The swelling phenomenon of acrylic resin polymer teeth at the interface with denture base polymers

Purpose. This study examined the interface between acrylic resin polymer teeth and denture base polymers. Material and methods. An autopolymerized denture base polymer was cured either at 30 degrees C, 50 degrees C, or 70 degrees C, and a heat-cured denture base polymer was cured at 100 degrees C in contact with acrylic resin polymer teeth. The specimens were ground net and polished to a thickness of 0.21 mm for the examination of the interface with a light microscope. The surface of the specimens n as then treated with the solvent tetrahydrofuran, and the specimens were examined with a scanning electron microscope (SEM). Results. As a result of grinding, the inner parts of the beads at the interface of the teeth were exposed to the denture base polymer. The inner part in these polymer beads of the polymer teeth swelled to a depth of 3 mu m when the autopolymerized polymer was cured at 30 degrees C. When cured at 70 degrees C, the thickness of the swelled layer was 21 mu m (p < 0.001). Microscopically, the interface between the heat-cured denture base polymer and the polymer teeth appeared diffuse in the region of the interpenetrating polymer networks (IPN) and the matrix. The IPN appeared as a separate zone in the outer parts of the beads of the teeth, both with the light microscope and with the SEM. Conclusions. The results suggest that by increasing the polymerization temperature, the monomers of the denture base polymers diffused more effectively into acrylic resin polymer teeth. This increases the bond strength between the polymer teeth and the denture base polymer.