Effect of intermittent PTH administration in the periodontitis-associated bone loss in ovariectomized rats

Abstract

Parathyroid hormone intermittent administration has been considered to treat bone mass decrease in osteoporotic individuals. The present study evaluates whether PTH can affect alveolar bone loss in ovariectomized rats, since estrogen deficiency has been proposed as a risk factor for periodontal disease. Thirty female rats were set in groups: ovariectomized (Ovx) and Sham operated. Ovx were divided in two groups: Ovx-PTH (1-34) treated and Ovx, which received vehicle. After 1 week, cotton ligature was placed around one lower first molar of all animals to induce periodontal disease. Ovx treated received PTH doses of 40 microg/kg, three times a week for 30 days. After that, the animals were sacrificed, the mandibles extracted, X-rayed and samples prepared for histological evaluation. Histomorphometry was performed using image analyzer software. Scanning electron microscopy (SEM) of the tibias was also performed in all animals to evaluate possible changes in bone structure caused by the estrogen deficiency. Optical densities of the radiographs were measured by aluminum step-wedge equivalent thickness. Histomorphomery indicated the anabolic PTH effect in ovariectomized rats with significant inhibition of periodontitis manifestation (p<0.05) thus neutralizing the periodontitis inductor effects. The photo densitometry showed a lower mandibular optical density in the ovariectomized group that did not receive PTH (p<0.05). SEM image confirmed the early effect of estrogen deficiency in osseous tissue and PTH anabolic effect. PTH systemic intermittent administration was able to reduce alveolar bone loss in ovariectomized rats, despite the presence of a periodontal disease inductor and estrogen deficiency.