The influence of temperature on the dimensional stability of poly (vinyl siloxane) impression materials.

It may be desirable to extend the working time of poly(vinyl siloxane) impression materials when making a multiple-unit impression. Alteration of the base-catalyst ratio is not possible with automix systems, but chilling the impression material provides an alternative. This study evaluated the dimensional accuracy of chilled impression material and the effect on accuracy of reheating the impression to mouth temperature prior to pouring. Two brands of poly(vinyl siloxane) impression material were evaluated both after refrigeration and at room temperature. Impressions were poured at room temperature and reheated to mouth temperature prior to pouring. Gypsum dies were recovered and measured. Refrigeration had no statistically significant effect on dimensional accuracy. Reheating the impression had no clinically significant effect on accuracy.