Variações de temperatura ocorridas durante a fotoativação de compositos odontologicos

Orientador: Simonides ConsaniDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: Nos últimos anos diversas fontes de luz fotoativadoras de compósitos odontológicos têm sido introduzidas no mercado, cada qual com suas características. No entanto, muitas dúvidas permanecem com relação ao possível aumento de temperatura durante a fotoativação de compósitos restauradores odontológicos. Assim, neste estudo procurou-se avaliar a influência de fatores envolvidos durante o procedimento de fotoativação sobre o grau de elevação da temperatura e suas conseqüências em algumas propriedades dos compósitos fotoativados. Visando o melhor entendimento, a pesquisa foi dividida em três trabalhos. O primeiro trabalho verificou a variação da temperatura durante a fotoativação, com três diferentes fontes de luz, em incrementos de 2 e 3mm utilizando dois compósitos restauradores. A maior espessura de compósito (3mm) contribuiu para a diminuição estatisticamente significante (p<0,05) da variação da temperatura. O fator fonte de luz também produziu diferença estatística significante na variação da temperatura durante a fotoativação (p<0,05), onde a fonte halógena produziu valores superiores de aumento de temperatura quando comparada às fontes de luz emitida por diodos (LED) e arco de plasma de Xenônio (PAC). O fator compósito influenciou no aumento de temperatura observada. O segundo trabalho verificou o aumento de temperatura durante a fotoativação e a dureza, quando utilizadas três fontes de luz e dois compósitos restauradores. A fonte de luz LED produziu menor valor de aumento de temperatura, independente do compósito utilizado ¿ Filtek Flow ou Filtek Z250 ¿quando comparada à fonte de luz halógena, porém com valores de dureza Knoop semelhantes. A luz emitida por arco de plasma de Xenônio gerou os menores valores de elevação da temperatura. Entretanto, esta fonte de luz produziu os menores valores de dureza Knoop quando comparada às fontes LED e halógena. O terceiro trabalho verificou a temperatura e o grau de conversão quando utilizadas três fontes de luz, com tempo de fotoativação indicado pelos fabricantes, tempo necessário para igualar a densidade de energia total e tempo necessário para igualar a densidade de energia na faixa entre 450-490nm do espectro eletromagnético. Quando utilizado o tempo preconizado pelos fabricantes, as fontes de luz halógena e LED produziram valores de grau de conversão estatisticamente semelhantes. Entretanto, o aumento de temperatura gerado pelo LED foi inferior. Quando a densidade total de energia foi padronizada, a fonte PAC produziu grau de conversão similar às demais fontes. Quando a densidade de energia foi igualada na faixa entre 450-490nm, a fonte de luz LED produziu valoresde grau de conversão estatisticamente superiores aos produzidos pela fonte PAC. A fonte PAC produziu os menores valores de variação da temperatura, independente do tempo de exposiçãoAbstract: In the last years several light curing units (LCUs) have been launched in the market, each one with its own characteristics. However, there are still many doubts concerning the possible temperature increase during the photo-activation of restorative dental composites. Thus, the aim of this study was to evaluate the influence of some factors involved during the photo-activation procedure on the degree of temperature increase and its consequences in some properties of photoactivated composites. For a better understanding, the research was divided in three works. The first work verified the temperature increase during photoactivation using three different LCUs in increments of 2 and 3mm using two composites. The thicker composite (3mm) contributed to a statistically significant decrease (p<0.05) in temperature increase. The light source factor also produced significant statistical difference in the temperature increase during photo-activation (p<0.05), where the halogen LCU produced higher values of temperature increase when compared to the sources LED and PAC (p <0.05). Composite type presented a complex behavior influencing temperature increase observed herein. The second work verified the temperature increase during photo-activation and the hardness using three LCUs and two restorative composites. The LED LCU produced lower values of temperature increase, regardless the composite used - Filtek Flow or Filtek Z250 - when compared with the halogen LCU, but with similar Knoop hardness values. The PAC LCU generated the lowest values of temperature increase. However, this light source produced the lowest Knoop hardness values regardless composite used. The third work verified the temperature increase and the degree of conversion using three LCUs, with adequate photo-activation time as recommended by the manufacturer - the amount of time needed to equal the total energy density and the amount of time needed to equal the energy density in the range between 450-490nm of the electromagnetic spectrum. When the time recommended by the manufacturer was used, the light sources QTH and LED produced statistically similar values of degree of conversion. However, the temperature increase generated by LED LCU was lower. When the total energy density was standardized, the PAC LCU produced a degree of conversion similar to the other LCUs. When the energy density was equaled in range between 450- 490nnm, the LED LCU produced values of degree of conversion statistically higher to the ones produced by the PAC LCU. The PAC LCU produced the smallest values of temperature increase, regardless the exposure timeMestradoMateriais DentariosMestre em Materiais Dentário

