Дисертації з теми "Bose glasse"
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1
Kanwal, Nasima. "Novel zinc containing phosphate glasses for glass-ionomer cements for bone cement applications." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8440.
Повний текст джерелаАнотація:
Glass‐ionomer cements (GICs) are acid base reaction cements used in dentistry for restorative applications. In conventional GICs aluminosilicate glass is used to react with a polyalkenoic acid such as poly acrylic acid. Glass–ionomer cements have the potential to be used for bone cement applications, however there is a concern over the neurotoxicity of aluminium in the glass component of these cements. In this work zinc containing phosphate glass based glass–ionomer cement has been developed for the bone cement application. In this relation structure of zinc containing phosphate glasses in the system Na2O:CaO:ZnO:P2O5 ranging from metaphosphate compositions to invert phosphate compositions has been examined. Various advanced techniques in solid state nuclear magnetic resonance (NMR) such as dipolar recoupling and solid state NMR of low quadrupolar nuclei (67Zn and 43Ca) and neutron diffraction have been employed. Special emphasis has been focused on structural role of zinc in glasses of different composition and the effect of different cations on coordination of zinc along with the effect on phosphate tetrahedra. 67Zn and 43Ca solid state NMR spectra of selected glass samples have been successfully acquired at ultrahigh field 900 MHz using Solid Echo pulse sequence. In addition solid state NMR spectra of two polymorphs of crystalline Zn(PO3)2 have also been acquired at 850 MHz using DFS– WURST–QCPMG pulse sequence in order to distinguish between the magnitude and orientation of electric field gradient (EFG) of zinc in octahedral and tetrahedral coordination. Structure determined through various techniques has been related to the dissolution behaviour of glass compositions from metaphosphate to invert phosphate. A decrease in pH of surrounding medium has been observed due to the presence of zinc. Insertion of ZnO4 tetrahedra between PO4 tetrahedra has been observed in invert phosphate glasses with high zinc oxide content which renders them suitable for glass– ionomer cements. Glass–ionomer cement from glass composition 10Na2O:50ZnO:10CaO:30P2O5 and hydroxyapatite and, acrylic acid and vinyl phosphonic acid co‐polymer has been produced successfully.
2
Kapoor, Saurabh. "Alkali-free bioactive glasses for bone regeneration." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13951.
Повний текст джерелаАнотація:
Doutoramento em Ciência e Engenharia dos MateriaisBioactive glasses and glass-ceramics are a class of third generation biomaterials which elicit a special response on their surface when in contact with biological fluids, leading to strong bonding to living tissues. The purpose of the present study was to develop diopside based alkali-free bioactive glasses in order to achieve good sintering behaviour, high bioactivity, and a dissolution/ degradation rates compatible with the target applications in bone regeneration and tissue engineering. Another aim was to understand the structure-property relationships in the investigated bioactive glasses. In this quest, various glass compositions within the Diopside (CaMgSi2O6) – Fluorapatite (Ca5(PO4)3F) – Tricalcium phosphate (3CaO•P2O5) system have been investigated. All the glasses were prepared by melt-quenching technique and characterized by a wide array of complementary characterization techniques. The glass-ceramics were produced by sintering of glass powders compacts followed by a suitable heat treatment to promote the nucleation and crystallization phenomena. Furthermore, selected parent glass compositions were doped with several functional ions and an attempt to understand their effects on the glass structure, sintering ability and on the in vitro bio-degradation and biomineralization behaviours of the glasses was made. The effects of the same variables on the devitrification (nucleation and crystallization) behaviour of glasses to form bioactive glass-ceramics were also investigated. Some of the glasses exhibited high bio-mineralization rates, expressed by the formation of a surface hydroxyapatite layer within 1–12 h of immersion in a simulated body fluid (SBF) solution. All the glasses showed relatively lower degradation rates in comparison to that of 45S5 Bioglass®. Some of the glasses showed very good in vitro behaviour and the glasses co-doped with zinc and strontium showed an in vitro dose dependent behaviour. The as-designed bioactive glasses and glass–ceramic materials are excellent candidates for applications in bone regeneration and for the fabrication of scaffolds for tissue engineering.
Os vidros e vitrocerâmicos bioactivos fazem parte da chamada terceira geração de biomateriais, i.e., materiais que estimulam uma resposta especial quando em contacto com fluidos biológicos, capaz de conduzir ao estabelecimento de ligações fortes entre a sua superfície e os tecidos vivos. O presente estudo visou o estudo e desenvolvimento de vidros bioactivos à base de diópsido e isentos de metais alcalinos que apresentem um bom comportamento na sinterização, elevados índices de bioactividade, e taxas de dissolução / degradação compatíveis com as almejadas aplicações em regeneração óssea e em engenharia de tecidos. Procurou-se ainda entender as relações entre a estrutura e as propriedades dos vidros bioactivos estudados. De acordo com esta perspectiva, estudaram-se várias composições de vidros bioactivos pertencentes ao sistema Diópsido (CaMgSi2O6) – Fluorapatite (Ca5(PO4)3F) – Fosfato de tricálcico (3CaO•P2O5). Todas as composições vítreas foram preparados por fusão, seguida de fritagem em água fria, e caracterizados através de um conjunto de técnicas complementares de caracterização. Os vitrocerâmicos foram obtidos por sinterização das fritas de vidro moídas e compactadas, seguida de tratamento térmico adequado para promover os fenómenos de nucleação e cristalização. Além disso, algumas composições vítreas seleccionadas foram dopadas com vários iões funcionais e os seus efeitos na estrutura vítrea, na sua propensão para a sinterização, e nos comportamentos in vitro em termos de biodegradação e bio-mineralização foram avaliados. Os efeitos das mesmas variáveis no processo de devitrificação (nucleação e cristalização) dos vidros e formação de materiais vitrocerâmicos foram também investigados. Algumas composições de vítreas apresentaram taxas de bio-mineralização elevadas, expressas através da formação de camadas superficiais de hidroxiapatite após 1-12 h de imersão num fluido fisiológico simulado (SBF). Todas as composições vítreas apresentaram taxas de degradação mais baixas quando comparadas com a do 45S5 Bioglass®. Alguns vidros bioactivos revelaram comportamentos in vitro excelentes, sendo a taxa de biomineralização dos co-dopados com zinco e estrôncio dependente da dose incorporada de dopantes. Os materiais estudados demostraram boa aptidão para aplicações em regeneração óssea e para o fabrico de estruturas de suporte em engenharia de tecidos.
3
Shimer, Matthew Timothy. "Nonequilibrium Relaxation and Aging Scaling Properties of the Coulomb Glass and Bose Glass." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28926.
Повний текст джерелаАнотація:
We use Monte Carlo simulations in order to investigate the density of states and the two-time
density autocorrelation function for the two- and three-dimensional Coulomb glass as well
as the Bose glass phase of flux lines in type-II superconductors. We find a very fast forming
gap in the density of states and explore the dependence of temperature and filling fraction.
By studying two scaling methods, we find that the nonequilibrium relaxation properties can
be described sufficiently by a full-aging scaling analysis. The scaling exponents depend on
both temperature and filling fraction, and are thus non-universal. We look at the trends of
these exponents and found that as either the temperature decreases or the filling fraction
deviates more from half-filling, the exponents reflect slower relaxation kinetics. With two
separate interaction potentials, a comparison of relaxation rates and the gap in the density
of states is made.Ph. D.
4
Niederle, Astrid Elisa [Verfasser]. "Local Aspects of the Bose Glass – Phase transitions of the disordered Bose–Hubbard model / Astrid Elisa Niederle." München : Verlag Dr. Hut, 2016. http://d-nb.info/1113334800/34.
Повний текст джерела
5
Burling, Luke Donald. "Novel phosphate glasses for bone regeneration applications." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10161/.
Повний текст джерелаАнотація:
Phosphate glass with additions of sodium, magnesium and/or calcium were investigated for their potential to be used as the reinforcing phase in a completely degradable long fibre composite. Glasses were prepared from phosphate salts as opposed to oxides and melted under air in platinum/gold crucibles. The effect of cation addition on the material properties and biocompatibility was investigated. Glasses were characterised using a number of complimentary techniques, including: XRD, XPS, DSC, IR and EDX. The findings from these techniques were used to explain the observed thermal and dissolution properties. The thermal and dissolution properties were found to be dependant on both the thermal history and composition of the phosphate glass. For a phosphate glass with low cation content, the temperature and length of time held at that temperature increased the Tg by 10 C for sodium phosphate glass and slightly improved the durability of sodium phosphate glass containing 10 mol.% MgHPO4, as phosphate chain growth was greater under those conditions. Addition of divalent cations increased the Tg of phosphate glasses from 295 C for sodium phosphate glass by up to 150 C with the addition of 50 mol.% MgHPO4. The dissolution rate was decreased exponentially with the addition of calcium phosphate or magnesium phosphate to sodium phosphate glass. Rates as low as 1x10-7 g/(cm2.h) were achieved with the addition of 50 mol.% divalent cation phosphates. The divalent cations inhibited phosphate chain growth but formed a new network based upon divalent cation/non bridging oxygen cross-links. These cross-links were found to exert greater influence over the material properties then the phosphate chain length. Cell culture assays were used to establish the biocompatibility of phosphate glasses with different compositions. Preliminary tests were conducted with craniofacial derived osteoblast like cells cultured on glass surfaces. Initial assays performed showed that the most durable glasses sustained the greatest amount of proliferation and differentiation over a seven day period. The most promising glass compositions, 40 Ca, 40 Mg, 30 Mg/20 Ca and 20 Mg/30 Ca, and were selected for longer term osteoblast culture and short term macrophage culture. Long term osteoblast culture showed that cells were able to attach, spread and proliferate throughout the 28 day duration of the study. Assays performed on the culture showed that cells were differentiating, producing specific osteoblast markers for each of the three differentiation phases of proliferation, matrix maturation and mineralisation. ECM production and mineralisation was confirmed on all surfaces tested via type I collagen staining and alizarin red staining respectively. Over the 28 day period, it was found that the composition did not have a significant effect on the production of the osteoblast markers, namely alkaline phosphatase, collagen, osteocalcin and mineral deposition. Immunological studies show that macrophages are not activated by the presence of phosphate glass. This demonstrated that phosphate glass has shown potential for use a biomaterial.
6
Wasson, Eleanor A. "The development of glass-poly(alkenoate) [glass-ionomer] cements for orthopaedic applications." Thesis, Brunel University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295811.
Повний текст джерела
7
Niederle, Astrid Elisa [Verfasser], and Heiko [Akademischer Betreuer] Rieger. "Local aspects of the Bose glass : phase transitions of the disordered Bose-Hubbard model / Astrid Elisa Niederle ; Betreuer: Heiko Rieger." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2016. http://d-nb.info/1115721445/34.
Повний текст джерела
8
Alvarez, Zuniga Juan Pablo. "Analytical and numerical study of the Superfluid : Bose glass transition in two dimensions." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30051/document.
