The effect of cold temperature mixing on the properties of zinc phosphate cement

A series of proprietary zinc phosphate cements were evaluated after mixing on glass slabs at three different temperatures, 23 degrees, 6 degrees and -10 degrees C. Working time, setting time, diametral tensile strength, compressive strength and solubility were investigated. From the results of the tests the following conclusions were made: 1) As the temperature of the mixing slab was decreased, the amount of powder required to maintain a constatnt viscosity increased. 2) Compressive, tensile, and solubility values remained constant as the temperature of the mixing slab was decreased provided a consistent viscosity was maintained. 3) Mixing zinc phosphate cement substantially below the dew point is an acceptable practice provided the powder/liquid ratio is modified accordingly. 4) Although the setting time of zinc phosphate cement generally remained constant at temperatures below 6 degrees C, the working time continued to increase at -10 degrees C. 5) Mixing zinc phosphate cemment on a cold mixing slab increases the working time on the glass slab and decreases the setting time in an oral environment. Both of these alterations are clinically beneficial to the orthodontist.