The reliability of the Brazilian version of the Composite International Diagnostic Interview (CIDI 2.1)

The objective of the present study was to determine the reliability of the Brazilian version of the Composite International Diagnostic Interview 2.1 (CIDI 2.1) in clinical psychiatry. The CIDI 2.1 was translated into Portuguese using WHO guidelines and reliability was studied using the inter-rater reliability method. The study sample consisted of 186 subjects from psychiatric hospitals and clinics, primary care centers and community services. The interviewers consisted of a group of 13 lay and three non-lay interviewers submitted to the CIDI training. The average interview time was 2 h and 30 min. General reliability ranged from kappa 0.50 to 1. For lifetime diagnoses the reliability ranged from kappa 0.77 (Bipolar Affective Disorder) to 1 (Substance-Related Disorder, Alcohol-Related Disorder, Eating Disorders). Previous year reliability ranged from kappa 0.66 (Obsessive-Compulsive Disorder) to 1 (Dissociative Disorders, Maniac Disorders, Eating Disorders). The poorest reliability rate was found for Mild Depressive Episode (kappa = 0.50) during the previous year. Training proved to be a fundamental factor for maintaining good reliability. Technical knowledge of the questionnaire compensated for the lack of psychiatric knowledge of the lay personnel. Inter-rater reliability was good to excellent for persons in psychiatric practice.

Intensification of hemicellulose hot-water extraction from spruce wood by parameter tuning

The growing population on earth along with diminishing fossil deposits and the climate change debate calls out for a better utilization of renewable, bio-based materials. In a biorefinery perspective, the renewable biomass is converted into many different products such as fuels, chemicals, and materials, quite similar to the petroleum refinery industry. Since forests cover about one third of the land surface on earth, ligno-cellulosic biomass is the most abundant renewable resource available. The natural first step in a biorefinery is separation and isolation of the different compounds the biomass is comprised of. The major components in wood are cellulose, hemicellulose, and lignin, all of which can be made into various end-products. Today, focus normally lies on utilizing only one component, e.g., the cellulose in the Kraft pulping process. It would be highly desirable to utilize all the different compounds, both from an economical and environmental point of view. The separation process should therefore be optimized. Hemicelluloses can partly be extracted with hot-water prior to pulping. Depending in the severity of the extraction, the hemicelluloses are degraded to various degrees. In order to be able to choose from a variety of different end-products, the hemicelluloses should be as intact as possible after the extraction. The main focus of this work has been on preserving the hemicellulose molar mass throughout the extraction at a high yield by actively controlling the extraction pH at the high temperatures used. Since it has not been possible to measure pH during an extraction due to the high temperatures, the extraction pH has remained a “black box”. Therefore, a high-temperature in-line pH measuring system was developed, validated, and tested for hot-water wood extractions. One crucial step in the measurements is calibration, therefore extensive efforts was put on developing a reliable calibration procedure. Initial extractions with wood showed that the actual extraction pH was ~0.35 pH units higher than previously believed. The measuring system was also equipped with a controller connected to a pump. With this addition it was possible to control the extraction to any desired pH set point. When the pH dropped below the set point, the controller started pumping in alkali and by that the desired set point was maintained very accurately. Analyses of the extracted hemicelluloses showed that less hemicelluloses were extracted at higher pH but with a higher molar-mass. Monomer formation could, at a certain pH level, be completely inhibited. Increasing the temperature, but maintaining a specific pH set point, would speed up the extraction without degrading the molar-mass of the hemicelluloses and thereby intensifying the extraction. The diffusion of the dissolved hemicelluloses from the wood particle is a major part of the extraction process. Therefore, a particle size study ranging from 0.5 mm wood particles to industrial size wood chips was conducted to investigate the internal mass transfer of the hemicelluloses. Unsurprisingly, it showed that hemicelluloses were extracted faster from smaller wood particles than larger although it did not seem to have a substantial effect on the average molar mass of the extracted hemicelluloses. However, smaller particle sizes require more energy to manufacture and thus increases the economic cost. Since bark comprises 10 – 15 % of a tree, it is important to also consider it in a biorefinery concept. Spruce inner and outer bark was hot-water extracted separately to investigate the possibility to isolate the bark hemicelluloses. It was showed that the bark hemicelluloses comprised mostly of pectic material and differed considerably from the wood hemicelluloses. The bark hemicelluloses, or pectins, could be extracted at lower temperatures than the wood hemicelluloses. A chemical characterization, done separately on inner and outer bark, showed that inner bark contained over 10 % stilbene glucosides that could be extracted already at 100 °C with aqueous acetone.

