The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform
Kunio Ishikawa - One of the best experts on this subject based on the ideXlab platform.
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bone regeneration using β tricalcium phosphate β tcp block with interconnected pores made by Setting Reaction of β tcp granules
Journal of Biomedical Materials Research Part A, 2020Co-Authors: Tansza Setiana Putri, Koichiro Hayashi, Kunio IshikawaAbstract:We fabricated an interconnected dual porous β-tricalcium phosphate (β-TCP) block via a Setting Reaction of β-TCP granules. This β-TCP block was unique because it exhibits a fully interconnected macroporous structure with micropores in the walls surrounding macropores and a roughened surface. The porosity and diametral tensile strength of the resulting product were 58.1 ± 1.7% and 1.4 ± 0.2 MPa, respectively. Rabbit distal femur bone defects were reconstructed using the porous β-TCP block and the efficacy of the porous β-TCP block as an artificial bone substitute was evaluated histomorphometrically. For a dense β-TCP control, 4 weeks following implantation, only 0.2 ± 0.1% of the β-TCP was resorbed, and the amount of newly formed bone was limited (0.1 ± 0.1%), whereas when the defect was reconstructed with porous β-TCP, 9.2 ± 3.1% was resorbed, and the amount of new bone was 18.9 ± 5.5%. This represents an approximately 50-fold enhancement in resorption and a 200-fold increase in bone formation for our porous β-TCP block. Therefore, interconnected dual porous β-TCP made via β-TCP granule Setting has good potential as an artificial bone substitute.
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Bone regeneration using β‐tricalcium phosphate (β‐TCP) block with interconnected pores made by Setting Reaction of β‐TCP granules
Journal of biomedical materials research. Part A, 2019Co-Authors: Tansza Setiana Putri, Koichiro Hayashi, Kunio IshikawaAbstract:We fabricated an interconnected dual porous β-tricalcium phosphate (β-TCP) block via a Setting Reaction of β-TCP granules. This β-TCP block was unique because it exhibits a fully interconnected macroporous structure with micropores in the walls surrounding macropores and a roughened surface. The porosity and diametral tensile strength of the resulting product were 58.1 ± 1.7% and 1.4 ± 0.2 MPa, respectively. Rabbit distal femur bone defects were reconstructed using the porous β-TCP block and the efficacy of the porous β-TCP block as an artificial bone substitute was evaluated histomorphometrically. For a dense β-TCP control, 4 weeks following implantation, only 0.2 ± 0.1% of the β-TCP was resorbed, and the amount of newly formed bone was limited (0.1 ± 0.1%), whereas when the defect was reconstructed with porous β-TCP, 9.2 ± 3.1% was resorbed, and the amount of new bone was 18.9 ± 5.5%. This represents an approximately 50-fold enhancement in resorption and a 200-fold increase in bone formation for our porous β-TCP block. Therefore, interconnected dual porous β-TCP made via β-TCP granule Setting has good potential as an artificial bone substitute.
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Effects of acidic calcium phosphate concentration on Setting Reaction and tissue response to β-tricalcium phosphate granular cement.
Journal of biomedical materials research. Part B Applied biomaterials, 2019Co-Authors: Naoyuki Fukuda, Kunio Ishikawa, Kazuya Akita, Kumiko Kamada, Naito Kurio, Yoshihide Mori, Youji MiyamotoAbstract:Beta-tricalcium phosphate granular cement (β-TCP GC), consisting of β-TCP granules and an acidic calcium phosphate (Ca-P) solution, shows promise in the reconstruction of bone defects as it sets to form interconnected porous structures, that is, β-TCP granules are bridged with dicalcium phosphate dihydrate (DCPD) crystals. In this study, the effects of acidic Ca-P solution concentration (0-600 mmol/L) on the Setting Reaction and tissue response to β-TCP GC were investigated. The β-TCP GC set upon mixing with its liquid phase, based on the formation of DCPD crystals, which bridged β-TCP granules to one another. Diametral tensile strength of the set β-TCP GC was relatively the same, at ∼0.6 MPa, when the Ca-P concentration was 20-600 mmol/L. Due to the Setting ability, reconstruction of the rat's calvarial bone defect using β-TCP GC with 20, 200, and 600 mmol/L Ca-P solution was much easier compared to that with β-TCP granules without Setting ability. Four weeks after the reconstruction, the amount of new bone was the same, ∼17% in both β-TCP GC and β-TCP granules groups. Cellular response to β-TCP granules and β-TCP GC using the 20 mmol/L acidic Ca-P solution was almost the same. However, β-TCP GC using the 200 and 600 mmol/L acidic Ca-P solution showed a more severe inflammatory Reaction. It is concluded, therefore, that β-TCP GC, using the 20 mmol/L acidic Ca-P solution, is recommended as this concentration allows surgical techniques to be performed easily and provides good mechanical strength, and the similar cellular response to β-TCP granules. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:22-29, 2020.
