Importance of microcracks in etiology of bisphosphonate-related osteonecrosis of the jaw: a possible pathogenetic model of symptomatic and non-symptomatic osteonecrosis of the jaw based on scanning electron microscopy findings

Local E-rhBMP-2/β-TCP Application Rescues Osteocyte Dendritic Integrity and Reduces Microstructural Damage in Alveolar Bone Post-Extraction in MRONJ-like Mouse Model

The pathology of medication-related osteonecrosis of the jaw (MRONJ), often associated with antiresorptive therapy, is still not fully understood. Osteocyte networks are known to play a critical role in maintaining bone homeostasis and repair, but the exact condition of these networks in MRONJ is unknown. On the other hand, the local application of E-coli-derived Recombinant Human Bone Morphogenetic Protein 2/β-Tricalcium phosphate (E-rhBMP-2/β-TCP) has been shown to promote bone regeneration and mitigate osteonecrosis in MRONJ-like mouse models, indicating its potential therapeutic application for the treatment of MRONJ. However, the detailed effect of BMP-2 treatment on restoring bone integrity, including its osteocyte network, in an MRONJ condition remains unclear. Therefore, in the present study, by applying a scanning electron microscope (SEM) analysis and a 3D osteocyte network reconstruction workflow on the alveolar bone surrounding the tooth extraction socket of an MRONJ-like mouse model, we examined the effectiveness of BMP-2/β-TCP therapy on the alleviation of MRONJ-related bone necrosis with a particular focus on the osteocyte network and alveolar bone microstructure (microcrack accumulation). The 3D osteocyte dendritic analysis showed a significant decrease in osteocyte dendritic parameters along with a delay in bone remodeling in the MRONJ group compared to the healthy counterpart. The SEM analysis also revealed a notable increase in the number of microcracks in the alveolar bone surface in the MRONJ group compared to the healthy group. In contrast, all of those parameters were restored in the E-rhBMP-2/β-TCP-treated group to levels that were almost similar to those in the healthy group. In summary, our study reveals that MRONJ induces osteocyte network degradation and microcrack accumulation, while application of E-rhBMP-2/β-TCP can restore a compromised osteocyte network and abrogate microcrack accumulation in MRONJ.

Biomechanical analysis of alveolar bones with compromised quality supporting a 4-unit implant bridge; a possible association with implant-related sequestration (IRS)

OBJECTIVES

This study aimed to investigate the strain in the bone surrounding dental implants supporting a 4-unit bridge and assess the role of excessive strain as a possible risk factor for implant related sequestration (IRS) or peri-implant medication-related osteonecrosis of the jaw (PI-MRONJ).

MATERIALS AND METHODS

A 3D-mandibular model was constructed using computed tomography and segmented it into cortical and cancellous bones. The 4-unit implant-supported bridges replacing the mandibular posteriors were constructed, and each featuring two, three, and four implants, respectively. The Young's modulus was assigned based on the quality of the bone. A maximum occlusal force of 200 N was applied to each implant in the axial and in a 30-degree oblique direction.

RESULTS

The maximum principal strain of the fatigue failure range (> 3000 µε) in the bone was analyzed. The volume fraction of fatigue failure was higher in poor-quality bone compared to normal bone and oblique load than in axial load. An increasing number of implants may dissipate excessive strain in poor-quality bones.

CONCLUSIONS

Occlusal force applied to poor-quality bone can result in microdamage. Given that unrepaired microdamage may initiate medication-related osteonecrosis of the jaw, long-term occlusal force on fragile bones might be a risk factor.

CLINICAL RELEVANCE

When planning implant treatment for patients with compromised bone status, clinical modifications such as strategic placement of implants and optimization of restoration morphology should be considered to reduce excessive strain which might be associated with IRS or PI-MRONJ.

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.

Peri-implantitis increases the risk of medication-related osteonecrosis of the jaws associated with osseointegrated implants in rats treated with zoledronate

This study evaluated the peri-implant tissues under normal conditions and under the influence of experimental peri-implantitis (EPI) in osseointegrated implants installed in the maxillae of rats treated with oncologic dosage of zoledronate. Twenty-eight senescent female rats underwent the extraction of the upper incisor and placement of a titanium dental implant (DI). After eight weeks was installated a transmucosal healing screw on DI. After nine weeks, the following groups were formed: VEH, ZOL, VEH-EPI and ZOL-EPI. From the 9th until the 19th, VEH and VEH-EPI groups received vehicle and ZOL and ZOL-EPI groups received zoledronate. At the 14th week, a cotton ligature was installed around the DI in VEH-EPI and ZOL-EPI groups to induce the EPI. At the 19th week, euthanasia was performed, and the maxillae were processed so that at the implanted sites were analyzed: histological aspects and the percentage of total bone tissue (PTBT) and non-vital bone tissue (PNVBT), along with TNFα, IL-1β, VEGF, OCN and TRAP immunolabeling. ZOL group presented mild persistent peri-implant inflammation, higher PNVBT and TNFα and IL-1β immunolabeling, but lower for VEGF, OCN and TRAP in comparison with VEH group. ZOL-EPI group exhibited exuberant peri-implant inflammation, higher PNVBT and TNFα and IL-1β immunolabeling when compared with ZOL and VEH-EPI groups. Zoledronate disrupted peri-implant environment, causing mild persistent inflammation and increasing the quantity of non-vital bone tissue. Besides, associated with the EPI there were an exacerbated inflammation and even greater increase in the quantity of non-vital bone around the DI, which makes this condition a risk factor for medication-related osteonecrosis of the jaws.

Novel Histopathological Findings of Micro Bone Fragments and Epithelial Response in the Oral Mucosa in Bisphosphonate-Related Osteonecrosis of the Jaw

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) occurs in the jawbone and interfacing oral mucosa of patients treated with bisphosphonates. Herein, we report novel histopathological findings in the oral mucosa of a surgical specimen obtained from a 61-year-old man with BRONJ. The resected jawbone and adjacent oral mucosa were separated for histological examination. The mucosal tissue was examined using Von Kossa staining and immunohistochemical (CK5/6, p63) staining of non-decalcified paraffin sections. Pseudoepitheliomatous hyperplasia (PEH), a microscopic feature of the mucosal epithelium in BRONJ, was observed in soft tissue specimens, concomitant with inflammatory cell infiltration. Von Kossa staining revealed small fragments of necrotic bone, tens to hundreds of micrometers in size, scattered within the connective tissues; the PEH forefront contacted some of the bone fragments. Immunohistochemical staining demonstrated that occasionally, the PEH not only contacted but also encompassed the bone fragments. To our knowledge, this is the first report of presence of micro bone fragments and their association with PEH in the oral mucosa in BRONJ.

