Compromised osseous healing of dental extraction sites in zoledronic acid-treated dogs

Italian position paper (SIPMO-SICMF) on medication-related osteonecrosis of the jaw (MRONJ)

OBJECTIVE

This paper aims to describe the 2023 update position paper on MRONJ developed by the Italian Societies of Oral Pathology and Medicine (SIPMO) and of Maxillofacial Surgery (SICMF).

METHODS

This is the second update following the 2013 and 2020 Italian position papers by the Expert panel, which is a representation of the two scientific societies (SIPMO and SICMF). The paper is based on an extensive analysis of the available literature from January 2003 to February 2020, and the subsequent review of literature conducted between March 2020 and December 2022 to include all new relevant published papers to confirm or modify the previous set of recommendations.

RESULTS

This position paper highlights the main issues of MRONJ on risk estimates, disease definition, diagnostic pathway, individual risk assessment, and the fundamental role of imaging in the diagnosis, classification, and management of MRONJ.

CONCLUSION

The Expert Panel confirmed the MRONJ definition, the diagnostic work-up, the clinical-radiological staging system and the prophylactic drug holiday, as recognized by SIPMO-SICMF; while, it presented novel indications regarding the categories at risk of MRONJ, the prevention strategies, and the treatment strategies associated with the therapeutic drug holiday.

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.

Interactive Associations between PPARγ and PPARGC1A and Bisphosphonate-Related Osteonecrosis of the Jaw in Patients with Osteoporosis

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a rare but severe adverse effect that can occur as a result of bisphosphonate treatment. This study aimed to examine the relationship between PPARγ and PPARGC1A polymorphisms and the BRONJ development in female osteoporosis patients undergoing bisphosphonate treatment. We prospectively conducted this nested case-control study at the Ewha Womans University Mokdong Hospital between 2014 and 2018. We assessed five single-nucleotide polymorphisms (SNPs) of PPARγ and six SNPs of PPARGC1A and performed a multivariable logistic regression analysis to determine the independent risk factors for developing BRONJ. There were a total of 123 patients included in this study and 56 patients (45.5%) developed BRONJ. In the univariate analysis, PPARGC1A rs2946385 and rs10020457 polymorphisms were significantly associated with BRONJ (p = 0.034, p = 0.020, respectively), although the results were not statistically significant in the multivariable analysis. Patients with the combined genotypes of GG in both PPARγ rs1151999 and PPARGC1A rs2946385 showed a 3.03-fold higher risk of BRONJ compared to individuals with other genotype combinations after adjusting for confounders (95% confidence interval (CI): 1.01-9.11). Old age (≥70 years) and duration of bisphosphonate use (≥60 months) increased the risk of BRONJ. The area under the receiver operating characteristic curve for the predicted probability was 0.78 (95% CI: 0.69-0.87, p < 0.001), demonstrating a satisfactory level of discriminatory power. Our study elucidated that PPARγ and PPARGC1A polymorphisms were interactively associated with BRONJ development. These results have potential implications for tailoring personalized treatments for females undergoing bisphosphonate therapy for osteoporosis.

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.

Estrogen deficiency during puberty affects the expression of microRNA30a and microRNA503 in the mandibular condyle

BACKGROUND

The aim of this study was investigated if estrogen deficiency during puberty affects the expression of miRNA30a and miRNA503 in maxillary and mandibular growth centers, and also evaluated if ERα and ERβ are correlated with miRNA30a and miRNA503 expressions.

METHODS

Samples from 12 female Wistar rats randomized into experimental group (OVX) and control group (SHAM). At an age of 45 days animals were euthanized for miRNA expression analyses. RT-qPCR was performed to determine miRNA30a and miRNA503 expression in growth sites: midpalatal suture, condyle, mandibular angle, symphysis/parasymphysis and coronoid process. The data was carried out using the parametric tests at 5% of significance level.

RESULTS

miRNA 30a and miRNA503 presented higher levels in the condylar site in SHAM group when compared with OVX (p = 0.002 and p = 0.020, respectively). In the growth centers, a statistical significant difference was observed only for miRNA30a (p = 0.004), when compared mandibular angle with condyle the in OVX group (p = 0.001). A strong positive correlation between miRNA503 and ERα in the condyle of OVX group was observed (r = 0.90; p = 0.039 and it also between miRNA503 and ERβ in the coronoid process of the OVX group (r = 0.88; p = 0.05).

CONCLUSION

The results suggested that estrogen regulates specific miRNAs in maxillary and mandibular growth centers, which may participate in posttranscriptional regulation of estrogen-regulated genes.

Drill Hole Models to Investigate Bone Repair

Our understanding of the mechanisms underlying fracture healing is rapidly developing and is contributing to new therapeutic strategies to enhance repair. To gain new insights, animal models must also evolve. From initially imprecise, uncontrolled bone defects we now have precise injury models that still capture all of the stages and phases of bone repair yet do so in a highly reproducible manner. The simple mono-cortical defect model allows assessment of bone repair through a cartilage intermediate, e.g., endochondral ossification, as well as direct bone repair, e.g., intramembranous healing. Cellular contributions of the periosteum can be distinguished from contributions originating in the bone marrow. In this chapter, we focus on the advantages of this bone repair model, as well as its limitations.

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..

Medication-Related Osteonecrosis of the Jaws

Medication-related osteonecrosis of the jaw is an oral complication in cancer patients being treated with either antiresorptive or antiangiogenic drugs. The first reports of MRONJ were published in 2003. Hundreds of manuscripts have been published in the medical and dental literature describing the complication, clinical and radiographic signs and symptoms, possible pathophysiology, and management. Despite this extensive literature, the pathobiological mechanisms by which medication-related osteonecrosis of the jaw develops have not yet been fully delineated. The aim of this manuscript is to present current knowledge about the complication ragarding to the definition, known risk factors, and clinical management recommendations. Based on this current state of the science, we also propose research directions that have potential to enhance the management of future oncology patients who are receiving these agents.