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Fabrication of interconnected porous β-tricalcium phosphate (β-TCP) based on a Setting Reaction of β-TCP granules with HNO3 followed by heat treatment.
Journal of biomedical materials research. Part A, 2017Co-Authors: Kunio Ishikawa, Tansza Setiana Putri, Akira Tsuchiya, Keisuke Tanaka, Kanji TsuruAbstract:β-Tricalcium phosphate [β-TCP] is the typical bone substitute due to its excellent osteoconductivity and bioresorbability. One of the keys to improve its potential as bone substitute is to introduce porous structure and its regulation. In this study, interconnected porous β-TCP blocks were fabricated through a Setting Reaction of β-TCP granules and subsequent heat treatment. First, β-TCP granules were mixed with HNO3 . Upon mixing, β-TCP granules were bridged with dicalcium phosphate dihydrate [DCPD: CaHPO4 ·2H2 O] containing Ca(NO3 )2 . Then, the DCPD-bridged β-TCP was heated at 1100°C. During the heating process, DCPD containing Ca(NO3 )2 transformed into β-TCP and bonded with β-TCP granules. As a result, an interconnected porous β-TCP block formed. The diametral tensile strength and porosity of the interconnected porous β-TCP block fabricated from 200-300-μm β-TCP granules and 5 N HNO3 and then heated at 1,100°C were 1.4 ± 0.2 MPa and 57% ± 2%, respectively. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 797-804, 2018.
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Effect of citric acid on Setting Reaction and tissue response to β-TCP granular cement.
Biomedical materials (Bristol England), 2017Co-Authors: Naoyuki Fukuda, Kanji Tsuru, Yoshihide Mori, Kunio IshikawaAbstract:We recently reported that when an acidic calcium phosphate solution is mixed with β-tricalcium phosphate (β-TCP) granules, the resulting dicalcium phosphate dihydrate (DCPD) crystals form bridges between the β-TCP granules, creating a set interconnected porous structure in approximately 1 min. Although this self-Setting β-TCP granular cement (β-TCPGC) is useful for clinical applications, the short Setting time is a key drawback for handling. In this study, the Setting time of β-TCPGC was adjusted with the addition of citric acid, which is a known inhibiter of DCPD crystal growth. As the concentration of citric acid in the acidic calcium phosphate solution increased, the amount of DCPD formation in the set β-TCPGC decreased, and the crystal morphology of DCPD became elongated. β-TCPGC prepared with various citric acid concentrations were used as grafting material in rat calvarial bone defects to evaluate bone regeneration in vivo. Four weeks after implantation, no inflammatory Reaction and approximately 20% new bone formation were observed, regardless of the presence or absence of citric acid in the liquid phase of β-TCPGC. We concluded, therefore, that citric acid might be a useful retarder of β-TCPGC Setting times.
Kanji Tsuru - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of interconnected porous β-tricalcium phosphate (β-TCP) based on a Setting Reaction of β-TCP granules with HNO3 followed by heat treatment.
