Key Engineering Materials Vols. 309-311

Abstract: Diamond-like carbon (DLC) coatings were deposited on titanium alloy (Ti-13Nb-13Zr) by plasma immersion process. DLC-coated Ti alloy and uncoated Ti were investigated in an animal model using the femoral condyles of rats for intervals of 4 and 12 weeks postoperatively. The interface between the implants and bones of the femoral condyles were analysed using scanning electron microscopy (SEM) by backscattering. The results showed that the DLC coatings were well tolerated in both periods.

Abstract: Alumina powder containing δ , δ crystal phases (designated δAP) showed osteoconductivity. δAP was manufactured by fusing pulverized alumina powder and quenching it. The purpose of the present study was to evaluate osteoconductivity of δAP using rat tibiae. Alumina powder containing αcrystal phase (designated αAP) was used as a reference material. These two types of alumina powder were packed into the intramedullary canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index. Rats were sacrificed at 4 and 8 weeks after surgery. The affinity index, equal to the length of bone in direct contact with the powder surface expressed as a percentage of the total length of the powder surface, was calculated for each alumina powder at each interval. At 4 and 8 weeks, the affinity indices for δAP were significantly higher than those for αAP. For both δAP and αAP, there were no significant differences between the values for 4 and 8 weeks. This study revealed that the osteoconductivity of δAP was due to the alumina’s δcrystal phases. δAP shows promise as a basis for developing a osteoconductive biomaterial.

Abstract: Three types of polymethylmethacrylate (PMMA)-based composite cements containing 40− 56 wt% micron-sized titania (titanium oxide) particles, designated ST2-40c, ST2-50c, and ST2-56c, were developed as bone substitutes for vertebroplasty, and evaluated for their mechanical, setting, and biological properties. In animal experiments, ST2-50c and ST2-56c were implanted into rat tibiae and solidified in situ. Their biological properties were evaluated at 6 and 12 weeks after implantation. Compressive strength, bending strength, and bending modulus increased with increasing titania content. Peak temperature during the setting reaction decreased as the filler content increased. ST2-56c had direct contact with bone over larger areas than ST2-50c at 6 and 12 weeks. Data from the present study indicated that ST2-56c is a good candidate as a bone substitute for vertebroplasty.

Abstract: Bioactive bone cement with mechanical properties higher than that of commercial polymethylmethacrylate (PMMA) bone cement are strongly desired to be developed. In the present study, PMMA-based cement incorporated with nano-sized rutile particles was prepared. The PMMA-based cement (rutile content was 50 wt%) shows the compressive strength (136 MPa) higher than that of commercial PMMA bone cement (88 MPa). The hardened cement formed apatite on the surface in a simulated body fluid within 3 days. Therefore, this PMMA-based cement incorporated with rutile particles might be useful as cement for fixation of prostheses as well as self-setting bone substitutes, because of its high apatite forming ability and mechanical strength.

Abstract: In order to overcome the disadvantage of commercialized PMMA bone cement, we have developed novel PMMA-based bone cement(7P3S) reinforced by 30 wt.% of bioactive CaO-SiO2 gel powders to induce the bioactivity as well as to increase mechanical property for the PMMA bone cement. The novel 7P3S bone cement hardened after mixing for about 7 minutes. For in vitro evaluation, apatite forming ability of it was investigated using SBF. When the novel 7P3S bone cement was soaked into SBF, it formed apatite on its surfaces within 1 week Furthermore; there is no decrease in its compressive strength within 9 weeks soaking in SBF. It is though that hardly decrease in compressive strength of 7P3S bone cement in SBF is due to the relative small amount of gel powder or its spherical shape and monosize. In vivo evaluation of the novel 7P3S bone cement was carried out using rabbit. After implantion into rabbit tibia for several periods, the interface between novel bone cement and natural bone was evaluated by CT images. According to the results, the novel bone cement directly contact to the natural bone without fibrous tissue after implantation for 4 weeks. This results indicates that the newly developed 7P3S bone cement can bond to the living bone and also be effectively used as bioactive bone cement without decrease in mechanical property.

