Structural organization and fine distribution of lymphatic vessels in periodontal tissues of the rat and monkey: a histochemical study.

The structural organization and fine distribution of lymphatic vessels in the periodontal tissues (gingiva, periodontium and alveolar process) were examined by light and electron microscopy using an enzyme-histochemical method. Whole mount preparations of periodontal membranes peeled from the teeth and cryostat sections of normal or decalcified tissues treated with EDTA were double-stained using 5'-nucleotidase (5'-Nase)-alkaline phosphatase (ALPase) and examined by light microscopy. This staining procedure allowed the lymphatic vessels in the periodontal tissue to be differentiated from blood vessels. Well-developed 5'-Nase-positive lymphatics were observed in the gingiva and periodontium. The histochemical aspects of 5'-Nase activity in lymphatic vessels are discussed in detail, with special reference to the supply of Mg++ ions. A network of 5'-Nase-positive lymphatics was observed in whole mount preparations of the periodontal membrane for the first time. This network was also observed in the tissue sections. More 5'-Nase-positive lymphatics were seen in the root area of the periodontium than in the cervical area. 5'-Nase-positive lymphatics in residual tissue blocks remaining after cryostat sectioning and in whole mount preparations were highlighted with good contrast and resolution on backscattered electron images produced by scanning electron microscopy. Dense granular precipitations resulting from the 5'-Nase reaction were observed on the luminal surface of the lymphatic endothelial cells as well as on the basal side but were absent in the blood vessels.