Osteonecrosis of the Jaw: Effect of Bisphosphonate Type, Local Concentration, and Acidic Milieu on the Pathomechanism

Bone complications of cancer treatment

With the advancements in conventional treatment modalities such as radiation, chemotherapy, and surgery, as well as the emergence of immunotherapy, the overall cure rate for solid tumor malignancies has experienced a significant increase. However, it is unfortunate that exposure to cancer treatments can have detrimental effects on the function of osteoblasts and osteoclasts, disturbing bone metabolic homeostasis in patients, as well as causing damage to bone marrow cells and other bone tissues. Consequently, certain tumor treatment options may pose a risk for subsequent bone diseases. Common bone disorders associated with cancer treatment include osteonecrosis, bone loss, and secondary bone tumors. (1)Cancer treatment-related osteonecrosis is primarily linked to the use of radiation therapy and certain chemicals, such as bisphosphonates, denosumab, antiangiogenic agents, and immunomodulators. It has been observed that high-dose radiation therapy is more likely to result in osteonecrosis. (2)Chemicals and hormones, particularly sex hormones, glucocorticoids, and thyroid hormones or thyrotropic hormones, are among the factors that can contribute to cancer treatment-related bone loss. (3)Secondary bone tumors differ from metastases originating from primary tumors, and radiotherapy plays a significant role in their development, while chemotherapy may also exert some influence. Radiogenic secondary bone tumors are predominantly malignant, with osteosarcoma being the most common type. Chemotherapy may be a risk factor for the relatively rare occurrence of secondary Ewing sarcoma of the bone. These treatment-related bone disorders have a considerable adverse impact on the prognosis of cancer patients. Hence, it is imperative to prioritize the bone health of patients undergoing cancer treatment and give it further attention.

The Potential of Enamel Matrix Derivative in Countering Bisphosphonate-Induced Effects in Osteoblasts

The suppressive effect of bisphosphonates (BPs) on bone metabolism is considered to be a major cause of medication-related osteonecrosis of the jaw (MRONJ). Enamel matrix derivative (EMD) stimulates and activates growth factors, leading to the regeneration of periodontal tissues. In this study, we aimed to explore the potential of EMD in reversing the detrimental effects of BPs on human fetal osteoblasts (hFOBs) and osteosarcoma-derived immature osteoblasts (MG63s) by assessing cell viability, apoptosis, migration, gene expression, and protein synthesis. While the suppressive effect of zoledronate (Zol) on cell viability and migration was observed, the addition of EMD significantly mitigated this effect and enhanced cell viability and migration. Furthermore, an increased apoptosis rate induced by Zol was decreased with the addition of EMD. The decreased gene expression of alkaline phosphatase (ALP), osteocalcin (OC), and the receptor activator of nuclear factors kappa-B ligand (RANKL) caused by BP treatment was reversed by the co-addition of EMD to hFOB cells. This trend was also observed for ALP and bone sialoprotein (BSP) levels in MG63 cells. Furthermore, suppressed protein levels of OC, macrophage colony-stimulating factor (M-CSF), BSP, and type 1 collagen (COL1) were recovered following the addition of EMD. This finding suggests that EMD could mitigate the effects of BPs, resulting in the recovery of cell survival, migration, and gene and protein expression. However, the behavior of the osteoblasts was not fully restored, and further studies are necessary to confirm their effects at the cellular level and to assess their clinical usefulness in vivo for the prevention and treatment of MRONJ.

A retrospective case series on bisphosphonate related osteonecrosis of the jaw in 20 cats

Introduction

This retrospective study highlights the salient aspects of a series of feline patients affected with bisphosphonate related osteonecrosis of the jaw. Though more commonly published in human literature, this presentation is rare in cats. The authors hope that this study will assist in making this a more globally known entity with subsequent improved prognosis.

Methods

Data was retrospectively obtained from the medical records between 2015 and 2021 of 20 cats with Medication Related Osteonecrosis of the Jaw. Data included patient information, clinical history, presenting complaint, systemic diseases, details referable to hypercalcemia and treatment thereof, bisphosphonate specifics (dose and duration), clinical presentation of the lesion, diagnostic testing including radiographic and histopathologic descriptions, treatment, and outcome.

Results

Pertinent results include that all 20 cats who developed Medication Related Osteonecrosis of the Jaw had been treated for idiopathic hypercalcemia with the bisphosphonate medication alendronate. Eighty-five percent of the cases had prior dental extractions at the site of MRONJ lesion. Ninety-five percent of the affected cats required a surgical procedure to control the disease. Thirty-five percent of cases required at least one revision surgery after the initial procedure was performed. Diagnosis of MRONJ was made by a correlation of diagnostic findings and patient history. No single diagnostic, or combination was pathognomonic for lesion diagnosis. As well, there were no statistically significant associations between patient variables assessed and the overall patient outcome.

Discussion

The case series reveals that cats with feline idiopathic hypercalcemia treated with alendronate may be at a risk for development of MRONJ, a serious oral condition with significant morbidity. Prior dental extraction sites in patients concurrently treated with bisphosphonate medications were often associated with MRONJ lesions. Therefore, any needed dental surgery should be performed prior to the use of bisphosphonates where possible. The authors have also included a relevant comparative literature review.

Effect of anti-resorptive therapy on implant failure: a systematic review and meta-analysis

PURPOSE

This review was conducted to systematically assess the impact of bisphosphonates (BPs) and denosumab, used as anti-resorptive therapies, on the incidence of dental implant failure.

METHODS

Electronic and manual searches were performed in accordance with the described search protocol. Only articles that met the inclusion criteria were selected. The primary outcome was implant failure, while secondary outcomes included biological complications and comorbidities. Following data extraction, a quality assessment and meta-analysis were conducted.

RESULTS

Fourteen eligible studies were included in the analysis following a qualitative evaluation. BP administration, regardless of the timing of anti-resorptive therapy, did not significantly increase the risk of implant failure (odds ratio [OR], 1.40; 95% confidence interval, 0.83-2.34). Subgroup analysis revealed a slightly higher, although statistically insignificant, risk of failure in patients with a follow-up period of 3 years or more compared to those with a follow-up duration of less than 3 years (with ORs of 2.82 and 1.53, respectively). Due to a lack of eligible studies, a meta-analysis for denosumab could not be conducted.

CONCLUSIONS

Our findings suggest that BP treatment does not compromise the survival of dental implants. Specifically, in patients with osteoporosis, implant failure rates were not significantly influenced by the administration of BPs before the placement of dental implants, suggesting that low-dose BP therapy may not contraindicate implant placement. Nevertheless, regular check-ups and maintenance periodontal treatment must not be neglected, and concomitant biological factors should be considered to ensure the long-term success of implant rehabilitation.

