Implant-assisted removable partial dentures: Part II. a systematic review of the effects of implant position on the biomechanical behavior.

PURPOSE: This systematic review aimed to evaluate the effects of implant placement sites on the biomechanical behavior of implant-assisted removable partial dentures (IARPDs) using finite element analysis (FEA). STUDY SELECTION: Two reviewers independently conducted manual searches of the PubMed, Scopus, and ProQuest databases for articles investigating implant location in IARPDs using FEA, according to the 2020 Systematic Reviews and Meta-analyses statement. Studies published in English up to August 1, 2022, were included in the analysis based on the critical question. RESULTS: Seven articles meeting the inclusion criteria were systematically reviewed. Six studies investigated mandibular Kennedy Class I and one study investigated mandibular Kennedy Class II. Implant placement reduced the displacement and stress distribution of the IARPD components, including dental implants and abutment teeth, regardless of the Kennedy Class type and dental implant placement site. Most of the included studies showed that, based on the biomechanical behavior, the molar region, rather than the premolar region, is the preferred implant placement site. None of the selected studies investigated the maxillary Kennedy Class I and II. CONCLUSIONS: Based on the FEA regarding mandibular IARPDs, we concluded that implant placement in both the premolar and molar regions improves the biomechanical behaviors of IARPD components, regardless of the Kennedy Class. Implant placement in the molar region results in more suitable biomechanical behaviors compared with implant placement in the premolar region in Kennedy Class I. No conclusion was reached for Kennedy Class II due to the lack of relevant studies.

Implant-assisted removable partial dentures: Part I. a scoping review of clinical applications.

PURPOSE: This scoping review aimed to systematically map research regarding implant-assisted removable partial dentures (IARPDs), and identify existing gaps in knowledge. STUDY SELECTION: Two reviewers independently conducted a search of the MEDLINE-PubMed and Scopus databases according to the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) extension for Scoping Review and included articles published in English up to August 31, 2022, including human studies, reviews, and in vitro studies. Expert opinions, animal studies, and clinical studies involving complete overdentures were excluded, and ten aspects for establishing the treatment strategy for IARPDs were examined. RESULTS: One hundred and twelve articles were chosen. There were two treatment modalities: IARPDs retained by implant- and tooth-supported surveyed single crowns (SCs) or fixed partial dentures (FPDs). In IARPDs retained by tooth-supported surveyed SCs or FPDs, the survival rate of dental implants for IARPDs was relatively higher with a wide range of marginal bone loss and many complications, but with improved functional performance, oral health-related quality of life, and patient satisfaction. There were limited data on survival or success rates and designs of IARPDs, attachment selections, length and diameter, inclination, placement sites, and loading protocols of implants, regardless of prosthetic types. There was limited information on maxillary IARPDs except for survival rates of implants. CONCLUSIONS: Although IARPDs could become a useful treatment strategy, there is limited scientific consensus with gaps in knowledge about their use. Additional well-designed clinical and in vitro studies are necessary to scientifically establish IARPDs as definitive prostheses in implant dentistry.

Medication-related osteonecrosis of the jaw: A literature review and update.

Since the initial description of medication-related osteonecrosis of the jaw (MRONJ) almost two decades ago, the potential pathophysiology and risk factors have been elaborated on in many investigations and guidelines. However, the definitive pathophysiology based on scientific evidence remains lacking. Consequently, the optimal clinical treatment and prevention strategies for MRONJ have not been established. Despite their different mechanisms of action, many drugs, including bisphosphonates, denosumab, angiogenesis inhibitors, and other medications, have been reported to be associated with MRONJ lesions in cancer and osteoporosis patients. Importantly, MRONJ occurs predominantly in the jawbones and other craniofacial regions, but not in the appendicular skeleton. In this up-to-date review, the currently available information and theories regarding MRONJ are presented from both clinical and basic science perspectives. The definition and epidemiology of MRONJ, triggering medication, and histopathology are comprehensively summarized. The immunopathology and the potential pathophysiology based on immune cells such as neutrophils, T and B cells, macrophages, dendritic cells, and natural killer cells are also discussed. In addition, antiangiogenesis, soft tissue toxicity, necrotic bone, osteocyte death, and single-nucleotide polymorphisms are examined. Moreover, other possible mechanisms of MRONJ development are considered based on the unique embryological characteristics, different cell behaviors between jawbones and appendicular skeleton, unique anatomical structures, and sustained bacterial exposure in the oral cavity as a basis for MRONJ site specificity. Based on the literature review, it was concluded that multiple factors may contribute to the development of MRONJ, although which one is the key player triggering MRONJ in the craniofacial region remains unknown.