Повний текст джерелаАнотація:
Les effets conjoints du désordre (i.e. des impuretés) et des interactions constituent une des questions les plus fondamentales de la Physique de la Matière Condensée qui a reçu énormément d'attention dans les dernières décennies. La transition de phase quantique du Superfluide vers le verre de Bose déclenchée par le désordre s'est révélée énigmatique tant pour les théoriciens que pour les expérimentateurs et des questions restent ouvertes malgré tous leurs efforts. Les travaux présentés dans ce manuscrit abordent certaines de ces questions pour deux modèles de bosons de coeur dur désordonnés à deux dimensions : valeurs des exposants critiques qui gouvernent la transition ; propriétés inhomogènes des phases en compétition ; scénario physique au point critique ; propriétés de localisation des excitations bosoniques. On utilise trois approches différentes pour la transition afin d'explorer ce problème. En premier lieu, on montre comment les fractions superfluide et du condensat de Bose-Einstein sont affectées par le désordre dans une approximation de Champ Moyen qui, bien qu'incapable de capturer la transition, donne accès à des caractéristiques qualitatives intéressantes. En se basant sur cette solution Champ Moyen, on introduit les fluctuations quantiques à travers une théorie d'ondes de spin linéaires dans l'espace réel qui capture la transition et dévoile un comportement non trivial du spectre d'excitations. Finalement, on explore minutieusement la région critique quantique par des simulations de Monte Carlo Quantique à l'état de l'art, menant à une évaluation précise des exposants critiques et à une surprenante absence d'auto-moyennation dans le régime du verre de BoseThe interplay of disorder (i.e. impurities) and interactions is one of the most fundamental questions in Condensed Matter Physics that has received a lot attention in the past couple of decades. The quantum phase transition from Superfluid to Bose glass driven by disorder has puzzled theoreticians and experimentalists alike, leaving unresolved questions despite their best efforts. The work presented in this thesis addresses some of these questions for two models of disordered hard-core bosons in two dimensions. In particular, the values of the critical exponents governing the transition, the inhomogeneous properties of the competing phases, the physical scenario at criticality and the bosonic excitations' localization properties are investigated. Three different approaches to the transition are used to explore this problem. We first show how Bose-condensate and superfluid fractions are affected by disorder in a Mean-Field approximation, which is unable to capture a transition, but reveals interesting qualitative features. Building on such a Mean-Field solution, quantum fluctuations are then introduced using a linear spin-wave theory in real space which does capture the transition and furthermore unveils a non-trivial behavior for the excitation spectrum. Finally, the quantum criticality is explored in great detail using state-of-the-art Quantum Monte Carlo simulations, leading to a precise evaluation of the critical exponents and a surprising absence of self-averaging in the Bose glass regime
9
Xynos, Ioannis D. "Bioactive glasses for the in vitro synthesis of bone tissue." Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/11494.
Повний текст джерела
10
Toumpaniari, Sotiria. "Apatite-wollastonite glass ceramic scaffolds for bone tissue engineering applications." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3212.
Повний текст джерелаАнотація:
In bone tissue engineering, one of the main challenges is to fabricate scaffolds that promote and support osseous reconstruction. The research reported in this thesis considers the use of apatite-wollastonite (A-W) as a bone scaffold. A variety of scaffold fabrication techniques, all based on initially processing powder to create a pre-form for subsequent sintering, have been developed and characterised for their ability to create microporous; and interconnected macroporous scaffolds. A range of powder processing techniques were used: pelleting, dry powder and slurry moulding, and different powder particle size ranges were assessed for the preparation of microporous scaffolds to influence their surface roughness without significantly varying the porosity. To introduce macroporosity within the ceramic scaffolds that would be comparable in terms of scale and organisation to trabecular bone, a variety of methods were employed. Burning off negative templates such as polymeric particles, filaments and fused deposition modelling 3D constructs was investigated, together with a novel method based on thermally induced phase separation (TIPS), freeze-drying and sintering. Selected microporous scaffolds with different surface topography and pore size; and highly interconnected scaffolds with porosity >80% were fabricated with height 2± 0.1 mm and diameter 8- 10 mm depending on the fabrication method and the particle range that was used. The parameters that were evaluated in vitro were the effect of variable topographies on microporous constructs and the influence of high porosity on cell adhesion, proliferation and cell differentiation. It is concluded that the surface area of A-W scaffolds affects their bioactivity, degradation and mechanical properties. Microporous scaffolds with smaller pores allow cell-cell interaction and promote osteogenesis. Further investigation is required to clarify the observed chondrogenesis that occurred when MSCs were cultured on microporous scaffolds with larger pores. Highly porous A-W scaffolds allow cell infiltration, migration and demonstrate signs of osteochondral lineage differentiation.
11
Melo, P., E. Tarrant, Thomas Swift, A. Townshend, M. German, A.-M. Ferreira, P. Gentile, and K. Dalgarno. "Short phosphate glass fiber - PLLA composite to promote bone mineralization." Elsevier, 2019. http://hdl.handle.net/10454/17158.
Повний текст джерелаАнотація:
YesThe clinical application of composites seeks to exploit the mechanical and chemical properties of materials which make up the composite, and in researching polymer composites for biomedical applications the aim is usually to enhance the bioactivity of the polymer, while maintaining the mechanical properties. To that end, in this study medical grade Poly(L-lactic) acid (PLLA) has been reinforced with short phosphate-based glass fibers (PGF). The materials were initially mixed by melting PLLA granules with the short fibers, before being extruded to form a homogenous filament, which was pelletized and used as feedstock for compression moulding. As made the composite materials had a bending strength of 51 MPa ± 5, and over the course of eight weeks in PBS the average strength of the composite material was in the range 20–50 MPa. Human mesenchymal stromal cells were cultured on the surfaces of scaffolds, and the metabolic activity, alkaline phosphatase production and mineralization monitored over a three week period. The short fiber filler made no significant difference to cell proliferation or differentiation, but had a clear and immediate osteoinductive effect, promoting mineralization by cells at the material surface. It is concluded that the PLLA/PGF composite material offers a material with both the mechanical and biological properties for potential application to bone implants and fixation, particularly where an osteoinductive effect would be valuable.
funded in part by the EPSRC Centre for Doctoral Training in Additive Manufacturing and 3D Printing (EP/L01534X/1), the EPSRC Centre for Innovative Manufacture in Medical Devices (EP/K029592/1), and Glass Technology Services Ltd., Sheffield, UK.
12
Chen, Qizhi. "Bioglass®-derived glass-ceramic scaffolds for bone tissue engineering." Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/11497.
Повний текст джерела
13
Franks, Katrin. "The structure and properties of soluble phosphate based glasses." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326227.
Повний текст джерела
14
Ren, Jiongyu. "Development of melt electrospun composite scaffolds for bone regeneration." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/108824/1/Jiongyu%20Edward_Ren_Thesis.pdf.
Повний текст джерелаАнотація:
This thesis was a step forward in the development of an effective and patient-specific treatment for bone tissue loss using synthetic tissue engineered constructs. A novel polycaprolactone/strontium-substituted bioactive glass composite was fabricated into scaffolds with highly ordered fibre structure and promising osteogenic potential using an advanced additive manufacturing technique known as melt-electrospinning. The findings of this thesis provide an indispensable link in our understanding of future cell-free treatment for bone defects utilising fully synthetic bioactive scaffolds. The thesis also developed several histological assessment tools for evaluating current and future tissue engineered bone constructs utilised in pre-clinical animal studies.
15
Costa, Karine Piacentini Coelho da. "Condensados de Bose-Einstein em redes óticas: a transição superfluido-isolante de Mott em redes hexagonais e a classe de universalidade superfluido-vidro de Bose em 3D." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-19052016-220027/.
Повний текст джерелаАнотація:
Estudamos transições de fases quânticas em gases bosônicos ultrafrios aprisionados em redes óticas. A física desses sistemas é capturada por um modelo do tipo Bose-Hubbard que, no caso de um sistema sem desordem, em que os átomos têm interação de curto alcance e o tunelamento é apenas entre sítios primeiros vizinhos, prevê a transição de fases quântica superfluido-isolante de Mott (SF-MI) quando a profundidade do potencial da rede ótica é variado. Num primeiro estudo, verificamos como o diagrama de fases dessa transição muda quando passamos de uma rede quadrada para uma hexagonal. Num segundo, investigamos como a desordem modifica essa transição. No estudo com rede hexagonal, apresentamos o diagrama de fases da transição SF-MI e uma estimativa para o ponto crítico do primeiro lobo de Mott. Esses resultados foram obtidos usando o algoritmo de Monte Carlo quântico denominado Worm. Comparamos nossos resultados com os obtidos a partir de uma aproximação de campo médio e com os de um sistema com uma rede ótica quadrada. Ao introduzir desordem no sistema, uma nova fase emerge no diagrama de fases do estado fundamental intermediando a fase superfluida e a isolante de Mott. Essa nova fase é conhecida como vidro de Bose (BG) e a transição de fases quântica SF-BG que ocorre nesse sistema gerou muitas controvérsias desde seus primeiros estudos iniciados no fim dos anos 80. Apesar dos avanços em direção ao entendimento completo desta transição, a caracterização básica das suas propriedades críticas ainda é debatida. O que motivou nosso estudo, foi a publicação de resultados experimentais e numéricos em sistemas tridimensionais [Yu et al. Nature 489, 379 (2012), Yu et al. PRB 86, 134421 (2012)] que violam a lei de escala $\\phi= u z$, em que $\\phi$ é o expoente da temperatura crítica, $z$ é o expoente crítico dinâmico e $ u$ é o expoente do comprimento de correlação. Abordamos essa controvérsia numericamente fazendo uma análise de escalonamento finito usando o algoritmo Worm nas suas versões quântica e clássica. Nossos resultados demonstram que trabalhos anteriores sobre a dependência da temperatura de transição superfluido-líquido normal com o potencial químico (ou campo magnético, em sistemas de spin), $T_c \\propto (\\mu-\\mu_c)^\\phi$, estavam equivocados na interpretação de um comportamento transiente na aproximação da região crítica genuína. Quando os parâmetros do modelo são modificados de maneira a ampliar a região crítica quântica, simulações com ambos os modelos clássico e quântico revelam que a lei de escala $\\phi= u z$ [com $\\phi=2.7(2)$, $z=3$ e $ u = 0.88(5)$] é válida. Também estimamos o expoente crítico do parâmetro de ordem, encontrando $\\beta=1.5(2)$.In this thesis, we have studied phase transitions in ultracold atoms trapped in optical lattices. The physics of these systems is captured by Bose-Hubbard-like models, which predicts a quantum phase transition (the so called superfluid-Mott insulator, or SF-MI) when varying the potential depth of the optical lattice in a system without disorder, where atoms have short range interactions, and tunneling is allowed only between nearest neighbors. Our studies followed two directions, one is concerned with the influence of the geometry of the lattice namely, we study the changes in the phase diagram of the SF-MI phase transition when the optical lattice is hexagonal. A second direction is to include disorder in the original system. In our study of the hexagonal lattice, we obtain the phase diagram for the SF-MI transition and give an approximation for the critical point of the first Mott lobe, using a quantum Monte Carlo algorithm called Worm. We also compare our results with the ones from the squared lattice and obtained using mean-field approximation. When disorder is included in the system, a new phase emerge in the ground-state phase diagram intermediating the superfluid and Mott-insulator phases. This new phase is called Bose-glass (BG) and the quantum phase transition SF-BG was the subject of many controversies since its first studies in the late 80s. Though many progress towards its thorough understanding were made, basics characterization of critical proprieties are still under debate. Our study was motivated by the publication of recent experimental and numerical studies in three-dimensional systems [Yu et al. Nature 489, 379 (2012), Yu et al. PRB 86, 134421 (2012)] reporting strong violations of the key quantum critical relation, $\\phi= u z$, where $\\phi$ is the critical-temperature exponent, $z$ and $ u$ are the dynamic and correlation length critical exponents, respectively. We addressed this controversy numerically performing finite-size scaling analysis using the Worm algorithm, both in its quantum and classical scheme. Our results demonstrate that previous work on the superfluid-to-normal fluid transition-temperature dependence on chemical potential (or magnetic field, in spin systems), $T_c \\propto (\\mu-\\mu_c)^\\phi$, was misinterpreting transient behavior on approach to the fluctuation region with the genuine critical law. When the model parameters are modified to have a broad quantum critical region, simulations of both quantum and classical models reveal that the $\\phi= u z$ law [with $\\phi=2.7(2)$, $z=3$, and $ u = 0.88(5)$] holds true. We also estimate the order parameter exponent, finding $\\beta=1.5(2)$.
