J Adv Prosthodont.  2013 Feb;5(1):44-50. 10.4047/jap.2013.5.1.44.

The effect of repeated porcelain firings on corrosion resistance of different dental alloys

• Tuncdemir
• Karahan I
• Polat S
• Malkoc MA
• Dalkiz M

• KMID: 2284771
• DOI: http://doi.org/10.4047/jap.2013.5.1.44

Abstract

PURPOSE
The aim of this study was to evaluate the effects of repeated porcelain firing process on the corrosion rates of the dental alloys.
MATERIALS AND METHODS
Cr-Co, Cr-Ni and Pd-Ag alloys were used for this study. Each metal supported porcelain consisted of 30 specimens of 10 for 7, 9 and 11 firing each. Disc-shaped specimens 10 mm diameter and 3 mm thickness were formed by melting alloys with a propane-oxygen flame and casted with a centrifuge casting machine and then with the porcelain veneer fired onto the metal alloys. Corrosion tests were performed in quintuplicate for each alloy (after repeated porcelain firing) in Fusayama artificial saliva solution (pH = 5) in a low thermal-expansion borosilicate glass cell. Tamhane and Sheffe test was used to compare corrosion differences in the results after repeated firings and among 7, 9 and 11 firing for each alloy. The probability level for statistical significance was set at alpha=0.05.
RESULTS
The corrosion resistance was higher (30 mV), in case of 7 times firing (Commercial). On the other hand, it was lower in case of 11 times firing (5 mV) (P<.05).
CONCLUSION
Repeated firings decreased corrosion resistance of Pd-Ag, Cr-Co and Cr-Ni alloys. The Pd-Ag alloy exhibited little corrosion in in vitro tests. The Cr-Ni alloy exhibited higher corrosion resistance than Cr-Co alloys in in vitro tests.

Keyword

Alloys; Corrosion test; Repeated firings

MeSH Terms

Alloys
Corrosion
Dental Alloys
Dental Porcelain
Fires
Freezing
Glass
Hand
Saliva, Artificial
Alloys
Dental Alloys
Dental Porcelain
Saliva, Artificial

Figure

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  Fig. 1 Schematic diagram of the corrosion test cycle.

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  Fig. 2 A: Time potential curves of Cr-Co alloys, B: Potentiodynamic polarisation of cast Cr-Co series in the fusayama test solutions, C: Potentiodynamic polarisation of cast Cr-Ni series in the fusayama test solutions, D: Current density-potential curves (Tafel plots) of various firing counts for Pd-Ag series.

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  Fig. 3 SEM images of the Cr-Co dental alloys before and after corrosion test (Original magnification ×1,000). A: before the corrosion test, B: after the corrosion test.

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  Fig. 4 SEM images of the Pd-Ag dental alloys before and after corrosion test (Original magnification ×1,000). A: before the corrosion test, B: after the corrosion test.

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  Fig. 5 SEM images of the Cr-Ni dental alloys before and after corrosion test (Original magnification ×1,000). A: before the corrosion test, B: after the corrosion test.

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