A morphological and quantitative study of osteoclast changes during the progress of periodontitis in the hamster

Since macroscopic bone loss in hamster periodontitis appears to be a continuous process, this study was undertaken to evaluate whether osteoclastic resorption is continuously activated or whether another pattern of activation occurred during the course of the disease. At the beginning of the experimental period, 5 male golden hamsters were killed; they were used as to controls. Forty other animals were then distributed into 2 equal groups. In the experimental group, periodontitis was induced by using the Keyes 2000 diet. Five animals in both control and experimental groups were killed at 45, 90, 135 and 180 days. The following parameters were quantitated in the mandibles: - the macroscopic bone loss, - the number of osteoclasts in contact or lying at a distance from bone, and - the number of nuclei per mm of bone surface. Control animals developed spontaneous, slowly progressing periodontitis. In the experimental animals, osteoclasts were more numerous along the periosteum than along the endosteal surfaces. The mean increase in active osteoclasts appeared to be almost stable throughout the experimental period after an initial marked increase along the periosteum. However from the morphological data, when each animal was examined individually, it appeared that osteoclastic activity varied from place to place along the bone surfaces. These findings, further supported by the large quantitative intra-group variations that we observed in this study as well as in our previous studies, suggested that although the disease progressed regularly at the macroscopic level, osteoclastic activity was rather discontinuous and recurrent.