Glass-ceramic Powder Research Articles

생체활성 유리 골 시멘트의 응결 및 수산화 아파타이트 형성

Hardening and hydroxyapatite(HAp) formation behavior of the bioactive cements in the system of CaO-SiO₂-P₂O 5 glasses and the corresponding glass-ceramics were studied. DCPD (Dicalcium Phosphate Dihydrate : CaHPO₄ · 2H₂O) and DCPA (Dicalcium Phosphate Anhydrous : CaHPO₄) were developed when the prepared glass and glass-ceramic powders were mixed with three different solutions. The DCPD and DCPA transformed to HAp when the cement was soaked in Simulated Body Fluid (SBF), and this HAp formation strongly depended on the releasing capacity of Ca 2+ ions from the cements. The glass-ceramic containing apatite showed fast setting, but no HAp formation was observed because no Ca 2+ ions were released from this glass-ceramics. The compressive strength of the cements increased with reaction time in SBF until all DCPD and DCPA transformed to HAp.

Low-temperature synthesis of pure BaAl 2Si 2O 8 glass–ceramic powder by citrate process

The citrate process was successfully used to prepare a glass–ceramic powder with the stoichiometric composition of BaAl 2Si 2O 8 (BAS 2). The solutions of barium and aluminum nitrate, colloidal silica, citric acid, and diethylene glycol were combined and afforded a clear gel on mixing which was further decomposed on heating to an easily handled precursor in a powder form. The characteristics of this dried precursor were analyzed by X-ray powder diffraction (XRD), differential thermal (DTA) and thermal gravimetric (TGA), and thermal mechanical analyses (TMA). An intermediate grinding of the precursor is crucial for the successful synthesis of the hexagonal BaAl 2Si 2O 8 directly from the precursor which was crystallized at temperature as low as 850 °C for 4 h calcination.

Mechanical behavior of bioactive composite cements consisting of resin and glass-ceramic powder in a simulated body fluid: effect of silane coupling agent.

Time-dependent strength behavior was investigated for bisphenol-a-glycidyl methacrylate/triethylene glycol dimethacrylate (Bis-GMA/TEGDMA) resin cements combined with glass-ceramic A-W filler treated with various kinds of silane coupling agents. The fracture strength of the composite resin cements was measured by three-point bending as a function of stressing rate in a simulated body fluid (SBF), and thereby the stress-corrosion susceptibility constant was evaluated. The fracture strength was found to depend on the kind of coupling agent used. For the present Bis-GMA/TEGDMA resin, the silane coupling agents without hydrophilic amine groups can be used to obtain good adhesion between resin and A-W filler owing to their nature of co-polymerizing with the resin. On the other hand, all the composite resin cements showed nearly the same degree of stress-corrosion susceptibility whether the A-W fillers were treated or untreated with silane coupling agents. This means that the stress-corrosion susceptibility of the present composite cements is predominantly affected by that of the matrix resin. Thus, the microcrack formation and growth at the resin matrix near particle - resin interface were thought to determine overall time-dependent strength behavior of the composite cements.

Preparation of β-spodumene-based glass–ceramic powders by polyacrylamide gel process

Glass–ceramic powders with a composition of Li 2O·Al 2O 3·4SiO 2 (LAS) containing various ZrO 2 additives have been synthesized by a novel method based on polyacrylamide (PAM) gel process using Al(NO 3) 3·9H 2O, Li 2CO 3, Si(OC 2H 5) 4 and ZrOCl 2·8H 2O as starting materials. X-ray powder diffraction (XRD), thermal analysis (TG–DTA) and transmission electron microscope (TEM) are utilized to characterize the gel powders. For the LAS powders with various amount of ZrO 2, the crystalline phase first obtained is β-quartz solid solution, which then gradually transforms into β-spodumene at high temperature. The transformation from β-quartz solid solution to β-spodumene is increasingly restricted as more ZrO 2 is added in the LAS system. The average particle size of the LAS powders is in nanometer scale with a narrow size distribution.

