Ultrastructural morphology of vascular endothelial junctions in periodontal ligament

The TEM was used to categorize vessels and their junctions in normal and tensioned rat maxillary molar periodontal ligament. In tensioned periodontal ligament mean luminal diameters of capillaries were significantly smaller (p < 0.001). Goniometer tilting of sections with apparent tight regions revealed that only 16 per cent were actual tight junctions. The other regions proved to be close junctions (85 per cent) and open junctions (4 per cent). No gap junctions were found. These findings establish that morphologically the periodontal ligament contains a microvascular bed of 'leaky' endothelium with a potentially high permeability factor.