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1
Lawson, Alison C. "Collagen-calcium phosphate composites." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300895.
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Chavda, Mehul. "Phosphate-modified calcium aluminate cements." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/15402/.
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The effect of phosphate modification on CAC hydration is poorly understood, and the investigation in this thesis focuses on the sodium phosphate modification of a commercially available calcium aluminate cement, examining the following : (i) the effect of modification upon the fresh state properties, (ii) long-term phase evolution, (iii) binding phase characterisation, and (iv) trials of aluminium encapsulation. Formulations of CAC modified by sodium polyphosphate, sodium monophosphate and mixtures of these, in varying proportions, are investigated. ATR-FTIR and solution NMR are used to examine the chain length of phosphate ions in solution prior to mixing. Immediately after mixing the fresh state properties are investigated using isothermal calorimetry, to assess the effect of average phosphate chain length on the heat of hydration and thermal behaviour of pastes during the initial curing period. The phase assemblage over the long term is examined by XRD and TGA up to a period of 180 days, elucidating trends in hydration behaviour with phosphate modification. This focuses upon assessment of the degree of conversion, identifying phosphate modifications which prolong the presence of metastable CAC hydrates for up to 180 days and also formulations that prevent any conventional phases forming at all and hence avoid conversion. Promising formulations with no conventional CAC hydrate formations are studied up to a period of 1050 days to confirm the longer-term stability of the alternate hydrates being formed. Characterisation of these samples after hydrothermal treatment showed the formation of hydroxyapatite, boehmite and a zeolite type phase. The disordered binding phase of this system is further investigated using solid-state nuclear magnetic resonance (NMR) to probe the environments of the 31P and 27Al nuclei. Results from advanced REAPDOR NMR experiments, used to assess the interactions between these nuclei, are reported and confirm the presence of a disordered C-A-P-H type binding phase. i Results from trials of aluminium encapsulation are also reported, where corrosion is assessed by hydrogen evolution evaluation using mass spectroscopy and water displacement, differential scanning calorimetry, scanning electron microscopy, and mass loss measurements. Promising formulations with phosphate modification outperformed the neat CAC encapsulants in all experiments performed, considering both powder and plate aluminium. The series of formulations with polyphosphate to cement mass ratio of 0.4 are recommended for further investigation as waste encapsulants. It was determined from the results of this study that altering the average phosphate ion chain length in solution prior to mixing can be used as a tool to tune the fresh state properties, including the heat of hydration and setting time. The kinetics of long term hydration and phase assemblage development maybe affected with the addition of sodium monophosphate, and radically altered away from conventional CAC hydration and instead the formation of an x-ray amorphous binding phase. This binding phase, optimal formulations, is shown to be stable in to a minimum of 1050 days with elevated compressive strength. NMR spectroscopy is used to positively verify the binding phase to be a calcium aluminium phosphate hydrate phase. Optimised phosphate modified CAC formulations are shown to outperform other conventionally used cementitious encapsulants, including OPC, OPC/BFS and neat CAC.
3
Åberg, Jonas. "Premixed Acidic Calcium Phosphate Cements." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-168650.
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Calcium phosphate cements are used in medicine to fill bone defects or give support to screws and plates in fracture fixation. The cements are formed via mixing a powder with water and the mixture harden through a dissolution-precipitation reaction. Today the cement mixing is performed in the operating room and consists of several complicated steps that need to be performed under sterile conditions. This renders the mixing a risk factor, potentially leading to harm for the patient e.g. unsatisfactory healing or infection. To reduce this risk, premixed cements have been developed using glycerol as mixing liquid. The premixed cement sets when it is exposed to body liquids. Therefore, premixed cement can be delivered to the operating room in prefilled syringes ready for use, thus eliminating the mixing step. The aim of this thesis is to describe differences between premixed and water-mixed cements and their advantages and drawbacks. The differences will be discussed based on results obtained from bench testing of specific cement properties as function of cement formulations as well as in vitro and in vivo studies. Several cement formulations were evaluated e.g. the influence of powder to liquid ratio (P/L), powder particle size and addition of water on key properties. The results showed that premixed cements have excellent handling properties and have mechanical properties similar to water-based cements. Both P/L and particle size can be used to control these properties. It was shown that small amounts of water improve certain cement properties while dry raw materials were important for long shelf life. To better understand the setting of premixed cements new methods for evaluating working time and setting of premixed cements were developed. In vivo studies showed that the formulations developed in this thesis are biocompatible, resorbable and show good tissue response in bone. This thesis concludes, that the premixed cements are a promising biomaterial with excellent handling properties and good biological response. The most important challenge for the premixed cements, in order to become commercially successful, is to obtain clinically relevant setting time and shelf life simultaneously. An increasing use of premixed cements in the clinics should shorten operation times and reduce infection rates to the benefit of both patients and medical staff.
4
Wetherall, Kate M. "The Structure of Amorphous Calcium Phosphate and othe phosphate materials." Thesis, University of Kent, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520863.
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Gonzales, Veronica Lourdes Escobar. "Stability of calcium phosphate arsenate compounds." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341898.
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Pele, Laetitia. "Cellular responses to calcium phosphate microparticles." Thesis, King's College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414584.
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Hsu, Yu-Hsiu. "Fabrication of porous calcium phosphate bioceramics." Thesis, University of Bath, 2005. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425267.
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Appleford, Mark Ryan. "Trabecular calcium phosphate scaffolds for bone regeneration." View the abstract Download the full-text PDF version (on campus access only), 2007. http://etd.utmem.edu/ABSTRACTS/2007-009-Appleford-index.html.
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Thesis (Ph.D)--University of Tennessee Health Science Center, 2007.Title from title page screen (viewed on October 8, 2007). Research advisor: Joo L. Ong, Ph.D. Document formatted into pages (xiii, 128 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 106-114).
9
O'Hara, Rochelle. "Injectable calcium phosphate cements for spinal repair." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.534586.
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Duffy, Hugh. "Microstructural evolution in calcium phosphate thin films." Thesis, Ulster University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.550567.
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Hydroxyapatite (HA) is an important class of biomaterial which has been extensively researched as a coating on metallic implant devices and/or as a model for the study of cells on bioactive surfaces. The composition of such coatings, when compared with the raw HA target powder, has led to them being termed as calcium phosphate (CaP) thin films with varying "HA-like" properties. The ability of the coating to deliver some or all of the properties of the sources material is limited by the unit cell composition that originates from the crystallinity of the coating during its growth. Although structural models exist for HA as a powder, the unit cell composition of CaP thin films has not yet been determined at the level necessary to understand the influences that effects from substrate topography and thermal annealing have on these properties. This work describes a detailed investigation of the evolution of the microstructure that occurs via grain growth in sputter deposited CaP thin films. The approach taken here utilises a multi-source RF magnetron sputter deposition system to create the relevant CaP surfaces and the application of advanced characterisation techniques and data analysis methodologies to investigate the structural properties. The effects of the key operational aspect of the process, most particularly the sputtering parameters and subsequent thermal processing on the extent of stress incorporation determined from crystallographic data and quantitative phase analysis have indicated that the choice of deposition parameters is the most critical consideration in terms of coating reproducibility and quality. The relationship between quality of the precursor HA (target) powder, thickness of the deposited layer and the unit cell composition of coating have all been addressed. It has been shown that the composition of the coating and its evolving microstructure are determined through preferred crystallographic orientation in the plane of lowest surface energy which limits the size and angle of curvature of the grains present in the coating. The size and shape of the grains produced influences the distribution of residual stress levels, i.e. the mechanical stal)1ity of the coating and also the concentration of the various atoms that are distributed across and within the thin film.
11
Unosson, Johanna. "Physical Properties of Acidic Calcium Phosphate Cements." Doctoral thesis, Uppsala universitet, Tillämpad materialvetenskap, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-233637.
