Is Bone Turnover of Jawbone and Its Possible Over Suppression by Bisphosphonates of Etiologic Importance in Pathogenesis of Bisphosphonate-Related Osteonecrosis?

Medication-related osteonecrosis of the jaw (MRONJ): a review of pathogenesis hypothesis and therapy strategies

Medication-related osteonecrosis of the jaw (MRONJ), a severe side effect caused by antiresorptive antiangiogenic medication, particularly bisphosphonates (BPs), has become a challenging disease with serious and profound effects on the physical and mental health of patients. Although it occurs with high frequency and is harmful, the exact mechanism of MRONJ remains unknown, and systematic and targeted approaches are still lacking. Maxillofacial surgeons focus on the etiology of osteonecrosis in the mandible and maxilla as well as the appropriate oral interventions for high-risk patients. Adequate nursing care and pharmacotherapy management are also crucial. This review provides a current overview of the clinicopathologic feature and research of MRONJ caused by BPs, with an emphasis on the potential mechanisms and current therapy and prevention strategies of the disease. We are of the opinion that an in-depth comprehension of the mechanisms underlying MRONJ will facilitate the development of more precise and efficacious therapeutic approaches, resulting in enhanced clinical outcomes for patients.

Zygomatic Implant Insertion in MRONJ: A Case Report with a Follow-Up of 3 Years

The oral rehabilitation of MRONJ patients represents a challenging situation. Conventional dental implant insertion is not indicated because of the risk of creating a new necrotic area. This case study describes the oral rehabilitation of a 78-year-old female patient, who developed an osteonecrotic lesion in the fourth year of bisphosphonate treatment. The patient underwent a series of surgeries, including resection of the necrotic tissue on the right maxillary region and removal of conventional implants. The patient had a large maxillary defect, and no other treatment modalities such as conventional prosthetic appliances and traditional dental implant insertions were applicable. The patient had a very poor quality of life and as a rehabilitation option, two zygomatic implant insertions were planned and performed as an anchorage for maxillary fixed prosthesis. Radiographic and clinical examination after three years of follow-up indicated that healing was achieved, and healthy tissues formed around zygomatic implants. The patient did not suffer from any additional necrotic tissues or other complications in the oral cavity. According to the results of this case report, zygomatic implantation after resective surgery might be considered as a promising alternative for MRONJ patients with large defects when other treatment alternatives fail or are not applicable.

Uncovering the unique characteristics of the mandible to improve clinical approaches to mandibular regeneration

The mandible (lower jaw) bone is aesthetically responsible for shaping the lower face, physiologically in charge of the masticatory movements, and phonetically accountable for the articulation of different phonemes. Thus, pathologies that result in great damage to the mandible severely impact the lives of patients. Mandibular reconstruction techniques are mainly based on the use of flaps, most notably free vascularized fibula flaps. However, the mandible is a craniofacial bone with unique characteristics. Its morphogenesis, morphology, physiology, biomechanics, genetic profile, and osteoimmune environment are different from any other non-craniofacial bone. This fact is especially important to consider during mandibular reconstruction, as all these differences result in unique clinical traits of the mandible that can impact the results of jaw reconstructions. Furthermore, overall changes in the mandible and the flap post-reconstruction may be dissimilar, and the replacement process of the bone graft tissue during healing can take years, which in some cases can result in postsurgical complications. Therefore, the present review highlights the uniqueness of the jaw and how this factor can influence the outcome of its reconstruction while using an exemplary clinical case of pseudoarthrosis in a free vascularized fibula flap.

MRONJ of the Mandible—From Decortication to a Complex Jaw Reconstruction Using a CAD/CAM-Guided Bilateral Scapula Flap

Medication-related osteonecrosis of the jaw (MRONJ) has been an integral part of the maxillofacial patient population for some time. The therapeutic concept ranges from conservative approaches over less extended decortications to major jaw resections, which can result in a considerable loss of quality of life. Based on three case reports, this paper presents the long-term history of patients with MRONJ of the mandible, whose disease ultimately resulted in partial or total mandibular resection and subsequent multisegmental reconstruction using a microvascular anastomosed bone flap. Furthermore, a suitable alternative for complex mandibular reconstruction is demonstrated when using a free fibula flap is not possible. The options are limited, particularly when multisegmental restoration of mandibular continuity is required. One case presents a mandible reconstruction using a CAD/CAM-guided bilateral scapular free flap (CAD/CAM = Computer-Aided Design and Manufacturing), which has not been described for this purpose before. Due to the complexity, computer-assisted surgery and patient-specific implants seem reasonable, which is why a special focus was applied to this topic.

High doses of zoledronic acid induce differential effects on femur and jawbone microstructure

OBJECTIVES

The aim of this study is to investigate the long-term effects on jaw and femur bone induced by oncologic doses of zoledronic acid in a young rat model.

