Acrylic bone cements are used in dentistry and orthopedic surgery to fix prosthetic devices into the bone. Bone cements transfer and distribute the applied load and increase the load-carrying capacity of the prosthesis/cement/bone system with the help of mechanical bonding between the device and the bone. In spite of all their advantages, bone cements have several drawbacks such as insufficient mechanical properties, high exothermic polymerization temperature, release of monomer to the environmental tissue and loosening of implant. Studies are being carried out to improve bone cement formulations with low curing temperature, good mechanical properties and good biocompatibility. In this study, bone cements with different compositions were prepared by using poly(methyl methacrylate) (PMMA) microspheres, barium sulphate (BaSO4) radiopaque agent, inorganic hydroxyapatite (HA) particles and 1-dodecyl mercaptan (DDM) chain stopping agent. Mechanical and thermal properties of the prepared bone cements were examined. When 8% hydroxyapatite was added into the formulation, both tensile and compressive strengths were increased and curing temperature was decreased. Addition of 13% BaSO4 caused 0.98% and 10.29% decrease in tensile and compressive strength values, respectively. Addition of 1%, 2% and 3% DDM, relative to the amount of methyl methacrylate monomer, decreased the maximum temperature from 101.78&deg / C to 91.80&deg / C, 78.38&deg / C and 71.35&deg / C, respectively. All compositions of the prepared bone cements fulfilled the minimum compressive strength (70 MPa) requirement and the minimum curing temperature was obtained as 71.35&deg / C. In order to have optimum desired properties, further studies to improve biocompatibility, mechanical and thermal properties of bone cements are needed.

No description available.

Bone response is one of the key determining factors in the overall success of biomaterials intended for bone regeneration and osseointegration. Understanding the formation of bone at an implant surface may lead to the improved design of biomaterials for the future. However, due to the inhomogeneity of bone tissue at an interface, two-dimensional images often lack detail on the interfacial complexity. Furthermore, the increasing use of nanotechnology in the design and production of biomaterials demands characterization techniques on a similar nano length scale. While current analysis methods, such as X-ray tomography, transmission electron microscopy, focused ion beam microscopy and scanning electron microscopy, provide a basis for analysing biomaterials and biointerfaces, they are incapable of doing so with both nanometre resolution and three-dimensional clarity. In contrast, electron tomography may be used to characterize the three-dimensional structure of biomaterials and their interfaces to bone with nanometre resolution. In this work, hydroxyapatite scaffolds, and laser-modified titanium and Ti6Al4V implants were studied in contact with human or rabbit bone. Z-contrast electron tomography revealed that the orientation of collagen in bone apposing hydroxyapatite, titanium and Ti6Al4V implants is consistently parallel to the implant surface, where the bioactive layer that precipitates on HA is oriented perpendicular to the implant surface. With this method, complete three-dimensional nanoscale osseointegration of titanium-based implants was also established. The extension of this technique from interfacial analyses to the design of biomaterials provided an understanding of the pore structure of mesoporous titania. In further investigations, the open three-dimensional pore network, as revealed by electron tomography, showed promise as a coating that improves implant osseointegration and enables site-specific drug-delivery from an implant surface. In summary, it was demonstrated that two-dimensional characterization techniques were insufficient for the investigation of nanostructured biomaterials, as well as their interfaces to bone. Visualizing biointerfaces and biomaterials with nanometre precision in three-dimensions can expose new fundamental information on materials properties and bone response, enabling better design of biomaterials for the future.

Thesis (Ph. D.)--University of Alabama at Birmingham, 1997. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.Sc.)--Aberdeen University, 2008. / Title from web page (viewed on March 9, 2009). Includes bibliographical references.

Thesis (Ph. D.)--University of Alabama at Birmingham, 1997. / Includes bibliographical references.