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The gold standard for bone replacement today, autologous bone, suffers from several disadvantages, such as the increased risk of infection due to the need for two surgeries. Degradable synthetic materials with properties similar to bone, such as calcium phosphate cements, are a promising alternative. Calcium phosphate cements are suited for a limited amount of applications and improving their physical properties could extend their use into areas previously not considered possible. For example, cement with increased strength could be used as load bearing support in selected applications. The focus of this thesis is, therefore, on how the physical properties of acidic calcium phosphate cements (brushite cements) are affected by compositional variations, with the ultimate aim of making it possible to formulate brushite cements with desired properties. In this thesis a method to measure the porosity of a cement was developed. This method is advantageous over existing methods as it is easy to use, requiring no advanced equipment. A model estimating the porosity of the hardened cement from the initial chemical composition was further formulated and the accuracy affirmed. Utilization of this model allows the porosity to be optimized by calculations rather than extensive laboratory work. The effect on strength and porosity of several compositional variations were also assessed and it was found that the optimal composition to achieve a high strength was: monocalcium phosphate particles in sizes <75µm, 10 mol% excess of beta-tricalcium phosphate, 1 wt% disodium dihydrogen pyrophosphate, and 0.5 M citric acid in a liquid-to-powder ratio of 0.22 ml/g. This composition gave the highest compressive strength historically measured for this type of cement, i.e., 74.4 (±10.7) MPa. Although such a high strength may not be necessary for all applications, it allows for the use of brushite cements in new applications. Furthermore, a high strength of the bulk allows for alterations to the cement that cause a decrease in strength. One application is fast degrading materials, allowing rapid bone ingrowth. A fast degradation is obtained with a high macroporosity, which would reduce strength. The high strength composition was therefore utilized to achieve brushite cement with a high macroporosity.
12
Linton, Kathryn Mary. "Calcium phosphate morphology in bone and bacteria." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.445383.
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Stefanova, Helena Ivanova. "Calcium and phosphate transport in sarcoplasmic reticulum." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303376.
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LeÌveÌ‚que, Ingrid. "Inorganic-organic processes in calcium phosphate systems." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396645.
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Christie, Christopher Robert. "Calcium/Phosphate Regulation: A Control Engineering Approach." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/54014.
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Calcium (Ca) homeostasis is the maintenance of a stable plasma Ca concentration in the human body in the presence of Ca variability in the physiological environment (e.g. by ingestion and/or excretion). For normal physiological function, the total plasma Ca concentration must be maintained within a very narrow range (2.2-2.4mM). Meeting such stringent requirements is the task of a regulatory system that employs parathyroid hormone (PTH) and calcitriol (CTL) to regulate Ca flux between the plasma and the kidneys, intestines and bones. On the other hand, plasma phosphate control is less tightly, but simultaneously, regulated via the same hormonal actions. Chronic imbalances in plasma Ca levels are associated with disorders of the regulatory organs, which cause abnormal hormonal secretion and activity. These changes in hormonal activity may lead to long-term problems, such as, osteoporosis (increased loss of bone mineral density), which arises from primary hyperparathyroidism (PHPT) – hyper secretion of PTH.
Existing in silico models of Ca homeostasis in humans are often cast in the form of a single monolithic system of differential equations and are not easily amenable to the sort of tractable quantitative analysis from which one can acquire useful fundamental insight. In this research, the regulatory systems of plasma Ca and plasma phosphate are represented as an engineering control system where the physiological sub-processes are mapped onto corresponding block components (sensor, controller, actuator and process) and underlying mechanisms are represented by differential equations. Following validation of the overall model, Ca-related pathologies are successfully simulated through induced defects in the control system components.
A systematic approach is used to differentiate PHPT from other diseases with similar pathophysiologies based on the unique hormone/ion responses to short-term Ca disturbance in each pathology model. Additionally, based on the changes in intrinsic parameters associated with PTG behavior, the extent of PHPT progression can be predicted and the enlarged gland size estimated a priori.
Finally, process systems engineering methods are used to explore therapeutic intervention in two Ca-related pathologies: Primary (PHPT) and Secondary (SHPT) Hyperparathyroidism. Through parametric sensitivity analysis and parameter space exploration, the calcium-sensing receptor (sensor) is identified as a target site in both diseases and the extent of potential improvement is determined across the spectrum of severity of PHPT. The findings are validated against existing drug therapy, leading to a method of predicting drug dosage for a given stage of PHPT. Model Predictive Control is used in drug therapy in SHPT to customize the drug dosage for individual patients given the desired PTH outcome, and drug administration constraints.Ph. D.
16
Sukhodub, L. B., A. I. Kulak, Наталія Миколаївна Іншина, Наталия Николаевна Иншина, Nataliia Mykolaivna Inshyna, V. N. Kuznetsov, A. S. Stanislavov, Леонід Федорович Суходуб, Леонид Федорович Суходуб, and Leonid Fedorovych Sukhodub. "Biphasic Calcium Phosphate Composite for Biomedical Applications." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35448.
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The paper describes the preparation of the biphasic (hydroxyapatite (HA) and tricalcium phosphate
(TCP)) nanostructured calcium phosphate composite. The product was chemically synthesized from the solution
which contained calcium acetate Са(СН3СОО)2 (0,167 mМ), sodium dihydrogen phosphate NaH2PO4
(0,1 mМ), sodium hydrocarbonate NaHCO3 (0,02 mM). The calcium phosphate composite was formed at
pH=11 with and without the addition of carbonate ions. The samples were analyzed using X-Ray diffraction
after the heat treatment at 900C for 1 h. The derived material contained HA and TCP phases with
their contents change depending on the concentration of the carbonate ions in the solution. The mean crystallite
size of the HA phase in (121) plane is 12 – 14 nm. Further studies will be directed to the using of the
derived composite for the biomedical applications.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35448
17
Gohmann, Andrew Kaden. "Calcium phosphate nucleation induced by electrochemical methods." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1627572348324976.
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Piccinini, Marzio. "Porous calcium phosphate granules for biomedical applications." Doctoral thesis, Università degli studi di Trento, 2012. https://hdl.handle.net/11572/368075.
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The repair or replacement of damaged or diseased hard tissue is a biomedical field that has been the subject of more and more interest in many areas of research and especially in the development of new biomaterials. The rise in the average age of the world population, increasing osteoporosis treatments and the spread of cancer and genetic bone diseases, has brought about the need to find solutions for patient care. To achieve this target/objective, biomaterials must simulate the body environment as much as possible and favour tissue repair by integrating them into the host site.
Calcium phosphates are used as medical implants because they have a chemical composition similar to the mineral of human bones, i.e. apatite. For this reason they are biocompatible and they can interact in a bioactive way with bone tissue.
In the present work a specific form of bone graft, in the form of calcium phosphate granules, has been developed by using the droplet extrusion technique. The granules were characterized chemically and physically, with specific attention to in vivo and in vitro analyses. The proposed method has allowed us to obtain spherical granules in very narrow micrometric size distribution (300-1200 μm) without the use of solvents or oils thus avoiding time consuming washing processes. Granules were produced with several controlled mineralogical compositions including: pure Hydroxyapatite (HA) and β-Tricalcium Phosphate (βTCP), mixtures of HA/βTCP and Hydroxyapatite/Tetracalcium phosphate (HA/TTCP), and compositions doped with zinc (for antibacterial purposes) and strontium (for anti-osteoporosis purposes). Of several interesting features, the produced granules show high interconnected microporosity (0.1-10 μm) and surface roughness, properties necessary for osteoconductivity.