16
Barros, Manuel João Salazar Guedes de. "Fabrication of hydrogel-bioactive glass composite scaffolds for bone tissue engineering." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17461.
Повний текст джерелаАнотація:
Mestrado em Materiais e Dispositivos BiomédicosBone is an extremely important connective tissue in the human body, as it provides support and protection of internal organs, being also metabolically relevant as the main mineral reservoir and assuring haematopoiesis through the bone marrow. Due to the current ageing of the population, an increase in bone tissue related diseases is noticeable. Thus, more efficient therapies for treating bone diseases is crucial. Tissue Engineering appears as a promising technology for treating several of those problems, such as bone loss and joint problems. In the present work, composite biomaterials composed of a polymeric hydrogel matrix reinforced with bioactive glass particles were prepared. Individually, these materials have a high water content, which enhances their diffusive transport properties, and display osteogenic properties, respectively. The selected polymer was RGD functionalized pectin, due to its interesting properties, such as biocompatibility, cell-adhesive characteristics and adequacy for cell entrapment, and the bioactive glass selected was a novel alkali-free formulation of 70% diopside and 30% tricalcium phosphate (Di-70), composed of SiO2, CaO, MgO and P2O5. Several different composite formulations were tested, in which pectin concentration, bioactive glass content and glass particle size were varied. The biocomposite’s viscoelastic properties were assessed, as well as their biological behaviour through cytotoxicity assays, and osteogenic character by incubating mesenchymal stem cell (MSC)-laden composites into both basal and osteogenic media for up to 21 days. The results obtained demonstrated that a composite biomaterial with tuneable mechanical properties was successfully prepared, with in situ crosslinking ability within therapeutically relevant timeframes, and not requiring additional crosslinking strategies besides its own composition. Furthermore, its intrinsic osteogenic properties due to the glass composition provided the adequate conditions for promoting the differentiation of MSCs without osteogenic stimulation. The combined properties achieved indicate that the biocomposites prepared are suitable candidate cellularized biomaterials for bone tissue engineering applications.
O osso é um tecido conjuntivo de extrema importância no organismo humano, tendo funções como suporte ou proteção de órgãos internos, sendo também metabolicamente relevante como o principal reservatório de minerais e assegurando a hematopoiese com a medula óssea. Dado o envelhecimento da população, tem-se verificado um aumento da incidência de doenças degenerativas deste tecido, sendo assim essencial aplicar terapias altamente eficientes para o tratamento dessas patologias. A Engenharia de Tecidos surge como uma tecnologia promissora no tratamento destes problemas, como a perda de massa óssea e problemas nas articulações. Neste trabalho, foram produzidos biomateriais compósitos, baseados numa matriz polimérica sob a forma de hidrogel reforçada com partículas de vidro bioativo. Individualmente, estes materiais apresentam um elevado teor em água favorável ao transporte de nutrientes, e propriedades osteogénicas, respetivamente. O polímero selecionado foi a pectina funcionalizada com RGD, dadas as suas propriedades interessantes como a biocompatibilidade, capacidade de promover a adesão celular e adequabilidade para o encapsulamento de células, e o vidro bioativo apresenta uma composição de 70% de diópsido e 30% de fosfato tricálcico (Di-70) isento de alcalinos e sendo composto por SiO2, CaO, MgO e P2O5. Diferentes formulações de hidrogéis compósitos foram testadas, em que se variou a concentração de polímero, a concentração de biovidro e o seu tamanho de partícula. Analisaram-se as propriedades viscoelásticas dos biocompósitos, bem como o seu comportamento biológico, com ensaios de citotoxicidade, e ainda as propriedades osteogénicas do material, pela incubação de hidrogéis contendo células estaminais mesenquimais (MSCs) em meio basal e osteogénico durante 21 dias. Os resultados deste trabalho indicam que foi possível preparar um biomaterial compósito de propriedades mecânicas ajustáveis, com capacidade de reticular in situ em tempos clinicamente desejáveis sem necessitar agentes reticulantes externos. Para além disso, as propriedades osteogénicas intrínsecas do biovidro forneceram as condições adequadas para a promoção da diferenciação de MSCs sem estimulação osteogénica adicional. As propriedades combinadas alcançadas indicam que os biocompósitos preparados têm potencial para ser aplicados em engenharia de tecido ósseo.
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Sabree, Israa. "Fabrication of bioactive glass scaffolds by stereolithography for bone tissue engineering." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/fabrication-of-bioactive-glass-scaffolds-by-stereolithography-for-bone-tissue-engineering(83a17853-1626-4ef2-bb7e-45c07834359c).html.
Повний текст джерелаАнотація:
Bone tissue engineering aims to regenerate the bone structure and therefore recover the functions of bone tissue rather than replacing it alone. Regenerative medicine focuses on using biomaterials as three-dimensional (3D) porous scaffolds, specifically designed to mimic the nature of host tissue and hence to promote cell growth and tissue regeneration. For such purposes, 3D bioactive glass scaffolds are one of the most studied types of scaffolds for bone tissue engineering because of their excellent bioactivity and potential for stimulating osteogenesis and angiogenesis. In the present study stereolithography has been used to fabricate negative moulds for use with the gel casting process to produce porous 3D 70%SiO2-30%CaO2 bioactive glass-ceramic scaffolds with three different pore sizes and identical porosity. A scaffold with 50 vol. % solid loading suspension was successfully manufactured in two different 3D external shapes and three pore sizes. The bioactive glass powder was crystallized at a temperature of 865.5°C. The mechanical behaviour of the scaffolds sintered at 1200⁰C was found to be influenced by pore size despite the similarity in porosity and the scaffold compressive strength decreased, and the failure probability increased, with increasing pore size. This behaviour was found to be consistent with the predictions of Weibull statistics. All three scaffold types exhibited a compressive strength within the strength range of human trabecular bone. The indentation hardness of the scaffold struts was found to be close to that of cortical bone. In vitro investigation of the scaffolds’ bioactivity was achieved through examining changes in the composition of the immersion solution. Biological tests showed that all scaffolds significantly enhanced cell proliferation, deposition of collagen, alkaline phosphatase activity and the expression of osteocalcin with an increasing rate of mineralisation throughout the culture period; this is believed to be due to the action of released ions from the bioactive glass which induces osteoblast cells from their proliferation phase to a mineralisation stage. A 3D sliced scaffold was produced from an assembly of quasi-2D slices to investigate cell behaviour throughout the scaffold. The goal of in vitro studies of the sliced scaffolds with different pore size is to improve the understanding of how scaffold pore size impacts on initial cell attachment, tissue ingrowth and mass transfer through the scaffold. The results confirmed that a scaffold with bigger pore size provided more space for tissue ingrowth and mass transfer throughout the scaffold over long culture periods. The findings suggest that the fabricated 3D 70%SiO2-30%CaO2 bioactive glass-ceramic scaffolds have potential for use in bone tissue engineering applications.
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Lotfibakhshaiesh, Nasrin. "High phosphate strontium containing bioactive glass coatings for bone tissue engineering." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/7090.
Повний текст джерелаАнотація:
The need for prosthetic joint implants continues to grow, but many implants fail and require revision surgery, mainly due to non-bonding to bone. Currently many metal prostheses are coated with hydroxyapatite (HA), often giving rise to ceramic particles leading to wear of the prosthesis surface. This thesis describes the development of bioactive glass (BG) coatings for metallic implants to improve the bone-implant bond, enable better osseointegration, and improve implant lifespan. Strontium was substituted for calcium in two series of melt-derived BG based on the SiO2-MgONa2O- K2O-ZnO-P2O5-CaO system. In the first series, 0, 10, 25, 50, 75 and 100% of the CaO was replaced by SrO; and in the second series 10% of the CaO was replaced by SrO and the P2O5 content was varied between 1.07 and 6.42 mol%. Ti alloy coupons were surface coated with BG by enamelling technique. The structural and physical properties of the glasses and glass coatings were investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Amorphous coatings showed good adhesion to the Ti alloy with the exception of the 100% Srsubstituted coating. The mixed calcium/strontium glasses exhibited a larger processing window; temperature difference between glass transition and onset of crystallization temperature; favouring the production of amorphous well sintered coatings. Dissolution profiles and bioactivity of the produced glasses were investigated by inductively coupled plasma-optical emission spectroscopy (ICP-OES), XRD, NMR and FTIR. Increasing the P2O5 content of the Sr-substituted glasses aided the formation of the hydroxycarbonate apatite (HCA) layer in SBF. 31P and 29Si NMR showed that the glasses were phase separated with a predominantly Q2 silicate structure co-existing with phosphorus in a predominantly Q0 orthophosphate environment. The Q2 silicate structure in the network did not change with substitution of SrO for CaO. LIVE/DEAD staining of human osteosarcoma cells (Saos-2) seeded onto BG coatings indicated that the coatings were not cytotoxic. SEM imaging showed that the cells attached and spread over the coating surface. The degree of osseointegration of the high-phosphate Sr-contatining (50% of the CaO replaced by SrO) BG-coated implants were compared with HA-coated implants up to 24 weeks which were inserted into lapine long bones (distal femur, proximal tibia). High-phosphate Sr-containing BGcoated implants demonstrated superior mechanical fixation and increased peri-implant bone formation compared to HA-coated implants. The results presented in this thesis demonstrate the potential of Srsubstituted BGs with high-phosphate content for the coating of metallic joint implants.
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Nommeots-Nomm, Amy Elizabeth. "3D printing versus foaming of melt-derived bioactive glasses for bone regeneration." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/50295.
Повний текст джерелаАнотація:
Bioactive glasses have the ability to regenerate bone defects as they form a rapid bond with bone and their dissolution products can stimulate new bone growth. The original Bioglass® 45S5 composition (46.1 mol% SiO2, 26.9 mol% CaO, 24.4 mol% Na2O, and 2.6 mol% P2O5) is available as a clinical product in a particulate form, but surgeons require scaffolds that can act as temporary templates for bone repair. Bioglass 45S5 cannot be made into porous scaffolds while maintaining an amorphous glass structure, due to its susceptibility to crystallise during sintering. New melt-derived glass compositions have recently been developed which avoid crystallisation, enabling bioactive glasses to be made into porous constructs. The aim of this thesis was to investigate the relationship between glass composition and scaffold production techniques. Three glasses compositions were used, ICIE16 (49.46 SiO2, 36.27 CaO, 6.6 Na2O, 1.07 P2O5 and 6.6 K2O, in mol%), 13-93 (54.6 SiO2, 22.1 CaO, 6.0 Na2O, 1.7 P2O5, 7.9 K2O, 7.7 MgO, in mol%) and SBP-3 (44.5 SiO2, 17.8 CaO, 4.0 Na2O, 4.5 P2O5, 4.0 K2O, 7.5 MgO, 17.8 SrO, in mol%), each with an extended thermal processing window. These glasses were made into 3D scaffolds utilising two processing techniques: an adapted gel-cast foaming and, for the first time, robocasting. Here we present the adaption and optimisation of these techniques. The three glass compositions, ICIE16, 13-93 and SBP-3, all have different modified network connectivities (mean number of bridging Si-O-Si bonds per silicon atom, NC’) of 2.13, 2.84 and 3.01 respectively. In vitro and in vivo analysis were completed to understand how the different glass chemistry affected their bioactivity and dissolution characteristics. The composition of ICIE16 chemistry was the most similar to the original 45S5 composition was shown to promote and sustain better bone ingrowth than comparable scaffolds produced from SBP-3.
