Open Access, Peer-reviewed, Quarterly
pISSN 0301-2875
eISSN 2005-3789
    J Korean Acad Prosthodont. 2011 Apr;49(2):161-167. Korean.
    Published online Apr 30, 2011.
    https://doi.org/10.4047/jkap.2011.49.2.161
    Copyright © 2011 The Korean Academy of Prosthodontics
    Original Article

    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, DDS, MSD, In-Sung Yeo, DDS, MSD, PhD, Sung-Hun Kim, DDS, PhD, Jung-Suk Han, DDS, MSD, PhD, Jai-Bong Lee, DDS, MSD, PhD and Jae-Ho Yang, DDS, MSD, 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: Email: jhoyang@snu.ac.kr
    Received October 13, 2010; Revised November 29, 2010; Accepted February 14, 2011.

    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 ΔE. 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 ΔE 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 µm before re-firing, 142.94 ± 47.40 µm after re-firing. After re-firing, the size of surface bubble was significantly increased (P<.05).

    Conclusion

    Shade change after re-firing was perceptible (ΔE < 2.0) and clinically acceptable (ΔE < 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.

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

    Figures

    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.

    Tables

    Table 1
    Firing procedures

    Table 2
    Change in shade after re-firing

    Table 3
    Change in number of air bubbles after re-firing

    Table 4
    Change in size of air bubbles after re-firing (unit: µm)

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    MeSH Terms
    Ceramics
    Crowns
    Dental Porcelain
    Humans
    Pyridines
    Saliva, Artificial
    Thiazoles
    Metrics
    Share
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    Tables
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