MDPI AG Acta Medica Okayama 2073-4360 18 7 2026 Effect of Universal Adhesives on Resin Cement–Fiber Post–Core Materials 810 EN Masao Irie Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Masahiro Okada Department of Dental Biomaterials, Graduate School of Dentistry, Tohoku University Yukinori Maruo Department of Prosthodontics, Okayama University Kenraro Akiyama Department of Occlusal and Oral Functional Rehabilitation, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Kumiko Yoshihara Health Research Institute, National Institute of Advanced Industrial Science and Technology Akimasa Tsujimoto Department of Operative Dentistry, School of Dentistry, Aichi Gakuin University Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University This study evaluated eleven resin cements used as core build-up materials by examining the following properties: (a) push-out force between root dentin and the fiber post; (b) pull-out force between the fiber post and the core build-up material; (c) shear bond strength of the resin cement to root dentin; (d) flexural strength of the resin cement; and (e) flexural modulus of elasticity of the resin cement. The purpose of this investigation was to clarify the relationships between recently available universal adhesives, core build-up materials, resin cements, and fiber posts. All experiments were performed at two evaluation periods: after 1 day of water storage (Base) and after 20,000 thermocycles (TC 20k). For the push-out test, simulated post spaces were prepared in single-rooted human premolars. The specimens were sectioned perpendicular to the long axis into 2 mm-thick slices and then subjected to push-out testing to assess the bond strength of the dentin–resin cement–fiber post complex. No significant differences in bonding performance were found between Base and TC 20k. These findings suggest that universal adhesives used for pretreatment of multiple substrates in fiber post cementation can provide not only strong but also durable adhesion over time. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 2452-199X 57 2026 Robust adhesion between solid-state hydroxyapatite and bone tissue through surface demineralization 632 645 EN Shichao Xie Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Masahiro Okada Division of Biomaterials Science and Engineering, Graduate School of Dentistry, Tohoku University Haruyuki Aoyagi Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Akihisa Otaka Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Xiaofeng Yang Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Takayoshi Nakano Division of Materials and Manufacturing Science, Graduate School of Engineering, The University of Osaka Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Objective: Current bone adhesives typically lack adequate mechanical strength, long-term stability, or biocompatibility. To address these limitations, we designed a new adhesion strategy using a solid-state hydroxyapatite (HAp) adhesive in combination with bone surface demineralization.<br> Methods: Solid-state HAp adhesives were synthesized via wet chemical precipitation and heat treatment. Cortical bone specimens were partially demineralized with phosphoric acid (H3PO4) or ethylenediaminetetraacetic acid (EDTA), and characterized using scanning electron microscopy (SEM) and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR). Shear adhesion strength of HAp to demineralized bone was measured over time. In vivo fixation was assessed in rats using micro-computed tomography and histology. Statistical analysis used Tukey-Kramer tests after normality and variance checks.<br> Results: Although the HAp adhesive failed to adhere to non-demineralized bone, effective adhesion was achieved on the surface-demineralized bone tissue. Shear adhesion strength was significantly higher in EDTA-treated samples (238.4 kPa at 10 h) compared to H3PO4-treated samples (102.9 kPa at 1 h), with performance correlating with demineralization depth. ATR-FTIR and SEM analyses revealed that EDTA preserved collagen's triple-helix structure and free water content, both enhancing adhesion. Animal experiments confirmed stable fixation of HAp adhesive to demineralized bone tissue.<br> Conclusions: Surface demineralization enabled strong adhesion of the solid-state HAp adhesive to bone by exposing collagen swollen with water. Adhesion strength was influenced by structural changes in the demineralized layer, and the adhesive provided stable in vivo fixation, supporting its potential for bone-anchored biomedical applications. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 2772-5022 5 2 2025 Amelioration of Cd-induced bone deterioration by orally administered calcium phosphate 101482 EN Ping-chin Sung Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Ahmad Bikharudin Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Masahiro Okada Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Randa Musa Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Kenta Uchida Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Akihisa Otaka Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Tadaaki Matsusaka Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University Aira Matsugaki Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University Takayoshi Nakano Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Cadmium (Cd) is a heavy metal that accumulates in the body, primarily through daily grain intake, and has a high affinity for bone, leading to skeletal diseases such as osteomalacia and fractures. Hydroxyapatite (HAp), a major bone mineral component, is highly pH-sensitive and is known to incorporate Cd, as observed in studies of Itai-itai disease. Based on these findings, we hypothesized that HAp could serve as an effective oral detoxification material for heavy metals. This study investigated the efficacy of orally administered HAp in inhibiting Cd-induced changes in bone physical and chemical properties, comparing its effects to those of activated charcoal (AC), a common detoxifying agent. Six-week-old male ICR mice were exposed to cadmium via drinking water containing CdCl2 and subsequently given diets containing either HAp or AC for four weeks. Three-point bending tests, micro-CT analysis, and histological observations of the femurs demonstrated that mice receiving HAp exhibited improved mechanical strength and enhanced bone quality protection compared to the control and other Cd-treated groups. Activated charcoal also contributed to bone quality improvement at low concentrations, but its effect diminished at high concentrations. These results suggest that the oral administration of HAp may be a promising therapeutic strategy for suppressing cadmium-induced osteomalacia. No potential conflict of interest relevant to this article was reported.

