Two different research projects were investigated for this thesis, which has consequently been presented in two parts. PART 1 An attempt has been made to improve the high temperature performance of phenol-formaldehyde thermosets by modification of their structure with inorganic phosphate groups. Transesterification of tri-phenyl phosphate with resorcinol has given a resorcinol phosphate resin, which cured with hexamethylenetetramine. A pilot scale batch of this resin has been made and used in high temperature stability studies. Post-cured resorcinol phosphate resin-chrysotile asbestos (30: 70) moulded bars retained 59.5% of their flexural strength after ageing at 523K for 1000 hr in air. Similar phenol-formaldehyde composite bars aged under identical conditions retained only 5.3% of their initial flexural strength. The utility of the resorcinol phosphate resin composite as a commercial product is limited, since the bars had a much lower initial flexural strength (30.85 MNm-2) than the phenol-formaldehyde resin composite bars (108.5 MNm-2). Thermogravimetry and isothermal heating studies have indicated that the degradation of resorcinol phosphate resin was greatly accelerated by chrysotile asbestos, which may catalyse a bond re-organisation process that has been tentatively proposed as a mechanism for the fragmentation of the resin. PART 2 Recently an ionomer dental cement (ASPA), prepared from aqueous poly(acrylic acid) and an ion-leachable aluminosilicate glass, has been developed. The system has been extended by studying other aqueous polymers. The factors influencing the gelation and the properties of the set cements have been examined. Poly(carboxylic acids) with hydrophobic, or no pendant substituents were found to be the most satisfactory polymers for preparing water stable cements. To study the influence of the nature of the cation and polymer structure on the gelation and water stability of ionomer cements, a wide range of metal oxide-polyacid products have been studied. The formation of water stable cements depended markedly on the type of oxide and polyacid employed and appeared to involve factors such as the co-ordination geometry and radius of the cation and the nature of the cation-polyanion bonding in the matrix. A comparison between the water stabilities of ASPA cement and poly(acrylic acid)-CaO, Al2O3, or Al(OH)3 cements has shown that the chemistry of ASPA cement is more complex than has been hitherto reported. Stability constants have been determined for Ca 2+ and Cd 2+ with poly(acrylic acid) and ethyl ethylene-maleic acid copolymer by a potentiometric titration method developed by Gregor and modified by Mandel and Leyte. The stability constants obtained in 1.0M NaNO3 at 298.2 ± 0.2K were: for poly(acrylic acid), with Cat2+, log b1 Ca2+ PAA ~ -3.35 with Cd2+, log Bav Cd2+ PAA = -2.30 for ethylene-maleic acid copolymer, with Cat2+, log b1 CA2+ EMA ~ -4.05 with Cd2+, log Bav Cd2+ EMA = -1.95 The log b1 values probably had little precise meaning, although to a first approximation, log b1 Ca2+ PAA > log b1 Ca2+ EMA The determined stability constants have been used with limited success in predicting the water stabilities of the corresponding metal oxide-polyacid cements.

Orientador: Angela Cristina Cilense Zuanon / Resumo: O cimento de ionômero de vidro (CIV) apresenta características favoráveis como ação antimicrobiana e capacidade de remineralização. A fim de potencializar essas propriedades, sua associação com outros materiais como as nanopartículas (NP) e os vidros bioativos (VB) é estudada e muita atenção deve ser voltada às possíveis alterações que podem ocorrer em suas propriedades físicas, mecânicas e químicas. O objetivo deste estudo foi avaliar propriedades físicas e mecânicas do CIV associado a NP de hidroxiapatita (HPa) a 5% e ao VB 45S5 a 10%, antes e após teste de escovação, em diferentes tempos de armazenamento. Foram avaliadas rugosidade superficial com auxílio de rugosímetro, dureza Vickers por meio de microdurômetro, e variação de massa do material medida por pesagens em balança analítica, além da análise qualitativa de sua superfície, por meio de perfilômetro, nos tempos de 1, 7, 15, 30 e 60 dias, antes e após o teste de escovação. Os dados obtidos foram analisados estatisticamente quanto à normalidade e a homogeneidade. A distribuição foi não normal e os testes não-paramétricos de Wilcoxon, e de Kruskal Wallis seguido pelo de Dunn foram realizados, todos com um nível de significância de 5%. Pode-se observar maiores valores para a perda de massa no primeiro dia de experimento para todos os grupos. A rugosidade superficial foi menor nos grupos Controle e NP aos 30 dias de experimento após o ensaio de escovação. A análise qualitativa por meio do perfil dos materiais confirma a ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The glass ionomer cement (GIC) has favorable characteristics such as antimicrobial action and remineralization capacity. In order to potentiate these properties, its association with other materials such as nanoparticles (NP) and bioactive glasses (BAG) is studied, and a great deal of attention must be given to the possible changes that may occur in the physical, mechanical and chemical properties. The objective of this study was to evaluate the physical and mechanical properties of GIC associated with 5% of hydroxyapatite NP (NPHPa) and of 10% BAG 45S5 before and after brushing test at different storage times. The surface roughness was evaluated using a rugosimeter, Vickers hardness by microdurometer, and mass variation of the material measured by analytical weighing, as well as the qualitative analysis of its surface by means of a profilometer at the times of 1, 7, 15, 30 and 60 days, before and after the brushing test. The data obtained were statistically analyzed for normality and homogeneity. The distribution was non-normal and the non-parametric Wilcoxon and Kruskal Wallis followed by Dunn's tests were performed, all with a significance level of 5%. It is possible to observe higher values for the loss of mass in the first day of experiment for all the groups. The surface roughness was lower in the control and NP groups at 30 days of experiment after the brushing test. The qualitative analysis through the profile of the materials confirms these findings. Larger values fo... (Complete abstract click electronic access below) / Mestre

