The effects of adjunctive parathyroid hormone injection on bisphosphonate-related osteonecrosis of the jaws: an animal study

Evaluation of Methenolone Enanthate Efficacy in Preventing MRONJ: A Randomized Trial on Rats

BACKGROUND

It is well-known that oral surgical procedures pose a high risk for medication-related osteonecrosis of the jaw in patients taking bisphosphonates. Although some position papers and guidelines have been published with regard to its treatment, few studies have investigated prevention methods. This study investigates the effectiveness of methenolone enanthate, an anabolic steroid, for the prevention of medication-related osteonecrosis of the jaw.

METHODS

Thirty-six Wistar rats were divided into three groups. Two experimental groups, Z and ZM, took zoledronic acid for 6 weeks prior to extraction of the left maxillary first molar. The Group ZM also was given methenolone enanthate continuously for 1 week before and 4 weeks after the extraction. The control group was not given any medication. The rats were euthanized 5 weeks after extraction. The extraction socket was evaluated clinically for bone exposure and histologically for inflammation, hyperemia, collagen fibers, epithelialization, number of osteoclasts, and empty lacunae.

RESULTS

Six rats died during the experimental research. The bone exposure rate, mean numbers of attached osteoclasts (in 40× magnification), and empty lacunae (in 100× magnification) were 0%, 4%, and 0.8% in Group C; 75%, 1%, and 8% in Group Z; and 10%, 2.1%, and 3% in Group ZM, respectively. Significant differences exist between all groups regarding the number of empty lacunae. There were significant differences between Group C/ZM and Group Z in terms of bone exposure rate, inflammation, hyperemia, collagen fiber organization, and epithelialization.

CONCLUSION

In our tested preclinical model, methenolone enanthate has shown potential for preventing medication-related osteonecrosis of the jaw.

Rodents as an animal model for studying tooth extraction-related medication-related osteonecrosis of the jaw: assessment of outcomes

OBJECTIVE

To assess the outcomes of several rodent animal models for studying tooth extraction-related medication-related osteonecrosis of the jaw (MRONJ).

DESIGN

After a search of the databases, 2004 articles were located, and 118 corroborated the inclusion factors (in vivo studies in rodents evaluating tooth extraction as a risk factor for the development of MRONJ).

RESULTS

Numerous studies attempting to establish an optimal protocol to induce MRONJ were found. Zoledronic acid (ZA) was the most used drug, followed by alendronate (ALN). Even when ZA did not lead to the development of MRONJ, its effect compromised the homeostasis of the bone and soft tissue. The association of other risk factors (dexamethasone, diabetes, and tooth-related inflammatory dental disease) besides tooth extraction also played a role in the development of MRONJ. In addition, studies demonstrated a relationship between cumulative dose and MRONJ.

CONCLUSIONS

Both ZA and ALN can lead to MRONJ in rodents when equivalent human doses (in osteoporosis or cancer treatment) are used. Local oral risk factors and tooth-related inflammatory dental disease increase the incidence of MRONJ in a tooth extraction-related rodent model.

Ozone Improved Bone Dynamic of Female Rats Using Zoledronate

The aim of this study was to analyze the effect of ozone (OZN) therapy on the dynamics of bone tissue in ovariectomized rats treated with zoledronic acid (ZOL). Female Wistar rats aged 6 months (n = 110) were subjected to bilateral ovariectomy (OVX). At month 3 post-OVX, 10 animals were euthanized to characterize the bone tissue architecture using microtomography (micro-CT). The remaining animals were divided into two groups: ZOL group, administered with ZOL (100 μg/kg body weight); saline (SAL) group (0.45 mL of SAL solution), both for 28 days. At month 3 post-treatment, 10 animals from each group were euthanized to characterize the bone architecture using micro-CT. The remaining animals were divided into the following groups: ZOL (n = 20), ZOL + OZN (n = 20); SAL (n = 20), and SAL + OZN (n = 20). The animals in ZOL + OZN and SAL + OZN groups were intraperitoneally administered with OZN (0.7 mg/kg body weight) once every 2 days. On days 30 and 60, six animals from each group were euthanized for analysis and structural characterization of bones in the femoral head and spine. Some samples of the femoral neck were subjected to biomechanical tests, while some samples were analyzed under a laser confocal microscope. The other samples collected from the femoral neck and spine were analyzed for area of neoformed bone and used for performing inflammatory cell and osteocyte counts. Data were submitted to statistical analysis considering a significance level of p < 0.05. Bone volume percentage and osteocyte and inflammatory cell counts were upregulated in the femoral head region of the ZOL + OZN group. Biomechanical analysis of the femoral neck revealed that the modulus of elasticity was similar between the ZOL and ZOL + OZN groups but differed significantly between the SAL and SAL + OZN groups. The positive areas for calcein and alizarin in the ZOL and ZOL + OZN groups were higher than those in the SAL and SAL + OZN groups. This suggested a positive synergistic effect of OZN and ZOL on the maintenance of bone mass and restoration of bone tissue vitality in ovariectomized rats.