MATERIAL AND METHODS

Six 12-week-old male Wistar rats received zoledronic acid (0.6 mg/kg) and six control rats received saline solution in the same volume. Compounds were administered intraperitoneally in five doses every 28 days. Euthanasia was performed 150 days after therapy onset. After animal sacrifice, their mandibles and femurs were scanned ex vivo using a high-resolution (14 μm) micro-computed tomography. Morphometric bone parameters were calculated using CT-Analyzer (Bruker, Belgium) between the first and second mandibular molars and in the distal femur metaphysis and epiphysis.

RESULTS

The treatment group as compared to the controls showed a significantly (p < .05) increased bone quantity (↑BV/TV, ↓Po[Tot], ↑Tb.Th), bone density (↑TMD, ↑BMD), and osteosclerosis of the trabecular bone (↓Tb.Sp, ↓Conn.Dn, ↓Tb.Pf, ↓SMI) in all anatomical sites. Bone remodeling suppression due to zoledronic acid treatment was more pronounced (p < .05) in the femoral metaphysis relative to the mandible and epiphysis. The exploratory linear discriminant analysis showed that for the mandible, it was mainly the bone quantity-related morphometric indices (BV/TV and Tb.Th), while for the femoral epiphysis and metaphysis, it was bone structure-related (Tb.Pf and Tb.N), which are of primary importance to study the treatment effect.

CONCLUSION

High doses of bisphosphonates can differently affect the bone quantity, density, and structure in long bones and jawbones. In the metaphysis, bone changes were primarily concentrated in the region of the growth plate. Future studies may consider the use of bone morphometric indices to evaluate the effect of bisphosphonates.

Characterization of Mesenchymal Stem Cells Derived from Bisphosphonate-Related Osteonecrosis of the Jaw Patients' Gingiva

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a clinical condition that specifically occurs in the oral cavity, characterized by retarded wound healing in oral mucosa accelerating the exposure of bone. Moreover, the pathological mechanism remains poorly understood. Gingival mesenchymal stem cells (GMSCs) play a critical role in gingival healing and soft tissue regeneration. Although previous studies have showed that bisphosphonates (BPs) are highly toxic to healthy GMSC, there is overall lack of direct evidence demonstrating the characterization of GMSCs derived from BRONJ patients. In present study, we isolated GMSCs for the first time from the central area of BRONJ patients' gingiva (center-BRONJ GMSCs) and the peripheral area (peri-BRONJ GMSCs), and found that they exhibited decreased proliferation, adhesion, migration capacities and underwent early apoptosis in vitro compared control GMSCs. Notably, the central and peripheral BRONJ GMSCs transplantation in a mice excisional skin model also displayed lower cell survival rate and poor healing effects than that of controls. Mechanistically, TGF-β1 signaling pathway was suppressed not only in BRONJ patients' gingival lesions but also in BRONJ GMSCs transplantation animal model. The results above suggested that under the microenvironment of BRONJ patients, the dysfunction of GMSCs and the suppressed TGF-β1 signaling pathway may be the vital factors in impaired gingival healing, thus contributing to persistent exposure of underlying bone and development of BRONJ. This study provides new insights into the prevention for BRONJ by improving the functions of GMSCs and upregulating TGF-β1 in accelerating gingival wound healing. Schematic illustration of the dysfunction of BRONJ GMSCs in vitro and BRONJ GMSCs transplantation in a mice skin model delaying cutaneous wound healing mainly via suppressing TGF-β1 signaling pathway.

Plasma Membrane Receptors Involved in the Binding and Response of Osteoclasts to Noncellular Components of the Bone

Osteoclasts differentiate from hematopoietic cells and resorb the bone in response to various signals, some of which are received directly from noncellular elements of the bone. In vitro, adherence to the bone triggers the reduction of cell–cell fusion events between osteoclasts and the activation of osteoclasts to form unusual dynamic cytoskeletal and membrane structures that are required for degrading the bone. Integrins on the surface of osteoclasts are known to receive regulatory signals from the bone matrix. Regulation of the availability of these signals is accomplished by enzymatic alterations of the bone matrix by protease activity and phosphorylation/dephosphorylation events. Other membrane receptors are present in osteoclasts and may interact with as yet unidentified signals in the bone. Bone mineral has been shown to have regulatory effects on osteoclasts, and osteoclast activity is also directly modulated by mechanical stress. As understanding of how osteoclasts and other bone cells interact with the bone has emerged, increasingly sophisticated efforts have been made to create bone biomimetics that reproduce both the structural properties of the bone and the bone’s ability to regulate osteoclasts and other bone cells. A more complete understanding of the interactions between osteoclasts and the bone may lead to new strategies for the treatment of bone diseases and the production of bone biomimetics to repair defects.