Preparation of Glass-Ceramics Containing Ferrimagnetic Zinc-Iron Ferrite for the Hyperthermal Treatment of Cancer

Ferrimagnetic glass-ceramics are useful as thermoseeds for hyperthermal treatment of malignant tumors, especially those located in deep parts of the body, since hysteresis loss heating occurs locally at the cancer site when they are implanted around the tumor and subjected to an alternating magnetic field. In the present study, glass-ceramic powders containing a large amount of fine particles of zinc-iron ferrite (Zn x Fe 3 - x O 4 ) in a CaO-SiO 2 -based glassy matrix were prepared by the heat treatment of ZnO-Fe 2 O 3 -CaO-SiO 2 glasses at various temperatures for 1 h in a 95CO 2 + 5H 2 atmosphere. The Zn x Fe 3 - x O 4 precipitated above 700°C, and its crystallite size and fraction increased with increasing heat-treatment temperature, reaching 130 nm and 37 mass% at 1150°C, respectively. The saturation magnetization of the specimen increased to 38.4 emu.g - 1 with increasing heat-treatment temperature up to 1150°C. The coercive force of the specimen increased to 167.6 Oe at 1000°C, and then decreased with increasing heat-treatment temperature. When the heat-treatment period at 1150°C in a 95CO 2 + 5H 2 atmosphere was increased from 1 to 5 h, the content of Zn x Fe 3 - x O 4 was not changed, whereas the crystallite size of Zn x Fe 3 - x O 4 increased from 130 to 170 nm. The saturation magnetization and coercive force of the powders heat treated at 1150°C for 5 h in a 95CO 2 + 5H 2 atmosphere were 26.5 emu.g - 1 and 150.5 Oe, respectively. The prepared glass-ceramic powders showed a large amount of heat generation of 12.4 W.g - 1 , under conditions of 300 Oe and 100 kHz.

Study on the structure and dielectric properties of BaO–SiO 2–B 2O 3 glass-doped (Ba,Sr)TiO 3 ceramics

(Ba,Sr)TiO 3 (BST)-based ferroelectric glass-ceramic powders with different BaO–SiO 2–B 2O 3 glass content, ranging from 0 to 30 mol%, were prepared by a sol–gel process. The crystalline structure and morphology were studied by XRD and SEM, respectively. The temperature dependence of dielectric constant and loss ( ε − T), dielectric constant versus applied dc field ( C– V) was measured for the BST glass-ceramics. Effects of doping glass on the structures and the dielectric characteristics of the BST glass-ceramics were discussed. Experimental results show that the BST glass-ceramics with pure perovskite phase can be well sintered at a lower temperature compared to the conventional BST ceramics. The dielectric constant and tunability decrease with the increasing of glass content. The sample with a glass content of 2 mol% shows a dielectric constant tunability of 37.1% and a dielectric loss of 0.008 at the paraelectric state.

Effect of SiCp Addition on Aqueous Tape Casting of LAS Glass-Ceramic Powders

Effect of SiCp Addition on Aqueous Tape Casting of LAS Glass-Ceramic Powders

Interfacial tensile strength between polymethylmethacrylate-based bioactive bone cements and bone.

We have developed two types of polymethylmethacrylate (PMMA)-based bioactive bone cements containing bioactive glass beads (designated GBC) or apatite-wollastonite containing glass-ceramic powder (designated AWC) as the filler. A new method was used to evaluate the bone-cement interfacial strength of these bioactive bone cements. Two types of bioactive bone cements (GBC and AWC) and PMMA cement (CMW-1) were put in a frame attached to the smooth tibial metaphyseal cortex of the rabbit and polymerized in situ. The load required to detach the cement from the bone was measured at 4, 8, and 16 weeks after implantation. The interfacial tensile strength of GBC and AWC showed significantly higher values than PMMA cement from 4 weeks, and increased with time. For GBC, strength reached a maximum value of 12.39 +/- 1.79 kgf 16 weeks after implantation. Histological examination of rabbit tibiae up to 16 weeks demonstrated no intervening layer between the bioactive bone cements and the bone, whereas fibrous tissue was observed at the interface between the PMMA cement and the bone. From this study, we conclude that PMMA-based bioactive bone cements have a relatively higher adhesiveness at the interface than the conventionally used PMMA cement, showing potential as a promising alternative.