O objetivo deste estudo cego foi avaliar in vitro a microinfiltração marginal em restaurações de cimento de ionômero de vidro, com e sem adição de antibióticos, em dentes decíduos. Os dois materiais utilizados foram o Vidrion-R e o Vitro Molar, sendo vinte dentes obtidos no banco de dentes de Departamento de Odontologia da UNITAU para cada grupo. Cada dente recebeu uma restauração na face vestibular e outra na face lingual/palatina, uma com adição de antibióticos (Metronidazol, Ciprofloxacina e Cefaclor) e outra sem. Os dentes, após a impregnação do corante (solução de nitrato de prata a 50%), foram seccionados no sentido vestíbulolingual/ palatino. Os cortes foram observados com lupa esteroscópica por um examinador calibrado, o qual atribuiu escores conforme o grau de microinfiltração marginal. Os dados obtidos foram submetidos ao teste estatístico Mann-Whitney, com nível de significância de 5%. Os grupos que receberam restaurações sem adição de antibióticos apresentaram resultados estatisticamente inferiores àqueles que receberam com adição dos antibióticos (p=0,00001). Na comparação entre os grupos que não receberam adição de antibióticos (Vidrion-R e Vitro Molar), não houve diferença estatisticamente significativa (p=0,162). Resultados semelhantes foram encontrados na comparação entre os grupos que receberam restaurações com adição de antibióticos. Não houve diferença estatisticamente significativa também entre o Vidrion-R com antibióticos e o Vitro Molar com antibióticos (p=0,519). A partir dos resultados obtidos, pode-se inferir que a inclusão de agentes antimicrobianos ao pó do cimento de ionômero de vidro convencional ou indicado para o tratamento restaurador atraumático aumentou a microinfiltração marginal de restaurações com estes materiais. / The purpose of this blind trial study was to evaluate in vitro the marginal microleakage in restorations of glass ionomer cement, with and without the addition of antibiotics in temporary teeth. The two materials used were the Vidrion-R and Vitro Molar, being twenty teeth obtained in the teeth bank of the Department of Dentistry of UNITAU for each group. Each tooth received one restoration in the bucal face and another in the lingual / palate face, with an addition of antibiotics and one without. The teeth, after the impregnation of the dye (solution of silver nitrate to 50%), were cut in order bucal to lingual. The cuts were seen with a magnifying glass by a calibrated examiner, which gave the scores as the degree of microleakage marginal. The data were submitted to the Mann-Whitney statistical test, with significant level of 5%. The groups that received restorations without added antibiotics showed results statistically lower than those who received with the addition of antibiotics (p=0,00001). In comparison between the groups who did not receive addition of antibiotics (Vidrion-R and Vitro Molar), there was no statistically significant difference (p=0,162). The same result was find when comparing the two groups that received the restorations with the addition of antibiotics. There was no statistically significant difference between the Vidrion-R with antibiotics and Vitro Molar with antibiotics (p=0,519). From the results, it is suggested that the inclusion of antimicrobial agents to the glass ionomer cement increased the microleakage marginal in restorations with these materials.

No description available.