Zoledronic Acid Deteriorates Soft and Hard Tissue Healing of Murine Tooth Extraction Sockets in a Dose-Dependent Manner.

The pathophysiology, histopathology, and immunopathology of bisphosphonate-related osteonecrosis of the jaw (BRONJ) Stage 0 remain unclear. The aim of this study was to investigate the effects of high-dose bisphosphonates on tooth extraction socket healing by creating a murine model of BRONJ Stage 0-like lesions using 8-week-old female C57BL/6J mice. Zoledronic acid (Zol) was administered subcutaneously twice a week for 7 weeks at doses of 0.1 mg/kg/week (moderate dose; Zol-M), 0.5 mg/kg/week (high dose; Zol-H1), and 1.0 mg/kg/week (higher dose; Zol-H2). Saline was used as a control (VC). Both maxillary first molars were extracted 3 weeks after drug treatment. Maxillae, long bones, and sera were collected 4 weeks post-extraction (n = 7 mice/group). Microcomputed tomography, histological, immunohistochemical, and ELISA analyses were performed. A ceiling effect for Zol was noted at the Zol-H1 dose. Osseous healing of extraction sites was significantly impaired with increased necrotic bone and the number of empty lacunae in a Zol dose-dependent manner. Zol significantly decreased epithelial thickness, due to a decrease in thickness of the stratum spinosum, in both Zol-H1 and Zol-H2. Both Zol-H1 and Zol-H2 significantly suppressed the distribution of F4/80+ macrophages in the connective tissue of tooth extraction sockets, although gross healing appeared to be normal. Intriguingly, both Zol-H1 and Zol-H2 significantly increased the numbers of TRAP+ mononuclear cells and detached osteoclasts in the connective tissue and bone marrow of extraction sites compared to VC and Zol-M, correlated with serum TRAcP5b levels. The created murine model of BRONJ Stage 0-like lesions becoming more severe in a dose-dependent manner may help to understand the pathophysiology and histopathology of BRONJ Stage 0 in humans.

Altered immunolocalization of FGF23 in murine femora metastasized with human breast carcinoma MDA-MB-231 cells.

INTRODUCTION: After the onset of bone metastasis, tumor cells appear to modify surrounding microenvironments for their benefit, and particularly, the levels of circulating fibroblast growth factor (FGF) 23 in patients with tumors have been highlighted. MATERIALS AND METHODS: We have attempted to verify if human breast carcinoma MDA-MB-231 cells metastasized in the long bone of nu/nu mice would synthesize FGF23. Serum concentrations of calcium, phosphate (Pi) and FGF23 were measured in control nu/nu mice, bone-metastasized mice, and mice with mammary gland injected with MDA-MB-231 cells mimicking primary mammary tumors. RESULTS AND CONCLUSIONS: MDA-MB-231 cells revealed intense FGF23 reactivity in metastasized lesions, whereas MDA-MB-231 cells cultured in vitro or when injected into the mammary glands (without bone metastasis) showed weak FGF23 immunoreactivity. Although the bone-metastasized MDA-MB-231 cells abundantly synthesized FGF23, osteocytes adjacent to the FGF23-immunopositive tumors, unlike intact osteocytes, showed no FGF23. Despite significantly elevated serum FGF23 levels in bone-metastasized mice, there was no significant decrease in the serum Pi concentration when compared with the intact mice and mice with a mass of MDA-MB-231 cells in mammary glands. The metastasized femora showed increased expression and FGFR1 immunoreactivity in fibroblastic stromal cells, whereas femora of control mice showed no obvious FGFR1 immunoreactivity. Taken together, it seems likely that MDA-MB-231 cells synthesize FGF23 when metastasized to a bone, and thus affect FGFR1-positive stromal cells in the metastasized tumor nest in a paracrine manner.

Gene expression analysis of fresh extraction wounds prior to onset of bisphosphonate-related osteonecrosis of the jaw-like lesions in mice: A preliminary animal study.

