Background: Bisphosphonates are indicated for the treatment of osteoporosis. However, they could have an adverse effect on specific sites, such as the bisphosphonate-related osteonecrosis of the jaw. The aim of this study is to investigate the effect of etidronate on the resorption and apposition sides of the periodontium in ovariectomized rats.
Methods: Twenty-four female Wistar rats were randomly subjected to either ovariectomy or sham operation. After 8 weeks, six animals of each group were sacrificed. The other 12 rats received 5 mg/kg/day etidronate subcutaneously during 4 weeks. Tartrate-resistant acid phosphatase reaction and immunohistochemical staining for receptor activator of nuclear factor-κB (RANK), RANK-ligand (RANKL), osteoprotegerin (OPG), and osteocalcin was performed. Immunoreactivity was evaluated using a semiquantitative analysis.
Results: In ovariectomized rats, osteoclasts were noticed in the root socket of molars, including the apposition side of the periodontium, in which RANKL expression was significantly evidenced. In the etidronate-treated group, OPG expression was significantly expressed and osteoclasts that were noticed in the resorption side remained undetected in the apposition side even under ovariectomy. RANK was significantly expressed in ovariectomized rats treated with etidronate. Osteoid formation and osteocalcin expression were described on the alveolar bone surfaces in etidronate-treated rats, with or without ovariectomy.
Conclusions: Etidronate has specific site and bone cell actions in the periodontium. It inhibits the osteoclast differentiation induced by ovariectomy in the apposition side of the periodontium but maintains bone formation over all the socket surfaces. Such specificity may be related to the pathogenesis of the bisphosphonate-induced osteonecrosis of the jaw.