Wood biochemicals for the protection of health. Focus on hemicellulose, stilbenoids and lignans

Trees produce an enormous amount of compounds that are still scantly utilized.However, the results obtained from structurally similar biochemicals suggest that wood-derived compounds could be used for the protection of health in various applications. Polyphenols, for instance, could be extracted from wood in high quantities. Similar polyphenols to those in wood include resveratrol, found in grapes, and secoisolariciresinol, present in flaxseeds. Their consumption has been inversely associated with the incidence of various diseases, especially certain cancers and obesity-related disorders. The aim of this study was to determine the health-promoting effects of woodderived biochemicals. The effect of spruce hemicellulose on the growth of probiotic intestinal bacteria was studied. The results suggest that the bifidobacteria and lactobacilli can utilize hemicellulose and thus it has potential as a prebiotic compound. In particular, the efficacy of pine polyphenols to inhibit the growth of prostate cancer was our main interest. It was found that stilbenoids and lignans inhibited the proliferation of various cancer cells, and reduced the growth of prostate cancer xenografts in mice. The polyphenol rich pine knot extract was well tolerated in diet and extract-derived polyphenols were rapidly absorbed after intake. Furthermore, we determined the effect of the dietary pine knot extract on the weight gain and the expression of aromatase gene in reporter mouse expressing the promoter region of a human aromatase gene. It was found that dietary pine knot extract alleviated the obesity-induced inflammation in adipose tissue and downregulated the expression of a human aromatase gene. Taken together, several components of spruce and pine may have a future role as health-promoting compounds.

Magnetization studies of polystyrene/multiwall carbon nanotube composite films

Lappeenranta University of Technology School of Technology Technical Physics Evgenii Zhukov MAGNETIZATION STUDIES OF POLYSTYRENE/MULTIWALL CARBON NANOTUBE COMPOSITE FILMS Master’s thesis 2015 55 pages, 41 pictures, 9 Tables. Examiners: Professor Erkki Lähderanta D.Sc. Ivan Zakharchuk Keywords: polystyrene, multi-walled carbon nanotubes, MWCNT, composite, magnetization, SQUID. In this thesis magnetic properties of polystyrene/multiwall carbon nanotube (MWCNT) composites are investigated with Quantum Design SQUID magnetometer (MPMS XL). The surface of the composite films is studied via BRUKER Multimode 8 Atomic Force Microscope, as well. The polystyrene/MWCNT composites have been prepared by the group of professor Okotrub (Physics Chemistry of Nanomaterials laboratory, Nikolaev Institute of Inorganic Chemistry, Russia). The composite films have been prepared by solution processing and stretching method. The approximate length and inner diameter of the MWCNTs used in fabrication are 260 μm and 10 nm, respectively. The content of MWCNTs is 1 and 2.5 contents percent (wt%) for studied samples. The stretching of the samples is 30% for samples with 1 and 2.5 wt% content, and one sample with 1 wt% loading of MWCNTs is 100% stretched. MWCNTs aligned perpendicular to a silicon substrate are used as a reference sample. The magnetization field dependencies of the samples exhibit hysteresis behavior. The values of saturation magnetization of composite films are much less compared to that of the reference sample. The saturation magnetization coercitivity field value drops with decrease of MWCNT content. At high magnetic fields strong presence of diamagnetism is observed. Measurements in magnetic field parallel and perpendicular to the composite plate display anisotropy with respect to the direction of stretching. Temperature dependences of magnetization for all samples display difference between zero-field cooled and field-cooled curves of magnetization. This divergence confirms the presence of magnetic interactions in the material. The atomic force microscopy study of the composites’ surfaces revealed that they are relatively smooth and the nanotubes are aligned with the axis of stretching to some extent. 