Purpose The aim of the present study was to investigate the effects of chemotherapeutic/bisphosphonate combination therapy with tooth extraction on gene expression patterns of fresh extraction wounds during initial stages prior to their diagnosis as bisphosphonate-related osteonecrosis of the jaw (BRONJ)-like lesions in mice.Methods Female C57BL/6J mice were used. To create a high-prevalence BRONJ mouse model, combination therapy with the chemotherapy drug cyclophosphamide (CY) and zoledronic acid (ZA) was performed (CY/ZA). Both maxillary first molars were extracted 3 weeks after drug therapy. Saline was used as the control (VC). Soft tissues near the fresh extraction wounds were dissected at 72 h postextraction to investigate the gene expression patterns. Maxillae and long bones at 2 and 4 weeks postextraction were also analyzed.Results CY/ZA significantly increased the relative expression levels of IL-6 and decreased those of IL-10 and IGF-1 when compared with those in VC. Moreover, CY/ZA significantly reduced the relative expression levels of CCR-7, cxcl12, cxcr4, and CD105 when compared with those in VC, whereas the level of F4/80 was significantly increased by CY/ZA. Furthermore, CY/ZA significantly decreased the relative expression levels of VEGFA, VEGFB, and VEGFC at 72 h postextraction compared with those in VC.Conclusions Considering that the present study lacked adequate in vitro models, CY/ZA markedly changed the gene expression patterns associated with wound healing from the initial stages prior to onset of BRONJ-like lesions, which may help us to understand the pathophysiology of BRONJ in humans.

Effects of surface sub-micrometer topography following oxalic acid treatment on bone quantity and quality around dental implants in rabbit tibiae.

BACKGROUND: To explore the effects of topographical modification of titanium substrates at submicron level by oxalic acid treatment on bone quality and quantity around dental implants in rabbit tibiae. METHODS: A total of 60 blasted CP-grade IV titanium dental implants were used. Twenty-eight control implant surfaces were treated with a mixture of HCl/H2SO4, whereas 28 other test implant surfaces were treated with oxalic acid following HCl/H2SO4 treatment. Two randomly selected sets of control or test implants were placed in randomly selected proximal tibiae of 14 female Japanese white rabbits. Euthanasia was performed 4 and 8 weeks post-implant placement. Bone to implant contact (BIC), bone area fraction (BAF), ratios of mature and immature bone to total bone, and the amount and types of collagen fibers were evaluated quantitatively. Two control and two test implants were used to analyze surface characteristics. RESULTS: Treatment by oxalic acid significantly decreased Sa and increased Ra of test implant surfaces. BIC in test implants was increased without alteration of BAF and collagen contents at 4 and 8 weeks after implant placement when compared with control implants. The ratios of immature and mature bone to total bone differed significantly between groups at 4 weeks post-implantation. Treatment by oxalic acid increased type I collagen and decreased type III collagen in bone matrices around test implants when compared with control implants at 8 weeks after implant placement. The effects of topographical changes of implant surfaces induced by oxalic acid on BAF, mature bone, collagen contents, and type I collagen were significantly promoted with decreased immature bone formation and type III collagen in the later 4 weeks post-implantation. CONCLUSIONS: Treatment of implant surfaces with oxalic acid rapidly increases osseointegration from the early stages after implantation. Moreover, submicron topographical changes of dental implants induced by oxalic acid improve bone quality based on bone maturation and increased production of type I collagen surrounding dental implants in the late stage after implant placement.

Osteocytic Osteolysis in PTH-treated Wild-type and Rankl-/- Mice Examined by Transmission Electron Microscopy, Atomic Force Microscopy, and Isotope Microscopy.

To demonstrate the ultrastructure of osteocytic osteolysis and clarify whether osteocytic osteolysis occurs independently of osteoclastic activities, we examined osteocytes and their lacunae in the femora and tibiae of 11-week-old male wild-type and Rankl-/- mice after injection of human parathyroid hormone (PTH) [1-34] (80 µg/kg/dose). Serum calcium concentration rose temporarily 1 hr after PTH administration in wild-type and Rankl-/- mice, when renal arteries and veins were ligated. After 6 hr, enlargement of osteocytic lacunae was evident in the cortical bones of wild-type and Rankl-/- mice, but not so in their metaphyses. Von Kossa staining and transmission electron microscopy showed broadly demineralized bone matrix peripheral to enlarged osteocytic lacunae, which contained fragmented collagen fibrils and islets of mineralized matrices. Nano-indentation by atomic force microscopy revealed the reduced elastic modulus of the PTH-treated osteocytic perilacunar matrix, despite the microscopic verification of mineralized matrix in that region. In addition, 44Ca deposition was detected by isotope microscopy and calcein labeling in the eroded osteocytic lacunae of wild-type and Rankl-/- mice. Taken together, our findings suggest that osteocytes can erode the bone matrix around them and deposit minerals on their lacunar walls independently of osteoclastic activity, at least in the murine cortical bone. (J Histochem Cytochem 68: -XXX, 2020).

