The effects of manipulative variables on base forming materials for amalgam restorations

The influence of several manipulative variables on the compressive and tensile strengths of eight base forming materials has been investigated. The most important manipulative variable from the point of view of influencing the development of strength was found to be the powder-liquid ratio. In particular, thicker mixes produced greater early strengths. The setting time of each material was found to be influenced more by the temperature during setting than the ambient temperature or presence of moisture.