Dental porcelains

Details Dental porcelains Dental porcelains

2002-06-12

2004-07-13

Koslow, C. Melissa (Department: 1755)

Compositions: coating or plastic

Coating or plastic compositions

Dental

C501S014000, C501S011000, C501S017000, C501S018000, C264S016000, C264S019000, C264S020000, C433S202100, C433S203100, C433S201100, C433S212100

Reexamination Certificate

active

06761760

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
Conventional
OPC ® Low Wear ™
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
mm
3
0.16 ± 0.04
0.49 ± 0.11
CTE, 10
−6
/° C., 25° C.-500° C.
About 17
About 13
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°-600° C., 10
−6
/° C.
15.8
Recommended alloy
Degunorm
Alloy CTE 25°-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°-600° C. By combining two frits, the expansion and fusing temperature can be controlled to the values stated above.


REFERENCES:
patent: 5308391 (1994-05-01), Komma et al.
patent: 5453290 (1995-09-01), Van Der Zel
patent: 5653791 (1997-08-01), Panzera et al.
patent: 6120591 (2000-09-01), Brodkin et al.
patent: 6428614 (2002-08-01), Brodkin et al.
patent: 2070691 (1992-12-01), None
patent: 0 272 745 (1987-12-01), None
patent: 0 518 454 (1992-05-01), None
patent: 0 870 479 (1998-10-01), None
patent: WO 95/11866 (1995-05-01), None
patent: WO 99/18910 (1999-04-01), None
PCT International Search Report with mail date of Nov. 20, 2000.
International Preliminary Examination Report with mail date of Oct. 22, 2001.
PCT Written Opinion with mail date of Jul. 26, 2001.
“Clay and Vocabulary Concepts.” [http://scitech.stisd.net/minkc/clayterms.html]. Jan. 15, 2002.
Perkins, W., Ceramic Glossary, 1984, The American Ceramic Society, pp. 33 & 52.
Skinner, E. W., Phillips, R. W., The Science of Dental Materials, W.B. Saunders Company, 1980, pp. 270 & 271.

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