Ultrastructure of plaque associated with polytetrafluoroethylene (PTFE) membranes used for guided tissue regeneration

The purpose of the study was to examine the ultrastructure of plaque contaminating polytetrafluoroethylene (PTFE) membranes used for guided periodontal tissue regeneration. 8 patients treated with Gore-Tex membranes received daily antibiotics (650 mg x 2 Femepen) and rinsed with 10 ml 0.2% chlorhexidine during a healing period of 30 days. Following retrieval, the membranes were processed for electron microscopy. External aspects of 12 portions from 4 partially exposed membranes were selected for detailed ultrastructural examination. The plaque-membrane interface was characterized by the presence of fibrin or discontinuous accumulation of intermicrobial matrix. Adjacent plaque-free areas of membrane surface exhibited no detectable electron-dense material. 3 structurally different groups of bacterial aggregations were observed on the strips: (i) dense layers of gram-positive cocci and rods dominated the external aspect of the open microstructure portion; (ii) cocci, rods and filamentous microorganisms embedded in fibrin filled the spaces of the open microstructure; (iii) a loosely arranged mixed microbiota consisting of gram-positive cocci and rods as well as of gram-negative microorganisms and spirochetes were present on the occlusive portion. Areas with morphologically intact bacteria alternated with areas with empty bacterial cell walls. One specimen also displayed degenerated Candida-like blastospores. This study shows that oral micro-organisms may colonize and extensively invade the open microstructure of PTFE material and that adhesion of plaque to the membrane surface is mediated either by fibrin or a discontinuous layer of intermicrobial matrix.