Key Engineering Materials Vols. 284-286

Abstract: Hybrids consisting of hydroxyapatite and biodegradable polymers are attractive materials for bone repair. We recently developed hydroxyapatite-alginate hybrids through a soaking process of alginate modified with 3-aminopropyltriethoxysilane (APES), ethylenediamine (EDA) and CaCl2 in a solution mimicking body fluid such as SBF, 1.5SBF proposed by Kokubo et al.. In this study, biological behavior of the apatite-alginate hybrid fabricated through modification with APES and CaCl2 were evaluated after implantation in a rat tibia, in comparison with that of alginate gel without hydroxyapatite. The higher degree of calcification was observed for the hydroxyapatitealginate hybrid than the alginate gel without hydroxyapatite. The hydroxyapatite precipitated on and inside alginate allowed the hybrid to show not only osteoconduction but also suitable biodegradation after implantation in bony defect.

Abstract: A variety of dental devices such as orthodontics, artificial teeth are implanted in oral cavity for long term. The implant coated with protective films, which can reduce corrosion and wear, may prevent the problems described above and extend the lifetime of implants to the benefit of the patients. Diamond-like carbon films have extreme hardness, low friction coefficients, chemical inertness, and high-corrosion resistance. Moreover, these properties make the good candidates as biocompatible coatings for dental devices. In this study, DLC films using the plasma CVD method deposited on acrylic resin and orthodontic archwires have investigated to detect the Ni release from the wires and to estimate cell growth in E-MEM immersed acrylic plates. After 6 months, the concentration of the nickel release from DLC-coated wire and Non-coated wire was 150 [ppb] and 933 [ppb], respectively. Results indicated DLC films inhibit the release of these materials, and prevent degradation of these materials in the solution.

Abstract: Particle filled composite and interpetrating phase composite (IPC) structures are investigated for the production of a biodegradable composite for use as a fixation device in various osteosynthesis applications. The composites consist of calcium polyphosphate, present as either a dispersion of 106 – 150 µm particles or as a sintered scaffold-like structure having open porosity in the range of 18 – 35 volume percent, and a polyvinyl acid-carbonate copolymer that is cured in situ via free radical polymerization. The performance of each composite structure is evaluated in terms of its three-point bend strength and elastic constant. Plane strain fracture toughness values are also presented for IPC samples based on CPP sintered to have 30 volume percent porosity.

Abstract: Beta-tricalcium phosphate/carboxymethyl chitin composites [TCP/CMCh] of various ratios of TCP granules and CMCh were made and their mechanical properties, handling properties and repair performance for bone defects and for osteochondral defects were investigated. Water pooling ratio of CMCh was approximately 40 times the weight itself. TCP/CMCh of a higher TCP ratio had higher stress at 50%-strain. The stress at 50%-strain of TCP/CMCh with 0, 2.5, 5.0, 7.5, 10 TCP ratios was 0.12, 0.51, 1.08, 1.46, 1.67 (MPa, n=5), respectively. The TCP/CMCh with 5.0 TCP ratios had the best total scores in handling tests. The bone repair rate of TCP/CMCh was TCP ratio 2.5< Blank= TCP ratio 7.5< TCP ratio 5.0. In the implantation test for osteochondral defects, TCP/CMCh was completely absorbed at four weeks after surgery. Regeneration of the articular cartilage was seen with TCP/CMCh and HA/CMCh but not with TCP granules, which remained eight weeks after implantation. The regenerated articular cartilage had remained 32 weeks after implantation. In conclusion, it was demonstrated that this TCP/CMCh composite was a promising material for repairing osteochondral defects.

Abstract: Intervertebral disc (IVD) damage due to degeneration, trauma or inflammation is the main cause for lower back pain leading to morbidity and loss of function of the spinal column. Until recently the state of the art treatment for degenerative disc disease (DDD) was arthrodesis. Developments in vertebral arthroplasty enable degenerated disc to be replaced with prosthetic IVD devices while maintaining motion at the affected part. The ability of the intervertebral device to support the in vivo loading environment is critical for the clinical success of such devices. However, such properties are depended on the location and structure of IVD, as the mechanical properties of IVD change locally [1]. The objective of this study was to evaluate the in vivo tissue compatibility of a novel composite, made with poly 2-hydroxyethyl methacrylate (pHEMA), poly ε-caprolactone (PCL) and poly ethylene terephthalate (PET) in an animal model. In vivo qualitative and quantitative results at 6 weeks post intraosseous implantation in rabbit femur revealed that this hydrogel, in contact with bone tissue, showed no tissue damage at the implant-bone interface. This novel composite disc prosthetic material is biocompatible as bone growth was observed into the implant and there was no evidence of toxicity to bone or inflammatory responses at the peri-implant tissue.

Abstract: Glass-ionomer cements (GIC) have been used in dentistry for over 30 years. In the past ten years they have also been developed for use as medical grade bone cements. However, concerns have been raised over the biocompatibility of GIC’s in non-dental applications. The release of Al3+ ions from the cement has been related to localized poor bone mineralisation and neurotoxicity. There is a need therefore to develop Al2O3-free cements. One potential route is the substitution of Al2O3 with Fe2O3 in the glass. An Fe2O3-based glass for use in GIC‘s was fabricated. The glass was found to differ considerably compared to the traditional amorphous Al2O3-based glasses. XRD demonstrated a highly crystalline morphology containing magnetite and apatite which was confirmed using electron microscopy. It was predicted that the reduction in Al concentration in the glass would improve the biocompatibility of the resulting cement.

Abstract: An in vivo biocompatibility test of a novel biocomposite, with major phases of CaTiO3 and Ti2O, and minor phases of AlTi3, TiO, CaO and Al2O3, was conducted on rats using subcutaneous implantation. The biocomposite and titanium alloy control specimens were removed at 6 and 14 weeks post-implantation. Histological examination revealed no significant adverse reaction of the surrounding tissue to the either the biocomposite or the control material. We conclude that the composite is well tolerated in a physiological environment.

Abstract: It is well known that bone morphogenetic protein (BMP) induces bone formation and requires for carriers. Poly-lactic acid / poly-glycolic acid (PLGA) is frequently used as the carriers of BMP. We developed a biodegradable composite PLGA membrane, which was containing oriented needle-like apatite with BMP. The composite membranes were implanted into the thigh muscle pouch of 3-week-old-mice. At 3 weeks after implantation, the implanted area was observed by optical microscopy. The composite membrane containing oriented needle-like apatite with BMP induced new bone formation. It seems that this composite membrane might be a scaffold of BMP and promoting the healing of bone defects.

Abstract: The purpose of this study was to evaluate the cytotoxicity of alginate-encapsulting ferrite particles in vitro. Various ferrite particles such as Ba-ferrite, Sr-ferrite, Co-ferrite, Co/Ni-ferrite were prepared by sol-gel process. Ferrite particles were encapsulated via calcium alginate process with different alginate contents ranged from 10 to 100 wt%. Mouse-fibroblastic NCTC L-929 cells were cultured in RPMI-1640 medium with 10% fetal bovine serum. The alginate-encapsulating ferrites were extracted in 5 ml of distilled water under pH 6.5 at 121°C for 1 h in accordance with ISO 10993-12. In vitro cytotoxicity was evaluated by WST-1. The results of this study indicated that the alginate-encapsulting ferrite particles affected cell viability by increasing alginate contents. Especially, alginate-encapsulating process were enhanced cell viability of ferrites such as Sr-ferrite, Co/Ni-ferrite, and Ba-Ferrite when alginate content was 10 wt%.