[The recombinant human parathyroid hormone, teriparatide as an alternative remedy for the medication-related osteonecrosis of the jaw]

In developed countries, osteoporosis is one of the most common debilitating conditions in the population over the age of 50. Unfortunately, the pathomechanism of the disease is still not fully understood. Nowadays, the administration of antiresorptive drugs blocking osteoclastic activity is the most commonly used medication to slow down the speed of the bone loss. One of the uncommon side effects of such drugs is the medication-related osteonecrosis of the jaw (MRONJ). Recently, a number of alternative therapeutic approaches has been tested and published, amongst them the recombinant human parathyroid hormone (rhPTH, teriparatide) use, which is turning into a promising treatment modality. According to certain meta-analyses, its pharmacological effect on increasing bone mineral density and controlling pathological vertebral fractures is superior to antiresorptive drugs; however, the so-called "off-label" application of teriparatide remains controversial. As intermittent administration of teriparatide stimulates bone formation, several animal and clinical studies indicated that systemic application of teriparatide shortened fracture healing time and improved quality of the callus and the newly formed bone. Furthermore, recently several clinical studies showed the beneficial effect of the intermittent rhPTH administration in the management of MRONJ. This article reviews the history of the anabolic effect of the low-dose rhPTH discovery, provides evidence-based data from animal and human studies, summarizes its biological mechanisms and the clinical benefits of the anabolic therapy and also their possible role in the management of MRONJ. The majority of the clinical data indicates that, in the case of therapy-resistant osteonecrosis, it may be worthwhile to apply short-term intermittent teriparatide therapy. Notwithstanding, more randomized clinical trials are necessary in order to confirm the efficacy and the safety of the use of teriparatide in the treatment of MRONJ. Orv Hetil. 2023; 164(36): 1406-1415.

Medication-related osteonecrosis of the jaw using periodontitis-induced rat before tooth extraction

OBJECTIVE

This study aimed to investigate the occurrence of medication-related osteonecrosis of the jaw (MRONJ) after tooth extraction due to periodontitis in ovariectomized rats.

METHODS

Twenty-four osteoporosis-induced rats were administered with zoledronic acid (ZA; ZA group) or saline (CONT group). In both groups, tooth extraction was performed after inducing periodontitis, and all animals were sacrificed 8-week after tooth extraction.

RESULTS

Micro-CT of the tibia showed that the bone volume fraction, bone surface density, trabecular number, and bone mineral density were significantly higher in the ZA group than in the CONT group. Histologically, the proliferative zone on the growth plate was thicker in the ZA group than in the CONT group. Micro-CT of the extraction sites revealed that the bone volume fraction was significantly higher in the ZA group than in the CONT group. Radiologically, the ZA group showed partial healing and delayed healing. Histological analysis revealed normal bone healing status with completely healed epithelium in the extraction sites of the CONT group, whereas abnormal empty osteocytes in the necrotic bone and inflammatory infiltration were observed in the ZA group.

CONCLUSION

The incidence of MRONJ increased in the rats administered with ZA.

Histopathological assessment of the preventive effect of leukocyte-platelet-rich fibrin on bisphosphonate-related osteonecrosis of the jaw following dental extraction: An animal study

Background

Leukocyte- and platelet-rich fibrin (L-PRF) could be considered a preventive measure in Bisphosphonate-Related Osteonecrosis of the Jaw (BRONJ). The present experiment aimed to assess the preventive effects of L-PRF on osteonecrosis of the jaw in rats.

Methods

In this interventional animal study with a split-mouth design, 28 rats were randomly allocated to saline (negative control), bisphosphonate (positive control), and Bis + L-PRF (case) groups. Bilateral extraction of maxillary molar teeth was performed followed by random application of L-PRF to one of the extraction sockets treated with Zoledronic acid for four weeks. Clinical occurrence of BRONJ and histopathologic evaluations were done, and data were subjected to the Kruskal-Wallis test, Mann-Whitney U test and exact Fisher test performed using SPSS 25. The significance level was set at 0.05.

Results

The application of L-PRF resulted in a 41.67% reduction in osteonecrosis centers and the number of osteoclast cells. Also, Kruskal Wallis test results showed a significant difference among the three groups regarding the frequency distribution of inflammation severity. However, no significant difference was detected regarding the frequency distribution of the blood vessels (Kruskal Wallis test, P-value = 0.649).

Conclusion

It could be inferred that possible preventive effects on the clinical occurrence of osteonecrosis could be expected from the application of L-PRF.

Intermittent parathyroid hormone enhances the healing of medication-related osteonecrosis of the jaw lesions in rice rats

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse event in patients treated with antiresorptives. Management of MRONJ is challenging, and no non-antibiotic, established medical treatment exists. Intermittent parathyroid hormone (iPTH) has been used off-label to treat MRONJ with favorable results. However, its medical efficacy has rarely been substantiated in clinical or preclinical experiments. Using a validated rice rat, infection-based model of MRONJ, we evaluated the effects of iPTH on established MRONJ. We hypothesize that iPTH contributes to MRONJ resolution by enhancing alveolar bone turnover and healing oral soft tissues. Eighty-four rice rats began a standard rodent chow diet at age 4 weeks to induce localized periodontitis. Rats were simultaneously randomized to receive saline (vehicle, VEH) or zoledronic acid (ZOL, 80 μg/kg IV) every 4 weeks. Oral exams were conducted bi-weekly to assign a gross quadrant grade (GQG, 0-4) to evaluate any lesion at the lingual aspect of the interdental space between maxillary molar (M2) and M3. 14 of 20 VEH-treated rice rats (70%) developed maxillary localized periodontitis with GQG 2-3 after 30 ± 10 weeks of saline. Additionally, 40 of 64 ZOL-treated rice rats with periodontitis developed MRONJ-like lesions after 30 ± 10 weeks of ZOL treatment. Rice rats with localized periodontitis or MRONJ-like lesions were treated with saline or iPTH (40 μg/kg) subcutaneously (SC) 3 times/week For 6 weeks until euthanasia. We found that iPTH -treated ZOL rats had a lower prevalence of MRONJ (p < 0.001), with lower severity extent of oral lesions (p = 0.003) and percentage of empty osteocyte lacunae (p < 0.001). ZOL rats treated with iPTH displayed a higher osteoblast surface (p < 0.001), more osteoblasts (p < 0.001), higher osteoclast surface (p < 0.001) and more osteoclasts (p = 0.002) at alveolar bone surfaces than ZOL/VEH rats. Greater gingival epithelial thickness and epithelial cell proliferation rate was found in the oral mucosa and gingiva of ZOL/PTH rats than in ZOL/VEH rats (p < 0.001). Our data suggest that iPTH is an efficacious non-operative medicinal therapy that accelerates oral healing and enhances the resolution of MRONJ lesions in ZOL-treated rice rats.

