Histomorphometric Study of the Periodontal Vasculature of the Rat Incisor

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Abstract
This study assessed quantitatively the vascular system in the cementum-related periodontal ligament (PDL) along the rat incisor. The lower left incisors of six rats (± 200 g) were subjected to routine histological procedures and cross-sectioned serially (2 μm), and the distance between each section and the apex was computed. The PDL of five sections at different levels along the tooth was divided into mesial, lingual, and lateral parts. The number and area of small and terminal arterioles, capillaries (C), sinusoids (S), post-capillary venules (PCV), and connecting venules, as well as the area of the PDL, were established. Blood vessels (BV) occupied 47 ± 2% of the PDL area in the apical half and 4 ± 2% at the incisal end. Of the total BV area, 41%, 32%, and 27% were located on the lingual, mesial, and lateral tooth sides, respectively. The majority of BV belonged to the venous system (98.5 ± 0.6% and 82.5 ± 3.0% in the apical and incisal parts, respectively). The apical venous system comprised 95.4 ± 1.6% S and 3.2 ± 1.0% PCV, reversing to 27.2 ± 14.2% S and 55.2 ± 11.3% PCV in the incisal half. The number of arterial profiles increased gradually from 6.8 ± 1.5 at the apex to 25.3±2.4 in the incisal part and that of C from 9.0 ± 1.18 to 25.0 ± 4.3. The extensive vascularization in the apical half of the PDL is consistent with the high metabolic demands and with the need for protective cushioning of the constantly growing dental and periodontal tissues. The paucity of blood supply and the presence of numerous small BVs in the incisal end equate with the metabolic needs of the highly organized supporting tissue in this region.