Bilateral femoral head osteonecrosis in a patient with metastatic breast cancer receiving long-term zoledronic acid treatment: A case report

Bone-modifying agents (BMAs), including bisphosphonate and anti-receptor activator of NF-κB ligand (RANKL) antibodies, are effective in treating bone metastases. The present study is a case report on the efficacy and side effects of long-term treatment with zoledronic acid, a BMA, in a 57-year-old woman. The patient was diagnosed with concurrent stage IV triple-negative breast cancer and stage II colon cancer. The patient experienced complete remission of both these cancers following chemotherapy, zoledronic acid treatment and irradiation for breast cancer and surgery for colon cancer. The patient received long-term zoledronic acid treatment and has survived >7 years after her initial diagnosis. The patient subsequently reported bilateral hip pain that was diagnosed as osteonecrosis of the femoral head, after the presence of bone metastases was ruled out using magnetic resonance imaging. The patient underwent bilateral artificial hip joint replacements. After orthopedic surgery, the multiple distant metastases, including a brain metastasis, remained in complete remission. It is well established that BMAs, such as zoledronic acid, increase the risk of osteonecrosis of the jaw, but it is not well understood if they can increase this risk in other anatomical locations. The findings of the present case study suggested that while long-term use of BMAs may be effective in managing bone metastases, it may increase the risk of osteonecrosis in anatomical locations other than the jaw.

Effect of bisphosphonates on healing of tooth extraction wounds in infectious osteomyelitis of the jaw

OBJECTIVES

Antiresorptive agent-related osteonecrosis of the jaw (ARONJ) and infectious osteomyelitis of the jaw (OMJ) in antiresorptive-naïve patients are different disease entities. Although osteoclast inhibition is at the center of the pathogenesis of ARONJ, the role of osteoclast inhibition in infectious OMJ is unknown. The objective of this study was to determine the effect of bisphosphonate osteoclast inhibition in infectious OMJ.

METHODS

Osteomyelitis was induced in mice by S. aureus inoculation. The establishment of OMJ was verified by the culture of bone marrow samples obtained from the mandible. Infected animals received either zoledronic acid (ZA) or saline starting at week-2. Treated animals along with non-infected animals underwent tooth extractions at week-4 post-infection. Healing was assessed every week using in vivo micro-computed tomography and intraoral photos. Animals were euthanized at week-8 and cervical lymph nodes were assessed for lymphatic and blood vessels.

RESULTS

Tooth extraction wounds did not heal in animals with OMJ. These wounds were characterized by incomplete soft tissue coverage, sporadic bone fill in the sockets, and inflammatory cell accumulation in the connective tissue at 4 weeks after tooth extractions. Conversely, the majority of tooth extraction wounds in the infected animals treated with ZA had improved healing with better bone fill than even non-infected control animals. Consistently, atrophic lymphatic vessels were noted in the draining lymph nodes in animals with OMJ. However, infected animals treated with ZA had lymphatic vessels that were unaltered and showed a similar appearance to those in non-infected control animals.

CONCLUSION

ZA treatment promoted wound healing in the jaw with infectious osteomyelitis. Clearly, antiresorptive therapy is contraindicated in patients with ARONJ. However, our finding suggests that osteoclast inhibition is potentially an effectual remedy for infectious OMJ in antiresorptive-naïve patients.

The Type of Antiresorptive Treatment Influences the Time to Onset and the Surgical Outcome of Medication-Related Osteonecrosis of the Jaw

PURPOSE

Few data exist focusing on differences in the time to disease onset and the success rates in patients suffering from medication-related osteonecrosis of the jaw (MRONJ) dependent on their different antiresorptive treatment. The purpose of this study was to analyze and compare these variables for patients treated with bisphosphonate (BP) or denosumab (DNO) and for patients who switched the antiresorptive drug (BP/DNO).

PATIENTS AND METHODSS

A retrospective single-center cohort study with patients suffering from MRONJ was conducted. The predictor variable was the antiresorptive treatment, the outcome variables were 1) time to onset of MRONJ (time of antiresorptive treatment to MRONJ diagnosis) and 2) treatment success (mucosal integrity 12 months postoperatively). The other variables include data on demographic, underlying disease, MRONJ stage, and trigger events. Cox and logistic regression, Phi-coefficient, Cramer's V, and Kruskal-Wallis tests were applied.

