Histomorphologic characteristics of bisphosphonate‐related osteonecrosis of the jaw

Background Bisphosphonate‐related osteonecrosis of the jaw ( BRONJ ) is a known side effect of the therapy with bisphosphonates. No specific pathologic aspects or histological features are included in the most current definition. This study investigates characteristics of BRONJ with a special emphasis on histomorphologic aspects, evaluating the role of A ctinomyces spp. as well as other disease‐promoting factors in a formal pathogenetic context. Methods We investigated 23 patients (14 female, nine male; mean age: 66 ± 11.8 years) who received bisphosphonates with a gender‐ /age‐matched control group. Tissue specimens were treated according to local standards and analyzed histologically. Results In 18 (78.3%) BRONJ cases, we found A ctinomyces spp. colonies. Bone remodeling could be found in three specimens (13%). Eight specimens (34.8%) showed signs of epithelial proliferation. Analysis of dental treatment before the onset of BRONJ did not reveal significant differences ( P  >   0.20). In 10 patients (83%; P  >   0.05) of the reported cases a relationship between dental treatment and the occurrence of a purulent bone necrosis could be observed. Statistically significant differences in thickness of trabeculae were detected between the two study groups ( P  =   0.04). Conclusions This study demonstrates the important influence of the osteoblast–osteoclast balance in a histomorphologic analysis. Together with cofactors, which are able to trigger the onset of BRONJ , a new pathogenesis model was developed.