Blood volume in human bicuspid periodontal ligament determined by electron microscopy

The microvascular volume of periodontal ligament is reported to range from 1.63 to 3.5% in man, whereas that of animals varies from 7.5 to 11.5%. This transmission electron-microscopic investigation was undertaken to determine stereologically the volume in human periodontal ligament. The hypothesis tested was that the ligament blood volume in man is similar to that in animals. Left and right segments of mandible containing first and second premolars came from an adult burns’ victim who underwent jaw reconstruction. The segments were immersion-fixed in 2.5% glutaraldehyde, demineralized at 4°C in 0.1 M EDTA and processed for microscopy. Segments of distal periodontal ligament were sectioned at 150-μm intervals from the alveolar crest to the root apex and random tissue quadrats recorded for point counting and data analysis using a generalized linear-regression statistical model. Mean adjusted microvascular luminal volume was 9.52±2.28% (SEM) and the abluminal volume 12.91±2.76%; the wall volume was 3.39%. Significant differences existed between the luminal and abluminal volumes of the different vessel types (p<0.05) and their distribution across the circumferential thirds of the ligament (p<0.05). Total length density of the blood vessels was 149.84×103 cm/cm3 and the surface density 330.19 cm2/cm3. Postcapillary-sized venules held 69.1% of the total blood volume and provided 49.3% of the luminal surface area. Venous capillaries were the most common vessel, comprising 48.5%, and they contributed 71.5% of the overall length density. This study confirmed the hypothesis for the blood volume in the periodontal ligament in man. Blood volumes do not reflect the configurations of microvascular beds.