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Kara, Alpagut. "Characterisation of the interfaces between leadless glazes and a bone china body." Thesis, University of Bath, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268189.
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Al-Qaysi, Mustafa. "Development of phosphate based glass scaffolds for the repair of craniofacial bone." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10047384/.
Повний текст джерелаАнотація:
Degradable phosphate-based glasses have been known to have many potential properties to work as biomaterials for bone repair clinical applications. Although several studies were performed on different compositions to investigate the most appropriate glass formula, no specific formula was found to be the most favourable for clinical application. The main aim of this thesis was to fabricate and biologically assess phosphate glass scaffold made from specific elements known for their potential in promoting bone growth. To achieve this, primary studies were done on four different compositions of both zinc and strontium phosphate-based glass discs. The next study was to further investigate the best two zinc and strontium glass compositions that were obtained from the primary studies using glass beads. As a result of this study, specific composition of both zinc and strontium phosphate glass, having the most favourable cellular response, was recommended to be used for the following experiments. Based on previous compositions, another study was performed to surface functionalise glass discs by coating them with carbon nanotubes (CNTs) and polycaprolactone polymer (PCL) to assess the effect of surface modification on cellular adhesion and metabolic activity. This was subsequently followed by manufacturing, mechanical testing and structural evaluation of zinc and strontium scaffolds. Another experiment was carried out to identify the most suitable technique for scaffold cells seeding by coating scaffolds with fibronectin and collagen. The final study aimed to assess different types of zinc and strontium phosphate glass scaffolds (non-coated, CNT-coated) in both static and dynamic conditions. For the assessment of these scaffolds under dynamic conditions, a perfusion bioreactor was custom made that worked continuously for 28 days. The results revealed that the most preferable glass compositions were identified as ZnO5% and SrO17.5%. Also, glass coating with CNTs and PCL has found to encourage cells adhesion and metabolic activity as it enhanced both surface roughness and hydrophilicity. Scaffold production by sintering technique was thermally optimised and scaffold cellular seeding using collagen coating has yielded the most efficient seeding density. The final results displayed that the most suitable cellular response was found in CNT and PCL coated scaffolds under dynamic conditions (perfusion bioreactors cultivated scaffolds).
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Lakhkar, N. J. "Phosphate glass microspheres as cell microcarrier substrates for bone tissue engineering applications." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1436722/.
Повний текст джерелаАнотація:
Phosphate glasses have demonstrated a high degree of suitability for use as biomaterials in a wide range of biomedical applications involving both hard and soft tissue regeneration. This study focused on the use of these glasses as substrate microcarrier materials for three-dimensional bone tissue formation. For this purpose, the successful production of phosphate glass microspheres in the ~10–200 μm size range was demonstrated using a simple, inexpensive and industrially scalable process. Microspheres made out of two different series of phosphate glass compositions were investigated: (a) iron phosphate glasses 0.5P2O5–0.4CaO–(0.1 – x)Na2O–xFe2O3 where x = 0.00, 0.01, 0.03 and 0.05 mole fraction and (b) titanium phosphate glasses 0.5P2O5–0.4CaO–(0.1 – x)Na2O–xTiO2 where x = 0.00, 0.01, 0.03, 0.05 and 0.07 mole fraction. Investigations of the microsphere physicochemical properties revealed the densification of the glass structure with increased metal oxide incorporation in the glass. Glass structural characterisation studies provided valuable information relating the physicochemical properties to glass structural arrangements at the glass phase and atomic levels. Cell culture studies involving culture of the microspheres with MG63 osteosarcoma cells and human mesenchymal stem cells indicated that microspheres made of glasses containing 3–7 mol% metal oxides, and particularly those containing 5 mol% TiO2, showed favourable characteristics in terms of cell attachment, viability, proliferation and release of proteins related to cell differentiation and metabolism under both static conditions in culture well plates and dynamic conditions in spinner flask bioreactors. Taken together, the results provide evidence of the potential of the investigated glass microspheres to function as effective microcarrier substrates for bone tissue engineering applications.
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Fu, Qiang. "Freeze casting of bioactive glass and ceramic scaffolds for bone tissue engineering." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2009. http://scholarsmine.mst.edu/thesis/pdf/Fu_09007dcc806b51af.pdf.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--Missouri University of Science and Technology, 2009.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 7, 2010) Includes bibliographical references.
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Santocildes, Romero Martin Eduardo. "Electrospun poly(caprolactone) and strontium-substituted bioactive glass for bone tissue engineering." Thesis, University of Sheffield, 2014. http://etheses.whiterose.ac.uk/5690/.
Повний текст джерелаАнотація:
Electrospinning is a technique which has been widely studied to fabricate fibrous polymeric membranes. More recent work has demonstrated the preparation of composite fibres by incorporation of ceramic or glass particles in the spinning process. However, the incorporation of strontium-substituted bioactive glasses (Sr-BGs) into electrospun membranes has not yet been studied with detail. This is perhaps surprising, as Sr-BGs have been reported to exhibit superior osteogenic activity compared to conventional bioactive glasses. Therefore, the aim of this project was to fabricate electrospun composite materials combining poly(caprolactone) (PCL) and Sr-BG particles, and to study their potential use as scaffolds for bone tissue engineering. Here, three Sr-BGs in which calcium was substituted by strontium in molar proportions of 0, 50 and 100% were prepared and characterised. Glass particles with sizes < 45 μm were prepared by milling and sieving, and added to PCL solutions before electrospinning. The resulting composite materials were then examined using scanning electron microscopy, energy dispersive X-ray spectroscopy (EDS), and by performing solubility and cytotoxicity studies. Two methods to add Sr-BG particles to the surface of the fibres were also investigated. The effect of Sr-BG dissolution on mesenchymal stromal cells (MSCs) was studied by assessing cytotoxicity and the expression of six genes associated with osteoblastic differentiation. Strontium substitution resulted in a reduction of glass transition temperature, increased density and increased solubility of the glasses. EDS confirmed the presence of Sr-BG particles within the electrospun fibres. Solubility studies suggested an accelerated degradation of PCL due to Sr-BG dissolution in the composite fibres, with an apparent effect on medium pH. All the materials generally presented good levels of in vitro biocompatibility, although the addition of particles to the surface of the fibres increased their apparent cytotoxicity in some cases. Sr-BG dissolution was associated with an up-regulation of genes involved in the process of osteoblastic differentiation. It was concluded that Sr-BGs may indeed enhance osteogenic differentiation in MSC populations, and electrospun PCL/Sr-BG showed great potential for use as a versatile medical device or scaffold for bone tissue regeneration.
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Yu, Bobo. "New sol-gel derived bioactive glasses and organic/inorganic hybrids for bone regeneration." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/7067.
Повний текст джерелаАнотація:
Sol-gel derived bioactive glasses have been considered as one of the most promising materials for bone regeneration. However they are brittle, therefore composites are needed if bioactive materials are to share load with bone. One strategy for production of composites with tailored mechanical properties and congruent degradation rates is the development of inorganic/ organic hybrids. Hybrids are particular types of nanocomposite synthesised by introducing a polymer into the sol-gel process so that the silica and polymer chains interact at the nanoscale. Calcium must be incorporated into glasses and hybrids if they are to be bioactive (e.g. bone to bone). Calcium nitrate is conventionally used in the sol-gel process as the calcium source. However, there are many disadvantages of using it. Calcium nitrate causes inhomogeneity by forming calcium rich regions and it requires high temperature treatment (>400⁰C) to be incorporated into the glass network. Calcium nitrate cannot be used in the synthesis of hybrids where the highest temperature used in the process is approximately 60⁰C. Therefore, a different precursor is needed to improve homogeneity of glasses and for low temperature synthesis of hybrids. In this work, two alternatives were investigated and compared to the conventional approach of using calcium nitrate: calcium chloride, an alternative calcium salt, and calcium methoxyethoxide (CME), a calcium alkoxide. The structure of the gels and glasses were investigated over a range of final processing temperatures from 60⁰C to 800⁰C, corresponding to hybrid and glass process temperatures using advanced probe techniques such as solid state NMR. The temperature at which calcium was incorporated into the network was identified for 70S30C (70 mol% SiO2, 30 mol% CaO) and 58S (60 mol% SiO2, 36 mol% CaO, 4 mol% P2O5) compositions synthesised with the three different calcium precursors. Using calcium nitrate, calcium did not enter the silica network until temperatures greater than 380⁰C were reached. When calcium chloride was used, the calcium did not seem to enter the network at any of the temperatures. In contrast, calcium from CME entered the silica network at room temperature, indicating CME is an improved calcium source for low temperature synthesis. An aim of this work was to synthesise poly(γ-glutamic acid)/ silica hybrids, containing calcium, using calcium chloride and CME. Calcium incorporation was much improved when CME was used and mechanical properties were much improved compared a sol-gel glass or hybrids synthesised with other calcium sources. A hydroxycarbonated apatite (HCA) formed on the hybrids after immersion in simulated body fluid (SBF), indicating bioactivity. Polylactide was also trialled as the organic phase for hybrid synthesis, using polylactide-diol (PLAD). However, synthesis of PLAD/bioactive glass hybrid was not successful as it was difficult to incorporate the functionalised polymer into the sol. Calcium incorporation into the silica network using the sol-gel process is therefore possible but challenging.
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Jabur, Roberto de Oliveira. "Avaliação clínica, histológica e histomorfométrica do reparo de defeitos ósseos criados em mandíbula de cães preenchidos com Biovidro 45S5 ou Biosilicato® após a colocação de implantes osseointegráveis." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/58/58136/tde-23012009-170150/.
Повний текст джерелаАнотація:
O presente trabalho avaliou a formacao de tecido osseo ao redor de implantes osseointegraveis de titanio, apos realizacao de defeitos osseos, utilizando diferentes tipos de substitutos osseos. Foram utilizados 5 caes de raca indeterminada, os pre molares e molares mandibulares foram extraidos, passados 12 semanas, os caes foram submetidos a um novo procedimento cirurgico aonde foram realizadas as perfurações preconizados pelo fabricante dos implantes, o osso vestibular da mandibula foi desgastado ate que parte da perfuracao fosse exposta, os implantes entao foram colocados nas respectivas perfuracoes, ficando com 4 espiras expostas. Esses defeitos foram preenchidos aleatoriamente com Bioglass® 45S5, Biosilicato® , Osso autogeno, e sem nenhum material de preenchimento. 18 semanas depois da colocacao dos implantes os caes foram mortos e suas hemi-mandibulas contendo os implantes removidas e submetidas aos analises histologiaos e histomorfometricas, os dados obtidos foram submetidos ao teste de Kruskal-Wallis. A histologia dos 4 grupos estudados revelaram a presenca de tecido osseo maduro em contato com os implantes, porem sem ralacao direta com os vidros bioativos e osso autogeno. A porcentagem de contato osso implante, matriz ossea mineralizada ao redor da espira, e area de espelho, nao mostraram diferencas estatisticas significantes entre os 4 materiais testados. Os resultados indicam que a presenca de substitutos osseos nao interfere com a formacao ossea ao redor dos implantes nesse modelo experimental. E existe resposta tecidual muito semelhante entre o osso autogeno, Bioglass® 45S5 e Biosilicato.The aim of the present study was to investigate the amount of bone formation on Ti implants in sites with intra-bony defects filled with different bone substitutes. Mandibular premolars and first molars were extracted from 5 dogs, and after 12 weeks 3 implants were bilaterally placed in sites with intra-bony defects and each implantation site randomly received the following treatment: Biosilicate®, Bioglass® 45S5, aoutologous bone or no treatment. At 18 weeks after implantation, the hemi-mandibles containing the implants were removed and processed for morphological and histomorphometric analysis. Data were submitted to Kruskal-Wallis and Fishers test. The histological sections of the 4 experimental groups exhibited mature bone tissue in contact with implants, but not related with bioactive glasses or autologous bone used. The percentage of bone-implant contact, mineralized bone matrix between implant threads, and mineralized bone matrix within mirror area in the treated or non-treated sites were not statistically different among the 4 experimental groups. These results indicates that the presence of the bone substitutes evaluated here did not interfere with bone formation on Ti implants in sites with intra-bony defects. In addition, tissue response to Biosilicate® was similar to that of Bioglass® 45S5 and autologous bone.