Journal of biomedical materials research. Part A, 2017Co-Authors: Kunio Ishikawa, Tansza Setiana Putri, Akira Tsuchiya, Keisuke Tanaka, Kanji TsuruAbstract:β-Tricalcium phosphate [β-TCP] is the typical bone substitute due to its excellent osteoconductivity and bioresorbability. One of the keys to improve its potential as bone substitute is to introduce porous structure and its regulation. In this study, interconnected porous β-TCP blocks were fabricated through a Setting Reaction of β-TCP granules and subsequent heat treatment. First, β-TCP granules were mixed with HNO3 . Upon mixing, β-TCP granules were bridged with dicalcium phosphate dihydrate [DCPD: CaHPO4 ·2H2 O] containing Ca(NO3 )2 . Then, the DCPD-bridged β-TCP was heated at 1100°C. During the heating process, DCPD containing Ca(NO3 )2 transformed into β-TCP and bonded with β-TCP granules. As a result, an interconnected porous β-TCP block formed. The diametral tensile strength and porosity of the interconnected porous β-TCP block fabricated from 200-300-μm β-TCP granules and 5 N HNO3 and then heated at 1,100°C were 1.4 ± 0.2 MPa and 57% ± 2%, respectively. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 797-804, 2018.
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Effect of citric acid on Setting Reaction and tissue response to β-TCP granular cement.
Biomedical materials (Bristol England), 2017Co-Authors: Naoyuki Fukuda, Kanji Tsuru, Yoshihide Mori, Kunio IshikawaAbstract:We recently reported that when an acidic calcium phosphate solution is mixed with β-tricalcium phosphate (β-TCP) granules, the resulting dicalcium phosphate dihydrate (DCPD) crystals form bridges between the β-TCP granules, creating a set interconnected porous structure in approximately 1 min. Although this self-Setting β-TCP granular cement (β-TCPGC) is useful for clinical applications, the short Setting time is a key drawback for handling. In this study, the Setting time of β-TCPGC was adjusted with the addition of citric acid, which is a known inhibiter of DCPD crystal growth. As the concentration of citric acid in the acidic calcium phosphate solution increased, the amount of DCPD formation in the set β-TCPGC decreased, and the crystal morphology of DCPD became elongated. β-TCPGC prepared with various citric acid concentrations were used as grafting material in rat calvarial bone defects to evaluate bone regeneration in vivo. Four weeks after implantation, no inflammatory Reaction and approximately 20% new bone formation were observed, regardless of the presence or absence of citric acid in the liquid phase of β-TCPGC. We concluded, therefore, that citric acid might be a useful retarder of β-TCPGC Setting times.
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Fabrication of interconnected porous calcium-deficient hydroxyapatite using the Setting Reaction of α tricalcium phosphate spherical granules
Ceramics International, 2017Co-Authors: Tya Indah Arifta, Kanji Tsuru, Melvin L. Munar, Kunio IshikawaAbstract:Abstract Interconnected porous calcium-deficient hydroxyapatite (cdHAp) blocks may be an ideal biomaterial to repair bone defects because of their greater similarity to human bone than that of sintered hydroxyapatite (HAp) with respect to calcium content and crystallinity. In particular, the interconnected pores in cdHAp may provide pathways for cell migration and tissue ingrowth. In this study, the feasibility of fabricating interconnected porous cdHAp blocks through the Setting Reaction of alpha-tricalcium phosphate (αTCP) spherical granules was investigated. It was found that regulation of cdHAp formation was important to fabricate interconnected porous cdHAp blocks. That is, cdHAp needed to precipitate preferentially at the contacting areas between αTCP spherical granules. Exposure of αTCP spherical granules to steam under appropriate pressure was effective for this purpose. When αTCP spherical granules were immersed in water at 100 °C, the Setting Reaction resulted in dense cdHAp blocks because of the free crystal growth of cdHAp in water. Therefore, steam was used to localize the water at the contacting areas between αTCP spherical granules, which was driven by the surface tension of the water. Without an applied load, no Setting Reaction was observed when αTCP spherical granules were exposed to steam at 100 °C for 12 h. In contrast, under a load of 20 MPa, cdHAp precipitated to bridge spherical granules, providing an interconnected porous cdHAp block. The porosity and diametral tensile strength of this block were approximately 63% and 1.5 MPa, respectively.