Dose-dependent effects of zoledronic acid on the osteogenic differentiation of human bone marrow stem cells (hBMSCs)

Recent studies have shown that bisphosphonates can also impact osteoblasts besides osteoclasts. This study aimed to evaluate the effects of different concentrations of Zoledronic acid (ZA) during the osteogenic differentiation of human Bone Marrow Stem Cells (hBMSCs) in vitro. Thus, osteogenic differentiation of hBMSCs was conducted with different concentrations of Zoledronic Acid (ZA) (0, 0.1, 1.0, and 5.0 μM) for the first 3 days. Cell metabolism was quantified at 1-, 3-, 7-, and 14 days. At 7- and 14-days, the following analyses were performed: 1) mineralization nodule assay, 2) LIVE/DEAD™, 3) cell adhesion and spreading, 4) alkaline phosphatase (ALP) activity, and 5) qPCR analysis for RUNX-2), ALPL, and COL1 A1. Data were analyzed by ANOVA 2-way, followed by Tukey's post hoc test (p < 0.05). Cell metabolism (3-, 7-, and 14-days) (p < 0.001), mineralization (7-, 14-days) (p < 0.001), and ALP activity (14-days) (p < 0.001) were reduced in ZA 5.0 µM when compared to control (no ZA). Also, ZA 5.0 µM downregulated the expression of RUNX2 at 7- and 14-days (p < 0.001). It is possible to conclude that ZA (5.0 µM) can impair hBMSC differentiation into osteoblasts and interferes with its mineralization phase.

Electron microscopic analysis of necrotic bone and failed implant surface in a patient with medication-related osteonecrosis of the jaw

BACKGROUND

Bisphosphonates (BP), a commonly used medication for various bone diseases, have been known to have severe complications such as bisphosphonate-related osteonecrosis of the jaw (BRONJ). Failure of dental implants has also been found in patients with medication-related osteonecrosis of the jaw (MRONJ). In this study, we analyzed the necrotic bone tissues and the surface of the failed implants removed from the jaw in patients treated with BPs and antiresorptive agents.

RESULTS

Chronic inflammatory cells with collagen and fibrous tissues and bone sequestrum were shown at 5.0 × , 10.0 × , 20.0 × , and 40.0 × magnified histologic sections in the bone and fibrotic scar tissues removed from patients with MRONJ due to osteonecrosis. Hardened bone tissues with microcracked bony resorbed lacunae were observed in SEM. Unlike the previously published comparative data where immune cells, such as dendritic cells, were found in the failed implant surface, these immune cells were not identified in the BRONJ-related peri-implantitis tissues through the TEM investigations. Furthermore, EDS revealed that in addition to the main titanium element, gold, carbon, oxygen, calcium, phosphorus, silicon, and sulfur elements were found.

CONCLUSION

Hardened bone tissues with microcracked bony resorbed lacunae were observed in the SEM findings, which were considered as the main characteristic of the osteonecrosis of the jaw. Immune cells, such as dendritic cells were not identified in the TEM. EDS showed that in addition to the main titanium element, gold, carbon, oxygen, calcium, phosphorus, and silicon elements were found. Furthermore, it was revealed that sulfur was found, which was considered to be one of the complicated causes of implant failure in patients with BRONJ.

Correlations between Immune Response and Etiopathogenic Factors of Medication-Related Osteonecrosis of the Jaw in Cancer Patients Treated with Zoledronic Acid

Impairment of the immune response in MRONJ (medication-related osteonecrosis of the jaws) is one of the still unclear etiopathogenic mechanisms of this condition encountered in cancer patients treated with bisphosphonates, with negative effects on the patient's quality of life. The aim of the present study was to correlate the immune response with etiopathogenic factors via immunohistochemical evaluation of the maxillary tissues in zoledronic acid osteonecrosis. The retrospective study included a group of 51 patients with various types of cancers, diagnosed with stage 2 or 3 MRONJ at zoledronic acid and treated surgically. Immunohistochemical expressions of αSMA, CD3, CD4, CD8, CD20, CD79α, CD68, CD204, and tryptase were evaluated. Immunohistochemical markers expressions were statistically analyzed according to the duration of the treatment, the trigger factor, the location of the MRONJ, and the healing status. Analysis of the immune response included T lymphocytes, B lymphocytes, plasma cells, macrophages, and mast cells. The duration of treatment significantly influenced the immunohistochemical expression of most markers (p < 0.05). For an increasing trend in treatment duration, a decreasing trend in marker score was observed, suggesting an inverse correlation. The expression of the markers was different depending on the trigger factor, on MRONJ localization (maxilla/mandible), and the healing status, being more intense in patients cured per primam compared to those who had relapses. The patient's immune response was negatively influenced by the duration of the treatment, the trigger factor, the location of the lesion in the mandible, and the recurrence of MRONJ.

MicroRNA in medication related osteonecrosis of the jaw: a review

Medication related osteonecrosis of the jaw (MRONJ) is a condition caused by inhibition of the osteoclast activity by the anti-resorptive and anti-angiogenic drugs. Clinically, there is an exposure of the necrotic bone or a fistula which fails to heal for more than 8 weeks. The adjacent soft tissue is inflamed and pus may be present as a result of the secondary infection. To date, there is no consistent biomarker that could aid in the diagnosis of the disease. The aim of this review was to explore the literature on the microRNAs (miRNAs) related to medication related osteonecrosis of the jaw, and to describe the role of each miRNA as a biomarker for diagnostic purpose and others. Its role in therapeutics was also searched. It was shown that miR-21, miR-23a, and miR-145 were significantly different in a study involving multiple myeloma patients as well as in a human-animal study while miR-23a-3p and miR-23b-3p were 12- to 14-fold upregulated compared to the control group in an animal study. The role of the microRNAs in these studies were for diagnostics, predictor of progress of MRONJ and pathogenesis. Apart from its potential diagnostics role, microRNAs have been shown to be bone resorption regulator through miR-21, miR-23a and miR-145 and this could be utilized therapeutically.

Is medication related osteonecrosis of the jaw around implants a rare entity? A case series with a focus on etiopathophysiology

OBJECTIVES

Medication Related Osteonecrosis of the Jaw (MRONJ) around dental implants is a rare complication of antiresorptive drug (ARD) treatment. MRONJ has been described in patients with implants placed before, during or after ARD treatment. The aim of this study was to review our cases and to discuss a preventive approach to avoid the risk of MRONJ around implants.

MATERIALS AND METHODS

In a retrospective analysis of the 168 MRONJ seen in our department from 2005 to 2021, we searched for cases of patients with MRONJ around dental implants.

RESULTS

Six patients (4 females, 2 males) presented with MRONJ around 17 implants. Median age was 64 (50-83) years. Four patients received ARD treatment for osteoporosis and 2 for cancer. The maxilla was more affected than the mandible. Six implants were placed after the initiation of ARD treatment and eleven were placed before initiation of ARD treatments. Eight implants were managed surgically while 9 implants were managed conservatively.