Το αντικείμενο της παρούσας μεταπτυχιακής διατριβής ειδίκευσης ήταν η μελέτη των φυσικοχημικών και μηχανικών ιδιοτήτων παθολογικά αλλοιωμένων ανθρώπινων μηνίσκων. Οι μηνίσκοι είναι ινοχόνδρινοι μηνοειδείς δίσκοι που παρεμβάλλονται μεταξύ των αρθρικών επιφανειών του μηριαίου κονδύλου και της κνημιαίας γλύνης. Αποτελούνται ως επί το πλείστον από ίνες κολλαγόνου και χονδροκύταρα. Περιέχουν ακόμα γλυκοσαμινογλυκάνες, ελλαστίνη και DNA. Συμβάλλουν καθοριστικά στη σωστή λειτουργία της άρθρωσης καθώς είναι επιφορτισμένοι με λειτουργίες, όπως η προστασία των αρθρικών επιφανειών από τη φθορά, η λίπανση και η σταθεροποίηση της άρθρωσης. Η σημαντικότερη ίσως μεταβολική νόσος των μηνίσκων είναι η χονδρασβεστίωση (chondrocalcinosis) κατά την οποία παρατηρείται ανάπτυξη ανόργανων αλάτων στην επιφάνεια ή/και στο σώμα του ιστού. Για τη μελέτη των ιδιοτήτων των παθολογικά αλλοιωμένων ανθρώπινων μηνίσκων χρησιμοποιήθηκαν τεχνικές μηχανικής και φυσικοχημικής ανάλυσης. Με Δυναμική Μηχανική Ανάλυση επιχειρήθηκε να αξιολογηθεί η επίδραση των διαφόρων τύπων παθολογικών αλλοιώσεων στις δυναμικές μηχανικές ιδιότητες των ιστών. Οι ασβεστοποιημένοι ιστοί και οι εναποθέσεις τους μελετήθηκαν με φασματοσκοπικές τεχνικές RAMAN, FT-RAMAN, FT-IR καθώς επίσης και με απεικονιστικές τεχνικές οπτικής μικροσκοπίας, σαρωτικής μικροσκοπίας ηλεκτρονίων (SEM) και μικροσκοπίας ατομικής δύναμης (AFM). Επιπλέον, για πρώτη φορά έγινε διασύγκριση της ικανότητας τριών διαφορετικών διατάξεων RAMAN (FT-RAMAN: 1064 nm, Dispersion RAMAN: 633 nm και Dispersion RAMAN: 325 nm) να εντοπίσουν την παρουσία εναποθέσεων στους ιστούς. Στην παρούσα μελέτη εξετάστηκαν 63 μηνισκικά μοσχεύματα από οστεοαρθριτικούς ασθενείς οι οποίοι υποβλήθηκαν σε ολική αρθροπλαστική γόνατος στο Περιφερειακό Πανεπιστημιακό Νοσοκομείο Πατρών. Τα μοσχεύματα αυτά εξετάστηκαν από ιστοπαθολόγο και διαγνώστηκαν οι παθολογικές αλλοιώσεις που έφερα καθένας από αυτούς. Με βάση τα ιστοπαθολογικά αποτελέσματα έγινε κατηγοριοποίηση των δοκιμίων και συσχέτιση των αποτελεσμάτων αυτών με τα αποτελέσματα των προαναφερθέντων τεχνικών. Από τα αποτελέσματα της δυναμικής μηχανικής ανάλυσης φάνηκαν μικρές αλλά όχι στατιστικά σημαντικές διαφοροποιήσεις μεταξύ ασβεστοποιημένων μηνίσκων και μηνίσκων που παρουσίαζαν μυξωματοειδή εκφυλισμό και κύστες (σύμφωνα με τα αποτελέσματα της ιστοπαθολογικής εξέτασης). Τα αποτελέσματα της περιθλασιμετρίας ακτίνων Χ των ασβεστοποιημένων ιστών έδειξαν παρουσία μείγματος τρικλινούς και μονοκλινούς διένυδρου πυροφωσφορικού ασβεστίου (CPPD) υψηλής κρυσταλλικότητας καθώς και μικροκρυσταλλικές εναποθέσεις απατιτικής σύστασης (HAP). Οι τεχνικές μικροσκοποίας (οπτική, SEM και AFM) επιβεβαίωσαν τον παραπάνω ισχυρισμό αποκαλύπτοντας το χαρακτηριστικό τρόπο ανάπτυξης κάθε τύπου εναπόθεσης. Τα αποτελέσματα της φασματοσκοπικής ανάλυσης με χρήση των τεχνικών RAMAN – FT-RAMAN – και FT-IR έδειξαν την παρουσία επίσης χαρακτηριστικών κορυφών του CPPD και του HAP. Οι εναποθέσεις από CPPD ανιχνεύθηκαν στο 82.6 % των ασβεστοποιημένων δειγμάτων (19 στα 23) ενώ από απατίτη στο 17.4% (4 στα 23) Aναφορικά με τα RAMAN, επισημαίνεται ότι ανεξάρτητα από το μήκος κύματος που χρησιμοποιήθηκε και παρά την ισχυρή μπάντα φθορισμού που επεδείκνυαν τα φάσματα, οι χαρακτηριστικές κορυφές των εναποθέσεων ήταν εμφανείς. / The aim of the present master thesis study was the physicochemical and biomechanical characterization of pathological human menisci. Menisci are semilunar shaped fibrocartilaginous tissues that lie between the femoral condyle and tibia plateau. They mainly consist of collagen fibers and chondrocytes. Additionally glycosaminoglycans, elastin and DNA are present in the tissue. Menisci play an important role in the good function of human knee joint by distributing the applied loads, contributing to the joint’s stability and lubricating the joint’s area. The most common metabolic meniscal lesion is the chondrocalcinosis where inorganic phases of calcium or sodium salts are deposited in/on the tissue. Pathologically altered human menisci were studied by mechanical and physicochemical analysis techniques. Dynamic Mechanical Analysis was used to investigate the effects of degeneration lesions on the dynamic mechanical properties of the tissue. Calcified tissues and the corresponding encrustations were studied by spectroscopic techniques such as RAMAN, FT-RAMAN, FT-IR as well as imaging techniques such as optical microscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM). Moreover, for the first time a comparison of the ability of three different RAMAN setups (FT-RAMAN: 1064 nm, Dispersion RAMAN: 633 nm and Dispersion RAMAN:325 nm) to detect calcification on the tissues was performed. The clinical sample comprised of 63 menisci with histopathologicaly confirmed alterations that were surgically extracted from osteoarthritic patients due to total knee arthroplasty in the University Hospital of Patras. Samples were classified according to the histopathological evaluation and a correlation of histopathological with mechanical or spectroscopic findings was attempted. Dynamic mechanical analysis results showed small but no statistically significant difference between the group of calcified and the group of mucoid and cystic degenerated tissues (as determined after histopathological examination) X-ray diffraction analysis of the menisci encrustations revealed highly crystallized depositions of triclinic and monoclinic Calcium Pyrophosphate Dihydrate (CPPD) and some samples with poorly crystallized apatitic depositions (HAP). Microscopic techniques (optical, SEM and AFM) confirmed the presence of CPPD and HAP and in addition revealed information regarding their growth mechanism.The results of spectroscopical analysis using RAMAN – FT-RAMAN and FT-IR showed also the characteristic peaks of the inorganic phase (CPPD or HAP) presented in/on the tissue. CPPD encrustations were detected in 82.6 % (19 of 23) of the calcified samples while apatite in 17.4 % (4 of 23). Moreover, it is notable that all RAMAN setups showed the characteristic peaks of CPPD and HAP regardless of the excitation source and the strong fluorescence band.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-18T17:04:56Z No. of bitstreams: 1 LEONARDO SARMENTO MEIRA GADELHA - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1520712 bytes, checksum: 8f477b0a9d2403096c41524ecdb9cda1 (MD5) / Made available in DSpace on 2018-04-18T17:04:56Z (GMT). No. of bitstreams: 1 LEONARDO SARMENTO MEIRA GADELHA - DISSERTAÇÃO PPG-CEMat 2014..pdf: 1520712 bytes, checksum: 8f477b0a9d2403096c41524ecdb9cda1 (MD5) Previous issue date: 2014-08-07 / As cerâmicas são materiais sólidos não metálicos inorgânicos. Por apresentar natureza refratária, dureza e inércia química frente às condições adversas encontradas na cavidade bucal, as cerâmicas foram introduzidas como material odontológico devido a sua biocompatibilidade, estabilidade de cor em longo prazo, resistência ao desgaste e a sua capacidade de serem conformadas em formas precisas. Destacam-se entre as cerâmicas utilizadas nos implantes ortodônticos a zircônia e a hidroxiapatita por possuirem propriedades mecânicas muito semelhantes à de metais e cor semelhante à cor do dente. Baseado nestas informações este trabalho tem como objetivo estudar as propriedades de blocos sinterizados de Zircônia/Hidroxiapatita como perspectiva de aplicação como biomaterial. Verificou-se a possibilidade de obter blocos Zircônia/Hidroxiapatita, controlando suas características morfológicas e cristalinas pela adição de hidroxiapatita, com potencial para ser aplicado como biomaterial. / Ceramics are inorganic non-metallic solids. By presenting refractory nature, hardness and chemical inertness face of the adverse conditions found in the oral cavity, ceramics were introduced as dental material due to its biocompatibility, color stability for long-term wear resistance and its ability to be formed into precise shapes. Prominent among the ceramics used in orthodontic zirconia implants and hydroxyapatite to possess mechanical properties very similar to the metal and color similar to the color of the tooth. Based on this information this work was to study the properties of sintered blocks of zirconia / hydroxyapatite as application perspective as a biomaterial. It has been found the possibility to obtain zirconia / hydroxyapatite blocks, controlling their morphological and crystalline characteristics by adding hydroxyapatite, with a potential to be applied as a biomaterial.

