TISSUE-RESPONSE TO COMMERCIAL SILICONE AND POLYURETHANE ELASTOMERS AFTER DIFFERENT STERILIZATION PROCEDURES

Two different commercial polymeric materials, a silicone and a polyure thane (PUR), were studied with regard to correlations between the chem ical and physical compositions of the polymer surfaces and the biologi cal response on implantation. Test specimens of the materials were man ufactured according to standard procedures. The specimens were implant ed in rats for 10 and 90 days. Before implantation the polymers were s terilized in three different ways, namely, beta irradiation, ethylene oxide sterilization and steam sterilization. The polymers were charact erized before and after the implantation with respect to the chemical composition and the morphology of the surfaces. After implantation the biological response was evaluated by counting numbers of macrophages, giant cells, fibroblasts and other cells present at the surfaces. The thickness of the fibrous capsule surrounding the test specimens was m easured at the thickest and thinnest parts. PUR surfaces showed signs of degradation already after sterilization and after 10 to 90 days of implantation, pits and cracks appeared, especially in the ethylene oxi de sterilized samples. However, differences in the biological response s were small and independent of the sterilization method. After 10 day s of implantation the capsule thickness and the amounts of cell materi al adhering at the surfaces were different, and it appears that the si licone rubber induces more tissue response than PUR. The differences i n the early tissue response evened out after 90 days implantation time and a steady state situation evolved, which was similar for the silic one and the polyurethane. (C) 1996 Elsevier Science Limited.