The solubility behavior of granules was studied and demonstrated that the morphology and microporosity are more important in dissolution processes than chemical or mineralogical composition. Products were tested in simulated body fluid (SBF), and among the different compositions, HA/TTCP has been found to be bioactive during in vitro studies. In fact an intense precipitation of a carbonated layer of apatite was observed, associated with the high dissolution of a TTCP phase. All pure granules were demonstrated to not be cytotoxic. Bone implantations in different animal models (rabbits and primates) showed good performance of granules in the repairing of bone. The granules stimulated the bone growth without any inflammatory reactions. In particular, HA/TTCP granules exhibited excellent biomechanical properties by increasing the stability of neo-formed bone. These preliminary investigations were sufficient to show that the developed granules can be used for bone repair or replacement. However, more studies, especially for doped products, such as in vitro cells experiments, have to be performed to assure the biocompatibility and the effective stimulation of bone growth.
This work was performed in collaboration with Eurocoating S.p.A. (Trento, Italy), a company expert in biomedical coatings for prostheses and implants, and it is a part of “CaP project†co-sponsored by Provincia Autonoma di Trento (Italy).
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Piccinini, Marzio. "Porous calcium phosphate granules for biomedical applications." Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/794/1/PhD%2BThesis_Piccinini_Definitiva_Aprile%2B2012.pdf.
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The repair or replacement of damaged or diseased hard tissue is a biomedical field that has been the subject of more and more interest in many areas of research and especially in the development of new biomaterials. The rise in the average age of the world population, increasing osteoporosis treatments and the spread of cancer and genetic bone diseases, has brought about the need to find solutions for patient care. To achieve this target/objective, biomaterials must simulate the body environment as much as possible and favour tissue repair by integrating them into the host site.
Calcium phosphates are used as medical implants because they have a chemical composition similar to the mineral of human bones, i.e. apatite. For this reason they are biocompatible and they can interact in a bioactive way with bone tissue.
In the present work a specific form of bone graft, in the form of calcium phosphate granules, has been developed by using the droplet extrusion technique. The granules were characterized chemically and physically, with specific attention to in vivo and in vitro analyses. The proposed method has allowed us to obtain spherical granules in very narrow micrometric size distribution (300-1200 μm) without the use of solvents or oils thus avoiding time consuming washing processes. Granules were produced with several controlled mineralogical compositions including: pure Hydroxyapatite (HA) and β-Tricalcium Phosphate (βTCP), mixtures of HA/βTCP and Hydroxyapatite/Tetracalcium phosphate (HA/TTCP), and compositions doped with zinc (for antibacterial purposes) and strontium (for anti-osteoporosis purposes). Of several interesting features, the produced granules show high interconnected microporosity (0.1-10 μm) and surface roughness, properties necessary for osteoconductivity.
The solubility behavior of granules was studied and demonstrated that the morphology and microporosity are more important in dissolution processes than chemical or mineralogical composition. Products were tested in simulated body fluid (SBF), and among the different compositions, HA/TTCP has been found to be bioactive during in vitro studies. In fact an intense precipitation of a carbonated layer of apatite was observed, associated with the high dissolution of a TTCP phase. All pure granules were demonstrated to not be cytotoxic. Bone implantations in different animal models (rabbits and primates) showed good performance of granules in the repairing of bone. The granules stimulated the bone growth without any inflammatory reactions. In particular, HA/TTCP granules exhibited excellent biomechanical properties by increasing the stability of neo-formed bone. These preliminary investigations were sufficient to show that the developed granules can be used for bone repair or replacement. However, more studies, especially for doped products, such as in vitro cells experiments, have to be performed to assure the biocompatibility and the effective stimulation of bone growth.
This work was performed in collaboration with Eurocoating S.p.A. (Trento, Italy), a company expert in biomedical coatings for prostheses and implants, and it is a part of “CaP project” co-sponsored by Provincia Autonoma di Trento (Italy).
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Raynaud, Sylvie. "Synthèse, frittage et propriétés mécaniques de phosphates de calcium dans le système hydroxyapatite - phosphate tricalcique." Limoges, 1999. http://www.theses.fr/1999LIMO0035.
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Des phosphates de calcium de rapport molaire ca/p compris entre 3/2 et 10/6 ont ete synthetises par precipitation en milieu aqueux. Les poudres sont monophasees de structure apatitique mais de stoechiometrie variable en calcium ca 1 0 x@ x(hpo 4) x(po 4) 6 x(oh) 2 x@ x (@ lacune, 0 x 1). Le rapport ca/p varie avec la temperature de synthese, il est maitrise par le controle precis de cette temperature. La calcination entre 400\c et 700\c fait diminuer la surface specifique des poudres sans densification par coalescence des particules. L'accroissement de la concentration en lacunes dans la structure augmente la vitesse de reduction d'aire. La phase apatitique se decompose a 700\c en hydroxyapatite hap et phosphate tricalcique tcp stoechiometriques. A la meme temperature, le frittage debute. Des composites biphases homogenes hydroxyapatite-phosphate tricalcique ont ete developpes par decomposition in situ de ces apatites et densifies en frittage sous charge. L'augmentation de la proportion de tcp (diminution du ca/p de la poudre) ralentit la densification. Les ceramiques elaborees au dessus de 1150\c sont particulierement fragiles avec une resistance a la rupture et une tenacite mediocres. Au cours du refroidissement, la variation de volume produite par la transformation allotropique / du tcp a 1150\c induit des contraintes residuelles nefastes aux proprietes mecaniques. Pour les materiaux densifies en dessous de 1150\c le tcp en proportion minoritaire renforce la matrice hap. La resistance atteint le double de celle de l'hap pour un composite contenant 10% en masse de tcp (ca/p = 1,65). De faibles variations de composition entrainent une chute significative des proprietes. Le rapport ca/p des poudres doit etre connu et maitrise avec precision. L'analyse quantitative par diffraction des rayons x est la methode la plus precise pour determiner ce parametre. L'incertitude relative mesuree sur le rapport ca/p n'excede pas 0,4% alors qu'elle atteint 2,5% en analyse chimique.
21
Latifzadeh, Lida 1956. "Raman spectroscopic studies of calcium-phosphate, aluminum metaphosphate-sodium fluoride and calcium metaphosphate-calcium fluoride glasses." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/278549.
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The role of modifier on the molecular structure of Ca-phosphate, sodium fluorophosphate and sodium aluminophosphate glasses have been investigated by Raman spectroscopy. Ca-phosphate glasses for this study have the molar ratio of CaO/P₂O₅ from 1.00 to 1.50. Curve fitting procedures have been used to resolve the overlapped peaks for accurate interpretation. Amorphous species with varying chain lengths and two crystalline phases of γ- and α-Ca₂P₂O₇ have been identified. Sodium fluorophosphate glasses have been prepared from the reaction between Al(PO₃)₃ and NaF. The molar ratio of Na/P is varied from 0.900 to 2.00 and the F/P ratio is from 0.510 to 1.61. By studying the vibrational frequency shifts, species with varying phosphorus and fluorine contents and aluminophosphate compounds have been identified.
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Walsh, Pamela Judith. "Natural calcium phosphate ceramics for tissue engineering application." Thesis, Queen's University Belfast, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486236.
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There is a great need for new bone graft materials. Bone related problems have increased considerably over the last few decades, owing to an ageing populate and the associated prevalence of bone disease. The traditional method of grafting to bridge bone defects are still widely used, despite a wide selection of new synthetic alternatives materials becoming available. These tend to lack the physical properties, such as porosity, interconnective and mechanical strength required for bone repair. Coral derived CaP ceramics have shown good potential, as substitute materials, offering the desirable physiochemical characteristics required for bone repair. This study investigated the development of a bioceramic from marine origins for use in bone tissue applications. Algae species were specifically selected to take account of their fast growth rate and aquaculture potential, which would minimise the environmental impact of harvesting. The conversion of alga was achieved through a novel technique, involving well controlled thermal processing followed by low pressure temperature hydrothermal synthesis technique. Using this technique, the original skeletal morphology of the alga was retained throughout processing. The resultant material was found to be a tri-phasic ceramic, with a > 90% composition of HA. Calcite and 13-TCP were the other two phases identified in the material. Cell studies confirmed the material to have good biocompatibility. A preliminary scaffold fabrication study incorporated the CaP material into a polymeric scaffold. The study found that the CaP material was robust and capable of withstanding rigorous processing. The work presented in this thesis indicates that this novel process is capable of synthesising a reproducible CaP material, which possesses suitable physiochemical properties for use in bone tissue engineering applications.
