Objective . The elastic modulus (EM) is the main constant characterizing the stiffness of a solid material. Different methods are known to describe this parameter, as there are mechanical (static vs. dynamic) or acoustic methods. The aim here was to evaluate the influence of different measuring principles on the elastic moduli of different dental direct restoratives.
Materials and methods . Three different resin based materials of various filler concentration and one resin modified glass ionomer cement (RMGIC) were selected for measuring the elastic modulus in three different testing regimes: static mechanical analysis (SMA, specimen deflection in 3p-bending with an extensometer), dynamic mechanical analysis (DMA, cyclic testing in 3p-bending as a function of temperature) and acoustic wave propagation analysis (US, velocity measurement of ultrasound). Specimens (2 × 2 × 25 mm (SMA, DMA) or 3 × 3 × 25 mm (US)) were produced ( n = 5) and stored dry (except for RMGIC) for 7d @ 37 °C prior to measurements. Statistical analysis was performed with 2-way ANOVA, mod. LSD ( p < 0.05).
Results . The different materials and different testing regimes as well as the combination of both have a significant influence ( p = 0.000) on the elastic modulus. Comparing the subsets, the statistical homogenous results are indicated in Table 1 .