Morphological studies on periodontal disease in the cynomolgus monkey

Histological observations were made on ligature‐induced periodontitis in two adult female monkeys ( Macaca fascicularis ). Silk ligatures were placed around posterior teeth and the shift from gingivitis to periodontitis was followed radiographically and bacteriologically for eight and nine weeks, respectively. Fifteen tissue blocks with ligatures in situ were obtained. Following decalcification with EDTA and epon embedding, sections one micron in thickness were prepared in the mesio‐distal plane to study the interproximal regions. Two additional blocks were processed for routine histology. Radiographically, progressive bone loss was observed in the interproximal regions that had a ligated tooth surface. Histologically, prominent features included supragingival and subgingival plaque (with dense accumulations of bacteria around and within the ligature), apical migration of the junctional epithelium, loss of collagen and connective tissue attachment, and osteoclastic bone resorption. A chronic inflammatory reaction was evidenced by a dense infiltration of leukocytes in the connective tissue, with a high proportion of plasma cells. Numerous polymorphonuclear leukocytes were seen in pathways between epithelial cells and in a zone around the plaque‐laden ligature. These morphological observations, similar to descriptions of human periodontitis, lend support for the usefulness of this model in the study of human periodontitis.