23
Gong, Tianxing. "Calcium phosphate silicate cement for risedronate drug delivery." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51550.
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The effectiveness of bone cements in treating bone fracture is impaired by osteoporosis, which not only delays the osseointegration but also compromises the stability of implants. As a result, further fractures are not unusual after bone cement implantation in osteoporotic patients. This dissertation reports the investigation of the novel calcium phosphate silicate cement (CPSC) as a possible drug delivery system (DDS) for risedronate (RA) to treat osteoporosis and to restore bone fracture. Risedronate belongs to the family of bisphosphonate and, as the 3rd generation of bisphosphonate, can effectively suppress osteoclast activities and treat osteoporosis. In this work, the CPSC material properties were characterized as a function of RA content. High performance liquid chromatography was used to detect RA release profiles from cements and the Higuchi’s Law was employed to explain its release mechanisms. In vitro biocompatibility of RA-added CPSC (CPSC-R) was evaluated by MTT assays, flow cytometry, and real-time polymerase chain reaction. In the tibia implantation model from osteoporotic rabbits, biomarkers, X-rays, computed tomography, histology and PCR arrays were used to evaluate CPSC-R in vivo performance.
It has been found that RA greatly affected CPSC setting time and compressive strength in a concentration-dependent manner. It was also found that RA disrupted CPSC hydration and delayed calcium silicate hydrate gel formation. RA was progressively adsorbed onto the unreacted calcium silicate and formed calcium-RA complexes. RA release kinetics from cement was controlled by the implant degradation and was in a good agreement with the theoretical calculations. CPSC-R was biocompatible and improved osteoblast proliferation and differentiation. Biomarker studies showed that CPSC-R significantly reduced osteoclast activities as compared to the sham control (p < 0.05). The radiographic and histological examination demonstrated that CPSC-R improved osseointegration and bone formation, as compared to RA-free CPSC control group. Gene array studies indicated that CPSC-R implants could significantly up-regulate osteogenesis-related gene expressions as compared to the control groups.
In conclusion, this study indicates that CPSC is potentially a good Drug Delivery System of RA. The anti-osteoporotic effectiveness of this system could be beneficial in bone fracture treatments for patients who are suffering from osteoporosis.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
24
Langstaff, Sarah Dorthea. "Calcium phosphate ceramics capable of supporting osteoclastic resorption." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0005/NQ42953.pdf.
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Barrère, Florence. "Biomimetic calcium phosphate coatings: physicochemistry and biological activity." Enschede : University of Twente [Host], 2002. http://doc.utwente.nl/58711.
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Shi, Jiawanjun. "Properties of alkaline-resistant calcium-iron-phosphate glasses." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/Shi_09007dcc8043f8f6.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 25, 2008) Includes bibliographical references (p. 52-54).
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梁永鏗 and Wing-hang Vitus Leung. "The calcium phosphate system in saliva-like media." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1989. http://hub.hku.hk/bib/B30425827.
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Van, der Houwen Jacqueline A. M. "Chemical principles of calcium phosphate dissolution and precipitation." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272517.
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Mancardi, Giulia. "Computational study of the nucleation of calcium phosphate." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10050587/.
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Hydroxyapatite (HA), the main mineral phase of mammalian tooth enamel and bone, originates in body fluids from amorphous calcium phosphate (ACP). The early stage of ACP formation from solution is the object of the investigations presented in this thesis. I have first performed ab initio molecular dynamics simulations to shed light on the structure and stability of the calcium phosphate (CaP) prenucleation clusters, [Ca(HPO4)3]4 – , in aqueous solution. The calcium is seven coordinated by two water molecules, two bidentate phosphates and one monodentate phosphate. Free energy profiles obtained using umbrella sampling simulations show that the complex with a Ca-to-P ratio of 1:3 is the most energetically favoured, and thermodynamically more stable than the free ions. In order to be able to study a larger system, I have employed shell-model molecular dynamics simulations to investigated the aggregation and clustering of calcium and phosphate ions in water. ACP presents short-range order in the form of small domains with size of 0.9 nm and chemical formula Ca9(PO4)6, known as Posner’s clusters. Calcium phosphate aggregates form in solution with compositions and Ca coordination that are similar to those found in Posner’s cluster, but the stoichiometry of these species is dependent on the ionic composition of the solution: calcium-deficient clusters in solutions with low Ca/P ratio; cluster containing protonated phosphate groups in neutral solutions; sodium ions partially substituting calcium in solutions containing a mixture of sodium and calcium ions. These Posner-like clusters can be connected by phosphate groups, which act as a bridge between their central calcium ions. The simulations of the aggregation in solution of calcium phosphate clusters are an unbiased and unequivocal validation of Posner’s model and reveal for the first time the structure and composition of the species that form during the early stages of ACP nucleation at a scale still inaccessible to experiment. Lastly, I have investigated the heterogeneous nucleation of CaP on a titanium implant. Titanium is commonly employed in orthopaedic and dental surgery due to its good mechanical properties. In order to promote the integration of the metallic implant with the biological tissues, titanium is passivated by a thin layer of oxide and covered by a bioactive material, normally HA; HA can originate on the oxide during a process called biomimetic deposition which consists in soaking the implant in simulated body fluids, that are supersaturated with respect to HA. This method allows to efficiently cover implants with complex shapes and to create a porous coating similar to the bone tissue. Here, I have used molecular dynamics and interatomic potentials to study the deposition of calcium and phosphate species on the titanium dioxide anatase. Different force fields developed for calcium phosphate, titanium dioxide and water were combined and the new parameters were benchmarked against DFT data. Calcium phosphate interaction with the (101) and (100) surfaces of anatase was successfully investigated and the force field here proposed can be used to study the nucleation of calcium phosphate on other titanium dioxide polymorphs and on common surface defects.
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Samizadeh, S. "Bone formation on calcium phosphate bone substitute materials." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/19891/.
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A large number of bone substitute materials are available; for which some authors claim osteoconductivity and some osteoinductivity. In order to rank these materials an in vivo analysis was carried out. These materials were chosen based on their availability and claimed mode of action. Silicon substituted Hydroxyapatite (SiHA), Hydroxyapatite (HA), Resorbable Calcium Phosphate Silicon, Skelite [siliconstabilized tricalcium phosphate-based bone substitute], Pro Osteon 500R [coralline HA], BiIonic [Yttrium stabilized SiHA] and two non-calcium phosphate, Dimeneralised Bone Matrix (DBM) based biomaterials: Accell Connexus DBM putty and Grafton crunch DBM were implanted in sheep femoral condyle defects for 6 weeks. Implanted calcium phosphate (CaP) based biomaterials demonstrated superior bone formation in comparison with the DBM samples. Silicon within CaPs increased the rate of bone formation in vivo. Silicon substituted HA showed increased proliferation rate (P<0.05) of human marrow stromal cells compared to pure HA in vitro. Expression of osteoblastic marker genes RUNX2, Osterix and Osteopontin within the hMSCs indicated the differentiation of preosteoblasts into osteoblasts, and osteogenic development on both HA and SiHA. Expression of osteocalcin and bone sialoprotein genes on HA and SiHA samples indicated the activation of mineralisation process. Differentiation of hMSCs into osteoblasts in vitro suggested a role in promotion of osteoinduction by both HA and SiHA. Implantation of porous SiHA and HA in paraspinous muscle of sheep, exhibited new bone formation through osteoinduction. SiHA indicated significantly higher new bone formation (P<0.01) compared to HA. SiHA and HA biomaterials with higher strut porosity (30%) indicated greater bone formation (P<0.05). In conclusion, CaP based biomaterials demonstrate superior bone formation in comparison with DBM biomaterials. Silicon substitution within HA enhances the cellular activity of hMSCs. Osteoinduction was greatest on SiHA with higher strut porosity. This result is believed to be due to a combination of the effect of interconnected porosity and chemical composition of the bone substitute.
