It is apparent that at high filler contents the strain locally may become quite large, i.e. 3Â§2.4), raising the energy of the system. Flexible impression materials play a crucial role in the fabrication of many dental devices, from full dentures to inlays, from orthodontic appliances to implanted prostheses. dropping non-negligible higher powers of strain is not appropriate in these circumstances. A previous research revealed that there are significant differences between testing immediately after the setting time and 24 hours following the setting time . Again, it is a matter of the design of the test reflecting the actual service conditions. Taking the length between filler particle centres as the reference unit, the column with the filler particle is shorter by the filler particle diameter. If any portion of the system is not constrained by cross-links, entanglements or bonding to filler, true flow must occur to give permanent deformation as well (Â§2.4). The amount of permanent deformation is related to the concentration of elastically effective network strands and the degree of cross-linking [14, 21]. It may also be noted that these considerations apply to any polymer system, not just elastomers, and to filled resins in particular (6Â§2.8). Since many of the restorative devices that are used in dental treatment need to be fabricated outside of the mouth, ranging from inlays to full dentures, there are obvious problems in getting them to fit if reliance is placed on trial and error methods. 3.1). Fillers are again often important in order to obtain adequate viscosity in the unset material, and appropriate stiffness when it is set. Flexitime showed the highest Sy values among the LB products (56.57 mm) and the lowest values among the HB materials (9.43 mm). PE impression materials showed the lowest yield strength, regardless of the viscosity. The same superscript letters indicate no statistically significant differences (, C. 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Mcguire, “Correlation of impression removal force with elastomeric impression material rigidity and hardness,”, W. D. Cook, F. Liem, P. Russo, M. Scheiner, G. Simkiss, and P. Woodruff, “Tear and rupture of elastomeric dental impression materials,”, W. D. Sneed, R. Miller, and J. Olson, “Tear strength of ten elastomeric impression materials,”, L. Brauchli, M. Zeller, and A. Wichelhaus, “Shear bond strengths of seven self-etching primers after thermo-cycling,”, N. C. Lawson, J. O. Burgess, and M. Litaker, “Tear strength of five elastomeric impression materials at two setting times and two tearing rates,”. ’ ability to bend before it breaks the PE-based Impregum presented the highest YS with the LB viscosity prosthetic relies. The success rate of stress relaxation the polyether was also recognized [ 15, 17.... Based on polysulphide, polyether and silicone rubbers the authors recommend that serious consideration be given to the to... 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