CONCLUSION

In this series, implants were placed before or after starting ARD treatment. Despite initial successful osseointegration, MRONJ occurred months or years after initiation of ARD treatment. The role of periimplantitis should be discussed as well as the role of microcracks in the bone following implant loading. Less is known over the effect of ARD treatment after implant osseointegration. Implants could be a risk factor for MRONJ and must be checked regularly (every 3 months). It is important to check the healthy and biomechanical harmony of the implant system during the pre-treatment assessment.

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.

Bone Targeting Agents in Patients with Prostate Cancer: General Toxicities and Osteonecrosis of the Jaw

Introduction: Bone metastases are the most frequent site of secondary localization of prostate cancer (PCa) and are present in about 90% of cases of advanced disease. Consequently, an adequate management of bone involvement is of pivotal importance in the therapeutic approach and skeletal-related events (SREs) need to be closely monitored and promptly assessed and treated. Bone targeting agents (BTAs), consisting in bisphosphonates and denosumab, are an essential part of the treatment of metastatic prostate cancer that accompanies systemic treatments throughout the most part of the history of the disease. Activity and safety of bone targeting agents: These treatments are correlated to better outcomes in terms of reduction of SREs and, in metastatic castration resistant setting, of increased overall survival (OS), but several important adverse events have to be managed and prevented. Of these, osteonecrosis of the jaw (ONJ) is extremely invalidating and should be managed with a special attention. Discussion: The role of BTAs in prostate cancer is pivotal throughout many stages of the disease, but several toxicities should be quickly recognized and treated. We aim at recollecting evidence on clinical benefit of BTAs, common and specific toxicities, and explore the pathophysiology and clinical aspects of osteonecrosis of the jaw. We present a review of the literature to report the role of the different types of bone targeting agents in the management of prostate cancer with bone metastases with a particular focus on common toxicities and ONJ to recollect current evidences on the activity of these compounds and the correct management of their adverse events.

Medication Related Osteonecrosis of the Jaw: 2021 Position Statement of the Korean Society for Bone and Mineral Research and the Korean Association of Oral and Maxillofacial Surgeons

Antiresorptives are the most widely prescribed drugs for the treatment of osteoporosis. They are also used in malignant bone metastases, multiple myeloma, and Paget's disease, and provide therapeutic efficacy on those diseases. However, it was reported that the occurrence of osteonecrosis of the jaw (ONJ) could be related to antiresorptive exposures, and there have been many cases regarding this issue. Therefore, a clearer definition and treatment guidelines were needed for this disease. The American Society for Bone and Mineral Research and the Amnerican Association of Oral and Maxillofacial Surgeons reported statements on bisphosphonate-related ONJ (BRONJ), and a revised version was recently presented. In the revised edition, the diagnosis BRONJ was changed to medication-related ONJ (MRONJ), which reflects consideration of the fact that ONJ also occurs for denosumab, a bone resorption inhibitor of the receptor activator of the nuclear factor-κB ligand antibody family, and bevacizumab, an anti-angiogenesis inhibitor. The Korean Society for Bone and Mineral Research and the Korean Association of Oral and Maxillofacial Surgeons had collectively formed a task force for the preparation of an official statement on MRONJ based on a previous position paper in 2015. The task force reviewed current knowledge and coordinated dental and medical opinions to propose the guideline customized for the local Korean situation.

Review and Update of the Risk Factors and Prevention of Antiresorptive-Related Osteonecrosis of the Jaw

Antiresorptive-related osteonecrosis of the jaw (ARONJ) is a rare but serious adverse event of bisphosphonate or denosumab administration; it is associated with severe pain and a deteriorated quality of life. Since its first report in 2003, there have been many studies on its definition, epidemiology, pathophysiology, diagnosis, and treatment. Nevertheless, the epidemiology and mechanisms underlying this condition have not yet been fully delineated and several risk factors are known. Moreover, as there is no effective treatment currently available for osteonecrosis of the jaw, prevention is essential. Furthermore, close cooperation between prescribing physicians and dentists is important. The aim of this review was to provide up-to-date information regarding the risk factors and prevention of ARONJ from a physician's perspective.

Bevacizumab-associated implant presence-triggered osteonecrosis: A case report and literature review

The effect of bevacizumab-related osteonecrosis of the jaw on previously osseointegrated dental implants has not been adequately studied. Here, we report a case of osteonecrosis of the jaw detected around dental implants placed prior to bevacizumab therapy. A 66-year-old woman undergoing bevacizumab therapy for metastatic triple-negative breast cancer, developed malocclusion following buccal gingival swelling and pain in the #18, #19, and #20 tooth region. The patient visited a local dental clinic, where existing implants in relation to #19 and #20 were removed. Subsequently, the patient visited our department, and intraoral examination revealed necrotic bone in the region corresponding to #19 and #20. Radiographic examination showed a pathological fracture in this region that was considered to result from osteonecrosis of the jaw. Bevacizumab therapy was suspended temporarily till the acute inflammation had subsided. In addition, treatment with antibacterial agents and conservative surgery was considered. Complete soft tissue coverage was observed 14 days following surgery. In recent years, the number of patients receiving bevacizumab treatment has increased. Since bevacizumab-related osteonecrosis of the jaw could occur around previously osseointegrated dental implants as well, this case report suggests an effective treatment regimen based on a combination of antibacterial agents and conservative surgery.

Mechanism, prevention, and treatment for medication-related osteonecrosis of the jaws

The morbidity rate of medication-related osteonecrosis of the jaws (MRONJ) increased rapidly in recent years. Thusfar, the mechanism of MRONJ has no consensus. The possible mechanisms may include bone remodeling inhibition theory, angiogenesis inhibition theory, oral microorganism infection theory, immunosuppression theory, cytotoxicity-targeted oral epithelial cells, microcrack formation of maxillary or mandibular bone, and single nucleotide polymorphism. However, the efficacy of prevention and treatment based on a single mechanism is not ideal. Routine oral examination before MRONJ-related drug treatment, treatment of related dental diseases, and regular oral follow-up during drug treatment are of great significance for the prevention of MRONJ. During the treatment of MRONJ, the stage of MRONJ must be determined accurately, treatment must be standardized in accordance with the guidelines, and personalized adjustments must be made considering the specific conditions of patients. This review aimed to combine the latest research and guidelines for MRONJ and the experiences on the treatment of MRONJ in the Maxillofacial Surgery Department of West China Hospital of Stomatology, Sichuan University, and discuss the strategies to improve the clinical process.

