Purpose: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is rare but severe adverse effect in patients receiving bisphosphonates. Anti-angiogenesis, which affect wound healing in soft and hard tissue, has been believe to be one of main causes of ONJ since 2003. The aim of this study was to investigate the effect of anti-angiogenesis on tooth extraction wound healing in mice.

Materials and Methods: C57B6/J mice received zoledronate (ZA), cyclophosphamide (CY), and combination of ZA and CY (CY/ZA) for 5 and 7 weeks. Both maxillary first molars were extracted at 3 weeks after the initiation of drug administrations. Euthanasia was performed at 72 hours, and 2 and 4 weeks after tooth extraction. Saline was used as control (VC) (n=7 per each group). Monoclonal anti-VEGFA antibody was administered for 14 days just after tooth extraction (Mab, n=4). MicroCT, histomorphological, immunohistochemical and qPCR analyses were performed.

Results: All wounds in ZA/CY were opened at 4 weeks after tooth extraction. No wound open was noted in VC, ZA and CY at 4 weeks. Suppressed collagen production and more infiltration of polymorphonuclear cells were noted in ZA/CY at 4 weeks after tooth extraction. Interestingly, blood vessel formation was significantly suppressed in both ZA/CY and CY at 2 and 4 weeks, although soft tissue healing was completed and impaired in CY and CY/ZA, respectively. Moreover, all wounds were healed at 2 weeks after tooth extraction in Mab group although Mab therapy significantly suppressed blood vessel formation. Anti-inflammatory related-gene expressions and M2 macrophages were significantly suppressed in CY/ZA, but not VC, ZA, and CY at 72 hours and 4 weeks after tooth extraction.

Discussion: Our findings strongly suggested that suppression of blood vessel formation in soft tissue around extraction sockets were not triggering factor of BRONJ. Immunosuppression may strongly contribute to induction of BRONJ in mice.