Effects of systematic bisphosphonate use in patients under orthodontic treatment: a systematic review

BACKGROUND

Bisphosphonates are a class of drugs prescribed for several osseous related disorders owing to their ability to regulate bone turnover, which could in turn affect orthodontic treatment outcomes.

OBJECTIVE

To examine the effect of bisphosphonate (BP) use on orthodontic patients through clinical and radiographic measurements.

SEARCH METHODS

Systematic and unrestricted search of 17 databases complemented with additional hand-searches were performed up to March 2019.

SELECTION CRITERIA

Articles reporting on human patients with a history of BPs administration that received orthodontic treatment were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Data regarding the medical profile of the patients, the specific type of malocclusion and the performed treatment plan, as well as the clinical and radiographic outcomes were extracted. Quality assessment was performed by the ROBINS-I tool for the cohort studies and by a slightly modified checklist from the original one proposed by Agbabiaka et al. for the case reports.

RESULTS

7 articles (1 retrospective cohort study and 6 case reports) were eventually included in the present review including 122 subjects (29 patients and 93 controls) reporting on the clinical and radiographic changes following orthodontic treatment of patients during or after BPs use. BPs seem to have a controversial effect on the clinical and patient-reported variables, even though the majority of the included patients presented with compromised treatment results and a rather slow rate of tooth movement. Most radiographic findings revealed mild root resorption, widened periodontal ligament spaces and sclerotic changes on the surrounding alveolar bone. However, these results should be interpreted with caution, due to the limited number of the eligible articles and their limitations.

LIMITATIONS

The included studies were of rather low quality due to study design and incomplete reporting.

CONCLUSIONS AND IMPLICATIONS

BP administration seems to be associated with compromised clinical outcomes, prolonged treatment time, and moderate changes on the roots and surrounding tissues of orthodontic patients.

REGISTRATION

Non-registered.

FUNDING

None.

Medication-related osteonecrosis of the jaw in a minipig model: Parameters for developing a macroscopic, radiological, and microscopic grading scheme

OBJECTIVES

To devise a macroscopic, radiological, and histological scale for assessing pathological changes associated with medication-related osteonecrosis of the jaw in a minipig model.

MATERIALS AND METHODS

Medication-related osteonecrosis of the jaw was induced in Göttingen minipigs by weekly intravenous administration of bisphosphonate (zoledronic acid) combined with a tooth extraction procedure. Controls either did not receive zoledronic acid or did not undergo tooth extraction. After 20 weeks, minipigs were euthanized and underwent computed tomography and micro-computed tomography scanning. The mandible underwent additional histological examination.

RESULTS

The most consistent macroscopic findings in animals that had developed bisphosphonate-related osteonecrosis of the jaw (BRONJ) were necrotic, denuded bone, and formation of fistula and pus. Under radiological examination, impaired extraction socket healing, decrease in attenuation of bone beneath the extraction site, and periosteal reaction were observed. Under histological examination, demineralization of the extracellular bone matrix, denuding of bone, and osteonecrosis were recorded.

CONCLUSION

These parameters were used to develop a scoring system for grading BRONJ.

Medication-related osteonecrosis of the jaw after long-term bisphosphonate treatment in a cat

A 12‐year‐old, neutered female, domestic medium hair cat was evaluated for a nonhealing, oral mucosal ulceration. The cat had a history of idiopathic hypercalcemia that had been treated with a bisphosphonate for 41 months. Oral examination identified exposed maxillary bone adjacent to a previous extraction site. Histopathology of the exposed bone and associated mucosa was most consistent with medication‐related osteonecrosis of the jaw. Treatment involved both medical and surgical interventions. Oral mucosal healing occurred after 6 months of treatment.

Clodronate-Loaded Liposome Treatment Has Site-Specific Skeletal Effects

Ineffective oral wound healing is detrimental to patients' oral health-related quality of life. Delineating the cellular mechanisms involved in optimal healing will elicit better approaches to treating patients with compromised healing. Osteal macrophages have recently emerged as important positive regulators of bone turnover. The contributions of macrophages to long bone healing have been studied, but their role in oral osseous wound healing following tooth extraction is less clear. Clodronate-loaded liposomes were used as a tool to deplete macrophages in C57BL/6J mice and assess oral osseous bone fill after extraction. In addition to macrophage ablation, osteoclast ablation occurred. Interestingly, depletion of macrophages and osteoclasts via clodronate treatment had differential effects based on skeletal location. In the nonwounded tibiae, clodronate treatment significantly increased CD68+ cells and decreased F4/80+ cells in the marrow, which correlated with increased trabecular bone volume fraction after 7 and 14 d. Serum formation and resorptive markers P1NP and TRAcP 5b were decreased as were tibial TRAP+ osteoclasts. In healing extraction sockets, clodronate treatment increased extraction socket trabecular bone thickness at 14 d, which correlated with decreased TRAP+ osteoclasts and F4/80+ macrophages. Conversely, nonwounded maxillary interseptal bone was unaffected by clodronate treatment. Furthermore, the increase in extraction socket bone fill with clodronate was less than the large increase in trabecular bone observed in a nonwounded long bone. These data suggest a temporal and spatial specificity in the roles of macrophages and osteoclasts in normal turnover and healing.

Oncologic doses of zoledronic acid induce site specific suppression of bone modelling in rice rats

OBJECTIVES

To examine the effect of zoledronic acid (ZOL) on cortical bone modelling and healing of extraction sockets in the jaw bones of a rodent model. We hypothesized ZOL suppresses both the bone formation in the modelling mode in the jaw bones and alters the extraction site healing.

MATERIAL & METHODS

Rice rats were administered saline solution and two dose regimens of ZOL: 0.1 mg/kg, twice a week, for 4 weeks (n=17, saline=8 & ZOL=9) and a higher dose of 0.4 mg/kg, weekly, for 9 weeks (n=30, saline=15 & ZOL=15). Two pairs of fluorochrome bone labels were administered. Extraction of maxillary teeth was performed in maxilla. Mineral apposition rate, mineralizing surface and bone formation rate (BFR) were quantified on periodontal (PDL), alveolar and basal bone surfaces, and in the trabecular bone of proximal tibia. Bone volume (BV) was evaluated at extraction sockets. Multivariate Gaussian models were used to account for repeated measurements, and analyzes were conducted in SAS V9.3.

