Fiber-reinforced Composite as Oral Implant Material. Experimental studies of glass fiber and bioactive glass in vitro and in vivo

Fiber-reinforced composite as oral implant material: Experimental studies of glass fiber and bioactive glass in vitro and in vivo Department of Prosthetic Dentistry and Biomaterials Science, Institute of Dentistry, University of Turku, Turku, Finland 2008. Biocompatibility and mechanical properties are important variables that need to be determined when new materials are considered for medical implants. Special emphasis was placed on these characteristics in the present work, which aimed to investigate the potential of fiber-reinforced composite (FRC) material as an oral implant. Furthermore, the purpose of this study was to explore the effect of bioactive glass (BAG) on osseointegration of FRC implants. The biocompatibility and mechanical properties of FRC implants were studied both in vitro and in vivo. The mechanical properties of the bulk FRC implant were tested with a cantilever bending test, torsional test and push-out test. The biocompatibility was first evaluated with osteoblast cells cultured on FRC substrates. Bone bonding was determined with the mechanical push-out test and histological as well as histomorplanimetric evaluation. Implant surface was characterized with SEM and EDS analysis. The results of these studies showed that FRC implants can withstand the static load values comparably to titanium. Threaded FRC implants had significantly higher push-out strength than the threaded titanium implants. Cell culture study revealed no cytotoxic effect of FRC materials on the osteoblast-like-cells. Addition of BAG particles enhanced cell proliferation and mineralization of the FRC substrates The in vivo study showed that FRC implants can withstand static loading until failure without fracture. The results also suggest that the FRC implant is biocompatible in bone. The biological behavior of FRC was comparable to that of titanium after 4 and 12 weeks of implantation. Furthermore, addition of BAG to FRC implant increases peri-implant osteogenesis and bone maturation.

Effect of milk coagulation properties of herd bulk milks on yield and composition of Emmental cheese

Selostus: Tankkimaidon juoksettumisominaisuuksien vaikutus Emmental-juuston määrään ja koostumukseen

Variation in soil nutrient concentrations and bulk density within peatland forest sites

Abstract

Materiaalitietokanta prosessilaitetoimituksen laitevalintojen tukena

In this master's thesis, material characteristics which includes material database will be developed, through which will be managed process device deliveries device selections. The analysed bulk materials exact values serve as basic data when choosing glass- and dried product industry raw material equipment solutions. In this study, the material database function structure will be divided into classified bulk materials characteristics and process device guidelines and planning which they are based on. In order to achieve the best possible advantage in use of the material database, the raw material handling with the process equipment has to be controlled with the help of database bulk material information. With the help of material database, the personnel of the company will find the needed material and device information to implement the processes. The structure of the database enables adding of information, and hence the database will be always kept updated. The material database uses free PhpOpenDatabase software programme, which adapts itself flexibly with the software and requirements of the company. The material frame and considered features of the material database were determined by the requirements of the company's device technology. National and international classifications were used as help. The collected material information was analysed and the correspondence between internal study results and found classifications were determined. As presented before, on the grounds of chosen and specified material features, also the controllability of device selecting and solutions was improved with device-specific screening and planning guidelines. As material frame of the material database was chosen ANSI/CEMA Standard 550. Its almost 1000 bulk materials form an extensive database frame. Over 600 of these raw materials have been determined according to classification. However, the most important ones are the materials of glass- and dried material plants, which consist of the last part of material frame. The analysis will be sustained and material information will be completed primarily of material part with test run in one's own material laboratory.

Design of a Condition Monitoring System for a Glass Wool Production Line

Työn tarkoituksena oli suunnitella kunnonvalvontajärjestelmä kahdelle lasivillan tuotantolinjalle. Suunnitteluprosessin lisäksi työssä on esitelty erilaisia kunnonvalvontamenetelmiä. Työn alussa on kerrottu erilaisista kunnonvalvontamenetelmistä, joilla voidaan seurata erilaisten laitteiden ja koneiden toimintakuntoa.Erityisesti työssä on tarkasteltu teollisuudessa yleistyviä kunnonvalvonnan värähtelymittauksia. Työssä suunniteltu kunnonvalvontajärjestelmä perustuu viiteen eri menetelmään, jotka ovat värähtelymittaus, lämpötilanmittaus lämpökameralla, lämpötilanmittaus kannettavalla mittarilla, kuuntelu elektronisella stetoskoopilla ja pyörivien osien kunnontarkkailu stroboskoopilla. Kunnonvalvontajärjestelmän suunnittelu on tehty useassa eri vaiheessa. Ensin työssä on kartoitettu tuotannon kannalta tärkeimmät laitteet ja niiden mahdolliset vikaantumistavat. Seuraavaksi on valittu sopivat kunnonvalvontamenetelmät ja tehty mittaussuunnitelma, jossa on esitetty eri laitteille suoritettavat mittaukset ja mittausten aikavälit.Lopuksi työssä on esitelty muutama esimerkkitapaus kunnonvalvontamenetelmien käytöstä sekä kerrottu mahdollisista tulevaisuuden kehitysmahdollisuuksista.