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Fabrication of carbonate apatite foam based on the Setting Reaction of α-tricalcium phosphate foam granules
Ceramics International, 2016Co-Authors: Yuki Sugiura, Kanji Tsuru, Kunio IshikawaAbstract:Carbonate apatite (CO3Ap) foam has attracted attention as a bone substitute and scaffold for tissue regeneration. In this study, the feasibility of fabricating CO3Ap foam was evaluated on the basis of the Setting Reaction of α-tricalcium phosphate (α-TCP) foam granules. CO3Ap foam was formed when α-TCP foam granules were treated hydrothermally at 200 °C in the presence of NaHCO3 solution for 24 h. The precipitated CO3Ap crystals interlocked with each other to form the CO3Ap foam. The CO3Ap formed in high NaHCO3 containing solution was considered to be a B-type CO3Ap, which is the CO3Ap found in bones and contained 0.85 mass% CO3. When the α-TCP foam granules were treated at higher NaHCO3 solution, the content of the CO3 in the apatitic structure increased and changed the morphology of the CO3Ap from fiber-like to plate-like with a smaller aspect ratio; thus, the Setting ability disappeared.
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Setting Reaction of α-TCP spheres and an acidic calcium phosphate solution for the fabrication of fully interconnected macroporous calcium phosphate
Ceramics International, 2015Co-Authors: Pham Trung Kien, Kunio Ishikawa, Kanji TsuruAbstract:Abstract Interconnected macroporous calcium phosphate has attracted attention as an artificial bone substitute as well as a scaffold for tissue engineering. In this investigation, a Setting Reaction between α-tricalcium phosphate (α-TCP) spheres and an acidic calcium phosphate solution (0.2 mol/L monocalcium phosphate monohydrate – 0.1 mol/L phosphoric acid) was studied to assess the feasibility of fabricating fully interconnected macroporous calcium phosphate. When 1.3 mm-diameter α-TCP spheres were exposed to an acidic calcium phosphate solution, brushite (dicalcium phosphate dihydrate) was formed on the surface of the α-TCP spheres. The precipitated brushite crystals interlocked with one another and bridged the α-TCP spheres, resulting in a 10 min Setting Reaction at 37 °C that produced fully interconnected macroporous calcium phosphate. The resultant calcium phosphate macroporous structure had a porosity of 49.7±2.5% and an average pore size of 312±160 μm.
Maria-pau Ginebra - One of the best experts on this subject based on the ideXlab platform.
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Robocasting of biomimetic hydroxyapatite scaffolds using self-Setting inks
Journal of materials chemistry. B, 2014Co-Authors: Yassine Maazouz, Cecilia Persson, Edgar B. Montufar, Jordi Guillem-marti, Ingmar Fleps, Caroline Öhman, Maria-pau GinebraAbstract:Low temperature self-Setting ceramic inks have been scarcely investigated for solid freeform fabrication processes. This work deals with the robocasting of alpha-tricalcium phosphate/gelatine reactive slurries as a bioinspired self-Setting ink for the production of biomimetic hydroxyapatite/gelatine scaffolds. A controlled and totally interconnected pore network of ∼300 μm was obtained after ink printing and Setting, with the struts consisting of a micro/nanoporous matrix of needle-shaped calcium deficient hydroxyapatite crystals, with a high specific surface area. Gelatine was effectively retained by chemical crosslinking. The Setting Reaction of the ink resulted in a significant increase of both the elastic modulus and the compressive strength of the scaffolds, which were within the range of the human trabecular bone. In addition to delaying the onset of the Setting Reaction, thus providing enough time for printing, gelatine provided the viscoelastic properties to the strands to support their own weight, and additionally enhanced mesenchymal stem cell adhesion and proliferation on the surface of the scaffold. Altogether this new processing approach opens good perspectives for the design of hydroxyapatite scaffolds for bone tissue engineering with enhanced reactivity and resorption rate.
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Relevance of the Setting Reaction to the injectability of tricalcium phosphate pastes
Acta biomaterialia, 2012Co-Authors: Edgar B. Montufar, Yassine Maazouz, Maria-pau GinebraAbstract:The aim of the present work was to analyze the influence of the Setting Reaction on the injectability of tricalcium phosphate (TCP) pastes. Even if the injection was performed early after mixing powder and liquid, powder reactivity was shown to play a significant role in the injectability of TCP pastes. Significant differences were observed between the injection behavior of non-hardening β-TCP pastes and that of self-hardening α-TCP pastes. The differences were more marked at low liquid-to-powder ratios, using fine powders and injecting through thin needles. α-TCP was, in general, less injectable than β-TCP and required higher injection loads. Moreover, clogging was identified as a mechanism hindering or even preventing injectability, different and clearly distinguishable from the filter-pressing phenomenon. α-TCP pastes presented transient clogging episodes, which were not observed in β-TCP pastes with equivalent particle size distribution. Different parameters affecting powder reactivity were also shown to affect paste injectability. Thus, whereas powder calcination resulted in an increased injectability due to lower particle reactivity, the addition of Setting accelerants, such as hydroxyapatite nanoparticles, tended to reduce the injectability of the TCP pastes, especially if adjoined simultaneously with a Na2HPO4 solution. Although, as a general trend, faster-Setting pastes were less injectable, some exceptions to this rule were found. For example, whereas in the absence of Setting accelerants fine TCP powders were more injectable than the coarse ones, in spite of their shorter Setting times, this trend was inverted when Setting accelerants were added, and coarse powders were more injectable than the fine ones.
