Short - term effects of occlusal hypofunction following antagonist tooth extraction upon periodontal tissues in the rat.

This histological study was designed to observe the early effects of occlusal hypofunction on periodontal tissues. Eighteen Wistar rats were used. Hypofunction was induced by extracting the right maxillary molars. Histological observations were reported on the right lower jaws which were embedded in methyl-metacrylate, sectioned at 4 micrometer without decalcification and stained with toluidine blue. The periodontal ligament disorganization began after 2 days and continued until 16 days. The outstanding observation was a considerable increase in bone formation, which was responsible for ligament narrowing as no change in cementoblastic activity was observed. At the top of the interradicular septa, the osteoblastic proliferation began at 24 hours, and bone mineralization increased until 4 days creating osteophytic bone, and then decreased. On the modelling sides of the sockets, a great amount of osteoid tissue deposited by osteoblasts set around large vessels was present at 4 days, and mineralization extended between 4 and 8 days. On the remodelling sides, bone formation extended at 4 days and osteoclastic resorption fell of except along oblique roots sockets; then the remodelling sides returned to nearly normal aspect at 16 days. The biological significance and clinical implications of these findings are discussed.