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Al-Lami, Mohammed Sabar. "Amorphous calcium phosphate nanocomplexes in dental film formulations." Thesis, University of Strathclyde, 2012. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23885.
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The present thesis concerns the exploration of novel amorphous calcium phosphate nanocomplexes stabilised by food grade additives. The concept is to generate a formulation to prevent dental caries through enamel remineralisation, supplementing the calcium and phosphate concentrations by delivery from an adhesive dental film dosage form. A formulation containing calcium chloride, dibasic sodium phosphate and stabiliser in hydrochloric acid solution at a pH of 5 was complexed by pH adjustment to 7 in the presence of fractioned hydrolysed casein or negatively charged peptides. This allowed the formation of stabilised amorphous calcium phosphate nanocomplexes. An alternative method in which carboxymethyl cellulose with short chain length with measured molecular weight and degree of substitution, produced by acid hydrolysis, was similarly able to stabilise the amorphous calcium phosphate nanocomplex. The prepared amorphous calcium phosphate nanocomplexes were suitable for formulation in to dental film dosage forms. The prepared nanocomplexes were formulated into dental films based on hydroxy propyl methyl cellulose (HPMC) of various grades which formed hydrogels with good adhesive properties. The physical properties of the prepared films were characterised by texture analysis, tensile strength and structure and the calcium release was measured using film strips in a specially designed dissolution cell. The formulated dental films containing a mixture of 2% w/v E10M and 1% w/v F4M hydroxy propyl methylcellulose, loaded with 2 % w/v 4 hours acidic hydrolysed carboxy methylcellulose and hydrolysed casein, had a suitable release of calcium. The release pattern of the calcium was characterised using different diffusion/erosion models and was best described by a Higuchi mode with Fickian, non-Fickian and super case II transport kinetics depending on the type of ACP and the grade of HPMC used. The effect of a biofilm generated on the tooth surface to make the substrate more hydrophobic was examined. The adhesion of 15% (w/v) HPMC-E10M hydrogel to enamel slabs was studied, and was found to be highly variable. The effect of ACP on the culture of the biofilm using confocal laser scanning microscopy was investigated and a substantial inhibitory effect was obtained with 8% w/v ACP. The remineralisation effect of preparations containing 2% w/v NGP-ACP, HC-ACP and acid hydrolysed CMC-ACP loaded into films formulated with a mixture of 2% w/v E10M and 1% w/v F4M hydroxy propyl methylcellulose was investigated. The method employed used scanning electron probe microanalysis to determine the elemental deposition of the calcium and phosphorus up to a depth of 400μm in enamel samples. Both 2% w/v 4h ahCMC-ACP and 2% w/v HC-ACP containing dental films showed an uptake of calcium and phosphate with uniform and constant deposition of the elements to a depth of 400μm into the enamel samples.
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Суходуб, Леонід Федорович, Леонид Федорович Суходуб, Leonid Fedorovych Sukhodub, Вячеслав Іванович Перекрестов, Вячеслав Иванович Перекрестов, Viacheslav Ivanovych Perekrestov, Ганна Сергіївна Корнющенко, et al. "Metal and Calcium-Phosphate Nanoparticles for Biomedical Applications." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34813.
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Nanoparticle research is currently an area of intense scientific research due to variety of potential applications
in optics, electronics, biotechnology, health care, biomedical, chemical, and pharmaceutical
fields. The physical sizes of these materials create a strong possibility for their interaction with biological
systems. Biological systems themselves contain various components that have nanometer dimensions (proteins,
nucleic acids, membranes), therefore nanopaticles can be useful both for in vivo and in vitro biological
researches and applications. Among the metallic nanoparticles (NPs), the most important materials in
nanomedicine are gold, silver, copper, iron, cobalt, nickel, platinum, magnesium, palladium and rhodium.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34813
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DAVID, PIERRE-CHRISTOPHE. "Utilisation du tri-calcium phosphate en chirurgie orthopedique." Aix-Marseille 2, 1994. http://www.theses.fr/1994AIX20035.
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Redmond, Jean Patricia. "Ethnic differences in calcium, phosphate and bone metabolism." Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708405.
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Leung, Wing-hang Vitus. "The calcium phosphate system in saliva-like media /." [Hong Kong] : University of Hong Kong, 1989. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12555769.
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Lee, Wing Hin. "Modulating protein adsorption of calcium phosphate-based biomaterials." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10267.
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The focus in this thesis was to examine the factors that influence protein adsorption onto hydroxyapatite (HA) surfaces and utilize these factors to improve HA properties to be used as a carrier for the delivery of bone growth factors in body. The ultimate aim was to prepare HA particles equipped with a high loading capacity for bone morphogenetic protein 2 (BMP-2), while simultaneously provide a sustained release of BMP-2 in the body. used widely as a bone substitute. The experimental approach focused on the methods used to selectively modify the surface charge of HA via immobilization of charged biological molecules such as amino acids and citric acid. The protein adsorption studies were investigated using two model proteins: basic protein (lysozyme) and acidic protein (BSA). In addition, manipulation of microenvironments (i.e. ionic strength, pH, temperature) was employed to achieve higher protein loading capacity and simultaneously to promote osteoblast attachment and differentiation. The understanding of the factors involved in protein adsorption could provide us with a better understating of strategies to manipulate protein adsorption onto HA, enabling us to further develop a superior HA biomaterial as a carrier for delivering therapeutic proteins (e.g., growth factors) in the body.
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Bennani-Ziatni, Mounia. "Etude du système phosphate de calcium, carbonate de calcium en milieu eau-éthanol." Toulouse, INPT, 1986. http://www.theses.fr/1986INPT004G.
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Composition des phases coprecipitees pour differents rapports carbonate-phosphate. Il existe des domaines monophases, amorphes et polyphases. Stabilite thermique des apatites carbonatees et des calcites phosphatees
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Bennani-Ziatni, Mounia. "Etude du système phosphate de calcium carbonate de calcium en milieu eau-éthanol." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375959373.
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Debroise, Théau. "Calcium Oxalate and Calcium Phosphate Biominerals : Formation and Stability studied by Molecular Dynamics." Electronic Thesis or Diss., Sorbonne université, 2019. https://theses.hal.science/tel-04059925.