Distinct immunopathology in the early stages between different antiresorptives-related osteonecrosis of the jaw-like lesions in mice.

There is limited information about denosumab-related osteonecrosis of the jaw (DRONJ), unlike bisphosphonate-related ONJ (BRONJ). The mode of action is clearly different between denosumab and bisphosphonates. DRONJ occurs mainly following tooth extraction in cancer patients treated with the combination of denosumab and other drugs including chemotherapy. However, DRONJ animal models similar to these clinical situations have not been developed. The aims of this study were to 1) create a new model of high-prevalence chemotherapy/anti-RANKL antibody-related ONJ-like lesions to mimic patients receiving a denosumab/chemotherapy combination; and 2) compare the histopathological and immunopathological findings in the early stages of BRONJ-like and anti-RANKL antibody-related ONJ-like lesions. Cyclophosphamide (CY) and anti-mouse RANKL monoclonal antibody (mAb) or zoledronate combination therapy (CY/mAb and CY/ZA, respectively) was performed to create ONJ-like lesions in female C57BL/6J mice. Both maxillary first molars were extracted at 3 weeks after drug administration. The animals were euthanized at either 2 or 4 weeks after tooth extraction. Increased necrotic bone and empty lacunae with decreased living bone and osteocyte numbers were common histopathological findings in CY/mAb- and CY/ZA-induced impaired wound healing at 4 weeks after tooth extraction, and they were diagnosed as ONJ-like lesions based on validation of BRONJ and DRONJ in humans. In areas of impaired healing at 2 weeks post-extraction, decreases in angiogenesis and F4/80+LYVE-1- macrophages were noted as common immunopathological findings, although anti-angiogenesis was worse with CY/mAb than with CY/ZA. Interestingly, CY/mAb did not reduce F4/80+LYVE-1+ cells and normal lymphangiogenesis remained, whereas CY/ZA profoundly suppressed the larger size of F4/80+LYVE-1+ cells, similar to vessels with a concomitant decrease in lymphangiogenesis. Therefore, the distribution of the larger size of F4/80+LYVE-1+ cells differed in the early stages between different antiresorptive-induced ONJ-like lesions in conjunction with lymphangiogenesis, although the histopathological findings were similar. These findings suggest that the pathogenesis of BRONJ and DRONJ may differ due to the distributions of F4/80+LYVE-1+ tube-like-structured cells.

Medication-related osteonecrosis of the jaw-like lesions in rodents: A comprehensive systematic review and meta-analysis.

OBJECTIVE: The aim of this comprehensive systematic review and meta-analysis was to investigate the pathology and pathogenesis of medication-related osteonecrosis of the jaw (MRONJ) in rodents. BACKGROUND: Medication-related osteonecrosis of the jaw occurs in patients taking antiresorptive drugs, such as bisphosphonates and denosumab, and anti-angiogenesis agents. However, there is limited information about the pathology of MRONJ at the clinical level. Moreover, no information about the exact mechanisms of MRONJ is clinically available. MATERIALS AND METHODS: The PubMed, SCOPUS and Medline databases were used to search for relevant articles up to April 2018 by two independent reviewers. A systematic review and meta-analysis were performed. RESULTS: Of the 1841 studies, 10 articles met the eligibility criteria. The most commonly observed pathology of MRONJ-like lesions was exposed bone without epithelial coverage, decreases in the number of osteocytes and increases in necrotic bone with more empty lacunae. No definitive pathogenesis of MRONJ-like lesions was found. Both zoledronic acid (ZA) monotherapy and ZA/chemotherapeutic and/or dexamethasone combination therapy were significant high-risk factors for developing MRONJ-like lesions (P < 0.00001 and P < 0.0001, respectively). CONCLUSION: Based on rodent studies, common pathological findings were extracted in bisphosphonate-related ONJ (BRONJ)-like lesions, whereas no definitive pathogenesis was identified. There is no information about the pathology and pathogenesis of denosumab-related ONJ. These findings clearly suggest that accumulation of scientific evidence based on animal studies is absolutely necessary to explore the pathology and pathogenesis of MRONJ in humans. ZA administration would be a significant risk factor for developing BRONJ-like lesions.

Immunolocalization of podoplanin/E11/gp38, CD44, and endomucin in the odontoblastic cell layer of murine tooth germs.

