The Effect of Mechanical Amalgamation on the Strength of Amalgam

¹ West Virginia University, School of Dentistry, Morgantown, West Virginia

The effect of mechanical amalgamation on the compressive strength of 4 amalgam alloys was investigated. The amount of trituration was systematically increased and decreased, and controlled method of hand condensation was used to prepare the samples. The 1-hour, 1- and 7-day strengths were determined. The relationship between frictional heat developed in the alloy during trituration and the 1-hour strength was studied. The following conclusions were obtained: (1) increased mechanical amalgamation will cause a significant increase in the 1-hour strength to a maximum and then a decrease. This increase may be related to the frictional heat developed in the alloy during trituration. The amount and rate of increase in 1-hour strength will vary with the alloy used; (2) increased mechanical amalgamation causes no significant increase in the 24-hour and 7-day strengths, which display relatively constant strengths that gradually decrease; (3) the relative particle thickness does not seem to be a major factor in controlling the strength of the alloys tested; (4) trituration must be thorough for adequate strength, and decreased trituration should be avoided to prevent loss in strength.