A Mapping Review of the Pathogenesis of Peri-Implantitis: The Biofilm-Mediated Inflammation and Bone Dysregulation (BIND) Hypothesis

This mapping review highlights the need for a new paradigm in the understanding of peri-implantitis pathogenesis. The biofilm-mediated inflammation and bone dysregulation (BIND) hypothesis is proposed, focusing on the relationship between biofilm, inflammation, and bone biology. The close interactions between immune and bone cells are discussed, with multiple stable states likely existing between clinically observable definitions of peri-implant health and peri-implantitis. The framework presented aims to explain the transition from health to disease as a staged and incremental process, where multiple factors contribute to distinct steps towards a tipping point where disease is manifested clinically. These steps might be reached in different ways in different patients and may constitute highly individualised paths. Notably, factors affecting the underlying biology are identified in the pathogenesis of peri-implantitis, highlighting that disruptions to the host-microbe homeostasis at the implant-mucosa interface may not be the sole factor. An improved understanding of disease pathogenesis will allow for intervention on multiple levels and a personalised treatment approach. Further research areas are identified, such as the use of novel biomarkers to detect changes in macrophage polarisation and activation status, and bone turnover.

Effect of agents affecting bone homeostasis on short- and long-term implant failure

OBJECTIVES

To review the current evidence on the relationship between agents that affect bone homeostasis and dental implant failures.

MATERIALS AND METHODS

Electronic searches for bisphosphonates, denosumab, methotrexate, corticosteroids, romosozumab, sunitinib, and bevacizumab were performed using PubMed, MEDLINE (OVID), EMBASE (OVID), Cochrane Central Register of Controlled Trials (Cochrane Library), Cochrane Oral Health Group Trials Register (Cochrane Library) and Web of Science (Thomson Reuters). Manual searches were also conducted to complement the digital searches for recent issues.

RESULTS

Previous publications suggested that bisphosphonates do not compromise the survival of dental implants. However, one study documented an increased risk of implant failure in patients who had received high-dose of intravenous bisphosphonate therapy after implant rehabilitation. There has been an issue of MRONJ around implants in patients who have successfully received implant therapy before and after antiresorptive therapy, leading to late implant failure. Despite evidence on the detrimental effects of denosumab, methotrexate and corticosteroids on bone metabolism, their role in implant survival is not conclusive.

CONCLUSIONS

At present, there is insufficient evidence to establish a potential connection between agents that affects bone homeostasis and implant failure. However, some studies have reported negative results for implant therapy. In addition, implant-related sequestration in patients who received anti-resorptive therapy, despite of successful osseointegration, is also noticeable. Although limited studies are available at present, clinicians should still carefully consider the potential hazards and take appropriate precautions to minimize the risks associated with the medications and implant therapy.

Targeting a therapeutically relevant concentration of alendronate for in vitro studies on osteoblasts

OBJECTIVE

Bisphosphonates like alendronate mainly exert their effects on osteoclasts. However, osteoblasts are also affected, but exposed to a much lower concentration in vivo than the osteoclasts. Given that the effects are dose-dependent, the intention of the study was to identify a therapeutically relevant concentration of alendronate for in vitro studies on osteoblasts.

MATERIALS AND METHODS

Primary human osteoblasts were incubated with alendronate (5, 20 and 100 µM) for 1, 3, 7 and 14 days. Proliferation and viability were assessed, and the effects on cellular growth and function were evaluated by multianalyte profiling of selected proteins in cell culture media using the Luminex 200^TM.

RESULTS

The viability was not affected by any of the dosages. Exposure to 5 µM alendronate had a neutral effect on osteoblast proliferation, and on secretion of osteogenic and inflammatory markers, while enhancing synthesis of a marker of angiogenesis. 20 µM alendronate induced a decline in proliferation and affected angiogenic and osteogenic biomarkers adversely. 100 µM alendronate reduced proliferation dramatically, and this dosage was excluded from further experiments.

CONCLUSION

A concentration of 5 µM alendronate exerted effects on human osteoblasts that may translate to those observed in vivo and could therefore be relevant for in vitro studies.

Risk factors associated with onset of medication-related osteonecrosis of the jaw in patients treated with denosumab

Objectives

While risk factors of bisphosphonate (BP) associated osteonecrosis of the jaw have been properly analyzed, studies focusing on risk factors associated with denosumab (DNO) are sparse. The purpose of this study was to identify risk factors influencing the onset of medication-related osteonecrosis of the jaw (MRONJ) in patients receiving antiresorptive treatment (ART) with DNO by comparing patients suffering from MRONJ and patients without MRONJ. Multiple variables were evaluated including the impact of a previous BP intake.

Materials and methods

A retrospective single-center cohort study with patients receiving DNO was conducted. One-hundred twenty-eight patients were included and divided into three groups: I (control, n = 40) receiving DNO with absence of MRONJ; group II (Test 1, n = 46), receiving DNO with presence of MRONJ; and group III (Test 2, n = 42) sequentially receiving BP and DNO with presence of MRONJ. Patients’ medical history, focusing on the identification of MRONJ risk factors, was collected and evaluated. Parameters were sex, age, smoking habit, alcohol consumption, underlying disease (cancer type, osteoporosis), internal diseases, additional chemo/hormonal therapy, oral inflammation, and trauma.

Results

The following risk factors were identified to increase MRONJ onset significantly in patients treated with DNO: chemo/hormonal therapy (p = 0.02), DNO dosage (p < 0.01), breast cancer (p = 0.03), intake of corticosteroids (p = 0.04), hypertension (p = 0.02), diabetes mellitus (p = 0.04), periodontal disease (p = 0.03), apical ostitis (p = 0.02), and denture use (p = 0.02). A medication switch did not affect MRONJ development (p = 0.86).

Conclusions

Malignant diseases, additional chemotherapy, DNO dosage, and oral inflammations as well as diabetes mellitus and hypertension influence MRONJ onset in patients treated with DNO significantly.

Clinical relevance

Patients receiving ART with DNO featuring aforementioned risk factors have a higher risk of MRONJ onset. These patients need a sound and regular prophylaxis in order to prevent the onset of MRONJ under DNO treatment.

Medication-Related Osteonecrosis of the Jaw: A Critical Narrative Review

Background: Nearly two decades have passed since a paradoxical reaction in the orofacial region to some bone modifying agents and other drugs was recognized, namely medication-related osteonecrosis of the jaw (MRONJ). Purpose: The aim of this manuscript was to critically review published data on MRONJ to provide an update on key terminology, concepts, and current trends in terms of prevention and diagnosis. In addition, our objective was to examine and evaluate the therapeutic options available for MRONJ. Methods: The authors perused the most relevant literature relating to MRONJ through a search in textbooks and published articles included in several databases for the years 2003–2021. Results and conclusions: A comprehensive update of the current understanding of these matters was elaborated, addressing these topics and identifying relevant gaps of knowledge. This review describes our updated view of the previous thematic blocks, highlights our current clinical directions, and emphasizes controversial aspects and barriers that may lead to extending the accumulating body of evidence related to this severe treatment sequela.

