Galvanic Corrosion of Dental Ni-Cr Alloy by Contact with Dental Solders

Part 2. Effect of Cr Concentration of the Alloys

Abstract

In case of soldered crowns and bridges made of Ni-Cr dental casting alloy, contact corrosion possibly occurs in oral environment. Generally, corrosion resistance of Ni-Cr alloy is related to content of chromium, but there are few reports about contact corrosion between Ni-Cr alloy and solder. Thus authers investigated about relation between contact corrosion and content of chromium in Ni-Cr alloys.
In this study, six kinds of Ni-Cr dental casting alloys were selected, these contents of chromium were different. Galvanic cells were constituted with combination of Ni-Cr alloys and gold solder or silver solder in saline solution, and galvanic currents were recorded continuously for a week. Then amounts of Ni and Cu dissolved in saline solution were measured after four months.
Results
1. Ni-Cr dental casting alloys with less than 19% content of chromium became anode either in combination with gold solder or silver solder. And these Ni-Cr alloys were promoted to corrode by contact with solders.
2. Pitting was observed on surfaces of Ni-Cr alloys corroded.
3. Ni-Cr alloys with more than 22% content of chromium did not corrode in this experimental environment.