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Abstract:
Processes of polymerization, crystallization and phase changes in viscoelastic materials are accompanied by a change of material parameters. In particular, viscoelastic properties of dental restorations made from Clearfil F2 evolve from viscid, almost liquid substance, to solid material during a short time of photo-polymerization. Below, a new rheological model is used for description of curing of Clearfill F2. The model consists of system of parallel and series connected springs and dashpots, which may adapt to the degree of cure of the material. A method of the system adaptation to the curing process bases on the concept of the „composite rheological models”. In this concept, the elastic moduli and viscous coefficients are given as functions of two groups of new parameters. The first group is called as inner structure coefficients, and the second group as the base material properties. Relations (functions) between the new introduced parameters and elastic moduli and viscosity coefficients are built using information of the model structure. It is assumed that at each time step of the process, the inner structure coefficients are changing, while the base material parameters remain constant. In the proposed model the relaxation curve is available for each moment of the process. It is shown that the numerical simulation of the model response is consistent with the published description of the experimental polymerization of dental material Clearfil F2.