Effect of mixing tip design on the mechanical properties, porosity, and waste reduction of extra-light-body polyvinyl siloxane impression material.

The purpose of this study was to compare the tensile strength, modulus of elasticity, porosity, and waste reduction of extra-light-body polyvinyl siloxane (PVS) impression material mixed with a helical impression tip or a new cartridge integrated system (NCIS) from the same manufacturer (Dentsply Sirona). The legacy teal tip (TT group) was compared with the NCIS red (RT group) and blue (BT group) mixing tips. Dumbbell-shaped specimens (TT, n = 17; RT, n = 15; and BT, n = 16) were prepared in accordance with German Institute for Standardization's rubber testing standard (DIN 53504.2017) and tested in a universal testing machine for tensile strength and modulus of elasticity. Porosity was evaluated via microcomputed tomography of cylindrical specimens (TT, n = 7; RT, n = 6; and BT, n = 7). Waste reduction was evaluated by comparing the mass of the mixing tips before use and after polymerization of the PVS to determine the difference in weight, which represented the amount of retained material (n = 11 per group). Tensile strength was analyzed using 1-way analysis of variance (ANOVA). Modulus of elasticity was analyzed using 1-way ANOVA with Tukey HSD. Porosity and waste reduction were analyzed using Shapiro-Wilk, Kruskal-Wallis, and Steel-Dwass tests. The analyses revealed no differences in tensile strength between groups (P = 0.493). The TT group had a significantly higher modulus of elasticity than the RT and BT groups (P < 0.001). The BT group had the highest mean porosity, and the difference between BT and RT was statistically significant (P = 0.048). The RT group showed the least material waste. Supporting the claims of the manufacturer, the NCIS tips generated tensile strengths comparable to that of the legacy tip and produced less waste, achieving waste reductions of 62% (RT) and 21% (BT) compared with the legacy tip. However, the RT and BT groups had a lower modulus of elasticity than the TT group, and porosity was increased in the BT group.