Terässiilojen mitoitusohjelman kehittäminen

Siiloja käytetään jauhemaisten ja rakeisten aineiden varastointiin ja annosteluun maataloudessa sekä mm. lasi-, laasti- ja tasoiteteollisuudessa. Tällaiset laitokset toimitetaan usein kokonaistoimituksina, joissa tavanomaisten teräsrakenteiden kustannusvaikutus voi olla jopa 30 % koko toimituksen arvosta. Niinpä osaltaan siilojen tehokkaalla mitoituksella ja erilaisiarakenneratkaisuja vertailemalla voidaan alentaa toimitusten kokonaiskustannuksia. Tässä diplomityössä perehdyttiin siilojen rakenteisiin ja niiden lujuustekniseen mitoitukseen etenkin tuentaratkaisujen osalta. Mitoituksen osalta työssä perehdyttiin pääasiassa uusiin Eurooppalaisiin standardeihin SFS-EN 1991-4 ja SFS-EN 1993-4-1. Niiden mukaan määritetään mitoituskuormat sekä tehdään lujuustekninen mitoitus. Työn tuloksena laadittiin Microsoft Excel -pohjainen mitoitusohjelma, jolla voidaan nopeasti mitoittaa siilojen olennaisimmat teräsrakenteet. Ohjelmalla voidaan määrittää mitoitus koskien siilon lieriön ja kartion seinämiä sekä tuentaratkaisuja. Ohjelma nopeuttaa erityisesti tarjousvaiheen suunnittelua ja antaa pohjan varsinaiselle siilojen yksityiskohtaiselle mitoittamiselle ja suunnittelulle.

Non-resorbable glass fibre-reinforced composite with porous surface as bone substitute material: Experimental studies in vitro and in vivo focused on bone-implant interface

The development of load-bearing osseous implant with desired mechanical and surface properties in order to promote incorporation with bone and to eliminate risk of bone resorption and implant failure is a very challenging task. Bone formation and resoption processes depend on the mechanical environment. Certain stress/strain conditions are required to promote new bone growth and to prevent bone mass loss. Conventional metallic implants with high stiffness carry most of the load and the surrounding bone becomes virtually unloaded and inactive. Fibre-reinforced composites offer an interesting alternative to metallic implants, because their mechanical properties can be tailored to be equal to those of bone, by the careful selection of matrix polymer, type of fibres, fibre volume fraction, orientation and length. Successful load transfer at bone-implant interface requires proper fixation between the bone and implant. One promising method to promote fixation is to prepare implants with porous surface. Bone ingrowth into porous surface structure stabilises the system and improves clinical success of the implant. The experimental part of this work was focused on polymethyl methacrylate (PMMA) -based composites with dense load-bearing core and porous surface. Three-dimensionally randomly orientated chopped glass fibres were used to reinforce the composite. A method to fabricate those composites was developed by a solvent treatment technique and some characterisations concerning the functionality of the surface structure were made in vitro and in vivo. Scanning electron microscope observations revealed that the pore size and interconnective porous architecture of the surface layer of the fibre-reinforced composite (FRC) could be optimal for bone ingrowth. Microhardness measurements showed that the solvent treatment did not have an effect on the mechanical properties of the load-bearing core. A push-out test, using dental stone as a bone model material, revealed that short glass fibre-reinforced porous surface layer is strong enough to carry load. Unreacted monomers can cause the chemical necrosis of the tissue, but the levels of leachable resisidual monomers were considerably lower than those found in chemically cured fibre-reinforced dentures and in modified acrylic bone cements. Animal experiments proved that surface porous FRC implant can enhance fixation between bone and FRC. New bone ingrowth into the pores was detected and strong interlocking between bone and the implant was achieved.

