Accuracy of four types of rubber impression materials compared with time of pour and a repeat pour of models.

The accuracy of four types of elastomeric impression materials was studied as a function of model location, time of pouring, and repetition of pouring. There was little change in dimension among abutment preparations for all materials, for all times of pour, and with a repeat pouring. It appears that measurements between posts are not sensitive to detecting differences between materials and that other dimensions should be examined to discern where differences might lie. The diameter of the stone post was larger than the standard for the AS and PS materials and was unchanged or smaller than the standard for the CS and the PE. The vertical dimensions of stone posts were, in general, shorter than the standard for all materials, with the AS demonstrating the smallest change. The AS and CS products demonstrated the best recovery from undercuts and the least change in dimensions between an initial and second pour of an impression. The AS and PE were the least affected with delays of 1, 4, and 24 hours in pouring the impression.