Accuracy of Various Elastomeric Impression Materials

Objectives:The purpose of this study was to evaluate the accuracy of reproducibility of various impression materials. Methods: The impression materials used in this experiment included five commercial silicone impression materials (Exaflex regular type, Aquasil , Express, Coltex fine and Rapid liner) , three alginate impression materials (Algiace Z, Cavex, Jeltrate), and two experimental silicone impression materials (KE106A and KE106B). Impression was made of 10 stainless steel master dies similar to prepared crowns. Impressions were poured at 30 min later with dental stone. After 1 more hour, the impressions and the stone dies were separated, then were re-poured and separated after another 1 more hour. The third round stone dies were made again after staying in room temperaturer for 24 hours. There were two kinds of stone used in this experiment (MG Crystal rock and Super hard stone). The diameter of occlusal surfaces of metal and stone dies were determined by taking the photos of occlusal surface with Canon DC 290 digital camera first, and then were measured by photomicrograph digitize integrate system to compare their discrepancy. All the data were analyzed by 3-way ANOVA to compare the influence of 10 impression materials, 3 storage times and 2 stones. Results: The results showed that only the impression material groups had statistic significance. According to the measurement data, we found that: (1) Aquasil was the most accurate (0.70%), KE106A was the worst(1.81%).(2) The storage time did not affect the discrepancy statistically (3) Two stones had no different accuracy under the same water powder ratio condition. (4) The more filler was contained, the less discrepancy. Conclusions:From this study it can be concluded that Aquasil was the best choice for impression taking, and two-ep putty-wash impression technique was the more adequate method than others.