Operant serial feature-positive conditional discrimination with composite features and different topography responses

In a serial feature-positive conditional discrimination procedure the properties of a target stimulus A are defined by the presence or not of a feature stimulus X preceding it. In the present experiment, composite features preceded targets associated with two different topography operant responses (right and left bar pressing); matching and non-matching-to-sample arrangements were also used. Five water-deprived Wistar rats were trained in 6 different trials: X-R®Ar and X-L®Al, in which X and A were same modality visual stimuli and the reinforcement was contingent to pressing either the right (r) or left (l) bar that had the light on during the feature (matching-to-sample); Y-R®Bl and Y-L®Br, in which Y and B were same modality auditory stimuli and the reinforcement was contingent to pressing the bar that had the light off during the feature (non-matching-to-sample); A- and B- alone. After 100 training sessions, the animals were submitted to transfer tests with the targets used plus a new one (auditory click). Average percentages of stimuli with a response were measured. Acquisition occurred completely only for Y-L®Br+; however, complex associations were established along training. Transfer was not complete during the tests since concurrent effects of extinction and response generalization also occurred. Results suggest the use of both simple conditioning and configurational strategies, favoring the most recent theories of conditional discrimination learning. The implications of the use of complex arrangements for discussing these theories are considered.

Fiber-reinforced composite fixed dental prostheses: Studies of the materials used as pontics

Fiber-reinforced composite fixed dental prostheses – Studies of the materials used as pontics University of Turku, Faculty of Medicine, Institute of Dentistry, Department of Biomaterials Science, Finnish Doctoral Program in Oral Sciences – FINDOS, Annales Universitatis Turkuensis, Turku, Finland 2015 Fiber-reinforced composites (FRC), a non-metallic biomaterial, represent a suitable alternative in prosthetic dentistry when used as a component of fixed dental prostheses (FDPs). Some drawbacks have been identified in the clinical performance of FRC restorations, such as delamination of the veneering material and fracture of the pontic. Therefore, the current series of studies were performed to investigate the possibilities of enhancing the mechanical and physical properties of FRC FDPs by improving the materials used as pontics, to then heighten their longevity. Four experiments showed the importance of the pontic design and surface treatment in the performance of FRC FDPs. In the first, the load-bearing capacities of inlay-retained FRC FDPs with pontics of various materials and thicknesses were evaluated. Three different pontic materials were assessed with different FRC framework vertical positioning. Thicker pontics showed increased load-bearing capacities, especially ceramic pontics. A second study was completed investigating the influence of the chemical conditioning of the ridge-lap surface of acrylic resin denture teeth on their bonding to a composite resin. Increased shear bond strength demonstrated the positive influence of the pretreatment of the acrylic surfaces, indicating dissolution of the denture surfaces, and suggesting potential penetration of the monomer systems into the surface of denture teeth. A third study analyzed the penetration depth of different monomer systems on the acrylic resin denture teeth surfaces. The possibility of establishing a durable bond between acrylic pontics and FRC frameworks was demonstrated by the ability of monomers to penetrate the surface of acrylic resin denture teeth, measured by a confocal scanning type microscope. A fourth study was designed to evaluate the load-bearing capacities of FRC FDPs using the findings of the previous three studies. In this case, the performance of pre-shaped acrylic resin denture teeth used as pontics with different composite resins as filling materials was evaluated. The filling material influenced the load-bearing capacities, providing more durable FRC FDPs. It can be concluded that the mechanical and physical properties of FRC FDPs can be improved as has been shown in the development of this thesis. The improvements reported then might provide long lasting prosthetic solutions of this kind, positioning them as potentially permanent rehabilitation treatments. Key words: fiber-reinforced composite, fixed dental prostheses, inlay-retained bridges, adhesion, acrylic resin denture teeth, dental material.

Influence of thermal treatment of wood on the aroma of a sugar cane spirit (cachaça) model-solution

The aging process of alcoholic beverages is generally conducted in wood barrels made with species from Quercus sp. Due to the high cost and the lack of viability of commercial production of these trees in Brazil, there is demand for new alternatives to using other native species and the incorporation of new technologies that enable greater competitiveness of sugar cane spirit aged in Brazilian wood. The drying of wood, the thermal treatment applied to it, and manufacturing techniques are important tools in defining the sensory quality of alcoholic beverages after being placed in contact with the barrels. In the thermal treatment, several compounds are changed by the application of heat to the wood and various studies show the compounds are modified, different aromas are developed, there is change in color, and beverages achieve even more pleasant taste, when compared to non-treated woods. This study evaluated the existence of significant differences between hydro-alcoholic solutions of sugar cane spirits elaborated from different species of thermo-treated and non-treated wood in terms of aroma. An acceptance test was applied to evaluate the solutions preferred by tasters under specific test conditions.