Medication-related osteonecrosis of the jaw (MRONJ) and eNOS Polymorphisms in multiple myeloma patients: a single center experience

Background

Multiple myeloma (MM) constitutes approximately 10% of hematological malignancies. Bisphosphonates have established themselves in solid organ metastasis and multiple myeloma lytic bone lesions by inhibiting osteoclast activation. Medication-related osteonecrosis of the jaw (MRONJ) emerges as an important complication. Investigating host-based factors, and developing personal risk factors gain importance in the development mechanism of MRONJ. We aimed to reveal the different genotype polymorphisms, and clinical effects of eNOS in patients with a diagnosis of MRONJ in MM patients.

Methods

Medical records and blood samples were collected from 60 MRONJ patients with MM and 60 healthy controls. Inclusion criteria was having an exposed maxillofacial bone for more than eight weeks, a history of bisphosphonates, and no history of radiation therapy for the jaws. eNOS G894T and intron 4 VNTR were calculated by polymerase chain reaction and/or restriction fragment length polymorphism.

Results

eNOS G894T and VNTR genotypes and alleles were compared statistically with the healthy control group. There was no significant difference between the two groups. In comparison between G894T and clinical parameters, aphthous stomatitis was more common in TT genotype, while DMFT > 3 was more common in TG-GG genotype (p = 0.035, 0.023).

Conclusions

eNOS induces osteogenesis in bone metabolism, with its regulatory effects on bone remodeling and also NO induced angiogenesis takes place indirectly with its protective effect on endothelial functions. We see that these polymorphisms affecting the entire process of bone remodeling and angiogenesis, especially mucosal damage, which is the triggering factor of MRONJ pathology, have been revealed in the MM patient group. Considering the MRONJ initiating factors, it is necessary to emphasize the importance of our study results. It should be seen as an important step for new studies towards MRONJ and its treatment.

Infection as an Important Factor in Medication-Related Osteonecrosis of the Jaw (MRONJ)

Medication-related osteonecrosis of the jaw (MRONJ) has become a well-known side effect of antiresorptive, and antiangiogenic drugs commonly used in cancer management. Despite a considerable amount of literature addressing MRONJ, it is still widely accepted that the underlying pathomechanism of MRONJ is unclear. However, several clinical and preclinical studies indicate that infection seems to have a major role in the pathogenesis of MRONJ. Although there is no conclusive evidence for the infection hypothesis yet, available data have shown a robust association between local infection and MRONJ development. This observation is very critical in order to implement policies to reduce the risk of MRONJ in patients under antiresorptive drugs. This critical review was conducted to collect the most reliable evidence regarding the link between local infection and MRONJ pathogenesis.

Nitrogen-containing bisphosphonate-loaded micro-arc oxidation coating for biodegradable magnesium alloy pellets inhibits osteosarcoma through targeting of the mevalonate pathway

Osteosarcoma (OS) remains one of the most threatening primary malignant human tumors of the bone, especially in the first or second decade of life. Unfortunately, the clinical therapeutic efficacy has not substantially improved over the past four decades. Therefore, to achieve efficient tumor eradication, a new approach to prevent tumor recurrence is urgently needed. Here, we develop a new bisphosphonate (BP)-loaded microarc oxidation (MAO) coated magnesium-strontium (Mg-Sr) alloy pellet that can inhibit OS, and we illuminate the cellular and molecular mechanisms of the inhibiting effect. To generate such pellets, nitrogen-containing BP is chemically conjugated with a MAO coating on hollow Mg-Sr alloys. We demonstrate that BP coated Mg pellet has multiple desired features for OS therapy through in vitro and in vivo studies. At the cellular level, BP coated Mg pellets not only induce apoptosis and necrosis, as well as antitumor invasion of OS cells in the two-dimensional (2D) cell culture environment, but also damage the formation of multicellular tumor spheroids by OS cell lines in the three-dimensional (3D) cell culture environment. At the in vivo level, BP coated Mg pellets can destroy tumors and prevent neoplasm recurrence via synergistic Mg degradation and drug release. It is further suggested that the superior inhibitory effect on OS of our pellet is achieved by inhibiting the mevalonate pathway at the molecular level. Hence, these results collectively show that the BP coated Mg pellet is a promising candidate for future applications in repairing defects after tumor removal in OS therapy.

Gingival cell growth with antiresorptive treatment combined with corticosteroids or antiestrogen

Objectives

Antiresorptive treatment has been shown to impair mucosal cell proliferation, migration, and viability. However, in the clinic, antiresorptives are often used in combination with other drugs. We studied the effect of antiresorptives combined with a corticosteroid or antiestrogen on oral mucosal keratinocytes and fibroblasts.

Material and methods

Human gingival keratinocyte and fibroblast cell lines were exposed to bisphosphonates (BPs) and denosumab in different concentrations and durations together with an antiestrogen or corticosteroid. Changes in cell viability, proliferation and migration after exposures were measured. Data were evaluated with hierarchical linear mixed model for repeated measurements.

Results

Bisphosphonate exposure suppressed keratinocyte and fibroblast cell viability, proliferation, and migration in a time‐dependent manner. Combining a corticosteroid or antiestrogen with BPs further increased this negative effect. Denosumab alone had a mild positive effect on keratinocyte and fibroblast growth. When denosumab was combined with a corticosteroid or antiestrogen, cell growth was suppressed.

Conclusions

Our results show that coexisting medications may increase the negative impact of BPs or denosumab on oral mucosal cells.

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.

A Drug Holiday Reduces the Frequency and Severity of Medication-Related Osteonecrosis of the Jaw in a Minipig Model

Treatment of medication-related osteonecrosis of the jaw (MRONJ) is challenging and no clear consensus has been achieved. This study investigated preventive measures recommended for tooth extractions under antiresorptive (AR) treatment and the role of discontinuation of AR therapy to avoid the onset of MRONJ in a minipig model. Thirty-six Göttingen minipigs were divided into four groups. Group 1 (negative control): tooth extractions but no zoledronate (ZOL). Group 2 (positive control): weekly ZOL infusions for 12 weeks followed by tooth extractions without wound management followed by 8 weeks of ZOL treatment. Group 3: weekly ZOL infusions for 12 weeks followed by tooth extractions; surgical wound management (resection of sharp bone edges, mucoperiosteal coverage); and continuation of ZOL infusions for 8 weeks plus antibiotic treatment. Group 4: 12 weeks of ZOL infusions followed by a drug holiday for 6 weeks. Tooth extractions with preventive wound management followed by antibiotic treatment for 8 weeks but no ZOL infusions. Jawbones were subjected to macroscopic, radiological (CT and micro-CT) and histopathological investigations. No clinical cases of MRONJ were observed in the negative group, in the positive control all animals developed MRONJ. Group 3 developed MRONJ in 83% of cases. With a drug holiday, 40% developed MRONJ in areas of tooth extraction. This is the first large animal model that reduces the occurrence of MRONJ following tooth extraction by the implementation of a drug holiday combined with antibiotic prophylaxis and smoothening of sharp bony edges. © 2020 The Authors. Journal of Bone and Mineral Research published by American Society for Bone and Mineral Research..