In this study, we attempted to localize the immunoreactivities of podoplanin/E11/gp38 and CD44, a counterpart possessing a high affinity to podoplanin/E11/gp38, as well as endomucin-immunoreactive blood vessels in the regions of odontoblast layers and the underlying sub-odontoblastic layers in murine tooth germs. Endomucin-reactive small blood vessels were scattered throughout the dental papillae of the tooth germs at postnatal day 1 but came to be localized close to the odontoblast/sub-odontoblastic layers until day 3. After postnatal day 5, small blood vessels were seen in odontoblast cell layers, while blood vessels with relatively larger diameters were seen forming in sub-odontoblastic layers. Immunoreactivities of podoplanin/E11/gp38 and CD44 were not detectable in the cells of dental papillae facing the inner enamel epithelium at postnatal day 1. However, at around postnatal days 3-5, podoplanin/E11/gp38 was localized in the odontoblast layer but not in the sub-odontoblastic layer, whereas CD44 was observed in the sub-odontoblastic layer but not in the odontoblast layer. The exclusive immunolocalization of podoplanin/E11/gp38 and CD44 in the odontoblast layers and sub-odontoblastic layers was seen after postnatal day 3 of the tooth germs, when the mesenchymal cells of dental papillae have already differentiated into mature odontoblasts at the cusp tip. Taken together, it seems likely that endomucin-reactive small blood vessels extended to the podoplanin/E11/gp38-positive odontoblast layers, whereas endomucin-reactive large blood vessels were already present in CD44-immmunopositive sub-odontoblastic layer, indicating the cellular regulation on the vascularization of endomucin-reactive endothelial cells during odontogenesis of the tooth germs.

Systemic administration of quality- and quantity-controlled PBMNCs reduces bisphosphonate-related osteonecrosis of jaw-like lesions in mice.

BACKGROUND: Definitive treatment strategies for bisphosphonate-related osteonecrosis of the jaw (BRONJ) have not been developed. Cell-based therapy is an attractive treatment method for intractable diseases in the medical and dental fields; however, approval has been challenging in dentistry. Recently, we developed quality- and quantity (QQ)-controlled peripheral blood mononuclear cells (PBMNCs) that have anti-inflammatory and pro-angiogenesis effects. The aim of this study was to investigate the effects of QQ-controlled PBMNC transplantation on BRONJ-like lesions in mice. METHODS: To create high-prevalence BRONJ-like lesions, cyclophosphamide (CY) and zoledronate (ZA) were used with tooth extraction. Drug treatment was performed for 5 weeks. QQ-controlled PBMNC transplantation was performed immediately following tooth extraction of both maxillary first molars at 3 weeks after drug administration. Mice were euthanized at 2 weeks post-extraction. Histomorphometric and immunohistochemical analyses, microcomputed tomography assessment, and quantitative polymerase chain reaction evaluation were conducted using maxillae and long bones. RESULTS: ZA effects on long bones were noted, regardless of CY. Severely inhibited osseous and soft tissue wound healing of tooth extraction sockets was induced by CY/ZA combination therapy, which was diagnosed as BRONJ-like lesions. QQ-controlled PBMNC transplantation reduced BRONJ-like lesions by improving soft tissue healing with increased M1 and M2 macrophages and enhanced neovascularization in the connective tissue of tooth extraction sockets. QQ-controlled PBMNC transplantation also reduced inflammation by decreasing polymorphonuclear cells and TNF-α expression in the tooth extraction sockets. Additionally, QQ-controlled PBMNC transplantation partially improved osseous healing of tooth extraction sockets. Interestingly, only 20,000 QQ-controlled PBMNCs per mouse induced these transplantation effects. QQ-controlled PBMNC transplantation did not affect the systemic microenvironment. CONCLUSIONS: Our findings suggest that transplantation of a small amount of QQ-controlled PBMNCs may become novel therapeutic or prevention strategies for BRONJ without any adverse side effects.

Histochemical examination on principal collagen fibers in periodontal ligaments of ascorbic acid-deficient ODS-od/od rats.

