Ultrastructural morphology of vascular endothelial junctions in periodontal ligament

Osseous Remodeling Around Dental Implants

Adequate bone remodeling may be a primary parameter for long-term successful complication-free dental implant treatment. A 1.8-mm osseous thickness around dental implants is thought to be the minimum thickness for adequate vasculature for osteocyte nutrition and function. A dental implant does not provide progenitor cells or angiogenic or osteogenic factors. Thus, the surrounding bone may need to have a 1.8-mm thickness to accommodate the vasculature necessary for nutrients for appropriate remodeling. Additionally, the 1.8-mm dimension may provide for mechanical load resistance. There is no evidence to illustrate the physiologic need for the 1.8-mm dimension. This dimension requirement is based on clinical outcome observations. Basic science research for bone survival around dental implants is needed.

Histomorphometric study of the periodontal vasculature during and after experimental tipping of the rat incisor

The periodontal vasculature encircling the entire length of the rat lower incisor was studied at the time of tipping movement and 3 months later. In 12 rats (212+/-4 g b.w.), loads (0.19+/-0.016 N) were applied to the lower left incisor in a linguointrusive direction. After 2 weeks of loading, six experimental animals were killed with the loading springs in place. The springs were removed in the six remaining rats, which were killed 12 weeks later. Six additional rats with intact teeth served as control. All incisors were fixed, demineralized, embedded in glycol methacrylate and cross-sectioned perpendicular to the long axis of the tooth. The distance of each section (2 microm) from the apex was calculated. A computerized image-analysis program was used to measure the width and area of the labial and lingual periodontal ligament to establish whether the measured segments corresponded to the compressed or expanded zones. In each cross-section, the various types of blood vessels were counted and the cross-sectional area of all venous vessels was measured. The results showed that after 2 weeks of loading (1) the general trend of vascular changes was similar under pressure and tension; (2) the large-diameter vessels were unaffected by loading; (3) the mean number of terminal arterioles had decreased significantly, while the number of capillaries and postcapillary venules had increased significantly in the apical tooth part; (4) the venous blood vessel area had decreased significantly in the apical tooth part; (5) the intensity of the vascular reaction was dependent on the degree of tissue distortion; and (6) after 12 weeks' recovery the vascular changes were still present, demonstrating a rebound effect. The findings suggest that microvascular alterations following tooth loading are not directly related to the spatial effect of loading itself and are of a much longer duration than expected.

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 degrees C in 0.1 M EDTA and processed for microscopy. Segments of distal periodontal ligament were sectioned at 150-micron 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 type (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 x 10(3) 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.