Colorimetric analysis of opaque porcelain fired to different base metal alloys used in metal ceramic restorations.
BACKGROUND
The popularity of base metal alloys has considerably increased in recent years because of their superior mechanical properties as well as the high cost of noble alloys. However, there is disagreement about their effect on the opaque porcelain color and the color differences among base metal alloys.


OBJECTIVE
The purpose of this in vitro study was to determine and compare the influence of various commercially available base metal alloys (excluding titanium-based systems) on the resulting color of opaque porcelain with the use of a colorimetric device.


METHODS
Fourteen different types of Ni-Cr and 3 different types of Co-Cr porcelain bonding alloys were selected with a Au-Pd alloy (V-Delta SF) as the control group for colorimetric measurements and determination of color shift after opaque application. Shade B1 of an opaque porcelain (IPS d.SIGN Opaquer) was applied (0.1 mm) to all specimens (16 mm x 1 mm). The color coordinates of each specimen were measured with a chromameter. The data were displayed in L*, a*, and b* values according to the CIELAB system, and the color differences (DeltaE) between base metal alloys and the control group were calculated. Data were statistically analyzed with 1-way ANOVA (alpha=.05). The ANOVA was followed by Dunnett's multiple comparison test for comparisons with the control group to determine specifically which groups were significantly different from the control group.


RESULTS
The L* value of only 1 base metal alloy was significantly different from the control group (P<.001). All base metal alloy groups except 3 had a* values which were significantly different from the control group a* value (P=.001 for Rexillium III, P=.008 for Heracles N, and P<.001 for the remaining 12 alloys), whereas only 3 base metal alloys were not statistically significantly different from the control group in the means of b* values (P<.001). All base metal alloys to which opaque porcelain was applied had significantly different DeltaE values in comparison with the control group (P<.001).


CONCLUSIONS
The data of the study indicated that a 0.1-mm-thick layer of opaque porcelain applied on the Ni-Cr and Co-Cr alloys did not reliably reproduce the color of opaque porcelain. However, within the limitations of this study, the color differences of base metal alloys measured according to the control group are within clinically acceptable limits (DeltaE<3.5).
Ozcelik
Tuncer Burak
TB
Department of Prosthodontics, Faculty of Dentistry, Baskent University, Ankara, Turkey.
Yilmaz
Burak
B
Ozcan
Isil
I
Kircelli
Cem
C
D000537:Aluminum Oxide / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry*; D003116:Color; D003124:Colorimetry; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D045662:Dental Etching / Q000379:methods; D003776:Dental Porcelain / Q000737:chemistry*; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry; D013499:Surface Properties
D002858:Chromium Alloys; D003722:Dental Alloys; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D003776:Dental Porcelain; D010165:Palladium; D000537:Aluminum Oxide