Elsevier BV Acta Medica Okayama 0304-3894 487 2025 Co-precipitating calcium phosphate as oral detoxification of cadmium 137307 EN Ahmad Bikharudin Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Masahiro Okada Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Ping-chin Sung Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Bone-eating (also known as osteophagia), found in wild animals, is primarily recognized as a means to supplement phosphorus and calcium intake. Herein, we describe a novel function of bone-eating in detoxifying heavy metal ions through the dissolution and co-precipitation of bone minerals as they travel through the gastrointestinal (GI) tract. In this study, cadmium (Cd), a heavy metal ion, served as a toxic model. We demonstrated that hydroxyapatite (HAp), the major calcium phosphate (CaP) in bone, dissolves in the stomach and acts as a co-precipitant in the intestine for Cd detoxification. We compared HAp to a common antidote, activated charcoal (AC), which did not precipitate within the GI tract. In vitro experiments showed that HAp dissolves under acidic conditions and, upon return to a neutral environment, efficiently re-sequesters Cd. Similarly, oral administration of HAp effectively prevented Cd absorption and accumulation, resulting in enhanced Cd excretion in the feces when compared to AC. A co-precipitating CaP in the GI tract could serve as an excellent detoxification system, as it helps prevent the accumulation of toxic substances and aids in developing appropriate strategies to reduce tissue toxicity. Moreover, understanding this detoxification system would be a valuable indicator for designing efficient detoxification materials. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1996-1944 18 9 2025 Initial Bonding Performance to CAD/CAM Restorative Materials: The Impact of Stepwise Concentration Variation in 8-Methacryloxyoctyl Trimethoxy Silane and 3-Methacryloxypropyl Trimethoxy Silane on Feldspathic Ceramic, Lithium Disilicate Glass-Ceramic, and Polymer-Infiltrated Ceramic 1983 EN Yukinori Maruo Department of Prosthodontics, Okayama University Miho Kuwahara Department of Occlusal and Oral Functional Rehabilitation, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kumiko Yoshihara Health Research Institute, National Institute of Advanced Industrial Science and Technology Masao Irie Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Noriyuki Nagaoka Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Dental School Mai Yoshizane Department of Occlusal and Oral Functional Rehabilitation, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Takuya Matsumoto Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Kentaro Akiyama Department of Occlusal and Oral Functional Rehabilitation, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences This study investigated the effects of varying concentrations of two distinct silane agents, 8-methacryloxyoctyl trimethoxy silane (8-MOTS) and 3-methacryloxypropyl trimethoxy silane (γ-MPTS), on their initial bonding efficacy to feldspathic ceramic (FC), lithium disilicate glass-ceramic (LD) and polymer-infiltrated ceramic (PIC) specimens, in 10% increments for concentrations ranging from 10% to 40%. Shear bond strengths between the ceramic substrates and the luting material were assessed following 24 h incubation in distilled water. For FC, the median value of shear bond strength peaked at 20% of γ-MPTS (7.4 MPa), while 8-MOTS exhibited a concentration-dependent increase, reaching its highest value at 40% (13.1 MPa). For LD, γ-MPTS above 10% yielded similar strength median values (10.2 MPa), whereas 8-MOTS at 30% (15.8 MPa) and 40% (13.4 MPa) yielded higher strength values than at 10% (2.9 MPa) and 20% (4.1 MPa), with the highest median value exhibited at 30%. For PIC, both γ-MPTS and 8-MOTS demonstrated similarly low bond strength values which were not significantly different from the non-silane-treated specimens. When applied on silica-based FC and LD, silane revealed a concentration-dependent bonding effect, with 8-MOTS exhibiting superior bond strength to γ-MPTS. However, PIC, characterized by a high inorganic filler content, demonstrated limited bondability with both silanes. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2073-4360 16 16 2024 Long-Term Bonding Performance of One-Bottle vs. Two-Bottle Bonding Agents to Lithium Disilicate Ceramics 2266 EN Masao Irie Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Masahiro Okada Department of Dental Biomaterials, Tohoku University Graduate School of Dentistry Yukinori Maruo Department of Prosthodontics, Okayama University Hospital Goro Nishigawa Department of Prosthodontics, Okayama University Hospital Takuya Matsumoto Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences The aim of this study was to compare the long-term bonding performance to lithium disilicate (LDS) ceramic between one-bottle and two-bottle bonding agents. Bonding performance was investigated under these LDS pretreatment conditions: with hydrofluoric acid (HF) only, without HF, with a two-bottle bonding agent (Tokuyama Universal Bond II) only. Shear bond strengths between LDS and nine resin cements (both self-adhesive and conventional adhesive types) were measured at three time periods: after one-day water storage (Base), and after 5000 and 20,000 thermocycles (TC 5k and TC 20k respectively). Difference in degradation between one- and two-bottle bonding agents containing the silane coupling agent was compared by high-performance liquid chromatography. With HF pretreatment, bond strengths were not significantly different among the three time periods for each resin cement. Without HF, ESTECEM II and Super-Bond Universal showed significantly higher values than others at TC 5k and TC 20k when treated with the recommended bonding agents, especially at TC 20k. Difference in degradation between one- and two-bottle bonding agents containing the silane coupling agent was compared by high-performance liquid chromatography (HPLC). For both cements, these values at TC 20k were also not significantly different from pretreatment with only Tokuyama Universal Bond II. For LDS, long-term bond durability could be maintained by pretreatment with Tokuyama Universal Bond II instead of the hazardous HF. No potential conflict of interest relevant to this article was reported.

Oxford University Press Acta Medica Okayama 2056-3418 10 2022 Fabrication of initial trabecular bone-inspired three-dimensional structure with cell membrane nano fragments rbac088 EN Koichi Kadoya Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Emilio Satoshi Hara Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Masahiro Okada Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Yu Yang Jiao Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Takayoshi Nakano Division of Materials & Manufacturing Science, Osaka University Akira Sasaki Department of Maxillofacial Surgery, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Takuya Matsumoto Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences The extracellular matrix of trabecular bone has a large surface exposed to the bone marrow and plays important roles such as hematopoietic stem cell niche formation and maintenance. In vitro reproduction of trabecular bone microenvironment would be valuable not only for developing a functional scaffold for bone marrow tissue engineering but also for understanding its biological functions. Herein, we analyzed and reproduced the initial stages of trabecular bone formation in mouse femur epiphysis. We identified that the trabecular bone formation progressed through the following steps: (i) partial rupture of hypertrophic chondrocytes; (ii) calcospherite formation on cell membrane nano fragments (CNFs) derived from the ruptured cells; and (iii) calcospherite growth and fusion to form the initial three-dimensional (3D) structure of trabecular bones. For reproducing the initial trabecular bone formation in vitro, we collected CNFs from cultured cells and used as nucleation sites for biomimetic calcospherite formation. Strikingly, almost the same 3D structure of the initial trabecular bone could be obtained in vitro by using additional CNFs as a binder to fuse biomimetic calcospherites. No potential conflict of interest relevant to this article was reported.