Biochemical characteristics of composite flours: influence of fermentation

The purpose of this study was to introduce yam in the development of two new composite flours containing soy and cassava. Two composite flours were obtained after fermentation of yam, soybean, and cassava in respectively 60, 30, and 10% proportions. Two varieties of yam were used: Dioscorea alata (variety "Bete bete") and Dioscorea cayenensis (variety "Lokpa"). Proximate composition, mineral content, some anti-nutritional factors (oxalates, phenols), microbiological quality, and α-amylase digestibility were determined for the fermented and unfermented composite flours. The results indicated that for the composite flours made of D. alata and D. cayenensis, fermentation increased ash and titrable acidity. Carbohydrates, pH, and energy decreased. Crude fat content was not affected by the fermentation process. Anti-nutritional factors such as oxalates and phenols were found to decrease significantly after the fermentation of the composite flours. Fermentation increased the mineral content (Mg, K, Fe, and Ca) of the composite flours. A decrease in P and Na was observed after fermentation. The microbiological study showed that safety flours contain no potential pathogenic germs. The in vitro α-amylase digestibility of the composite flours was significantly improved after fermentation. The biochemical characteristics and good hygienic quality of the obtained flours suggest that these flours can be considered as a feeding alternative for children in poor areas where yam is produced.

The feasibility of torrefaction for the co-firing of wood in pulverised-fuel boilers

Torrefaction is the partial pyrolysis of wood characterised by thermal degradation of predominantly hemicellulose under inert atmosphere. Torrefaction can be likened to coffee roasting but with wood in place of beans. This relatively new process concept makes wood more like coal. Torrefaction has attracted interest because it potentially enables higher rates of co-firing in existing pulverised-coal power plants and hence greater net CO2 emission reductions. Academic and entrepreneurial interest in torrefaction has sky rocketed in the last decade. Research output has focused on the many aspects of torrefaction – from detailed chemical changes in feedstock to globally-optimised production and supply scenarios with which to sustain EU emission-cutting directives. However, despite its seemingly simple concept, torrefaction has retained a somewhat mysterious standing. Why hasn’t torrefied pellet production become fully commercialised? The question is one of feasibility. This thesis addresses this question. Herein, the feasibility of torrefaction in co-firing applications is approached from three directions. Firstly, the natural limitations imposed by the structure of wood are assessed. Secondly, the environmental impact of production and use of torrefied fuel is evaluated and thirdly, economic feasibility is assessed based on the state of the art of pellet making. The conclusions reached in these domains are as follows. Modification of wood’s chemical structure is limited by its naturally existing constituents. Consequently, key properties of wood with regards to its potential as a co-firing fuel have a finite range. The most ideal benefits gained from wood torrefaction cannot all be realised simultaneously in a single process or product. Although torrefaction at elevated pressure may enhance some properties of torrefied wood, high-energy torrefaction yields are achieved at the expense of other key properties such as heating value, grindability, equilibrium moisture content and the ability to pelletise torrefied wood. Moreover, pelletisation of even moderately torrefied fuels is challenging and achieving a standard level of pellet durability, as required by international standards, is not trivial. Despite a reduced moisture content, brief exposure of torrefied pellets to water from rainfall or emersion results in a high level of moisture retention. Based on the above findings, torrefied pellets are an optimised product. Assessment of energy and CO2-equivalent emission balance indicates that there is no environmental barrier to production and use of torrefied pellets in co-firing. A long product transport distance, however, is necessary in order for emission benefits to exceed those of conventional pellets. Substantial CO2 emission reductions appear possible with this fuel if laboratory milling results carry over to industrial scales for direct co-firing. From demonstrated state-of-the-art pellet properties, however, the economic feasibility of torrefied pellet production falls short of conventional pellets primarily due to the larger capital investment required for production. If the capital investment for torrefied pellet production can be reduced significantly or if the pellet-making issues can be resolved, the two production processes could be economically comparable. In this scenario, however, transatlantic shipping distances and a dry fuel are likely necessary for production to be viable. Based on demonstrated pellet properties to date, environmental aspects and production economics, it is concluded that torrefied pellets do not warrant investment at this time. However, from the presented results, the course of future research in this field is clear.

