A MORPHOMETRIC, ELECTRON-MICROSCOPIC ANALYSIS OF TISSUE CHANNELS SHOWN BY IONIC TRACER IN NORMAL AND TENSIONED RAT MOLAR APICAL PERIODONTAL-LIGAMENT

A 1.0 newton continuous, extrusive load was applied to the right maxillary molar for 30 min to determine the presence of channels as shown by the distribution of tracer across the interstitial compartment of normal and tensioned PDL. Sodium ferrocyanide (1% w/v), perfused via the common carotid arteries, was the tracer probe and tris(ethylenediamine) cobalt III chloride (1% w/v) the precipitating ion. Left molar control PDL had an overall mean of 0.43 ± 0.05/μm2 tissue channels at 0.2 μm m from the vascular endothelium, and 0.15 ± 0.04/μm2 at 7-8 μm. On the experimental side, the overall mean number of tissue channels was 0.65 ± 0.13/μm2 at 0-2 μm and 0.19 ± 0.07/μm2 at 7-8 μm. A significant depth effect (P < 0.01) was present in the control and experimental interstitial tissues for tissue channels adjacent to the endothelium of different categories of vessel. Extrusion increased the tissue channel density adjacent to arterial capillaries (P < 0.01), venous capillaries (P < 0.01) and postcapillarysized venules (P < 0.01). These findings implicate these three types of vessel as being functionally important in fluid exchange across endothelial boundaries in the PDL. © 1990.