Fabrication of scaffold is the key for bone tissue engineering, which is commonly regarded as the most potential route for repairing bone defects. Previously, porous ceramic scaffolds were fabricated through a variety of traditional methods, like moulding and casting, but most of them cannot produce customised tissue-engineered scaffolds. Therefore, 3D printing methods are gaining more attention and are currently being explored and developed to make scaffolds with acceptable biocompatibility. With the considerable development of bone tissue engineering, the bioactivity of scaffolds is becoming increasingly demanded, which leads to new methods and techniques to produce highly biomimetic bone scaffolds. In this study, a new fabrication process to optimise the structures of scaffolds was developed, and intensive researches were performed on the porous scaffolds to confirm their advantages in biological performance. Specifically, by combination of motor assisted extrusion deposition and gas-foaming (graphite as the porogen) technique, hierarchically porous scaffolds with improved microstructures, i.e. multi-scaled pores from nanometre to millimetre (nm-μm-mm), was successfully developed. In this thesis, the optimal content of porogen for scaffolds was studied in terms of compressive strength and in-rod porosities. The most concerned physicochemical properties of scaffolds were carefully examined and the results revealed that such scaffolds exhibit excellent physicochemical properties owing to hierarchically porous structures. Due to additional in-rod micropores and increased specific surface area, along with better hydrophilicity, hierarchically porous scaffolds exerted complete superiority in biological activity, including promoting cellular proliferation of osteoblasts, adhesion and spreading status, as well as the ability to induce cellular differentiation.

