Distinct fibro-vascular arrangements in the periodontal ligament of the horse

SummaryObjective: riodontal ligament (PDL) of the hypsodont cheek teeth of the horse meets specific requirements of tooth support: (1) to fix the tooth; (2) to withstand pressure and tension during the laterolateral mastication movement; (3) to restore the original tooth position. These requirements are assumed to be met by the periodontal collagen fiber apparatus and by the vascular system. Distinct fibro-vascular arrangements are described here in order to reveal the structural prerequisites for these distinct functions. : ens from nine horses were processed for (1) collagen labeling with fluorescein, (2) oxytalan fiber staining, (3) immunostaining of smooth muscle actin, and (4) TEM examinations. s: vessels were found to be integrated in the PDL in three distinct ways:(1) : Groups of blood vessels were wrapped up in a sheath of so-called veil cells. I: Single venules were fixed, or anchored, in a very elaborate collagen fiber system. II: Wide, ballooned venules were integrated between collagen fiber bundles that ran parallel to the tooth surface. sions: eaths formed by veil cells (type-I arrangement) isolate distinct groups of blood vessels from deformations of the surrounding tissue. trast, the distinct fibro-vascular arrangements of anchored blood vessels (type-II arrangement) and ballooned venules (type-III arrangement) are assumed to accept the forces generated by masticatory tooth movements. The anchored blood vessels sustain tractive forces by means of what is called a lateral compression mechanism, whereas the ballooned venules act as a hemodynamic cushion.