Update on Equine Odontoclastic Tooth Resorption and Hypercementosis

Equine odontoclastic tooth resorption and hypercementosis (EOTRH) is a progressive, painful disease, affecting incisors, canines, and cheek teeth. Examination findings include gingival inflammation, gingival recession and/or hyperplasia, subgingival swelling, bulbous enlargement of teeth, associated periodontal disease, pathologic tooth fracture, and/or tooth mobility and loss. Current hypotheses include biomechanical stresses and secondary bacterial involvement. Early recognition allows case management, but it is a progressive disease. Owner education is crucial; horses with complete or multiple extractions have a favorable prognosis. Human oral and dental health may be affected by bisphosophonate use; long-term effects of these drugs are currently unknown in horses.

Preventing, identifying, and managing medication-related osteonecrosis of the jaw: a practical guide for nurses and other allied healthcare professionals

BACKGROUND

Medication-related osteonecrosis of the jaw (MRONJ) is an infrequent, but potentially serious, adverse event that can occur after exposure to bone-modifying agents (BMAs; e.g., bisphosphonates, denosumab, and antiangiogenic therapies). BMAs are typically used at higher doses to prevent skeletal-related events in cancer patients and at lower doses for osteoporosis/bone loss. MRONJ can cause significant pain, reduce quality of life, and can be difficult to treat, requiring a multiprofessional approach to care.

METHODS

We reviewed the literature and guidelines to summarize a practical guide on MRONJ for nurses and other allied healthcare professionals.

RESULTS

While there is a risk of MRONJ with BMAs, this should be considered in relation to the benefits of treatment. Nurses and other allied healthcare professionals can play a key role alongside physicians and dentists in assessing MRONJ risk, identifying MRONJ, counseling the patient on the benefit-risk of BMA treatment, preventing MRONJ, and managing the care pathway of these patients. Assessing patients for MRONJ risk factors before starting BMA treatment can guide preventative measures to reduce the risk of MRONJ. Nurses can play a pivotal role in facilitating multiprofessional management of MRONJ by communicating with patients to ensure compliance with preventative measures, and with patients' physicians and dentists to ensure early detection and referral for prompt treatment of MRONJ.

CONCLUSIONS

This review summarizes current evidence on MRONJ and provides practical guidance for nurses, from before BMA treatment is started through to approaches that can be taken to prevent and manage MRONJ in patients receiving BMAs.

Wound closure and alveoplasty after preventive tooth extractions in patients with antiresorptive intake-A randomized pilot trial

OBJECTIVES

To compare success rates between the sub-periosteal prepared (SPP) muco-periosteal flap and the epi-periosteal prepared (EPP) mucosa flap and the feasibility of alveoplasty after surgical tooth extractions in patients undergoing/after antiresorptive treatment.

SUBJECTS

Patients with an indication for preventive tooth extraction undergoing/after antiresorptive treatment were enrolled over a 24-month period in a parallel-group randomized clinical pilot trial and randomly assigned for primary wound closure to either the SPP or the EPP group. The primary outcome was treatment failure 8 weeks after surgery. To assess the feasibility of alveoplasty, necrotic bone changes at the time point of tooth extraction were evaluated.

RESULTS

One hundred and sixty patients were randomized to the SSP (n = 82) or the EPP (n = 78) group. One hundred and fifty-seven patients met the primary endpoint 8 weeks after surgery with five treatment failures for the SPP group (6.3%) and 18 (23.4%) for the EPP group (p = .004). A significant relationship (p < .0001) was observed between symptomatic teeth and non-vital bone found in 54.8% of all biopsies.

CONCLUSIONS

The strong superiority of the muco-periosteal flap as primary wound closure revealed the feasibility and effectiveness of the study. The large number of necrotic biopsies emphasizes the importance of alveoplasty as a preventive measure.

Prevention of medication related osteonecrosis of the jaw after dentoalveolar surgery: An institution's experience

Background

Dentoalveolar surgery is a predisposing factor for medication related osteonecrosis of the jaw (MRONJ). The aim of our study was to evaluate the described surgical procedures to prevent the development of MRONJ after dentoalveolar surgery in patients receiving bisphosphonates.

Material and Methods

In this retrospective study, sixty-three dentoalveolar surgeries were performed on 44 patients taking bisphosphonate in accordance with the treatment procedures we described. The following procedures were applied to patients 1) use of antibiotics 2) performed dentoalveolar surgical procedures 3) fill the socket with leukocyte- and platelet-rich fibrin (L-PRF) 4) post-operative application of low level laser therapy through Nd: YAG laser 5) sutures were removed on post-op 14th day 6) long-term results were evaluated.

Results

Healing of all patients was uneventful. Complete mucosal healing was achieved in all patients at 1 month. There is no failure was observed in long-term follow-up.

Conclusions

Because of the pathophysiology of MRONJ is not fully understood and has many risk factors, definitive protocols on prevention and treatment have not been established yet. Personal risk assessment is required for the prevention and treatment of MRONJ. The described surgical protocol may be considered to reduce the risk of developing MRONJ after dentoalveolar surgery due to its high success rate.

Key words:Tooth extraction, medication related osteonecrosis of the jaw, preventive dentistry, L-PRF, low level laser therapy.