Radiographic changes of mandibular cortical bone in bisphosphonate drug holiday

Objectives

There have been few studies to date on the residual effect of bisphosphonate. This study investigated the radiographic changes of mandibular cortical thickness upon bisphosphonate drug holiday.

Materials and Methods

This retrospective study includes 36 patients diagnosed with MRONJ (medication-related osteonecrosis of the jaw) at Ajou University Dental Hospital in 2010-2021. All patients stopped taking bisphosphonate under consultation with the prescribing physicians. Panoramic radiographs were taken at the start of discontinuation (T₀), 12 months after (T₁), and 18 months after (T₂) discontinuation of bisphosphonate, respectively. Mental index and panoramic mandibular index were calculated using Ledgerton’s method. Paired t-tests were used to analyze differences over time.

Results

The difference in indices (mental index and panoramic mandibular index) between T₀ and T₁ was not statistically significant (paired t-test, P>0.05). However, the difference in these indices between T₁ and T₂ was statistically significant (paired t-test, P<0.05).

Conclusion

The cortical thickness of the mandible decreased in the late stage (after 18 months) as observed by panoramic radiograph.

American Association of Oral and Maxillofacial Surgeons' Position Paper on Medication-Related Osteonecrosis of the Jaws-2022 Update

Strategies for management of patients with, or at risk for, medication-related osteonecrosis of the jaws (MRONJ) - formerly referred to as bisphosphonate-related osteonecrosis of the jaws (BRONJ)-were set forth in the American Association of Oral and Maxillofacial Surgeons (AAOMS) position papers in 2007, 2009 and 2014. The position papers were developed by a committee appointed by the AAOMS Board of Trustees and comprising clinicians with extensive experience in caring for these patients, as well as clinical and basic science researchers. The knowledge base and experience in addressing MRONJ continues to evolve and expand, necessitating modifications and refinements to the previous position papers. Three members of the AAOMS Committee on Oral, Head, and Neck Oncologic and Reconstructive Surgery (COHNORS) and three authors of the 2014 position paper were appointed to serve as a working group to analyze the current literature and revise the guidance as indicated to reflect current knowledge in this field. This update contains revisions to diagnosis and management strategies and highlights the current research status. AAOMS maintains that it is vitally important for this information to be disseminated to other relevant healthcare professionals and organizations.

Osteonecrosis of the Jaw and Antiresorptive Agents in Benign and Malignant Diseases: A Critical Review Organized by the ECTS

CONTEXT

Antiresorptive therapy significantly reduces fracture risk in patients with benign bone disease and skeletal-related events (SREs) in patients with bone metastases (BM). Osteonecrosis of the jaw (ONJ) is a rare but severe condition manifested as necrotic bone lesion or lesions of the jaws. ONJ has been linked to the use of potent antiresorptive agents, termed medication-related ONJ (MRONJ).

OBJECTIVE

We aimed to identify the differences various aspects of MRONJ among distinct patient categories and provide recommendations on how to mitigate the risk and optimally manage MRONJ in each of them.

METHODS

A working group of the European Calcified Tissue Society (ECTS) and 2 experts performed an updated detailed review of existing literature on MRONJ incidence, characteristics, and treatment applied in bone diseases with variable severity of skeletal insult, ranging from osteoporosis to prevention of cancer treatment-induced bone loss and SREs in cancer patients with BM.

RESULTS

The risk for MRONJ is much higher in patients with advanced malignancies compared to those with benign bone diseases because of the higher doses and more frequent administration of antiresorptive agents in individuals with compromised general health, along with coadministration of other medications that predispose to MRONJ. The overall risk for MRONJ is considerably lower than the benefits in all categories of patients.

CONCLUSION

The risk for MRONJ largely depends on the underlying bone disease and the relevant antiresorptive regimen applied. Physicians and dentists should keep in mind that the benefits of antiresorptive therapy far outweigh the risk for MRONJ development.

Current Trends in Adjuvant Therapies for Medication-Related Osteonecrosis of the Jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a refractory disease, and a standard protocol for its treatment has not yet been established. In addition, owing to the old age of MRONJ patients and various complications, treatment goals focus on relieving the symptoms and improving the quality of life. For this reason, different treatments such as conservative, surgical, and adjunctive treatments have been attempted. In particular, adjunctive treatment, which is effective for promoting healing and reducing recurrence, is gaining increasing interest, and several studies and clinical trials related to it have been published. Representative adjuvant therapies include teriparatide, recombinant human bone morphogenetic protein-2, hyperbaric oxygen, photobiomodulation and platelet concentrates. All have generally shown beneficial effects; however, no standard protocol for adjunctive treatment exists. Therefore, in this literature review, we briefly summarized the different adjuvant therapies and reviewed clinical reports to help decide whether to use adjuvant therapies in treating patients with MRONJ.

