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Key Engineering Materials Vols. 330-332
Paper Title Page
Abstract: Porous scaffolds of hydroxyapatite (HA), derived from calcined bovine bones and doped
with various reinforcing materials, such as Ti, TiO2 and Li2O, were produced with the aid of
commercial sugar, which was added as 20 wt% with respect to the total batch, and sintering at 1200°C
and 1300°C. The samples were characterized by SEM and X-ray diffraction analysis as well as by
porosity measurements. The experimental results showed that porosity can be controlled by the
correct selection of doping materials. The optimum sintering temperature was 1200°C since firing at
1300°C caused extended sintering and thus porosity was considerably reduced. Matching of chemical
nature as well as thermal expansion coefficients between HA and the doping components are of high
importance for the structural integrity of the resultant scaffolds. Doping with Li2CO3 seemed to have
the highest potential for achieving high porosity, likely due to the decomposition to Li2O, but the
amount of Li2CO3 used should not jeopardizing HA bioactivity. The use of natural sugar is an
economic way of producing safe for the health porous HA scaffolds.
411
Abstract: Collagen (Col) and chitosan (Chi) are both natural polymers and have received extensive
investigation in recent years in the field of tissue engineering, but there are few reports on the
introduction of hydroxyapatite (HA) into the Col-Ch system. In this study, based on the miscibility
of these two polymers under proper condition, hydroxyapatite (HA) was synthesis in the Col-Chi
system by in-situ co-precipitate method to give rise to a novel nanocomposite. The structural
characterization of such Col-Ch-HA nano-materials was carried out by using FT-IR, XRD, SEM
and TGA analyses with main components and Col-Chi samples used for comparison. It was found
that there exist interactions between Col and Chi molecules. The nucleation and growth of inorganic
phase occurs in the Col-Chi system and final products are uniform dispersion of nano-sized HA in
the Col-Chi network without obvious phase separation. This novel nanocomposite would be a
promising material for bone tissue engineering.
415
Abstract: Histoacryl® (N-butyl-2-cyanoacrylate) has been widely utilized as a tissue adhesive. The
aim of this study was to evaluate the physical and adhesive properties of newly developed
cyanoacrylate-based β-TCP composite systems. The β-TCP powder was modified on the surface
with citric acid to make this material mixed with cyanoacrylate easily. The setting time of acidtreated
β-TCP/ Histoacryl® systems was dramatically prolonged and the polymerization heat was
significantly decreased compared to that of untreated β-TCP/Histoacryl® system. The shear bond
strength of cyanoacrylate-based β-TCP composites decreased with addition of acid-treated β-TCP
filler. The compressive strength of β-TCP/Histoacryl® composites increased strongly with
increasing the amount of acid-treated β-TCP filler. The cytotoxicity of the β-TCP/Histoacryl®
composites decreased with the increasing of the amount of added β-TCP. These results indicated
that our novel β-TCP/Histoacryl® composites had the great potential to serve as adhesives or filling
materials in the dental field.
419
Abstract: In order to develop a bone-filling material with osteoinductive potential, a composite
micorspheres of collagen molecules and biphasic calcium phosphate (BCP) was prepared by
utilizing emulsion polymerization and the intrinsic self-assembly of collagen. The prepared
microspheres were analyzed by granularity test, scanning electron microscopy (SEM), infrared
spectra (IR) and enzymatic digestion experiment. The results showed that the collagen matrix of
fibrils was reconstituted in the droplets, and the native triple-helix structure of collagen was still
maintained. The study provides an effective way to prepare microspheres of collagen and BCP
composite.