Abstract: A new composite bone cement designated ‘G2B1’ was developed for percutaneous transpedicular vertebroplasty. G2B1 contains beta tricalcium phosphate particles and methylmethacrylate –methylacrylate copolymer as the powder components, and methylmethacrylate, urethane dimethacrylate, and tetrahydrofurfuryl methacrylate as the liquid components. Osteoconductivity and histological changes with time were evaluated using scanning electron microscopy, contact microradiography, and Giemsa surface staining 4, 8, 12, 26, and 52 weeks after implantation into rat tibiae. To evaluate osteoconductivity, affinity indices (%) were calculated. Scanning electron microscopy and contact microradiography revealed that bone contact with G2B1 was attained within 4 weeks (affinity index: 50.2 ± 11.8 at 4 weeks) and at most of the margin within 26 weeks (affinity index: 87.4 ± 7.2 at 26 weeks). Giemsa surface staining showed that there was almost no inflammatory reaction around the G2B1. These results indicate that G2B1 is a biocompatible and highly osteoconductive bone cement.

Abstract: The bioactivity and biocompatibility of a zinc phosphate luting cement (HARVARD, Richter & Hoffmann, Dental-GmbH, Berlin) which was modified by Bioglass® (PerioGlas® Synthetic Bone Graft Particulate, US Biomaterials), was evaluated in vitro with human lung fibroblasts (MRC-5), baby hamster kidney fibroblasts (BHK) and rat pulp cells (RPC) by XTT and BrdU assays. A thin Ca-P layer was grown on the surface of Bioglass®-modified zinc phosphate cement specimens after immersion in SBF for 7 days and remained constant after 16 days immersion time. The incorporation of Bioglass® powder in zinc phosphate specimens resulted in equal or increased cell attachment and activity for almost all cell lines examined without any apparent impact on mechanical or physicochemical properties of the cement, although this needs further documentation. The combination of these two methods in determining the biocompatibility of Bioglass®-modified zinc phosphate cements showed that cells not only attached well on modified specimens but were actively synthesizing DNA after 72h of incubation.

Abstract: The aim of this study is evaluate to the cellular viability of elution from the newly developed resin and Osteobond® in vitro. The basis of the newly developed resin are methacryloyloxyethyl methyl succinate and 1,6-Hexanediol dimethacrylate. The basis of Osteobond is methyl methacrylate. The concentrations of basis in each elution were determined by high-performance liquid chromatography (HPLC). Cellular viabilities of L-929 mouse fibroblasts were evaluated by direct cells counting, and then, each IC50 value was calculated. Moreover, patterns of cell death were analyzed using annexin V/propidium iodide staining with the phase-contrast microscope and flow cytometry. The concentration of Osteobond elution was 2.16 mM of MMA, and the newly developed resin elution was 1.02 mM of TA and 1.87 x 10-2 mM of HX. Until 72 hours of incubation, treatment with each elution impaired the viability of L-929 cells in a dose-dependent manner. IC50 value of Osteobond was 6.48 x 10-4 mM of MMA. However, IC50 of the newly developed resin was not calculated. Treatment with Osteobond elution showed more necrotic cells than with the newly developed resin elution. In conclusion, the results demonstrated much more excellent cellular viability of the newly developed resin than that of MMA resin. Thus, it is suggested that the newly developed resin will be more useful as an implantation material for dentistry and orthopaedics.

Abstract: In this paper the synthesis of bioactive cement based on α-Ca3(PO4)2 (α-TCP) and calcium deficient hydroxyapatite (CDHAp), obtained by hydrothermal method from CaCl2, EDTA, NaH2PO4·12H2O and urea at 160oC, was described. According to the results of DTA, SEM, X-ray and FTIR analyses performed in this investigation, it is shown that CDHAp is transformed to β- TCP at 780oC, and to α-TCP at 1400oC. The hardening of the samples, prepared from the mixture of α-TCP and 2.5 % solution of Na2HPO4, in simulated body fluid at 37oC, was followed by the microstructure changes.