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Porous hydroxyapatite and gelatin/hydroxyapatite microspheres obtained by calcium phosphate cement emulsion
Journal of Biomedical Materials Research - Part B Applied Biomaterials, 2011Co-Authors: Roman A. Perez, Sergio Del Valle, George Altankov, Maria-pau GinebraAbstract:Hydroxyapatite and hybrid gelatine/hydroxyapatite microspheres were obtained through a water in oil emulsion of a calcium phosphate cement (CPC). The Setting Reaction of the CPC, in this case the hydrolysis of α-tricalcium phosphate, was responsible for the consolidation of the microspheres. After the Setting Reaction, the microspheres consisted of an entangled network of hydroxyapatite crystals, with a high porosity and pore sizes ranging between 0.5 and 5 μm. The size of the microspheres was tailored by controlling the viscosity of the hydrophobic phase, the rotation speed, and the initial powder size of the CPC. The incorporation of gelatin increased the sphericity of the microspheres, as well as their size and size dispersion. To assess the feasibility of using the microspheres as cell microcarriers, Saos-2 cells were cultured on the microspheres. Fluorescent staining, SEM studies, and LDH quantification showed that the microspheres were able to sustain cell growth. Cell adhesion and proliferation was significantly improved in the hybrid gelatin/hydroxyapatite microspheres as compared to the hydroxyapatite ones.
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The cement Setting Reaction in the CaHPO4-α-Ca3(PO4)2 system: An X-ray diffraction study
Journal of biomedical materials research, 1998Co-Authors: Enrique Fernández, Maria-pau Ginebra, F. C. M. Driessens, Serena Best, F. J. Gil, J. A. PlanellAbstract:The Setting Reactions of calcium phosphate cements in the CaHPO4-alpha-Ca3(PO4)2 (DCP-alpha-TCP) system have been investigated. X-ray diffraction (XRD) analyses were performed on DCP-alpha-TCP cement samples of varying calcium to phosphorus (Ca/P) ratios after Setting for 24 h in Ringer's solution at 37 degrees C. XRD measurements showed that the intensity of the DCP peaks decreased linearly as the Ca/P ratio of the mixture increased. However, the intensity of the peaks of a new calcium-deficient hydroxyapatite [CDHA; Ca9(HPO4)(PO4)5OH] precipitating phase increased linearly as the Ca/P ratio increased. Alpha-TCP was not detected after 24 h of Setting in any sample. A two-phase mixture XRD model was applied to explain the results, and suitable fits were obtained between observed and expected values of the relevant peak heights. The method used for this study also can be applied to studies of the kinetic behavior of other cement systems.
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Setting Reaction and Hardening of an Apatitic Calcium Phosphate Cement
Journal of dental research, 1997Co-Authors: Maria-pau Ginebra, Enrique Fernández, E.a.p. De Maeyer, Ronald Verbeeck, M. G. Boltong, Josep Ginebra, F. C. M. Driessens, J. A. PlanellAbstract:The combination of self-Setting and biocompatibility makes calcium phosphate cements potentially useful materials for a variety of dental applications. The objective of this study was to investigate the Setting and hardening mechanisms of a cement-type Reaction leading to the formation of calcium-deficient hydroxyapatite at low temperature. Reactants used were alpha-tricalcium phosphate containing 17 wt% beta-tricalcium phosphate, and 2 wt% of precipitated hydroxyapatite as solid phase and an aqueous solution 2.5 wt% of disodium hydrogen phosphate as liquid phase. The transformation of the mixture was stopped at selected times by a freeze-drying techniques, so that the cement properties at various stages could be studied by means of x-ray diffraction, infrared spectroscopy, and scanning electron microscopy. Also, the compressive strength of the cement was measured as a function of time. The results showed that: (1) the cement Setting was the result of the alpha-tricalcium phosphate hydrolysis, giving as a product calcium-deficient hydroxyapatite, while beta-tricalcium phosphate did not participate in the Reaction; (2) the extent of conversion of alpha-TCP was nearly 80% after 24 hr; (3) both the extent of conversion and the compressive strength increased initially linearly with time, subsequently reaching a saturation level, with a strong correlation observed between them, indicating that the microstructural changes taking place as the Setting Reaction proceeded were responsible for the mechanical behavior of the cement; and (4) the microstructure of the set cement consisted of clusters of big plates with radial or parallel orientations in a matrix of small plate-like crystals.
