Modeling of viscoelastic behavior of dental chemically activated resin composites during curing

Shrinkage stresses generated in dental resin composites during curing are a mong the major problems in adhesive dentistry, because they interfere with the integrity of the restored tooth. The aim of this study was to find a me chanical model to describe the viscoelastic behavior of a two-paste resin c omposite during curing, to aid our understanding of the process of shrinkag e stress development. In this study, stress-strain data on Clearfil F2 duri ng curing were obtained by a dynamic test method and analyzed using three m echanical models (Maxwell, Kelvin, and the Standard Linear Solid model), Wi th a modeling procedure, the model's stress response was compared with the experimental stress data, and the material parameters were calculated. On t he basis of the modeling and evaluation results, a model for describing the viscoelastic behavior of the shrinking resin composite was selected. The v alidation results showed that the modeling procedure is free of error, and that it was capable of finding material parameters associated with a two-pa rametric model with a high degree of accuracy. The viscoelastic behavior of the shrinking resin composite, as excited by the conditions of the test me thod, cannot be described by a single mechanical model. In the early stage of curing, the most accurate prediction was achieved by the Maxwell model, while during the remainder of the curing process the Kelvin model can be us ed to describe the viscoelastic behavior of the two-paste resin composite. (C) 2000 John Wiley Bc Sons, Inc. J Biomed Mater Res (Appl Biomater) 58: 16 -26. 2001.