J Korean Acad Prosthodont.  2011 Jan;49(1):73-79. 10.4047/jkap.2011.49.1.73.

The effect of repeated firings on the color of zirconia-based all-ceramic system

• Jang JE
• Kim MH
• Yun MJ
• Jeong CM
• Jeon YC

• KMID: 2000286
• DOI: http://doi.org/10.4047/jkap.2011.49.1.73

Abstract

PURPOSE
The aim of this study was to evaluate the effect of repeated firings on the color of zirconia restoration with different shading method.
MATERIALS AND METHODS
Three different types of zirconia frameworks (adding metallic pigments to the initial zirconia powder before sintering (Group NM), dipping the milled frameworks in dissolved coloring agents (Group KI), or application of liner material to the sintered white frameworks (Group KW) were used to support A3 shade dentin porcelain. Repeated firings (3, 5, or 7) were performed, color differences among ceramic specimens were measured using a colorimeter. Repeated measurements analysis of variance (ANOVA) was used to analyze the data for significant difference. The Tukey Honestly Significant Different (HSD) test was used to perform multiple comparisons (alpha = .05).
RESULTS
1. L*a*b* values of the ceramic systems were affected by the number of firings (1, 3, 5 or 7 firings) (P < .001) and shading methods (P < .001). 2. As the number of firings increased, the L* (for all groups) and a* value (for KW and NM groups) decreased and the b* value(for all groups) increased. 3. The mean color differences caused by repeated firings were perceptible (DeltaE > 1) for group KW and KI fired after 3 times, except for group NM fired after 7 times. 4. In order of decreasing DeltaE value fired after 7 times, the values were group KI(DeltaE = 2.26) > group KW (DeltaE = 1.47) > group NM (DeltaE = 1.08) (P < .001).
CONCLUSION
Repeated firings influenced the color of the zirconium-oxide all-ceramic specimens with different shading methods.

Keyword

Zirconia; Shading; Repeated firings; Color

MeSH Terms

Ceramics
Coloring Agents
Dental Porcelain
Dentin
Fires
Humans
Zirconium
Ceramics
Coloring Agents
Dental Porcelain
Zirconium

Figure

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  Fig. 1. Samples of all groups: Left, After sintering zirconia. Right, After veneering porcelain.

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  Fig. 2. ShadeEye-NCC® dental chroma meter (Shofu Dental, Kyoto, Japan).

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  Fig. 3. Means of L∗ for different number of firings.

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  Fig. 4. Means of a∗ for different number of firings.

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  Fig. 5. Means of b∗ for different number of firings.

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