Tear Strength of Elastomeric Impression Materials: An In-vitro Comparison

Methods: A new hybrid impression material, a polyether and four polyvinylsiloxanes were tested: Aquasil^TM Dentsply (AD), Hydrorise® Zhermack (HZ), Affinis® Coltene (AC), Flexitime® Heraeus Kulzer (FH), Impregum^TM 3M Espe (IM) and Exa’lence^TM GC (EG). For each material 3 different viscosities were evaluated: heavy body (HB), medium body (MB), light body (LB). A total of 170 samples was divided in 17 groups, each one composed by 10 dumbbell shaped specimen, considering different viscosity and manufacturer. Samples were manufactured through an aluminum mold according to specifications DIM, ISO 37 and ASTM D412. Specimens were allowed to set for complete polymerization. Tensile strength tests were performed after 1 hour using a Universal Instron machine at crosshead speed of 250mm/min until failure. Data were processed and analyzed with one way ANOVA (P ≤ 0.05).

Results: TS: HB: AD 5.1(a), AC 4.93(a), FH 4.91(a), HZ 3.19(b), IM 1.49(c), EG 1.42(c); MB: AD 4.18(a), EG 3.16(b), AC 2.6(bc), FH 2.11(cd), HZ 1.8(d), LB: AD 4.98(a), EG 4.03(b), FH 3.02(c), HZ 2.3(d), AC 2.03(de), IM 1.47(e). YS: HB: AC 2.85(a), AD 2.35(ab), FH 2.11(abc), HZ 1.59(b), IM 1.11(c), EG 0.95(c); MB: AD 2.7(a), AC 1.77(ab), FH 1.46(b), HZ 1.37(b), EG 1.34(b), LB: EG 2.69(a) AD 1.97(ab), FH 1.78(abc), HZ 1.35(bc), AC 1.12(bc), IM 0.93(c). All values are expressed in MPa. At the same letter do not correspond statistically significant different results.

Conclusions: With regard to the mechanical properties (TS and YS) tested, considering all different viscosities, PVS and hybrid materials showed higher in-vitro results than polyether material. Heavy-Light or Heavy-Medium combinations returned comparable mechanical performances. Regardless the materials, a permanent deformation occurred from 53% to 77% of their tensile strength.