RESULTS

One hundred thirty-two patients were included and divided into 3 groups: group I (BP) n = 45 patients, n = 59 lesions; group II (BP/DNO) n = 42 patients, n = 71 lesions; and group III (DNO) n = 45 patients, n = 62 MRONJ lesions. Treatment success and time to onset differed significantly between the groups: success rates in group I BP (84.7%) were significantly lower (P = .04) than in group II BP/DNO (91.5%, P = .12) and group III DNO (90.3%, P = .35). The onset was significantly earlier in group III DNO (median 2.0 years, Q_0.25: 1.49, Q_0.75: 2.98; confidence interval 95%: 1.93 to 2.83) than in group II BP/DNO (median 4.07 years, Q_0.25: 1.64, Q_0.75: 6.70; confidence interval 95%: 3.55 to 5.68) and group I BP (median 3.86 years, Q_0.25: 1.69, Q_0.75: 6.46; confidence interval 95%: 3.43 to 5.87).

CONCLUSIONS

The different antiresorptive drugs show distinctive characteristics of time to onset and treatment success with the lowest success rates in the BP group and the earliest onset in the DNO group. The switch of the antiresorptive therapy (BP to DNO) did not influence the outcome variables negatively.

Quantitative bone single photon emission computed tomography analysis of the effects of duration of bisphosphonate administration on the parietal bone

Effects of long-term bisphosphonate (BP) administration on the metabolism of healthy bone and the concomitant changes in imaging are unclear. Hence, we aimed to retrospectively investigate the effects of long-term BP administration on the intact parietal bone using the standardised uptake value (SUV) derived from single photon emission computed tomography (SPECT). We enrolled 29 patients who had odontogenic infection, osteoporosis, bone metastasis cancer, or rheumatoid arthritis, and classified them into BP-naïve: A (14 patients) and BP-treated: B, < 4 years (7 patients) and C, ≥ 4 years (8 patients) groups. We measured the maximum bilateral SUV (SUVmax) of the parietal bone using quantitative bone SPECT software. There were significant differences in the duration of BP administration and SUVmax of the parietal bone among the diseases (P < 0.0001 and P = 0.0086, respectively). There was a positive correlation between the duration of BP administration and SUVmax of the parietal bone (r_s = 0.65, P = 0.0002). The SUVmax was significantly different between A and B (P = 0.02) and between A and C (P = 0.0024) groups. This is the first report on the correlation between long-term BP administration and the SUVmax of the parietal bone using the quantitative bone SPECT analysis.

Necrotizing periodontitis or medication-related osteonecrosis of the jaw (MRONJ) in a patient receiving Bemcentinib-a case report

Bemcentinib is a newly developed AXL inhibitor that is currently under investigation in phase II trails for the treatment of acute myeloblastic leukemia (AML). Clinical and radiographic findings in this case were very similar to cases of MRONJ in patients receiving Sunitinib or other anti-angiogenetic substances, assuming that Bemcentinib may cause similar oral side effects. We present a male 81-year-old patient with a manifestation of alveolar bone necrosis at the central upper incisors following a 2-month regimen with the AXL-inhibitor Bemcentinib, administered for the treatment of secondary acute myeloblastic leukemia (sAML). Due to the duration of less than 8 weeks, the osteonecrosis was diagnosed as necrotizing periodontitis, but the intraoral clinical and radiographic findings were also compatible with the differential diagnosis of medication-related osteonecrosis of the jaw (MRONJ, stage II). Following to discontinuation of Bemcentinib, the affected bone was surgically revised including the removal of a demarcated bone sequester under preventive antibiotic treatment (metronidazole 400 mg t.i.d.). We hypothesize that Bemcentinib might increase the susceptibility for osteonecrosis of the jaw, probably related to its antiangiogenic effects and the resulting modulation of host immune response. Based on the current observations, it can be assumed that oro-dental health might be significant also prior and during treatment with Bemcentinib for the prevention of MRONJ.

Enhancement of peri-implant bone formation via parathyroid hormone administration in a rat model at risk for medication-related osteonecrosis of the jaw

Purpose

Dental implant-associated medication-related osteonecrosis of the jaw has been frequently reported in patients administered bisphosphonates (BPs) to prevent osteoporosis. The aim of this study was to investigate the effect of intermittent administration of parathyroid hormone (PTH) on peri-implant bone in the maxillae of ovariectomized rats systemically administered BPs.

Methods

Thirty 8-week-old female Sprague-Dawley rats were randomly divided into 3 groups. The OVX-ZP group included ovariectomized rats administered 60 µg/kg of zoledronate once a week for 6 weeks and 30 µg/kg PTH after implant installation. The OVX-Z group included ovariectomized rats administered 60 µg/kg of zoledronate once a week for 6 weeks and saline after implant installation, and the control group included rats that underwent a sham operation and were then administered saline. Rats were sacrificed 4 weeks after implant placement for histomorphometric and micro-computed tomography (CT) analyses.