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Candarlioglu, Lutfiye Pelin. "Biological characterization of strontium substituted bioactive glass as a new bone graft material." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/39385.
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Miller, Cheryl Ann. "Crystalisation of canasite/frankamenite based glass-ceramics for bone tissue repair and augmentation." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274946.
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Kent, Niall William. "Development of a novel in-vivo setting bone graft substitute from bioactive glass." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8442.
Повний текст джерелаАнотація:
Calcium phosphate cements are in-vivo setting, injectable calcium phosphate based biomaterials. They are made of calcium phosphate salts which when mixed with water react to form apatite, the mineral phase of bones and teeth. This study investigates a novel way of forming calcium phosphate cements using bioactive glasses. The aim of the work was to discover a novel route of synthesis using a silicate bioactive glass. Fifteen glass compositions were produced designed to investigate P2O5 content, CaF2 content and calcium to sodium ratio within the glass. Glasses were produced via a melt-quench route before being milled and sieved to below 38 μm. The bioactive glass and Ca(H2PO4)2 powders were mixed in an overall calcium to phosphate ratio of 1.67. The cement powder was then reacted with a 2.5 % solution of Na2HPO4. The paste was then mixed and then placed into cylindrical moulds. Eight samples were immersed into Tris buffer solution for 1 hour, 1 day, 7 days or 28 days. The compressive strength was measured for each specimen as well as SEM performed and the setting times for each composition was studied using the Gilmore needle test. The cement phase was analysed using 31P & 19F MAS-NMR, FTIR and XRD. The results showed that both compressive strength and setting time was dependent upon glass composition. As sodium content was increased both the initial and final setting times decreased. Increased fluoride addition caused a decrease in the setting time. In the fluoride free compositions octacalcium phosphate was identified in all compositions. The cement setting reaction for these compositions followed a similar reaction of first forming dicalcium phosphate dihydrate which transformed to octacalcium phosphate then eventually hydrolysing to hydroxyapatite. When fluoride was incorporated into the cement the phases formed were fluoridated-apatite and DCPD. In conclusion a novel method of producing calcium phosphate cements was discovered using a bioactive glass as a reactive precursor. It was shown that the cement phase, setting time and compressive strength could all be altered by changing the glass composition.
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Tang, Hok Man. "Porous melt-derived bioactive glass scaffolds for bone regeneration via gel-cast foaming." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24844.
Повний текст джерелаАнотація:
Scaffolds suitable for trabecular bone regeneration were produced via the gel-cast foaming process using the melt-derived glass composition SBP-3. A problem common to most bioactive glass compositions that undergo sintering in order to achieve scaffold form is that they crystallise, lowering bioactivity as well as incurring mechanical instability of the structure via unpredictable local degradation. The scaffolds did not exhibit significant bulk crystallisation upon sintering and the presence of potassium sodium sulphate crystals were not detected on the surface, which were formed with a previously studied composition ICIE16. The process was then optimised further and up-scaled to produce scaffolds in sufficient quantities for an in vivo ovine condyle defect study (undertaken at University College London by Prof. Allen Goodship and Prof. Gordon Blunn). Despite possessing a relatively high network connectivity - 2.31 - and low bioactivity from SBF studies, results from the in-vivo study concluded that the SBP-3 scaffolds performed better than the original 45S5 Bioglass granules, displaying 99 % bone aposition over a period of 91 days, in addition to the new bone more closely resembling the trabecular bone structure. Work was then carried out to simplify the process, switching from a chemical polymerisation process to a thermal gelation process, thus allowing for greater optimisation of the process.
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Serna, Christopher. "Development of a synthetic trabecular bone graft utilizing a two phase glass-ceramic." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/17705/.
Повний текст джерелаАнотація:
The aim of this work was to produce and characterise porous glass-ceramic scaffolds that mimicked human trabecular bone through the foam replica technique. Parent glasses were formed via a melt quench route to produce glass frits, these were then processed into powders consisting of < 45 µm particles confirmed through particle analysis. DSC analysis confirmed a glass transition region of ~ 750 °C, two crystallisation peaks were noted at 886 °C and 942 °C. Combining multiple glass batches exhibited properties consistent with single batch analysis, allowing for scale up of glass volumes and sample sizes for characterisation. Slurries of varying ratios of glass and binder (polyvinyl alcohol) were then produced and used to coat a polyurethane foam template. Two distinct heat treatments were then designed from initial studies; SEM analysis confirmed a dwell at 800 °C for 5 hours sufficiently sintered the glass particles, XRD analysis confirmed a tertiary dwell at 950 °C for 1 hour formed both apatite and wollastonite phases. Biaxial flexural testing and micro-CT analysis showed that with decreasing glass content within the initial slurry the resultant mechanical and architectural properties diminished. Excessive use of binder within the initial slurry was also found to diminish the consistency and properties of the scaffolds produced. Coating the porous scaffolds with fluorapatite was shown to be feasible; the crystallinity of the substrate was found to alter the resultant crystal morphologies. Human adipose derived stem cells (hADSC’s) were shown to both attach and proliferate on scaffolds, with or without a fluorapatite coating.
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Loy, Chee Wah. "The synthesis and microstructure characterisation of bioglasses, bioglass-ceramics and glass-ionomer cements for bone and dental restoration." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/18806.
Повний текст джерелаАнотація:
This PhD thesis presents the synthesis and microstructure characterisation of Ca-fluoroaluminosilicate (CFAS) glasses, fluorapatite glass-ceramics and glass-ionomer cements (GICs) for bone and dental restoration. The first part of the thesis presents the crystallographic, chemical and thermal characterisation of starting waste materials. CO2-sequestration was exploited to convert aluminium cans to aluminas. The microstructures of aluminas were investigated using a SEM-EDX and SANS. The effects of heat treatment on the phase transformation of oyster shells and rice husk ash are also reported. The second part of the thesis includes the synthesis and microstructural investigations of 13 CFAS glasses. These are synthesised in parts from waste materials via melt-quench technique. The CFAS glass compositions are varied within the SiO2–Al2O3–CaO–Na2O–CaF2–P2O5 system. The microstructures of these glasses are studied using SANS, USANS and SAXS. The results provide microstructural information for the glass particles over a size range from 1 nm to 10 µm. The third part presents sinter-crystallisation of the CFAS glasses to fluorapatite glass-ceramics. The conditions to synthesise fluorapatite-mullite, fluorapatite-anorthite and fluorapatite-albite glass-ceramics are also established. The phase transformations of glass-ceramics are studied using PXRD, infrared spectroscopy, SANS and STA. The last part reports the chemical and microstructural evolution of GIC pastes during the cement setting reaction. GIC pastes are formulated from a mixture of CFAS glass, polyacrylic acid and water. The setting reaction of GIC pastes is investigated using in-situ infrared spectroscopy and SANS. The results showed the formation of cross-links within polyacrylate chains and the thickening of siliceous hydrogel layers surrounding the glass particles. The GICs acquired high mechanical strength (~60 MPa) after one month of setting, and performed as well as the commercial LG26 glass.
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Brook, Ian Michael. "Evaluation of glass-ionomer cements for use as bone substitutes with reference to their value for treatment of atrophic alveolar bone." Thesis, University of Sheffield, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.695353.
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Ainsworth, Madison. "The development of strontium-substituted bioactive glass composite scaffolds for patient-specific bone repair." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/203941/1/Madison_Ainsworth_Thesis.pdf.
Повний текст джерелаАнотація:
Large (critical-sized) bone defects present a regenerative challenge to the body. Scaffold-based tissue engineering techniques can potentially address the challenge through the convergence of patient-specific design and novel biomaterials. This project investigated the in vitro bone forming capacity of a bioactive composite biomaterial scaffold produced with a high-resolution 3D printing technique: melt electrowriting (MEW). The MEW fabricated composite material was found to enhance the differentiation of bone-forming cells.
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Sahlin-Platt, Annika. "Bone tissue regeneration indento-alveolar surgery : clinical and experimental studies on biomaterials and bone graft substitutes." Doctoral thesis, Umeå universitet, Institutionen för odontologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-47418.
Повний текст джерелаАнотація:
Pathological processes in the alveolar and facial bones can lead to bone loss that may not heal with complete regeneration. Biomaterials can be used to facilitate the healing process and/or as a bone substitute, but the mechanisms are not fully understood. Persistent leakage of bacteria/bacterial toxins, after root canal treatment, may lead to a residual bone defect. The healing is dependent on a placed dental biomaterial providing a tight seal. The composition of the filling material may also influence the healing process. The general aim of this study is to investigate surface properties and biological interactions of biomaterials used in dento-alveolar surgery. A dental biomaterial, a bonded compomer (DAP) containing a corroding glass filler, was used as a root end filling material, promoting a new operation technique. The healing (assessed according to Molven´s x-ray criteria) demonstrates a significant improvement in healing results for the compomer group, compared to a commonly used technique. The surface properties and biological interactions of DAP were analyzed. ICP-OES of DAP cell culture medium extract demonstrated a significant release of Sr, Si and F from the dental biomaterial. Human periodontal ligament (PDL) cells grew on and around DAP specimens without any sign of toxic reactions. DAP extract stimulated proliferation of PDL cells, but caused an inhibition of osteoblastic gene expression in mouse bone marrow cells. The surface properties of the glass containing compomer may contribute to improved healing of the periapical lesions. A bovine inorganic bone graft substitute (BO) is commonly used as a treatment option in dento-alveolar surgery with new bone formation in immediate close contact with BO material. ICP-OES dissolution analysis of cell culture media, after incubation with BO particles, demonstrated a dosedependent release of Si and a decrease of Ca and P. An uptake of Ca from the medium to the BO particle was demonstrated with calcium-45 labeling. The Si dissolution varied between different batches, possibly reflecting a variation in food intake in the animals. Stimulated osteogenic response was seen in close contact to the BO particles in cell cultures. Furthermore, it was clearly demonstrated that the study design is a critical factor for correctly understanding biomaterials’ biological interactions. The surface properties of three bone graft substitutes reported to have good results in dento-alveolar surgery were investigated, in order to establish whether or not dissolution-precipitation reactions could contribute to the bone healing. Dissolution-precipitation extracts of BO, bioactive glass 45S5 (BG) and a marine algae hydroxyl apatite (AP) in cell culture media were analyzed. Dissolution of Si at significant levels was detected for BO and 45S5 over time. Significant uptake levels of Ca and P from the culture were seen for both 45S5, BO and AP but at different times. Surface analysis of the biomaterials with SEM/EDAX, before and after immersion in cell culture media, revealed a smoothing of the surface morphology for 45S5 over time. No obvious alterations for BO and AP were detected. Ca/P ratio decreased significantly for 45S5, but no major changes were detected by XPS for BO or AP. XPS further demonstrated a surface charge for BO, changing from negatively to positively charged when exposed to serum. 45S5 and AP had positive surface charges, both in the absence and the presence of serum. These demonstrated surface changes in biomaterials could contribute to adherence of cells and subsequently affect bone healing. Conclusion: Biomaterials used in dento-alveolar surgery interact with biological surroundings through surface and dissolution-precipitation reactions which may have implications for bone healing.