J. A. Planell - One of the best experts on this subject based on the ideXlab platform.
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The cement Setting Reaction in the CaHPO4-α-Ca3(PO4)2 system: An X-ray diffraction study
Journal of biomedical materials research, 1998Co-Authors: Enrique Fernández, Maria-pau Ginebra, F. C. M. Driessens, Serena Best, F. J. Gil, J. A. PlanellAbstract:The Setting Reactions of calcium phosphate cements in the CaHPO4-alpha-Ca3(PO4)2 (DCP-alpha-TCP) system have been investigated. X-ray diffraction (XRD) analyses were performed on DCP-alpha-TCP cement samples of varying calcium to phosphorus (Ca/P) ratios after Setting for 24 h in Ringer's solution at 37 degrees C. XRD measurements showed that the intensity of the DCP peaks decreased linearly as the Ca/P ratio of the mixture increased. However, the intensity of the peaks of a new calcium-deficient hydroxyapatite [CDHA; Ca9(HPO4)(PO4)5OH] precipitating phase increased linearly as the Ca/P ratio increased. Alpha-TCP was not detected after 24 h of Setting in any sample. A two-phase mixture XRD model was applied to explain the results, and suitable fits were obtained between observed and expected values of the relevant peak heights. The method used for this study also can be applied to studies of the kinetic behavior of other cement systems.
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Synthesis of dahllite through a cement Setting Reaction.
Journal of materials science. Materials in medicine, 1998Co-Authors: Enrique Fernández, J. A. Planell, Serena Best, William BonfieldAbstract:Dahllite is a synthetic carbonated hydroxyapatite with a carbonate ion content similar to bone mineral. The first objective of this study was to investigate the stoichiometric conditions under which dahllite formation occurs in a powder mixture of alpha-Ca3(PO4)2, Ca(H2PO4)2 and CaCO3. The second objective was to identify how these conditions apply to commercially available cement, Skeletal Repair System (SRS), and other alpha-Ca3(PO4)2-based cements currently under investigation. The stoichiometric coefficients were found to be a function of both the percentage of carbonate ions incorporated into the hydroxyapatite structure, and the amount of CO2 released during the Reaction. As a consequence, a stability field has been obtained where different initial proportions of the reactants in the powder mixture should give the same Reaction product if sufficient CO2 is released into the solution. However, increasing amounts of CaCO3 in the initial mixture have been shown to affect the solution pH in such a way that only partial Reaction of the reactants takes place. SRS and other alpha-Ca3(PO4)2-based cements have been located inside the stability field and a comparison between their reported Setting and hardening properties has been performed.