Stress response in periodontal ligament stem cells may contribute to bisphosphonate‑associated osteonecrosis of the jaw: A gene expression array analysis

Gene expression alterations in periodontal ligament stem cells (PDLSCs) during bisphosphonate (BP) usage and the transcriptomic mechanism underlying BP-related osteonecrosis of the jaw have not been fully elucidated. In the present study, human PDLSCs were isolated from adults with no history of periodontal disease, and subsequently incubated and treated with zoledronate on days 3 and 5. Subsequently, PDLSCs from all timepoints were screened using an Affymetrix Gene Expression Array. Limma differential expression analysis was performed on a normalized gene expression matrix, followed by cluster analysis, pathway and network analyses. Overall, 906 genes (352 upregulated and 554 downregulated) exhibited differential expression levels between days 0 and 5, and these were termed slow-response genes. These slow-response genes were enriched in cellular stress response signaling pathways (upregulated genes), as well as proliferation- and ossification-associated signaling pathways (downregulated genes). Furthermore, 168 (day 3 vs. 0) and 105 (day 5 vs. 3) genes were differentially expressed between adjacent timepoints. These genes were also enriched in stress response- and proliferation-associated signaling pathways, but not in ossification-associated signaling pathways. Poly(ADP-ribose) polymerase 1 (PARP1) and CYLD lysine 63 deubiquitinase (CYLD) had the most protein-protein interaction partners among the slow-response genes and were connected with both stress- (e.g. caspase-1) and ossification-associated genes [e.g. secreted phosphoprotein 1 and collagen type I α1 chain (COL1A1)]. BP treatment induced stress response-like transcriptional alterations in PDLSCs, followed by inhibition of proliferation and ossification. These alterations may contribute to the onset of jaw osteonecrosis. PARP1 and CYLD may be two key genes involved in this pathological procedure.

Influence of Bisphosphonates on the Behavior of Osteoblasts Seeded Onto Titanium Discs

Abstract Among other factors, types of bisphosphonates and treatment regimens seem to be strongly associated with the success or failure of installation of osseointegrated implants. This study investigated the influence of two bisphosphonates, sodium alendronate (SA) and zoledronic acid (ZA), on the metabolism of osteoblasts. Human osteoblasts (Saos-2) were seeded onto machined or acid-treated titanium discs previously placed on 24-well plates in complete culture medium. After 24 h, cells were exposed to bisphosphonates at 0.5, 1 or 5 µM for 24 h, 48 h or 7 days. The effects of SA and ZA on osteoblasts were assessed based on the adhesion of these cells to the titanium surfaces by direct fluorescence, cell viability, total protein and collagen synthesis. Alkaline phosphatase activity and mineral nodule deposition by these cells were also evaluated. Data were evaluated by ANOVA and Tukey tests (α=0.05). Decreased adhesion of cells to the titanium discs was observed when exposed to both bisphosphonates; however, this lack of cell adhesion was more evident for ZA-treated cells. In addition, the exposure of osteoblasts to ZA decreased the viability, ALP activity and mineral nodule deposition, which may be related to poor osseointegration after implant installation.

Differences between auto-fluorescence and tetracycline-fluorescence in medication-related osteonecrosis of the jaw-a preclinical proof of concept study in the mini-pig

Objectives

Fluorescence-guided bone surgery is a well-established technique in the treatment of medication-related osteonecrosis of the jaw. No histopathological evidence for bone auto-fluorescence is currently available, and thus, any differences from tetracycline-fluorescence remain unclear. Therefore, the goals of this study were to find out if macroscopic and histological differences occur between the auto- and tetracycline-fluorescence in the delineation of viable and necrotic jawbone in the mini-pig.

Materials and methods

According to the proof of concept, osteonecrosis was provoked in eight Göttingen minipigs. Pigs were divided into two groups (AF group: no fluorochrome label; TF group: tetracycline label). Delineation of necrosis and viable bone was evaluated in vivo and in vitro macro−/microscopically, correlated to fluorescence properties and compared between the two study groups.

Results

No macroscopic and microscopic clinical differences were seen in fluorescence between the AF and TF groups. Macroscopic and microscopic viable bone fluoresced green, whereas necrotic bone showed no or only pale fluorescence in both groups. The auto-fluorescence was attributable to the arrangements and structure of collagen and the cell-filled bone lacunae.

Conclusion

Neither in vivo nor in vitro macroscopically differences are apparent between the auto-fluorescence and the tetracycline-fluorescence of bone. The auto-fluorescence is attributable to the arrangements and structure of collagen and the cell-filled bone lacunae. Tetracycline-fluorescence is a mixture of tetracycline (at the bone edges with increased bone formation) and large components of auto-fluorescence.

Clinical relevance

Because auto-fluorescence is easy to apply, reproducible, and does not rely on the subjective impression of the surgeon, it promises to be an important standardized alternative to tetracycline-labeled MRONJ therapy.

Dental care for patients taking antiresorptive drugs: a literature review

Antiresorptive drugs (ARDs), such as bisphosphonates or denosumab, that prevent bone resorption are widely used in patients with osteoporosis or with cancer that has metastasized to the bones. Although osteonecrosis of the jaw (ONJ) is a well-documented complication of ARD use, the benefits ARDs outweigh the complication. Thus, research has focused on finding ways to prevent or reduce the risk of developing ONJ. Dentists, as part of a multi-professional team, have a critical role in preventing ONJ. However, many dentists tend to hesitate to provide dental care to patients with ONJ, or tend to think that it is a problem to be dealt with by oral surgeons. This review gives an overview of ARD-related ONJ and provides the guidelines for dental care in patients taking ARDs to lower the risk of developing ONJ.

Synthetic Calcium Phosphate Ceramics as a Potential Treatment for Bisphosphonate-Related Osteonecrosis of the Jaw

(1) Background: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is one of the most often seen side effects in patients treated with nitrogen-containing bisphosphonates (BPs), a post-surgical non-healing wound condition. Since calcium phosphate (CP) compounds are able to adsorb zoledronate (ZOL) when used as a drug delivery vehicle, we aimed to verify if these ceramics might have a potential protective effect for soft tissues surrounding surgical osseous wounds. (2) Methods: The chemical reaction between ZOL and CP compounds was evaluated through ultraviolet-visible spectroscopy and elemental analysis. A primary culture of human gingival fibroblasts (HGF) was established as a model to evaluate the cytotoxicity of the association of ZOL (5–500 μM) and of ZOL/biphasic calcium phosphates (BCP). Metabolic activity, cell viability, types of cell death, the cell cycle through, and the migration ability of human gingival fibroblasts were evaluated. (3) Results: ZOL was adsorbed by biphasic calcium phosphate compounds in an aqueous solution. The HGF were sensitive to ZOL toxicity; nevertheless, ZOL/BCP showed a significant protective effect regarding metabolic activity, cell viability, and cell migration. (4) Conclusions: BCP interaction with ZOL reduces or abolishes its toxicity in HGF. This finding represents a potential solution for BRONJ in the case of patients undergoing therapy with ZOL.

Effects of pH alteration on the pathogenesis of medication-related osteonecrosis of the jaw

INTRODUCTION

An acidic environment has been recognized to increase catabolic activities and inhibit osteoblastic deposition, and also exhibited in the pathogenesis of various bone diseases. The aim of the study was to investigate the role of systemic and local pH alteration in the pathogenesis of medication-related osteonecrosis of the jaw (MRONJ).

