Shinichiro Kuroshima

Generalized exacerbation of systemic allergic dermatitis due to zinc patch test and dental treatments.

A 37-year-old Japanese man was referred with a one-year history of multiple pruritic eruptions covering his entire body. The skin lesions had been refractory to topical corticosteroids and anti-histamines. Examination showed an oedematous erythema with lesions 3–10 mm in diameter that were distributed over his entire body. A detailed history revealed that the patient had had dental fillings 3 months prior to the onset of the rash. We suspected systemic allergic dermatitis because of the dental fillings. We performed patch test with a metal series (Torii Pharmaceutical Co., Ltd., Tokyo, Japan) consisting of aluminium chloride, gold chloride, tin chloride, iron chloride, platinum chloride, palladium chloride, indium chloride, manganese chloride, silver bromide, cobalt chloride, potassium dichromate, nickel sulfate, and zinc chloride. He developed a positive (+) reaction (ICDRG criteria) to zinc chloride on D2 (Table 1) and this persisted to D7. During patch testing, the skin lesions dramatically flared at previous lesion sites (Fig. 1). Serum zinc concentration was within normal limits; there was an eosinophilia. Lymphocyte stimulation test revealed a reaction to zinc chloride with a stimulation index of 518% (normal is <180%). A skin biopsy from erythema lesion on the back showed spongiosis and perivascular lymphocytic infiltration. Based on these clinical and histological findings, we diagnosed his pruritic eruption as systemic allergic dermatitis because of zinc. Dental inspection showed that he had 11 teeth with zinc-containing metal fillings. We have been removing the fillings one by one, but with each

Optimally oriented grooves on dental implants improve bone quality around implants under repetitive mechanical loading

The aim was to investigate the effect of groove designs on bone quality under controlled-repetitive load conditions for optimizing dental implant design. Anodized Ti-6Al-4V alloy implants with -60° and +60° grooves around the neck were placed in the proximal tibial metaphysis of rabbits. The application of a repetitive mechanical load was initiated via the implants (50N, 3Hz, 1800 cycles, 2days/week) at 12weeks after surgery for 8weeks. Bone quality, defined as osteocyte density and degree of biological apatite (BAp) c-axis/collagen fibers, was then evaluated. Groove designs did not affect bone quality without mechanical loading; however, repetitive mechanical loading significantly increased bone-to-implant contact, bone mass, and bone mineral density (BMD). In +60° grooves, the BAp c-axis/collagen fibers preferentially aligned along the groove direction with mechanical loading. Moreover, osteocyte density was significantly higher both inside and in the adjacent region of the +60° grooves, but not -60° grooves. These results suggest that the +60° grooves successfully transmitted the load to the bone tissues surrounding implants through the grooves. An optimally oriented groove structure on the implant surface was shown to be a promising way for achieving bone tissue with appropriate bone quality. This is the first report to propose the optimal design of grooves on the necks of dental implants for improving bone quality parameters as well as BMD. The findings suggest that not only BMD, but also bone quality, could be a useful clinical parameter in implant dentistry. STATEMENT OF SIGNIFICANCE Although the paradigm of bone quality has shifted from density-based assessments to structural evaluations of bone, clarifying bone quality based on structural bone evaluations remains challenging in implant dentistry. In this study, we firstly demonstrated that the optimal design of dental implant necks improved bone quality defined as osteocytes and the preferential alignment degree of biological apatite c-axis/collagen fibers using light microscopy, polarized light microscopy, and a microbeam X-ray diffractometer system, after application of controlled mechanical load. Our new findings suggest that bone quality around dental implants could become a new clinical parameter as well as bone mineral density in order to completely account for bone strength in implant dentistry.

Ultrastructural alterations of osteocyte morphology via loaded implants in rabbit tibiae.

Osteocytes are crucial cells that control bone responses to mechanical loading. However, the effects of mechanical loading on osteocytes around dental implants are unclear. The aim of this study was to investigate whether mechanical loading via bone-integrated implants influences osteocyte number and morphology in the surrounding bone. Fourteen anodized Ti-6Al-4V alloy dental implants were placed in seven Japanese white rabbits, and implants in each rabbit were subjected to mechanical loading (50N, 3Hz for 1800 cycles, 2 days/week) along the implant long axis. Eight weeks after the initiation of loading, histomorphometric analysis and microcomputed tomography were performed. Scanning electron microscopy (SEM) was also performed with an acid etching technique using longitudinal and cross-sectional specimens. More bone formation around loaded implants was noted. In the implant neck, osteocytes tended to be more spherical with increased dendrite processes around loaded implants, while spindle-shaped osteocytes without increased dendrite processes were observed around unloaded implants in both longitudinal and cross-sectional images. In the bottom area, morphological changes in osteocytes were observed around loaded implants; however, dendrite processes did not differ in longitudinal or cross-sectional images, regardless of mechanical loading. These findings indicate that increased osteocyte numbers and developed dendrite processes are associated with anabolic bone responses to mechanical loading. The combination of acid etching and SEM imaging is a useful technique to assess ultrastructural osteocyte morphology around dental implants.