Crystallization characteristics of bioactive glasses

Bioactive glasses are excellent candidates for implant materials, because they can form a chemical bond to bone or guide bone growth, depending on the glass composition. Some compositions have even shown soft tissue attachment and antimicrobial effects. So far, most clinical applications are based on monoliths, plates and particulates of different grain sizes. There is a growing interest in special products such as porous implants sintered from microspheres and fibers drawn from preforms or glass melts. The viscosity range at which these are formed coincides with the crystallization temperature range for most bioactive glasses, thus complicating the manufacturing process. In this work, the crystallization tendency and its kinetics for a series of glasses with their compositions within the range of bioactivity were investigated. The factors affecting crystallization and how it is related to composition were studied by means of thermal analysis and hot stage microscopy. The crystal compositions formed during isothermal and non-isothermal heat treatments were analyzed with SEM-EDXA and X-ray diffraction analysis. The temperatures at which sintering and fiber drawing can take place without interfering with crystallization were determined and glass compositions which are suitable for these purposes were established. The bioactivity of glass fibers and partly crystallized glass plates was studied by soaking them in simulated body fluid (SBF). The thickness of silica, calcium and phosphate rich reaction layers on the glass surface after soaking was used as an indication of the bioactivity. The results indicated that the crystallization tendencies of the experimental glasses are strongly dependent on composition. The main factor affecting the crystallization was found to be the alkali oxide content: the higher the alkali oxide content the lower the crystallization temperature. The primary crystalline phase formed at low temperatures in these glasses was sodium calcium silicate. The crystals were found to form through internal nucleation, leading to bulk crystallization. These glasses had high bioactivity in vitro. Even when partially crystalline, they formed typical reaction layers, indicating bioactivity. In fact, sodium calcium silicate crystals were shown to transform in vitro into hydroxyapatite during soaking. However, crystallization should be avoided because it was shown to retard dissolution, bioactivity reactions and complicate fiber drawing process. Glass compositions having low alkali oxide content showed formation of wollastonite crystals on the surface, at about 300°C above the glass transition temperature. The wide range between glass transition and crystallization allowed viscous flow sintering of these compositions. These glasses also withstood the thermal treatments required for fiber drawing processing. Precipitation of calcium and phosphate on fibers of these glasses in SBF suggested that they were osteoconductive. Glasses showing bioactivity crystallize easily, making their hot working challenging. Undesired crystallization can be avoided by choosing suitable compositions and heat treatment parameters, allowing desired product forms to be attained. Small changes in the oxide composition of the glass can have large effects and therefore a thorough understanding of glass crystallization behavior is a necessity for a successful outcome, when designing and manufacturing implants containing bioactive glasses.

Mössbauer spectra of iron oxides in the bulk and nanocrystalline states

Magnetic nanoparticles are very important in modern industry. These particles are used in many different spheres of life. Nanoparticles have unusual physical and chemical properties connected both with quantum dimensional effects and with the increased role of the surface atoms. Most clearly the difference between the properties of bulk materials and nanoparticles can be seen in the magnetic properties of these materials. The most typical magnetic properties of nanomaterials are superparamagnetism with the size of the cluster from 1 to 10 nm; single-domain magnetic state of nanoclusters and nanostructures up to 20 nm; magnetization processes connected with magnetic cluster ordering and with its forms and sizes; quantum magnetic tunneling effects when magnetization changes by jumps and giant magnetoresistance effects. For research of the magnetic properties of iron-containing nanostructures, it is convenient to apply Mӧssbauer spectroscopy. In this work a number of nano-sized samples of iron oxides were examined by Mössbauer spectroscopy. The Mössbauer spectra of nanoparticles with various sizes were obtained. Mössbauer spectra of iron oxide nanoparticles were compared with the spectra of bulk samples. It was shown how the spectra of iron oxide nanoparticles change depending on the particle sizes.