MATERIAL AND METHODS

Initially, MRONJ was induced in 54 Sprague-Dawley rats via subcutaneous bisphosphonate injections, once a week for 8 weeks. A week prior to bisphosphonate termination, surgical intervention was performed and rats were divided into 3 groups-alkalotic, acidic and control group, wherein each received NaHCO₃, NH₄Cl and normal saline, respectively for 8 weeks. Upon sacrifice, blood was sent for arterial blood pH analysis and their mandibles were subjected to histomorphometric and μCT analyses. ONJ was histologically defined as necrotic bone persisting for eight weeks after surgical intervention.

RESULTS

Each intervention exemplified its expected outcome wherein each group exhibited a borderline alkalotic (7.43 ± 0.05) and acidic state (7.27 ± 37), respectively (P < 0.05). Acidic group showed a higher occurrence of MRONJ (95%) compared to that of alkalotic group (60%) and control (76.9%). Histomorphometric and microstructural evaluation revealed that acidic group presented deteriorated bone architectures with significantly higher necrotic bone fraction, clusters of empty lacunae, N.Oc/B.Pm and lower B.Ar./T.Ar, BV/TV, Tb.Th (P < 0.05). Alkalotic group showed possible protective effects against ONJ versus acidic group, however these trends were not statistically significant.

CONCLUSIONS

An acidic milieu aggravated ONJ development in an animal model. Further investigations are needed to elucidate the exact role of acid-base balance in MRONJ pathogenesis and possible benefits of alkali supplementation for the prevention.

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.

Geranylgeraniol (GGOH) as a Mevalonate Pathway Activator in the Rescue of Bone Cells Treated with Zoledronic Acid: An In Vitro Study

Bisphosphonates (BPs) are the keystone to treat bone disorders. Despite the great benefits of BPs, medication-related osteonecrosis of the jaw (MRONJ) arouse as a potential side effect. Nitrogen-containing BPs (N-BPs) as zoledronate (ZA) act by the inhibition of specific enzymes of the mevalonate pathway resulting in altering protein prenylation which is required for the posttranslational maturation of the small GTP-binding proteins. Geranylgeraniol (GGOH) is an intermediate product in the mevalonate pathway having positive effects on different cell types treated with BPs by salvaging protein prenylation improving cell viability and proliferation in tissue regeneration, thus overcoming N-BP-induced apoptosis. Here, the effect of different concentrations of zoledronate (ZA) on the bone cells has been investigated by cell viability assay, live/dead staining, and western blot to understand if GGOH was able to rescue bone cells and levels of statistical significance were indicated at ^∗P < 0.05, ^∗∗P < 0.01, ^∗∗∗P < 0.001, and ^∗∗∗∗P < 0.0001. Although the high concentration of ZA had significantly decreased the cell viability in the bone cells, GGOH reversed the action of ZA on the cells while at very high concentration; it caused severe reduction in the cell viability. Rap1A, a member of the GTPases family, was expressed in the negative controls but was absent in cells treated with high concentrations of ZA. The addition of GGOH had increased the expression of Rap1A up to a certain limit. The experiments proved that ZA acts directly on the mevalonate pathway and protein prenylation and that GGOH could be applied as a future local therapy to MRONJ.

Effect of ProRoot MTA® and Biodentine® on osteoclastic differentiation and activity of mouse bone marrow macrophages

Objectives

This investigation aimed to assess the differentiation inhibitory effects of ProRoot MTA^® (PMTA) and Biodentine^® (BIOD) on osteoclasts originated from murine bone marrow macrophages (BMMs) and compare these effects with those of alendronate (ALD).

Materials and Methods

Mouse BMMs were cultured to differentiate into osteoclasts with macrophage colony-stimulating factor and receptor activator of NF-κB (RANKL), treated with lipopolysaccharide. After application with PMTA, BIOD, or ALD, cell toxicities were examined using WST-1 assay kit, and RANKL-induced osteoclast differentiation and activities were determined by resorption pit formation assay and tartrate-resistant acid phosphate (TRAP) staining. The mRNA levels of osteoclast activity-related genes were detected with quantitative real time polymerase chain reaction. Expressions of molecular signaling pathways were assessed by western blot. All data were statistically analyzed with one-way ANOVA and Tukey's post-hoc test (p<0.05).

Results

Mouse BMMs applied with PMTA, BIOD, or ALD showed highly reduced levels of TRAP-positive osteoclasts. The BIOD treated specimens suppressed mRNA expressions of cathepsin K, TRAP, and c-Fos. Nonetheless, it showed a lower effect than PMTA or ALD applications. Compared with ALD, PMTA and BIOD decreased RANKL-mediated phosphorylation of ERK1/2 and IκBα.

Conclusions

PMTA and BIOD showed the inhibitory effect on osteoclast differentiation and activities similar to that of ALD through IκB phosphorylation and suppression of ERK signaling pathways.

Molecular and cellular mechanisms for zoledronic acid-loaded magnesium-strontium alloys to inhibit giant cell tumors of bone

Giant Cell Tumors of Bone (GCTB) are benign but aggressive and metastatic tumors. Surgical removal cannot eradicate GCTB due to the subsequent recurrence and osteolysis. Here we developed Zoledronic acid (ZA)-loaded magnesium-strontium (Mg-Sr) alloys that can inhibit GCTB and studied the molecular and cellular mechanisms of such inhibition. We first formed a calcium phosphate (CaP) coating on the Mg-1.5 wt%Sr implants by coprecipitation and then loaded ZA on the CaP coating. We examined the response of GCTB cells to the ZA-loaded alloys. At the cellular level, the alloys not only induced apoptosis and oxidative stress of GCTB cells, and suppressed their resultant pre-osteoclast recruitment, but also inhibited their migration. At the molecular level, the alloys could significantly activate the mitochondrial pathway and inhibit the NF-κB pathway in the GCTB cells. These collectively enable the ZA-loaded alloys to suppress GCTB cell growth and osteolysis, and thus improve our understanding of the materials-induced tumor inhibition. Our study shows that ZA-loaded alloys could be a potential implant in repairing the bone defects after tumor removal in GCTB therapy.