RESULTS

ZOL suppressed bone modelling (BFR/BS) at the PDL surfaces in the mandible (P<.05), but its effect was not significant at the periosteal surfaces of both jaws. BV for the healing sockets of ZOL treated animals was not significantly different (P=.07) compared to the saline group. ZOL suppressive effect was higher in the tibia compared to the jaws.

CONCLUSION

ZOL severely suppresses coupled remodelling in the tibia, and the suppression of bone formation in the modelling mode in the jaws demonstrates the site specific effects of ZOL in rice rats.

Preventive Effect of Phosphodiesterase Inhibitor Pentoxifylline Against Medication-Related Osteonecrosis of the Jaw: An Animal Study

PURPOSE

The aim of this experimental study was to investigate the prophylactic effect of pentoxifylline (PTX) on medication-related osteonecrosis of the jaw (MRONJ).

MATERIALS AND METHODS

Female Sprague-Dawley rats (n = 33) received zoledronic acid (ZA) for 8 weeks to create an osteonecrosis model. The left mandibular second molars were extracted and the recovery period lasted 8 weeks before sacrifice. PTX was intraperitoneally administered to prevent MRONJ. The specimens were histopathologically and histomorphometrically evaluated.

RESULTS

Histomorphometrically, between the control and ZA groups, there was no statistically significant difference in total bone volume (P = .999), but there was a statistically significant difference in bone ratio in the extraction sockets (P < .001). A comparison of the bone ratio of the ZA group with the ZA/PTX group (PTX administered after extraction) showed no statistically significant difference (P = .69), but there was a statistically significant difference with the ZA/PTX/PTX group (PTX administered before and after extraction; P = .008). Histopathologically, between the control and ZA groups, there were statistically significant differences for inflammation (P = .013), vascularization (P = .022), hemorrhage (P = .025), and regeneration (P = .008). Between the ZA and ZA/PTX groups, there were no statistically significant differences for inflammation (P = .536), vascularization (P = .642), hemorrhage (P = .765), and regeneration (P = .127). Between the ZA and ZA/PTX/PTX groups, there were statistically significant differences for inflammation (P = .017), vascularization (P = .04), hemorrhage (P = .044), and regeneration (P = .04).

CONCLUSION

In this experimental model of MRONJ, it might be concluded that although PTX, given after tooth extraction, improves new bone formation that positively affects bone healing, it is not prophylactic. However, PTX given before tooth extraction is prophylactic. Therefore, PTX might affect healing in a positive way by optimizing the inflammatory response.

Animal model for medication-related osteonecrosis of the jaw with precedent metabolic bone disease

Despite the fact that the medications used to treat abnormal bone conditions often induce osteonecrosis of the jaw (ONJ), previous attempts to establish an animal model for ONJ have shown insufficient consideration for this important prerequisite for the development of the disease. The purpose of this study was to establish an animal model with the most common metabolic bone disease, osteoporosis. Ninty-six rats were randomly divided into ovariectomy (Ov) group (n=48) and sham-operated group (n=48). Six weeks after Ov or sham surgery, rats in each group were subdivided into bisphosphonate group (n=36 each) and control group (n=12 each) and injected with zoledronic acid and normal saline, respectively, once a week. After additional 6weeks, surgical intervention was performed, and the injections were continued for 8 more weeks. The animals were then sacrificed for further macroscopic, histological, histomorphometric, radiological, and bone biomarker investigations. As histologically determined, the Ov group (77.8%) showed higher ONJ prevalence compared to the sham group (47.2%; P<0.05). Micro-structural and histomorphometric assessments revealed that rats with ONJ (ONJ group) presented with deteriorated bone architectures with higher necrotic bone fraction and lower number of osteoclasts (P<0.05). Compared to the sham-operated ONJ group, the Ov ONJ group showed significantly lower values of Tb.N, Tb.Sp, Conn.D, N.Oc/T.Ar, and TRACP 5b and CTX/TRACP (P<0.05). The ovariectomized rat model in this study successfully mimicked human ONJ lesions with an underlying bone disease and showed different bone characteristics than that of the previous ONJ model. Based on the differences, further researches for investigating pathophysiology of ONJ, including various pharmacological responses for deteriorated bone environment, are required.

Medication-Related Osteonecrosis of the Jaw: Basic and Translational Science Updates

In the late 1990s and the early 2000s, bisphosphonates had become the clinical pillar of excellence for treating metabolic bone disease, and thus their connection with osteonecrosis of the jaw (ONJ) caused significant concern. Over the past decade, progress has been made in understanding what is now referred to as medication-related ONJ (MRONJ), because of its connections to agents other than bisphosphonates, although in many respects the progress has been slow. This review highlights the key basic science and translational (animal) studies in the area of MRONJ and suggests areas of focus as the field moves into the next decade.

In Vivo UTE-MRI Reveals Positive Effects of Raloxifene on Skeletal-Bound Water in Skeletally Mature Beagle Dogs

Raloxifene positively affects mechanical properties of the bone matrix in part through modification of skeletal-bound water. The goal of this study was to determine if raloxifene-induced alterations in skeletal hydration could be measured in vivo using ultra-short echotime magnetic resonance imaging (UTE-MRI). Twelve skeletally mature female beagle dogs (n = 6/group) were treated for 6 months with oral doses of saline vehicle (VEH, 1 mL/kg/d) or raloxifene (RAL, 0.5 mg/kg/d). After 6 months of treatment, all animals underwent in vivo UTE-MRI of the proximal tibial cortical bone. UTE-MRI signal intensity versus echotime curves were analyzed by fitting a double exponential to determine the short and long relaxation times of water with the bone (dependent estimations of bound and free water, respectively). Raloxifene-treated animals had significantly higher bound water (+14%; p = 0.05) and lower free water (-20%) compared with vehicle-treated animals. These data provide the first evidence that drug-induced changes in skeletal hydration can be noninvasively assessed using UTE-MRI.

