Korean J Dent Mater.  2023 Sep;50(3):135-144. 10.14815/kjdm.2023.50.3.135.

Effect of cooling rate during simulated porcelain firing and post-firing heat treatment on the hardness of Pd–Ag–In-Sn metal-ceramic alloy

• Kim MJ
• Shin HJ
• Jeong JI
• Seol HJ

• KMID: 2546957
• DOI: http://doi.org/10.14815/kjdm.2023.50.3.135

Abstract

The objective of this study was to investigate the effect of different cooling rates and subsequent post-firing heat treatment on the final hardness of a metal-ceramic alloy. For this, Specimens of Pd-Ag-In-Sn alloy underwent simulated firing at two different cooling rates, followed by post-firing heat treatment. Hardness measurement, microstructure observation, and crystal structure analysis were conducted on the firing simulated and post-firing heat-treated specimens to analyze the causes of hardness variations. The experimental results showed that the difference in cooling rates during simulated firing had an impact on the final hardness of the alloy, and the specimens cooled at the slowest rate (Stage 3) exhibited higher hardness at all firing Stages compared to the specimens cooled at the highest rate (Stage 0). Regardless of the difference in cooling rates during the firing process, the hardness of the alloy significantly increased by the post-firing heat treatment. The increase in hardness by the post-firing heat treatment was attributed to the formation of fine precipitates in the matrix, and the precipitation reaction occurred as a result of the decrease in solubility of (Pd, Ag, Au) 3 (In, Sn, Zn) phase in the Pd-Ag-rich matrix. The clinical significance of this study is that performing the post-firing heat treatment demonstrates effectiveness in increasing the reduced hardness after porcelain firing in metal-ceramic alloys.

Keyword

Porcelain-firing simulation; Post-firing heat treatment; Precipitation; Pd-Ag-In-Sn alloy; Cooling rate