In this study, we aimed to clarify the role of ascorbic acid in collagen synthesis in periodontal ligaments using osteogenic disorder Shionogi (ODS)/ShiJcl-od/od rats lacking L-gulonolactone oxidase. These rats cannot synthesize ascorbic acid in vivo. Eight-week-old ODS/ShiJcl-od/od male rats were administered ascorbic acid solution at a concentration of 200 mg/dL (control group, n = 6) or ascorbic acid solution at concentration of 0.3 mg/dL (insufficient group, n = 12). Six rats of the insufficient group were then given with ascorbic acid solution at concentration of 200 mg/dL for additional 3 weeks (rescued group, n = 6), and then, their mandibles were histochemically examined. Consequently, the insufficient group specimens were seen to possess fewer collagen fibers, and silver impregnation revealed numerous fine, reticular fiber-like fibrils branching off from collagen in the periodontal ligaments. In control group, faint immunoreactivities for matrix metalloproteinase (MMP)2 and cathepsin H were seen in the periphery of blood vessels and throughout the ligament, respectively. In contrast, in the insufficient group, intense MMP2-immunoreactivity was observed to be associated with collagen fibrils in the periodontal ligaments, and cathepsin H-immunopositivity was seen in ligamentous cells. The rescued group showed abundant collagen fibers filling the periodontal ligament space. Under transmission electron microscopy, ligamentous fibroblasts incorporated collagen fibrils into tubular endosomes/lysosomes while simultaneously synthesizing collagen fibril bundles. Thus, ascorbic acid insufficiency affected the immunolocalization of cathepsin H and MMP2; however, ligamentous fibroblasts appear to possess the potential to synthesize collagen fibers when supplied with ascorbic acid.

Medication-related osteonecrosis of the jaw: A literature review.

BACKGROUND: Antiresorptive agents such as bisphosphonates and denosumab, as well as angiogenesis inhibitors, may induce medication-related osteonecrosis of the jaw (MRONJ). However, the exact mechanisms of MRONJ are unclear and definitive treatment strategies have not yet been developed. Moreover, the aging population requiring antiresorptive agents and angiogenesis inhibitors has been increasing worldwide. Therefore, the aim of this literature review was to introduce the latest information on MRONJ. The epidemiology, triggering factors, risk factors, drug holiday, pathoetiology and treatment strategies for each drug-induced ONJ were investigated by conducting a PubMed search. HIGHLIGHT: The prevalence and incidence of ONJ were very low. Some mechanisms of ONJ have been identified, although they were not definitive. Novel treatment strategies have been proposed in basic and clinical research. Several factors, including age and the administration duration of bisphosphonates, are risks for the development of bisphosphonate-related ONJ (BRONJ). Dental implant therapy and peri-implantitis could become risk factors of BRONJ, regardless of the onset timing of bisphosphonates. No reliable information about ONJ induced by denosumab and angiogenesis inhibitors was found. CONCLUSION: Caution should be taken when dental treatment including implant therapy is performed in patients receiving bisphosphonates, denosumab, and angiogenesis inhibitors. There is limited scientific evidence regarding the relationship between MRONJ and older age. Further ONJ-related research on the aging population is required to manage the treatment of such diseases in older people in the future.

Prevalence of bisphosphonate-related osteonecrosis of the jaw-like lesions is increased in a chemotherapeutic dose-dependent manner in mice.

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) worsens oral health-related quality of life. Most BRONJ occurs in multiple myeloma or metastatic breast cancer patients treated with bisphosphonate/chemotherapeutic combination therapies. Cyclophosphamide (CY), an alkylating chemotherapeutic drug, is used to treat multiple myeloma, although its use has been recently reduced. The aim of this study was to clarify the effects of CY dose on tooth extraction socket healing when CY is used with or without bisphosphonate in mice. Low-dose CY (50 mg/kg; CY-L), moderate-dose CY (100 mg/kg; CY-M), high-dose CY (150 mg/kg; CY-H), and bisphosphonate [Zometa (ZA): 0.05 mg/kg] were administered for 7 weeks. Each dose of CY and ZA in combination was also administered for 7 weeks. Both maxillary first molars were extracted at 3 weeks after the initiation of drug administration. Euthanasia was performed at 4 weeks post-extraction. Gross wound healing, microcomputed tomography analysis, histomorphometry, and immunohistochemistry were used to quantitatively evaluate osseous and soft tissue wound healing of tooth extraction sockets. ZA monotherapy induced no BRONJ-like lesions in mice. CY monotherapy rarely induced open wounds, though delayed osseous wound healing occurred in a CY dose-dependent manner. In contrast, CY/ZA combination therapy prevalently induced BRONJ-like lesions with compromised osseous and soft tissue healing in a CY dose-dependent manner. Interestingly, anti-angiogenesis was noted regardless of CY dose and ZA administration, even though only CY-M/ZA and CY-H/ZA combination therapies induced BRONJ-like lesions. Our findings suggest that high-dose CY may be associated with the development of BRONJ following tooth extraction only when CY is used together with ZA. In addition to anti-angiogenesis, other factors may contribute to the pathoetiology of BRONJ.

