A PRELIMINARY-REPORT ON A METHOD FOR STUDYING THE PERMEABILITY OF EXPANDED POLYTETRAFLUOROETHYLENE MEMBRANE TO BACTERIA IN-VITRO - A SCANNING ELECTRON-MICROSCOPIC AND HISTOLOGICAL STUDY

THE TECHNIQUE OF GUIDED TISSUE REGENERATION using expanded polytetrafl uoroethylene (ePTFE) membranes has been shown to be effective in impla nt dentistry (bony defects, extremely thin alveolar ridges, and implan ts placed in fresh extraction sockets). One of the drawbacks associate d with the use of membranes is their premature exposure with consequen t bacterial contamination. The aim of this study was to examine the po ssibility that oral bacteria migrate through the occlusive portion of ePTFE membranes and to determine the time needed for microorganisms to pass from the outer surface to the inner surface of the membranes. A removable acrylic device was adapted to the molar-premolar region of o ne quadrant of the jaws in each of three volunteers. Five cylindrical teflon chambers were glued to the buccal aspect of each device. The ch ambers were divided into two rooms separated by the inner portion of a ePTFE membrane. The outer room was open to the oral cavity allowing p laque accumulation; the inner room was isolated from the oral cavity b y the ePTFE membrane. One of the 5 chambers was completely closed and used as control. The test period lasted for 4 weeks. Every week, one c hamber was removed from each device and processed for scanning electro n microscopic and histologic examinations. Our study showed the possib ility that oral bacteria may contaminate ePTFE membranes exposed to th e oral cavity. One specimen showed partial bacterial penetration after 2 and 3 weeks, but after 4 weeks, all membrane specimens demonstrated bacterial contamination. Complete bacterial penetration through the m embrane and contamination of the inner surface was observed in one spe cimen after 3 weeks and in two specimens after 4 weeks of exposure to the oral cavity. Therefore, the partially occlusive porosity of the me mbranes seems to be able to delay bacterial penetration through the me mbrane for approximately 3 to 4 weeks. After this time, prematurely ex posed membranes should probably be removed to prevent bacterial infect ion of the underlying regenerating tissues.