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Setting Reaction and Hardening of an Apatitic Calcium Phosphate Cement
Journal of dental research, 1997Co-Authors: Maria-pau Ginebra, Enrique Fernández, E.a.p. De Maeyer, Ronald Verbeeck, M. G. Boltong, Josep Ginebra, F. C. M. Driessens, J. A. PlanellAbstract:The combination of self-Setting and biocompatibility makes calcium phosphate cements potentially useful materials for a variety of dental applications. The objective of this study was to investigate the Setting and hardening mechanisms of a cement-type Reaction leading to the formation of calcium-deficient hydroxyapatite at low temperature. Reactants used were alpha-tricalcium phosphate containing 17 wt% beta-tricalcium phosphate, and 2 wt% of precipitated hydroxyapatite as solid phase and an aqueous solution 2.5 wt% of disodium hydrogen phosphate as liquid phase. The transformation of the mixture was stopped at selected times by a freeze-drying techniques, so that the cement properties at various stages could be studied by means of x-ray diffraction, infrared spectroscopy, and scanning electron microscopy. Also, the compressive strength of the cement was measured as a function of time. The results showed that: (1) the cement Setting was the result of the alpha-tricalcium phosphate hydrolysis, giving as a product calcium-deficient hydroxyapatite, while beta-tricalcium phosphate did not participate in the Reaction; (2) the extent of conversion of alpha-TCP was nearly 80% after 24 hr; (3) both the extent of conversion and the compressive strength increased initially linearly with time, subsequently reaching a saturation level, with a strong correlation observed between them, indicating that the microstructural changes taking place as the Setting Reaction proceeded were responsible for the mechanical behavior of the cement; and (4) the microstructure of the set cement consisted of clusters of big plates with radial or parallel orientations in a matrix of small plate-like crystals.
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kinetic study of the Setting Reaction of a calcium phosphate bone cement
Journal of Biomedical Materials Research, 1996Co-Authors: Enrique Fernández, Maria-pau Ginebra, E.a.p. De Maeyer, Ronald Verbeeck, M. G. Boltong, Josep Ginebra, F. C. M. Driessens, J. A. PlanellAbstract:The Setting Reaction of a calcium phosphate bone cement consisting of a mixture of 63.2 wt % α-tertiary calcium phosphate (TCP)[α-Ca3(PO4)2], 27.7 wt % dicalcium phosphate (DCP) (CaHPO4), and 9.1 wt % of precipitated hydroxyapatite [(PHA) used as seed material] was investigated. The cement samples were prepared at a liquid-to-powder ratio of: L/P = 0.30 ml/g. Bi-distilled water was used as liquid solution. After mixing the powder and liquid, some samples were molded and aged in Ringer's solution at 37°C. At fixed time intervals they were unmolded and then immediately frozen in liquid nitrogen at a temperature of TN = -196°C, lyofilized, and examined by X-ray diffraction as powder samples. The compressive strength versus time was also measured in Setting samples of this calcium phosphate bone cement. The crystal entanglement morphology was examined by scanning electron microscopy. The results showed that: 1) α-TCP reacted to a calcium-deficient hydroxyapatite (CDHA), Ca9(HPO4)(PO4)5OH, whereas DCP did not react significantly; 2) the Reaction was nearly finished within 32 h, during which both the Reaction percentage and the compressive strength increased versus time, with a strong correlation between them; and 3) the calcium phosphate bone cement showed in general a structure of groups of interconnected large plates distributed among agglomerations of small crystal plates arranged in very dense packings. © 1996 John Wiley & Sons, Inc.
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Kinetic study of the Setting Reaction of a calcium phosphate bone cement.
Journal of biomedical materials research, 1996Co-Authors: Enrique Fernández, Maria-pau Ginebra, E.a.p. De Maeyer, Ronald Verbeeck, M. G. Boltong, Josep Ginebra, F. C. M. Driessens, J. A. PlanellAbstract:The Setting Reaction of a calcium phosphate bone cement consisting of a mixture of 63.2 wt % alpha-tertiary calcium phosphate (TCP)[alpha-Ca3(PO4)2], 27.7 wt % dicalcium phosphate (DCP) (CaHPO4), and 9.1 wt % of precipitated hydroxyapatite [(PHA) used as seed material] was investigated. The cement samples were prepared at a liquid-to-powder ratio of: L/P = 0.30 ml/g. Bi-distilled water was used as liquid solution. After mixing the powder and liquid, some samples were molded and aged in Ringer's solution at 37 degrees C. At fixed time intervals they were unmolded and then immediately frozen in liquid nitrogen at a temperature of TN = -196 degrees C, lyofilized, and examined by X-ray diffraction as powder samples. The compressive strength versus time was also measured in Setting samples of this calcium phosphate bone cement. The crystal entanglement morphology was examined by scanning electron microscopy. The results showed that: 1) alpha-TCP reacted to a calcium-deficient hydroxyapatite (CDHA), Ca9(HPO4)(PO4)5O H, whereas DCP did not react significantly; 2) the Reaction was nearly finished within 32 h, during which both the Reaction percentage and the compressive strength increased versus time, with a strong correlation between them; and 3) the calcium phosphate bone cement showed in general a structure of groups of interconnected large plates distributed among agglomerations of small crystal plates arranged in very dense packings.
