Evaluation of the parathyroid hormone efficacy on bisphosphonate related osteonecrosis of the jaws in experimental animal model

The treatment of bisphosphonate related osteonecrosis of the jaws (BRONJ) is a difficult and complex pathology in oral and maxillofacial surgery. Recently, studies have been attempted various methods for the treatment of BRONJ, but has not been developed a fully secured protocol.In this study, it is aimed to investigate the effect of adjuvant parathyroid hormone on BRONJ after administration of the bisphosphonate that followed by the tooth extraction process.In this study, 36 Sprague-Dawley female rats were divided into four experimental groups. In group 1, 0.1mg/kg sterile saline (SF) and in group 2, 0.1mg/kg zoledronate (ZA), during a-8-week period for 3-times in a week was intraperitoneally (i.p.) injected and at the end of this period animals were sacrified. In group 3, 0.1mg/kg ZA, during a-8-week period for 3-times in a week was injected i.p., afterwards right first molar teeth were extracted and allowed 8 weeks for recovery, then the animals were sacrificed at the end of this period. In group 4, 0.1mg/kg ZA, during a-8-week period for 3-times in a week was injected i.p., afterwards right first molar teeth were extracted and 30µg/kg/day Parathyroid hormone (PTH) analogue was injected subcutaneously. At the end of this period animals were sacrified.The hemimandibles revealed for histologic and histomorphometric examination. Accordingly, the BRONJ ratio in tooth extraction groups was found to be significantly higher than the groups without tooth extraction (p<0.01). In addition, the incidence and the severity of the inflammation and BRONJ values in PTH applied group has been found to be lower than the group without PTH application, however this difference was not statistically significant.In conclusion, chronic bisphosphonate uptake that followed by tooth extraction have been identified to induce BRONJ development, on the other hand adjuvant PTH therapy has positive influences in the treatment of these lesions. However, before using this treatment in clinical application, more long term studies are required with larger dose and durations in experimental groups.Key words: Bisphosphonate related osteonecrosis of the jaws, inflammation, bone turnover, Parathyroid hormone, trauma