Preclinical models of medication-related osteonecrosis of the jaw (MRONJ)

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially severe adverse event affecting patients with cancer and patients with osteoporosis who have been treated with powerful antiresorptives (pARs) or angiogenesis inhibitors (AgIs). pARs, including nitrogen-containing bisphosphonates (N-BPs; e.g., zoledronic acid, alendronate) and anti-RANKL antibodies (e.g., denosumab), are used to manage bone metastases in patients with cancer or to prevent fragility fractures in patients with osteoporosis. Though significant advances have been made in understanding MRONJ, its pathophysiology is still not fully elucidated. Multiple species have been used in preclinical MRONJ research, including the rat, mouse, rice rat, rabbit, dog, sheep, and pig. Animal research has contributed immensely to advancing the MRONJ field, particularly, but not limited to, in developing models and investigating risk factors that were first observed in humans. MRONJ models have been developed using clinically relevant doses of systemic risk factors, like N-BPs, anti-RANKL antibodies, or AgIs. Specific local oral risk factors first noted in humans, including tooth extraction and inflammatory dental disease (e.g., periodontitis, periapical infection, etc.), were then added. Research in rodents, particularly the rat, and, to some extent, the mouse, across multiple laboratories, has contributed to establishing multiple relevant and complementary preclinical models. Models in larger species produced accurate clinical and histopathologic outcomes suggesting a potential role for confirming specific crucial findings from rodent research. We view the current state of animal models for MRONJ as good. The rodent models are now reliable enough to produce large numbers of MRONJ cases that could be applied in experiments testing treatment modalities. The course of MRONJ, including stage 0 MRONJ, is characterized well enough that basic studies of the molecular or enzyme-level findings in different MRONJ stages are possible. This review provides a current overview of the existing models of MRONJ, their more significant features and findings, and important instances of their application in preclinical research.

Effect and timing of parathyroid hormone analog administration for preventing medication-related osteonecrosis of the jaws in a murine model

The aim of this study was to investigate the effect and timing of recombinant human parathyroid hormone analog (PTH) administration for preventing medication-related osteonecrosis of the jaws (MRONJ) using a murine model. After standardized MRONJ induction using zoledronic acid and dexamethasone injections, 48 female Sprague-Dawley rats were divided into four groups according to the timing of PTH administration before or after dental extraction. Rats were euthanized 3 weeks after dental extraction, followed by clinical and histologic analyses. No clinical improvements were observed in the preoperative and postoperative PTH groups, compared to controls (p = 0.638 and 0.496, respectively). However, on histological analysis, the number of empty lacunae reduced significantly, and the number of blood vessels increased in the preoperative PTH group (p = 0.004 and 0.002, respectively). The postoperative PTH group did not show significant differences for empty lacunae and blood vessels compared to controls (p = 0.075 and 0.194, respectively). The reduction in the empty lacunae and the increase in the blood vessels in the preoperative PTH group were significant compared to other groups, suggesting more viable bone tissue in this group. In perspective, preoperative PTH use may represent a better prophylactic regimen for preventing the occurrence of MRONJ after traumatic dental or surgical procedures, especially in patients with a history of long-term bisphosphonate administration or at high risk of developing MRONJ. However, the findings should be proven in further studies on other animals followed by clinical trials.

The Use of Photodynamic Therapy on Medication-Related Osteonecrosis of the Jaws: Animal Study

Background/Aim: Bisphosphonate-related osteonecrosis of the jaw (BRONJ) was first introduced in 2003 and its scope was expanded by the name medication-related osteonecrosis of the jaw (MRONJ), since 2014. This study aimed to evaluate the effects of photodynamic therapy (FDT) on tissue samples by histopathological and histomorphometric examination and serum TRACP-5b (Tartrateresistant acid phosphatase-5b) measurement in rats.

Material and Methods: 24 Sprague-Dawley male rats were divided into 3 groups comprising 8 animals. Zoledronic acid was administered to groups 1 and 2 and 0.9% sodium chloride was administered to group 3 intraperitoneally. After the injections were completed, dental extractions were performed. Photodynamic therapy was applied to group 2, three times a weekfor the two weeks after the extraction. In the 16th week, sacrification was performed. Rats were undergone histopathologic and histomorphometric evaluations.

Results: Photodynamic therapy has led to a decrease in epithelial opening and inflammation and an increase in the formation of new bone. Serum TRACP-5b values were shown to decrease significantly in the presence of osteonecrosis.

Conclusions: PDT was shown to be useful in reducing MRONJ risk in rats. As a serum biomarker, Serum TRACP-5b could be a valuable marker. Additional studies should confirm the findings.

Effects of pre-extraction intermittent PTH administration on extraction socket healing in bisphosphonate administered ovariectomized rats

The purpose of this study was to investigate the effect of administering intermittent parathyroid hormone (iPTH) before tooth extraction versus after tooth extraction on the risk of developing MRONJ in experimental animal model. Twenty-five ovariectomized rats received 6 weeks of bisphosphonate therapy. They were classified into 3 groups, based on the timing of the medication, as Control, Pre-PTH and Post-PTH groups. For Control group, normal saline was administered before and after tooth extraction. iPTH was administered during 4 weeks before tooth extraction for Pre-PTH group and after tooth extraction for Post-PTH group. The animals were euthanized 8 weeks after tooth extraction. Macroscopic, histological, micro-computed tomography (micro-CT), and histomorphometric examinations were conducted. The incidences of impaired healing were 11.11% both in Pre-PTH and Post-PTH groups, which was lower than the Control group (42.86%). Bone healing in the extraction socket, based on micro-CT and histomorphometry evaluations, was best in Post-PTH and worst in Control group. The Pre-PTH group showed moderate healing pattern. Despite of limitations in this study, the authors identified Pre-PTH group seems to have positive effect on extraction socket healing. With regard to timing, administering iPTH after tooth extraction was superior to applying it before tooth extraction.