Elsevier Acta Medica Okayama 1882-7616 59 2023 Solid-state inorganic and metallic adhesives for soft biological tissues 439 445 EN Masahiro Okada Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Currently, the soft-tissue adhesives used in clinical practice are glue-type organic adhesives. However, there is a demand for new types of adhesives, because the current organic adhesives present challenges in terms of their biocompatibility and adhesion strength. This review summarizes the discovery and development of inorganic and metallic adhesives designed for soft biological tissues while focusing on immobilization of medical divices on soft tissues. These new types of adhesives are in a solid state and adhere directly and immediately to soft tissues. Therefore, they are called "solid-state adhesives" to distinguish them from the currently used glue-type adhesives. In previous studies on inorganic solid-state adhesives, oxides and calcium phosphates were used as raw materials in the form of nanoparticles, nanoparticle-coated films, or nanoparticle-assembled porous plates. In previous studies on metallic solid-state adhesives, only Ti and its alloys were used as raw materials. This review also discusses the future perspectives in this active research area. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2073-4360 15 20 2023 Fabrication of a Fish-Bone-Inspired Inorganic-Organic Composite Membrane 4190 EN Yuyang Jiao Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama University Masahiro Okada Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama University Bhingaradiya Nutan Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama University Noriyuki Nagaoka Advanced Research Center for Oral and Craniofacial Sciences, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Ahmad Bikharudin Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama University Randa Musa Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama University Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama University Biological materials have properties like great strength and flexibility that are not present in synthetic materials. Using the ribs of crucian carp as a reference, we investigated the mechanisms behind the high mechanical properties of this rib bone, and found highly oriented layers of calcium phosphate (CaP) and collagen fibers. To fabricate a fish-rib-bone-mimicking membrane with similar structure and mechanical properties, this study involves (1) the rapid synthesis of plate-like CaP crystals, (2) the layering of CaP-gelatin hydrogels by gradual drying, and (3) controlling the shape of composite membranes using porous gypsum molds. Finally, as a result of optimizing the compositional ratio of CaP filler and gelatin hydrogel, a CaP filler content of 40% provided the optimal mechanical properties of toughness and stiffness similar to fish bone. Due to the rigidity, flexibility, and ease of shape control of the composite membrane materials, this membrane could be applied as a guided bone regeneration (GBR) membrane. No potential conflict of interest relevant to this article was reported.

Royal Society of Chemistry (RSC) Acta Medica Okayama 2050-750X 11 3 2022 Important roles of odontoblast membrane phospholipids in early dentin mineralization 657 666 EN Risa Anada Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Emilio Satoshi Hara Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Noriyuki Nagaoka Advanced Research Center for Oral and Craniofacial Sciences, Dental School, Okayama University Masahiro Okada Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Hiroshi Kamioka Department of Orthodontics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University The objective of this study was to first identify the timing and location of early mineralization of mouse first molar, and subsequently, to characterize the nucleation site for mineral formation in dentin from a materials science viewpoint and evaluate the effect of environmental cues (pH) affecting early dentin formation. Early dentin mineralization in mouse first molars began in the buccal central cusp on post-natal day 0 (P0), and was first hypothesized to involve collagen fibers. However, elemental mapping indicated the co-localization of phospholipids with collagen fibers in the early mineralization area. Co-localization of phosphatidylserine and annexin V, a functional protein that binds to plasma membrane phospholipids, indicated that phospholipids in the pre-dentin matrix were derived from the plasma membrane. A 3-dimensional in vitro biomimetic mineralization assay confirmed that phospholipids from the plasma membrane are critical factors initiating mineralization. Additionally, the direct measurement of the tooth germ pH, indicated it to be alkaline. The alkaline environment markedly enhanced the mineralization of cell membrane phospholipids. These results indicate that cell membrane phospholipids are nucleation sites for mineral formation, and could be important materials for bottom-up approaches aiming for rapid and more complex fabrication of dentin-like structures. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2073-4360 15 5 2023 Shear Bond Strength of Resin Luting Materials to Lithium Disilicate Ceramic: Correlation between Flexural Strength and Modulus of Elasticity 1128 EN Masao Irie Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science Masahiro Okada Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science Yukinori Maruo Department of Prosthodontics, Division of Dentistry, Okayama University Goro Nishigawa Department of Prosthodontics, Division of Dentistry, Okayama University Takuya Matsumoto Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science This study investigates the effect of the curing mode (dual-cure vs. self-cure) of resin cements (four self-adhesive and seven conventional cements) on their flexural strength and flexural modulus of elasticity, alongside their shear bond strength to lithium disilicate ceramics (LDS). The study aims to determine the relationship between the bond strength and LDS, and the flexural strength and flexural modulus of elasticity of resin cements. Twelve conventional or adhesive and self-adhesive resin cements were tested. The manufacturer's recommended pretreating agents were used where indicated. The shear bond strengths to LDS and the flexural strength and flexural modulus of elasticity of the cement were measured immediately after setting, after one day of storage in distilled