STATEMENT OF SIGNIFICANCE

In clinics, giant cell tumors of bone (GCTB) are removed by surgery. However, the resultant defects in bone still contain aggressive and metastatic GCTB cells that can recruit osteoclasts to damage bone, leading to new GCTB tumor growth and bone damage after tumor surgery. Hence, it is of high demand in developing a material that can not only fill the bone defects as an implant but also inhibit GCTB in the defect area as a therapeutic agent. More importantly, the molecular and cellular mechanism by which such a material inhibits GCTB growth has never been explored. To solve these two problems, we prepared a new biomaterial, the Mg-Sr alloys that were first coated with calcium phosphate and then loaded with a tumor-inhibiting molecule (Zoledronic acid, ZA). Then, by using a variety of molecular and cellular biological assays, we studied how the ZA-loaded alloys induced the death of GCTB cells (derived from patients) and inhibited their growth at the molecular and cellular level. At the cellular level, our results showed that ZA-loaded Mg-Sr alloys not only induced apoptosis and oxidative stress of GCTB cells, and suppressed their induced pre-osteoclast recruitment, but also inhibited their migration. At the molecular level, our data showed that ZA released from the ZA-loaded Mg-Sr alloys could significantly activate the mitochondrial pathway and inhibit the NF-κB pathway in the GCTB cells. Both mechanisms collectively induced GCTB cell death and inhibited GCTB cell growth. This work showed how a biomaterial inhibit tumor growth at the molecular and cellular level, increasing our understanding in the fundamental principle of materials-induced cancer therapy. This work will be interesting to readers in the fields of metallic materials, inorganic materials, biomaterials and cancer therapy.

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.

Influence of pH on osteoclasts treated with zoledronate and alendronate

OBJECTIVES

The objectives of this study were to analyze the effect of pH on the growth and activity of osteoclasts treated with different doses of two nitrogen-containing BPs, zoledronate and alendronate.

MATERIALS AND METHODS

Murine osteoclasts cultured on dentine disks were treated with zoledronate (50 or 500 nM) or alendronate (500 or 5 μM) at two different pH values (7.4 or 7.0). Osteoclasts were counted with transmitted light microscopy, apoptosis/necrosis was studied with flow cytometry and confocal microscopy, and resorption pit number and depth were calculated using reflected light and scanning electron microscopy.

RESULTS

The osteoclast count on dentine disks was significantly (p < 0.001) reduced by zoledronate or alendronate treatment at pH 7.0 in comparison to treatment with the same doses at pH 7.4 and untreated disks (controls). The percentage of apoptotic cells was significantly increased by treatment with 500 nM zoledronate or 5 μM alendronate at pH 7.0 in comparison to the same doses at pH 7.4. The number and depth of resorption pits were significantly lower in disks treated at each BP dose studied than in untreated controls at pH 7.0.

CONCLUSIONS

Zoledronate and alendronate at therapeutic doses have an adverse effect on the viability and resorptive activity of osteoclasts when the local medium pH is reduced.

CLINICAL RELEVANCE

These findings suggest that periodontal or peri-implant oral cavity infection may be a key trigger of the cascade of events that lead to BRONJ.

Bisphosphonate Modulation of the Gene Expression of Different Markers Involved in Osteoblast Physiology: Possible Implications in Bisphosphonate-Related Osteonecrosis of the Jaw

The aim of the present study was to elucidate the role of osteoblasts in bisphosphonates-related osteonecrosis of the jaw (BRONJ). The specific objective was to evaluate the effect on osteoblasts of two nitrogen-containing BPs (zoledronate and alendronate) and one non-nitrogen-containing BP (clodronate) by analyzing modulations in their expression of genes essential for osteoblast physiology. Real-time polymerase chain reaction (RT-PCR) was used to study the effects of zoledronate, alendronate, and clodronate at doses of 10-5, 10-7, or 10-9 M on the expression of Runx-2, OSX, ALP, OSC, OPG, RANKL, Col-I, BMP-2, BMP-7, TGF-β1, VEGF, TGF-βR1, TGF-βR2, and TGF-βR3 by primary human osteoblasts (HOBs) and MG-63 osteosarcoma cells. Expression of these markers was found to be dose-dependent, with no substantive differences between these cell lines. In general, results demonstrated a significant increase in TFG-β1, TGF-βR1, TGF-βR2, TGF-βR3, and VEGF expressions and a significant reduction in RUNX-2, Col-1, OSX, OSC, BMP-2, BMP-7, ALP, and RANKL expressions, while OPG expression varied according to the dose and cell line. The results of this in vitro study of HOBS and MG-63 cell lines indicate that low BP doses can significantly affect the expression of genes essential for osteoblast growth and differentiation and of genes involved in regulating osteoblast-osteoclast interaction, possibly by increasing TGF-β1 production. These findings suggest that osteoblasts may play an important role in BRONJ development, without ruling out other factors.

Effects of an oral bisphosphonate and three intravenous bisphosphonates on several cell types in vitro

OBJECTIVE

To analyze the influence of an oral bisphosphonate and compare the potency to intravenous bisphosphonates on various cell types as regards the rarity of bisphosphonate-associated osteonecrosis of the jaw (BP-ONJ) caused by oral bisphosphonate.

MATERIALS AND METHODS

A viability assay (MTT), a migration assay (Boyden chamber), and an apoptosis assay (Caspase-Glo® 3/7) were performed to analyze the effect of bisphosphonates on human fibroblasts, umbilical vein endothelial cells (HUVEC), and osteoblasts.

RESULTS

Alendronate and intravenous bisphosphonates suppressed cell viability and migration, and induced apoptosis in all tested cell types. Alendronate had a greater impact than ibandronate on the characteristics in fibroblasts and osteoblasts but not as strong as zoledronate.

CONCLUSIONS

The incidence of BP-ONJ in oral bisphosphonate treatment is reported to be much lower than that in intravenous bisphosphonates. However, the influences of alendronate on human cells were at least as strong as ibandronate, although it was lower than zoledronate.

CLINICAL RELEVANCE

Alendronate showed strong enough effects to suppress human somatic cells and was comparable to certain intravenous bisphosphonates in potency. This study suggests that the lower incidence of BP-ONJ in alendronate treatment is not originated by its potency, but might be due to the low bioavailability of alendronate, lower dosing on a daily basis, and having no additional therapies.

In vivo effects of geranylgeraniol on the development of bisphosphonate-related osteonecrosis of the jaws

BACKGROUND

Bisphosphonate-related osteonecrosis of the jaws (BRONJ) is a complication of the bisphosphonate (BP) treatment and its pathopysiology is still not fully understood. The existing preventive and treatment options require updates and more attention. Geranylgeraniol (GGOH) so far demonstrated an increased activity and viability of the cells previously treated with zoledronic acid (ZA). The aim of this study was to evaluate the in vivo effects of GGOH on the development of BRONJ.

MATERIALS AND METHODS

A total of 30 male Wistar rats were included in the study, divided into three groups: two experimental groups (EG1 and EG2) and a control group (CG). Rats from EG1 and EG2 were treated with 0,06 mg/kg ZA ip weekly in a duration of five weeks, while CG received saline ip. On the third week all animals underwent extraction of the lower right first molars. The rats from EG2 received a local solution of GGOH in concentration of 5 mM in the socket every day after the tooth extraction. The analyses included clinical evaluation on the wound healing and pathohistological evaluation for presence and level of osteonecrosis.