423
Abstract: Synthesis of hydroxyapatite (HA) in organic solutions has received extensive attention in
recent years with an attempt to obtain HA of a nanometer level. In this preliminary study, we
demonstrated that organic-HA nanocomposites could also be achieved with one step method via in
situ mineralization and subsequent crosslinking of organic species. This design was realized
through in situ synthesis of hydroxyapatite in poly(vinyl alcohol) and acrylic acid aqueous solution
as an organic template. The aforementioned organic-inorganic nanocomposites were analyzed by
using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electrical microscopy,
thermal analysis. The comparative structural measurements were also conducted with the
synthesized HA with absence of the organic template. The results indicated that the existence of
organic species effectively inhibits the growth of calcium phosphate and that relatively pure HA can
be obtained in sintered composite products. The present study provides a direct and versatile route
for fabrication of nanocomposite biomaterials.
427
Abstract: Magnetite/hydroxyapatite/chitosan rods have been prepared via in situ compositing
method. The mechanical properties were characterized and evaluated for suitability as a bone repair
materials. Scanning electron microscopy (SEM) was carried out to investigate the microstructure of
CS/HA/Fe3O4 composite. Effect of inorganic content on the mechanical properties of the
CS/HA/Fe3O4 composite was also investigated. It was observed that the mechanical properties of
the composite in the dry condition improved as the percentage of CS content increased. Mechanical
properties of CS/HA/Fe3O4 composite rod are much better than that prepared via traditional method.
Bending strength, bending modulus of CS/HA/Fe3O4 composite are 118.5 MPa, 2.3 GPa,
respectively. All of these material properties are twice or three times stronger compared with that of
nature bone of human being.
435
Abstract: So-called bioactive ceramics bond to living bone through the apatite layer formed on their
surfaces in the body. The apatite deposition is triggered by dissolution of calcium ion (Ca2+) and by
silanol (Si-OH) group formed on the surfaces of the ceramics. It is expected that organic modification
of these components would produce bioactive materials with high flexibility. In this study, we
examined bioactivity and mechanical properties of the organic-inorganic hybrids from starch by
modification with silanol group and calcium ion. Effect of cross-linking agent was also investigated.
The obtained hybrids showed bioactivity and mechanical properties analogous to those of human
cancellous bone by appropriate control in their compositions. Addition of cross-linking agent to
improve mechanical strength of the hybrids did not decrease their bioactivity.
439
Abstract: A long-term stable material, which has two main crystalline phases – fluorapatite (FA)
and calcium zirconium phosphate (CZP) [1, 2] and could be processed to dense sintered samples
was tested related to the use with two application forms – spongiosa-like specimen and foils. The
suitability of various sintering additives was investigated alone and in diverse combinations. During
sintering of the spongiosa-like samples volume shrinkage of about 50% was observed whereas the
shrinkage in x,y plane was about twice of the shrinkage in z direction. The cuboid form was not
affected by the shrinkage. The compression strength of the spongiosa-like materials was in the
range of 1MPa up to 1.6MPa. A ceramic foil was generated via foil slip casting of a slip containing
about 38vol% of FA-CZP. Temperature programs were created for debindering and sintering of the
green foil and the four-fold laminate, respectively.
443
Abstract: In the present in vitro study, osteoblasts proliferation, vitality and ultrastructure were
investigated when cultured in the presence of silver-hydroxyapatite/titania nanoparticles
(nAg_HA/TiO2) compared to HA nanoparticles (nHA) at various concentrations and cell culture
without nanoparticles for up to 120 hours. Results confirmed the detrimental influences of both
nAg_HA/TiO2 and nHA on osteoblast growth.Cell vitality was slightly higher during the earlier 24h,
but after that was inhibited. Both cell proliferation and vitality by addition of nanoparticles were
restricted with concentrations of nanoparticles increasing. However, the respiration rates by addition
of nanoparticles were showed higher than that of the cell culture without nanoparticles. No
remarkable ultrastructure changes were showed in the osteoblasts exposed nanoparticles. The
difference in cell proliferation, vitality and ultrastructure between nAg_HA/TiO2 and nHA were
insignificant. It was demonstrated that biocompatibility of nAg_HA/TiO2 is almost the same as nHA.
447