Shrinkage Stresses Generated during Resin-Composite Applications: A Review

Many developments have been made in the field of resin composites for dental applications. However, the manifestation of shrinkage due to the polymerization process continues to be a major problem. The material's shrinkage, associated with dynamic development of elastic modulus, creates stresses within the material and its interface with the tooth structure. As a consequence, marginal failure and subsequent secondary caries, marginal staining, restoration displacement, tooth fracture, and/or post-operative sensitivity are clinical drawbacks of resin-composite applications. The aim of the current paper is to present an overview about the shrinkage stresses created during resin-composite applications, consequences, and advances. The paper is based on results of many researches that are available in the literature

Exposure to polycyclic aromatic hydrocarbons in atmospheric PM1.0 of urban environments: Carcinogenic and mutagenic respiratory health risk by age groups

We investigated the carcinogenic and mutagenic respiratory health risks related to the exposure to atmospheric PAHs in an urban area. Our study focused in the association of these pollutants and their possible effect in human health, principally respiratory and circulatory diseases. Also, we determined a relationship between the inhalation risk of PAHs and meteorological conditions. We validated the hypothesis that in winter PAHs with high molecular weight associated to submicron particles (PM1) may increase exposure risk, especially for respiratory diseases, bronchitis and pneumonia diseases. Moreover, in our study we verified the relationship between diseases and several carcinogenic PAHs (Ind, BbkF, DahA, BaP, and BghiP). These individual PAHs contributed the most to the potential risk of exposure for inhalation of PM1.0. Even at lower ambient concentrations of BaP and DahA in comparison with individual concentrations of other PAHs associated to PM1.0. Mainly, research suggests to include carcinogenic and mutagenic PAHs in future studies of environmental health risk due to their capacity to associate to PM10. Such carcinogenic and mutagenic PAHs are likely to provide the majority of the human exposure, since they originate from dense traffic urban areas were humans congregate

Exposure to nanometric pollutants in primary schools: Environmental implications

School children are highly susceptible to chemicals in the atmosphere. Some studies have demonstrated that the pollution is related to respiratory problems and impaired cognitive development in children. In this context, the objective of this study was to determine nanoparticles and associated species and their origin in fresh air currents in La Salle Canoas School in Rio Grande do Sul (Brazil). Different analyses by using high-resolution transmission electron microscopy with energy-dispersive, X-ray spectroscopy (HR-TEM/SAED/EDS), and the scanning (STEM) mode were carried out. The EDS analysis of the atmospheric particles demonstrated that materials contain a significant proportion of elements such as Cr, Fe, Mn, Ni, and Si and other trace metals Zn, Pb, Zr, Ca, Cu, K, Cr, and Cd from exhaust and non-exhaust. The main source of the particles was emission from internal combustion in motor vehicles, road dust, and brake and tire wear. This emphasizes the importance of urban planning to reduce exposure of children to traffic gas emissions