A Model for Osteonecrosis of the Jaw with Zoledronate Treatment following Repeated Major Trauma

This study aims to develop a reproducible rat model for post-traumatic bisphosphonate-related osteonecrosis of the jaw (BRONJ). In our previous studies using dental extraction as an inducing factor, only 30%-60% of zoledronate-treated animals fulfilled the definition of clinical BRONJ. We modified the zoledronate regimen and introduced repeated surgical extraction to illicit quantifiable BRONJ in all animals. Eighty retired-breeder female Sprague-Dawley rats were divided between the treatment (i.v. zoledronate; 80 μg/kg/week for 13 weeks) and control (saline) groups. On week 13, the left mandibular first molar was surgically extracted, followed by the second molar a week later. Animals were euthanized at 1-week, 2-weeks, and 8-weeks following extraction. The occurrence and severity of BRONJ were scored in each animal based on gross and MicroCT analysis. Parameters of bone formation and osteoclast functions at the extraction site were compared between groups. All zoledronate-treated animals developed a severe case of BRONJ that fulfilled the clinical definition of the condition in humans. Osteoclast attachment continued to be defective eight weeks after stopping the treatment. There were no signs of kidney or liver toxicity. Our data confirmed that repeated surgical extraction (major trauma) by itself consistently precipitated massive bone necrosis in ZA-treated animals, eliminating the need to induce pre-existing infection or comorbidity. These results will be the basis for further studies examining the in-vivo pathogenesis and prevention of BRONJ.

A novel model of bisphosphonate-related osteonecrosis of the jaw in rats

OBJECTIVE

To establish a rat model of bisphosphonate-related osteonecrosis of the jaw (BRONJ) that realistically mimics major clinical manifestations of the disease.

METHODS

Female Sprague Dawley rats received intravenous zoledronate 80 μg/kg once a week via the tail vein. Three weeks after intravenous injection, maxillary first molars were extracted under general anesthesia. Then 1, 4 and 12 weeks after tooth extraction, the rats were euthanized, and the intact maxillas were harvested en bloc. Macroscopic analysis, histological analysis and cytokine analysis were performed. Untreated rats with tooth extraction were used as controls.

RESULTS

12 weeks after extraction, rats treated with zoledronate developed BRONJ-like disease, including characteristic features of impaired soft tissue healing, exposed necrotic bone or sequestra, increased inflammatory infiltrates, while the controls showed normal bone healing. 4 weeks after extraction, rats treated with zoledronate exhibited the decreased receptor activator of nuclear factor kappa-B ligand (RANKL) values, the increased osteoprotegerin (OPG) values and the remarkable decreased RANKL/OPG ratio when compared with the controls.

CONCLUSION

The rats treated with zoledronate can be considered a novel, reliable and reproducible animal model to better understand the pathophysiology and pathogenesis of BRONJ and to develop a therapeutic approach.

Zoledronate induces osteonecrosis of the jaw in sheep

INTRODUCTION

The treatment of bisphosphonate-related osteonecrosis of the jaw has become routine in maxillofacial hospitals. However, the etiopathology has not yet been fully understood. The aim of this study was to develop a large animal model for medication-related osteonecrosis of the jaw (MRONJ).

MATERIAL AND METHODS

Eight Swiss mountain sheep were randomly assigned into two groups. Group I received 0.075 mg/kg zoledronate (ZOL) intravenously every third week for 16 weeks. After 16 weeks, extraction of the first and second lower left premolar was performed. Group II underwent surgery and no ZOL was administered. After surgery, Group I continued to receive ZOL infusions; after 16 weeks, all animals were euthanized. The jaw bones were investigated macroscopically, radiographically (computed tomography) and histologically.

RESULTS

Osteonecrosis of the jaw was observed at all extraction sites in all the animals receiving ZOL, and at none of the sites in animals without ZOL. All ZOL-treated animals spontaneously developed exposed bone lesions in the oral cavity at sites where no surgical intervention was performed. CT imaging shows persistent alveolar extraction sockets 16 weeks after surgery in all animals of the ZOL-group, and healed alveolar extraction sockets in non-ZOL-treated animals.

CONCLUSION

Sheep treated with ZOL reproducibly demonstrated osteonecrosis of the jaw after tooth extraction, and spontaneous development of exposed bone in the oral cavity at sites where no manipulation was performed. This animal model can be used for further research in the fields of BP-ONJ etiopathology, oral implantology, bone and fracture healing and periodontology.

Influence of Zoledronic Acid on Atrial Electrophysiological Parameters and Electrocardiographic Measurements

INTRODUCTION

Our objective was to determine effects of zoledronic acid (ZA) on atrial electrophysiological parameters and electrocardiographic measurements.

METHODS AND RESULTS

Ex vivo perfusion study: Isolated guinea pig hearts were perfused with modified Krebs-Henseleit (K-H) buffer with or without ZA 0.07 mg/kg/L (each n = 6). In ZA-perfused hearts, atrial action potential at 90% repolarization (APD90 ) decreased more from baseline than in controls (-23.2% ± -5.1% vs. -2.1% ± -8.1%, P < 0 .0001), as did APD30 (-28.8% ± -3.8% vs. -2.1% ± -2.1%, P < 0.0001). In vivo dose-response study: Guinea pigs underwent intraperitoneal injections every 2 weeks in 1 of 4 groups (each n = 8): ZA 0.007 mg/kg (low-dose), ZA 0.07 mg/kg (medium-dose), ZA 0.7 mg/kg (high-dose), or placebo. Hearts were excised at 8 weeks and perfused with modified K-H. Atrial effective refractory period (ERP) was lower with medium- and high-dose ZA versus placebo (P = 0.004). Atrial APD30 was lower with high-dose ZA versus placebo, low and medium doses (P < 0.001). Canine ECG study: Mature female beagles received intravenous ZA 0.067 mg/kg or saline (placebo; each n = 6) every 2 weeks for 12 weeks. P wave dispersion was greater in the ZA group (7.7 ± 3.7 vs. 3.4 ± 2.6 ms, P = 0.04). There were no significant differences in P wave index, maximum or minimum P wave duration, or PR interval.