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Cette thèse s’articule autour de la thématique de la biominéralisation, le processus par lequel les êtres vivants parviennent à orienter la précipitation de minéraux présents dans leur environnement pour confectionner des matériaux utiles à la survie de l’espèce considérée. La biominéralisation est un phénomène extrêmement complexe mettant en jeu des régulations génétiques et l’implication de protéines permettant d’enclencher la minéralisation, à des localisations bien précises. Il arrive cependant que celle-ci échappe au contrôle de l’organisme vivant conduisant alors à diverses pathologies. C’est le cas par exemple, quand des calcifications appelées calculs rénaux, se forment à l’intérieur des reins. A partir d’une certaine taille, un calcul rénal devient pathologique et nécessite une prise en charge hospitalière. La pathologie est communément appelée lithiase urinaire. Il est établi que les oxalates de calcium, et plus particulièrement les phases monohydratée (Calcium Oxalate Monohydrate, COM ou whewellite) et dihydratée (Calcium Oxalate Dihydrate, COD ou weddellite), composent la majorité des calculs rénaux. L’environnement, et tout particulièrement l’alimentation, est un facteur clé influençant la formation et la composition des calculs rénaux. Actuellement, les traitements consistent principalement à une injection d’antalgiques et à l’éjection du calcul par les voies naturelles. Si nécessaire, une intervention chirurgicale est mise en œuvre. Les médecins sont à la recherche de médicaments/traitements potentiellement capables de prévenir la formation des calculs rénaux. Dans cette thèse, nous avons choisi d’aborder cette problématique par le biais de la chimie théorique et plus particulièrement de la dynamique moléculaire, une méthode prédictive d’importance permettant d’étudier le comportement d’un modèle atomique au cours du tempsThis thesis is about biomineralisation, the process by which living beings manage to direct the precipitation of minerals present in their environment to make materials useful for the survival of the species in question. Biomineralization is an extremely complex phenomenon involving genetic regulation and the involvement of proteins to trigger mineralization at specific locations. It happens however that it escapes the control of the living organism, then leading to various pathologies. This is the case, for example, when calcifications called kidney stones are formed inside the kidneys. From a certain size, a renal calculus becomes pathological and requires hospital care. The pathology is commonly called urolithiasis. It is established that calcium oxalates, and more particularly the monohydrate (Calcium Oxalate Monohydrate, COM or whewellite) and dihydrate (Calcium Oxalate Dihydrate, COD or Weddellite) phases, make up the majority of kidney stones. The environment, and especially food, is a key factor influencing the formation and composition of kidney stones. Currently, the treatments consist mainly of an injection of analgesics and the ejection of the calculation by the natural channels. If necessary, surgery is performed. Doctors are looking for drugs / treatments that can potentially prevent the formation of kidney stones
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Le, Grill Sylvain. "Composite chitosane-phosphate de calcium : synthèse par atomisation séchage et caractérisation structurale." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30023/document.
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Ce mémoire porte sur l'élaboration et la caractérisation d'un matériau composite chitosane/phosphate de calcium destiné à une utilisation dans le domaine de la substitution osseuse. Le procédé d'atomisation-séchage a été choisi pour élaborer ce composite sous forme d'une poudre susceptible d'être transformée en revêtement ou objet 3D. Une étude préliminaire a permis d'appréhender les mécanismes de synthèse du phosphate de calcium, la phase minérale, par atomisation-séchage. Une suspension de particules d'hydroxyapatite stœchiométrique ou d'apatite biomimétique dispersées dans une solution acide mène systématiquement à l'apparition d'une phase amorphe. La proportion de cette phase amorphe dans la poudre atomisée-séchée est dépendante de la taille et de la cristallinité du matériau d'origine. L'atomisation séchage d'une solution acide contenant les ions précurseurs de calcium et phosphate mène à la formation d'une phase principalement amorphe. Cette poudre a pu être décrite à différentes échelles : à une échelle de l'ordre du nanomètre apparaissent des clusters, à une échelle de l'ordre de la centaine de nanomètres des agrégats sphériques de clusters organisés en chapelet tortueux et imbriqués sont identifiés et enfin à une échelle micrométrique des agglomérats de nanoparticules ont été mises en évidence. Le phosphate de calcium ainsi synthétisé possède un rapport molaire Ca/P proche de 1.3. Au-delà de ce rapport dans la solution à atomiser, de l'acétate de calcium (utilisé ici comme précurseur) recristallise dans la poudre. Pour élaborer la poudre composite, le polymère a été solubilisé et ajouté d'abord dans une suspension acide d'hydroxyapatite avant atomisation. Cette première stratégie mène à la formation d'un composite qui présente de fortes inhomogénéités de répartition des phases organiques et minérales. Pour limiter ce problème lié à la distribution de tailles de grains de la phase minérale, une seconde stratégie a été développée. Une solution de polymère contenant des précurseurs de phosphate de calcium a été préparée pour favoriser l'association à l'échelle nanométrique des deux phases. Après atomisation-séchage, un matériau composite présentant une très bonne dispersion de la phase minérale dans la matrice organique est synthétisé. La structuration de la phase minérale est modifiée par la présence du polymère. Cette modification se traduit par une diminution de la fraction volumique des clusters et, à l'échelle supérieure, la phase minérale n'est plus présente sous forme de chapelet mais en particules sphériques isolées. Par ailleurs, une interaction chimique est envisagée en raison des liaisons de type hydrogène, ioniques ou de coordinations possibles entre les deux phases. La présence du polymère inhibe également la formation de l'acétate de calcium cristallin en favorisant la formation d'un sel d'acétate de chitosane. Deux techniques de mises en forme ont été étudiées (MAPLE, pour l'élaboration de revêtements minces et l'impression 3D de pâte pour l'obtention d'objet massif) et ont permis de mettre en avant le potentiel de transformation de la poudre préparée par atomisation séchage. Les études biologiques faites sur le revêtement ont de plus permis de démontrer les propriétés antibactériennes du matériau utiliséThis thesis deals with the development and characterization of a chitosan/calcium phosphate composite material for use in the field of bone substitution. The spray-drying method was chosen to develop this composite in the form of a powder that could be transformed into a coating or 3D object. A preliminary study made it possible to understand the mechanisms of synthesis of calcium phosphate, the mineral phase, by spray-drying. A suspension of stoichiometric hydroxyapatite particles or biomimetic apatite dispersed in an acidic solution systematically leads to the appearance of an amorphous phase. The proportion of this amorphous phase in the spray-dried powder is dependent on the size and crystallinity of the original material. The spray drying of an acidic solution containing the precursor ions of calcium and phosphate leads to the formation of a mainly amorphous phase. This powder could be described at different scales: on a scale of about one nanometer appear clusters, on a scale of about one hundred nanometers spherical aggregates of clusters organized into tortuous and nested chaplets are identified and finally on a micrometric scale, agglomerates of nanoparticles were highlighted. The calcium phosphate thus synthesized has a molar ratio Ca/P close to 1.3. Beyond this ratio in the solution to be atomized, calcium acetate (used here as a precursor) recrystallizes in the powder. To develop the composite powder, the polymer was solubilized and added first into an acid suspension of hydroxyapatite before atomization. This first strategy leads to the formation of a composite that has strong in homogeneities in the distribution of organic and inorganic phases. To limit this problem related to the grain size distribution of the mineral phase, a second strategy has been developed. A polymer solution containing calcium phosphate precursors has been prepared to promote nanoscale association of the two phases. After spray-drying, a composite material having a very good dispersion of the mineral phase in the organic matrix is synthesized. The structuring of the mineral phase is modified by the presence of the polymer. This modification results in a reduction of the volume fraction of the clusters and, on the larger scale, the mineral phase is no longer present in the form of a string but in isolated spherical particles. Moreover, a chemical interaction is envisaged because of the hydrogen, ionic or possible coordination bonds between the two phases. The presence of the polymer also inhibits the formation of crystalline calcium acetate by promoting the formation of a salt of chitosan acetate. Two shaping techniques were studied (MAPLE, for the elaboration of thin coatings and the 3D printing of dough for obtaining massive objects) and made it possible to highlight the transformation potential of the prepared powder by spray drying. The biological studies made on the coating have also demonstrated the antibacterial properties of the material used
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Benaqqa, Chahid Fantozzi Gilbert. "Etude de la propagation sous critique de fissures dans les phosphates de calcium cas de l'hydroxyapatite et du phosphate tri-calcique /." Villeurbanne : Doc'INSA, 2004. http://docinsa.insa-lyon.fr/these/pont.php?id=benaqqa.
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Thèse doctorat : Génie des Matériaux : INSA LYON : 2003. Thèse doctorat : Génie des Matériaux : Ecole Mohammadia d'ingénieurs, Rabat : 2003.Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. p. 105-119.
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Destainville, Arnaud. "Etude du phosphate tricalcique : application à l'élaboration de biomatériaux céramiques macroporeux en phosphates de calcium." Limoges, 2005. https://aurore.unilim.fr/theses/nxfile/default/1461a6e6-df31-40e2-89bb-8e65a6934703/blobholder:0/2005LIMO0010.pdf.
