The artificial restoration of a dental root

Periodontal ligament (PDL) cells, osteoblasts (OB), and gingival (GIN) cells originating from human periodontium were co-cultured indirectly with human peripheral blood lymphocytes (PBL). The formation of osteoclasts (OC) from each the co-cultured PBL was compared with a standard PBL culture. A marked suppression of OC formation was observed in PBL co-cultured with PDL cells, and an enhanced OC formation was observed in PBL co-cultured with OB and GIN cells, when compared with the standard PBL culture. The suppressing activity of PDL cells and the enhancing activity of OB and GIN cells on the formation of OC derived from PBL were also found, when the co-culture fluids of PDL/PBL, OB/PBL, and GIN/PBL were added to PBL, and the numbers of OC were counted after 7 days' incubation. Furthermore, the alkaline phosphatase (ALPase) activity of PDL cells was stimulated by co-culturing them with PBL, and the ALPase activity of OB and GIN cells was inhibited by co-culturing them with PBL. When PDL cells were seeded on the surfaces of titanium discs and incubated at 37 degrees C in a 5% CO2 incubator, PDL cells could adhere faster onto titanium surfaces that were coated with a cell-and-tissue-adhesive substance than onto non-coated titanium surfaces. These cultures formed a confluent monolayer on the surfaces of titanium discs by means of an autologous serum containing alpha MEM. These results clearly suggest that the periodontal ligament is a specifically differentiated tissue whose function is to protect alveolar bone from bone resorption due to biting force.(ABSTRACT TRUNCATED AT 250 WORDS)