Novel poly(ethylene isophthalate) (PEI) and poly(ethylene terephthalate) (PET) polymers containing terminal units derived from sodio 3-sulfobenzoic acid (SSBA) were synthesized using catalyzed melt polymerization techniques. Various concentrations of the ionic end group, SSBA, were successfully incorporated in a telechelic fashion. For comparison, polyesters containing telechelic alkyl groups with controllable molecular weights were also synthesized. Furthermore, ionic copolymers of dimethyl isophthalate and trans-cyclohexane dicarboxylate, dimethyl isophthalate and dimethyl terephthalate were synthesized to study the influences of polarity and rigidity of the polymer chain backbone on material properties. Novel branched polyester ionomers using trimellitic anhydride were also prepared. In addition to modifying the polymer compositions, PET ionomers were blended with zinc stearate to investigate the effect of plasticizer on the melt processibilty of the ionomers. FTIR spectroscopy, which was used to quantify the sulfonate end groups for all of the ionomers, indicated an absorbance peak for the S-O stretching mode between 600-700 cm⁻¹. ¹H NMR spectroscopy was used to confirm the structure of the ionic and non-ionic polyesters, as well as to verify the presence of the terminal groups. By systematically varying the chemical structure of these ionomer model systems (i.e., altering the contents of ionic functional groups), detailed characterizations were carried out, wherein the ionic interactions/aggregations in the ionomers were found to play an important role in the resulting material properties. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements were performed to study the effects of ionic groups and oligomer composition on the thermal properties of the polyesters. The glass transition temperatures of the ionomers revealed that the ionic interaction helped to maintain the structural integrity of the polymer chains, thus limiting their mobility. The dilute solution viscosity behavior of the ionomers exhibited upward curvature, which is a key characteristic of an ionomer. In PEI ionomers, the ionic aggregates formed at lower temperatures (<150 °C), while at higher temperatures (>150 °C), the ionic aggregations dissociated and behaved similarly to oligomers with lower molecular weights. Dodecanol was used as an effective end-capper to control the molecular weight of the non-ionic polyesters. In addition to telechelic ionic PEI and PET homopolymers, copolymers of poly(ethylene isophthalate-co-trans-1,4-cyclohexane dicarboxylate) (PEI-co-trans-CHDC) and poly(ethylene isophthalate-co-terephthalate) (PEIT) telechelic ionomers were also synthesized and characterized. Introducing trans-1,4-cyclohexane dicarboxylate into PEI ionomers decreased the polarity and packing regularity of the polymer chains. Also, the kinked-structure of dimethyl isophthalate reduced the regularity of the polymer chains in PET ionomers, thus reducing their propensity for rapid crystallization. Crystallization kinetics were studied for both ionic and alkyl telechelic polyesters, and resulting data revealed that the nature of the endgroup had a dramatic effect on crystallization from the melt state. The catalyst residue in the polymers also affected the crystallization rate for both ionic and non-ionic polyesters. With regard to the ionomers, antimony catalyst interacted with ionic aggregates, further increasing the crystallization rate. Branched PEI and PET ionomers showed an increase in melt strength. After blending with zinc stearate, the melt viscosity of the PET ionomers dropped dramatically. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / The luting agent is a crucial factor in the outcome of cemented fixed restorations. A new water-based cement, Ceramir C&B (CM), approved to be marketed in the US, is composed of calcium aluminate and glass ionomer. CM is a luting agent indicated for permanent cementation of cast restorations, all-zirconia or all-alumina crowns, and prefabricated metal and cast dowel and cores. The manufacturer claims that the cement has demonstrated favorable biocompatibility properties when tested in vitro and in vivo and has proven to be bioactive. The objective of this study was to evaluate volumetric dimensional changes and the amount of Ca2+ released by the new luting agent. Twenty specimens of each material, namely calcium aluminate glass ionomer, resin-modified glass ionomer, and two resin luting agents, were fabricated and weighed. The 20 specimens for all materials were divided into four groups (five samples in each group) based on storage conditions: silicone oil at 22°C and 37°C and distilled water at 22°C and 37°C. Using the manufacturers’ instructions for each material, cylindrical specimens were prepared with dimensions of 7 +0.1 mm in diameter and 2 +0.1 mm in height. A 0.01-mg resolution balance was used to determine volumetric dimensional change using an Archimedean equation. Measurements were made 30 minutes after mixing, and at the time intervals of 7 days, 14 days, 21 days, and 30 days, and after total dehydration of the specimen. Chemical analyses of the solutions were performed using atomic absorption spectroscopy to determine the Ca+2 ion concentration. Moreover, the pH values were measured to determine the OH–concentration in the solutions. The results showed that CM had the most expansion among the tested luting agents in distilled water at 22°C and 37°C, and significantly increased at higher temperature. In silicone oil, resin-modified glass ionomer shrank the most and also shrank more with the high temperature. The result of the ion concentration analysis indicated that Ca+2 and OHion release increased with increasing time and also significantly with temperature rise. In conclusion, calcium aluminate-glass ionomer exhibited the most significant dimensional change when stored in water storage. The solubility of the tested luting agents should be evaluated in the future because they were not evaluated in this study. Furthermore, to evaluate the clinical effect of the dimensional changes, the impact on the gap formation at tooth-crown margins should be determined in future work.