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Ansari, Sonia. "The Effect of Interpenetrating Network on the Physico-Chemical Properties of Polymer-Bioactive Glass Hybrid Monolith for Bone Tissue Regeneration." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/15998.
Повний текст джерелаАнотація:
The organic-inorganic hybrid is a favourable material for bone tissue engineering. However, the brittleness and rapid degradation of these monoliths restrict their application for engineering, soft tissues and their interfaces with bone. The aim of this project was to address the issue of brittleness and phase separation by introducing an interpenetrating network between the polymer and bioactive glass. In this study, the physicochemical properties and mechanical strength of these hybrid monoliths were tuned by incorporating a cross linking agent poly (ethylene glycol diacrylate) (PEGda). The results of molecular scale analysis demonstrated that at an optimum condition of 40:60 (v/v %) polymer: bioactive glass, an interpenetrating network between poly (lactide ethylene oxide fumarate) (PLEOF) and bioactive glass during the sol-gel process, resulted in the fabrication of a hybrid monolith. The feasibility of fabricating a PLEOF-Bioactive glass hybrid monolith with improved mechanical properties was also investigated by increasing the concentration of polymer in the hybrid structure. We observed ten-fold decrease in the compressive modulus of hybrid monolith compare to pure bioactive glass, which is favourable for bone tissue application. In addition to remarkable enhancement in the mechanical properties of PLEOF-Bioactive glass hybrid, their structural integrity was significantly increased. These hybrid monoliths kept their structure for more than 28 days in simulated body fluid. In addition, these hybrid monoliths tend to reduce the rapid degradation of their structure compared to a physical mixture. As a result of prolonged release of silica, which is favourable for stronger interaction with the host tissue, a thicker apatite was obtained for improved bone formation. The presence of homogeneous distribution of bioactive glass in the hybrid monolith helps to promote the precipitation of calcium and phosphate particles, which are the main inorganic composites of the bone extracellular matrix. In conclusion, an organic-inorganic hybrid was developed that significantly improved the physico-chemical properties of the composite via promoting the homogeneous distribution of phases. Also it has higher mechanical strength compared to ceramic based scaffolds. This hybrid shows biocompatibility under simulated body fluid. This polymer-bioactive glass hybrid monolith is suitable for bone regeneration and tissue engineering. KEYWORDS: Organic-inorganic hybrid, bioactive glass, PLEOF, bioactivity, tissue engineering, bone regeneration, sol-gel, biomaterial, mechanical properties, degradation behaviour.
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van, Daalen Tessa Eline. "Effect of particle size on osteoinductive capacity of strontium substituted bioactive glasses (SrBG) in vitro." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/225932/1/Tessa%20Eline_van%20Daalen_Thesis.pdf.
Повний текст джерелаАнотація:
Current clinical treatments for bone defects rely on donors or synthetic crafts, which are both associated with various complications such as limited availability, donor side morbidity and immune rejection. Thus, there is a strong need for “off the shelf” available bone implants with the ability to induce bone regeneration by host cells. Therefore, 3D printed composite bone crafts have been developed using a cost-effective bioresorbable polymer in combination with the ceramic "bioactive glass" to improve cell attachment. Here, Bioactive glass particles were reduced in size to increase surface area to hypothetically further stimulate bone tissue deposition by the host cells.
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Sanders, Lawrence Matthew. "The Synthesis & Characterization of an Antibacterial Bioactive Glass Suitable as a Bone Void Substitute." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo15447109069978.
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Meng, Decheng. "Glass-ceramic scaffolds with tailored surface topography and additional bioactive functions for bone tissue engineering." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11099.
Повний текст джерелаАнотація:
The focus of this thesis was to develop new highly porous (>90% porosity) Bioglass®-based glass-ceramic scaffolds (fabricated by the foam replica method) in order to enhance the scaffold cellular response and biological performance and to improve the scaffold suitability for future clinical applications by adding new functions. In the first part of the project, techniques were developed to introduce or engineer nanoscale topography on the surfaces of 3D scaffolds, these included: i) carbon nanotube (CNT) coating (by electrophoretic deposition), ii) polymer demixing and iii) water treatment. In the second part of the project, aiming at further improving the functionality of scaffolds, a system with drug delivery capability was developed. To this aim, multi-functional poly(3-hydroxybutryate) microsphere (PMS) coated Bioglass®-based composite scaffolds were fabricated and characterised. Tetracycline-encapsulated PMSs (< 2 μm in diameter) were made using a solid-in-oil-in-water emulsion solvent extraction/evaporation technique. The scaffolds were coated with PMSs by slurry-dipping, producing a uniform PMS coating throughout the 3D structure. By studying tetracycline release kinetics, it was found that the drug release from the coated scaffolds was slow and controlled.
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Thomson, Steven. "The effects of disorder in strongly interacting quantum systems." Thesis, University of St Andrews, 2016. http://hdl.handle.net/10023/9441.
Повний текст джерелаАнотація:
This thesis contains four studies of the effects of disorder and randomness on strongly correlated quantum phases of matter. Starting with an itinerant ferromagnet, I first use an order-by-disorder approach to show that adding quenched charged disorder to the model generates new quantum fluctuations in the vicinity of the quantum critical point which lead to the formation of a novel magnetic phase known as a helical glass. Switching to bosons, I then employ a momentum-shell renormalisation group analysis of disordered lattice gases of bosons where I show that disorder breaks ergodicity in a non-trivial way, leading to unexpected glassy freezing effects. This work was carried out in the context of ultracold atomic gases, however the same physics can be realised in dimerised quantum antiferromagnets. By mapping the antiferromagnetic model onto a hard-core lattice gas of bosons, I go on to show the importance of the non-ergodic effects to the thermodynamics of the model and find evidence for an unusual glassy phase known as a Mott glass not previously thought to exist in this model. Finally, I use a mean-field numerical approach to simulate current generation quantum gas microscopes and demonstrate the feasibility of a novel measurement scheme designed to measure the Edwards-Anderson order parameter, a quantity which describes the degree of ergodicity breaking and which has never before been experimentally measured in any strongly correlated quantum system. Together, these works show that the addition of disorder into strongly interacting quantum systems can lead to qualitatively new behaviour, triggering the formation of new phases and new physics, rather than simply leading to small quantitative changes to the physics of the clean system. They provide new insights into the underlying physics of the models and make direct connection with experimental systems which can be used to test the results presented here.
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Trégouët, Hélène. "Structure et cristallisation de verres d'oxydes simples riches en bore et en terres rares." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066032/document.
Повний текст джерелаАнотація:
Ce travail de thèse s'intéresse à la structure de verres d'oxydes simples, riches en bore et en terre rare (TR). Cette famille de verres trouve des applications dans différents domaines, de l'optique au confinement des déchets nucléaires. Ici, nous étudions la structure de verres du système le plus simple regroupant ces deux oxydes, à savoir le binaire B2O3-TR2O3. Un intérêt particulier est porté à la composition métaborate de terre rare TRB3O6, à fusion congruente. Cette étude structurale est menée au moyen de différentes techniques spectroscopiques, notamment la RMN du solide sur les noyaux 11B et 17O, l'absorption optique de Nd3+ et la diffusion des neutrons et des rayons X, associée à de la modélisation par RMC. Nous obtenons ainsi des informations sur la structure du réseau vitreux (nature des groupements structuraux, connectivité du réseau¿) et l'environnement des ions TR3+. La tendance à la cristallisation de ces verres binaires est également étudiée, par ATD, DRX et MEB. Le second volet de ces travaux concerne le système ternaire SiO2-B2O3-TR2O3. Tout d'abord, l'étendue du domaine vitrifiable est déterminée, pour nos conditions d'élaboration, puis certains verres homogènes et transparents obtenus font l'objet d'une étude structurale, de manière analogue aux verres du système binaire. Les premiers résultats concernant la tendance à la cristallisation de ces verres sont obtenusThis work focuses on the structure of boron and rare earth (RE) rich simple oxide glasses. This family of glasses finds applications in various fields, from optical materials to nuclear waste storage. Here, we study the glass structure of the simplest system combining these two oxides, namely the binary system B2O3-RE2O3. Particular attention is paid to the rare earth metaborate composition REB3O6, which exhibits a congruent melting. This structural study combines different spectroscopic techniques, such as solid state NMR on 17O and 11B nuclei, optical absorption (Nd3+) and neutron and X-rays scattering, coupled with RMC simulation. Information concerning the glassy network (nature of the structural units, network connectivity…) and the rare earth environment is gathered. The tendency towards crystallization of these binary glasses is also studied, using DTA, XRD and SEM. The second part of this work deals with the ternary system SiO2-B2O3-TR2O3. First, the extension of the domain where homogeneous and transparent glasses can be obtained (in our experimental conditions) is determined. Then, some of the glassy samples obtained undergo a structural study, analogously to the glasses of the binary system. The first results about the crystallization tendency of these glasses are obtained
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Blinder, Rémi. "Étude par Résonance Magnétique Nucléaire de nouveaux états quantiques induits sous champ magnétique : condensation de Bose-Einstein dans le composé DTN." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY030/document.
Повний текст джерелаАнотація:
Nous présentons l'étude par Résonance Magnétique Nucléaire (RMN) du composé NiCl2-4SC(NH2)2, dit DTN, constitué de chaînes de spins 1 faiblement couplées suivant les directions transverses aux chaînes. A basse température et dans un champ magnétique compris entre les deux valeurs critiques Hc1 et Hc2, ce système s'ordonne dans un état de type Condensat de Bose-Einstein (CBE). Dans cette phase, nous décrivons d'une part la détermination expérimentale du paramètre d'ordre (aimantation transverse), dont l'amplitude est bien décrite par la théorie mais dont la phase (orientation) semble fixée par un terme d'anisotropie. D'autre part nous avons étudié les fluctuations des spins électroniques à basse énergie, par la mesure du taux de relaxation RMN 1/T1, et montré que celui-ci obéit à la loi de puissance 1/T1 propto T^5. Ce comportement peut être associé au processus de 2ème ordre lié à des excitations ayant une dispersion linéaire, tels que les quasiparticules de Bogoliubov, mais sa nature n'est pas encore bien comprise. En dehors de la phase CBE, nous décrivons l'étude des fluctuations de spin dans le régime critique quantique (H ~ Hc2), dans lequel nous établissons une loi d'échelle sur 1/T1, identique à celle que l'on a observé dans un autre composé de description équivalente (échelle de spins BPCB), prouvant ainsi l'universalité de ce régime [S. Mukhopadhyay et al., Phys. Rev. Lett. 109, 177206 (2012)]. Nous avons aussi étudié les effets du désordre induit par la substitution Br-Cl dans le composé Ni(Cl1−xBrx)2-4SC(NH2)2, pour lequel des mesures par des techniques macroscopiques ont suggéré l'existence d'une phase "verre de Bose" [R. Yu et al., Nature 489, 379 (2012)]. Cette phase est caractérisée, pour différentes concentrations du dopage x = 4%, 9%, 13%, par un pic de relaxation RMN 1/T1 au champ Hp = 13.5 T, marquant un regain des fluctuations longitudinales et présentant une forte distribution des valeurs de 1/T1 - probablement due à l'aspect vitreux du système. L'indépendance du Hp en fonction de x démontre que la physique y est dominée par les effets locaux liés aux dopantsWe present a Nuclear Magnetic Resonance (NMR) study of the NiCl2-4SC(NH2)2 compound, called DTN, consisting of spin-1 chains that are weakly coupled along the transverse directions. At low temperatures and for magnetic field values between the two critical fields Hc1 and Hc2, this system enters an ordered phase of the Bose-Einstein Condensate (BEC) type. Within this phase, we first describe the experimental determination of the order parameter (transverse magnetization), the amplitude of which is found to be well described by theory while its phase (orientation) seems to be fixed by an anisotropy term. Second, by NMR relaxation rate 1/T1 we have studied the low-energy fluctuations of the electronic spins and found that they obey the power law 1/T1 ~ T 5. Such a behaviour points to a 2nd order process involving linearly dispersing excitations, such as Bogoliubov quasiparticles, but its nature is not yet well understood. Outside the BEC phase, we report a study of the spin fluctuations in the quantum critical regime (H ~ Hc2), demonstrating a scaling law on 1/T1 similar to the one that has already been observed in another equivalent compound, BPCB spin-ladder, thus proving the universality of this regime [S. Mukhopadhyay et al., Phys. Rev. Lett. 109, 177206 (2012)]. We have also studied the effect of disorder induced by the Br-Cl substitution in the compound Ni(Cl1-xBrx)2-4SC(NH2)2 (doped DTN), for which measurements using macroscopic techniques have suggested the existence of a "Bose glass" phase [R. Yu et al., Nature 489, 379 (2012)]. This phase is characterized, for all studied doping concentrations x = 4%, 9%, 13%, by a peak in the NMR relaxation rate 1/T1 at the field value Hp ~ 13.5 T, evidencing an upsurge of the longitudinal spin fluctuations, and presenting strong inhomogeneity of the 1/T1 values – probably reflecting the glassy character of the system. The observed doping-independence of Hp demonstrates that the corresponding physics is dominated by local effects due to the dopants
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Ravarian, Roya. "The Effect of Nano-Scale Interaction on the Physico-Chemical Properties of Polymer-Bioactive Glass Composites." Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/10147.