Bone-Bonding Strength of Two Kinds of Polymethylmethacrylate-Based Bioactive Bone Cement Containing Bioactive Glass Beads or Glass-Ceramic Powder

Bone-Bonding Strength of Two Kinds of Polymethylmethacrylate-Based Bioactive Bone Cement Containing Bioactive Glass Beads or Glass-Ceramic Powder

Bioactive bone cement: effects of phosphoric ester monomer on mechanical properties and osteoconductivity.

A new bioactive bone cement, designated GBC, has been developed. It consists of polymethyl methacrylate (PMMA) as an organic matrix and bioactive glass beads as an inorganic filler. The bioactive beads, consisting of MgO--CaO--SiO(2)--P(2)O(5)--CaF(2) glass, have been newly designed, and a novel PMMA powder was selected. The purpose of the present study was to evaluate the effects on mechanical properties and osteoconductivity of adding a phosphoric ester (PE) monomer to the cement as an adhesion-promoting agent. Four kinds of cements were prepared: GBC, GBC with PE (designated GBC/PE), a cement consisting of the same PMMA used in GBC with apatite- and wollastonite-containing glass-ceramic (AW-GC) powder (designated AWC), and AWC with PE (designated AWC/PE). Each filler was added to the cement at 70 wt %. Adding PE to either GBC or AWC resulted in increases in the bending strength and decreases in the Young's modulus compared with the unmodified cements. Cements were packed into the intramedullar canals of rat tibiae to evaluate osteoconductivity as determined by an affinity index. Rats were sacrificed at 4 and 8 weeks after operation. The affinity index (length of bone in direct contact with the cement expressed as a percentage of the total length of the cement surface) was calculated for each cement. Adding PE to either GBC or AWC resulted in significant increases in the affinity index compared with the unmodified cements. The affinity index for GBC was significantly higher than that of AWC, and that for GBC/PE was also significantly higher than that of AWC/PE. The affinity indices for each cement increased significantly with time up to 8 weeks. Our study revealed that the higher osteoconductivity of GBC/PE was due to the large alkyl group in the PE monomer, to the hydrophilicity of the phosphoric acid in the PE monomer, and to the higher bioactivity of the bioactive glass beads at the cement surface. GBC/PE shows promise as an alternative bone cement with improved properties compared with conventional PMMA bone cement.

Microstructure and mechanical properties of SiC platelet reinforced BaOAl 2O 32SiO 2 (BAS) composites

BaOAl 2O 32SiO 2 (BAS) glass–ceramic powders were prepared by sol–gel technique. SiC platelet reinforced BAS glass–ceramic matrix composites with high density and uniform microstructure were fabricated by hot-pressing. The effect of additional crystalline seeds on hexagonal to monoclinic phase transformation of Barium aluminosilicate was studied. The effects of SiC platelet content on the microstructure and mechanical properties of the composites were also investigated. The results showed that the flexural strength and fracture toughness of the BAS glass–ceramic matrix composites can be effectively improved by the addition of silicon carbide platelets. The main toughening mechanism was crack deflection, platelets' pull-out and bridging. The increased value of flexural strength is contributed to the load transition from the matrix to SiC platelets.

Bioactive bone cement: effect of surface curing properties on bone-bonding strength.

