Long‐term dimensional stability of three current elastomers

Abstract

The long-term dimensional stability of three non-aqueous elastomeric impression materials, a silicone, a polyether and a polysiloxane, were investigated. The testing apparatus was an A.D.A. specification No. 19 test block and mould. The impressions were measured by the use of a travelling stage reflecting microscope and a Quantimet 720 Image Analyzing computer at time zero and again at 4, 24 and 48 h, and at 1, 2, 3 and 4 weeks. Impressions poured immediately had the greatest accuracy for all the materials. The polysiloxane (0.025 mm) and polyether (0.033 mm) showed very little change in dimension after 4 weeks when compared to the test block. However, the silicone showed significant change at 4 h (0.14 mm) and 0.2 mm after 4 weeks. After 4 weeks the polysiloxane maintained the best surface detail, the polyether was adequate but the silicone lost much of its detail in as little as 24 h. The reasons for these findings are discussed.

The effect of disinfectants on dimensional stability of addition and condensation silicone impressions

“…In a 1983, Clancy et al 27 examined the dimensional stability of three elastomers as the function of time using specimens from the stainless steel test block and a mold recommended by ADA spec. No.19 (ISO 4823).…”

“…The methods depending on measuring microscope are one dimensional and neglect dimensional changes that exist in all three dimensions 21,26,27 . The studies of Saleh Saber et al 23 and Kronström et al 24 illustrate the reference points and distances for measurements of threedimensional objects which confirm the existence of threedimensional changes, that is in accordance with the results of the present study.…”

Dimensional stability of alginate impression materials measured by a non-pressure direct method.

“…Most of the previous studies [1][2][3][4][5][6][7][8][9][10] which have been carried out on the dimensional changes occurring in impression materials have involved the use of the indirect method, in which complexity of measurement is unavoidable. There have also been some studies [11][12][13] employing measurement by the direct method using transducers and Microkators, although it is feared that when the direct method is used, the in- In the present experiment, the lever-type probe of an electronic micrometer was turned upside down and attached to the top of the stand ; a magnet was attached between the probe and the tip of the specimen, and thus measurement could be made without application of pressure.…”

Dimensional accuracy of implant impression obtained from polysiloxane condensation silicone

“…Since the introduction of hydrocolloids in the mid-1930s, the impression of undercuts became possible. In the 1950s, polysulfides and condensation reaction silicones (C-type silicones) were used reliably in fixed prosthodontics [7].…”