CONCLUSION

ZA shortens left atrial APD and ERP and increases P wave dispersion.

Diagnosis and management of osteonecrosis of the jaw: a systematic review and international consensus

This work provides a systematic review of the literature from January 2003 to April 2014 pertaining to the incidence, pathophysiology, diagnosis, and treatment of osteonecrosis of the jaw (ONJ), and offers recommendations for its management based on multidisciplinary international consensus. ONJ is associated with oncology-dose parenteral antiresorptive therapy of bisphosphonates (BP) and denosumab (Dmab). The incidence of ONJ is greatest in the oncology patient population (1% to 15%), where high doses of these medications are used at frequent intervals. In the osteoporosis patient population, the incidence of ONJ is estimated at 0.001% to 0.01%, marginally higher than the incidence in the general population (<0.001%). New insights into the pathophysiology of ONJ include antiresorptive effects of BPs and Dmab, effects of BPs on gamma delta T-cells and on monocyte and macrophage function, as well as the role of local bacterial infection, inflammation, and necrosis. Advances in imaging include the use of cone beam computerized tomography assessing cortical and cancellous architecture with lower radiation exposure, magnetic resonance imaging, bone scanning, and positron emission tomography, although plain films often suffice. Other risk factors for ONJ include glucocorticoid use, maxillary or mandibular bone surgery, poor oral hygiene, chronic inflammation, diabetes mellitus, ill-fitting dentures, as well as other drugs, including antiangiogenic agents. Prevention strategies for ONJ include elimination or stabilization of oral disease prior to initiation of antiresorptive agents, as well as maintenance of good oral hygiene. In those patients at high risk for the development of ONJ, including cancer patients receiving high-dose BP or Dmab therapy, consideration should be given to withholding antiresorptive therapy following extensive oral surgery until the surgical site heals with mature mucosal coverage. Management of ONJ is based on the stage of the disease, size of the lesions, and the presence of contributing drug therapy and comorbidity. Conservative therapy includes topical antibiotic oral rinses and systemic antibiotic therapy. Localized surgical debridement is indicated in advanced nonresponsive disease and has been successful. Early data have suggested enhanced osseous wound healing with teriparatide in those without contraindications for its use. Experimental therapy includes bone marrow stem cell intralesional transplantation, low-level laser therapy, local platelet-derived growth factor application, hyperbaric oxygen, and tissue grafting.

The effects of bisphosphonate on the remodeling of different irregular bones in mice

BACKGROUND

We aimed to compare the effects of bisphosphonate on the remodeling of irregular bones (the jaw and ilium) in mice after trauma.

METHODS

To verify the feasibility of modeling osteonecrosis, 20 mice were injected intraperitoneally with zoledronate and dexamethasone (ZOL&DEX group), dexamethasone (DEX group), or phosphate-buffered saline (PBS) [control (CTR) group]. Mice then underwent extraction of the right maxillary first molar and creation of an artificial bony cavity in the ilium. Bone sections were stained with H&E for morphological studies. To further compare differences between the maxilla and the ilium caused by similar traumas, 80 mice were injected intraperitoneally with ZOL&DEX or PBS. Pathological progression at the injury sites was assessed at 1 day and at 1, 3, and 8 weeks after trauma using micro-computed tomography (CT), H&E and immunohistochemistry analyses, high-performance liquid chromatography-mass spectrometry, and enzyme-linked immunosorbent assay.

RESULTS

Only the ZOL&DEX model group effectively developed osteonecrosis. Bony sequestra, osseous sclerosis, unhealed mucosa, and radiopaque alveolar bone were found in the maxilla. In the ilium, there was a lower frequency of osteonecrotic disease and osseous sclerosis, and less suppression of bone remodeling than in the maxilla following long-term bisphosphonate administration. Zoledronate levels were higher in the maxilla. ZOL&DEX treatment suppressed the levels of RANKL and IL-17, but induced an upregulation of osteoprotegerin and FAM20C in both bones.

CONCLUSION

Accumulation of bisphosphonate may increase the incidence of osteonecrosis. The RANKL/OPG pathway and IL-17 and FAM20C cytokines play key roles in the progression of pathologically abnormal bone remodeling.

Atraumatic tooth extraction in patients taking bisphosphonates: a review of literature and experience with three cases

PURPOSE

Regev et al. first re-introduced the method of atraumatic tooth extraction with orthodontic elastics in 2008. Since then, the method has been mentioned regularly in literature. Nevertheless, the need for additional more detailed information remains.

METHODS

We present a review of literature and a retrospective analysis of our three patients receiving bisphosphonate medication. Two of our patients suffered from bisphosphonate-related osteonecrosis of the jaw (BRONJ). All three patients underwent atraumatic tooth extraction, which we describe in detail.

RESULTS

Regev et al. reported satisfactory results using the novel method. We removed six teeth in two patients with continued chemotherapy or bisphosphonate therapy in a time span of 26.2 ± 16.4 weeks successfully. None of the patients developed exposed bone in the follow-up (7.4 ± 0.2 months). In one case, the technique had to be discontinued due to increasing tooth soreness.

CONCLUSIONS

Atraumatic tooth extraction seems to be a safe method to prevent bone exposure, even in cases with BRONJ. The time required of our patients for exfoliation exceeded the time mentioned in literature considerably. This proved to be a major limitation. Our cases showed that patients with good compliance, no sore teeth, or painful BRONJ lesions, benefited from atraumatic tooth extraction. One of the method's major advantages might be the possibility to continue chemotherapy and bisphosphonate therapy throughout the treatment.