Transplantation of Noncultured Stromal Vascular Fraction Cells of Adipose Tissue Ameliorates Osteonecrosis of the Jaw-Like Lesions in Mice.

The precise pathoetiology and effective treatment strategies for bisphosphonate-related osteonecrosis of the jaw (BRONJ) remain unknown. Transplantation of noncultured stromal vascular fraction (SVF) cells has been shown to be a useful method for regenerative medicine in place of stem cell therapy. This study investigated the effects of noncultured SVF transplantation on tooth extraction socket healing in mice. Both chemotherapeutic/bisphosphonate combination therapy for 7 weeks and tooth extraction of maxillary first molars at 3 weeks after drug administration were performed using female C57BL/6J mice. Osseous and soft tissue wound healing were validated at 4 weeks postextraction using gross wound healing and histomorphometry. Here, we created a new animal model of high-prevalence ONJ-like lesions that mimic human progression, because human ONJ mainly occurs in female patients taking both chemotherapeutic and bisphosphonate following tooth extraction. Moreover, mice with chemotherapeutic and bisphosphonate combination therapy for 5 weeks received SVF transplantation just after tooth extraction at 3 weeks post-drug administration. Euthanasia was performed at 2 weeks postextraction to assess the transplantation effects on wound healing using gross wound healing, histomorphometry, immunohistomorphometry, quantitative real-time polymerase chain reaction, and microcomputed tomography. We showed that systemic transplantation of noncultured SVF cells ameliorates ONJ-like lesions by improving both osseous and soft tissue healing of tooth extraction sockets. SVF therapy significantly increased blood vessels and the ratio of M2/M1 macrophages. In addition, SVF transplantation reduced the increases in tartrate-resistant acid phosphatase-positive (TRAP+ ) mononuclear cells (MNCs) and nonattached osteoclasts from the bone surface, which were significantly detected in the connective tissue of tooth extraction sockets and bone marrow by chemotherapeutic/bisphosphonate combination therapy. Our findings suggest that transplantation of noncultured SVF cells is a suitable treatment for BRONJ. Abnormal TRAP+ MNCs and nonattached osteoclasts in systemic and local environments may contribute to the development of BRONJ. © 2017 American Society for Bone and Mineral Research.

Effect of anti-angiogenesis induced by chemotherapeutic monotherapy, chemotherapeutic/bisphosphonate combination therapy and anti-VEGFA mAb therapy on tooth extraction socket healing in mice.

Osteonecrosis of the jaw (ONJ), which is a rare but severe adverse effect, mainly occurs in oncology patients receiving chemotherapeutic agents and bisphosphonates. However, the combined impact of chemotherapy and bisphosphonates on wound healing after tooth extraction remains unknown. The aim of this study was to determine the precise etiology of ONJ induced by chemotherapy and bisphosphonate combination therapy. Mice received zoledronate (ZA) monotherapy, cyclophosphamide (CY) monotherapy or CY/ZA combination therapy. The maxillary first molars were extracted 3 weeks after the initiation of drug treatment. Moreover, antivascular endothelial growth factor A (VEGFA) monoclonal antibody (mAb) was administered once every 2 days just after tooth extraction for 2 weeks. Soft and hard tissue wound healing was evaluated 2 and 4 weeks post-extraction using histomorphometry, microcomputed tomography and immunohistochemistry. ZA monotherapy did not induce impaired oral wound healing and ONJ-like lesions 2 and 4 weeks post-extraction, respectively. Tooth extraction socket healing worsened with severe anti-angiogenesis by CY monotherapy and CY/ZA combination therapy 2 weeks post-extraction. However, CY monotherapy rarely induced ONJ-like lesions with severe angiogenesis suppression, whereas CY/ZA combination therapy frequently induced ONJ-like lesions with severe angiogenesis inhibition 4 weeks post-extraction. Interestingly, anti-VEGFA mAb therapy delayed osseous wound healing with normal soft tissue wound healing of tooth extraction sockets, although this therapy significantly suppressed blood vessel formation. Our findings suggest that anti-angiogenesis alone is not the main cause of ONJ-like lesions induced by CY/ZA combination therapy. The combination of suppressed osteoclasts and anti-angiogenesis, in addition to other risk factors such as chemotherapy, may contribute to the development of ONJ.

Cyclic mechanical stretch contributes to network development of osteocyte-like cells with morphological change and autophagy promotion but without preferential cell alignment in rat.