The fact that bisphenol-a-glycidyl methacrylate (bis-GMA)-based cements contain an uncured surface is believed to play an important role when determining the surface curing properties of the cements. Therefore, in the present study, the bone-bonding strength of cement plates having an uncured surface on one side and a cured surface on the other side has been evaluated. These cement plates were composites of a bis-GMA-based resin with either an apatite- and wollastonite-containing glass-ceramic (AW-GC) powder or a hydroxyapatite (HA) powder, respectively designated AWC and HAC. The amount of each of these powders in a composite cement was 70 wt %. We formulate the hypothesis that the uncured surface of a cement plate is bioactive having bone-bonding properties. The goal of the present study was to indicate the bone-bonding strength of the uncured surfaces of AWC and HAC and compare the strength with the respective cured surfaces by a detaching in vivo test, as well as to histologically examine the bone-cement interface. Each plate has been implanted into the tibiae of male Japanese white rabbits, taking care to retain the surface properties, and the so-called "failure load has been measured using a detaching test followed 8 weeks after implantation. The failure load for AWC-plates at the uncured surface (2.05 +/- 1.11 kgf, n = 8) was significantly higher than AWC at its cured surface side (0.28 +/- 0.64 kgf, n = 8). The failure load for HAC-plates at the uncured surfaces (1.40 +/- 0.68 kgf, n = 8) was significantly higher than HAC at its cured surface (0.00 +/- 0.00 kgf, n = 8). Failure loads for AWC at its uncured and cured surfaces were both higher than for HAC, although not significantly. Direct bone formation has been observed histologically for both AWC and HAC on the uncured surfaces, and a Ca-P-rich layer was observed only at the uncured surface of AWC. These findings strongly suggest that uncured surfaces are useful for exposing a bioactive filler on a surface of composites, being very effective in inducing bone bonding.

Effect of silane treatment and different resin compositions on biological properties of bioactive bone cement containing apatite-wollastonite glass ceramic powder.

In methylmethacrylate (MMA)-based cements containing bioactive particles, polymethylmetacrylate (PMMA) is known to suppress the bioactivity of Bioglass(R) and apatite-wollastonite glass ceramic (AW-GC). Little is known about the effect of different silane treatment methods on the bioactivity of AW-GC. MMA-based cement plates containing dry silanated AW-GC particles and PMMA particles of different molecular weights (12,000-900,000) were immersed in simulated body fluid (SBF). Cements containing PMMA particles of high molecular weight formed an apatite layer on the surface after 24 h. Using PMMA particles with a molecular weight of 60,000 and AW-GC particles silanated with different methods (dry method vs. slurry method), cement plates were made and immersed in SBF. Only cement plates containing dry silanated AW-GC particles showed apatite formation in SBF after 3 days. In vivo implantation in rat tibias of MMA-based cement containing dry silanated AW-GC particles and PMMA particles (molecular weight 900,000) demonstrated an affinity index of 32.1 +/- 15.8% after 8 weeks of implantation compared to 89.4 +/- 10.7% achieved by bisphenol-A-glycidyl methacrylate based cement containing the same bioactive powder. By using a dry method of silane treatment and high molecular weight PMMA particles, the bioactivity of cement based on MMA monomer was achieved; but further effort is needed to improve the mechanical properties of the composite.

Preparation and properties of barium-ferrite-containing glass ceramics

Magnetic properties of magnetic ceramics are dependent on the magnetisation processes. They are usually dominated by Bloch-wall displacements in multi-domain structures of the sintered magnetic material, even if the starting powder material shows single-domain Stoner–Wohlfarth behaviour. Domain wall motion limits in several cases the quality of magnetic materials for special applications like permanent magnets or rf devices. We have developed a new type of magnetic powder preparation which permits the fabrication of compact glass ceramics containing Ba-ferrite maintaining the single-domain behaviour of the starting powder. This technology is based on the glass crystallisation method for the precipitation of single-domain Ba-ferrite particles in a quenched melt of Fe 2O 3–BaO–B 2O 3(-SiO 2). By milling the crystallized melt or leaching out the borate from the SiO 2-containing glass, a glass ceramic powder containing Ba-ferrite can be produced, which can be sintered at moderate temperatures providing a dense compact glass ceramic containing up to 90 wt% Ba-ferrite. This compact glass ceramic shows the same single-domain behaviour as the starting powders, i.e. it also possesses the high coercivities of hard magnetic material.