Results

The average bone area percentage was greater in the OVX-ZP group than in the OVX-Z group (53.4%±4.0% vs. 28.9%±9.5%, P=0.01). The bone-to-implant contact ratio was 50.8%±1.4% in the OVX-ZP group and 16.9%±2.4% in the OVX-Z group (P=0.012). The average bone volume ratio as shown on micro-CT was 31.3%±19.8% in the OVX-ZP group and 19.4%±9.3% in the OVX-Z group (P=0.045). The OVX-ZP and OVX-Z groups displayed similar trabecular thickness (0.06±0.004 mm vs. 0.06±0.002 mm) (P>0.05) and trabecular separation (0.21±0.02 mm vs. 0.29±0.13 mm) (P>0.05). However, the number of trabeculae in the OVX-ZP group was significantly higher than that in the OVX-Z group (4.3±1.33/mm³ vs. 2.2±0.19/mm³) (P=0.024).

Conclusions

The present findings indicate that intermittently-administered PTH can promote peri-implant bone formation and suggest that PTH administration may aid in effective treatment for medication-related osteonecrosis of the jaw after dental implantation.

Cloud-Based Multicenter Data Collection and Epidemiologic Analysis of Bisphosphonate-Related Osteonecrosis of the Jaws in a Central European Population

Objective: Bisphosphonate-related osteonecrosis of the jaws is considered to be a rare but severe complication of bisphosphonate therapy. To understand this condition better, data collection is essential. Although the number of scientific papers about this subject is large, to date only a few multicenter reports have been published. Study design: We present a novel cloud-based data collection system for the evaluation of the risk factors of bisphosphonate-related osteonecrosis of the jaws. Web-based questionnaire and database have been set up and made available to voluntary researchers and clinicians in oral and maxillofacial surgery in Hungary and Slovakia. Results: To date, fifteen colleagues from eight maxillofacial units have joined the study. Data of 180 patients have been recorded. Collected data were statistically analysed and evaluated from an epidemiological point of view. Conclusions: Authors consider cloud-based multicenter data collection a useful tool that allows for real-time collaboration between users, facilitates fast data entry and analysis, and thus considerably contributes to widening our knowledge of bisphosphonate-related osteonecrosis of the jaws.

Cloud-Based Multicenter Data Collection and Epidemiologic Analysis of Bisphosphonate-Related Osteonecrosis of the Jaws in a Central European Population

Objective: Bisphosphonate-related osteonecrosis of the jaws is considered to be a rare but severe complication of bisphosphonate therapy. To understand this condition better, data collection is essential. Although the number of scientific papers about this subject is large, to date only a few multicenter reports have been published. Study design: We present a novel cloud-based data collection system for the evaluation of the risk factors of bisphosphonate-related osteonecrosis of the jaws. Web-based questionnaire and database have been set up and made available to voluntary researchers and clinicians in oral and maxillofacial surgery in Hungary and Slovakia. Results: To date, fifteen colleagues from eight maxillofacial units have joined the study. Data of 180 patients have been recorded. Collected data were statistically analysed and evaluated from an epidemiological point of view. Conclusions: Authors consider cloud-based multicenter data collection a useful tool that allows for real-time collaboration between users, facilitates fast data entry and analysis, and thus considerably contributes to widening our knowledge of bisphosphonate-related osteonecrosis of the jaws.

Skeletal Site-Specific Response of Jawbones and Long Bones to Surgical Interventions in Rats Treated with Zoledronic Acid

Bisphosphonates (BPs) have been extensively used for management of bone diseases with pathologically high resorption. Despite the great clinical benefits, a severe complication known as medication-related osteonecrosis of the jaw (MRONJ) has been reported. It is found that most of the reported MRONJ cases were limited in the jawbones/craniofacial bones instead of long bones. The present study aims to investigate the differential bone response to surgical procedures between jawbones and long bones exposed to BPs. Forty-eight skeletal mature Sprague Dawley female rats were administered oncologic dose of zoledronic acid (ZA) or normal saline for 4 weeks and then subjected to tooth extraction on the mandible and maxilla, and a bone defect creation on the femur. After surgical procedures, ZA or saline treatment were continued until sacrifice at week 2, week 4, and week 8, post-operatively. The samples were subjected to micro-computerized tomography (micro-CT) and histological assessment. Osteonecrosis was only found in jawbones in ZA-treated rats. ZA-treated rats showed significantly higher bone mineral density with greater bone volume in all surgical sites than that in the controls. The length of exposure of ZA did not seem to affect trabecular microstructure, and it only showed higher bone volume and BMD with longer healing time which is expected in the healing process.

Effect of intravenous administration of zoledronic acid on jaw bone density in cases having skeletal metastasis: A prospective clinical study

Aim:

The objective is to evaluate the effect of intravenous (i.v.) administration of bisphosphonate (zoledronic acid) therapy on the jaw bone density and incidence of any other bony patholog.

Settings and Design:

Observational – prospective study.

