An Evaluation of Dimensional Accuracy of One-Step and Two-Step Impression Technique Using Addition Silicone Impression Material: An In Vitro Study

Abstract

The study is aimed to evaluate the dimensional accuracy, the effect of undercut of two different configurations and the elastic recovery of addition silicone impression material assessed indirectly, by measuring the dimensions on stone models recorded from the impression of the master model, using one-step and two-step impression technique, for addition silicone impression materials. Measurements are taken to evaluate horizontal or linear and vertical dimensional changes, of the abutment V and abutment C from the stainless steel model. Heavy body/light body material is used for making one-step impression technique in a custom tray. Putty/light body is used for taking two-step technique in a stock metal tray. Improved die stone is used for pouring the impression. The different 11 locations on the dies produced by two different techniques are measured microscopically on image analyzer and compared with those of stainless steel model. Anova test was applied to test the differences of mean values of inter and intra abutment measurements, to calculate p value. Unpaired t test was applied to calculate t value. Results showed less deviation of stone models produced by one-step technique from stainless steel model, whereas the deviation of stone models produced by two-step is comparatively more. (p < 0.01). This difference of deviation is significantly less in one-step as compared to two-step technique. One-step is sufficiently dimensionally accurate than two-step technique in conjunction with addition silicone impression material. They have the best elastic recovery from the two undercut configurations.

Dimensional Stability and Accuracy of Silicone – Based Impression Materials Using Different Impression Techniques – A Literature Review

“…The in-vitro study of Pande et al [8] aims at evaluating the dimensional accuracy, the effect of undermining in three different abutments and the elastic restoration of the addition silicone by indirect assessment, measuring the dimensions of the cast plaster models obtained by impressions from the master model, using the double-phase 1-step impression and the double-phase 2-step impression. Moreover, measurements were also made to evaluate the horizontal or linear and vertical dimensional changes of the corresponding abutments of the master steel model.…”

“…The 2-step double phase technique is performed first by filling up the tray with the putty impression material and record the abutment. The second step continues after setting (hardening) of the impression and its extraction from the mouth where low viscosity material is afterwards applied on the first impression and is again returned into the mouth for correctional impression [7][8][9][10].…”

Dimensional accuracy of different impression techniques of partially edentulous mandibular arch

“…Some authors 8,[10][11][12][13][14][15] have demonstrated that the impression technique is a critical factor which directly influences the dimensional accuracy. However, in this study, the dimensional accuracy of a partially edentulous mandibular arch is related more to the type of impression material than the impression technique 7,[16][17] . The 2-step putty/light-body technique was initially developed to decrease the problems of polymerization shrinkage for condensation silicones 18 .…”

“…A ratio of 150 g of type IV dental stone (IV Durone, Dentsply) to 28.5 ml of water was used to fill the molds (n = 5). The sample size was determined according to previous studies 17,[21][22] which demonstrated that 5 samples had an adequate power to detect statistical differences between groups. Three readings were performed for each distance by a single calibrated operator and the means were recorded.…”

“…Several studies showing differences in dimensional accuracy between the impression techniques are found in literature [8][9][10][11][12][13][14][15] . Conversely, other studies show similar outcomes between different impression techniques 7,[16][17] or only small differences within a specific group of elastomeric impression materials 18 . Therefore, there is conflicting evidence on impression techniques.…”