Osteonecrosis of the jaw: BRONJ and ARONJ

Bisphosphonates and other more recent antiresorptive agents are potent inhibitors of osteoclast function and osteoclast-mediated bone resorption. As such, they have been effectively utilised to reduce skeletally related events and improve the quality of life of patients with osteoporosis and malignant osteolytic disease. Despite these benefits, osteonecrosis of the jaw continues to be a worrisome complication in a small subset of patients receiving these drugs.

Molecular alterations of bone quality in sequesters of bisphosphonates-related osteonecrosis of the jaws

Compared to healthy bone, the intrinsic bone materials properties in the pre-existing lamellar bone are altered in jaw bone sequesters of bisphosphonates (BP)-related osteonecrosis.

INTRODUCTION

The aim of this study was to evaluate the human jaw bone quality, especially intrinsic bone material properties among sequesters of osteonecrosis of the jaw (ONJ) induced by BP.

METHODS

Bone sequesters were obtained from 24 patients suffering from ONJ following a BP treatment. Within BP-exposed bone samples, benign-BP and malignant-BP groups were distinguished in relation to the underlying disease: osteoporosis and bone metastases or multiple myeloma, respectively. Healthy cadaveric cortical jaw bone samples were used as controls. The physicochemical parameters of bone samples - mineral/organic ratio, relative proteoglycan content, crystallinity, monohydrogen phosphate content, and type-B carbonate substitution - were evaluated by Raman microspectroscopy. Representative Raman spectral features of bones control and BP-exposed bone sequesters were identified with the Partial-Least-Square Discriminant Analysis (PLS-DA).

RESULTS

BP-exposed bone sequesters are characterized by a significant increase of mineral to organic ratio (+12 %) and a significant decrease of relative proteoglycan content (-35 %), thus regulating initial collagen matrix mineral deposition. Structural changes on mineral components are revealed by a significant decrease of both crystallinity (-2 %) and mineral maturation (-41 %) in the BP-exposed bone sequesters compared to healthy bones. These modifications were also observed distinctly in both benign-BP and malignant-BP groups. In addition, a shift of the phosphate ν1 band was highlighted by PLS-DA between bones control and BP-exposed bone sequesters, revealing a disruption of the apatitic phosphate environment in the jaw bone sequesters.

CONCLUSIONS

The present data show that jaw bone quality can be altered with an overmineralization and ultrastructural modifications of apatitic mineral in bone sequesters of BP-related ONJ.

Atypical subtrochanteric and diaphyseal femoral fractures: second report of a task force of the American Society for Bone and Mineral Research

Bisphosphonates (BPs) and denosumab reduce the risk of spine and nonspine fractures. Atypical femur fractures (AFFs) located in the subtrochanteric region and diaphysis of the femur have been reported in patients taking BPs and in patients on denosumab, but they also occur in patients with no exposure to these drugs. In this report, we review studies on the epidemiology, pathogenesis, and medical management of AFFs, published since 2010. This newer evidence suggests that AFFs are stress or insufficiency fractures. The original case definition was revised to highlight radiographic features that distinguish AFFs from ordinary osteoporotic femoral diaphyseal fractures and to provide guidance on the importance of their transverse orientation. The requirement that fractures be noncomminuted was relaxed to include minimal comminution. The periosteal stress reaction at the fracture site was changed from a minor to a major feature. The association with specific diseases and drug exposures was removed from the minor features, because it was considered that these associations should be sought rather than be included in the case definition. Studies with radiographic review consistently report significant associations between AFFs and BP use, although the strength of associations and magnitude of effect vary. Although the relative risk of patients with AFFs taking BPs is high, the absolute risk of AFFs in patients on BPs is low, ranging from 3.2 to 50 cases per 100,000 person-years. However, long-term use may be associated with higher risk (∼100 per 100,000 person-years). BPs localize in areas that are developing stress fractures; suppression of targeted intracortical remodeling at the site of an AFF could impair the processes by which stress fractures normally heal. When BPs are stopped, risk of an AFF may decline. Lower limb geometry and Asian ethnicity may contribute to the risk of AFFs. There is inconsistent evidence that teriparatide may advance healing of AFFs.

Early inhibitory effects of zoledronic acid in tooth extraction sockets in dogs are negated by recombinant human bone morphogenetic protein

PURPOSE

This study was conducted with 2 purposes. The first was to determine the effect of a single dose of zoledronic acid (ZA) on the healing of a tooth extraction socket in dogs. The second was to determine if placement of recombinant human bone morphogenetic protein-2 (rhBMP-2)/absorbable collagen sponge (ACS) - INFUSE, (Medtronic, Memphis, TN) into these extraction sockets would inhibit the inhibition on bone healing and remodeling by ZA.

MATERIALS AND METHODS

Nine adult female beagle dogs (2 to 3 yr old) were placed into 3 groups of 3 dogs each. Group I received 15 mL of sterile saline intravenously; group II received 2.5 mg of ZA intravenously; and group III received 5 mg of ZA intravenously. Forty-five days after treatment, all dogs underwent extraction of noncontiguous right and left mandibular first molars and second premolars. In group I, the right mandibular extraction sockets had nothing placed in them, whereas the left mandibular sockets had only ACS placed in them. In groups II and III, the right mandibular sockets had rhBMP-2/ACS placed in them, whereas the left mandibular sockets had only ACS placed. All extraction sockets were surgically closed. Tetracycline was given intravenously 5 and 12 days later, and all animals were euthanized 15 days after tooth extraction. The extraction sockets and rib and femur samples were harvested immediately after euthanasia, processed, and studied microscopically.

RESULTS

A single dose of ZA significantly inhibited healing and bone remodeling in the area of the tooth extractions. The combination of rhBMP-2/ACS appeared to over-ride some of the bone remodeling inhibition of the ZA and increased bone fill in the extraction sites, and remodeling activity in the area was noted. The effects of rhBMP-2/ACS were confined to the area of the extraction sockets because bone activity at distant sites was not influenced.

CONCLUSIONS

A single dose of ZA administered intravenously inhibits early healing of tooth extraction sockets and bone remodeling in this animal model. The combination of rhBMP-2/ACS significantly increased bone fill and bone remodeling in these areas, negating much of the effect of the ZA.

