Effect of Beverages on viscoelastic properties of resin-based dental composites

Objectives: The viscoelastic properties of three commercially available resin-based composites (Filtek™ P60, Filtek™ Supreme, and Filtek™ Z250; 3M ESPE, UK) were measured using Dynamic Mechanical Analysis (DMA) to determine the effect of beverages on their storage moduli and damping ratios. Methods: Rectangular samples of the three hybrid composites with different matrix structure and filler composition were prepared. They were immersed in three beverages, namely coca-cola, apple juice and mineral water at 37°C for 1, 4, and 8 weeks. At each time interval, these samples were subjected to three-point bend tests in temperature mode using a Perkin Elmer DMA7 dynamic mechanical analyzer to measure the storage modulus and damping ratio. Results: The immersion time had significant influence on the viscoelastic property of composites and it was found that generally for all samples the storage modulus was reduced, whereas damping values increased with immersion time. Conclusion: The composites absorb less energy in repeated stress, and the external energy is likely to be dissipated within the material as residual stress. The acidic environment may cause the scission of polymeric chain and due to dynamic force the movement of molecules was expected to increase leading to movement of polymer chain, which reduces the stress and consequently the storage modulus. The viscoelastic behavior of tested materials seems to be related to the pH environment, hydrophilicity and the chemical composition of composites.