Transmission oflight through individually formed fiber- reinforced composite post (Yksilöllisesti muotoillun kuitukomposiittinastan valonläpäisevyys)

Kuitukomposiitista valmistettuja juurikanavanastoja käytetään apuna, kun restauroidaan juurihoidettuja ja kruunuosastaan runsaasti kudosta menettäneitä hampaita. Kliinisen kestävyyden kannalta on tärkeää että nasta kiinnittyy hampaaseen hyvin. Tarvittavan valomäärän saattaminen valokovetuksella pimeään juurikanavaan on vaikeaa ja sen vuoksi nastojen kiinnittämiseen suositellaan kaksoiskovetteista yhdistelmämuovisementtiä, joka kovettuu vain osittain valolla. Jotta nasta ja sementti polymeroituisivat hyvin, nastan hyvä valonläpäisy- ja sirontakyky olisi eduksi. Tehdasvalmisteisten nastojen valonläpäisykyvyn on todettu heikkenevän niiden pituuden kasvaessa. Yksilöllisesti muotoilluilla kuitukomposiittinastoilla, joilla on osittaislomittaismuoviverkostorakenne (semi-IPN) polymeerimatriisi, on todettu tehdasvalmisteisia kuitunastoja parempi sidos nastan ja yhdistelmämuovisementin välillä. Yksilöllisesti muotoilluilla kuitunastoilla näyttäisi myös olevan hyvä valonjohtamiskyky, mutta lisätutkimuksia tarvitaan. Tässä tutkimuksessa selvitettiin yksilöllisesti muotoillun kuitukomposiittinastan (EverStick Post) ja kahden tehdasvalmisteisen (Relyx Fiber Post ja GC Fiber Post) kuitukomposiittina stan valonläpäisevyyttä sekä pituuden vaikutusta niiden valonläpäisykykyyn laboratorio- olosuhteissa. Tutkimushypoteesi oli, että nastojen valonläpäisykyky heikkenee niiden pidentyessä. Tutkimuksessa kaikista nastatyypeistä valmistettiin eripituisia nastoja (4, 8, 12 ja 16 mm). Nastoille tehtiin samanpituiset testikappaleet muoviputkesta ja polyvinyylisiloksaanista, ja nastat asetettiin niiden sisään. Tämän jälkeen nastoja kovetettiin valokovettimella 10 sekuntia, ja läpi päässyt valo mitattiin MARC Resin Calibrator -laitteella. Kontrollina käytettiin tyhjää testikappaletta ilman nastaa. Keskeiseksi tulokseksi saatiin, että yksilöllisesti muotoillulla kuitukomposiittinastalla oli kaikissa pituusryhmissä muita nastoja merkitsevästi parempi valonläpäisykyky. Tulokset osoittivat myös, että kaikkien nastojen valonläpäisevyys laski merkitsevästi nastan pituuden lisääntyessä aina 12 millimetriin asti. Tulosten perusteella yksilöllisesti muotoillulla kuitukomposiittinastalla on tehdasvalmisteista nastaa parempi valonläpäisykyky. Kuitukomposiittinastojen valonläpäisykyky heikkenee niiden pituuden kasvaessa aiempien tutkimusten mukaisesti. Jatkotutkimuksissa tulisi selvittää, miten valonläpäisevyys ja siroaminen vaikuttavat nastan ja sementin polymeroitumiseen ja siten kliiniseen lopputulokseen.

A software engineering approach to distributed systems for composite modeling

The goal of this thesis is to define and validate a software engineering approach for the development of a distributed system for the modeling of composite materials, based on the analysis of various existing software development methods. We reviewed the main features of: (1) software engineering methodologies; (2) distributed system characteristics and their effect on software development; (3) composite materials modeling activities and the requirements for the software development. Using the design science as a research methodology, the distributed system for creating models of composite materials is created and evaluated. Empirical experiments which we conducted showed good convergence of modeled and real processes. During the study, we paid attention to the matter of complexity and importance of distributed system and a deep understanding of modern software engineering methods and tools.

