TISSUE-REACTIONS TO BIODEGRADABLE AND NONDEGRADABLE MEMBRANES PLACED TRANSCUTANEOUSLY IN RATS, OBSERVED LONGITUDINALLY OVER A PERIOD OF 4 WEEKS

The aim of this study was to observe the tissue responses to a number of membrane materials processed for use in guided tissue regeneration at different time periods. Non-degradable Gore-Tex(R) PTFE membrane an d degradable polylactic acid (PLA) membranes were placed transcutaneou sly in surgical incisions made in the dorsum of rats. The tissue respo nses to these materials were observed histologically at 3 days, 1 week and 4 weeks after placement. A wide variation in the tissue responses to both materials was evident at each time period. These variations c ould not be attributed to different rates of healing over time, but ra ther to more complex factors. These factors may include differences in host responses between different animals, local factors pertaining to specific site variations, physical characteristics of the materials l ike surface texture, and contamination from the wound surface. Neither membrane material was found to be totally satisfactory. The PLA membr anes were well tolerated by the tissues but they were unevenly absorbe d within 2 weeks of placement. The Gore-Tex PTFE membranes, however, w ere associated with prolonged acute inflammatory infiltrate throughout the duration of the study, indicating that they were less well tolera ted by the tissues than the PLA materials. As the healing characterist ics of tissues are complex and highly variable, and as neither the non -degradable PTFE or degradable PLA membranes demonstrated ideal tissue responses, it is concluded that variations in clinical responses to t hese materials used in regeneration techniques must be anticipated.