Effect of inflammation on collateral circulation of the gingiva

The effect of inflammation on collateral circulation of the gingiva and the vasculature of the periodontal ligament was studied in 12 squirrel monkeys. Gingival inflammation was induced by tying silk ligature at the cervical area of mandibular bicuspids and molars to encourage plaque accumulation. At 2, 10 and 26 weeks after ligature placement the animal's vasculature was perfused with India ink and calf serum. Nonligatured bicuspids and molars from the same animals served as controls. At all time points, on all experimental tooth surfaces examined, the vascularity (% grid intersections falling over vessel lumen) of the cervical portion of the periodontal ligament was significantly higher than the controls. The number of vessels connecting vessels of the periodontal ligament with supracrestal vessels was also significantly higher. There was a tendency for the number of vessels perforating either the alveolar bone proper or the alveolar crest to increase when inflammation was induced. The results of this study demonstrate the development of collateral circulation from the periodontal ligament to the gingiva in response to inflammation and help to explain the extension of inflammation into the deeper structures of the periodontium, including the periodontal ligament.