Proposição: avaliar histológica e bioquimicamente o efeito de enxerto ósseo autógeno e implante de hidroxiapatita (HA) sintética (HAP 91®), sob influência de campo magnético estático, no reparo ósseo na calvária de ratos. Materiais e métodos: utilizaram-se defeitos críticos de 5 mm realizados na calvária de 60 ratos Wistar. Os animais foram submetidos a quatro diferentes intervenções: enxerto ósseo autógeno ou implante de HA, com e sem a presença de campo magnético estático, sepultado, com intensidade entre 40 e 70 G. Foi realizada análise histológica histométrica e descritiva dos defeitos ósseos em 15, 30 e 60 dias pós-operatórios. Realizou-se análise da atividade sistêmica da enzima fosfatase alcalina nos mesmos tempos operatórios. Para controle bioquímico utilizaram-se cinco animais (Naive). Resultados: o reparo ósseo foi mais acelerado no grupo de enxerto autógeno sob influência de campo magnetico do que no mesmo grupo sem influência magnética. O enxerto ósseo autógeno demonstrou reparo ósseo superior ao implante de HA. A atividade da enzima fosfatase alcalina teve sua maior expressividade em 30 dias pós-operatórios. Neste mesmo tempo operatório, os grupos com aplicação de campo magnético apresentaram atividade enzimática inferior aos grupos sem tal influência. Conclusões: o implante de HA demonstrou ser inferior ao enxerto ósseo autógeno no reparo ósseo. O campo magnético estático não causou influência sobre o reparo ósseo. A enzima fosfatase alcalina teve sua atividade diminuída em 30 dias pós-operatórios pela influência do campo magnético estático. / Purpose: to evaluate histologically and biochemically the effect of autogenous bone graft and synthetic hidroxiapatite (HA) implant (HAP 91®), under static magnetic field influence, on bone healing in rat calvaria. Materials e methods: 5-mm critical-size defects were created in each calvarium of 60 Wistar rats. They were submitted into four different interventions: autogenous bone graft or HA implant, with or without static magnetic field influence with intensity ranging from 40 to 70 G. Histometric and descriptive analysis of the bone defects were performed in 15, 30 and 60 days after surgery. At the same times, the systemic activity of alkalin phosphatase was measured. Five animals (Naive) were used as biochemical control. Results: bone healing was faster in the autogenous bone graft group under magnetic field stimulation than in the same group without the magnetic influence. The autogenous bone graft showed better results for bone healing than the HA implant. Alkalin phosphatase activity had its higher expression in 30 days after surgery. At this time the groups under magnetic stimulation had lower alkalin phosphatase activity than the groups without magnetic field influence. Conclusions: the HA implant showed worse bone healing than the autogenous bone graft. The static magnetic field did not cause any influence on bone healing. alkalin phosphatase had its activity lowered in 30 days after surgery in the groups under magnetic field influence.