Various Therapeutic Methods for the Treatment of Medication-Related Osteonecrosis of the Jaw (MRONJ) and Their Limitations: A Narrative Review on New Molecular and Cellular Therapeutic Approaches

Medication-related osteonecrosis of the jaw (MRONJ) is one of the most interesting diseases in the field of maxillofacial surgery. In addition to bisphosphonates, the use of antiresorptive and antiangiogenic agents is known to be the leading cause. However, the exact pathogenesis of MRONJ has not been established, and various hypotheses have been proposed, such as oxidative stress-related theory. As a result, a definitive treatment protocol for MRONJ has not been identified, while various therapeutic approaches are applied to manage patients with MRONJ. Although the surgical approach to treat osteomyelitis of the jaw has been proven to be most effective, there are limitations, such as recurrence and delayed healing. Many studies and clinical trials are being conducted to develop another effective therapeutic modality. The use of some materials, including platelet concentrates and bone morphogenetic proteins, showed a positive effect on MRONJ. Among them, teriparatide is currently the most promising material, and it has shown encouraging results when applied to patients with MRONJ. Furthermore, cell therapy using mesenchymal stem cells showed promising results, and it can be the new therapeutic approach for the treatment of MRONJ. This review presents various treatment methods for MRONJ and their limitations while investigating newly developed and researched molecular and cellular therapeutic approaches along with a literature review.

Success Rate and Safety of Dental Implantology in Patients Treated With Antiresorptive Medication: A Systematic Review

There is no agreement of data on the subject of implant failure and the development of osteonecrosis in patients receiving antiresorptive agents. The purpose of this systematic review is to evaluate whether dental implants placed in patients on antiresorptive medication have an increased failure rate and whether the implant placement or the implant existence are risk factors for developing medication-related osteonecrosis of the jaw (MRONJ). An electronic search was conducted in PubMed/Medline, and all publications fulfilling the inclusion criteria were included. The search was completed by a hand research of the references cited in all electronic identified publications, resulting in 411 articles. Based on the inclusion criteria, 32 studies were included, with a total of 5221 patients, 12 751 implants, 618 cases of implants loss, and 136 cases of MRONJ analyzed. Because of the small number of studies, most of which were characterized by a low level of quality, it cannot be established that the use of antiresorptive medication affects dental implant survival rates. The risk of MRONJ as an early or late complication is also not well established. Therefore, successful dental implant procedures in patients receiving antiresorptive medication might be possible, but more studies need to be carried out in the future to verify this topic. Apart from intravenous antiresorptive drugs, which remain an absolute contraindication, the use of antiresorptive medication is not a contraindication to dental implantology, but it must be accompanied by careful treatment planning, informing patients about possible complications, and essential long follow-up periods.

Microarchitecture of medication-related osteonecrosis of the jaw (MRONJ); a retrospective micro-CT and morphometric analysis

Medication-related osteonecrosis of the jaw (MRONJ) is a severe side effect of antiresorptive (AR) drugs such as bisphosphonates (BP) and denosumab (Dmab). Although several risk factors are described, the etiology of MRONJ is still not fully elucidated. Bone-strengthening is the primary aim of antiresorptive therapy; however, overly increased bone mass and microcrack accumulation are also discussed in MRONJ etiologies. The aim of this study is to evaluate the microarchitecture of jaw bones with micro-computed tomography (micro-CT) in AR-treated patients with or without MRONJ. Human jaw bone samples of AR-treated patients were separated into 11 groups by AR treatment bisphosphonate (BP), denosumab (Dmab), both (M) and control groups. Subgroups were divided according to the clinical localization as AR-exposed vital jaw bone (BP_exp, Dmab_exp, M_exp), osteonecrosis-margin of a sequestrum (BPO_mar, DmabO_mar, MO_mar) and osteonecrosis-sequestrum (BPO_seq, DmabO_seq, MO_seq). Healthy jaw bone (C_HB) and osteoporotic jaw bone (C_OP) represent control groups. Samples underwent retrospective micro-CT and morphometric analysis in representative units by bone volume fraction (BV/TV), bone surface density (BS/BV), trabecular thickness (Tr.Th.), trabecular number (Tr.N.), trabecular space (Tr.Sp.), Euler characteristic for bone connectivity, bone mineral density (BMD) and tissue mineral density (TMD). A total of 141 samples from 78 patients were analyzed. BV/TV of M_exp group (mean: 0.46 ± 0.27) was significantly higher than in the C_OP group (mean: 0.14 ± 0.05; p = 0.0053). Tr.Th. differed significantly between the BP_exp group (mean: 0.32 ± 0.15) and the M_exp group (mean: 0.57 ± 0.20; p = 0.0452) as well as between the BPO_seq group (mean: 0.25 ± 0.10) and the MO_seq group (mean: 0.39 ± 0.18; p = 0.0417). Signs of trabecular thickening and unorganized trabecular microarchitecture from AR-exposed- to sequestrum groups, were analyzed in 3D reconstructions. However, BS/BV, Tr.N., and Tr.Sp. showed no significant differences. Euler characteristic of the BPO_seq group (median: 7.46) doubled compared to that of the BP_exp group (median: 14.97; p = 0.0064). Mineralization parameters BMD and TMD were similar in all groups. Findings show evidence of enhanced bone mass and suspect microarchitecture in some AR-treated jaw bone compared to osteoporotic jaw bone. Despite increased bone mass, some MRONJ samples showed decreased trabecular connectivity by Euler characteristic compared to AR-treated jaw bone. These samples may indicate extensive ossification and ineffective bone mass with superficially higher bone mass without existing or even reduced mechanical stability, indicated by connectivity loss. This result might also suggest a high risk to microcrack accumulation. At some point, possibly some kind of over-ossification could lead to under-nourishment and microarchitectural weakness, creating instability, subsequently increasing vulnerability to MRONJ.

The Role of the Immune Response in the Development of Medication-Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a rare but serious adverse drug effect. There are multiple hypotheses to explain the development of MRONJ. Reduced bone remodeling and infection or inflammation are considered central to the pathogenesis of MRONJ. In recent years, increasing evidence has shown that bisphosphonates (BPs)-mediated immunity dysfunction is associated with the pathophysiology of MRONJ. In a healthy state, mucosal immunity provides the first line of protection against pathogens and oral mucosal immune cells defense against potentially invading pathogens by mediating the generation of protective immunoinflammatory responses. In addition, the immune system takes part in the process of bone remodeling and tissue repair. However, the treatment of BPs disturbs the mucosal and osteo immune homeostasis and thus impairs the body's ability to resist infection and repair from injury, thereby adding to the development of MRONJ. Here, we present the current knowledge about immunity dysfunction to shed light on the role of local immune disorder in the development of MRONJ.

Osteonecrosis of the Jaw Beyond Bisphosphonates: Are There Any Unknown Local Risk Factors?

