Off-Axial Tear Strengths of Addition Silicone Impression Materials

Objectives: Historically, our group examined several parameters with respect to tear strengths of addition silicone dental impression materials (Boghosian et al, Le et al. 1985 - 2014) comparing commercial products leading to products ranked in tear strengths. In addition, data analyses discovered potential relationships between tear strengths and cross sectional notch thickness or strain rate (Monaghan, et al. 2013-4.) One area which has been neglected is impression material off-axial removal stresses. We designed a protocol to examine such off-axial tear strengths.
Methods: Axial tear specimens of Aquasil Ultra Cordless Single TMIM (Dentsply Caulk, Milford, DE) and Imprint 4 Super Quick Light (3M Oral Care, St. Paul, MN) were made in a mouth-like conditioning environment in a proprietary mould and removed at manufacturers’ dwell times (Boghosian, et al 2009.) Using a custom photographic map, lines were scribed at 0, 10 and 20 degrees on preconditioned specimens. Immediately thereafter, using the scribed lines, specimens were placed tightly in grips mounted in a universal testing machine and run in axial tensile mode at 508 mm/min until failure. Load at failure was recorded and converted to failure stress in MPa. Statistical analysis by 2-way ANOVA (α ≤ 0.0001) was used to determine differences between products with the Tukey-Kramer HSD post hoc analysis used to identify differences between the individual groups. Differences were found between products and between groups at both levels (p = 0.0001.)
Results: The data table below depicts the results.
Conclusions: Strengths of materials increased linearly with increased angle pull. Aquasil Ultra was stronger than Imprint 4 in any head-to-head of equal paring. Acknowledgements: Demeng Che, The Ehmann Group, Northwestern University.