Plasticity of Amalgam Mixes

¹ University of Oregon Dental School, Portland, Oregon

A test was devised to quantitate the plasticity of amalgam mixes prior to condensation. The validity of this test was established, and the effect of various factors on plasticity of various alloys was determined. Although the significance of plasticity on the integrity of the amalgam restoration is yet to be determined, some conclusions were drawn concerning plasticity alone:

1. Increased precondensation-Hg content of amalgam mixes results in increased plasticity.

2. Eames technic mixes provide greater plasticity than conventionally squeezed mixes, although retriturating squeezed mixes for 1 second eliminates this difference.

3. Micro-cut alloy mixes have less plasticity than fine-cut alloy mixes at similar precondensation Hg contents.

4. Spherical particle alloy mixes are extremely plastic but are not unique in this regard, since one conventional fine-cut alloy investigated had a similar plasticity.

5. Plasticity of amalgam mixes decreases with increased time from the end of trituration.

6. Plasticity of amalgam mixes decreases with prolonged trituration.