To evaluate the effect of storage temperature on the linear dimensional accuracy of delayed and repeat pours of two addition silicone impression materials

Abstract

Background: Addition silicone elastomers are the most commonly used impression materials for making final impression for fixed partial dentures, implants, and removable partial dentures. The dimensional stability and accuracy of addition silicone impression material is influenced by the storage time, temperature, and repeat pour. Aim and Objectives: The aims and objectives of this study were to evaluate the accuracy of two different types of addition silicone elastomeric impression materials, stored at different temperatures; to evaluate the accuracy of two different types of addition silicone elastomeric impression materials after delayed and repeated pour; and to compare the linear dimensions of two different types of addition silicone elastomeric impression materials with a control die. Materials and Methods: A machined standard steel master die and a metal custom impression tray were made for making a final impression of machined standard steel master die. The final impression was made by using two different brands of addition silicone impression materials (Aquasil™ Ultra Impression material, Dentsply/Caulk, Milford, DE, USA, and 3M™ ESPE™). Double-step putty light-body impression technique was used for making the final impression. In this manner, a total of eighty impressions were made, and they were divided into two groups namely Group I and Group II. To study the effect of delayed pours and storage temperature, the two groups were further divided into four subgroups, with ten impressions each. All the ten impressions of each subgroup were stored in an acrylizer at 40°C, −10°C for 24 h, −2°C for 48 h, and 0°C for 1 week inside a refrigerator in sealed plastic bags before being poured with type IV dental stone. To study the effect of repeat pours on the accuracy of stone casts, all the ten impressions of each subgroup were immediately re-poured with type IV die stone after the removal of the first set of casts. Thus, again a fresh set of eighty casts were obtained having forty casts to each group. Results: When the impressions were stored in the acrylizer at 40°C, −10°C for 24 h, −2°C for 48 h, and 0°C for 1 week, the addition silicone impression materials did not show any significant change when compared to the control samples. Conclusion: Both the types of addition silicone elastomeric impression materials maintained their accuracy after delayed pours and repeat pours. Storing impressions under different conditions caused no adverse effect upon the accuracy of both types of addition silicone elastomeric impression materials. There was no significant change in the dimensions of stone casts obtained from both impression materials as compared to the dimensions of the master die. Even though if the addition silicone impression material is delayed, i.e. poured up to 1 week, repeat poured, and exposed from − 10°C to 40°C, the linear dimensional accuracy will not be adversely affected.