INTRODUCTION

Bisphosphonate (BP)-related osteonecrosis of the jaw (BRONJ) is a complication of intravenous (IV) BP therapy. BP therapy locally affects the dentoalveolar area, while systemic effects are associated with parenteral/IV BP use. Despite numerous publications, the pathogenesis of BRONJ is not fully understood, as only some patients receiving IV BPs develop BRONJ.

PURPOSE

Can impaired bone remodeling (found in aseptic-ischemic osteonecrosis of the jaw [AIOJ], bone marrow defects [BMD], or fatty-degenerative osteonecrosis of the jaw [FDOJ]) represent a risk factor for BRONJ formation?

PATIENTS AND METHODS

A literature search clarified the relationship between AIOJ, BMD, FDOJ, and BRONJ, in which common characteristics related to signal cascades, pathohistology, and diagnostics are explored and compared. A case description examining non-exposed BRONJ is presented.

DISCUSSION

Non-exposed BRONJ variants may represent one stage in undetected BMD development, and progression to BRONJ results from BPs.

CONCLUSION

Unresolved wound healing at extraction sites, where wisdom teeth have been removed for example, may contribute to the pathogenesis of BRONJ. With IV BP administration, persisting AIOJ/BMD/FDOJ areas may be behind BRONJ development. Therapeutic recommendations include IV BP administration following AIOJ/BMD/FDOJ diagnosis and surgical removal of ischemic areas. BPs should not be regarded as the only cause of osteonecrosis.

Morphological and immunohistochemical features of tooth extraction sites in rats treated with alendronate, raloxifene, or strontium ranelate

OBJECTIVE

The aim of this study was to evaluate morphological and immunohistochemical features of tooth extraction sites in rats subjected to different antiresorptive drugs.

MATERIALS AND METHODS

Wistar rats were allocated into 4 groups according to the treatment: (1) alendronate, (2) raloxifene, (3) strontium ranelate, and (4) control. The animals underwent tooth extraction (60th day of treatment) and afterwards were euthanized (90th day of treatment). Tooth extraction sites were analyzed by means of scanning electron microscopy (SEM), hematoxylin-eosin staining (H&E), and immunohistochemical staining (RANKL and OPG).

RESULTS

On H&E analysis, the alendronate group showed greater amounts of non-vital bone, biofilm, inflammatory infiltrate and root fragment, and smaller amount of vital bone. The strontium ranelate group showed great amount of non-vital bone. This group also had lower levels of OPG, while the alendronate group showed lower OPG and RANKL than the other groups. On SEM analysis, the alendronate group showed a considerable number of microcracks on the alveolar bone surface and few Howship lacunae and lack of bone cells as well. The raloxifene, strontium ranelate, and control groups showed a large number of bone cells and Howship lacunae on the bone surface and few microcracks.

CONCLUSION

Alendronate therapy is associated with macro- and microscopic features of medication-related osteonecrosis of the jaw at tooth extraction sites, whereas raloxifene therapy is not, and strontium ranelate therapy is associated with non-vital bone.

CLINICAL RELEVANCE

Osteonecrosis of the jaws is a serious side effect of alendronate therapy, where tooth extraction is a major risk factor. Considering the significant number of patients undergoing antiresorptive therapies worldwide, the present study investigated whether raloxifene and strontium ranelate interfere with bone repair after tooth extraction in a similar way to bisphosphonates.

Bisphosphonate-associated osteonecrosis of the jaw

INTRODUCTION

The purpose of this systematic review was to determine the possible risk factors related to pathophysiology of bisphosphonate-related osteonecrosis of the jaw (BRONJ) and identify adequate treatment strategies available and success rates.

EVIDENCE ACQUISITION

We performed a search for publications about the treatment of BRONJ, published between 2003 and 2018 in the PubMed/Medline data base using the key words: "Bisphosphonate-Associated Osteonecrosis of the Jaw" OR "Bisphosphonate Osteonecrosis" OR "BRONJ", based on the list of MeSH and DeCS.

EVIDENCE SYNTHESIS

According to pre-established criteria for data collection concerning the treatment of BRONJ, we found 19 articles covering a total of 400 patients. Treatments that showed good outcomes were Ozone, PRF, PRP/Debridement/Laser bio-stimulation, Laser surgery and Laser surgery/Laser bio-stimulation. HBO did not achieve good results and was used in only 10 patients. BRONJ is a rare condition in patients with osteoporosis/other pathologies using BP orally. These patients had long exposure time and cumulative doses of BPs until onset of the lesion. The oncological patients were exposed to more potent intravenously administered BPs such as pamidronate and zoledronate. These patients had a shorter exposure time until onset of the lesion.

CONCLUSIONS

The treatment of BRONJ is still under debate and there are promising treatments that need randomized trials with larger numbers of patients to confirm their results. Patients receiving BPs or those who will start treatment should be encouraged to perform preventive dental treatment and maintain good oral hygiene.

Replacing one evil with another: Is the fibula really a dispensable spare part available for transfer in patients with medication-related osteonecrosis of the jaws?

Because of the long-term and consecutive use of different causative agents, clinicians are increasingly encountering patients needing restoration of the stomatognathic system after surgical resection of highly advanced necroses of the jaw. For plastic restoration in these cases, microvascular reconstruction seems to represent the most viable option. According to the limited data available, the risks of this operation are considered comparable with those faced by other patient cohorts. We report here the case of a patient who suffered 2 successive pathologic fractures of the tibia after microsurgical reconstruction of the mandible with a free fibula flap. This exemplifies a general problem, especially because the patient also suffered from a treatment-refractory infection of the transplanted bone. Although the present literature indicates otherwise, fibula transplants might not be the gold standard in these cases. Therefore, alternatives to transplants from the weight-bearing parts of the body need to be considered until more data are available.

Saliva diagnostics in patients suffering from bisphosphonate-associated osteonecrosis of the jaw: Results of an observational study

OBJECTIVE

One of the severe side effects of bisphosphonate (BP) therapy is bisphosphonate-associated osteonecrosis of the jaw (BONJ). However, there is no information available about its pathogenesis. Hence, the aim of this observational study was to contribute to discerning this pathogenesis by comparing salivary quantity and quality in patients with BONJ and undergoing BP treatment.

MATERIALS AND METHODS

This study included 60 patients divided into three groups. The first group consisted of 20 patients with established BONJ, the second group had 20 patients undergoing BP treatment, and the third group comprised 20 healthy individuals. These groups were analysed for the flow rate of stimulated saliva, buffer capacity, and salivary pH level.

RESULTS

Reduced salivation was observed in a significantly high number of patients with established BONJ (n = 8) and those undergoing BP treatment (n = 9) in comparison with the healthy control group (n = 4; p = 0.039). Though the distribution of the mean value of stimulated saliva flow rates in patients undergoing BP treatment was lower than in the control group, the difference was not significant. Moreover, there were no significant differences in the salivary pH level and buffer capacity in patients undergoing BP treatment as compared with the healthy control group.

