Bio-Medical Materials and Engineering - Volume 7, issue 5

Authors: Nordström, E.G. | Yokobori Jr., A.T. | Yokobori, T. | Aizawa, Y.

Article Type: Research Article

Abstract: A fine grained hydroxyapatite/mica composite material was studied by the atomic force microscopy method and the results were compared with results of atomic force microscopy studies of very five grained hydroxyapatite. In the investigation It was found that the fractal dimension diagram from the atomic force microscopy studies is a tool by which mechanical properties on the surface of the material can be predicted. The two investigated materials were found to show self-similarity properties, i.e., they are identical on the surface. The information given by the fractal dimension is important, and the fractal dimension analysis is an important tool in …future designing and engineering of, especially, bioceramics and composites. Show more

Keywords: Atomic force microscopy, hydroxyapatite, hydroxyapatite/mica composite, self-similarity

DOI: 10.3233/BME-1997-7501

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 5, pp. 285-289, 1997

Authors: Otsuka, Makoto | Nakahigashi, Yoshinori | Matsuda, Yoshihisa | Kokubo, Tadashi | Yoshihara, Satoru | Fujita, Hiroshi | Nakamura, Takashi

Article Type: Research Article

Abstract: The in vivo and in vitro drug release profiles from a self-setting bioactive CaO-SiO2 -P2 O5 glass bone cement containing indomethacin as a model drug were investigated. The cement containing 2% and 5% indomethacin (IMC) powder hardened within 5 min after mixing with ammonium phosphate buffer. After setting, in vitro drug release from drug-loaded cement pellets in a simulated body fluid (SBF) at pH 7.25 and 37°C continued for two weeks. The hardened cement gradually formed low-crystallinity hydroxyapatite during the drug release test in SBF. An IMC-loaded cement device (2% and 5% drug) was implanted in the subcutaneous tissue …on the back of rats. The in vivo IMC release from the cement increased and attained maximum levels (Cmax of 2% and 5% drug-loaded cements was 0.27 and 3.37 μg/ml, respectively) at Tmax , 3 and 0.5 d, respectively, upon subcutaneous (s.c.) administration in rats. This suggested that the s.c. administration of the cement provided IMC release for a much longer period than s.c. administration of the solution, and the plasma IMC concentration was dependent on the drug concentration in the cement. The plasma IMC concentration and the area under the curve from 2% and 5% IMC-Ioaded cements in rats were dependent on the concentration of IMC in the cements. The in vivo IMC concentration in plasma obtained by the deconvolution method was much lower than that delivered in SBF in vitro. Scanning electron microscopy and photomicrographs of cross sections showed that the bioactive bone cement had excellent biocompatibility with the surrounding soft tissues. Show more

Keywords: Hydroxyapatite, biomaterial, artificial bone, self-setting bone cement, bioactive bone glass cement, a drug delivery system for skeletal tissue, in vivo drug release test

DOI: 10.3233/BME-1997-7502

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 5, pp. 291-302, 1997

Authors: Torrisi, L.

Article Type: Research Article

Abstract: Swift ions with 50 MeV energy are used to irradiate bio-polymeric films. Lithium, carbon and oxygen beams, with fluencies ranging between 108 and 1013 ions/cm2 , are swept on large surfaces of hydrogenated and fluorated polymers. The electronic stopping power of the ion induces high rates of ionization, excitation and radical formation along the ion path with production of chain-scission and cross-linking processes which can be investigated by the molecular emission from the irradiated polymer. The radiation damage increases the chemical solubility of the material around the ion track up to distances of the order of 100 nm. …A suitable chemical etching removes the damaged material leaving micrometric holes in the polymeric film. This process gives rise to micro-perforated films which can be used as microfilters, with sub-micrometric pore dimension, high selectivity and controllable porosity. Their use is very interesting for special applications in ultra- and micro filtration of biological liquids. Show more

DOI: 10.3233/BME-1997-7503

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 5, pp. 303-313, 1997

Authors: Lewis, Gladius

Article Type: Research Article

Abstract: Interlocking intramedullary nailing is currently the leading method of treating a wide assortment of tibial fractures. Satisfactory clinical performance of such a nail is interwoven with the mechanical characteristics (chiefly, static strength, fatigue strength, fatigue life and stiffness) of the nail-contiguous fractured bone construct. The present work reviews the open literature on these nails and the mechanical performance of the constructs. Based on the observations made in the review, areas for future work are identified and expounded upon.