Evaluation of socket healing in patients undergoing bisphosphonate therapy: experience of a single Institution

OBJECTIVE

To assess the clinical features of exodontias performed in cancer patients who have been receiving intravenous bisphosphonates (BPs).

STUDY DESIGN

This is a retrospective cohort study using a sample of 20 patients receiving BPs who had 62 teeth extracted. An univariate analysis was applied to calculate socket healing time (HT), comparing among exodontias performed according to cause, such as periodontal disease or caries, type of BP, and use of corticosteroid. In order to analyze the influence of each variable on HT, multiple statistical analyses were performed through logistic multiple regression.

RESULTS

From the 62 tooth extractions performed, 5 exodontias had evolved to 4 sites of bisphosphonate-related osteonecrosis of the jaws (BOJ). Of another 57 exodontias without development of BOJ, HT was significantly better for tooth extraction performed in patients receiving corticosteroid (p= .01), for tooth extracted due to caries (p= .04), and for extractions under pamidronate (p= .03). Sockets after exodontias due to periodontal diseases had OR= 5.22 (95% CI 1.73-133.66, p=0.01) for delayed HT, exodontias performed under corticosteroid use had OR=0.04 (95% CI 0.01-0.40, p<0.001), and exodontias performed under zoledronate had OR=0.31 (95% CI 0.08-1.25, p=0.10).

CONCLUSIONS

Exodontias performed in patients under BP therapy had a low rate of BOJ occurrence. Zoledronate and periodontal diseases influence delayed socket healing. Adjuvant antibiotics could be relevant procedures aimed at reducing the risk of BOJ development.

Zoledronate effects on systemic and jaw osteopenias in ovariectomized periostin-deficient mice

Osteoporosis and periodontal disease (PD) are frequently associated in the elderly, both concurring to the loss of jaw alveolar bone and finally of teeth. Bisphosphonates improve alveolar bone loss but have also been associated with osteonecrosis of the jaw (ONJ), particularly using oncological doses of zoledronate. The effects and therapeutic margin of zoledronate on jaw bone therefore remain uncertain. We reappraised the efficacy and safety of Zoledronate (Zol) in ovariectomized (OVX) periostin (Postn)-deficient mice, a unique genetic model of systemic and jaw osteopenia. Compared to vehicle, Zol 1M (100 µg/kg/month) and Zol 1W (100 µg/kg/week) for 3 months both significantly improved femur BMD, trabecular bone volume on tissue volume (BV/TV) and cortical bone volume in both OVX Postn^+/+ and Postn^−/− (all p<0.01). Zol 1M and Zol 1W also improved jaw alveolar and basal BV/TV, although the highest dose (Zol 1W) was less efficient, particularly in Postn^−/−. Zol decreased osteoclast number and bone formation indices, i.e. MAR, MPm/BPm and BFR, independently in Postn^−/− and Postn^+/+, both in the long bones and in deep jaw alveolar bone, without differences between Zol doses. Zol 1M and Zol 1W did not reactivate inflammation nor increase fibrous tissue in the bone marrow of the jaw, whereas the distance between the root and the enamel of the incisor (DRI) remained high in Postn^−/− vs Postn^+/+ confirming latent inflammation and lack of crestal alveolar bone. Zol 1W and Zol 1M decreased osteocyte numbers in Postn^−/− and Postn^+/+ mandible, and Zol 1W increased the number of empty lacunae in Postn^−/−, however no areas of necrotic bone were observed. These results demonstrate that zoledronate improves jaw osteopenia and suggest that in Postn^−/− mice, zoledronate is not sufficient to induce bone necrosis.

Absence of exposed bone following dental extraction in beagle dogs treated with 9 months of high-dose zoledronic acid combined with dexamethasone

PURPOSE

Factors contributing to osteonecrosis of the jaw with anti-remodeling drug treatment are unclear. Epidemiologic and experimental studies have suggested the combination of bisphosphonates and dexamethasone results in osteonecrosis of the jaw more often than either agent alone. The goal of this study was to assess the combination of these 2 drugs in a large animal model previously shown to be susceptible to exposed bone in the oral cavity when treated with bisphosphonates.

MATERIALS AND METHODS

Skeletally mature beagle dogs were untreated controls or treated with zoledronic acid (ZOL), dexamethasone (DEX), or ZOL plus DEX. ZOL and DEX were given at doses based on those used in humans. All animals underwent single molar extraction at 7 and 8 months after the start of the study. Extraction sites were obtained at month 9 for assessment of osseous healing using micro-computed tomography and histology.

RESULTS

No animals were observed to have exposed bone after dental extraction, yet 1 animal treated with ZOL and 1 treated with ZOL plus DEX had severely disrupted extraction sites as viewed by computed tomography and histology. These 2 animals had an intense periosteal reaction that was less obvious but still present in all ZOL-treated animals and absent from untreated animals. There was no significant difference in bone volume within the socket among groups at 4 or 8 weeks after healing, yet the ratio of surface to volume was significantly higher in animals treated with ZOL plus DEX at 8 weeks compared with control animals.

CONCLUSIONS

These findings suggest a more complex pathophysiology to osteonecrosis of the jaw than is implied by previous epidemiologic studies and those in rodents and raise questions about the potential role of DEX in its etiology.

Bone vascularization in normal and disease conditions

Bone vasculature is essential for many processes, such as skeletal development and growth, bone modeling and remodeling, and healing processes. Endothelium is an integral part of bone tissue, expressing a physiological paracrine function via growth factors and chemokines release, and interacting with several cellular lines. Alterations of the complex biochemical interactions between vasculature and bone cells may lead to various clinical manifestations. Two different types of pathologies result: a defect or an excess of bone vasculature or endothelium metabolism. Starting from the molecular basis of the interactions between endothelial and bone cells, the Authors present an overview of the recent acquisitions in the physiopathology of the most important clinical patterns, and the modern therapeutic strategies for their treatments.

