhibit a coefficient of thermal expansion (CTE) substantially equal to or slightly above the CTE of the metal to which it is applied. Preferably, the porcelains exhibit a CTE equal to or up to about 1.5×10
−6
/° C. higher than the dental alloys to which they are applied as the opaque, and more preferably equal to or up to about 1.0×10
−6
/° C. The porcelains are compatible with metals having coefficients of thermal expansion (CTE) in the range of from about 15.5 to about 17×10
−6
/° C. in the temperature range from 20° to 500° C. The porcelains exhibit CTEs in the range of about 16.9 to about 18.5 in the temperature range from 20° to 500° C., and preferably in the range of about 17 to about 17.5×10
−6
/° C. in the temperature range from 20° to 500° C. The porcelains are fabricated from a mixture of two frit compositions. A high expansion, leucite containing frit is combined with a low fusing glass frit to provide a porcelain having an expansion in the range of 16.9 to about 18.5×10
−6
/° C. in the temperature range of 25°-500° C. It is essential to this invention that both the high expansion and the low fusing components of the two-frit mixture exhibit a low glass transition temperature (GTT). It is extremely important that the low fusing component used in the opaque formulation exhibits a GTT lower than about 415° C. By combining two frits, the expansion and firing temperature can be controlled to the values stated above. Opaque porcelains herein having pigments exhibit a coefficient of thermal expansion of average value of about 17×10
−6
/° C. in the temperature range of 25°-500° C. Opaque porcelains without pigments, i.e., white opaques, exhibit coefficients of thermal expansion in the higher end of the range, such as about 17.5 to about 18.5×10
−6
/° C. in the temperature range of 25°-500° C.
Table 3 below shows the compositional ranges of the porcelains for use in the invention.
TABLE 3
Body and
Incisal
Opaque
Opaque
Opaque
Opaque
Porcelain
Porcelain (1)
Porcelain (2)
Porcelain (3)
Porcelain (4)
(by weight
(by weight
(by weight
(by weight
(by weight
percent)
percent)
percent)
percent)
percent)
SiO
2
about 59-
about 59-
about 59-
about 48-
about 48-
about 65
about 65
about 65
about 65
about 65
B
2
O
3
X
X
X
0-about 0.7
0-about 0.7
Al
2
O
3
about 10-
about 10-
about 10-
about 10-
about 10-
about 15
about 15
about 15
about 15
about 15
ZnO
X
X
X
0-about 5
0-about 5
CaO
about 0.5-
about 0.5-
about 0.5-
about 0.5-
about 0.5-
about 2
about 2
about 2
about 2
about 2
MgO
X
X
X
0-about 2
0-about 2
BaO
X
X
X
0-about 1
0-about 1
Li
2
O
about 1.5-
about 1.5-
about 1.5-
about 1.5-
about 1.5-
about 3
about 3
about 3
about 3
about 3
K
2
O
about 15-
about 15-
about 12-
about 14-
about 15-
about 17
about 17
about 17
about 17
about 17
Na
2
O
about 4-
about 4-
about 4-
about 4-
about 4-
about 6
about 6
about 6
about 6
about 6
TiO
2
X
X
X
0-about 2
0-about 2
ZrO
2
X
X
X
0-about 17
0-about 17
CeO
2
X
X
X
0-about 1
0-about 1
F
about 0.4-
about 0.4-
about 0.4-
about 0.4-
about 0.4-
about 1
about 1
about 1
about 1
about 1
Ta
2
O
5
—
X
X
0-about 2
0-about 2
SnO2
—
—
—
0-about 18
0-about 18
ZrSiO
4
—
—
—
0-about 7
—
*Opacifiers
0-about 1
about 13-
about 10-
—
—
about 20
about 20
**Pigments
0-about 5
about 2-
—
—
—
about 13
*Opacifiers, Al
2
O
3
, SnO
2
, TiO
2
, ZrO
2
, ZrSiO
4
, ZnO,

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