No description available.

No description available.

Proton-Exchange Membrane Fuel Cells are an alternative source of electricity generation for automobiles and stationary power plants. With increasing concerns on environmental issues, recent research has focused on maximizing the efficiency and durability as well as minimizing the costs of fuel cells. One of the main areas of research is optimizing the structure of the cathode catalyst layer. The main driving force of this thesis was the effective visualization of nanostructure of the ionomer, which is responsible for proton conduction in the cathode catalyst layer. However, challenges regarding sample preparation and radiation damage still need to be well understood. Different sample preparation techniques of catalyst inks and catalyst coated membranes were used for Scanning and Transmission Electron Microscopy, such as freeze fracturing, ultramicrotomy and Focused Ion Beam. Comparisons of the microstructure and chemical differences of all components, especially the ionomer, prepared by ultramicrotomy and Focused Ion Beam, was done with Transmission Electron Microscopy and Scanning Transmission X-ray Microscopy applied to the same catalyst coated membrane sample. Detailed spectroscopic information regarding components in both specimens was compared with C 1s and F 1s near edge X-ray absorption spectra recorded in a Scanning Transmission X-ray Microscope. Focused Ion Beam causes extensive damage to the carbon support and ionomer but prepares thinner sections than ultramicrotomy. This work makes it possible to understand the limitations of each sample preparation and compositional analysis technique in order to later apply one of them to image the ionomer in the catalyst layer at the nanoscale, hopefully using tomography techniques. / Thesis / Master of Materials Science and Engineering (MMatSE)

Indiana University-Purdue University Indianapolis (IUPUI) / The furanone derivatives and their constructed polymers were synthesized, characterized and formulated into dental glass-ionomer cement (GIC) and resin composite for improved antibacterial properties. Compressive strength (CS) and S. mutans viability were used to evaluate the mechanical strength and antibacterial activity of the restoratives. Fuji II LC cement and P60 were used as control. The specimens were conditioned in distilled water at 37 oC for 24 h prior to testing. The effects of loading, saliva and aging on CS and S. mutans viability were investigated. The antibacterial effect of the furanone derivative on other bacteria was also studied. Chapter 2 describes how we studied and evaluated the formulated antibacterial glass-ionomer cement by incorporating the synthesized furanone derivative-containing polymer into the formulation. The results show that all the formulated furanone-containing cements showed a significant antibacterial activity, accompanying with an initial CS reduction. Increasing loading significantly enhanced antibacterial activity but reduced the initial CS of the formed cements. The derivative showed a broad antibacterial spectrum on bacteria including S. mutans, lactobacillus, S. aureus and S. epidermidis. Human saliva did not affect the antibacterial activity of the cement. The long-term aging study indicates that the cements may have a long-lasting antibacterial function. Chapter 3 describes how we studied and evaluated the formulated antibacterial resin composite by incorporating the synthesized furanone derivative into the basic resin formulations. The results show that the modified resin composites showed a significant antibacterial activity without substantially decreasing the mechanical strengths. With 5 to 30% addition of the furanone derivative, the composite kept its original CS unchanged but showed a significant antibacterial activity with a 16-68% reduction in the S. mutans viability. Further, the antibacterial function of the new composite was not affected by human saliva. The aging study indicates that the composite may have a long-lasting antibacterial function. In summary, we have developed a novel furanone-containing antibacterial system for dental restoratives. Both glass-ionomer cement and resin composite have demonstrated significant antibacterial activities. The modified experimental glass-ionomer cement is a promising system because the reduced strength of the cement with addition of the furanone-containing polymer is still above those demonstrated by original commercial cement Fuji II LC. The modified resin composite shows nearly no reduction in mechanical strength after incorporation of the antibacterial furanone derivative. It appears that both experimental cement and resin composite are clinically attractive dental restoratives that can be potentially used for long-lasting restorations due to their high mechanical strength and permanent antibacterial function.