Abstract
The aim of study is to evaluate the linear dimensional changes (cross arch, antero–posterior dimensions) of imp-ressions and die stone casts of two brands of addition silicone impression materials (Express and President) for special master model using two–steps (putty–wash) tech-nique, at different storage times before pouring of impression, by using of three dimensional measuring machine and to compare between the accuracy of the two brands of impression materials.
The results indicated that a significant difference between the interabutment dist-ances of impression and die stone casts. The Express impression materials produce the most accurate results.
There is slightly increase in inter-abutment distances of stone casts. At one hour storage time there are the smallest dimensional changes of impressions and stone casts in relation to construction of complete–arch fixed partial denture.