CONCLUSIONS

It is possible that the quantity of human saliva is affected by BP treatment. This reduction in saliva production could have a negative effect on mucosal health and is perhaps a cofactor in the pathogenesis of BONJ.

Microbial diversity in infections of patients with medication-related osteonecrosis of the jaw

OBJECTIVES

A central role of infections in the treatment of MRONJ patients is widely accepted. An investigation of the MRONJ lesions' biofilms as potential pathogens seems logical.

MATERIALS AND METHODS

We investigated the clinical data of our MRONJ patients who received surgery in advanced stage of the disease. Special attention was granted to the local colonizers harvested from osseous MRONJ specimens and submucosal putrid infections.

RESULTS

Eleven out of 71 patients presented a spontaneous onset of the disease and for 60 out of 71 patients a trigger was detected. Breast cancer (29.6%) and prostate cancer (22.5%) were the most frequent underlying disease for prescription of an antiresorptive therapy, mostly zoledronate. Submucosal soft tissue biofilms significantly differed from biofilms harvested from the MRONJ lesions bottom, yet the most frequent bacteria were equally present in both groups: Streptococcus species (spp.), Prevotella spp., Actinomyces spp., Veillonella spp., and Parvimonas micra. The cephalosporins, cefuroxime and cefotaxime, and ß-lactam antibiotics with ß-lactamase inhibitor revealed the greatest susceptibility for the detected bacteria.

CONCLUSION

The bacteria from the submucosal areas and the bottom of the infected bone presented comparable susceptibility to the common antibiotics regimes. Streptococcus spp., Prevotella spp., and Veillonella spp. present a high abundance in MRONJ lesions beside Actinomyces spp. The MRONJ lesions bottom is in many cases not infected by Actinomyces spp.

CLINICAL RELEVANCE

The removal of the necrotic bone reduces the variety of bacteria found in MRONJ lesions, in particular at the bottom of the lesion.

Clinical characteristics and recurrence-related factors of medication-related osteonecrosis of the jaw

OBJECTIVES

The purpose of this study was to investigate the demographic and clinical characteristics of patients with medication-related osteonecrosis of the jaw (MRONJ) and to elucidate factors affecting recurrence in surgical treatment.

MATERIALS AND METHODS

A total of 51 patients who were diagnosed with MRONJ were analyzed according to demographic and clinical features and treatment results through a retrospective chart review from 2013 to 2017 in the Department of Oral and Maxillofacial Surgery, Korea University Anam Hospital, Seoul in Korea.

RESULTS

Alendronate composed the majority of medication doses (55.6%), followed by ibandronate (20.0%), risedronate (15.6%), and zoledronate (6.7%). Forty patients (88.9%) were given oral medication, and five patients (11.1%) were intravenously treated, and the mean duration of medication use was 61.1±42.9 months. A total of 10 patients (22.2%) had a drug holiday before MRONJ-induced dental treatment lasting an average of 6.8±7.0 months. MRONJ occurred 2.7 times more in the mandible, with 41 cases (73.2%) occurring in the mandible and 15 cases (26.8%) occurring in the maxilla, and the prevalence of affected posterior parts (premolar-molar) was six times greater than that of the anterior parts (incisor-canine) (48 cases vs 8 cases, 85.7% vs 14.3%). The most common dental cause of MRONJ was tooth extraction (69.6%). Regarding recurrence, there was no statistical difference in recurrence rate according to either site or stage. However, recurrence occurred in 4 out of 34 cases (11.8%) in the primary closure group and 9 out of 20 cases (45.0%) in the secondary healing group, and there was a statistical difference with respect to closure technique.

CONCLUSION

The identified risk factors in patients taking bone resorption inhibitors can aid dental clinicians in ensuring prevention and proper treatment of MRONJ.

Vitamin D supplementation: Hypothetical effect on medication-related osteonecrosis of the jaw

Vitamin D is an important nutrient for bone health and skeleton growth. Few foods are natural sources of this secosteroid; this is the reason why the consumption of vitamin D as a dietary supplement is becoming common in developed countries. For many years vitamin D has been considered crucial in the treatment and prevention of the Global Burden of Disease and in a reduction in mortality among elder people. Many health care providers prescribe these supplements in the management of osteoporosis and metabolic bone diseases; specifically in the primary prevention of fractures. Recently medication-related osteonecrosis of the jaw (MRONJ) has been reported as severe late sequelae of antiresorptive therapies (i.e., bisphosphonates and some monoclonal antibodies). Although MRONJ-related pathophysiology is not fully understood, there are three fundamental theories to explain it: (1) the inhibition of osteoclasts, (2) the inhibition of angiogenesis and (3) the processes of inflammation-infection. Recent advances in Vitamin D research have shown that this secosteroid can play a potential pivotal role in many of the different etiological pathways of MRONJ. Furthermore, there are a large number of co-morbidities between the deficit of this vitamin and other MRONJ concomitant outcomes. Our hypothesis argues that the low-risk and low-cost vitamin D dietary supplementation may prove to be suitable for use as a practical MRONJ prevention strategy. The described framework gives more insight into the study of disease mechanisms, search of potential biomarkers, and therapeutic targets in MRONJ.

Bone-site-specific responses to zoledronic acid

OBJECTIVES

Bisphosphonates are widely used to treat bone diseases such as osteoporosis. However, they may cause osteonecrosis of the jaw. Here, we investigated whether in vivo exposure to bisphosphonates has a different effect on long bone and jaw osteoclasts, and on the turnover of these different bones.

MATERIALS AND METHODS

Zoledronic acid (0.5 mg kg^-1 weekly) was administered intraperitoneally to 3-month-old female mice for up to 6 months. The effects on the number of osteoclasts, bone mineralization and bone formation were measured in the long bones and in the jaw.

RESULTS

Long-term treatment with zoledronic acid reduced the number of jaw bone marrow cells, without affecting the number of long bone marrow cells. Zoledronic acid treatment did not affect the number of osteoclasts in vivo. Yet, the bisphosphonate increased bone volume and mineral density of both long bone and jaw. Interestingly, 6 months of treatment suppressed bone formation in the long bones without affecting the jaw. Unexpectedly, we showed that bisphosphonates can cause molar root resorption, mediated by active osteoclasts.

CONCLUSIONS

Our findings provide more insight into bone-site-specific effects of bisphosphonates and into the aetiology of osteonecrosis of the jaw. We demonstrated that bisphosphonates can stimulate osteoclast activity at the molar roots.

