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

Jung-Eun Jang; Mu-Hyon Kim; Mi-Jung Yun; Chang-Mo Jeong; Young-Chan Jeon

doi:10.4047/jkap.2011.49.1.73

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Jang, Kim, Yun, Jeong, and Jeon: The effect of repeated firings on the color of zirconia-based all-ceramic system

ORIGINAL ARTICLE

J Korean Acad Prosthodont 2011;49(1):73-79.

Published online: 18 December 2011

DOI: https://doi.org/10.4047/jkap.2011.49.1.73

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

Jung-Eun Jang, MSD, DDS, Mu-Hyon Kim, MSD, DDS, Mi-Jung Yun, MSD, DDS, Chang-Mo Jeong, MSD, DDS, PhD, Young-Chan Jeon, MSD, DDS, PhD^∗

Department of Prosthodontics, School of Dentistry, Pusan National University, Yangsan, Korea

∗Corresponding Author: Young-Chan Jeon Department of Prosthodontics, School of dentistry, Pusan National University, Beomeo-ri, Mulgeum-eup, Yangsan, 626-870, Korea +82 55 360 5130: e-mail, jeonyc@paran.com

Received 29 December 201012 January 2010 Accepted 14 January 2010

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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 (α= .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 (ΔE > 1) for group KW and KI fired after 3 times, except for group NM fired after 7 times. 4. In order of decreasing ΔE value fired after 7 times, the values were group KI(ΔE = 2.26) > group KW (ΔE = 1.47) > group NM (ΔE = 1.08) (P < .001).

Conclusion

Repeated firings influenced the color of the zirconium-oxide all-ceramic specimens with different shading methods.

Keywords: Zirconia, Shading, Repeated firings, Color

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Fig. 1.

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

Fig. 2.

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

Fig. 3.

Means of L∗ for different number of firings.

Fig. 4.

Means of a∗ for different number of firings.

Fig. 5.

Means of b∗ for different number of firings.

Table 1.

Zirconia core material used in this study

Group	Coloring method	Zirconia material	Manufacture
KW KI	Masking liner Infiltration with solution	KaVo Everest	KaVo Dental GmbH, Germany
NM	Mixed with metal oxides	Katana Zirconia	Noritake Dental Supply Co. Ltd, Japan

Table 2.

Multivariate test results based on 2-factor repeated measures ANOVA for change in color coordinates after repeated firings

	Group	Mean (SD)	Numerator df	Denominator df	F	P
ΔL∗1-7	KW	-1.37 (0.35)^a	2	147	14.687	< .001
	KI	-1.25 (1.10)^a
	NM	-0.67 (0.30)^b
	KW	-0.15 (0.12)^a
Δa∗1-7	KI	0.02 (0.32)^b	2	147	8.725	< .001
	NM	-0.07 (0.11)^c
	KW	0.19 (0.44)^a
Δb∗1-7	KI	1.68 (1.19)^b	2	147	51.003	< .001
Δb∗1-7	NM	0.63 (0.36)^c	2	147	51.003	< .001

Within same column, means with same lowercase letters do not significantly differ (P > .05).

Table 3.

Mean ΔEab values of all-ceramic specimens after repeated firings

Comparison Number of firings	ΔE
Comparison Number of firings	KW	KI	NM
1, 3	1.21 (0.34)^aA	1.89 (1.50)^aB	0.80 (0.34)^aA
1, 5	1.45 (0.33)^bcA	2.04 (1.47)^abB	0.99 (0.30)^bcA
1, 7	1.47 (0.34)^cA	2.26 (1.42)^cB	1.08 (0.39)^cC
3, 5	0.54 (0.25)^A	0.86 (0.53)^B	0.55 (0.28)^A
3, 7	0.61 (0.26)^A	0.82 (0.52)^B	0.48 (0.24)^A
5, 7	0.55 (0.24)^A	0.92 (0.55)^B	0.49 (0.37)^A

Values followed with same lowercase letters in column do not significantly differ (P > .05). Values followed with same uppercase letters in row do not significantly differ (P > .05).

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