Keywords

Paper information

Mitsugu TODO, Keiichi SASAKI and Takashi GOTO, “Preface”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.306-306 . doi:10.1299/jbse.4.306

Muscloskeletal tissues, bone, cartilage, muscles and tendons regulate and support the body's actions and are differentiated from mesenchymal stem cells. These organs generate and/or respond to mechanical stress, which is inevitable in daily life. Among these tissues, cartilages play roles in articular function in joints where shear stress is loaded in combination with cyclical or intermittent compressive force by joint action, and provides a template for bone growth under compressive stress directed along the long axis of long bones. Along with soluble factors, such as cytokines and growth factors, mechanical stress has been recognized as one of the epigenetic factors that regulates the gene expression of various types of cells. Thus, the molecular mechanisms of the mechano-sensing, mechano-transduction, and mechano-response of cells have become a focus of connective tissue biology. Here, we will discuss the mechanisms through which differentiated chondrocytes and mesenchymal cells that are differentiating into chondrocytes respond to various types of mechanical stress by altering their phenotype and how these phenotypic changes are molecularly regulated. We will focus on the roles of cell-extracellular matrix interactions through integrins and downstream signaling pathways involving mitogen-activated protein kinases.

Keywords

Chondrocyte, Cell-ECM Interface, MAPK, Phosphorylation

Paper information

Ichiro TAKAHASHI, Taisuke MASUDA, Kumiko KOHSAKA, Fumie TERAO, Takahisa ANADA, Yasuyuki SASANO, Teruko TAKANO-YAMAMOTO and Osamu SUZUKI, “Molecular Mechanisms of Mechanical Stress Response during Chondrogenesis”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.307-317 . doi:10.1299/jbse.4.307

Ti-Ag alloys with 20 and 25 mass% Ag were prepared; their surfaces were polished using silicon carbide abrasive papers. The polished alloys were immersed in a simulated body fluid (SBF), and their surfaces were observed by scanning electron microscope (SEM) to investigate the spontaneous formation of calcium phosphates. The precipitates formed on the alloys were qualitatively and quantitatively analyzed using an electron probe microanalyzer (EPMA), with pure titanium and silver used as controls. Hardness and surface roughness, which was measured as the height parameter Ra, were examined, and their effect on calcium phosphate formation was elucidated. On immersion in SBF, calcium phosphates were formed on the Ti-Ag alloys and pure titanium but not on pure silver. The amount of the precipitate and the concentration ratios of calcium to phosphorus in the precipitates of the Ti-Ag alloys and pure titanium did not differ significantly. The Ti-Ag alloys showed significantly higher hardness and lower Ra values than pure titanium. The Ra values of the metals decreased as their hardness increased. The Ra values of the metals appeared to have very little effect on calcium phosphate formation. The results of this study have verified the biocompatibility of the Ti-Ag alloys, making them suitable for use as dental and orthopedic implants.

Keywords

Biomaterial, Titanium Alloy, Calcium Phosphate, Simulated Body Fluid, Bioconductivity, Biocompatibility, Dental Implant

Paper information

Masatoshi TAKAHASHI, Masafumi KIKUCHI, Kouki HATORI, Yusuke ORII, Keiichi SASAKI and Yukyo TAKADA, “Calcium Phosphate Formation on Ti-Ag Alloys in Simulated Body Fluid”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.318-325 . doi:10.1299/jbse.4.318

In the present study, peri-implant tissue alteration was studied histologically, and then differences in the gene expression pattern of certain proteins were analyzed using cDNA microarray analysis, under the influence of static lateral load. Beagle dogs were divided into two groups: control and load. Three months after the extraction of mandibular premolars, two implants were placed in each side of the mandible. Each group was further divided into subgroups for loading times of 1, 7 and 14 days. Immediately after the implant installation, a loading device was adhered between the abutments of neighboring implants. Afterward, the expansion screw of the load group was activated by 360-degree rotation, resulting in 0.7 mm horizontal expansion. After sacrificing the dogs, peri-implant tissue was collected, then microarray analysis for the detection of gene expression was performed, as well as histology. Histology indicated that the peri-implant tissue broke down under the influence of the load. Microarray analysis demonstrated the presence of load-sensitive gene expression even after 1 day. Differences in gene expression patterns in concert with static lateral load were demonstrated, even at an early stage post-operation. Further study may help in the diagnosis of pathological overload.