Parathyroid hormone related to bone regeneration in grafted and nongrafted tooth extraction sockets in rats.

Objective:The quality and quantity of bone formed in tooth extraction sockets impact implant therapy. Therefore, the establishment of a new approach to enhance bone formation and to minimize bone resorption is important for the success of implant therapy. In this study, we investigated whether intermittent parathyroid hormone (PTH) therapy enhanced bone formation in grafted sockets. Methods:Tooth extractions of the maxillary first molars were performed in rats, and the sockets were grafted with xenograft. Intermittent PTH was administered either for 7 days before extractions, for 14 days after extractions, or both. The effect of PTH therapy on bone formation in the grafted sockets was assessed using microcomputed tomography at 14 days after extractions. Results:PTH therapy for 7 days before extractions was not effective to augment bone fill, whereas PTH therapy for 14 days after operation significantly augmented bone formation in the grafted sockets. Conclusions:Intermittent PTH therapy starting right after tooth extractions significantly enhanced bone fill in the grafted sockets, suggesting that PTH therapy can be a strong asset for the success of the ridge preservation procedure.

Structural and Qualitative Bone Remodeling Around Repetitive Loaded Implants in Rabbits.

BACKGROUND Bone mechanical function is regulated by bone quality and bone mineral density (BMD) that reflect bone strength. The preferential alignment of biological apatite (BAp) c-axis/collagen fibers and osteocytes is a determinant factor of bone quality. However, the effect of mechanical loading on bone quality around dental implants is unclear. PURPOSE The aim of this study was to clarify the effects of mechanical loading on osseointegration, bone volume BMD, and bone quality around dental implants. MATERIALS AND METHODS Twenty anodized Ti-6Al-4V alloy implants (KYOCERA Co., Kyoto, Japan) were placed in the proximal tibial metaphysis of 10 rabbits. Twelve weeks after surgery, mechanical loading was applied along the long axis of the implant (50 N, 3 Hz, 1,800 cycles, 2 days/week) for 8 weeks. Osseointegration, bone volume, BMD, and bone quality were evaluated using light microscopy, microcomputed tomography, polarized light microscopy, and microbeam X-ray diffractometer. RESULTS Mechanical loading increased osseointegration, bone volume, and BMD. Bone quality around dental implant was altered with increased osteocyte numbers and the preferential alignment direction and degree of BAp c-axis/collagen fibers. CONCLUSIONS These findings suggest that mechanical loading effectively induces bone anabolic responses around dental implants. Altered bone quality may upregulate bone strength, contributing to long-term implant stability.

Effects of mechanical repetitive load on bone quality around implants in rat maxillae

Greater understanding and acceptance of the new concept “bone quality”, which was proposed by the National Institutes of Health and is based on bone cells and collagen fibers, are required. The novel protein Semaphorin3A (Sema3A) is associated with osteoprotection by regulating bone cells. The aims of this study were to investigate the effects of mechanical loads on Sema3A production and bone quality based on bone cells and collagen fibers around implants in rat maxillae. Grade IV-titanium threaded implants were placed at 4 weeks post-extraction in maxillary first molars. Implants received mechanical loads (10 N, 3 Hz for 1800 cycles, 2 days/week) for 5 weeks from 3 weeks post-implant placement to minimize the effects of wound healing processes by implant placement. Bone structures, bone mineral density (BMD), Sema3A production and bone quality based on bone cells and collagen fibers were analyzed using microcomputed tomography, histomorphometry, immunohistomorphometry, polarized light microscopy and birefringence measurement system inside of the first and second thread (designated as thread A and B, respectively), as mechanical stresses are concentrated and differently distributed on the first two threads from the implant neck. Mechanical load significantly increased BMD, but not bone volume around implants. Inside thread B, but not thread A, mechanical load significantly accelerated Sema3A production with increased number of osteoblasts and osteocytes, and enhanced production of both type I and III collagen. Moreover, mechanical load also significantly induced preferential alignment of collagen fibers in the lower flank of thread B. These data demonstrate that mechanical load has different effects on Sema3A production and bone quality based on bone cells and collagen fibers between the inside threads of A and B. Mechanical load-induced Sema3A production may be differentially regulated by the type of bone structure or distinct stress distribution, resulting in control of bone quality around implants in jaw bones.

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.

Medication-related osteonecrosis of the jaw; what should we do as prosthodontists?

Medication-related osteonecrosis of the jaw (MRONJ), which is a rare but severe impairment of oral wound healing in patients taking antiresorptive drugs, including bisphosphonates (BPs) and denosumab, mainly occurs after tooth extraction [1]. Due to their pharmacological action, oral and intravenous BPs have been widely used to treat osteoporosis, bone metastases of solid tumors, multiple myeloma and Paget’s disease in Japan and other countries [2]. Denosumab, which is a human monoclonal antibody against the receptor activator of nuclear factor-kB ligand (RANKL), has recently been approved for osteoporosis and malignant therapies in Japan. Denosumab is also antiresorptive, but has a different pharmacological action than BPs in that it binds to RANK, and targets both bone resorbing osteoclasts and pre-osteoclasts [3].

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.

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.