[Ultrastructure of the lymph capillaries in human dental pulp]

The purpose of this article is to observe the ultrastructures of the lymph capillaries in the human dental pulps.

Investigations have been performed on dental pulps from 8 human permanent teeth, including 4 mandibular first premolars and 4 maxillary first premolars, which were extracted for orthodontic reason. As soon as possible, we cleaved the teeth longitudinally and immersed in the fixative solution at 4 degrees C for 1 hour, then kindly removed the pulps and immersed in the same fixative solution for 3 hours, then routinely postfixed, dehydrated, embedded, and prepared the ultrathin sections (50-70 nm) without semithin section localization. The lymph vessels were distinguished from blood vessels on ultrathin sections by their morphological features.

We have observed three fundamental kinds of intercellular junctions, overlapping(51%), end to end(36.1%), and interdigistating (10.6%). A few complex junctions also could be seen, but we failed to find the open junction. The Weibel-Palade bodies were occasionally present in the lymphatic vessels endothelial cells of young dental pulps. And we even found the lipofuscins in the cytoplasm of the endothelium. Some inclusion bodies, such as paracrystalline inclusions and myeloid bodies, also could be seen. There were many micropinocytotic vesicles in the cytoplasm of the lymphatic endothelium, the diameter of the most vesicles was about 50-80 nm, some was about 100-500 nm. Some vesicles appeared to lie free within the cytoplasm, and some were seen to touch or open onto the luminal or abluminal surfaces of the endothelia, which suggested that many vesicles were not simple discrete units but rather from parts of chains that reached either luminal or abluminal surfaces. It was reported that micropinocytotic vesicles, open junctions and intraparietal channels provided fluid transport.

Dental pulp is a special organ, and the lymph capillaries in it have their own ultrastructural features.