Keywords

Mechanical Stress, Static Load, Microarray Analysis, Dental Implant, Dental Implant Failure

Paper information

Yasuko MORIYAMA, Yasunori AYUKAWA, Kenichi KABEMURA, Yasuyuki MATSUSHITA, Masafumi KIHARA, Yoshihiro TSUKIYAMA, Mitsugu TODO, Yoshihiro TAKAO and Kiyoshi KOYANO, “The Alternation of Peri-Implant Bone Response Exposed to Static Lateral Load”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.326-335 . doi:10.1299/jbse.4.326

A porcine mandible was separated to prepare thin periodontium specimens, consisting of a molar, periodontal ligament (PDL), and alveolar bone. Occlusion was simulated by applying a forced compressive displacement, using a table-top material tester. We photographed images of the displacing periodontium specimen and simultaneously obtained the load-displacement curve during the test. The displacement and deformation distributions were examined using digital image correlation analysis. Then, we correlated the distribution with the load-displacement curve, which was characterized by biphasic behavior, as noted in many previous studies. We found that the displacement and deformation distributions of actual periodontium correlated with the load-displacement curve during dental occlusion. Regarding the biphasic characteristics of the load-displacement curve, we showed experimentally that the first phase indicated deformation of the PDL and the second indicated deformation of the alveolar bone and tooth.

Keywords

Dental Occlusion, Load-Displacement Curve, Deformation Distribution, Digital Image Correlation, Whole-Field Measurement, Periodontium, PDL, Alveolar Bone, Porcine Mandible, Biphasic Characteristics

Paper information

Yasuyuki MORITA, Masakazu UCHINO, Mitsugu TODO, Yasuyuki MATSUSHITA, Kazuo ARAKAWA and Kiyoshi KOYANO, “Relationship between the Load-Displacement Curve and Deformation Distribution in Porcine Mandibular Periodontium”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.336-344 . doi:10.1299/jbse.4.336

Currently, β-type Ti-Nb-Ta-Zr alloys are gaining attention owing to their feasibility for use as biomedical materials. However, the deformation behaviors of these alloys have not yet been clarified. In this study, the Nb content of the Ti-30Nb-10Ta-5Zr (TNTZ) alloy was altered between 1.0 and 3.0 mass% from 30 mass%, and the corresponding changes in the superelasticity and shape-memory characteristics were investigated by tensile loading-unloading tests, X-ray diffraction (XRD) analysis, and microstructural analysis using a transmission electron microscopy (TEM). When the Nb content is less than approximately 29 mass%, the loading-unloading stress-strain curves show two-step gradients and are similar to those of common shape-memory alloys such as Ti-Ni alloys; these gradients result from stress-induced martensitic transformation and its reversion. When the Nb content is approximately 30 mass%, the tensile loading-unloading curves show a nonlinear gradient corresponding to superelastic behavior, which can not be explained by XRD and TEM microstructural analyses on stress-induced martensitic transformation and its reversion in the present state. When the Nb content is approximately 31 mass%, the tensile loading-unloading curves show a single gradient. The elastic deformation is mainly caused by the elastic strain in the lattice. Changes in the chemical content of Nb in TNTZ within a very narrow range are found to alter the superelastic behavior of this alloy.

Keywords

β-Type Titanium Alloy, Metallic Biomaterial, Stress-Induced Martensite, Elastic Deformation, Superelastic Behavior

Paper information

Toshikazu AKAHORI, Mitsuo NIINOMI, Masaaki NAKAI and Harumi TSUTSUMI, “High Mechanical Functionalization of Metallic Biomaterials through Thermomechanical Treatments”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.345-355 . doi:10.1299/jbse.4.345

The polymerization shrinkage of dental restorative resin composites in cavities was studied using a digital image correlation method. The cylindrical and semi-cylindrical cavities in bovine teeth were used to examine the shrinkage behavior on the top free surface and the simulated cross section, respectively. The cavities filled with the resin after spreading a bonding agent were irradiated using a visible-light curing unit and photographed with a CCD camera as a function of time. The two images photographed were correlated to study the deformation during the polymerization process. Experiments were also performed on the cavities without the bonding agent, and its effect on the bonding strength at the interface between the resin and tooth structure was examined.

Keywords

Dental Restoration Material, Light Cure Resin Composite, Bovine Tooth, Polymerization Shrinkage, Displacement Fields, Digital Image Correlation Method

Paper information

Taichi FURUKAWA, Kazuo ARAKAWA, Yasuyuki MORITA and Masakazu UCHINO, “Polymerization Shrinkage Behavior of Light Cure Resin Composites in Cavities”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.356-364 . doi:10.1299/jbse.4.356

Previously, a few models have been proposed to predict bone resorption process due to stress shielding in long bones such as proximal femur; however, there are almost no reports on finite element analysis of loss of marginal dental bone that is caused mainly by occlusive overload. In this work, the stress, strain and strain energy density (SED) criteria were separately applied to simulate overload-induced bone resorption in a jawbone/implant system by means of the finite element analysis. A simplified dental bone/implant model was created, with the bone composed of a cortical bone and a cancellous bone and the implant having the detailed screw structure. The results demonstrated that the simulations according to the equal SED criterion reproduce bone resorption patterns that are more realistic to actual clinical situations, when compared to the equal stress or strain criterion. It was shown that bone resorption starts initially in the cortical bone around the implant neck, then extends downwards, and lastly enters the cancellous bone after passing through the interface of the cortical and cancellous bone. A symmetric bone resorption pattern was revealed under the condition of axial loading, whereas an asymmetric resorption prototype was demonstrated under the oblique loading condition. Moreover, in the case of oblique loading, bone resorption is faster and the amount of resorbed bone is larger, which leads to more micromotion of the dental implant than in the case of axial loading.