Повний текст джерелаАнотація:
Polymer-bioglass composites are favourable materials for bone repair. However, early failure in the interface of components is a common problem in physical mixtures. The aim of this project was to address the issue of phase separation by creating a hybrid material in which the polymer is bonded to bioglass. Synthetic non-biodegradable poly(methyl methacrylate) (PMMA) and natural biodegradable chitosan were selected as two types of polymers for fabrication of hybrid with bioglass. PMMA and chitosan were functionalised with appropriate silane coupling agents and covalently bonded to bioglass. The polymer and bioglass were then co-condensed during sol-gel method to form hybrid. The results of molecular scale analyses demonstrated that at optimum condition (0.1 coupling agent:MMA mol ratio, 60:40 vol% polymer:bioglass), the covalent bond between PMMA and bioglass occurred and resulted in the fabrication of hybrid. The presence of nano-scale interaction resulted in improved physico-chemical and biological properties compared with physical mixtures and bioglass. Furthermore, by manipulating process parameters such as replacing tetrahydrofuran with ethanol, increasing the temperature to 70 °C and adding sodium bicarbonate as catalyst, the gelation time was reduced and a more condensed structure was produced. The chitosan-bioglass hybrid was optimized for the volume ratio of chitosan:bioglass and coupling agent. Furthermore, a new method was developed for the creation of porosity in polymer-bioglass composites in which sodium bicarbonate was used as a gas foaming agent and a biocompatible alternative for the commonly used hydrofluoric acid during sol-gel method. In conclusion, the presence of nano-scale interaction significantly improved the physico-chemical properties of polymer-bioglass hybrids via promoting the homogenous distribution of phases. These hybrids open an avenue for the applications of polymers-bioglass composites for bone replacement and tissue engineering.
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Shah, Mohammadi Maziar. "Silicon, iron and titanium doped calcium phosphate-based glass reinforced biodegradable polyester composites as bone analogous materials." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107830.
Повний текст джерелаАнотація:
Bone defects resulting from disease or traumatic injury is a major health care problem worldwide. Tissue engineering offers an alternative approach to repair and regenerate bone through the use of a cell-scaffold construct. The scaffold should be biodegradable, biocompatible, porous with an open pore structure, and should be able to withstand the applied forces. Phosphate-based glasses (PGs) may be used as reinforcing agents in degradable composites since their degradation can be predicted and controlled through their chemistry. This doctoral dissertation describes the development and evaluation of PGs reinforced biodegradable polyesters for intended applications in bone augmentation and regeneration. This research was divided into three main objectives: 1) Investigating the composition dependent properties of novel PG formulations by doping a sodium-free calcium phosphate-based glass with SiO2, Fe2O3, and TiO2. Accordingly, (50P2O5-40CaO- xSiO2-(10-x)Fe2O3, where x = 10, 5 and 0 mol.%) and (50P2O5-40CaO-xSiO2-(10-x)TiO2 where x = 10, 7, 5, 3 and 0 mol.%) formulations were developed and characterised. SiO2 incorporation led to increased solubility, ion release, pH reduction, as well as hydrophilicity, surface energy, and surface polarity. In contrast, doping with Fe2O3 or TiO2 resulted in more durable glasses, and improved cell attachment and viability. It was hypothesised that the presence of SiO2 in the TiO2-doped formulations could up-regulate the ionic release from the PG leading to higher alkaline phosphatase activity of MC3T3-E1 cells. 2) Incorporating Si, Fe, and Ti doped PGs as fillers, either as particulates (PGPs) or fibres (PGFs), into biodegradable polyesters (polycaprolactone (PCL) and semi-crystalline and amorphous poly(lactic acid) (PLA and PDLLA)) with the aim of developing degradable bone analogous composites. It was found that PG composition and geometry dictated the weight loss, ionic release, and mechanical properties of the composites. It was also hypothesised that a potential reaction between Si and the ester bond led to the formation of carboxylate by-products resulting in a lower molecular weight polymer, thus affecting the mechanical properties of the composites. Cytocompatibility assessment with MC3T3-E1 preosteoblasts showed that these composites were cytocompatible, and cell alignment along the PGFs was observed possibly due to their favourable ionic release properties. 3) Investigating the solid-state foaming using carbon dioxide (CO2) of PDLLA-PGP composites with up to 30 vol.% filler content. While PDLLA foams resulted in 92% porosity, the porosity of the composites ranged between 79 and 91% which decreased with PGP content. In addition, a reduction in pore size was observed with increasing PGP content; however, the pore size maintained its range of 200-500 µm in all composite foams, suitable for bone tissue engineering applications. The percentage of open pores increased significantly with PGP content (up to 78% at 30 vol.% PGP). Compressive strength and modulus of PDLLA-PGP foams showed up to approximately 3-fold increase at 30 vol.% PGP content compared to neat PDLLA foams.Les défauts osseux découlant de maladies ou de traumatismes constituent un problème de santé majeur à l'échelle mondiale. Le génie tissulaire représente une autre option pour réparer et régénérer des os en faisant appel à l'échafaudage cellulaire. L'échafaudage ainsi produit devrait fournir un milieu adéquat pour la prolifération et la différentiation des ostéoblastes et entraîner, à terme, la formation d'os. L'échafaudage doit être biodégradable, biocompatible, poreux à structure ouverte, et doit pouvoir résister aux forces appliquées. Des verres à base de phosphate (PG) peuvent être utilisés comme agents de renforcement dans des composites biodégradables puisque leur dégradation peut être prédite et maîtrisée par l'intermédiaire de leurs propriétés chimiques. La présente thèse de doctorat décrit la mise au point et l'évaluation de polymères biodégradables renforcés avec des PG pour des applications d'augmentation et de régénération osseuses. La recherche présentée visait les trois principaux objectifs suivants : 1) l'étude des propriétés dépendantes de la composition de nouvelles formulations de PG par le dopage de verres de calcium à base de phosphate exempts de sodium (50P2O5-40CaO, en % molaire) avec du SiO2, du Fe2O3 et du TiO2. Ainsi, des formulations de (50P2O5-40CaO-xSiO2-(10-x)Fe2O3, où x = 10, 5 et 0 % mol) et (50P2O5-40CaO-xSiO2-(10-x)TiO2 où x = 10, 7, 5, 3 et 0 % mol) ont été mises au point et caractérisées. L'incorporation de SiO2 s'est traduite par une augmentation de la solubilité, de la libération d'ions, de la réduction du pH, ainsi que de l'hydrophilicité, de l'énergie de surface et de la polarité. En revanche, le dopage au Fe2O3 ou au TiO2 a donné des verres plus durables, en plus d'améliorer la fixation et la viabilité cellulaires. Il a été postulé que la présence de SiO2 dans les formulations dopées au TiO2 pourrait accroître la libération d'ions des PG, entraînant ainsi une activité de l'ALP accrue des cellules MC3T3-E1. 2) l'incorporation de PG dopés aux Si, Fe et Ti comme charges, sous forme de particules ou de fibres, dans des polyesters biodégradables (polycaprolactone (PCL) et acides polylactiques amorphes (PLA et PDLLA)) dans le but de mettre au point des composites dégradables analogues aux os. Il a été établi que la composition et la géométrie des PG déterminent la perte de poids, la libération d'ions, et les propriétés mécaniques des composites. Il a également été postulé qu'une réaction potentielle entre le Si et le lien ester entraînait la formation de sous-produits de carboxylate, ce qui se traduirait par un polymère de poids moléculaire réduit et aurait ainsi une incidence sur les propriétés mécaniques des composites. L'évaluation de la cytocompatibilité avec les préostéoblastes MC3T3-E1 a démontré que ces composites étaient cytocompatibles, et un alignement de cellules le long des PGF a été observé, qui pourrait être dû à leurs propriétés de libération d'ions favorables. 3) l'investigation du moussage en milieu solide avec du dioxyde de carbone (CO2) de composites de PDLLA-PGP contenant jusqu'à 30 % vol de charge. Alors que les mousses de PDLLA présentaient 92 % de porosité, la porosité des composites allait de 79 % à 91 %, diminuant avec la teneur en PGP. En outre, une réduction de la taille des pores a été observée avec l'augmentation de la teneur en PGP; la fourchette de dimensions des pores est toutefois demeurée la même (de 200 µm à 500 µm) pour toutes les mousses de composites, qui conviennent à des applications en génie tissulaire osseux. Le pourcentage de pores ouverts a augmenté significativement avec la teneur en PGP (jusqu'à 78 % à 30 % vol de PGP). La résistance à la compression et le module d'élasticité en compression des mousses PDLLA-PGP avaient à peu près triplé à 30 % vol de PGP par rapport à celles des mousses seulement constituées de PDLLA.
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De, Silva Thompson David Roshan. "Scalable production of tissue engineered microunits for bone regeneration using bioactive glass microspheres and dynamic culture conditions." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10051607/.
