Influence of porcelain re-firing on the formation of surface bubble and on the change in shade of metal-ceramic crown exposed to artificial saliva

Ji-Hyun Park; In-Sung Yeo; Sung-Hun Kim; Jung-Suk Han; Jai-Bong Lee; Jae-Ho Yang

doi:10.4047/jkap.2011.49.2.161

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Park, Yeo, Kim, Han, Lee, and Yang: Influence of porcelain re-firing on the formation of surface bubble and on the change in shade of metal-ceramic crown exposed to artificial saliva

ORIGINAL ARTICLE

J Korean Acad Prosthodont 2011;49(2):161-167.

Published online: 18 December 2011

DOI: https://doi.org/10.4047/jkap.2011.49.2.161

Influence of porcelain re-firing on the formation of surface bubble and on the change in shade of metal-ceramic crown exposed to artificial saliva

Ji-Hyun Park, MSD, DDS, In-Sung Yeo, MSD, DDS, PhD, Sung-Hun Kim, DDS, PhD, Jung-Suk Han, MSD, DDS, PhD, Jai-Bong Lee, MSD, DDS, PhD, Jae-Ho Yang, MSD, DDS, PhD^∗

Department of Prosthodontics, School of Dentistry, Seoul National University, Seoul, Korea

∗Corresponding Author: Jae-Ho Yang Department of Prosthodontics, School of Dentistry, Seoul National University, 62 Changgeonggungno, Jongno-Gu, Seoul, 110-749, Korea +82 2 2072 2661: e-mail, jhoyang@snu.ac.kr

Received 13 October 201029 November 2010 Accepted 14 February 2011

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 purpose of this study was to evaluate the influence of porcelain re-firing on the formation of surface bubble and on the change in shade of metal-ceramic crown exposed to artificial saliva.

Materials and methods

Thirty disk-shaped specimens were made in 10 mm diameter with 0.5 mm metal core thickness and 1 mm ceramic thickness. A spectroradiometer was used to determine the CIE Lab coordinates. The number and size of surface bubble were observed with a stereomicroscope. After the exposure to artificial saliva for 7 days, re-firing was performed at glazing temperature. After re-firing, the CIE Lab were calculated, and the number and size of surface bubble were observed again. The change in shade was expressed with △E . Statistical analysis was done with paired t-test for the change in the number of surface bubble and student t-test for the change in the size of surface bubble (α= 0.05).

Results

Shade difference was calculated 2.14 △E units. The mean number of surface bubble was 1.33 ± 1.49 before re-firing, 3.27 ± 2.90 after re-firing. After re-firing, the number of surface bubble was significantly increased (P<.05). The mean size of surface bubble was 81.97 ± 32.03 ㎛ before re-firing, 142.94 ± 47.40 ㎛ after re-firing. After re-firing, the size of surface bubble was significantly increased (P<.05).

Conclusion

Shade change after re-firing was perceptible (△E < 2.0) and clinically acceptable (△E < 3.7). The number and size of surface bubble was significantly increased after re-firing. Further investigation to decrease the surface bubble on the extra oral repair of metal-ceramic crown, will be needed in future study. (J Korean Acad Prosthodont 2011;49:161-7)

Keywords: Metal ceramic crown, Re-firing, Shade, Surface bubble

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Fig. 1.

Generated large bubble.

Fig. 2.

Effect of immersion in acetone. A: Removal of organic materials, B: Combustion of organic materials.

Fig. 3.

Procedure of specimen fabrication. A: Metal coping, B: Mold for porcelain build up, C: fabricated specimens.

Fig. 4.

Increase of air bubbles on porcelain surface after re-firing was detected in the stereomicroscope images. (arrows) (Original magnification, ×20). A: Before re-firing, B: After re-firing.

Table 1.

Firing procedures

	Starting temperature	Dried temperature time	Temperature rise per minute	Firing temperature	Firing temperature time	Vacuum starting temperature	Vacuum finishing temperature
First opaque firing and second opaque firing	600℃	8 min	55℃	945℃	30 sec	700℃	945℃
Dentin firing	600℃	5 min	55℃	930℃	1 min	700℃	930℃
Enamel firing	600℃	5 min	55℃	915℃	1 min	700℃	915℃
Glaze firing	600℃	3 min	55℃	905℃	1 min	700℃	905℃

Table 2.

Change in shade after re-firing

	Mean	SD
L₁ - L₂	2.036	0.963
a₁ - a₂	0.260	0.089
b₁ - b₂	-0.209	0.19
△E	2.140	0.822

Table 3.

Change in number of air bubbles after re-firing

	Number of specimens	Number of air bubbles	Mean	SD
Before re-firing	30	40	1.33	1.49
After re-firing	30	98	3.27	2.90

Table 4.

Change in size of air bubbles after re-firing (unit: ㎛)

	Mean	SD
Before re-firing	81.97	32.03
After re-firing	142.94	47.40

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