Kinetic analysis of the nonisothermal degradation process of Zetaplus impression material has been performed. Kinetic data for the investigated degradation process were obtained from the thermogravimetric (TG) and differential thermal analysis (DTA) measurements conducted at the three different heating rates (beta = 10, 20, and 25 degrees C min(-1)) in an air atmosphere. For determination of the kinetic model function (f(alpha) or g(alpha)), the isoconversional and Master-plot methods were used. It was found that the first degradation stage of Zetaplus impression material can be described by the three-dimensional diffusion (D3) and with the following values of kinetic parameters: E-a = 99.5 kJ mol(-1) and A = 1.05 x 10(8) min(-1). Kinetic analysis shows that the first degradation stage corresponds to the bond cleavages and polydimethylsiloxane thermal volatilization, which is contolled by the rate of diffusion and evaporation of oligomers produced on decomposition. The observed second degradation step is more complex; it includes two parallel independent reactions with different values of the apparent activation energy. By applying the nonlinear regression (NLR) method, it was found that the second degradation stage can be described by two independent parallel first-order reactions (nth-order reaction model).