Pathogenesis and multidisciplinary management of medication-related osteonecrosis of the jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a serious side effect of bone-modifying agents and inhibits angiogenesis agents. Although the pathogenesis of MRONJ is not entirely clear, multiple factors may be involved in specific microenvironments. The TGF-β1 signalling pathway may have a key role in the development of MRONJ. According to the clinical stage, multiple variables should be considered when selecting the most appropriate treatment. Therefore, the prevention and management of treatment of MRONJ should be conducted in patient-centred multidisciplinary team collaborative networks with oncologists, dentists and dental specialists. This would comprise a closed responsibility treatment loop with all benefits directed to the patient. Thus, in the present review, we aimed to summarise the pathogenesis, risk factors, imaging features, clinical staging, therapeutic methods, prevention and treatment strategies associated with MRONJ, which may provide a reference that can inform preventive strategies and improve the quality of life for patients in the future.

The effect of melatonin on prevention of bisphosphonate-related osteonecrosis of the jaw: an animal study in rats

Objectives

Melatonin induces human stem cells, converts pre-osteoblasts to mature osteoblasts, and reduces the duration of this transition. However, melatonin itself prevents activation of osteoclasts. Here, we evaluate the role of melatonin in prevention of bisphosphonate-related osteonecrosis of the jaw.

Materials and Methods

In this experimental-interventional study, 30 rats were evaluated in 3 groups. The first and second groups received saline and zoledronic acid, respectively, for 4 weeks and the third group received 4 weeks of zoledronic acid and 3 weeks of melatonin simultaneously. First-right-maxillary-molar extraction was performed for all animals, which were sacrificed after 4 weeks of recovery. The extraction sockets were examined histologically for the presence of osteonecrosis, number of osteoclasts and fibroblasts, severity of inflammation, and vascularization. Data were analyzed by chi-square, one-way ANOVA, Tukey, Kruskal–Wallis and Fisher’s exact statistical tests (α=0.05).

Results

Osteonecrosis was observed in 20%, 90%, and 70% of the first, second and third groups, respectively (P=0.008). The lowest number of osteoclasts and fibroblasts was seen in the third group.

Conclusion

Melatonin may effectively prevent some undesirable side effects of bisphosphonates. However, further studies are required to confirm the results of this study.

The role, efficacy and outcome measures for teriparatide use in the management of medication-related osteonecrosis of the jaw

Medication-related osteonecrosis of the jaw (MRONJ) is a complex disease which can be associated with multiple morbidities and is challenging to treat. This review evaluates the literature on the role and efficacy of teriparatide (TPTD) as a treatment for MRONJ. The clinical, radiological, histopathological and serological parameters used to assess treatment response have been described. Electronic databases were searched to retrieve articles (April 2005 and April 2020) based on strict inclusion criteria. Seventeen articles were included in this review. Of the 91 patients treated; only six received TPTD as a standalone treatment. There were significant variations in defining treatment outcomes and measuring treatment response. The longest follow-up period was 26 months, and 12 studies failed to report follow-up. The overall quality of evidence is weak with potential for a high risk of bias, making it difficult to determine the efficacy of TPTD and its long-term effects. However, TPTD may play a role in the treatment of intractable MRONJ in osteoporotic patients or those unfit for surgery. Therefore, randomized clinical trials on larger patient cohorts with long-term follow-up is required to confirm efficacy, safety and inform treatment indications for TPTD in the treatment of MRONJ.

Standardized Arrabidaea chica Extract Shows Cytoprotective Effects in Zoledronic Acid-Treated Fibroblasts and Osteoblasts

INTRODUCTION

Osteonecrosis of the jaw is a condition associated with intraoral ulceration and bone necrosis induced by antiresorptive medications, such as zoledronic acid, a bisphosphonate. Previous data on Arrabidaea chica (H&B.) Verlot wound healing activity prompted the study reported herein on A. chica standardized hydro alcoholic extract in vitro cytoprotective activity data on epithelial and osteoblastic cells exposed to zoledronic acid (ZA).

METHODS

Primary human gingival fibroblasts and murine pre-osteoblasts were treated with ZA 10 µM together with 5 or 10 µg.mL-1 A. chica extract for 24h and 48 h. At both times, cells were submitted to viability assay and caspase 3/7 activation evaluation. Statistical analysis used one-way ANOVA and p=0.05.

RESULTS

In cell viability assay, a drastic damage effect of ZA appeared after 48 h in both epithelial (55.8%) and pre-osteoblastic cells (39.7%). When treated with ZA in combination with A. chica extract, cells showed higher viability values: 74.1%-82.3% for fibroblasts and 66% for pre-osteoblasts. Furthermore, the combined treatment presented lower caspase 3/7 activation in fibroblasts and pre-osteoblasts.

CONCLUSION

At low concentrations, A. chica extract showed promising cytoprotective effects against ZA-induced damage actions; however, further in vitro and in vivo studies are required to establish the mechanism of action.

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

Purpose

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

Methods

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

Results

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

Conclusions

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

A comparative effectiveness pilot study of teriparatide for medication-related osteonecrosis of the jaw: daily versus weekly administration

We studied the effectiveness of teriparatide (TPTD) for treating medication-related osteonecrosis of the jaw (MRONJ) in patients with osteoporosis and examined differences in the clinical outcomes following daily versus weekly TPTD. The outcomes were significantly improved in the entire patient series and the daily group.

PURPOSE

Teriparatide (TPTD) treatment for Stage II-III medication-related osteonecrosis of the jaw (MRONJ) in osteoporotic patients has yielded promising results in uncontrolled studies. The daily administration and the weekly administration of TPTD have been reported to improve outcomes in MRONJ. Herein, we sought to identify differences in the clinical outcomes of MRONJ patients treated with daily TPTD versus weekly TPTD.