Повний текст джерелаАнотація:
Bone is one of the most common tissues to be transplanted, with over 2.2 million grafting procedures performed worldwide every year (Van der Stok et al., 2011). Autologous bone grafts, while considered the current gold standard, have inherent risks including limited donor tissue availability, donor site morbidity, surgical complications, and pain of procedure. Alternative approaches to treating bone tissue defects are required based on clinically effective bone graft substitutes that can be manufactured at a commercially relevant scale. Tissue engineering is an alternative strategy that uses biocompatible scaffolds in combination with cells as a bioactive implant to induce bone repair. In this thesis, microspherical bioactive glasses have been studied as a platform for scalable bone tissue engineering that has flexibility to address diverse geometric requirements with the aim of becoming a commercially available tool. Specifically, titanium-doped phosphate glass microspheres have been studied for their ability to support bone progenitor cells. Here, the microspheres (5 and 7 mol% TiO2) were assessed in their ability to support proliferation of osteoblast-like cell (MG63) and proliferation and osteogenic differentiation of human bone-marrow derived mesenchymal stem cells (hBM-MSCs) under static and dynamic agitation culture. Scalability was assessed using scalable dimensionless Froude number to scale microwell plate cultures to 125ml Erlenmeyer flask cultures using Froude as a tool to map mixing systems at both scales. MG63 and hBM-MSC proliferation was observed on the microspheres under all conditions studied as well as extracellular matrix protein secretion, confirming the biocompatibility of the materials tested. Similar growth kinetics was observed at both scales, where moderate agitation stimulated cell proliferation, but higher agitation was damaging to cells. Upregulation of key bone expression markers (COL1A1 and SPP1) was observed also at moderate orbital agitations, while on at high agitation rates this was largely absent, except for upregulation of SPP1 on the control microsphere, Synthemax. Furthermore, biomaterial resorption was observed upon differentiating mouse-derived monocytes into osteoclasts on the titanium-phosphate glass discs. In conclusion, large-scale culture using titanium-doped phosphate glass microspheres was achieved with hBM-MSCs, with the substrate effectively supporting cell proliferation and osteogenic differentiation. This research provides a stepping stone in understanding how biomaterials processed into microcarrier format can be utilised in a commercial environment to create clinically relevant quantities of tissue engineering bone.
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Hasan, Muhammad Sami. "Phosphate glass fibre reinforced composite for bone repair applications : investigation of interfacial integrity improvements via chemical treatments." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12777/.
Повний текст джерелаАнотація:
Bone repair devices made from degradable polymers, such as poly lactic acid (PLA) have limitation in terms of matching the mechanical property requirements for bone repair, both initially and for the duration of repair. For this reason the use of totally degradable phosphate glass fibre (PGF) reinforced PLA composite has proved attractive. A crucial part of the success of such implants is maintenance of interfacial integrity between the polymer matrix and reinforcement phases of the composite. It is well known that most fibre reinforced composites loose 50% or more of their strength due to interfacial integrity loss. In this study candidate chemical treatments for PGF reinforced PLA composite are being investigated in terms of their reactability, biocompatibility, effect on interfacial mechanical properties and degradation behaviour of these composites. As a crucial part of this project, phosphate based glass (PBG) formulations were devised and assessed for structural, thermal, degradation and cytocompatibility variations with varying P2O5 or Fe2O3 content. Selected formulations were drawn into fibres and tested for single fibre tensile strength. Finally, a glass formulation (P45Ca16Mg24Na11Fe4, number indicates percentage molar concentration of oxides) was selected for surface modification and composite production. Chemical surface treatments were selected on the basis of potential to react with PBG and PLA. Mode of chemical interaction between PBG and surface treatments chemicals were analysed using surface analyses techniques (FTIR and XPS). It was found that aminopropyltriethoxy silane (APS), etidronic acid (EA) and hexamethylene diisocyanate (HDI) were linked through covalent bonds, other agents making hydrogen bonds with PBG. Chemical treatments were optimised and investigated for their effect on interfacial shear strength (IFSS) between polymer/glass, wettability and degradation behaviour. Chemically treated PBG was also assessed for cytocompatibility of elution products, short–term direct contact with MG63 osteosarcoma and long term direct contact with primary human osteoblasts. All selected surface treatment chemicals except amino phosphonic acid (APA) improved the interfacial bond between PBG and PLA. However, the covalently linked agents (HDI, APS and EA) saw up to 4–fold improvement in IFSS. SPLA also improved the IFSS significantly, which was attributed to the presence of several –OH groups. There was no significant effect on degradation rate of PBG. All agents demonstrated acceptable cytocompatibility for their elution products and in direct contact. Selected chemicals (APS, EA, SPLA and HDI) were investigated further in PGF reinforced PLA composite. PGF mats (UD or non–woven), treated with surface treatment chemical were sandwich–pressed between PLA sheets. Flexural mechanical properties with degradation, water–uptake, degradation rate and cytocompatibility were tested. It was found that surface chemical treatment improved the initial flexural properties (APS, SPLA) and/or delayed the mechanical integrity loss (HDI, APS), latter was attributed to the reduced water–uptake and maintenance of relatively strong interface. Human osteoblasts were found to perform normal functions when cultured on prepared composites.
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Camargo, André Ferrari de França. "Avaliação histomorfométrica comparativa dos defeitos ósseos cavitários preenchidos com vidro bioativo e com enxerto ósseo autólogo: estudo experimental em coelhos." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/5/5140/tde-23112015-162035/.
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O tratamento das lesões ósseas cavitárias com autoenxerto ainda é considerado o padrão-ouro. Seu uso, entretanto, é limitado, devido principalmente à baixa disponibilidade e à morbidade do sítio doador. Os enxertos ósseos sintéticos são estudados com o objetivo de superar as limitações decorrentes da retirada de autoenxerto ou da disponibilidade de bancos de tecidos. O vidro bioativo é um material sintético osteoindutor, osteocondutor e antibacteriano, à base de sílica e cria um arcabouço para o crescimento ósseo. Objetivo: comparar o vidro bioativo com o autoenxerto, com relação às características histomorfométricas. Métodos: foi realizado um estudo experimental prospectivo caso-controle em animais, para comparar o vidro bioativo com o autoenxerto com relação às características histomorfométricas. Oito coelhos foram submetidos a uma cirurgia em que um defeito cavitário foi criado em ambos os fêmures proximais; de um lado, o defeito ósseo criado foi preenchido com os grânulos de vidro bioativo; do outro, o defeito ósseo foi preenchido com o autoenxerto retirado do lado contralateral. Os lados foram randomizados. Catorze dias após a cirurgia os animais foram sacrificados. Resultados: a análise histológica revelou que a neoformação óssea entre os dois grupos foi equivalente, e que a contagem de osteoblastos foi superior nos fêmures tratados com vidro bioativo. A contagem de osteócitos, por outro lado, foi menor. A semelhança na intensidade de neoformação óssea coincide com o encontrado na literatura. As diferenças de contagem celular são concordantes com o mecanismo de ação do vidro bioativo: aumento do turnover ósseo, estímulo dos osteoblastos e retardo na sua diferenciação para osteócitos. Conclusão: o vidro bioativo promove neoformação óssea semelhante ao autoenxerto neste modelo animal de defeito ósseo cavitário. Nível de evidência III, estudo caso-controleAutograft is still considered the gold standard in the treatment of cavitary bone lesions. The low availability and donor site morbidity, however, limits its use. Synthetic bone grafts have been studied in order to overcome the limitations of autograft or allograft. Bioactive glass is an osteoinductive, osteoconductive and antibacterial silica-based synthetic material. It promotes the creation of a scaffold for bone growth. Objectives: to compare bioactive glass and autograft regarding their histomorphometric characteristics. Methods: the author conducted a prospective case-control experimental study on animals, to compare the histomorphometric characteristics of bioactive glass versus autograft. Eight rabbits underwent surgery in which a cavitary defect was created in both proximal femurs. On one side, the bone defect was filled with bioactive glass granules and on the other, the defect was filled with autograft grafted from the contralateral side. The sides were randomized. Fourteen days after surgery, the animals were euthanized. Results: histologic analysis revealed that bone neoformation was equivalent among the two groups and the osteoblasts cell-count was higher in the femurs treated with bioactive glass. The osteocytes cell-count, however, was lower. The similarity in bone formation between both groups was also found in the literature. The differences in cell-count of osteocytes and osteoblasts are in accordance with the mechanism of action of the bioactive glass: increase in bone turnover, stimulation of osteoblasts and inhibition of their differentiation into osteocytes. Conclusion: bioactive glass is similar to autograft regarding bone neoformation, in this animal model of cavitary bone defects. Level of evidence III, case-control study
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Poh, Su Ping Patrina. "In vitro and in vivo assessment of bioactive composite scaffolds fabricated via additive manufacturing technology." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/75649/1/Su%20Ping%20Patrina_Poh_Thesis.pdf.
Повний текст джерелаАнотація:
Additive manufacturing (AM) technology was implemented together with new composite material comprising a synthetic materials, namely, polycaprolactone and bioactive glass with the ultimate aim of the production of an off-the-shelf composite bone scaffold product with superior bone regeneration capacity in a cost effective manner. Our studies indicated that the composite scaffolds have huge potential in promoting bone regeneration. It is our contention that owing to the fruits of such innovative efforts, the field of bone regeneration can metamorphose into a technology platform that allows clinicians worldwide to create tissue-engineered bone with economies of scale in the years to come.
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Li, Wei [Verfasser], and Aldo [Akademischer Betreuer] Boccaccini. "45S5 Bioactive Glass-Based Composite Scaffolds with Polymer Coatings for Bone Tissue Engineering Therapeutics / Wei Li. Gutachter: Aldo Boccaccini." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2015. http://d-nb.info/1076166660/34.
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Cancian, Daniela Cristina Joannitti [UNESP]. "Utilização de enxerto ósseo autógeno, biovidros e cimento de fosfato de cálcio em defeitos ósseos criados cirurgicamente em mandíbulas de macacos Cebus apella. Estudo histológico." Universidade Estadual Paulista (UNESP), 2002. http://hdl.handle.net/11449/104756.
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cancian_dcj_dr_arafo.pdf: 701669 bytes, checksum: fd8aefd8d48f51c10e40c62ed9f6db8a (MD5)A proposição deste estudo foi avaliar histologicamente a efetividade do PerioGlass, Fillerbone e Bone Source no preenchimento de cavidades ósseas cirurgicamente criadas em mandíbulas de macacos adultos jovens Cebus apella. Foram criadas duas cavidades transfixantes de 5mm de diâmetro nos ângulos mandibulares. Os defeitos ósseos foram preenchidos aleatoriamente e os grupo divididos da seguinte forma: Grupo I - cavidades preenchidas com osso cortiço-medular autógeno de tíbia; Grupo II - cavidades preenchidas com cimento de fosfato de cálcio (Bone Source); Grupo III - cavidades preenchidas com vidro bioativo (Fillerbone); Grupo IV - cavidades preenchidas com vidro bioativo (PerioGlass). Após 180 dias os animais foram sacrificados, as peças removidas e processadas para obtenção de cortes histológicos. A análise histológica dos resultados demonstrou que a utilização de enxerto ósseo autógeno permitiu reparação total do defeito ósseo; os materiais Fillerbone e PerioGlass permitiram reparo total dos defeitos com íntimo contaato dos grânulos dos materiais com o tecido ósseo neoformado; o material Boné Source não permitiu reparação do defeito ósseo ocorrendo preenchimento do defeito por tecido conjuntivo fibroso e foi em grande parte reabsorvido.
The present study evaluated histological results of filling with autogenous bone, PerioGlass, Fillerbone and Bone Source in bone cavities surgically created in mandible of Cebus apella Monkeys. The surgical cavities were prepared through both mandibular cortices, with a diameter of 5mm, inthe mandibular angle region. The cavities were randomized filled and the groups divided according to the material employed as follow: Group I - Filled with tibial autogenous corticocancellous bone; Group II - Filled with calcium phosphate cement (Bone Source); Group III - Filled with bioactive glass (Fillerbone); Group IV - Filled with bioactive glass (PerioGlass). After 180 days the animals were sacrificed and the specimens followed routine laboratory procedures for hematoxilin/eosin staining and histological evaluation. The histological analysis showed that the autogenous bone allowed total repair of the bone defects; Fillerbone and PerioGlass allowed total repair of the defects with intimate contact of the remaining granules and newly formed bone; Bone Source did not allow bone formation with filling of the defects by connective fibrous tissue and the material was almost totally ressorbed.