Keywords: Tibial interlocking intramedullary nail, stiffness, strength

DOI: 10.3233/BME-1997-7504

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 5, pp. 315-325, 1997

Authors: Zuccari, A.G. | Oshida, Y. | Moore, B.K.

Article Type: Research Article

Abstract: Acrylic resins are commonly used in many dental applications; especially in the fabrication of provisional fixed partial dentures. Among noticed technical drawbacks associated with this material are unsatisfactory mechanical properties. Moreover, if acrylic resins are exposed to moist environment, water sorption results in further mechanical deterioration. In order to improve the mechanical properties, aluminum, magnesium, and zirconium oxide powders and pulverized E-glass particles were separately admixed with pre-polymerized acrylic resin beads prior to mixing with monomer liquid. Particle loading ratios were 1,2 and 3 vol.% with respect to pre-polymerized beads. Poly(methyl methacrylate), poly(ethyl methacrylate) and poly(isobutyl methacrylate) were used …as resin matrices. Furthermore, a metal primer agent was employed in order to form a strong interpha.se between admixed particles and polymer matrix phase. Samples were subjected to three-point transverse bending tests at a crosshead speed of 10 mm/min. It was concluded that (1) addition of particles generally increases the water sorbed by the composite resins systems, (2) however, two vol.% admixtures in a PMMA resin matrix showed significant improvements in the mechanical properties (p < 0.05), (3) among the oxide particles, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness and hardness, and (4) mechanical properties (transverse strength, 0.2%. offset yield strength and modulus of elasticity) were linearly correlated to hardness numbers. Show more

Keywords: Composite resin, provisional restorations, polymethylmethacrylate resin, metallic oxide particles, mechanical properties

DOI: 10.3233/BME-1997-7505

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 5, pp. 327-343, 1997

Authors: Zuccari, A.G. | Oshida, Y. | Miyazaki, M. | Fukuishi, K. | Onose, H. | Moore, B.K.

Article Type: Research Article

Abstract: In Part I, it was found that (i) 2 vol.% admixture of reinforcing elements in PMMA (Jet) resin matrix had a significant beneficial effects on the mechanical properties, and (ii) among these, zirconia exhibited the greatest improvements in modulus of elasticity, transverse strength, toughness, and hardness number. Using the best combination (i.e., PMMA resin matrix and 2 vol.% ZrO2 ), exothermic temperature raise and polymerization shrinkage were further investigated. Deterioration in mechanical properties due to prolonged water sorption were also studied for 5 weeks. The following can be concluded: (1) By increasing liquid/powder ratio for PMMA control samples, …the peak temperature occurrence was retarded by 3 min and raised by 8°C. (2) The effect of admixed oxide particles to PMMA resin matrix on the heat generated during polymerization was not significant. (3) The polymerization volumetric shrinkage was influenced by the admixture of particles, with increases as large as 0.9% (or 0.3% in linear shrinkage). (4) PMMA resin admixed with 2 vol.% of zirconia particles showed a continuous weight gain due to water sorption, mechanical properties appears to be increasing up to 1-week sorption, followed by rapid drop of all properties. (5) Autopolymerizing acrylic resins are a resin-resin composite material of pre-polymerized beads embedded in a newly formed acrylic matrix. The main fracture modality appears to occur through the matrix and at the interface, although some trans-beads fractures were identified. (6) It was suggested that incorporating certain type of oxide particles into the pre-polymerized beads would provide stronger resin matrix. Show more

Keywords: Polymerization shrinkage, exothermic temperature raise, PMMA, oxide-reinforced polymers, water deterioration

DOI: 10.3233/BME-1997-7506

Citation: Bio-Medical Materials and Engineering, vol. 7, no. 5, pp. 345-355, 1997