Study of the sol–gel processing of glass-ceramic powders in the SiO 2–Al 2O 3–CaO–CaF 2 system. I. Effect of powder composition on gel time and temperature

To determine the effect of powder composition on gel time and temperature, 12 sol–gel derived glasses in the SiO 2–Al 2O 3–CaO–CaF 2 system with different compositions chosen from a 21-point design generated through the mixture design technique were synthesised. Gel times varied from a few seconds at room temperature to a few hours at 75°C, as the fluoride content was increased. The longest gel times were observed for those compositions with the largest amounts of aluminium regardless of their fluoride ion concentrations. As the fluoride ion concentration was increased, the effect of both silicon and calcium concentrations on the gel times became gradually smaller. Accordingly, gel temperatures were found to vary from 75°C, for glasses with low fluoride content (3 mol% as H 2SiF 6), to room temperature, for those with higher fluoride contents (9 and 15 mol% as H 2SiF 6). Experimental data on the compositional dependence of gel time for the system studied was fitted using a quadratic model, with a square multiple correlation coefficient of 0.9962.

Osteoconductivity and bone-bonding strength of high- and low-viscous bioactive bone cements.

A study was conducted to evaluate the osteoconductivity and bone-bonding ability of two types of bioactive bone cement, both consisting of apatite and wollastonite containing glass-ceramic powder (AW-P), fused silica glass powder (SG-P), submicron fumed silica as an inorganic filler, and bisphenol-a-glycidyl methacrylate (Bis-GMA) based resin as an organic matrix. The cements had two kinds of formulas: one (dough-type cement; designated DTC) composed of 85% (w/w) filler and 15% resin, which was developed for fixation of the acetabular component in total hip arthroplasty and could be handled manually; and one (injection-type cement; designated ITC) composed of 79% (w/w) filler and 21% resin. ITC was developed for fixation of the femoral component and, because it had a lower viscosity than DTC, could be injected. The DTC and ITC both contained 73% AW-P, 25% SG-P, and 2% fumed silica in the weight ratio of the filler component. Two other types of cement, both of which consisted of 83.3% AW-P or SG-P, 1.7% fumed silica, and 15% resin, were used as reference material (designated AWC or SGC) for a detaching test. Following the packing of bone defects in the rat tibiae with either DTC or ITC, histological examination revealed that the DTC and ITC had both directly contacted the bone and were almost completely surrounded by bone by 16 weeks after the surgery and that no marked biodegradation had occurred at 52 weeks postimplantation. Rectangular plates (2 x 10 x 15 mm) of AWC, DTC, ITC, and SGC were implanted into the metaphysis of the tibia of male rabbits and the failure load was measured by a detaching test at 10 and 25 weeks after implantation. The failure loads of AWC, DTC, ITC, and SGC were 3.65, 2.21, 2.44, and 0.04 kgf at 10 weeks and 4.87, 2. 81, 2.82, and 0.13 kgf at 25 weeks, respectively. Observation of the bone-implant interface by scanning electron microscopy and energy dispersive X-ray microanalysis revealed that all the samples except SGC formed direct contact with the bone and that only AWC-implanted tibiae had a layer of a low calcium and phosphorus level at the bone-implant interface. Results showed that DTC and ITC have excellent osteoconductivity and bone-bonding ability under non-weight-bearing conditions.

Effects of water-soluble component content on cephalexin release from bioactive bone cement consisting of bis-GMA/TEGDMA resin and bioactive glass ceramics.

The effect of the amount of a water-soluble, lactose, on cephalexin (CEX) release from bioactive bone cement consisting of bisphenol-alpha-glycidyl methacrylate (bis-GMA), triethylene-glycol dimethacrylate (TEGDMA) resin and apatite- and wollastonite-containing glass-ceramic (A-W GC) powder was investigated. A-W GC powder containing 5% CEX and lactose powders hardened within 5 min after mixing with bis-GMA/TEGDMA resin, and furthermore its compressive strength was expected to be higher than that of polymethylmethacrylate cement. In vitro CEX release from bioactive bone cement pellets in a simulated body fluid at pH 7.25 and 37 degrees C continued for more than 2 wk. The drug-release rate increased with increasing amount of lactose powder in the mixture. CEX release profiles followed the Higuchi equation in the initial stage, but not in later stages. As hydroxyapatite was precipitated out on the cement surface, the CEX release rate decreased. The micropore distribution of the cements measured by mercury porosimetry also supported the variation in drug release due to cement porosity being mainly a result of the dissolution of lactose in the cements. These results suggest that the rate of CEX release from bioactive bone cement could be controlled by varying the amount of lactose in the cement system.