Roger Thull - One of the best experts on this subject based on the ideXlab platform.
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amorphous α tricalcium phosphate preparation and aqueous Setting Reaction
Journal of the American Ceramic Society, 2004Co-Authors: Uwe Gbureck, Jake E. Barralet, Lavinia Radu, Hans Georg Klinger, Roger ThullAbstract:The mechanical and Setting properties of calcium phosphate cements are considerably determined by the pretreatment of the constituents. In this report we show for the first time that prolonged high-energy ball milling of α-tricalcium phosphate (α-TCP) led to mechanically induced phase transformation from the crystalline to the amorphous state. The amorphous material demonstrated a high reactivity such that the time for substantially complete conversion of α-TCP to calcium-deficient hydroxyapatite in 2.5% Na2HPO4 solution decreased from about 20 h (1 h of grinding in ethanol, 85% relative crystallinity) to 4–6 h for a material with a crystallinity of 8% (24 h of grinding). This reactivity could be attributed to an increased thermodynamic and kinetic solubility of the ground materials. Mechanically activated α-TCP cements were produced with compressive strengths of up to 80 MPa and Setting times of 5–16 min. The effect of reactant preparation and cement mixing parameters on the physical and chemical properties of mechanically activated α-TCP cement was investigated. By comparing cements of similar porosity and degree of conversion it was demonstrated that apatite specific surface area has a strong influence on cement mechanical performance, which highlights the importance of this previously overlooked parameter in improving strength.
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Amorphous α‐Tricalcium Phosphate: Preparation and Aqueous Setting Reaction
Journal of the American Ceramic Society, 2004Co-Authors: Uwe Gbureck, Jake E. Barralet, Lavinia Radu, Hans Georg Klinger, Roger ThullAbstract:The mechanical and Setting properties of calcium phosphate cements are considerably determined by the pretreatment of the constituents. In this report we show for the first time that prolonged high-energy ball milling of α-tricalcium phosphate (α-TCP) led to mechanically induced phase transformation from the crystalline to the amorphous state. The amorphous material demonstrated a high reactivity such that the time for substantially complete conversion of α-TCP to calcium-deficient hydroxyapatite in 2.5% Na2HPO4 solution decreased from about 20 h (1 h of grinding in ethanol, 85% relative crystallinity) to 4–6 h for a material with a crystallinity of 8% (24 h of grinding). This reactivity could be attributed to an increased thermodynamic and kinetic solubility of the ground materials. Mechanically activated α-TCP cements were produced with compressive strengths of up to 80 MPa and Setting times of 5–16 min. The effect of reactant preparation and cement mixing parameters on the physical and chemical properties of mechanically activated α-TCP cement was investigated. By comparing cements of similar porosity and degree of conversion it was demonstrated that apatite specific surface area has a strong influence on cement mechanical performance, which highlights the importance of this previously overlooked parameter in improving strength.
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Vibrational spectroscopic study of tetracalcium phosphate in pure polycrystalline form and as a constituent of a self-Setting bone cement
Journal of biomedical materials research, 1998Co-Authors: U. Posset, Roger Thull, E Löcklin, W KieferAbstract:Polycrystalline tetracalcium phosphate (TTCP), a material of considerable interest for human implantation due to its similarity to hydroxyapatite, was studied by means of Raman and FT-IR spectroscopy. The spectra were interpreted on the basis of group theoretical considerations. In addition, the Setting Reaction of a calcium phosphate cement (CPC) consisting of an equimolar mixture of TTCP and dicalcium phosphate (DCPA) was investigated by Raman spectroscopy. The band of the totally symmetric phosphate mode v1 of TTCP showed marked factor group splittings. The splitting components arose at coincident wave numbers in the IR and Raman spectra. This observation was in accordance with space group P2(1) (factor group C2(2), Z = 4). The characteristic splitting of v1 allowed the Setting Reaction of CPC to hydroxyapatite to be followed. According to the Raman spectroscopic results, considerable amounts of TTCP must be present at the sample surface after 24 h of Setting in an aqueous environment.
