The periodontal microvasculature--a morphological and morphometric study.

Various ultrastructural studies on the periodontal ligament (PDL) microvasculature have been reported. However, the lack of a systematic classification has led to much confusion in the terminology used to define vessel types. On the basis of morphological criteria, the author proposes that 3 vessel types are present in the PDL: terminal arterioles (Type A vessels), capillaries (Types B-1 & B-2) and postcapillary venules (Type C vessels). Morphometric analysis of the apical PDL revealed that the total vascular volume was 19.9%. Type C vessels predominated with a vascular volume of 16.4% while the other 2 vessel types made up the remainder of the vascular volume. The results of this study suggest that the apical PDL region is predominantly venous. Introduction By use of the SEM methacrylate corrosion cast technique[1] and transmission electron microscopy[2,3] in a variety of animal models, various types of microvascular segments have been described in the periodontal ligament (PDL). These include arterioles, venules, sinusoids, lymphatics and capillaries. However, a feature common to these studies was the lack of a systematic classification of the PDL blood vessels. Furthermore, the authors have not always defined their criteria for categorization of vessel types. Estimates of the vascular volume in selected regions of the PDL range from 1-2%[4] to 22%[5]. It is generally agreed that the vascularization is densest in the apical region of the PDL[6,7]. However, the relative proportions of vascular types have not been reported. The objective of this study was to derive an ultrastructural classification system for the PDL microvasculature and to determine morphometrically the vascular volume of different vascular types using the rat molar periodontal ligament as a model. Faculty of Dentistry, National University of Singapore, National University Hospital, Lower Kent Ridge Road, Singapore 0511.