Effect of Contact Time Between Silicone Impression Materials and Stone on Dimensional Stability of Resultant Cast

Abstract

Background:Numerous factors have an effect on the accuracy of an impression and resultant cast, and these include: impression material, impression technique, tray selection, impression disinfection, storage time of impression before pouring, stone type used for fabrication of cast. Up to now, there has been little research conducted on the effect of contact time of a cast with an impression, on the dimensional stability of a cast. Objectives: The purpose of this study was to evaluate the effect of the contact time of silicone impression materials with stone casts, on the dimensional stability of resultant casts. Materials and Methods: A total of 44 impressions were made from a stainless steel master model, with each one of two silicone impression materials (Elite HD+ and Speedex), and poured with Elite Master Type IV. The thickness of the light-body material (1 mm) was provided by using four copings. The resulting casts from each material were placed in four groups (n = 11) after each contact time with the impression (1 hour, 24 hours, 48 hours, 1 week). Distance between anterior and posterior abutments was measured for the casts and master model. Data were analyzed by two-way analysis of variance and a Tukey test. Results:The relationship between the dimensional stability of the casts and the simultaneous effect of the impression material and contact time of the cast with the impression was not statistically significant (P = 0.099). Type of impression material on the dimensional stability of the cast had no significant effect (P = 0.163). Increased contact time of the cast with the impression resulted in increased dimensional change (P < 0.001). Conclusions: Dimensional stability of the casts after different contact time with the impression was acceptable. The best time to separate the cast from the impression was one hour after pouring the impression.

An In-Vitro Evaluation of the influence of repeat pours of addition silicone impressions on the dimensional accuracy of resultant casts: an original research study

“…[2] The master model employed in our study was comparable to the standard die used to assess dimensional stability by Heidari and associates. [9] Similar model was used for making the impression in the research made of stainless steel was used by Heidari and associate9 and Aalaei and colleagues10 and in addition, it was similar to the pattern used in a study by Schleier and co-workers. [11] This kind of model has more dimensional stability compared to plaster or wax models.…”