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La synthèse par voie aqueuse du phosphate tricalcique apatitique Ca9(HPO4)(PO4)6(OH), qui conduit au TCP β anhydre Ca3(PO4)2 après calcination à une température supérieure à 700°C, a été étudiée par la méthode des plans d’expériences. Sous couvert d’un contrôle précis de la température et du pH, les conditions de stabilité permettant d’envisager la synthèse reproductible de TCP apatitique sont réunies pour une température de 30°C, un pH compris entre 6,5 et 7,0 et une durée de maturation minimale de 10 h. La validation de ce protocole a nécessité la mise en place de méthodes de caractérisation par ATD et DRX autorisant la détection à des seuils très faibles des deux phases secondaires HA et CPP β qu’est susceptible de contenir le TCP synthétisé après calcination à 1000°C. L’évolution cristallographique du TCP β en température semble se traduire par une compensation progressive des altérations structurales affectant la maille hexagonale à basse température. Le caractère renversable des processus mis en jeu ne semble assuré que sous des conditions restrictives de recuit. Les valeurs optimales de résistance à la rupture et à la propagation de fissures sont obtenues pour des compacts de TCP β pur frittés sous charge à 1100°C pendant 30 mn. Ces valeurs sont respectivement de 85 MPa et de 1,3 MPa. M1/2. Des pièces macroporeuses de TCP β et de mélange biphasé 65% HA/35% TCP β vouées à la substitution osseuse ont été élaborées par imprégnation de mousse polymérique par des suspensions de phosphates de calcium. Après une étape de broyage-mélange, les suspensions ont un comportement pseudo-plastique rhéofluidifiant pour de faibles valeurs de vitesse de cisaillement suivi d’un écoulement de type linéaire pour un cisaillement plus intense. Les pièces de TCP β présentent, après un frittage de 2 h à 1100°C, une microstructure dense exempte de microporosité pour une macroporosité totale de 74% et une résistance en compression de 2,1 MPa. Les échantillons de BCP présentent, après frittage de 1 heure à 1350°C et recuit de 48 h à 1000°C, une porosité totale de 78,5% composée de 80% de macropores et de 20% de micropores pour une valeur moyenne de résistance en compression de 0,4 MPa. Les matériaux cellulaires obtenus sont à porosité contrôlée et interconnectée : diamètres de macropores compris entre 330 et 690 µm et diamètres d’interconnexion compris entre 50 et 250 µm. Les pièces de TCP β et de BCP finalisées ont des surfaces spécifiques respectives de 0,9 m²/cm3 et de 0,7 m²/cm3The synthesis via aqueous medium of apatitic tricalcium phosphate Ca9(HPO4)(PO4)6(OH), which leads to anhydrous β TCP Ca3(PO4)2 above 700°C, was studied with the help of Doelhert experimental designs. Under an accurate control of temperature and pH, the experimental conditions allowing the reproducible synthesis of pure apatitic TCP are a temperature of 30°C, a pH between 6,5 and 7,0 and a ripening time of 10 hours. Characterization methods using ATD and DRX were required to validate the synthesis process and to control the purity of the as-synthesized powders by detection of very small quantities of secondary phases (β CPP, HA). Crystallographic changes of β TCP with temperature seems analogue to a progressive compensation of structural alterations affecting its hexagonal lattice at low temperature. Reversibility of the phenomenon involved is not insured without restrictive conditions of additional heat treatment. Flexural strength and indentation toughness of pure β TCP were measured on fully dense materials obtained by hot pressing for 30 minutes at 1100°C. Optimal values are, respectively, 85 MPa and 1,3 MPa. M1/2. Macroporous bone substitutes were prepared by immersion of polymeric foams in β TCP or biphasic mixture 65% HA/35% β TCP slurries. After milling, BCP and TCP slurries are shear thinning at low shear rate whereas they exhibit a linear rheological behaviour at high shear rates. After sintering at 1100°C for 2 hours, samples of β TCP were dense with a microstructure free from porosity for a total macroporosity of 74% and a compressive strength of 2,1 MPa. Samples of BCP exhibit, after sintering at 1350°C for 1 hour and a secondary firing step at 1000°C during 48 hours, a total porosity of 78,5% made of 80% of macropores and 20% of micropores, for a compressive strength of 0,4 MPa. Cellular materials obtained have a controlled and interconnected porosity: macropores diameters between 330 and 690 µm and interconnexion diameters between 50 and 250 µm. TCP and BCP processed parts have a specific area of, respectively, 0,9 m²/cm3 and 0,7 m²/cm3
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Benaqqa, Chahid. "Etude de la propagation sous critique de fissures dans les phosphates de calcium : cas de l'hydroxyapatite et du phosphate tri-calcique." Lyon, INSA, 2003. http://theses.insa-lyon.fr/publication/2003ISAL0069/these.pdf.
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Dans ce travail, des essais de double torsion ont été réalisés pour étudier la propagation lente de fissures dans l'hydroxyapatite (HAP, Ca10(PO4)6(OH)2), le Phosphate tricalcique (TCP, Ca3(PO4)2) et un composite HAP/b-TCP (70/30) sous forme dense. Les lois de variation de la vitesse, V, en fonction du facteur d'intensité de contrainte, KI, qui sont des lois intrinsèques de propagation de fissure pour chaque céramique, ont été obtenues dans différents environnements et conditions d'élaboration. Les courbes V-KI des trois matériaux se composent de trois stades bien distincts, dus aux mécanismes de corrosion sous contrainte par les molécules d'eau. Ces bio-céramiques semblent être très sensibles à la propagation sous-critique de fissures, qui peut se produire même pour des facteurs d'intensité de contrainte très faibles. Ceci peut être attribué aux groupes hydroxyles, favorisant l'adsorption de l'eau, à l'origine d'une forte chute de l'énergie de surface. La présence d'un seuil définissant l'intervalle de sécurité d'utilisation a été également observée. Cette étude démontre en outre que les conditions d'élaboration doivent être soigneusement contrôlées, en particulier, la température de frittage, qui a un effet significatif sur les lois V-KI. Un frittage 50ʿC au-dessus ou au-dessous de la température optimale, par exemple, peut décaler les lois de propagation vers de très faible facteurs d'intensité de contrainte. Des essais sont aussi réalisés en vu de révéler l'influence du vieillissement sur les lois V-KI.
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Lindgren, Christer. "On healing of titanium implants in biphasic calcium phosphate." Doctoral thesis, Linköpings universitet, Institutionen för klinisk och experimentell medicin, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-72938.
