Effect of two impression techniques on some properties of silicone impression materials

ABSTRACT

Putty-wash impression technique is commonly used with addition and condensation silicone impression materials. It can be made either as a one-step or a two-step procedure. The aim of the present study was to compare between the two techniques regarding their effect on some properties of silicone impression materials. To evaluate their effect on dimensional accuracy and undercut reproduction impressions were made for a master model using the two techniques and stone casts were poured. The dimensions of the stone casts were compared to those of the master cast. Split moulds attached to the universal testing machine were used to evaluate the putty wash bond strength. The results revealed that the one-step technique was significantly more accurate with condensation silicones while the accuracy of addition silicones was not significantly affected by the impression technique. Both techniques provided the same accuracy of undercut reproduction. Addition silicones exhibited greater putty-wash bond strength than condensation silicones. The one-step technique yielded higher bond strength with addition silicones while the two-step technique provided greater bond strength with condensation materials. Contamination of the putty surface with saliva markedly reduced the bond strength while contamination with residual monomer resulted in a stronger adhesive junction