Materials and Methods:

A total of 57 patients having a history of bony metastasis (excluding the jaw bone) were enrolled following the inclusion/exclusion criteria. Each patient received six doses of 4 mg i.v. bisphosphonate once a month. Multidetector computed tomography (MDCT) of jawbones for each patient was performed before the start of therapy (baseline) and subsequently at 6 and 12 months. Bone density was assessed at 24 predetermined sites (8 sites in maxilla and 16 sites in mandible) and any pathological change in either of the jaw bones was noted.

Statistical Analysis Used:

Shapiro–Wilk test ,Pearson's Chisquare test and repeated measures analysis of variance.

Results:

The result showed no statistically significant increase in mean bone density over a period of 1 year in maxilla and mandible. However, a significant increase in bone density was observed from 6 months to 1 year in mandibular anterior cancellous bone. The detailed observation of each MDCT scan showed no pathological change in either of the jaw bones during the study period.

Conclusion:

The administration (i.v.) of six doses of 4 mg bisphosphonate did not lead to a significant change in bone density over a period of 1 year.

Symposium: Imaging modalities for drug-related osteonecrosis of the jaw (6), assessment of mandibular metabolism due to long-term administration of an anti-resorptive agent by bone scintigraphy (secondary publication)

It is not yet known why anti-resorptive agent-related osteonecrosis specifically affects the jaw. Here we assessed changes in the bone metabolism of the mandible in response to long-term bisphosphonate (BP) therapy, and we compared the bone metabolism changes of the mandible with those of other bone sites using a quantitative analysis by bone scintigraphy. The region of interest was selected by identifying without an abnormal accumulation of the mandible, humerus, second and fourth lumbar vertebrae, iliac crest, intertrochanteric femur and diaphysis. Bone scintigraphy images were quantified using a value we termed the ‘bone uptake value (BUV)’. In the low-dose bisphosphonate (LBP) group (n = 21), the patients were undergoing osteoporosis treatment with low-dose BP. The high-dose BP (HBP) group consisted of 12 bone metastasis patients undergoing high-dose BP treatment. The Control group was 47 subjects with oral disease who had never been treated with an anti-resorptive agent. Our analyses demonstrated that with long-term BP administration, the bone metabolism of the iliac crest and intertrochanteric femur was suppressed but that of the mandible was enhanced. There was no significant difference in bone metabolism with either the low-dose BP or high-dose BP treatment. The effects of the long-term administration of BP were site-specific.

Medication-related osteonecrosis of the jaw: Prevention, diagnosis and management in patients with cancer and bone metastases

Medication-related osteonecrosis of the jaw (MRONJ) is primarily an adverse side effect of denosumab or bisphosphonates (particularly when used at high doses to prevent skeletal-related events [SREs] in patients with cancer and bone metastases) or possibly anti-angiogenic cancer treatment. While the implementation of preventive measures over recent years has reduced the risk of MRONJ in patients with bone metastases due to cancer, it is imperative to balance the risk of MRONJ against the beneficial effects of treatment with denosumab or bisphosphonates on the skeletal health of patients. Despite growing awareness of MRONJ within the medical community, there is a lack of large-scale, prospective clinical studies in this rapidly evolving field. Discussing preventive measures with patients and implementing them, both before and during treatment with bisphosphonates or denosumab, is the best option to reduce the risk of MRONJ. In particular, avoiding bone trauma and preventing and treating dental infections before and during denosumab or bisphosphonate therapy is crucial to minimize the risk of MRONJ. If MRONJ develops, conservative (non-surgical) treatment can provide symptom relief, but achieving mucosal closure remains challenging. When management of symptoms and mucosal healing are the ultimate goals of therapy, or after failure of conservative treatment, a surgical approach may be beneficial. This critical review, based on a best-evidence review of currently available literature, provides clear practical guidelines to help to prevent, manage and treat MRONJ. Overall, a multidisciplinary, pragmatic approach to MRONJ should be adopted, prioritizing patient's quality of life and management of their skeletal malignant disease.

Comparison of mucosal and mucoperiosteal wound cover for the treatment of medication-related osteonecrosis of the jaw lesions: a retrospective cohort study

OBJECTIVES

Actually, there is no detailed guidance on how to deal with wound closure after surgical removal of medication-related osteonecrosis of the jaw (MRONJ) lesions. This study attempts to compare the difference in outcome between the mucosal and the mucoperiosteal flap closure after surgery.

PATIENTS AND METHODS

In this retrospective monocentric cohort study, patients (n = 61; 35 female/26 male) suffering from MRONJ and requiring surgical therapy at the University of Aachen between 2013 and 2015 were included. Due to intra-institutional variances, one group was treated with the mucosal, the other group with the mucoperiosteal technique. The success rate, i.e., mucosal closure and no relapse at the point of follow-up, was evaluated and compared. All patients were clinically investigated for the postoperative follow-up during a special consultation appointment.