Geochemical study of submicron particulate matter (PM1) in a metropolitan area

Air pollution has become a major problem in urban areas due to increasing industrialization and urbanization. In this study ambient concentrations of PM1 and metal concentrations as well as source contributions were identified and quantified by using Positive Matrix Factorization (PMF) in receptor modeling in the Metropolitan Area of Porto Alegre, Brazil. The PM1 samples were collected on PTFE filters from December 2012 to December 2014 in two sampling sites. Major ion and trace element concentrations were assessed. The average concentrations were 12.8 and 15.2 μg/m3 for Canoas and Sapucaia do Sul sites, respectively. Major ion contributions of PM1 were secondary pollutants such as sulfate and nitrate. Trace elements, especially Cu, Pb, Zn, Cd, and Ni also made important contributions which are directly associated with anthropogenic contributions. Our results show significantly higher levels in winter than in summer. Most of the PM1 and the analyzed PM species and elements originated from anthropogenic sources, especially road traffic, combustion processes and industrial activities, which are grouped in 7 major contributing sources. A back-trajectory analysis showed that the long-range transport of pollutants was not relevant in relation to the contribution to PM1 and metal concentrations. This work highlights the importance of urban planning to reduce human health exposure to traffic and industrial emissions, combined with awareness-raising actions for citizens concerning the impact of indoor sources

Study Of Coal Cleaning Rejects By FIB And Sample Preparation For HR-TEM: Mineral Surface Chemistry And Nanoparticle-Aggregation Control For Health Studies

Nano-minerals and amorphous nanoparticles play a vital role in the contexts of human health and environmental sustainability. For instance, aerosols generated by the process of coal beneficiation adversely affect human health as well as the environment. These are called Coal Cleaning Rejects (CCRs). They mainly contain clay minerals, nano-quartz, different particles of Fe/Al, and other Hazardous Elements (HEs) and compounds in minute quantities. In this work, we studied the CCRs of industrial facilities in Brazil for the presence of nanoparticles/nanominerals and HEs. CCRs were characterized using Focused Ion Beam (FIB) to evaluate nano-compound assemblages with high resolution-transmission electron microscopy/energy dispersive spectroscopy (HR-TEM/EDS) to assess the extent of risk to human health. In the present work, the importance of nanogeoscience in the description of CCRs and HEs in several secondary phases deposits (e.g. Fe and Al-sulfates, oxides and hydroxides minerals) has been emphasized and the presence of HEs in Brazilian coal abandoned area has been confirmed. This innovative study used an advanced characterization that will be useful in understanding the extent of environmental risk as well as a threat to human health, associated with CCRs

Regionalizações dos ovidutos em Boophilus microplus (Canestrini, 1887) (Acari:Ixodidae) e seu possível significado na fecundação

The structural analysis of oviducts in Boophilus microplus (Canestrini, 1887) in different stages of ingurgitation has indicated that they are constituted primarily of an internal cylinder and an external cylinder with different cell types being found between them. Copulated females in active ingurgitation process show typical variations along the internal cylinder, and three regions can be defined: anterior, ring-like and transitional. Based on such regionalization, hypotheses were raised about where and how fertilization takes place, a process yet to be clarified for the acari.Uma análise estrutural dos ovidutos de Boophilus microplus (Canestrini, 1887) em diferentes fases de ingurgitamento permitiu detectar que eles estão constituídos basicamente por dois cilindros celulares, um interno e outro externo; entre os quais foram encontrados diferentes tipos celulares. Fêmeas copuladas e em processo ativo de ingurgitamento mostram variações típicas ao longo do cilindro interno podendo ser definidas três regiões: anterior, anelar e de transição. Com base em tal regionalização, hipóteses sobre onde e como ocorre a fecundação, processo ainda não elucidado até o momento para ácaros, são levantadas

Nanometric particles of high economic value in coal fire region: Opportunities for social improvement

Spontaneous coal combustion in the La Guajira coals was studied for the presence of carbon nanophases (e.g., carbon nanotubes), occurrence of rare earth elements (REEs) in them, and the probable mechanisms for concentration of these rare compounds. For this purpose, various techniques such as scanning electron microscopy (SEM), Field-emission SEM, transmission electron microscopy (TEM), high-resolution TEM, and focused ion beam (FIB) were used. The development and alteration of the nanoparticles by geo-processes during the early modification periods of coal combustion were explored. Certain types of carbon nanophases and REE compounds may constitute nanominerals and ultra-fine particles accumulated in the coal peat. Assemblages of these nanophases (crystalline and amorphous compounds), predominantly the clay-monazite relationship and its connection to tonsteins in the coal combustion zones in the east region of the coal mines studied in this work, indicate that the coal area was subjected to REE concentration. The carbon nanophases contained several potential hazardous elements (PHEs), including, arsenic, bromine, cadmium, chlorine, fluorine, mercury, and other PHEs. While carbon nanotubes have been known to be produced from spontaneous combustion of coal of varying ranks, the present work is the first report on the naturally occurring REEs and carbon nanophases in the Colombian coal mining area