Temporal course of avascular femoral head necrosis in patients with pemphigus vulgaris

BACKGROUND AND OBJECTIVES

Pemphigus vulgaris (PV) is typically treated with systemic corticosteroids and immunosuppressive agents. Avascular necrosis (AVN) of the femoral head is a well-recognized major complication of corticosteroid therapy. The characteristics of this serious complication in PV remain unknown.

PATIENTS AND METHODS

Uncontrolled, retrospective study of all PV-related AVN cases diagnosed at an Iranian autoimmune bullous disease clinic between 1985 and 2013.

RESULTS

Of the 2,321 medical records of PV patients reviewed, 45 (1.93 %) cases showed femoral AVN, with 30 (66.7 %) individuals being male. The mean age at diagnosis of AVN was 47.4 ± 14.2 years. The mean interval between the diagnosis of PV and the onset of AVN was 25.3 ± 18.3 months. With the exception of eight cases (17.8 %), the majority of patients developed AVN within three years after the diagnosis of PV. The mean cumulative dose of prednisolone in patients with AVN was 13,115.8 ± 7041.1 mg. There was a strong correlation between the total prednisolone dose and the time of onset of AVN (p = 0.001). In patients with a history of alendronate intake, that interval was significantly shorter (p = 0.01).

CONCLUSIONS

Occurring in about 2 % of patients, AVN is a serious complication of corticosteroid treatment in patients with PV, predominantly in the first three years of treatment. In individuals receiving higher doses of prednisolone, AVN tends to occur earlier.

Osteonecrosis of the Jaw-a Bone Site-Specific Effect of Bisphosphonates

A known complication that can occur in patients using bisphosphonates (BPs) is osteonecrosis of the jaw (ONJ). ONJ features bone exposure that may be associated with severe pain, swelling, local infection, and pathological fracture of the jaw. Current literature indicates that a complex combination of factors is necessary to induce ONJ. Several hypotheses about the pathophysiology of ONJ were previously reported. Here, we review these hypotheses and introduce new ideas and suggestions on this topic, focusing on bone site-specific cells, and the effect that BPs and other anti-resorptive drugs have on those cells. Gaining more insight into bone site-specific effects may help to better understand the pathogenesis ONJ, and contribute to the development of new bone site-specific anti-resorptive drugs.

Prevalence of Medication-Related Osteonecrosis of the Jaw in Patients with Breast Cancer, Prostate Cancer, and Multiple Myeloma

Medication-related osteonecrosis of the jaw is a known side-effect of antiresorptive therapy in patients with malignant diseases. Nevertheless, the exact pathogenesis is still unknown and published prevalences show a significant range. The aim of the presented paper was to assess the prevalence of osteonecrosis (ONJ) in breast cancer, prostate cancer, and multiple myeloma patients receiving parenteral antiresorptive therapy. For this reason a PubMed search was performed and 69 matching articles comprising 29,437 patients were included in the analysis. Nine-hundred fifty-one cases of jaw necrosis were described. The overall ONJ-prevalence was 2.09% in the breast cancer group, 3.8% in the prostate cancer group, and 5.16% for multiple myeloma patients.

Medication-Related Osteonecrosis of the Jaw: New Insights into Molecular Mechanisms and Cellular Therapeutic Approaches

In recent years, medication-related osteonecrosis of the jaw (MRONJ) became an arising disease due to the important antiresorptive drug prescriptions to treat oncologic and osteoporotic patients, as well as the use of new antiangiogenic drugs such as VEGF antagonist. So far, MRONJ physiopathogenesis still remains unclear. Aiming to better understand MRONJ physiopathology, the first objective of this review would be to highlight major molecular mechanisms that are known to be involved in bone formation and remodeling. Recent development in MRONJ pharmacological treatments showed good results; however, those treatments are not curative and could have major side effects. In parallel to pharmacological treatments, MSC grafts appeared to be beneficial in the treatment of MRONJ, in multiple aspects: (1) recruitment and stimulation of local or regional endogenous cells to differentiate into osteoblasts and thus bone formation, (2) beneficial impact on bone remodeling, and (3) immune-modulatory properties that decrease inflammation. In this context, the second objective of this manuscript would be to summarize the molecular regulatory events controlling osteogenic differentiation, bone remodeling, and osteoimmunology and potential beneficial effects of MSC related to those aspects, in order to apprehend MRONJ and to develop new therapeutic approaches.

Legal liability in bisphosphonate-related osteonecrosis of the jaw

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is an adverse reaction that may occur in patients administered with bisphosphonates (BP). This condition can cause high morbidity and hinder quality of life. Its treatment is complex and often unsatisfactory, and prevention strategies may have limited effectiveness, if any. Thus, managing patients treated with BP may result in exposure of the practitioner to legal liability or malpractice claims: legal actions pursuant to BRONJ are reported to be underway on three continents. Nonetheless, the attribution of liability, if any, is a complex process requiring, on the basis of current knowledge, a robust and pragmatic approach to the facts, which must be identified from the point of view of the time, place and individuals involved. This means a comprehensive consideration of the sequence of actions from bisphosphonates prescription to BRONJ occurrence (as well as immediately after, and any action potentially related to its causation or worsening) is required in order to determine if a breach in informing, diagnosing, managing or referring the patient took place, as well as determining if the patient was compliant in attending to prescriptions and follow-up programmes.

Maxilla Osteonecrosis: a differential diagnosis in patients with metastatic cancer on bisphosphonates

Bisphosphonate-induced osteonecrosis of the mandible and/or maxilla is an increasingly recognized, though still rare complication of bisphosphonate therapy. In the present case, the patient presented with a seven-month history of maxillary sinusitis and pain, and was originally diagnosed with a bony metastasis from her primary breast cancer. However, surgical excision and biopsy led to a diagnosis of bisphosphonate-induced osteonecrosis of the maxilla. As bisphosphonates are often prescribed for patients with metastatic disease, it is important to recognize that bisphosphonate-induced osteonecrosis may present similarly to bony metastases.

Osteonecrosis of the jaw (ONJ): diagnosis and management in 2015

Osteonecrosis of the jaw (ONJ) has been associated with the use of aminobisphosphonates and denosumab. The vast majority (>90%) of cases occur in the oncology patient population receiving high doses of intravenous bisphosphonates or subcutaneous denosumab. The incidence of ONJ in the osteoporosis patient population is very low and is estimated at 1-90 per 100,000 patient-years of exposure. In the oncology patient population the incidence appears to be related to dose and duration of exposure, and prevalence has been estimated to be as high as 18.6%. A number of risk factors in addition to antiresorptive therapy have been identified. These include the presence of periodontal disease, oral surgical procedures with extractions or implants, radiation therapy, chemotherapy, diabetes, glucocorticoid use, and smoking. Antiangiogenic agents appear to contribute to the risk of ONJ, however, data at this time are limited and further evidence is required prior to confirming a causal relationship. ONJ may be prevented with optimization of oral hygiene, the use of oral antimicrobial mouth rinses, as well as systemic antibiotic therapy. Individuals not responding to conservative management or in the advanced stages of ONJ may be considered for surgery, as data over the past several years have demonstrated surgical success in this patient population. Case reports have indicated that teriparatide may enhance healing. A number of experimental therapies are being evaluated and include the use of bone marrow stem cell intralesional transplantation, local application of platelet-derived growth factor, hyperbaric oxygen, tissue grafting, and low-level laser therapy. This paper summarizes the current research as well as the international consensus on the diagnosis and management of ONJ.