Effect of TiO2 addition on the preparation of β-spodumene powders by sol-gel process

This study has shown the possibility of achieving two primary considerations for the advanced fabrication of spodumene with a composition of Li2O · Al2O3 · 4SiO2 · nTiO2 (LAST) glass-ceramics by a sol-gel process, namely, an enormous reduction of sintering temperature from 1600 to 1200 °C together with the appearance of simple phases of β-spodumene/rutile as opposed to products via the conventional melting-crystallization process. Fine glass-ceramic powders with a composition of Li2O · Al2O3 · 4SiO2 (LAS) have been synthesized by the sol-gel process using Si(OC2H5)4, Al(OC2H5)3, LiOCH3, and Ti(OC2H5)4 as the starting materials. The process included well-controlled hydrolysis polycondensation of the raw alkoxides. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron diffraction (ED) analysis were utilized to study the effect of TiO2 addition on the preparation of β-spodumene powders by the sol-gel process. The gelation time of the LAST solution increases as the TiO2 content increases. For the low (<3) or high (>11) pH value, the gelation time was shortened. At pH = 5, regardless of the TiO2 content, the gel has the longest time of gelation. When the dried gels of the LAST system are heated from 800 to 1200 °C, the crystallized samples are composed of the major phase of β-spodumene and a minor phase of rutile (TiO2).

Effect of Heating Cycle on the Structure of Ag Films Deposited over Porcelain Substrates

Silver films were deposited over porcelain substrates by using flexible adhesive transfer layers. These films were produced in order to use porcelain utensils over household induction heating plates. Mixtures of different glass ceramic powders with silver powder are used to prepare the self-transfer patterns. These patterns are deposited over porcelain substrates and sintered using different heating cycles. One defect observed in such films is the presence of porosity either at the Ag/porcelain interface or inside the Ag film structure. While lower sintering temperatures produce less porosity, the microstructure of the Ag layer at lower temperatures is no longer composed of a contiguous network of large silver agglomerates. Consequently, the heating capability of the layer through electromagnetic induction is affected. Finally a sintering cycle is proposed for which the film properties are least modified with a minimum level of porosity.

Bioactive bone cement: comparison of apatite and wollastonite containing glass-ceramic, hydroxyapatite, and beta-tricalcium phosphate fillers on bone-bonding strength.

A study was conducted to compare the bone-bonding strengths of three types of bioactive bone cement, consisting of either apatite- and wollastonite-containing glass-ceramic (AW-GC) powder, hydroxyapatite (HA) powder, or beta-tricalcium phosphate (beta-TCP) powder as an inorganic filler and bisphenol-a-glycidyl methacrylate (Bis-GMA) based resin as an organic matrix. Seventy percent (w/w) filler was added to the cement. Rectangular plates (10 x 15 x 2 mm) of each cement were made and abraded with #2000 alumina powder. After soaking in simulated body fluid for 2 days, the AW cement (AWC) and HA cement (HAC) formed bonelike apatite over their entire surfaces, but the TCP cement (TCPC) did not. Plates of each type of cement were implanted into the tibial metaphyses of male Japanese white rabbits, and the failure loads were measured by a detaching test at 10 and 25 weeks after implantation. The failure loads of AWC, HAC, and TCPC were 3.95, 2.04, and 2.03 kgf at 10 weeks and 4.36, 3.45, and 3.10 kgf at 25 weeks, respectively. The failure loads of the AWC were significantly higher than those of the HAC and TCPC at 10 and 25 weeks. Histological examination by contact microradiogram and Giemsa surface staining of the bone-cement interface revealed that all the bioactive bone cements were in direct contact with bone. However, scanning electron microscopy and energy-dispersive X-ray microanalysis showed that only AWC had contacted to the bone via a Ca-P rich layer formed at the interface between the AW-GC powder and the bone, which might explain its high bone-bonding strength. Neither the HAC nor the TCPC contacted the bone through such a layer between each powder and the bone, although the HAC and TCPC directly contacted with bone. Our results indicate that all three types of abraded and prefabricated cement have bonding strength to bone, but AWC has superior bone-bonding strength compared to HAC and TCPC.