RESULTS

EG2 showed significantly improved wound healing and tissue proliferation, when compared to EG1. EG2 significantly differed from EG1 and CG (p<0,05) for the presence of microscopical osteonecrosis (80% vs 22,2% vs 0%). Regarding to the number of empty lacunes without osteocytes and the level of necrosis, all groups demonstrated significant differences.

CONCLUSION

Geranylgeraniol in a form of local solution may be a promising option for prevention and treatment of BRONJ.

A multicenter retrospective study of the risk factors associated with medication-related osteonecrosis of the jaw after tooth extraction in patients receiving oral bisphosphonate therapy: can primary wound closure and a drug holiday really prevent MRONJ?

Root amputation, extraction of a single tooth, bone loss or severe tooth mobility, and an unclosed wound were significantly associated with increased risk of developing medication-related osteonecrosis of the jaw (MRONJ). We recommend a minimally traumatic extraction technique, removal of any bone edges, and mucosal wound closure as standard procedures in patients receiving bisphosphonates.

INTRODUCTION

Osteonecrosis of the jaws can occur following tooth extraction in patients receiving bisphosphonate drugs. Various strategies for minimizing the risk of MRONJ have been advanced, but no studies have comprehensively analyzed the efficacy of factors such as primary wound closure, demographics, and drug holidays in reducing its incidence. The purpose of this study was to retrospectively investigate the relationships between these various risk factors after tooth extraction in patients receiving oral bisphosphonate therapy.

METHODS

Risk factors for MRONJ after tooth extraction were evaluated using univariate and multivariate analysis. All patients were investigated with regard to demographics; type and duration of oral bisphosphonate use; whether they underwent a discontinuation of oral bisphosphonates before tooth extraction (drug holiday), and the duration of such discontinuation; and whether any additional surgical procedures (e.g., incision, removal of bone edges, root amputation) were performed.

RESULTS

We found that root amputation (OR = 6.64), extraction of a single tooth (OR = 3.70), bone loss or severe tooth mobility (OR = 3.60), and an unclosed wound (OR = 2.51) were significantly associated with increased risk of developing MRONJ.

CONCLUSIONS

We recommend a minimally traumatic extraction technique, removal of any bone edges, and mucosal wound closure as standard procedures in patients receiving bisphosphonates. We find no evidence supporting the efficacy of a pre-extraction short-term drug holiday from oral bisphosphonates in reducing the risk of MRONJ.

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.

Influence of bisphosphonates on the adherence and metabolism of epithelial cells and gingival fibroblasts to titanium surfaces

OBJECTIVES

To evaluate the effects of sodium alendronate (SA) and zoledronic acid (ZA), on the adhesion and metabolism of epithelial cells and gingival fibroblasts to titanium surfaces considering cell functions related to an effective mucosal barrier around the implant.

MATERIALS AND METHODS

Cells were seeded onto titanium discs and incubated for 24 h. Then, serum-free DMEM containing selected bisphosphonates (0, 0.5, 1, or 5 μM) was added for 24 and 48 h. Factors related to the achievement of an effective mechanical and immunological barrier-cell adhesion, viability, collagen epidermal growth factor, and immunoglobulin synthesis-were evaluated. Data were analyzed by Kruskal-Wallis and Mann-Whitney tests as well as by ANOVA and Tukey's tests, (α = 0.05).

RESULTS

The presence of bisphosphonates culminated in lower cell adhesion to the titanium discs, particularly for SA at 5 μM (40%) and ZA at all concentrations (from 30 to 50%, according to increased concentrations). Reduced cell viability occurred after exposing these cells to ZA (40%); however, only 5 μM SA-treated cells had decreased viability (30%). Reduced synthesis of growth factors and collagen was observed when cells were reated with ZA (20 and 40%, respectively), while about 70% of IgG synthesis was enhanced.

CONCLUSION

Bisphosphonates negatively affected the adhesion and metabolism of oral mucosal cells, and this effect was related to the type of bisphosphonate as well as to concentration and period of treatment.

CLINICAL RELEVANCE

The negative effects of bisphosphonates on oral mucosal cells can hamper the formation of an effective biological seal in osseointegrated implants.

Role of microbiological culture and polymerase chain reaction (PCR) of actinomyces in medication-related osteonecrosis of the jaw (MRONJ)

We hypothesized that local infection plays a critical role in the pathogenesis of medication-related osteonecrosis of the jaw (MRONJ). Recent developments in molecular methods have revolutionized new approaches for the rapid detection of microorganisms including those difficult to culture. The aim of our study is to identify the bacterial profiles in MRONJ by microbiological culture and polymerase chain reactions (PCR). A retrospective analysis was performed on MRONJ patients from 2008 to 2014. The bacterial profile from MRONJ bone samples was determined using microbiological culture and PCR. Ninety five patients fulfilled the inclusion criteria with mean age of 69.85 ± 8.71 years. A female predilection was detected. The mandible was more commonly affected than maxilla. Tooth extraction was the frequent triggering factor. Breast cancer was the primary cause for administration and intravenous bisphosphonates were the most commonly administrated antiresorptive drugs. The majority of patients were classified as stage 2. Posterior teeth were most commonly affected. Based on bone culture results, the most common microorganism were both actinomyces and mixed flora. PCR confirmed the presence of actinomyces in 55 patients. Our data suggest that PCR might be an innovative method for detection of microorganisms difficult to culture using traditional microbiological techniques.

Osteonecrosis

Younger patients are affected more often by osteonecrosis than by osteoarthritis, and osteonecrosis has significantly greater long-term morbidity.

Corticosteroids are the most common cause of nontraumatic osteonecrosis.

The femoral head is the most common site of osteonecrosis.

In rare instances, osteonecrosis of the jaw has been associated with bisphosphonate exposure. This phenomenon is more common with repeated intravenous infusions of bisphosphonates.

Case reports of osteonecrosis of the jaw in association with other medications, such as denosumab, have been reported.

The final common pathway in the pathogenesis of osteonecrosis is disruption of blood supply to a segment of bone.

Abnormalities in lipid metabolism, bone homeostasis, regulation of apoptosis, coagulopathies, innate immunity, and oxidative stress may play a role in the pathogenesis of osteonecrosis.

Epigenetics may alter the predisposition to develop osteonecrosis.

MRI is currently the optimal test for early diagnosis and identification of the extent of osteonecrosis.

Nonsurgical treatment of osteonecrosis does not change the natural history of the disease.

Although surgical treatment of femoral head osteonecrosis has many variations, most symptomatic patients eventually require total hip arthroplasty.

Knowledge of risk factors and early detection are crucial to the successful management of osteonecrosis.

Because of the lack of successful treatment options, new modes of management focus on the prevention of osteonecrosis.