RESULTS

The success rates between the different techniques after 2 years follow-up were very similar. In the group of mucosal wound closure, 22 of 29 (75.86%) patients revealed mucosal integrity without signs of MRONJ. The rate in the mucoperiosteal wound closure group was almost identical (24 of 32 (75%)).

CONCLUSION

No differences in the success rates between the two different techniques could be evaluated.

CLINICAL RELEVANCE

The results of this study suggest that the complete removal of the necrotic bone might have a higher impact on the success rates than the technique of the wound closure. Due to the fact that the mucoperiosteal wound closure technique offers a better overview of the extent of the MRONJ lesion, the authors advise to use this technique.

Further development of the MRONJ minipig large animal model

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but serious and potentially severe side effect of antiresorptive therapy with bisphosphonates or denosumab. Recently, a large animal minipig MRONJ model was introduced which led to early necrotic lesions in the majority of extraction sites after bisphosphonate administration. The aim of this project was to modify the preoperative cumulative bisphosphonate dose (zoledronate) and hereby firstly to demonstrate the reliability and reproducibility of the established model. Secondly, the MRONJ lesions should be carefully investigated using clinical and μCT as well as detailed histological analyses. Twelve 1.5-year-old Göttingen minipigs were divided into three groups. In group 1 (n = 3) minipigs received weekly doses of zoledronate intravenously (0.05 mg/kg bodyweight) for 20 weeks. No interventions were performed. In group 2 (n = 6) animals received the identical zoledronate dosage as animals in group 1 and tooth extractions of two premolars (PM 2 and 4) in each jaw (maxilla and mandible) were performed after 12 weeks. Group 3 (n = 3) served as tooth extraction only control (no zoledronate administrations). The jaw-bones were subjected to detailed macroscopic, radiological and histological investigations. All extraction sites (24/24) in animals of group 2 showed clinical, radiological and histological signs of MRONJ (mainly stage II), whereas no bone necrosis was found in group 3. Animals of group 1 and group 2 showed further MRONJ lesions in areas where infections (periodontitis) were present. This is the first large animal model to show a 100% incidence of MRONJ at all extraction sites in bisphosphonate pretreated animals (group 2). In addition, in this preclinical model for MRONJ it is shown that tooth extractions are not mandatory for a MRONJ manifestation. MRONJ also developed in areas of gingival or periodontal infections.

Wound healing protein profiles in the postoperative exudate of bisphosphonate-related osteonecrosis of mandible

Recurrent bacterial infections in cases of bisphosphonate-related osteonecrosis of jaw (BRONJ) frequently occur. Therefore, BRONJ are usually treated by radical saucerization followed by intensive antibiotic medications without bisphosphonate therapy. The postoperative exudate (POE) from BRONJ lesions may directly indicate the inflammatory status of osteomyelitis in patients, but so far, the POE has rarely been examined for its expression of various cytokines and wound healing proteins. A total of 27 cases of BRONJ, which involved the mandible, were selected and their individual POE collected 6 h, 1 day, and 2 days after surgical intervention was analyzed by immunoprecipitation high performance liquid chromatography (IP-HPLC). The different protein expressions in the BRONJ POE were compared with findings from ten cases of chronic mandibular osteomyelitis (CMO) exudate as the control group. For the protein expressions for inflammation, osteogenesis, and angiogenesis, in the 6 h POE sample, the BRONJ exudate exhibited more expression of IL-10, IL-28, OPG, and osteocalcin, but less expression of TNFα and LL-37 than the control. In the 1 day POE sample, the BRONJ exudate showed more expression of TNFα, IL-6, 8, 12, 28, α1-antitrypsin, VEGF-A, and VEGF-C, but less expression of CD68, lysozyme, bFGF, RANKL, bFGF, and ALP than the control. In the 2 day POE sample, the BRONJ exudate consistently showed more expression of LL-37, β-defensin-1, and VEGF-A than the control. The present BRONJ POE revealed the rapid progress of bony wound healing through increased molecular signaling for inflammation, angiogenesis, and osteogenesis compared to the control. Therefore, it was suggested that the POE obtained from the postoperative bony lesions should be collected and analyzed by the IP-HPLC method to predict the prognosis of seriously complicated inflammatory bony diseases such as BRONJ.