METHODS

We enrolled 13 patients and randomly assigned them to receive either of two treatments: 1×/week 56.5-μg TPTD injection for 6 months (weekly group; n = 6 patients after 1 dropout), or 20-μg TPTD injection daily for 6 months (daily group; n = 6 patients). Patients in both groups received conventional therapy plus intensive antibiotic therapy as necessary. We compared the changes in the patients' clinical stage of MRONJ, bone metabolism, percentage of bone formation, and bone turnover markers between the weekly and daily groups.

RESULTS

TPTD treatment with MRONJ led to partial remission or complete remission in 5 daily-group patients and 3 weekly-group patients. The MRONJ stage was significantly improved from baseline to 6 months of treatment in the entire series of 12 patients (p = 0.008); the weekly group did not show significant improvement, but the daily group did (p = 0.01).

CONCLUSIONS

This study provides the first comparison of clinical outcomes between MRONJ patients who received daily or weekly TPTD injections. Six months of treatment with TPTD realized a significant improvement of MRONJ stage in both the entire patient series and the daily group.

The effects of different doses of teriparatide on bisphosphonate-related osteonecrosis of the jaw in mice

OBJECTIVES

This study aimed to investigate the therapeutic effect of different doses of teriparatide (TPTD) on bisphosphonate-related osteonecrosis of the jaw (BRONJ).

MATERIALS AND METHODS

To establish the BRONJ model, 20 mice were randomly divided into two groups: a group that received tail vein administration of zoledronic acid with dexamethasone (ZA-125 µg/kg, DEX 5 mg/kg) and a group that received saline weekly. The mice subsequently underwent bilateral maxillary first molar extraction. After 8 weeks of modelling administration, the maxilla samples were examined by micro-computed tomography and histological staining (haematoxylin and eosin, Masson's trichrome and tartrate-resistant acid phosphatase) and the cytokine level was measured (enzyme-linked immunosorbent assay and Western blot). To determine the role of TPTD in BRONJ, the same protocol as previously described was applied in 100 mice (80 received ZA + DEX, and 20 received saline). After 8 weeks of modelling administration, 80 ZA + DEX mice were randomly divided into four groups: three groups with subcutaneous administration of TPTD (i.e. T1-3, T2-10 and T3-30 µg kg^-1  day^-1 ) and one group with saline daily for the next 8 weeks. The other 20 saline mice continued to receive saline daily.

RESULTS

In Part 1, the level of receptor activator of nuclear factor-kappa Β ligand and the numbers of osteoclasts differed between the model and control groups. In Part 2, we found that TPTD had a positive effect on BRONJ in a mouse model based on clinical and histomorphological observations. Among the three treatment groups, the T1 and T2 groups significantly differed from the model group, whereas the T3 group showed no statistical differences.

CONCLUSION

Subcutaneous administration of TPTD has a beneficial effect on BRONJ in mice. Nevertheless, further studies are needed to determine whether the therapeutic effect on BRONJ is dose-dependent.

The efficacy of sustained-release chitosan microspheres containing recombinant human parathyroid hormone on MRONJ

Treatment of patients with bisphosphonate usage is a significant concern for oral surgeons because it interferes with jaw bone turnover and regeneration. In case of adverse effects manifesting related to bisphosphonate use, oral surgeons are usually treating and keep the patient's symptoms under control. In this study, we aimed to investigate a new treatment protocol for medication-related osteonecrosis of the jaw (MRONJ). This treatment protocol consisted of administering human parathyroid hormone (hPTH) loaded chitosan microspheres which were prepared by ionotropic gelation method or/and the prepared microspheres were suspended in a poloxamer gel. After in-vitro optimization studies, the efficacy of the chosen formulations was evaluated in-vivo studies. Zoledronic acid was administered daily to forty-eight adult female Sprague-Dawley rats, divided into four experimental groups, at a daily concentration of 0.11 mg/kg over three weeks to induce the MRONJ model. At the end of this period, maxillary left molar teeth were extracted. In the first group, the subjects received no treatment. In the negative control group, poloxamer hydrogel containing empty microspheres were immediately applied to the soft tissues surrounding the extraction socket. The treatment group-1 was treated with local injections of poloxamer hydrogel containing hPTH. The treatment group-2 was treated with a single local injection of poloxamer hydrogel containing hPTH-loaded chitosan microspheres. Both treatment groups received a total of 7 µg of hPTH at the end of the treatment protocol. Our study demonstrates successful attenuation of MRONJ through a local drug delivery system combined with hPTH, as opposed to previously attempted treatment strategies.

Pathogenesis of medication-related osteonecrosis of the jaw: a comparative study of in vivo and in vitro trials

Objective This study was performed to determine whether the results of prevailing in vivo and in vitro studies offer a reliable model for investigation of medication-related osteonecrosis of the jaw (MRONJ). Methods Embase, Medline, and the Cochrane Library were searched for articles published from September 2003 to June 2017 involving experimental approaches to the pathogenesis of MRONJ. In vivo and in vitro trials were analyzed with respect to the scientific question, study design, methodology, and results. Results Of 139 studies, 87, 46, and 6 conducted in vivo, in vitro, and both in vivo and in vitro experiments, respectively. Rats, mice, dogs, minipigs, sheep, and rabbits were the preferred animal models used. Osteoblasts, osteoclasts, fibroblasts, keratinocytes, macrophages, and human umbilical vein endothelial cells were the preferred cell types. Zoledronate, alendronate, ibandronate, and risedronate were the most frequent bisphosphonates used. MRONJ was most reliably induced in minipigs because of the close relationship with human bone physiology. In vitro studies showed that reduced viability, growth, and migration of cells in the bone and soft tissues were causative for MRONJ. Other than exposed jawbone after tooth extraction, no reliable cofactors were found. Conclusion The minipig is the most suitable animal model for MRONJ.

