ACCURACY OF DIES OBTAINED FROM DUAL ARCH IMPRESSIONs using different impression materials AND TECHNIQUES

Abstract

Summary & conclusion

T his in vitro study investigated the dimensional accuracy of impression trays (dual arch method and conventional full arch custom) using two elastomeric impression materials: 1) Polyvinylsiloxane impression material 2) Polyether impression material, following three impression techniques: 1) monophase technique 2) double mix double steps technique without releif 3) double mix single step technique. In the present investigation,a typodont cast was used to simulate the clinical condition containing a stainless steel die in the place of missing lower right second premolar and a fixed force of closure was used to standardize the load during closure of the articulated typodont casts. The stainless steel die was scored occlusally with two vertical lines intersected by a horizontal line making 2 points of intersection to measure the distance between them. Each line was 500um in width and 500 um in depthusing a milling machine. Summary and Conclusion

The mean value of the distance transferred to the testing samples was measured at time intervals of 1 hour and 24 hours for each sample and the results were compared with the metal die.

Data were collected from all the tests previously done according to the sample grouping in the form of tables of mean and standard deviations. The collected data were statistically analyzed.

The significant level was set at p<0.05. Kolmogorov-smirnova and Shapiro-Wilk tests were used to assess data normality distributed. Mixed Anova was used to assess effect of impression materials, impression techniques and impression methods over accuracy of bite registration.

Summary and Conclusion

The results of this in vitro study showed that there is no statistically significant effect of the elastomeric impression materials on the dimensional accuracy.

The impression technique showed a statistically significant effect over percentage ofdimensional changes where the monophase technique gave the best results while the double mix double step gave the highest distortion.

As regarding to the impression tray types, although in this study dual arch method gave higher accuracy Than PVS while the polyether showed higher accuracy with the conventional custom trays, the results showed no significant effect on dimensional accuracy.

Conclusions Within the limitation of this study, the following conclusions were drawn

Summary and Conclusion

• Polyvinvlsiloxane and polyether impression materials provided accurate records. • Both dual arch trays and conventional arch trays can provide accurate impressions. However, using dual arch tray with PVS gave higher accuracy. • Polyether gave high success rate with full arch tray while PVS gave high success rate with dual arch tray. • The dimensional accuracy is influenced mainly by the impression techniques. The monophase technique gave the highest accuracy.