Tooth extraction in mice administered zoledronate increases inflammatory cytokine levels and promotes osteonecrosis of the jaw.

INTRODUCTION: Osteonecrosis of the jaw (ONJ) occurring after invasive dental treatment often adversely affects patients' activities of daily living. Long-term administration of strong anti-bone resorptive agents such as bisphosphonates prior to invasive dental treatment is considered an ONJ risk factor; however, pathological mechanisms underlying ONJ development remain unclear. MATERIALS AND METHODS: We developed an ONJ mouse model in which a tooth is extracted during treatment with the bisphosphonate zoledronate. RESULTS: We observed induction of apoptosis in osteocytes, resulting in formation of empty lacunae in jaw bones at sites of tooth extraction but not in other bones of the same mice. We also observed elevated levels of inflammatory cytokines such as TNFα, IL-6 and IL-1 in jaw bone at the extraction site relative to other sites in zoledronate-treated mice. We also report that treatment in vitro with either zoledronate or an extract from Porphyromonas gingivalis, an oral bacteria, promotes expression of inflammatory cytokines in osteoclast progenitor cells. We demonstrate that gene-targeting of either TNFα, IL-6 or IL-1 or treatment with etanercept, a TNFα inhibitor, or a neutralizing antibody against IL-6 can antagonize ONJ development caused by combined tooth extraction and zoledronate treatment. CONCLUSIONS: Taken together, the cytokine storm induced by invasive dental treatment under bisphosphonate treatment promotes ONJ development due to elevated levels of inflammatory cytokine-producing cells. Our work identifies novel targets potentially useful to prevent ONJ.

Factors affecting the quality of life of patients with medication-related osteonecrosis of the jaw during treatment: A quality-of-life survey and causal analysis.

This prospective cohort study aimed to investigate the impact of medication-related osteonecrosis of the jaw (MRONJ) on health-related quality of life (HRQOL) and oral health-related QOL (OHRQOL) and the association between the downstaging of MRONJ and OHRQOL. The HRQOL and OHRQOL of 44 patients with MRONJ were assessed using the SF-36v2 and the General Oral Health Assessment Index (GOHAI), respectively. Treatment was performed in accordance with the AAOMS position paper (2014). The SF-36v2 and GOHAI scores at the beginning of the survey were used to evaluate the impact of MRONJ on QOL. Potential confounders affecting the association between downstaging and QOL improvement were selected using directed acyclic graphs. Multiple regression analysis was performed to evaluate causal inferences. HRQOL scale scores declined below the national average. The three-component summary score (3CS), comprising the physical component summary (PCS), mental component summary (MCS), and role/social component summary (RCS), revealed that performance status and primary disease significantly affected the PCS and RCS (P = 0.005 and P < 0.001, respectively) and PCS and MCS (P = 0.024 and P = 0.003, respectively). The MRONJ stage did not influence the 3CS; however, OHRQOL declined in a stage-dependent manner (P = 0.005). Downstaging of MRONJ was independently associated with the improvement rate of the total GOHAI scores after adjusting for variables (P = 0.045). The HRQOL of patients with MRONJ declined; however, this may depend on the underlying disease status rather than the MRONJ stage. Improvement of the disease status can potentially predict an improvement in OHRQOL, regardless of the treatment modality.

Osteonecrosis development by tooth extraction in zoledronate treated mice is inhibited by active vitamin D analogues, anti-inflammatory agents or antibiotics.

Invasive dental treatment such as tooth extraction following treatment with strong anti-bone resorptive agents, including bisphosphonates and denosumab, reportedly promotes osteonecrosis of the jaw (ONJ) at the extraction site, but strategies to prevent ONJ remain unclear. Here we show that in mice, administration of either active vitamin D analogues, antibiotics or anti-inflammatory agents can prevent ONJ development induced by tooth extraction during treatment with the bisphosphonate zoledronate. Specifically, tooth extraction during treatment with zoledronate induced osteonecrosis in mice, but administration of either 1,25(OH)2D3 or ED71, both active vitamin D analogues, significantly antagonized osteonecrosis development, even under continuous zoledronate treatment. 1,25(OH)2D3 or ED71 administration also significantly inhibited osteocyte apoptosis induced by tooth extraction and bisphosphonate treatment. Administration of either active vitamin D analogue significantly inhibited elevation of serum inflammatory cytokine levels in mice in response to injection of lipopolysaccharide, an infection mimetic. Furthermore, administration of either anti-inflammatory or antibiotic reagents significantly blocked ONJ development following tooth extraction and zoledronate treatment. These findings suggest that administration of active vitamin D, anti-inflammatory agents or antibiotics could prevent ONJ development induced by tooth extraction in patients treated with zoledronate.

An ionic silver coating prevents implant-associated infection by anaerobic bacteria in vitro and in vivo in mice.

Currently, implants are utilized clinically for bone transplant procedures. However, if infectious osteomyelitis occurs at implant sites, removal of bacteria can be challenging. Moreover, altered blood flow at peri-implant infectious sites can create an anaerobic environment, making it more difficult to treat infection with antibiotics. Thus, it would be beneficial if implants could be modified to exhibit antibacterial activity, even in anaerobic conditions. Here, we show antibacterial activity of silver ions coated on titanium rods, even against the anaerobic bacteria Porphyromonas gingivalis (P. gingivalis), both in vitro and in vivo. Specifically, we implanted silver-coated or control uncoated titanium rods along with P. gingivalis in mouse femoral bone BM cavities and observed significantly inhibited P. gingivalis infection with silver-coated compared with non-coated rods, based on in vivo bio-imaging. Osteonecrosis by infectious osteomyelitis and elevation of the inflammatory factors C-reactive protein and IL-6 promoted by P. gingivalis s were also significantly reduced in the presence of silver-coated rods. Overall, our study indicates that silver ion coating of an implant represents a therapeutic option to prevent associated infection, even in anaerobic conditions or against anaerobic bacteria.

Elevation of pro-inflammatory cytokine levels following anti-resorptive drug treatment is required for osteonecrosis development in infectious osteomyelitis.

Various conditions, including bacterial infection, can promote osteonecrosis. For example, following invasive dental therapy with anti-bone resorptive agents, some patients develop osteonecrosis in the jaw; however, pathological mechanisms underlying these outcomes remain unknown. Here, we show that administration of anti-resorptive agents such as the bisphosphonate alendronate accelerates osteonecrosis promoted by infectious osteomyelitis. Potent suppression of bone turnover by these types of agents is considered critical for osteonecrosis development; however, using mouse models we found that acceleration of bone turnover by teriparatide injection did not prevent osteonecrosis but rather converted osteoclast progenitors to macrophages expressing inflammatory cytokines, which were required for osteonecrosis development. In fact, we demonstrate that TNFα-, IL-1α/ß- or IL-6-deficient mice as well as wild-type mice administered a TNFα-inhibitor were significantly resistant to development of osteonecrosis accompanying infectious myelitis, even under bisphosphonate treatment. Our data provide new insight into mechanisms underlying osteonecrosis and suggest new ways to prevent it.