Drug holiday patterns and bisphosphonate-related osteonecrosis of the jaw

OBJECTIVES

There is limited evidence regarding the appropriate length of a bisphosphonate (BP) holiday to reduce the risk of osteonecrosis of the jaw (ONJ). In this cross-sectional study, we investigated the population-based patterns of the gaps between BP discontinuation and ONJ diagnosis.

SUBJECTS AND METHODS

We used the claims database of the National Health Insurance Service in Korea. Among BP users between 2006 and 2015, incident ONJ cases during 2010-2015 with no history of ONJ in the last 4 years were identified. We assessed the time gap from the last BP administration to ONJ diagnosis.

RESULTS

Among 1,569 incident ONJ cases, 836 (53.3%) occurred after BP discontinuation. The cumulative proportions of ONJ occurrence within 1 month, 3 months, 1 year, 2 years, and 3 years after discontinuation were 58.9%, 70.8%, 87.0%, 93.2%, and 96.1%, respectively. The length of drug holidays showed no significant difference between patients with or without comorbid cancer and diabetes mellitus (p-value, 0.12 and 0.52, respectively). However, the use of injectable BP formulations significantly affected ONJ incidence (p < 0.01).

CONCLUSIONS

Most ONJ cases occurred within 3 years from BP suspension, with a higher prevalence among BP injection users with 1 year or lesser BP holiday.

Anabolic agents: what is beyond osteoporosis?

Osteoporosis is a common skeletal disorder characterized by low bone mass, which leads to reduced bone strength and an increased risk of fractures. Anabolic agents have been shown to improve bone mass and decrease fracture risk in osteoporosis patients by directly stimulating osteoblasts to produce new bone. Currently, two anabolic agents are available in the USA: recombinantly produced teriparatide (TPTD), which is the fully active (1-34) amino active sequence of human parathyroid hormone (PTH), and abaloparatide (APTD), a synthetic analog of parathyroid hormone-related peptide (PTHrP). At present, both agents are approved only for treatment of patients with osteoporosis at high risk of fracture. Nonetheless, their anabolic properties have led to off-label application in additional settings which include spine fusion, osteonecrosis of the jaw, arthroplasty, and fracture healing. In this article, we summarize available scientific literature regarding the efficacy, effectiveness, and safety of TPTD in these off-label settings.

Surgical treatment of stage 2 medication-related osteonecrosis of the jaw compared to osteomyelitis

OBJECTIVE

To compare the characteristics and outcomes of patients who underwent surgical treatment for stage 2 medication-related osteonecrosis of the jaw (MRONJ) versus osteomyelitis.

METHODS

This retrospective study compared the following variables in 73 patients with stage 2 MRONJ versus 89 patients with osteomyelitis: impaired wound healing after surgery, sex, age, the presence of actinomycosis, location of the jaw lesion, and involvement of the inferior alveolar nerve (IAN).

RESULTS

There were significant differences between the groups in age, sex, rates of impaired wound healing, actinomycosis, and the location (anterior/posterior) of the lesion. Impaired wound healing after surgical treatment in the stage 2 MRONJ group was associated with patient age. All patients with impaired wound healing after the initial surgery recovered fully after reoperation.

CONCLUSIONS

These findings for surgical treatment of stage 2 MRONJ may help clinicians plan surgical treatment of MRONJ.

Short-term perioperative teriparatide therapy for the prevention of medication-related osteonecrosis of the jaw: A randomized, controlled preclinical study in rats

OBJECTIVE

Dentoalveolar procedures in patients receiving bisphosphonates and other antiresorptive agents are associated with an increased risk of medication-related osteonecrosis of the jaw (MRONJ). The aim of present study was to evaluate the effects of perioperative teriparatide (TPD) therapy in prevention of MRONJ.

SUBJECTS AND METHODS

Two protocols of TPD therapy were studied. For protocol A, 25 TPD-treated (AT) and 25 control (AC) rats received 5 weekly injection of 0.06 mg/kg zoledronate. At the end of week 5, extraction of bilateral mandibular first molars was performed for all rats, and 4-week TPD (20 μg/kg/day) and saline therapy was started for AT and AC rats, respectively. For protocol B, 25 TPD-treated (BT) and 25 control (BC) rats received 5 weekly injection of 0.06 mg/kg zoledronate. One week later, 4-week TPD and saline therapy was started for BT and BC rats, respectively. Both groups underwent tooth extraction at the end of week 7 of the experiment. All rats were sacrificed 8 weeks after tooth extraction and assessed clinically for bone exposure/fistula, and histologically for density of osteocytes in newly formed bone and empty osteocyte lacunae in alveolar bone.

RESULTS

Incidence of bone exposure/fistula and mean numbers of osteocytes and empty lacunae per 25 mm² (at 400× magnification) were 20%, 15.36, and 2.63 in AT group; 78%, 5.78, and 6.81 in AC group; 14%, 16.94, and 2.08 in BT group; and 78%, 7.54, and 5.95 in BC group; respectively. The differences between AT and AC and between BT and BC were statistically significant (P < 0.001). However, no statistically significant difference between AT and BT and between AC and BC was found.

CONCLUSION

Four weeks of TPD therapy, beginning at the same day or 2 weeks before tooth extraction, had a potential role in prevention of ONJ.