Enhancement of ultrafiltration process by pretreatment in recovery of hemicelluloses from wood extracts

Hemicelluloses are potential raw material for several items produced in future wood-based biorefineries. One possible method for recovering hemicelluloses from wood extracts is ultrafiltration (UF). However, low filtration capacities and severe fouling restrict the use of tight UF membranes in the treatment of wood extracts. The lack of suitable commercial membranes creates a need for pretreatment which would decrease fouling and increase the filtration capacity. This thesis focuses on the evaluation of the possibility to improve the filtration capacity and decrease fouling with the pretreatment of wood extracts. Methods which remove harmful compounds and methods which degrade them are studied, as well as combinations of the methods. The tested pretreatments have an influence on both the concentration of different compounds and the molecular mass distribution of the compounds in the extract. This study revealed that in addition to which kind of compounds were removed, also the change in molecular size distribution affected the filtration capacity significantly. It was shown that the most harmful compounds for the filtration capacity of the hydrophobic 5 kDa membrane were the ones capable of permeating the membrane and fouling also the inner membrane structure. Naturally, the size of the most harmful compounds depends on the used UF membrane and is thus case-specific. However, in the choice of the pretreatment method, the focus should be on the removal of harmful compound sizes rather than merely on the total amount of removed foulants. The results proved that filtration capacity can be increased with both adsorptive and oxidative pretreatments even by hundreds of per cents. For instance, the use of XAD7 and XAD16 adsorbents increased the average flux in the UF of a birch extract from nearly zero to 107 kg/(m2h) and 175 kg/(m2h), respectively. In the treatment of a spruce extract, oxidation by pulsed corona discharge (PCD) increased the flux in UF from 46 kg/(m2h) to 158 kg/(m2h). Moreover, when a birch extract batch was treated with laccase enzyme, the flux in UF increased from 15 kg/(m2h) to 36 kg/(m2h). However, fouling was decreased only by adsorptive pretreatment while oxidative methods had a negligible or even negative impact on it. This demonstrates that filtration capacity and fouling are affected by different compounds and mechanisms. The results of this thesis show that filtration capacity can be improved and fouling decreased through appropriate pretreatment. However, the choice of the best possible pretreatment is case-specific and depends on the wood extract and the membrane used. Finding the best option requires information on the extract content and membrane characteristics as well as on the filtration performance of the membrane in the prevailing conditions and a multivariate approach. On the basis of this study, it can be roughly concluded that adsorptive pretreatment improves the filtration capacity and decreases fouling rather reliably, but it may lead to significant hemicellulose losses. Oxidation reduces the loss of valuable hemicelluloses and could improve the filtration capacity, but fouling challenges may remain. Combining oxidation with adsorptive pretreatment was not a solution for avoiding hemicellulose losses in the tested cases.

Crescimento da firma e comércio exterior: revisitando a teoria de Adrian Wood

This paper analyzes the growth of the firm by foreign trade. The theory of Adrian Wood is revisited for the analysis of growth and profit trade-off and improved to cope with growth by exports. The main outcome of this paper is that low domestic demand can be a very important factor to firm choices growth by foreign market. However, the growth of domestic demand does not necessarily reduce exports.

Tuotannon- ja materiaalinsuunnittelu ja sen ennustaminen Metsä Wood:n Suolahden koivuvaneritehtaalla

