Accuracy and Dimensional Stability of two Polysiloxane Putty- wash Impression Techniques

Statement of problem: 

The accuracy and dimensional stability of dental impression materials and technique is an important factor in the accuracy and fitness of the final restoration. Condensation- reaction polysilicone impression material has adequate accuracy and is the most commonly used material in fixed prosthodontic restorations with putty- wash technique. There are different considerations and controversies in the literature about the effect of impression technique on the accuracy of restoration.

The aim of this study was to compare the accuracy and dimensional stability of two polysiloxane putty- wash impression techniques with and without spacer.

A laboratory model with two metallic dies was used. In one of the dies a horizontal notch was applied as an undercut. Ten impressions were made without spacer and another ten with spacer. Twenty stone models were made from both techniques. Dimensions of the stone models were measured and comparison was made with the laboratory model dimensions. The results were analyzed using T- test.

The results showed that the height of the dies without undercut was decreased in both groups, being significant in non- spacer technique ( p <0.001). The distance between the two dies increased in both techniques. The difference was significant in technique without spacer ( p <0.002). The height of the dies above the undercut increased and in both techniques they proved to be statistically significant (without spacer p<0.003 and with spacer p<0.001).

The polysiloxane putty- wash impression technique with spacer is more accurate for fabricating the stone die.