water at 37 degrees C, and after 20,000 thermocycles (TC 20k). The relationship between the bond strength to LDS, flexural strength, and flexural modulus of elasticity of resin cements was investigated using a multiple linear regression analysis. For all resin cements, the shear bond strength, flexural strength, and flexural modulus of elasticity were lowest immediately after setting. A clear and significant difference between dual-curing and self-curing modes was observed in all resin cements immediately after setting, except for ResiCem EX. Regardless of the difference of the core-mode condition of all resin cements, flexural strengths were correlated with the LDS surface upon shear bond strengths (R-2 = 0.24, n = 69, p < 0.001) and the flexural modulus of elasticity was correlated with them (R-2 = 0.14, n = 69, p < 0.001). Multiple linear regression analyses revealed that the shear bond strength was 17.877 + 0.166, the flexural strength was 0.643, and the flexural modulus was (R-2 = 0.51, n = 69, p < 0.001). The flexural strength or flexural modulus of elasticity may be used to predict the bond strength of resin cements to LDS. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1996-1944 15 21 2022 Does Multifunctional Acrylate's Addition to Methacrylate Improve Its Flexural Properties and Bond Ability to CAD/CAM PMMA Block? 7564 EN Yukinori Maruo Department of Prosthodontics, Okayama University Kumiko Yoshihara Health Research Institute, National Institute of Advanced Industrial Science and Technology Masao Irie Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Noriyuki Nagaoka Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Dental School Takuya Matsumoto Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Shogo Minagi Department of Prosthodontics, Okayama University This study investigated the effects of a multifunctional acrylate copolymer-Trimethylolpropane Triacrylate (TMPTA) and Di-pentaerythritol Polyacrylate (A-DPH)-on the mechanical properties of chemically polymerized acrylic resin and its bond strength to a CAD/CAM polymethyl methacrylate (PMMA) disk. The methyl methacrylate (MMA) samples were doped with one of the following comonomers: TMPTA, A-DPH, or Trimethylolpropane Trimethacrylate (TMPTMA). The doping ratio ranged from 10 wt% to 50 wt% in 10 wt% increments. The flexural strength (FS) and modulus (FM) of PMMA with and without comonomer doping, as well as the shear bond strength (SBS) between the comonomer-doped PMMA and CAD/CAM PMMA disk, were evaluated. The highest FS (93.2 +/- 4.2 MPa) was obtained when doped with 20 wt% of TMPTA. For TMPTMA, the FS decreased with the increase in the doping ratio. For SBS, TMPTA showed almost constant values (ranging from 7.0 to 8.2 MPa) regardless of the doping amount, and A-DPH peaked at 10 wt% doping (8.7 +/- 2.2 MPa). TMPTMA showed two peaks at 10 wt% (7.2 +/- 2.6 MPa) and 40 wt% (6.5 +/- 2.3 MPa). Regarding the failure mode, TMPTMA showed mostly adhesive failure between the CAD/CAM PMMA disk and acrylic resin while TMPTA and A-DPH showed an increased rate of cohesive or mixed failures. Acrylate's addition as a comonomer to PMMA provided improved mechanical properties and bond strength to the CAD/CAM PMMA disk. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2504-477X 5 10 2021 Flexural Property of a Composite Biomaterial in Three Applications 282 EN Masao Irie Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science Yukinori Maruo Department of Occlusion and Removable Prosthodontics, Okayama University Hospital Goro Nishigawa Department of Occlusion and Removable Prosthodontics, Okayama University Hospital Takuya Matsumoto Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science Resin composite is widely used in the dental field in clinics as a biomaterial. For example, it has been used as a composite material, a type of biomaterial, to repair caries and restore masticatory function, and as a luting agent to adhere the restoration to the tooth substrate. In order to demonstrate its function, we have measured the mechanical strength. From such basic research, we explain the potential of a dental material through the measurement of flexural strength and modulus of elasticity. In this research, we introduce commercial products that are actually used as composite materials suitable for tooth substrate and provide readers with their properties based on flexural strength and modulus of elasticity. In clinical performance, it might be advisable to delay polishing when a composite material is used for a luting material, a filling material and a core build-up material, as the flexural strength and the flexural modulus of elasticity were improved after 1 day of storage, and flexural strength and characteristics are considered as important mechanical properties of oral biomaterials.</p> No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 2196-7350 7 9 2020 Titanium as an Instant Adhesive for Biological Soft Tissue 1902089 EN Masahiro Okada Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Emilio Satoshi Hara Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University tsushi Yabe Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Kei Okada Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Okayama University Yo Shibata Department of Conservative Dentistry, Division of Biomaterials and Engineering, Showa University School of Dentistry Yasuhiro Torii Department of Comprehensive Dentistry, Okayama University Hospital Takayoshi Nakano Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University A variety of polymer‐ and ceramic‐based soft‐tissue adhesives have been developed as alternatives to surgical sutures, yet several disadvantages regarding the mechanical properties, biocompatibility, and handling hinder their further application particularly when applied for immobilization of implantable devices. Here, it is reported that a biocompatible and tough metal, titanium (Ti), shows instant and remarkable adhesion properties after acid treatment, demonstrated by ex vivo shear adhesion tests with mouse dermal tissues. Importantly, in vivo experiments demonstrate that the acid‐treated Ti can easily and stably immobilize a device implanted in the mouse subcutaneous tissue. Collectively, the acid‐treated Ti is shown as a solid‐state instant adhesive material for biological soft tissues, which can have diverse applications including immobilization of body‐implantable devices. No potential conflict of interest relevant to this article was reported.

