Mechanism of β1formation in conventional dental amalgams

✍ Scribed by N. K. Sarkar

• Book ID: 104643650
• Publisher: Springer
• Year: 1995
• Tongue: English
• Weight: 427 KB
• Volume: 6
• Category: Article
• ISSN: 0957-4530
• DOI: 10.1007/bf00151038

✦ Synopsis

This study reexamined the mechanism of 131 formation in conventional dental amalgams in the light of a previously unrecognized intergranular structure, the SnHg-82 phase. Two amalgams, A (45.5% Hg) and B (65.0% Hg), were made from a Zn-free alloy of the following composition (wt%): Ag-70, Sn-26, Cu-4. After storage at 37 °C for 1 day, both amalgams were heat treated at 70°C for up to 16 days. The structural changes in the two amalgams as a function of their heat treatment were characterized by differential scanning calorimetry and X-ray diffraction techniques. On the basis of the experimental data, we have proposed a new mechanism on 131 formation. This mechanism involves a series of interrelated reactions. The primary one is a reaction between AgSn-7 and 62 that leads to the nucleation of 131 at 7 boundaries. Simultaneous operation of several secondary and tertiary reactions result in (1) further growth of 131 and its continuing change in composition, (2) loss of Sn from the 71 matrix, (3) conversion of CuHg into rl', and (4) a possible transformation of 72 into Sn-rich 132 or ~2.