5 research outputs found

    Experimental Studies on Non-Metallic Composite Bone Implants With a Special Reference to Staphylococcal Biofilm Infection

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    Non-metallic implants made of bioresorbable or biostable synthetic polymers are attractive options in many surgical procedures, ranging from bioresorbable suture anchors of arthroscopic surgery to reconstructive skull implants made of biostable fiber-reinforced composites. Among other benefits, non-metallic implants produce less interference in imaging. Bioresorbable polymer implants may be true multifunctional, serving as osteoconductive scaffolds and as matrices for simultaneous delivery of bone enhancement agents. As a major advantage for loading conditions, mechanical properties of biostable fiber-reinforced composites can be matched with those of the bone. Unsolved problems of these biomaterials are related to the risk of staphylococcal biofilm infections and to the low osteoconductivity of contemporary bioresorbable composite implants. This thesis was focused on the research and development of a multifunctional implant model with enhanced osteoconductivity and low susceptibility to infection. In addition, the experimental models for assessment, diagnostics and prophylaxis of biomaterial-related infections were established. The first experiment (Study I) established an in vitro method for simultaneous evaluation of calcium phosphate and biofilm formation on bisphenol-Aglycidyldimethacrylate and triethylenglycoldimethacrylate (BisGMA-TEGDMA) thermosets with different content of bioactive glass 45S5. The second experiment (Study II) showed no significant difference in osteointegration of nanostructured and microsized polylactide-co-glycolide/β-tricalcium phosphate (PLGA /β-TCP) composites in a minipig model. The third experiment (Study III) demonstrated that positron emission tomography (PET) imaging with the novel 68Ga labelled 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) CD33 related sialic-acid immunoglobulin like lectins (Siglec-9) tracer was able to detect inflammatory response to S. epidermidis and S. aureus peri-implant infections in an intraosseous polytetrafluoroethylene catheter model. In the fourth experiment (Study IV), BisGMATEGDMA thermosets coated with lactose-modified chitosan (Chitlac) and silver nanoparticles exhibited antibacterial activity against S. aureus and P. aeruginosa strains in an in vitro biofilm model and showed in vivo biocompatibility in a minipig model. In the last experiment (Study V), a selective androgen modulator (SARM) released from a poly(lactide)-co-ε-caprolactone (PLCL) polymer matrix failed to produce a dose-dependent enhancement of peri-implant osteogenesis in a bone marrow ablation model.Polymeereistä valmistettuihin ei-metallisiin komposiittiluuimplantteihin liittyvä kokeellinen tutkimus erityisesti liittyen biofilmiä muodostavaan stafylokokki -infektioon Synteettisistä polymeereistä valmistetut biohajoavat ja biostabiilit implantit ovat vaihtoehtoja metallisille implanteille useissa kirurgisissa toimenpiteissä. Biohajoavia implantteja voidaan käyttää tähystyskirurgiassa ommelankkureina tai biostabiileita kuitulujitteisia implantteja kalloluun korjauksessa. Polymeereistä valmistetut implantit häiritsevät kuvantamistutkimuksia vähemmän kuin tavanomaiset metalliset implantit. Biohajoavat polymeerit voivat myös toimia luun kasvua ohjaavana rakenteena ja samalla vapauttaa paikallisesti luun kasvua edistävää lääkettä. Myös biostabiileista kuitulujitteisista polymeereistä voidaan valmistaa kuormaa kantavia implantteja, joiden mekaanisia ominaisuuksia on säädelty luun kanssa samankaltaisiksi. Biomateriaalien kliiniseen käyttöön liittyy aina jonkinasteinen infektioriski. Vaikeimmin hoidettavat infektiot liittyvät bakteerikantojen kykyyn kiinnittyä implanttien pinnalle (biofilmin muodostuminen). Myös biohajoavien implanttien käytössä riittämätön uudisluun muodostuminen on todettu yhdeksi ongelmaksi. Tässä väitöskirjatutkimuksessa keskityttiin multifunktionaalisen implanttimallin tutkimukseen, jossa pyrkimyksenä oli saada parannettua implantin osteokonduktiivisuutta ja alentaa infektioalttiutta. Ensimmäisessä osatyössä kehitettiin menetelmä, jolla voidaan seurata biofilmin ja hydroksiapatiitin muodostumista bioaktiivisen lasin 45S5 sekä bisfenoli-Aglysidyylidimetakrylaatin ja trietyleeniglykolidimetakrylaatin (BisGMA-TEGDMA) seoksesta valmistetun yhdistelmämateriaalin pinnalla. Toisessa osatyössä todettiin, että luun muodostusta edistävän β-trikalsiumfosfaatin (β-TCP) partikkelikoolla (nano versus mikro) ei ollut merkittävää vaikutusta biohajoavan yhdistelmämateriaalin (valmistettu polylaktidiglysidyylin seospolymeeristä ja β-TCP:sta) kiinnittymiseen luuhun. Kolmannessa osatyössä todettiin, että positroniemissiotomografian (PET) uusi Siglec-9 -niminen kuvausmerkkiaine pystyy tunnistamaan stafylokokkien (S. epidermidis ja S. aureus kannat) aiheuttamat implantti-infektiot. Siglec-9 valmistettiin 68Ga-isotoopilla leimattuun 1,4,7,10-tetra-atsasyklododekaani-1,4,7,10- tetraetikkahappoon (DOTA). Implantti oli luun sisäinen katetrityyppinen ratkaisu, ja se oli valmistettu polytetrafluorietyleenistä (PTFE). Neljännessä osatyössä osoitettiin, että nanokoon hopeapartikkeleita sisältävä laktoosi-modifioitu kitosaani (Chitlac) -pinnoite estää bakteerien kasvua (S. aureus ja P. aeruginosa kannat) biostabiilin BisGMA-TEGDMA:sta valmistetun implantin pinnalla. Pinnoitteella ei ollut haitallisia vaikutuksia implantin kiinnittymiseen luuhun. Viimeisessä osatyössä todettiin, että biohajoavista polylaktidikaprolaktonin (PLCL) seospolymeerimatriisista valmistetusta implantista vapautuva anabolinen lääkeaine (selektiivinen androgeenimodulaattori, SARM) ei edistänyt uudisluun muodostumista paikallisesti luuydinablaatiomallissa.Siirretty Doriast