SAGE Publications Acta Medica Okayama 2280-8000 18 2020 Flexural properties, bond ability, and crystallographic phase of highly translucent multi-layered zirconia 2280800020942717 EN Yukinori Maruo Department of Occlusion and Removable Prosthodontics, Okayama University Kumiko Yoshihara National Institute of Advanced Industrial Science and Technology, Health Research Institute Masao Irie Department of Biomaterials, Okayama University Goro Nishigawa Department of Occlusion and Removable Prosthodontics Noriyuki Nagaoka Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Takuya Matsumoto Department of Biomaterials, Okayama University Shogo Minagi Advanced Research Center for Oral and Craniofacial Sciences, Okayama University This study investigated the mechanical properties, bond ability, and crystallographic forms of different sites in a highly translucent, multi-layered zirconia disk. Flexural properties, bond ability to resin cement, and phase composition were investigated at three sites of a highly translucent, multi-layered zirconia disk: incisal, middle, and cervical. Flexural strength (FS) and flexural modulus (FM) were measured with static three-point flexural test. Shear bond strength (SB) to resin cement was measured after 24 h storage (37°C). Phase composition under mechanical stress was analyzed using X-ray diffraction. Without air abrasion, FS at the incisal site yielded the lowest value and was significantly lower than the middle and cervical sites. Air abrasion lowered the FS of each site. FM at the incisal site without air abrasion showed the significantly lowest value, and air abrasion increased its FM value. At the middle and cervical sites, their FM values were higher than the incisal site but were not significantly affected by air abrasion. SB value did not show significant differences among the sites. After sintering, cubic zirconia was detected at each site. Rhombohedral phase transformation occurred after mirror polishing. In highly translucent, multi-layered zirconia which was mainly composed of cubic zirconia, rhombohedral phase transformation occurred under mechanical stress and resulted in weakened mechanical properties. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 2073-4360 12 12 2020 Flexural Strength of Resin Core Build-Up Materials: Correlation to Root Dentin Shear Bond Strength and Pull-Out Force 2947 EN Masao Irie Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science Yukinori Maruo Department of Occlusion and Removable Prosthodontics, Okayama University Goro Nishigawa Department of Occlusion and Removable Prosthodontics, Okayama University Kumiko Yoshihara National Institute of Advanced Industrial Science and Technology (AIST), Health and Medical Research Institute Takuya Matsumoto Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science The aims of this study were to investigate the effects of root dentin shear bond strength and pull-out force of resin core build-up materials on flexural strength immediately after setting, after one-day water storage, and after 20,000 thermocycles. Eight core build-up and three luting materials were investigated, using 10 specimens (n = 10) per subgroup. At three time periods-immediately after setting, after one-day water storage, and after 20,000 thermocycles, shear bond strengths to root dentin and pull-out forces were measured. Flexural strengths were measured using a 3-point bending test. For all core build-up and luting materials, the mean data of flexural strength, shear bond strength and pull-out force were the lowest immediately after setting. After one-day storage, almost all the materials yielded their highest results. A weak, but statistically significant, correlation was found between flexural strength and shear bond strength (r = 0.508, p = 0.0026, n = 33). As the pull-out force increased, the flexural strength of core build-up materials also increased (r = 0.398, p = 0.0218, n = 33). Multiple linear regression analyses were conducted using these three independent factors of flexural strength, pull-out force and root dentin shear bond strength, which showed this relationship: Flexural strength = 3.264 x Shear bond strength + 1.533 x Pull out force + 10.870, p = 0.002). For all the 11 core build-up and luting materials investigated immediately after setting, after one-day storage and after 20,000 thermocycles, their shear bond strengths to root dentin and pull-out forces were correlated to the flexural strength in core build-up materials. It was concluded that the flexural strength results of the core build-up material be used in research and quality control for the predictor of the shear bond strength to the root dentin and the retentive force of the post. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1996-1944 13 22 2020 Micro-Architectural Investigation of Teleost Fish Rib Inducing Pliant Mechanical Property 5099 EN Yu Yang Jiao Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Masahiro Okada Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Emilio Satoshi Hara Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Shi Chao Xie Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Noriyuki Nagaoka Advanced Research Center for Oral and Craniofacial Sciences, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Takayoshi Nakano Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Despite the fact that various reports have been discussing bone tissue regeneration, precise bone tissue manipulation, such as controlling the physical properties of the regenerated bone tissue, still remains a big challenge. Here, we focused on the teleost fish ribs showing flexible and tough mechanical properties to obtain a deeper insight into the structural and functional features of bone tissue from different species, which would be valuable for the superior design of bone-mimicking materials. Herein, we examined their compositions, microstructure, histology, and mechanical properties. The first rib of Carassius langsdorfii showed a higher Young's modulus with a small region of chondrocyte clusters compared with other smaller ribs. In addition, highly oriented collagen fibers and osteocytes were observed in the first rib, indicating that the longest first rib would be more mature. Moreover, the layer-by-layer structure of the oriented bone collagen was observed in each rib. These microarchitectural and compositional findings of fish rib bone would give one the useful idea to reproduce such a highly flexible rib bone-like material. No potential conflict of interest relevant to this article was reported.

MDPI Acta Medica Okayama 1422-0067 21 15 2020 Cellular Fragments as Biomaterial for Rapid In Vitro Bone-Like Tissue Synthesis 5327 EN Mst Nahid Akhter Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Emilio Satoshi Hara Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Koichi Kadoya Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Masahiro Okada Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Takuya Matsumoto Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Current stem cell-based techniques for bone-like tissue synthesis require at least two to three weeks. Therefore, novel techniques to promote rapid 3D bone-like tissue synthesis in vitro are still required. In this study, we explored the concept of using cell nanofragments as a substrate material to promote rapid bone formation in vitro. The methods for cell nanofragment fabrication were ultrasonication (30 s and 3 min), non-ionic detergent (triton 0.1% and 1%), or freeze-dried powder. The results showed that ultrasonication for 3 min allowed the fabrication of homogeneous nanofragments of less than 150 nm in length, which mineralized surprisingly in just one day, faster than the fragments obtained from all other methods. Further optimization of culture conditions indicated that a concentration of 10 mM or 100 mM of beta-glycerophosphate enhanced, whereas fetal bovine serum (FBS) inhibited in a concentration-dependent manner, the mineralization of the cell nanofragments. Finally, a 3D collagen-cell nanofragment-mineral complex mimicking a bone-like structure was generated in just two days by combining the cell nanofragments in collagen gel. In conclusion, sonication for three min could be applied as a novel method to fabricate cell nanofragments of less than 150 nm in length, which can be used as a material for in vitro bone tissue engineering. No potential conflict of interest relevant to this article was reported.