Bioactive Glass in Lumbar Spondylodesis. A Pre-Clinical and Clinical Study

Bioactive glasses (BGs) form a group of synthetic, surface-active, composition-dependent, silica-based biomaterials with osteoconductive, osteopromotive, and even angiogenic, as well as antibacterial, properties. A national interdisciplinary research group, within the Combio Technology Program (2003–2007), developed a porous load-bearing composite for surgical applications made of BG 1–98 and polymer fibers. The pre-clinical part of this thesis focused on the in vitro and in vivo testing of the composite materials in a rabbit femur and spinal posterolateral fusion model. The femur model failed to demonstrate the previously seen positive effect of BG 1–98 on osteogenesis, probably due to the changed resorption properties of BG in the form of fibers. The spine study was terminated early due to adverse events. In vitro cultures showed the growth inhibition of human mesenchymal stems next to BG 1–98 fibers and radical pH changes. A prospective, long-term, follow-up study was conducted on BG–S53P4 and autogenous bone used as bone graft substitutes for instrumented posterolateral spondylodesis in the treatment of degenerative spondylolisthesis (n=17) and unstable burst fractures (n=10) during 1996–1998. The operative outcome was evaluated from X-rays and CT scans, and a clinical examination was also performed. On the BG side, a solid fusion was observed in the CT scans of 12 patients, and a partial fusion was found in 5 patients, the result being a total fusion rate in all fusion sites (n=41) 88% for levels L4/5 and L5/S1 in the spondylolisthesis group. In the spine fracture group, solid fusion was observed in five patients, and partial fusion was found in five resulting in a total fusion rate of 71% of all fusion sites (n=21). The pre-clinical results suggest that under certain conditions the physical form of BG can be more critical than its chemical composition when a clinical application is designed. The first long-term clinical results concerning the use of BG S53P4 as bone graft material in instrumented posterolateral spondylodesis seems to be a safe procedure, associated with a very low complication rate. BG S53P4 used as a stand-alone bone substitute cannot be regarded as being as efficient as AB in promoting solid fusion.

Survey of transportation of liquid bulk chemicals in the Baltic Sea

This study is made as a part of the Chembaltic (Risks of Maritime Transportation of Chemicals in Baltic Sea) project which gathers information on the chemicals transported in the Baltic Sea. The purpose of this study is to provide an overview of handling volumes of liquid bulk chemicals (including liquefied gases) in the Baltic Sea ports and to find out what the most transported liquid bulk chemicals in the Baltic Sea are. Oil and oil products are also viewed in this study but only in a general level. Oils and oil products may also include chemical-related substances (e.g. certain bio-fuels which belong to MARPOL annex II category) in some cargo statistics. Chemicals in packaged form are excluded from the study. Most of the facts about the transport volumes of chemicals presented in this study are based on secondary written sources of Scandinavian, Russian, Baltic and international origin. Furthermore, statistical sources, academic journals, periodicals, newspapers and in later years also different homepages on the Internet have been used as sources of information. Chemical handling volumes in Finnish ports were examined in more detail by using a nationwide vessel traffic system called PortNet. Many previous studies have shown that the Baltic Sea ports are annually handling more than 11 million tonnes of liquid chemicals transported in bulk. Based on this study, it appears that the number may be even higher. The liquid bulk chemicals account for approximately 4 % of the total amount of liquid bulk cargoes handled in the Baltic Sea ports. Most of the liquid bulk chemicals are handled in Finnish and Swedish ports and their proportion of all liquid chemicals handled in the Baltic Sea is altogether over 50 %. The most handled chemicals in the Baltic Sea ports are methanol, sodium hydroxide solution, ammonia, sulphuric and phosphoric acid, pentanes, aromatic free solvents, xylenes, methyl tert-butyl ether (MTBE) and ethanol and ethanol solutions. All of these chemicals are handled at least hundred thousand tonnes or some of them even over 1 million tonnes per year, but since chemical-specific data from all the Baltic Sea countries is not available, the exact tonnages could not be calculated in this study. In addition to these above-mentioned chemicals, there are also other high volume chemicals handled in the Baltic Sea ports (e.g. ethylene, propane and butane) but exact tonnes are missing. Furthermore, high amounts of liquid fertilisers, such as solution of urea and ammonium nitrate in water, are transported in the Baltic Sea. The results of the study can be considered indicative. Updated information about transported chemicals in the Baltic Sea is the first step in the risk assessment of the chemicals. The chemical-specific transportation data help to target hazard or e.g. grounding/collision risk evaluations to chemicals that are handled most or have significant environmental hazard potential. Data gathered in this study will be used as background information in later stages of the Chembaltic project when the risks of the chemicals transported in the Baltic Sea are assessed to highlight the chemicals that require special attention from an environmental point of view in potential marine accident situations in the Baltic Sea area.