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Background: Previously, autogenous bone was considered the gold standard for grafting procedures in implant surgery. Today, the use of bone graft substitutes is an alternative for sinus lift procedures. Nevertheless, only a few bone substitutes are well documented and can be recommended as an alternative to autogenous bone grafts. Both deproteinized bovine bone (DBB) and tricalcium phosphate (TCP) are materials that are frequently used and well documented. During the last years a novel biphasic calcium phosphate (BCP) has been introduced to the market. Until now only a few studies have been published. Aims: Studies I, II, III and IV. The overall aim of the present thesis was to evaluate a new biphasic calcium phosphate for bone augmentation of the maxillary sinus. Deproteinized bovine bone was used as a control.Study V. The aim of this in vitro study was to evaluate the response of human osteoblast-like cells (HOB) to nano-crystalline-diamond-particle-modified (nDP-modified) and un-modified (control) deproteinized bovine bone (DBB) and biphasic calcium phosphate (BCP) scaffolds. Materials and Methods: Studies I, II, III and IV. The studies were based on 11 patients (six women, five men) with a mean age of 67 years (range; 50 to 79 years). All patients showed severe maxillary resorption with less than 5mm of residual alveolar bone in the floor of the maxillary sinus, which excluded conventional implant treatment. Twenty-two maxillary sinuses were augmented with BCP on one side and with DBB acting as a control at the contralateral side. Simultaneously with the augmentation procedure 22 microimplants were placed inside the augmented materials. After 8 months of graft healing the microimplants and a surrounding bone core were retrieved for histomorphometrical analysis (Paper I) and for energy dispersive spectroscopy (Paper II). After retrieval of the microimplants, 62 conventional implants were placed and left to heal for 8 weeks before rehabilitation with fixed prosthetic constructions. The conventional implants were evaluated clinically at baseline, after 1- and 3 years of loading (Papers III and IV). After 3 years of graft healing 18 biopsies were harvested from 9 patients for histomorphometrical analysis (Paper IV). Computerized tomography (CT) of the maxillary sinuses was performed after 3 years of graft healing to allow examination of the recipient sites. Study V. Nano-crystalline-diamond particle-modification of DBB and BCP particles was carried out through different steps of preparation including grinding and ultrasonic techniques. Scanning electron microscopy (SEM) was carried out after 24 hours and 3 days. Real time-polymerase chain reaction (PCR) was carried out after 3 days, 1 week and 2 weeks of incubation. The following osteoblast differentiation markers were analyzed: alkaline phosphatase (ALP), osteocalcin (OC), bone morphogenetic protein type 2 (BMP-2) and integrin alpha 10 (ITGA 10). Results: In paper I, the results revealed a similar degree of bone formation and bone-to-implant contact around sandblasted and acid-etched microimplants placed in sinuses augmented with BCP or DBB. No obvious signs of resorption of the BCP and DBB particles were noticed. There was a significantly higher amount of DBB particles in contact with newly formed bone compared to BCP (p=.007). In paper II, the median Ca/P ratios (atomic %), determined from >200 discreet sites within residual graft particles and adjacent bone were analysed. The difference between the median values for BCP and DBB and for BCP-augmented bone compared with DBB-augmented bone were statistical significant (p=.028 in each case). The reduction in Ca/P ratio for BCP over the healing period is consistent with the dissolution of β-TCP and reprecipitation on the surface of calcium-deficient hydroxyapatite. In paper III, the results revealed that no implant placed in residual bone was lost, one implant placed in BCP was lost after 3 months of functional loading due to infection, and one implant placed in DBB was lost only a few weeks after insertion due to lack of initial instability. The overall implant survival rate was 96.8%. Success rates for implants placed in BCP and DBB were 91.7% and 95.7% respectively. No significant differences in marginal bone loss were found around implants placed in BCP, DBB or residual bone respectively. In paper IV, it was shown that after 36 months (range; 36 to 37 months) of functional loading the overall implant survival rate was 96.8%. Success rates for implants placed in BCP, DBB and residual bone were 91.7%, 95.7% and 86.7% respectively. No significant difference was found between implants placed in BCP, DBB and residual bone. The corresponding histological evaluation after 3 years of graft healing showed BCP particles under different levels of dissolution. Dissolution was mostly observed on the edges of the BCP particles but in some cases the entire particle was dissolving. In contrast, DBB particles showed no signs of resorption. The percentage of graft particles in contact with newly formed bone was not significantly different after 3 years of healing for BCP and DBB. In paper V, cellular responses were evaluated in terms of attachment and differentiation. SEM after 24 hours and 3 days of incubation disclosed similar cell attachment and spreading for nDP-modified and non-modified DBB and BCP particles. Real-time PCR revealed significant up-regulation of mRNA expression of ALP and OC and by HOB grown on nDP-modified DBB and BCP-particles after 1 and 2 weeks compared to non-modified particles. A significant down-regulation of BMP-2 on nDP-modified DBB and a significant up-regulation of BMP-2 on DP-modified BCP was disclosed for HOB in relation to un-modified particles. Cell adhesion marker ITGA 10 showed significant down-regulation in the mRNA level for both nDP-modified groups after 2 weeks of incubation (mDP-BCP (p<.01) and nDP-DBB (p<.05) compared to the non-modified materials. Conclusion: It is concluded that BCP can be used for maxillary floor augmentation and later placement of dental implants producing equal results to those for DBB. Nevertheless, the initial HA/β-TCP ratio in BCP might not be optimized for cell adhesion, which can affect the early healing phase. Furthermore, the results indicate that BCP is not optimized for gene expression in its present form and that nDP-modified BCP enhances the osteoblast phenotype suggesting that these scaffolds are appropriate cell carriers, superior to non-modified BCP particles. Surface modification of bone substitutes is a new interesting field in bone tissue engineering (BTE). Nevertheless, it´s still unclear if the modification will have any clinical impact.
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Dai, Xiaoshu. "Calcium phosphate scaffolds from electrospun PVA/inorganic sol precursors." Worcester, Mass. : Worcester Polytechnic Institute, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-042506-161758/.
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Möller, Janina. "Porous calcium phosphate based nanovectors for growth factor release." Phd thesis, Université de Haute Alsace - Mulhouse, 2010. http://tel.archives-ouvertes.fr/tel-00685006.
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Calcium phosphates are the most frequently used ceramics for bone regeneration due to their biocompatibility and favorable resorption properties. Their performance can however be improved if they are associated to growth factors. In order to control the release of growth factors, we have inted to synthesize calcium phosphates with controlled mesoporosity. This thesis represents the first work that combines mesoporous calcium phosphates with the growth factors TGF and VEGF. To obtain hydroxyapatite with controlled mesoporosity, we propose new synthesis pathways: the hydroxyapatite is synthesized inside the porosity of silica or carbon templates by infiltration of aqueous precursor solutions. The template is eliminated by chemical etching with NaOH (silica template) or by selective oxidation (carbon template). Six ceramics have been chosen for the analysis of their protein adsorption and release properties. First, the experimental protocol is defined using the model proteins BSA and Cytochrom C. Then, the growth factors TGF and VEGF have been used. By this study, we were able to determine which samples were the most efficient in terms of protein adsorption and release.
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De, Mestral François. "Calcium phosphate glasses and glass-ceramics for medical applications." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65405.
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Michie, Emily M. "Simulation of calcium phosphate materials for radioactive waste applications." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506054.
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Zhou, Shuxin. "Synthesis and characterization of calcium phosphate silicate bio-cements." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46355.
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Calcium phosphate silicate cement (CPSC) describes a family of materials in which the powder component is composed of the mixture of hydraulic calcium silicates and calcium phosphates. CPSC was developed and characterized in this work with the broad goal to address, and possibly overcome, the disadvantages of calcium silicate and calcium phosphate cements used in medical and dental fields. The main objective of this work was to synthesize and characterize CPSC, focusing particularly on the hydration process of CPSC. The cements consisting of various amounts of triclacium silicate (C₃S) and calcium phosphate monobasic (CPM), were synthesized by the sol-gel process, followed by heat treatment at 1550ºC and planetary ball-milling. It has been determined that after mixing with water, C₃S hydrates to calcium silicate hydrates (C-S-H) and calcium hydroxide (CH); within 10 min CPM reacts with CH to form dicalcium phosphate dihydrate (DCPD), which further reacts with CH and precipitates hydroxyapatite (HAP). It is proposed that the phosphate ions incorporate into C-S-H to form another type of hydrates C-S-P-H. The morphology of the hydrates depends on the process of hydration and the composition of CPSC. At the early stages of hydration, the hydration products form “almond-shaped” particles that serve as a nucleation site for the hydrates. The hydrates take tubular shape and form bundles clustered along the radial direction of the tubes. CPM influences the hydration kinetics of C₃S by increasing the duration of the hydration acceleration period rather than increasing the hydration rate, especially for the higher content of CPM in CPSC. CPM also increases the porosity of CPSC and reduces the content of CH, thought to be the “weak link” in the set CPSC. As a compromise between the two effects, the optimal content of CPM appears to exist at about 10 wt% of CPM in CPSC. After immersion in simulated body fluid, HAP forms on the surface of CPSC indicating that CPSC is bioactive in vitro. Cytotoxicity assay and cell adhesion assay against human gingival fibroblast indicated that the biocompatibility of CPSC is significantly enhanced.
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Simmons, Jane. "The structure and function of amorphous calcium phosphate biominerals." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.339520.
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