    The use of an induced muscle flap to reconstruct mandibular defects

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    The treatment of challenging large osseous defects presents a formidable problem for orthopaedic and maxillofacial surgeons. Autogenous bone grafting is the present method of choice to replace the lost tissue, but supplies of autologous bone are limited and harvesting of the graft is associated with donor site morbidity. Artificial biomaterials hold much promise, but do not, by themselves, supply the osteoprogenitor cells needed for bone formation. Moreover, there are often issues with resorption of the scaffold used in the biomaterial, as well as limited vascularity. This study investigates the novel application of a composite bone mineral (Cerament TM Spine Support) as an injectable bone cement loaded with cytokines and seeded with induced mesenchymal stromal cells, for maxillofacial reconstruction in rabbits. This study aims to test the feasibility of converting a pedicled muscle flap into bone to reconstruct a critical-size defect in the mandible as the above three components would theoretically have the combined effect of osteoconduction, osteoinduction and osteogenesis. The study included a comprehensive assessment of bone regeneration using plain radiography, Cone Beam computerized Tomography (CBCT), Micro-Computerized Tomography (micro-CT) and histology. Results at 3 months following surgery showed areas of bone formation and remnants of residual cement throughout the muscle and connective tissue in the surgical defect. Data analysis showed that complete bone integration or incorporation for the reconstruction of the surgical defect was not achieved. However, the regenerated bone displayed a high degree of remodeling with an intricate network of woven bone trabeculae within the cement. The bone was thicker in the bucco-lingual direction and exhibited more red and fatty marrow spaces compared to the contralateral (non-operated) side. The study confirmed that bone formation within a muscle flap in the maxillofacial region is possible. However, a wide range of variation in the patterns of bone formation was seen among the samples. The findings demonstrated the remarkable potential for the use of autologous muscle flaps as bioreactors for injectable scaffoldings, BMP, rMSCs to facilitate the reconstruction of maxillofacial bony defects

    Feasibility of monitoring bone remodelling around loaded percutaneous tibial implants in guinea pigs by in vivo microfocus computed tomography

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    Guinea pigs were selected as an animal model for studying bone remodelling around loaded percutaneous implants. The feasibility of monitoring bone remodelling in vivo by microfocus computed tomography was assessed experimentally. A microfocus computed tomography (μCT) protocol was developed to minimise the side effects (i.e. radionecrosis) while maintaining sufficient image quality to allow segmentation of the μCT slices for subsequent processing into finite element models. © 2001 Elsevier Science B.V.status: publishe

    Feasibility of monitoring bone remodelling around loaded percutaneous tibial implants in guinea pigs by in vivo microfocus computed tomography (µCT)

    No full text
    Guinea pigs were selected as an animal model for studying bone remodelling around loaded percutaneous implants. The feasibility of monitoring bone remodelling in vivo by microfocus computed tomography was assessed experimentally. A microfocus computed tomography (mCT) protocol was developed to minimise the side effects (i.e. radionecrosis) while maintaining sufficient image quality to allow segmentation of the mCT slices for subsequent processing into finite element models. (c) 2001 Elsevier Science B.V. All rights reserved.status: publishe
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