Setting Reactions of Spherical-Particle Amalgams

¹ Department of Dental Materials, Marquette University School of Dentistry, Milwaukee, Wisconsin

The setting reaction of amalgam has been studied by metallographic examination and X-ray-diffraction studies and microindentation hardness used as an auxiliary aid.The amalgams studied were prepared from spherical-alloy particles of the composition Ag₃Sn.

It has been determined that spherical particles retain their original shape, and the amount of material reacting (as measured by reduction in size of the original particle) is small.

Original alloy is present in fully set amalgams, even when excess mercury is present.

Two phases have been detected in the set amalgam by microscopic examination. The harder, stronger, more vigorous silver-mercury phase tends to influence the disposition of the softer, weaker, slower-forming tinmercury phase.

The relationship between reactions taking place on the surface and in the body of setting amalgam has been established.

Spherical-particle amalgams provide an excellent system for the study of setting reactions in amalgam.