A transmission electron-microscope stereological study of the blood vessels, oxytalan fibres and nerves of mouse-molar periodontal ligament.

Mandibular, mesiobuccal ligament was sectioned from the alveolar crest to the apex at predetermined levels. Data collected using standard point counting procedures was analysed for main effects due to animal, side of mouth, depth and zone across the ligament. Statistically-significant variations only occurred between different lateral thirds with the middle third containing the most oxytalan fibres and the bone third the greatest vascular and neural volumes. Stereology showed that the ligament was 3-7 times more vascular than other connective tissues. Eighty-eight per cent of the periodontal blood volume was enclosed in vessels with a mean lumenal diameter of 20.9 microns and characterized by a thin endothelial lining and few perivascular cells. These vessels had a surface density of 125.1 cm2/cm3. Oxytalan fibres had a length density of 1258 X 10(3) cm/cm3 and a mean caliper diameter of 0.7 micron. Furthermore, 78 per cent of fibres were adjacent to cells, 14 per cent within principal collagen fibres and 8 per cent in the walls of blood vessels. The length density of nerves within the ligament was 255.9 X 10(3) cm/cm3. Unmyelinated axons constituting 95 per cent of periodontal nerve fibres had a mean caliper diameter of 1.4 micron.