Keywords

Bone Resorption, Bone Remodeling, Dental Implant, Numerical Simulation, Finite Element Analysis

Paper information

Lihe QIAN, Mitsugu TODO, Yasuyuki MATSUSHITA and Kiyoshi KOYANO, “Finite Element Analysis of Bone Resorption Around Dental Implant”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.365-376 . doi:10.1299/jbse.4.365

Newly approach using the formation process of polymer foam is introduced in this study to prepare porous hydroxyapatite (HAp) scaffolds for bone tissue engineering applications, which could provide a better control over the microstructures of scaffolds and enhance their mechanical properties. The scaffolds prepared have an open, relatively uniform and interconnected porous structure with a pore size ranging 50 to 300 ?m. A compressive strength of 5 MPa for the scaffolds with HAp content 80 wt% and higher porosity of 77% was achieved. The pore morphology and size of the scaffolds were characterized using a scanning electron microscopy. X-ray diifraction was used to determine the crystal structure. Scaffolds with desired porosity, pore size, and geometry could be prepared by using the formation process of polymer foam with controlling process parameters.

Keywords

Porous, Hydroxyapatite, Scaffold, Polymer, Foaming

Paper information

Zin-Kook KIM, Jeong-Jung OAK, Hisamichi KIMURA, Takashi GOTO, Akihisa INOUE and Seog-Young YOON, “Achitecture of Porous Hydroxyapatite Scaffolds Using Polymer Foam Process”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.377-383 . doi:10.1299/jbse.4.377

Ni-free type Ti-based metallic glass evaluated in this study has imposing performances for biomaterials that is based on high bulk forming ability (BFA) for implantable materials, superior specific strength, low Young's modulus as hard tissue replacements and excellent workability. Especially, surface characteristics of Ti-based bulk metallic glass for corrosion resistance exhibit a high potential for application to be used as dental implants in the oral cavity. We also made an examination of chemical stability for human cell test with osteoblasts (SaOS2) in vitro. Results of the good biocompatibility and high glass forming ability evaluated in this study are expected to increase utility value for biomedical application

Keywords

Ti Alloy, Bulk Metallic Glasses, Corrosion Resistance, Cell Culture, Implant Materials

Paper information

Jeong-Jung OAK, Gi-Wook HWANG, Yong-Ha PARK, Hisamichi KIMURA, Seog-Young YOON and Akihisa INOUE, “Characterization of Surface Properties, Osteoblast Cell Culture in Vitro and Processing with Flow-Viscosity of Ni-Free Ti-Based Bulk Metallic Glass for Biomaterials”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.384-391 . doi:10.1299/jbse.4.384

Calcium phosphate coating films were fabricated on blast-treated titanium plates and screw-type titanium implants using RF magnetron sputtering. A uniform and dense coating film with a thickness of 0.5 ?m could cover the blast-treated titanium plate efficiently, maintaining the surface roughness of the substrates. The as-sputtered coating films consisted of amorphous calcium phosphate (ACP) or oxyapatite (Ca10(PO4)6O, OAp). Heat treatments of the OAp coating films were conducted in a silica ampoule or in air, and it was observed that the crystallinity of the coating films increased after the heat treatment. The bonding strength between the as-sputtered coating films, subjected to heat treatment in air, and the blast-treated titanium plates exceeded 60 MPa. An immersion test was conducted and alkaline phosphatase (ALP) activity of osteoblasts was investigated in vitro. The dissolution rate of the coating films in the 0.9% NaCl solution decreased with an increase in their crystallinity. The ACP coating film exhibited high ALP activity. As the in vivo evaluation, the coated and non-coated titanium implants were implanted into the femur of Japanese white rabbits. The percentage of bone-implant contact and the removal torque value of the coated titanium implants were greater than those of the non-coated titanium implants.

Keywords

Calcium Phosphate, Titanium, Sputtering, Bonding Strength, Immersion Test, Implant, Animal Experiments

Paper information

Kyosuke UEDA, Yuuki KAWASAKI, Takayuki NARUSHIMA, Takashi GOTO, Jun KURIHARA, Hironobu NAKAGAWA, Hiroshi KAWAMURA and Masayuki TAIRA, “Calcium Phosphate Films with/without Heat Treatments Fabricated Using RF Magnetron Sputtering”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 3 (2009), pp.392-403 . doi:10.1299/jbse.4.392