CELLULAR COLONIZATION AND BONE-FORMATION INTO EXPANDED POLYTETRAFLUOROETHYLENE MEMBRANES - A LIGHT-MICROSCOPIC AND HISTOCHEMICAL TIME-COURSE STUDY IN THE RABBIT

WE REPORT ON A TIME COURSE STUDY of cellular colonization of expanded polytetrafluoroethylene (ePTFE) membranes in rabbits. Bone defects (8 mm) were prepared with low speed burs in rabbit tibial metaphyses and covered with ePTFE membranes. The membranes were retrieved after 3, 6, 9, and 12 weeks. At 3 weeks, all membranes were filled by cells and o steoid tissue: no mineralized tissue was found. Osteoblasts positive f or alkaline phosphatase (ALP) were observed on the outer surface and i nside the material interstices of the membrane. At 6 weeks, it was pos sible to observe an increase of the quantity of the osteoid material i nside the membranes. At 9 weeks, bone tissue was present and it usuall y originated from the most external part of the membrane, and spread t o the central part of the membrane. Only the central portion of this b one appeared to be completely mineralized. A sharp decrease in the num ber of ALP-positive osteoblasts was observed. At 12 weeks, the quantit y of bone present appeared to be substantially increased. Only a small percentage of the bone inside the membrane appeared to be completely mineralized. No cells positive to acid phosphatase were observed. Thes e histological results confirm the high biocompatibility of ePTFE memb ranes and the bone formation inside the ePTFE interconnected nodes cou ld, probably, help in achieving a good biomaterial-tissue integration with predictable results in bone regeneration.