Physical and Mechanical Properties of Elastomeric Impression Materials

Purpose: The project evaluated properties of five elastomeric impression materials. Methods: The elastomeric impression materials tested were: addition silicone (Aquasil Ultra Xtra Medium, AUXM), polyether (Impregum Penta Medium, IPM; Impregum Soft, IS) and silicone-polyether elastomeric (EXA'lence Monophase, EM; Identium Medium-Soft, IMS) regular-setting impression materials. The Shark Fin test (3M ESPE) was measured at 24°C at 25 seconds after start of mixing and at the end of the working time. Elastic recovery and strain in compression were determined by ISO 4823. Pants tear energy was determined by methodology of Webber and Ryge. Toughness was determined by ISO 53504. Specimens were tested on an Instron 5866 at crosshead speed of 20 mm/min at 5 minutes after the start of mixing. Data were analyzed by ANOVA and Fisher's PLSD test at 0.05 level of significance. Results: Means (n=5) and standard deviations are listed in Table 1.

Table 1. Properties of impression materials.

Property                                      IPM                            IS                                AUXM                       EM                              IMS

Shark Fin

at 25 sec, mm           11.4(0.1)*                14.3(0.1)^a                                   12.6(0.4)^b                                   12.6(0.4)^b                                   14.0(0.4)^a

Shark Fin

at WT, mm                  9.9(0.1)                     7.9(0.4)                     2.1(0.1)^a                                      2.1(0.1)^a                                      6.0(0.4)

Strain in

Compression, %       2.7(0.1)                     2.4(0.1)^a                                      2.9(0.1)                     2.3(0.1)^a                                      3.3(0.1)

Elastic

Recovery, %             98.2(0.1)                                     99.0(0.1)                                     99.5(0.1)                                     97.5(0.1)                                     99.3(0.1)

Tear Energy,

J/m²                            1240(80)^a                                   1720(100)                1200(40)^a                                   820(50)^b                   730(90)^b

Toughness,

Nmm/mm³                  4.6(0.5)^a                                      5.0(0.5)^a                                      2.8(0.4)^b                                      2.6(0.2)^b                                      1.9(0.6)

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*Means (n=5) with standard deviations in parentheses. Means with the same superscripted letters are not different statistically (p=0.05).

Conclusions: Shark Fin height measured between 25 seconds and the end of the working time decreased 13% for IPM, 45% for IS and 57% for IMS, and 83% for AUXM and EM. Strain in compression ranged from 2.3% to 3.3%. Elastic recovery ranged from 97.5% to 99.5%. Tear energy ranged from 730 to 1720 J/m². Toughness ranged from 1.9 to 5.0 Nmm/mm³. Acknowledgment: Supported in part by 3M ESPE.