Japanese Society for Dental Materials and Devices Acta Medica Okayama 0287-4547 39 2 2020 Toughening of Highly Translucent Zirconia by Monoclinic ZrO 2 and SiO 2 Particle Coating 295 301 EN Soichiro Uno Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Masahiro Okada Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Hiroaki Taketa Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Yasuhiro Torii Department of Comprehensive Dentistry, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Takuya Matsumoto Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 1549-3296 107 5 2019 Biomimetic mineralization using matrix vesicle nanofragments 1021 1030 EN Yosuke Kunitomi Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Emilio Satoshi Hara Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Masahiro Okada Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Noriyuki Nagaoka Advanced Research Center for Oral and Craniofacial Sciences, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Takuo Kuboki Department of Oral Rehabilitation and Regenerative Medicine, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Takayoshi Nakano Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University Hiroshi Kamioka Department of Orthodontics, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences Takuya Matsumoto Department of Biomaterials, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences In vitro synthesis of bone tissue has been paid attention in recent years; however, current methods to fabricate bone tissue are still ineffective due to some remaining gaps in the understanding of real in vivo bone formation process, and application of the knowledge in bone synthesis. Therefore, the objectives of this study were first, to perform a systematic and ultrastructural investigation of the initial mineral formation during intramembranous ossification of mouse calvaria from a material scientists' viewpoint, and to develop novel mineralization methods based on the in vivo findings. First, the very initial mineral deposition was found to occur at embryonic day E14.0 in mouse calvaria. Analysis of the initial bone formation process showed that it involved the following distinct steps: collagen secretion, matrix vesicle (MV) release, MV mineralization, MV rupture, and collagen fiber mineralization. Next, we performed in vitro mineralization experiments using MVs and hydrogel scaffolds. Intact MVs embedded in collagen gel did not mineralize, whereas, interestingly, MV nanofragments obtained by ultrasonication could promote rapid mineralization. These results indicate that mechanically ruptured MV membrane can be a promising material for in vitro bone tissue synthesis. No potential conflict of interest relevant to this article was reported.

Elsevier B.V. Acta Medica Okayama 1742-7061 57 2017 Biocompatible nanostructured solid adhesives for biological soft tissues 404 413 EN Masahiro Okada Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Akira Nakai Department of Biomaterials, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Satoshi Hara Emilio Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Tetsushi Taguchi Polymeric Biomaterials Group, RCFM, National Institute for Materials Science Takayoshi Nakano Division of Materials and Manufacturing Science, Graduate School of Engineering, Osaka University Takuya Matsumoto Department of Biomaterials, Okayama University Over the past few years, the development of novel adhesives for biological soft tissue adhesion has gained significant interest. Such adhesives should be non-toxic and biocompatible. In this study, we synthesized a novel solid adhesive using nanostructured hydroxyapatite (HAp) and evaluated its physical adhesion properties through in vitro testing with synthetic hydrogels and mouse soft tissues. The results revealed that HAp-nanoparticle dispersions and HAp-nanoparticle-assembled nanoporous plates showed efficient adhesion to hydrogels. Interestingly, the HAp plates showed different adhesive properties depending upon the shape of their nanoparticles. The HAp plate made up of 17 nm-sized nanoparticles showed an adhesive strength 2.2 times higher than that of the conventional fibrin glue for mouse skin tissues. No potential conflict of interest relevant to this article was reported.

Nature Publishing Group Acta Medica Okayama 2045-2322 5 2015 Peptide-modified Substrate for Modulating Gland Tissue Growth and Morphology In Vitro 11468 EN Hiroaki Taketa Ara Sathi Gulsan Farahat Mahmoud Anisur Rahman Kazi Takayoshi Sakai Yoshiaki Hirano Takuo Kuboki Yasuhiro Torii Takuya Matsumoto In vitro fabricated biological tissue would be a valuable tool to screen newly synthesized drugs or understand the tissue development process. Several studies have attempted to fabricate biological tissue in vitro. However, controlling the growth and morphology of the fabricated tissue remains a challenge. Therefore, new techniques are required to modulate tissue growth. RGD (arginine-glycine-aspartic acid), which is an integrin-binding domain of fibronectin, has been found to enhance cell adhesion and survival; it has been used to modify substrates for in vitro cell culture studies or used as tissue engineering scaffolds. In addition, this study shows novel functions of the RGD peptide, which enhances tissue growth and modulates tissue morphology in vitro. When an isolated submandibular gland (SMG) was cultured on an RGD-modified alginate hydrogel sheet, SMG growth including bud expansion and cleft formation was dramatically enhanced. Furthermore, we prepared small RGD-modified alginate beads and placed them on the growing SMG tissue. These RGD-modified beads successfully induced cleft formation at the bead position, guiding the desired SMG morphology. Thus, this RGD-modified material might be a promising tool to modulate tissue growth and morphology in vitro for biological tissue fabrication. No potential conflict of interest relevant to this article was reported.

Okayama University Acta Medica Okayama 13 2015 Peptide directs artificial tissue growth EN Takuya Matsumoto No potential conflict of interest relevant to this article was reported.