ULTRASTRUCTURAL MORPHOLOGY OF VASCULAR ENDOTHELIAL JUNCTIONS IN PERIODONTAL-LIGAMENT

The TEM was used to categorize vessels and their junctions in normal a nd tensioned rat maxillary molar periodontal ligament. In tensioned pe riodontal ligament mean luminal diameters of capillaries were signific antly smaller (p<0.001). Goniometer tilting of sections with apparent tight regions revealed that only 16 per cent were actual tight junctio ns. The other regions proved to be close junctions (85 per cent) and o pen junctions (4 per cent). No gap junctions were found. These finding s establish that morphologically the periodontal ligament contains a m icrovascular bed of 'leaky' endothelium with a potentially high permea bility factor.