INHIBITORY EFFECTS OF A BISPHOSPHONATE (RISEDRONATE) ON EXPERIMENTAL PERIODONTITIS IN RATS

The present study was designed to examine whether systemic administrat ion of a bisphosphonate, risedronate, could prevent alveolar bone reso rption in rats with experimental periodontitis. On Day 1, an elastic r ing was placed around the neck of the right mandibular Ist molar to in duce inflammatory periodontitis. The animals were given daily injectio ns of either 0.9% NaCl (control group), or 0.8, 1.6 or 3.2 mu moles/kg (s.c.) of risedronate (experimental groups) from Days 1 to 7, and wer e killed on Day 8. Histological examinations and determination of bone mineral density in the interdental area between the 1st and 2nd molar s with an image analyzer revealed that the presence of the elastic rin g induced a loss of attachment and bone resorption in the control grou p. Vigorous bone resorption, with appearance of a large number of oste oclasts, was observed in the interdental and bifurcation areas. In the experimental groups, however, the resorption of alveolar bone and the loss of bone mineral content in these areas were prevented in a dose- dependent fashion, especially at doses of 1.6 and 3.2 mu moles/kg. Man y osteoclasts were detached from the surface of the alveolar bone and had degenerated appearances, such as rounded shapes, loss of polarity and pyknosis. These results suggest that administration of risedronate is effective in preventing bone resorption in periodontitis.