Development of porous glass-fiber reinforced composite for bone implants. Evaluation of antimicrobial effect and implant fixation

Cranial bone reconstructions are necessary for correcting large skull bone defects due to trauma, tumors, infections and craniotomies. Traditional synthetic implant materials include solid or mesh titanium, various plastics and ceramics. Recently, biostable glass-fiber reinforced composites (FRC), which are based on bifunctional methacrylate resin, were introduced as novel implant solution. FRCs were originally developed and clinically used in dental applications. As a result of further in vitro and in vivo testing, these composites were also approved for clinical use in cranial surgery. To date, reconstructions of large bone defects were performed in 35 patients. This thesis is dedicated to the development of a novel FRC-based implant for cranial reconstructions. The proposed multi-component implant consists of three main parts: (i) porous FRC structure; (ii) bioactive glass granules embedded between FRC layers and (iii) a silver-polysaccharide nanocomposite coating. The porosity of the FRC structure should allow bone ingrowth. Bioactive glass as an osteopromotive material is expected to stimulate the formation of new bone. The polysaccharide coating is expected to prevent bacterial colonization of the implant. The FRC implants developed in this study are based on the porous network of randomly-oriented E-glass fibers bound together by non-resorbable photopolymerizable methacrylate resin. These structures had a total porosity of 10–70 volume %, of which > 70% were open pores. The pore sizes > 100 μm were in the biologically-relevant range (50-400 μm), which is essential for vascularization and bone ingrowth. Bone ingrowth into these structures was simulated by imbedding of porous FRC specimens in gypsum. Results of push-out tests indicated the increase in the shear strength and fracture toughness of the interface with the increase in the total porosity of FRC specimens. The osteopromotive effect of bioactive glass is based on its dissolution in the physiological environment. Here, calcium and phosphate ions, released from the glass, precipitated on the glass surface and its proximity (the FRC) and formed bone-like apatite. The biomineralization of the FRC structure, due to the bioactive glass reactions, was studied in Simulated Body Fluid (SBF) in static and dynamic conditions. An antimicrobial, non-cytotoxic polysaccharide coating, containing silver nanoparticles, was obtained through strong electrostatic interactions with the surface of FRC. In in vitro conditions the lactose-modified chitosan (chitlac) coating showed no signs of degradation within seven days of exposure to lysozyme or one day to hydrogen peroxide (H2O2). The antimicrobial efficacy of the coating was tested against Staphylococcus aureus and Pseudomonas aeruginosa. The contact-active coating had an excellent short time antimicrobial effect. The coating neither affected the initial adhesion of microorganisms to the implant surface nor the biofilm formation after 24 h and 72 h of incubation. Silver ions released to the aqueous environment led to a reduction of bacterial growth in the culture medium.

Unidirectional fiber-reinforced composite as an oral implant abutment material: Experimental studies of E-glass fiber/BisGMA-TEGDMA polymer in vitro

Fiber-reinforced composites (FRCs) are a new group of non-metallic biomaterials showing a growing popularity in many dental and medical applications. As an oral implant material, FRC is biocompatible in bone tissue environment. Soft tissue integration to FRC polymer material is unclear. This series of in vitro studies aimed at evaluating unidirectional E-glass FRC polymer in terms of mechanical, chemical, and biological properties in an attempt to develop a new non-metallic oral implant abutment alternative. Two different types of substrates were investigated: (a) Plain polymer (BisGMA 50%–TEGDMA 50%) and (b) Unidirectional FRC. The mechanical behavior of high fiber-density FRCs was assessed using a three-point bending test. Surface characterization was performed using scanning electron and spinning disk confocal microscopes. The surface wettability/energy was determined using sessile drop method. The blood response, including blood-clotting ability and platelet morphology was evaluated. Human gingival fibroblast cell responses - adhesion kinetics, adhesion strength, and proliferation activity - were studied in cell culture environment using routine test conditions. A novel tissue culture method was developed and used to evaluate porcine gingival tissue graft attachment and growth on the experimental composite implants. The analysis of the mechanical properties showed that there is a direct proportionality in the relationship between E-glass fiber volume fraction and toughness, modulus of elasticity, and load bearing capacity; however, flexural strength did not show significant improvement when high fiber-density FRC is used. FRCs showed moderate hydrophilic properties owing to the presence of exposed glass fibers on the polymer surface. Blood-clotting time was shorter on FRC substrates than on plain polymer. The FRC substrates also showed higher platelet activation state than plain polymer substrates. Fibroblast cell adhesion strength and proliferation rate were highly pronounced on FRCs. A tissue culture study revealed that gingival epithelium and connective tissue established an immediate close contact with both plain polymer and FRC implants. However, FRC seemed to guide epithelial migration outwards from the tissue/implant interface. Due to the anisotropic and hydrophilic nature of FRC, it can be concluded that this material enhances biological events related with soft tissue integration on oral implant surface.

Through the looking glass: does our metadata make sense?

Esitys KDK-käytettävyystyöryhmän järjestämässä seminaarissa: Miten käyttäjien toiveet haastavat metatietokäytäntöjämme? / How users' expectations challenge our metadata practices? 30.9.2014.