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

• Park JH
• Yeo IS
• Kim SH
• Han JS
• Lee JB
• Yang JH

• KMID: 2196123
• DOI: http://doi.org/10.4047/jkap.2011.49.2.161

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 DeltaE. 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 (alpha= 0.05).
RESULTS
Shade difference was calculated 2.14 DeltaE 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 microm before re-firing, 142.94 +/- 47.40 microm after re-firing. After re-firing, the size of surface bubble was significantly increased (P<.05).
CONCLUSION
Shade change after re-firing was perceptible (DeltaE < 2.0) and clinically acceptable (DeltaE < 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.

Keyword

Metal ceramic crown; Re-firing; Shade; Surface bubble

MeSH Terms

Ceramics
Crowns
Dental Porcelain
Humans
Pyridines
Saliva, Artificial
Thiazoles
Ceramics
Dental Porcelain
Pyridines
Saliva, Artificial
Thiazoles

Figure

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  Fig. 1. Generated large bubble.

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  Fig. 2. Effect of immersion in acetone. A: Removal of organic materials, B: Combustion of organic materials.

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  Fig. 3. Procedure of specimen fabrication. A: Metal coping, B: Mold for porcelain build up, C: fabricated specimens.

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  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.

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