Tässä diplomityössä tutkitaan Metsä Woodin Suolahden koivuvaneritehtaan toimitustarkkuuteen negatiivisesti vaikuttavia tekijöitä. Tarkoituksena on löytää ne ongelmakohdat, mitkä heijastuvat toimitusten myöhästymisenä sekä muutostekijät, mitkä vaikuttavat toimitusviikon myöntämiseen. Lisäksi työssä kartoitetaan kuinka hyvin tietoa ja informaatiota on tarjolla sitä tarvitseville henkilöstötahoille. Teoriaosuudessa tarkastellaan tuotannonsuunnitteluun liittyviä teorioita sekä tiedon liikkumista organisaation sisällä. Työssä kuvataan Suolahden koivuvaneritehtaan nykyinen vanerin valmistusprosessi ja tuotannonsuunnittelu. Varsinainen tutkimustyö suoritetaan laadullisia tutkimusmenetelmiä hyväksikäyttäen. Tulosten tarkastelussa käsitellään työn aikana tapahtuneita muutoksia ja ongelmakohtia sekä analysoidaan kyselytutkimuksen tuloksia ja tulosten luotettavuutta. Yhteenvedossa esitetään pääongelmakohdat ja niiden ratkaisut ja esitetään uusia mielenkiintoisia jatkotutkimusaiheita.

Optimal distance of the light-curing tip for light transmission through the resin composite

Hammaslääketieteessä käytetettävien komposiittien valonläpäisevyys vaihtelee. Samoin LED-valokovettimet eroavat toisistaan valotehonsa ja muotoilunsa perusteella. On yleisesti tiedossa, että valokovettimesta tulevan valon intensiteetti pinta-alayksikköä kohden heikkenee, kun kovettimen etäisyys kasvaa. Toisaalta ei ole tiedossa, miten valokovetettavan kohteen ja valokovettimen kärjen väliin sijoitettu materiaali tarkalleenottaen vaikuttaa valon intensiteettiin eri etäisyyksiä käytettäessä. Tämän tutkimuksen tarkoituksena on selvittää, miten valokovetettavan kohteen ja valokovettimen kärjen väliin asetettava etukäteen polymerisoitu materiaali vaikuttaa valon intensiteettiin eri etäisyyksillä. Tutkimus suoritettiin käyttämällä kahta eri valokovetinta. Jotta etäisyyden vaikutusta valotustehoon voitiin demonstroida, vaihdettiin kovettimen etäisyyttä sensorista 0,2,4,6,8,10mm välillä. Valotehot rekisteröitiin MARC resin calibrator -laitteella. Sensorin ja valokovettimen kärjen väliin asetettavat erilaiset komposiittilevyt olivat valmiiksi kovetettuja,1mm paksuisia, filleripitoisuuksiltaan neljää erilaista muovia. Valotehot rekisteröitiin jokaiselta etäisyydeltä komposiitin ollessa sensorin päällä. Rinnakkaisesti verrattiin myös etäisyyden vaikutusta valotehoon ilman esikovetettua materiaalia kovettimen kärjen ja valoa mittaavan sensorin välissä. Vertailun suorittamiseksi laskettiin intensiteettisuhdeluku muovillisen ja muovittoman arvon välillä aina tietyllä etäisyydellä Valokovettimen kärjen etäisyyden kasvattaminen sensorista (eli valokovetettavasta kohteesta) odotusten mukaisesti pienensi valotehoa. Laittamalla sensorin ja kovettimen väliin komposiittilevy, valoteho pieneni odotetusti vielä enemmän. Tutkittaessa intensiteettisuhdetta (valoteho muovin kanssa : valoteho ilman muovia) kuitenkin huomattiin, että 4-6mm:n kohdalla suhdeluku oli suurempi kuin 0,2,8 ja 10mm kohdalla. Johtopäätöksenä oli, että suurin mahdollinen valokovetusteho saavutetan laittamalla kovetuskärki mahdollisimman lähelle kohdetta. Jos valokovetettavan kohteen ja valokovettimen kärjen välissä oli kiinteä komposiittipalanen, suurin mahdollinen valokovetusteho kohteeseen saavutetaan edelleen laittamalla kovetuskärki kiinni muoviin. Jos etäisyyttä muovin pinnasta sen sijaan kasvatettiin, valokovetusteho ei laskenutkaan niin nopeasti kuin oli odotettu. Tämä voi liittyä siihen, että tehokkaan valokeilan halkaisijan koko on suurempi verrattuna komposiitin sekä sensorin halkaisian kokoon. Toiseksi on arvioitu, että resiinikomposiitin täyteaineet voisivat fokusoida läpi kulkevaa valoa sensoriin. Se, pitääkö tämä ilmiö paikkansa, vaatii kuitenkin enemmän tutkimusta