IADR Abstract Archives
Influence of Elastomer Thickness on Tear Strength
Influence of cross section area on elastomer tear strength is not well defined for dental impression materials. Objective: This work was conducted to find any relation between cross section areas and tear strengths of dental impression elastomers. Method: Three addition silicone impression materials (Exafast NDS Injection [GC], GC Corp, Affinity Light Body HF [CC], Clinicians Choice, Imprint 3 Quick Step LB[3M], 3M ESPE) with known standard testing performance values were selected. A current standard testing protocol (Lautenschlager, Greener, Boghosian, Monaghan, developed 1989, last presented 2012, Seattle) was modified to produce specimen notches of cross section thicknesses of 30, 60, 120, 240 and 480 µm. Centered notch specimens (100 mm x 19 mm x 3 mm) were made at 35°C in a proprietary stainless steel mould and removed at manufacturers' published setting times. Upon demoulding, the specimens were quickly installed in a universal testing machine (MTS) and immediately loaded in tensile mode at 250 mm/min until failure. Tear stress data were calculated and statistically analyzed using one-way ANOVA and the Tukey-Kramer HSD tests (p ≤ 0.001) for each thickness group. A regression analysis was also performed. Results: Data are given in the following table and fit (R2 = 0.9939) an equation of the type: σ' = A'σ(-0.5) where A' is a material specific factor and σ' is the predicted tear stress. Conclusions: Tear strengths were highest with the thinnest specimens and lowest with the thickest. A generalized equation to calculate tear strength is proposed. The materials tested herein had tear strength values and hierarchical ranks similar to previous studies. Acknowledgement: Piedong Han, The Ehmann Group, Northwestern University.
| Elastomer Impression Materials Tear Strengths According to Notch Thicknesses | ||||
Product | 30 µm | 60 µm | 120 µm | 240 µm | 480 µm |
GC | 10.3 MPa ± 0.9 | 6.1 MPa ± 0.6 | 4.3 MPa ± 0.2 | 3.2 MPa ± 0.2 | 2.2 MPa ± 0.1 |
CC | 11.5 MPa ± 0.8 | 7.4 MPa ± 0.3 | 5.1 MPa ± 0.1 | 3.6 MPa ± 0.1 | 2.7 MPa ± 0.1 |
3M | 15.3 MPa ± 1.2 | 9.6 MPa ± 0.6 | 6.9 MPa ± 0.4 | 4.9 MPa ± 0.3 | 3.7 MPa ± 0.2 |