Comparative studies on the mechanic and molecular properties of heat- and self-curing polymers (PMMA) showed the following results: 1. The glass-transition temperature of heat- and self-curing polymers clearly shows measurable differences also as a function of their storage conditions. However, this is hardly of any clinical or practical significance. 2. The modulus of elasticity values of heat and self-curing polymers are not significantly different in the range of the usually applied temperatures. However, water-uptake considerably reduces the rigidity. 3. Overloading or fatigue failures do not show any clear differences in morphological characteristics. The practical influence of smaller long-term inflation strength of self-curing polymers has not yet been sufficiently proven. 4. Heat and self-curing polymers are identical as basic materials for dentures from the point of view of material technology.