[Position paper on medication-related osteonecrosis of the jaw (MRONJ)]

It is now 12 years since the first article on medication-related osteonecrosis of the jaw (MRONJ) was reported in 2003. The recognition of MRONJ is still inconsistent between physicians and dentists but it is without doubt a severe disease with impairment of oral health-related quality of life. This position paper was developed by three Austrian societies for dentists, oral surgeons and osteologists involved in this topic. This update contains amendments on the incidence, pathophysiology, diagnosis, staging and treatment and provides recommendations for management based on a multidisciplinary international consensus. The MRONJ can be a medication-related side effect of treatment of malignant and benign bone diseases with bisphosphonates (Bp), bevacizumab and denosumab (Dmab) as antiresorptive therapy. The incidence of MRONJ is highest in the oncology patient population (range 1-15 %), where high doses of these medications are used at frequent intervals. In the osteoporosis patient population, the incidence of MRONJ is estimated to be 0.001-0.01 %, marginally higher than the incidence in the general population (< 0.001 %). Other risk factors for MRONJ include glucocorticoid use, maxillary or mandibular bone surgery, poor oral hygiene, chronic inflammation, diabetes mellitus, ill-fitting dentures as well as other drugs, including antiangiogenic agents. Prevention strategies for MRONJ include elimination or stabilization of oral disease prior to initiation of antiresorptive agents, as well as maintenance of good oral hygiene. In those patients at high risk for the development of MRONJ, including cancer patients receiving high-dose BP or Dmab therapy, consideration should be given to withholding antiresorptive therapy following extensive oral surgery until the surgical site heals with mature mucosal coverage. Management of MRONJ is based on the stage of the disease, extent of the lesions and the presence of contributing drug therapy and comorbidity. Conservative therapy includes topical antibiotic oral rinses and systemic antibiotic therapy. Early data have suggested enhanced osseous wound healing with teriparatide in those patients without contraindications for its use. The MRONJ related to denosumab may resolve more quickly with a drug holiday than MRONJ related to bisphosphonates. Localized surgical debridement is indicated in advanced nonresponsive disease and has proven successful. More invasive surgical techniques are becoming increasingly more important. Prevention is the key for the management of MRONJ. This requires a close teamwork for the treating physician and the dentist. It is necessary that this information is disseminated to other relevant health care professionals and organizations.

Fibrous Dysplasia and Medication-Related Osteonecrosis of the Jaw

PURPOSE

Osteonecrosis of the jaw (ONJ) is an established side effect of intravenous bisphosphonates and other antiresorptive medications. Although bisphosphonates are frequently prescribed for patients with the skeletal disorder fibrous dysplasia (FD), there are no reports of ONJ in this population. This has led some to conclude that patients with FD are at low risk for the development of bisphosphonate-related ONJ.

PATIENTS AND METHODS

Patients were evaluated as part of a longstanding FD natural history study at the National Institutes of Health.

RESULTS

Of 76 patients with FD who were treated with bisphosphonates, 4 developed ONJ (5.4%). Three patients developed ONJ in areas of FD-affected bone and 1 in an area of normal bone. All 4 patients had features known to be associated with ONJ in the general population, including long-term high-dose intravenous bisphosphonate treatment, periodontal and endodontic infections, and dentoalveolar surgical procedures.

CONCLUSIONS

These cases establish ONJ as a potential complication of bisphosphonate treatment in patients with FD. The presence of established risk factors for ONJ in this group of patients with FD suggests that high-risk patients could be identified before the development of ONJ. Clinicians should use caution in prescribing bisphosphonates to patients with FD and should do so only for established indications.

Bisphosphonate uptake in areas of tooth extraction or periapical disease

PURPOSE

Bisphosphonates (BPs) are widely used for the management of bone diseases such as osteoporosis and bone malignancy. However, osteonecrosis of the jaws (ONJ) is a serious complication of BP treatment. ONJ lesions mainly occur after extraction of teeth deemed unrestorable or around teeth with active periodontal or periapical disease. Because socket healing or dental disease shows higher bone turnover, the authors hypothesized that preferentially high BP accumulation would be observed in these areas.

MATERIALS AND METHODS

The authors tested the uptake of fluorescein-labeled zoledronic acid (5-FAM-ZOL) in sites of tooth extraction or experimental periapical disease in mice. Maxillary molars were extracted or the crowns of mandibular molars were drilled to induce pulp exposure. Animals were injected with 5-FAM-ZOL 200 μg/kg at various times after intervention and fluorescence was measured at healthy versus intervention sites. Fluorescein injections were used as controls. Data were analyzed by t test and mixed effects linear models were constructed because the animals had repeated measurements over time and at the 2 sites.

RESULTS

A statistically significant (P≤.001 to .002) time-dependent uptake of 5-FAM-ZOL was detected in the areas of extraction socket and in the alveolar ridge around teeth with periapical disease compared with the healthy contralateral sites of the same animals. For the 2 conditions, the uptake reached a maximum 3 days after experimental intervention and decreased thereafter.

CONCLUSIONS

These data suggest that sites with increased bone turnover, such as extraction sites or areas of periapical inflammation, are exposed to higher BP doses than the remaining alveolar ridge and could explain, at least in part, the susceptibility of such areas to ONJ.