Interventions for treating bisphosphonate-related osteonecrosis of the jaw (BRONJ)

BACKGROUND

Bisphosphonate drugs can be used to prevent and treat osteoporosis and to reduce symptoms and complications of metastatic bone disease; however, they are associated with a rare but serious adverse event: osteonecrosis of the maxillary and mandibular bones. This condition is called bisphosphonate-related osteonecrosis of the jaw or BRONJ. BRONJ is diagnosed when people who are taking, or have previously taken, bisphosphonates have exposed bone in the jaw area for more than eight weeks in the absence of radiation treatment. There is currently no "gold standard" of treatment for BRONJ. The three broad categories of intervention are conservative approaches (e.g. mouth rinse, antibiotics), surgical interventions and adjuvant non-surgical strategies (e.g. hyperbaric oxygen therapy, platelet-rich plasma), which can be used in combination.

OBJECTIVES

To determine the efficacy and safety of any intervention aimed at treating BRONJ.

SEARCH METHODS

We searched the following databases to 15 December 2015: the Cochrane Oral Health Group Trials Register, the Cochrane Breast Cancer Group Trials Register (20 September 2011), the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE via Ovid, EMBASE via Ovid, CancerLit via PubMed, CINAHL via EBSCO and AMED via Ovid. We scanned the references cited in retrieved articles and contacted experts in the field, the first authors of included papers, study sponsors, other bisphosphonates investigators and pharmaceutical companies. We searched for ongoing trials through contact with trialists and by searching the US National Institutes of Health Trials Register (clinicaltrials.gov) and the World Health Organization Clinical Trials Registry Platform. We also conducted a grey literature search to September 2015.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing the effects of any treatment for BRONJ with another treatment or placebo.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the search results, assessed the risk of bias in the included trials and extracted data. When in dispute, we consulted a third review author.

MAIN RESULTS

One small trial at high risk of bias met the inclusion criteria. The trial randomised 49 participants, most of whom had cancer. It compared standard care (defined as surgery, antibiotics and oral rinses at the discretion of the oral-maxillofacial surgeon) to standard care plus hyperbaric oxygen therapy (2 atmospheres twice a day for 40 treatments). The trial measured the percentage of participants who improved or healed at three, six, 12 and 18 months and last contact. It also measured mean weekly pain scores.At three months, the study found that the participants in intervention group were more likely to have an improvement in their osteonecrosis than the standard care group participants (risk ratio (RR) 1.94, 95% confidence interval (CI) 1.01 to 3.74). There was no clear difference between the groups for the outcome 'healed' at three months (RR 3.60, 95% CI 0.87 to 14.82). There was no clear difference between the groups for improvement or healing when they were evaluated at six, 12 and 18 months and last contact.The study did not give any information on adverse events.Although the findings suggest adjunctive hyperbaric oxygen improved BRONJ, the quality of the evidence is very low since the only study was underpowered and was at high risk of bias due to lack of blinding, cross-over of participants between groups and very high attrition (50% at 12 months and 80% at 18 months in this study, which was designed for an intended follow-up of 24 months).

AUTHORS' CONCLUSIONS

There is a lack of evidence from randomised controlled trials to guide treatment of bisphosphonate-related osteonecrosis of the jaw (BRONJ). One small trial at high risk of bias evaluated hyperbaric oxygen therapy (HBO) as an adjunct to "standard" care and could not confirm or refute the effectiveness of HBO. There are two ongoing trials of teriparatide treatment for BRONJ. We found no randomised controlled trials of any other BRONJ treatments. High quality randomised controlled trials are needed. We provide recommendations for their focus and design.

Pathophysiology of Osteonecrosis of the Jaws

Osteonecrosis of the jaw (ONJ) is a multifactorial disease in patients with primary or metastatic bone malignancy or osteoporosis undergoing systemic antiresorptive therapy, where pathophysiology has not yet been fully determined. The staging of ONJ is based on severity of symptoms and extent of clinical and radiographic findings. Treatment strategies range from conservative local wound care to aggressive resective surgery of all necrotic bone. The first ONJ cases were reported in 2003 and 2004, and although significant progress has been made in our understanding of the disease, much more work needs to be done to completely explain its pathophysiology.

The effect of laser therapy on the expression of osteocalcin and osteopontin after tooth extraction in rats treated with zoledronate and dexamethasone

PURPOSE

Laser therapy has been used for the prevention and management of medication-related ostenecrosis of the jaw (MRONJ). The aim of this paper was to investigate the action of laser therapy on extraction socket healing in rats in conditions at risk for MRONJ, evaluating the expression of markers of bone metabolism.

METHODS

Thirty male Sprague-Dawley rats were divided in four groups: control group (C, n = 5), laser group (L, n = 5), treatment group (T, n = 10), and treatment plus laser group (T + L, n = 10). Rats of group T and T + L received zoledronate 0.1 mg/kg and dexamethasone 1 mg/kg every 2 days for 10 weeks. Rats of group C and L were infused with vehicle. After 9 weeks, the left maxillary molars were extracted in all rats. Rats of groups L and T + L received laser therapy (Nd:YAG, 1064 nm, 1.25 W, 15 Hz, 5 min, 14.37 J/cm(2)) in the socket area at days 0, 2, 4, and 6 after surgery. Western blot analysis was performed to evaluate the alveolar expression of osteopontin (OPN) and osteocalcin (OCN) 8 days after extraction.

RESULTS

Rats of groups L and T + L showed a significant higher expression of OCN compared to rats of groups C and T (+348 and +400 %, respectively; P = 0.013 and P = 0.002, respectively). The expression of OPN did not show significant differences among the different groups.

CONCLUSIONS

Our findings suggest that laser irradiation after tooth extraction can promote osteoblast differentiation, as demonstrated by the higher expression of OCN. Thus, laser irradiation could be considered a way to improve socket healing in conditions at risk for MRONJ development.