Emerging concepts in the management and treatment of osteonecrosis of the jaw

Since the first description of bone necrosis in patients receiving bisphosphonate therapy in 2004, there have been multiple retrospective, prospective, and case-control studies that have served to characterize the diagnosis, associated risk factors, and treatment of this new complication. Bisphosphonate-related osteonecrosis of the jaw is at present associated with several risk factors that are identified across several disciplines in medicine and dentistry. With this level of broad-based recognition, new clinical and basic science research initiatives have begun and are likely to elucidate the etiopathogenesis of this disease process, significantly improving the level of disease management and prevention.

Bisphosphonate related osteonecrosis of the jaw: A minipig large animal model

Bisphosphonate related osteonecrosis of the jaw (BRONJ) is rare but potentially severe, and the etiopathology and risk factors are poorly defined. To date, it has not been possible to induce BRONJ in a large animal model, a shortfall this study aims to redress. Ten two-year-old adult Göttingen minipigs were split into two groups. Five pigs (group 1) were administered intravenously a weekly dose of a bisphosphonate (zoledonate 0.05mg/kg body weight, approximating the oncologic dose in humans) and five pigs (group 2) served as controls. After 6 weeks, tooth extractions were performed in the upper and lower jaw (both groups) and the bisphosphonate administration continued for a further 10 weeks (group 1 only). Clinical and blood parameters were monitored throughout the entire experiment; thereafter, the jaw-bones were subjected to macroscopic, radiological (CT) and histological investigations. Whilst the extraction sites in the control group healed within two weeks, all animals in the bisphosphonate group exhibited exposed bone and impaired wound healing, indicators that are synonymous of macroscopically advanced osteonecrosis. Radiological and in particular histological investigations confirmed the presence of BRONJ in the animals from group 1. This paper demonstrates that the administration of bisphosphonates, in combination with tooth extractions, induces BRONJ in a minipig model. The ability to study BRONJ in miniature pigs, animals with a bone structure not dissimilar to humans, may improve our knowledgebase regarding the etiopathology, the prophylaxis and potentially uncover new therapies of BRONJ.

Multiple systemic diseases complicated by bisphosphonate osteonecrosis: a case report

AIMS

this work aims at demonstrating that multiple systemic conditions, in association with the development of bisphosphonate associated osteonecrosis of the jaw (ONJ), increase the risk of complications and may lead to hospitalization. For this reason the dental approach to patients with multisystem disease should be carefully managed by a team of specialists.

CASE REPORT

a case of mandibular necrosis associated with intake of oral bisphosphonates in a complex systemic context is described.

RESULTS AND DISCUSSION

many different diseases and systemic conditions may draw the line at oral surgery. Multiple treatments (e.g. antithrombotic, calcium channel blockers, diuretics, antibiotics and bisphosphonates) can alter the normal physiological response to tissue healing.

CONCLUSIONS

patients taking bisphosphonates for more than three years (i.e. the term over which the risk of ONJ increases according to the literature, in presence of complex systemic situations, need to be carefully managed during the pre-operative, peri-operative and postoperative phases through a synergistic collaboration among different kind of specialists.

Ovariectomy stimulates and bisphosphonates inhibit intracortical remodeling in the mouse mandible

OBJECTIVE

The pathophysiology of osteonecrosis of the jaw (ONJ) is thought to be linked to suppression of intracortical remodeling. The aim of this study was to determine whether mice, which normally do not undergo appreciable amounts of intracortical remodeling, could be stimulated by ovariectomy to remodel within the cortex of the mandible and if bisphosphonates (BPs) would suppress this intracortical remodeling.

MATERIAL AND METHODS

Skeletally mature female C3H mice were either ovariectomized (OVX) or SHAM operated and treated with two intravenous doses of zoledronic acid (ZOL, 0.06 mg/kg body weight) or vehicle (VEH). This ZOL dose corresponds to the dose given to patients with cancer on a mg/kg basis, adjusted for body weight. Calcein was administered prior to sacrifice to label active formation sites. Dynamic histomorphometry of the mandible and femur was performed.

RESULTS

Vehicle-treated OVX animals had significantly higher (eightfold) intracortical remodeling of the alveolar portion of the mandible compared to sham--this was significantly suppressed by ZOL treatment. At all skeletal sites, overall bone formation rate was lower with ZOL treatment compared to the corresponding VEH group.

CONCLUSIONS

Under normal conditions, the level of intracortical remodeling in the mouse mandible is minimal but in C3H mice it can be stimulated to appreciable levels with ovariectomy. Based on this, if the suppression of intracortical remodeling is found to be part of the pathophysiology of ONJ, the ovariectomized C3H mouse could serve as a useful tool for studying this condition.

In vivo effects of zoledronic acid on oral mucosal epithelial cells

OBJECTIVE

Osteonecrosis of the jaw is a serious complication of bisphosphonate treatment for which the pathophysiology is unknown. The purpose of this study was to investigate whether in vivo zoledronic acid (ZA) induces alterations in cell proliferation, apoptosis, and matrix metalloproteinases (MMPs) expression in oral mucosal epithelial cells.

METHODS

One-year-old dogs were either untreated (control group) or given high doses of intravenous ZA (ZA group) for 3 months. The doses of ZA were equivalent to those given to cancer patients, yet were administered two times more frequently (every 2 weeks). Mucosal tissues were assessed immunohistochemically for cell proliferation (proliferating cell nuclear antigen, PCNA), matrix metalloproteinase (MMP) expression, and apoptosis (caspase 3 and TUNEL).

RESULTS

There were no significant differences between the groups with respect to PCNA, MMP-2, MMP-14, and TUNEL positive cells. However, the expression of MMP-9 was significantly higher in the control group than in the ZA group (P < 0.05), whereas the expression of caspase 3 was significantly lower in the control group than in the ZA group (P < 0.05).

CONCLUSION

  These results suggest that high doses of ZA resulted in higher levels of apoptosis and lower levels of MMP-9 in the oral epithelial cells supporting the idea of bisphosphonate treatment affects the oral mucosa.