Role of microcracks in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw

OBJECTIVES

The aim of this study was to investigate the potential role of microcrack accumulation in the pathogenesis of bisphosphonate-related osteonecrosis of the jaw (ONJ) through an animal model.

MATERIALS AND METHODS

Twenty-four ovariectomized rats were randomly divided into a bisphosphonate group (n = 19) and control group (n = 5) and weekly injected with zoledronic acid and normal saline, respectively. After 6 weeks, surgical intervention was performed, and the injections were continued for eight additional weeks. Then, the animals were sacrificed, and ONJ lesions were inspected for the presence of microcracks using scanning electron microscopy. Measurements included bone dimension, number of cracks, crack length, and normalized indices; crack density (Cr.Dn) and crack surface density (Cr.S.Dn) were used for group comparison.

RESULTS

Both number of cracks and crack length in the bisphosphonate group were greater than those in the control group (P < 0.05). Of the 19 rats injected with bisphosphonates, 13 rats (68.4 %) were classified into the ONJ group. Cr.Dn and Cr.S.Dn were significantly greater in the ONJ group than in the non-ONJ group, indicating accumulation of unrepaired microcracks (P < 0.05). Seventy-two percent of microcracks in the ONJ group conformed to the defined length that was considered significant according to a previous literature (30-80 μm); whereas 12 % of microcracks in the non-ONJ group were considered significant (P < 0.05).

CONCLUSION

Accumulation of unrepaired microcracks was significantly associated with the development of bisphosphonate-related ONJ. Further research is required to determine the role of microcracks in the pathogenesis of bisphosphonate-related ONJ.

CLINICAL RELEVANCE

Long-term bisphosphonates use may deteriorate the biomechanical and physiological bone integrity, contributing to the pathogenesis of bisphosphonate-related ONJ.

Medication Related Osteonecrosis of the Jaw: 2015 Position Statement of the Korean Society for Bone and Mineral Research and the Korean Association of Oral and Maxillofacial Surgeons

Bisphosphonates are the most widely prescribed drugs for the treatment of osteoporosis, and are also used in malignant bone metastases, multiple myeloma, and Paget's disease, and provide therapeutic efficacy on those diseases. However, it was reported that occurrence of osteonecrosis of the jaw (ONJ) could be related with bisphosphonate exposures, and there have been many cases regarding this issue. Therefore, a clearer definition and treatment guidelines were needed for this disease. The American Society for Bone and Mineral Research (ASBMR) and American Association of Oral and Maxillofacial Surgeons (AAOMS) reported statements on bisphosphonate-related ONJ (BRONJ), and a revised version was recently presented. In the revised edition, the diagnosis BRONJ was changed to medication-related ONJ (MRONJ), which reflects a consideration of the fact that ONJ also occurs for denosumab, a bone resorption inhibitor of the receptor activator of nuclear factor-kappa B ligand (RANKL) antibody family, and bevacizumab, an anti-angiogenesis inhibitor. In 2009, a statement on ONJ was also reported locally by a relevant organization, which has served as basis for clinical treatment in Korea. In addition to the new official stance of the AAOMS and ASBMR, with an increasing pool of ONJ clinical experience, a revised version of the 2009 local statement is needed. As such, the Korean Society for Bone and Mineral Research (KSBMR) and the Korean Association of Oral and Maxillofacial Surgeons (KAOMS) have collectively formed a committee for the preparation of an official statement on MRONJ, and have reviewed recent local and international data to propose guidelines customized for the local Korean situation.

Surgical treatment of bisphosphonate-associated osteonecrosis: Prognostic score and long-term results

Over a century after the first synthesis of bisphosphonates (1897) and a decade (2003) since the initial report on bisphosphonate-related osteonecrosis of the jaw (ONJ), this osteopathy remains a serious clinical challenge. A single center longitudinal study (2005-2014) was carried out to prospectively characterize inpatients with manifest ONJ and to evaluate their outcomes. The data recorded were: medical history, bisphosphonate treatment, localization, imaging, treatment, histomorphological features, and complications. A prognostic score (modified UCONN-Score) was adopted to predict outcomes. Eighty patients were included (mean age 69.4 years; 40 male, 40 female). Breast cancer (n = 25), multiple myeloma (n = 16), and prostate cancer (n = 15) were the three most common malignancies; and cardiovascular disease (n = 31), diabetes mellitus (16), and renal disorders (6) were the most important comorbidities. The severity of ONJ was stage I in three patients, stage II in 37, and stage III in 40, being predominantly localized in the posterior mandible and needing gradual resection. The average duration of bisphosphonate treatment was 38.3 months. The typical histological aspects of ONJ were predominantly osteonecrosis, bone marrow fibrosis, and bacterial colonization (Actinomyces) with suppurative inflammation. Within the resected jawbone a primary malignancy was diagnosed in two cases. The overall success rate was 83.6% (follow-up 23.5 months), with a UCONN-Score ≥15 predicting unfavorable treatment results (OR = 5.2). The past decade has enhanced experience with ONJ treatment and knowledge about its pathogenesis, which seems to be a multistep process. This study demonstrates the importance of bone and multilayer soft tissue management, preferably as an early intervention. The UCONN-Score might help to assess individual prognosis in ONJ surgery and the potential benefit of an antiresorptive drug holiday. To our knowledge it is the first use of a prognostic score in ONJ surgery.

Infection and Medication-related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ), although initially believed to be exclusively associated with bisphosphonates, has been implicated in recent reports with additional drugs, especially the bone antiresorptive denosumab. The pathophysiology has not been fully elucidated, and no causal association between bone antiresorptive regimens and MRONJ has yet been established. However, reduced bone turnover and infection, an almost universal finding, are thought to be central to the pathogenesis of MRONJ. Both bisphosphonates and denosumab, through different pathways of action, significantly reduce the rate of bone turnover and potentially reduce the efficacy of the host defense against infection. Recent evidence questions the simplified etiology of low bone turnover causing MRONJ and offers evidence on the prominent role of infection instead. The management of MRONJ remains a significant clinical challenge, with little progress having been made on treatment. The aim of this article is to explore the current theories on the etiology of MRONJ and to emphasize the importance of infection in the development of this devastating pathology.