THE VASCULATURE OF THE PERIODONTAL-LIGAMENT - A SCANNING ELECTRON-MICROSCOPIC STUDY USING CORROSION CASTS IN THE RAT

THE PURPOSE OF THIS STUDY WAS TO EXAMINE the 3-dimensional architectur e of the microvascular system of the rat periodontal ligament (PDL). V ascular corrosion casts were prepared and examined by scanning electro n microscopy. Cervically, arterioles and venules communicated with the profuse capillary network of the gingiva. The mid-root segment of the PDL contained arterioles and venules that mainly coursed occluso-apic ally near the alveolar wall, as well as capillary loops located closer to the root surface. Arterioles entered the PDL through vascular cana ls from the bone marrow, then coursed coronally and branched into an i nterconnected network of capillaries. The capillaries formed hairpin l oops pointing coronally. At the tip, the capillary loops were enlarged in diameter and had an irregular luminar surface. The capillaries the n coursed apically, anastomosing freely, until entering a venule. Larg e venules mainly followed a coronal-apical path, giving the PDL vascul ature a palisade-like appearance. These vessels either left the PDL th rough vascular canals in the alveolar wall or connected in an apical, venous cap with venules exiting through the apical foramen. The result s show that the microvasculature forms a highly organized system presu mably related to the specialized functions of the periodontium. Cervic ally, a dense capillary system may be required for antimicrobial defen se and rapid tissue turnover. The vasculature in the middle segment su pports the suspensory structures, while the venous cap in the apical r egion may be designed to cushion masticatory forces. The large vessel diameter combined with an irregular lumina surface at the tip of capil lary loops indicates reduced blood velocity and turbulence in the func tional part of the PDL vasculature where exchange of metabolites mainl y occurs.