Corrosion resistance of the Pt-Fe-Nb magnets for dental-casting.

Magnetic attachments have been used in clinical dental practice, but there is some difficulties associated with removable bridges. One possible solution is to make whole bridges of Pt-Fe magnet alloys and its abutment out of magnetic stainless steel by casting. In terms of castability and magnetic properties, the promising composition of the Pt-Fe-Nb magnet alloy is Pt-30.0 mass% Fe-0.6 mass% Nb and Pt-30.0 mass% Fe-0.5 mass% Nb-0.03 mass% Si. In the present study, the corrosion resistance of these alloys was investigated based on the elusion test, electrochemical behavior and surface characterization by EPMA analysis. The released elements from the Pt-Fe-Nb magnets were mainly Fe ions in quantities similar to that of stainless steel for biomedical use, and the Pt-Fe-Nb magnet alloy, the Pt-Fe-Nb-Si magnet alloy and platinum resembled each other in electrochemical behavior. The present findings suggest, that the Pt-Fe-Nb magnet alloy provides excellent corrosion resistance and has important clinical dental applications.