Osteocytes play important roles in controlling bone quality as well as preferential alignment of biological apatite c-axis/collagen fibers. However, the relationship between osteocytes and mechanical stress remains unclear due to the difficulty of three-dimensional (3D) culture of osteocytes in vitro. The aim of this study was to investigate the effect of cyclic mechanical stretch on 3D-cultured osteocyte-like cells. Osteocyte-like cells were established using rat calvarial osteoblasts cultured in a 3D culture system. Cyclic mechanical stretch (8% amplitude at a rate of 2 cycles min-1) was applied for 24, 48 and 96 consecutive hours. Morphology, cell number and preferential cell alignment were evaluated. Apoptosis- and autophagy-related gene expression levels were measured using quantitative PCR. 3D-cultured osteoblasts became osteocyte-like cells that expressed osteocyte-specific genes such as Dmp1, Cx43, Sost, Fgf23 and RANKL, with morphological changes similar to osteocytes. Cell number was significantly decreased in a time-dependent manner under non-loaded conditions, whereas cyclic mechanical stretch significantly prevented decreased cell numbers with increased expression of anti-apoptosis-related genes. Moreover, cyclic mechanical stretch significantly decreased cell size and ellipticity with increased expression of autophagy-related genes, LC3b and atg7. Interestingly, preferential cell alignment did not occur, irrespective of mechanical stretch. These findings suggest that an anti-apoptotic effect contributes to network development of osteocyte-like cells under loaded condition. Spherical change of osteocyte-like cells induced by mechanical stretch may be associated with autophagy upregulation. Preferential alignment of osteocytes induced by mechanical load in vivo may be partially predetermined before osteoblasts differentiate into osteocytes and embed into bone matrix.

A paradigm shift for bone quality in dentistry: A literature review.

PURPOSE: The aim of this study was to present the current concept of bone quality based on the proposal by the National Institutes of Health (NIH) and some of the cellular and molecular factors that affect bone quality. STUDY SELECTION: This is a literature review which focuses on collagen, biological apatite (BAp), and bone cells such as osteoblasts and osteocytes. RESULTS: In dentistry, the term "bone quality" has long been considered to be synonymous with bone mineral density (BMD) based on radiographic and sensible evaluations. In 2000, the NIH proposed the concept of bone quality as "the sum of all characteristics of bone that influence the bone's resistance to fracture," which is completely independent of BMD. The NIH defines bone quality as comprising bone architecture, bone turnover, bone mineralization, and micro-damage accumulation. Moreover, our investigations have demonstrated that BAp, collagen, and bone cells such as osteoblasts and osteocytes play essential roles in controlling the current concept of bone quality in bone around hip and dental implants. CONCLUSION: The current concept of bone quality is crucial for understanding bone mechanical functions. BAp, collagen and osteocytes are the main factors affecting bone quality. Moreover, mechanical loading dynamically adapts bone quality. Understanding the current concept of bone quality is required in dentistry.

Histochemical Examination on Periodontal Tissues of Klotho-Deficient Mice Fed With Phosphate-Insufficient Diet.

To elucidate which of elevated serum concentration of inorganic phosphate (Pi) or disrupted signaling linked to αklotho/fibroblast growth factor 23 (FGF23) is a predominant regulator for senescence-related degeneration seen in αKlotho-deficient mice, we have examined histological alteration of the periodontal tissues in the mandibular interalveolar septum of αKlotho-deficient mice fed with Pi-insufficient diet. We prepared six groups of mice: wild-type, kl/kl, and αKlotho-/- mice with normal diet or low-Pi diet. As a consequence, kl/klnorPi and αKlotho-/-norPi mice showed the same abnormalities in periodontal tissues: intensely stained areas with hematoxylin in the interalveolar septum, dispersed localization of alkaline phosphatase-positive osteoblasts and tartrate-resistant acid phosphatase-reactive osteoclasts, and accumulation of dentin matrix protein 1 in the osteocytic lacunae. Although kl/kllowPi mice improved these histological abnormalities, αKlotho-/- lowPi mice failed to normalize those. Gene expression of αKlotho was shown to be increased in kl/kl lowPi specimens. It seems likely that histological abnormalities of kl/kl mice have been improved by the rescued expression of αKlotho, rather than low concentration of serum Pi. Thus, the histological malformation in periodontal tissues in αKlotho-deficient mice appears to be due to not only increased concentration of Pi but also disrupted αklotho/FGF23 signaling.