Geochemical study of submicron particulate matter (PM1) in a metropolitan area

Air pollution has become a major problem in urban areas due to increasing industrialization and urbanization. In this study ambient concentrations of PM1 and metal concentrations as well as source contributions were identified and quantified by using Positive Matrix Factorization (PMF) in receptor modeling in the Metropolitan Area of Porto Alegre, Brazil. The PM1 samples were collected on PTFE filters from December 2012 to December 2014 in two sampling sites. Major ion and trace element concentrations were assessed. The average concentrations were 12.8 and 15.2 µg/m3 for Canoas and Sapucaia do Sul sites, respectively. Major ion contributions of PM1 were secondary pollutants such as sulfate and nitrate. Trace elements, especially Cu, Pb, Zn, Cd, and Ni also made important contributions which are directly associated with anthropogenic contributions. Our results show significantly higher levels in winter than in summer. Most of the PM1 and the analyzed PM species and elements originated from anthropogenic sources, especially road traffic, combustion processes and industrial activities, which are grouped in 7 major contributing sources. A back-trajectory analysis showed that the long-range transport of pollutants was not relevant in relation to the contribution to PM1 and metal concentrations. This work highlights the importance of urban planning to reduce human health exposure to traffic and industrial emissions, combined with awareness-raising actions for citizens concerning the impact of indoor sources

Effect of the increase of energy density on knoop hardness of dental composites light-cured by conventional QTH, LED and xenon plasma arc

The aim of this study was to evaluate the effect of the increase of energy density on Knoop hardness of Z250 and Esthet-X composite resins. Cylindrical cavities (3 mm in diameter X 3 mm in depth) were prepared on the buccal surface of 144 bovine incisors. The composite resins were bulk-inserted and polymerized using different light-curing units and times: conventional QTH (quartz-tungsten-halogen; 700 mW/cm²; 20 s, 30 s and 40 s); LED (light-emitting diode; 440 mW/cm²; 20 s, 30 s and 40 s); PAC (xenon plasma arc; 1700 mW/cm²; 3 s, 4.5 s and 6 s). The specimens were stored at 37°C for 24 h prior to sectioning for Knoop hardness assessment. Three measurements were obtained for each depth: top surface, 1 mm and 2 mm. Data were analyzed statistically by ANOVA and Tukey's test (p0.05) were found for QTH. Knoop hardness values decreased with the increase of depth. The increase of energy density produced composites with higher Knoop hardness means using LED and PAC.Este estudo teve como objetivo avaliar o efeito do aumento da densidade de energia na dureza Knoop das resinas compostas Z250 e Esthet-X. Cavidades cilíndricas (3 mm de diâmetro X 3mm de profundidade) foram preparadas na superfície vestibular de 144 incisivos bovinos. As resinas compostas foram inseridas em incremento único e fotopolimerizadas com diferentes unidades e tempos de fotopolimerização: luz halógena convencional (700 mW/cm²; 20 s, 30 s and 40 s); LED (diodo emissor de luz; 440 mW/cm²; 20 s, 30 s and 40 s); PAC (arco de plasma de xenônio; 1700 mW/cm²; 3 s, 4,5 s and 6 s). Os espécimens foram armazenados a 37°C durante 24 h, previamente à realização das leituras de dureza Knoop. Foram realizadas três leituras por profundidade: superfície, 1 mm e 2 mm. Os dados foram submetidos à ANOVA e ao teste de Tukey (p0.05). Os valores de dureza Knoop diminuíram com o aumento da profundidade. O aumento da densidade de energia produziu compósitos com maior dureza Knoop quando o LED e o PAC foram utilizados como fontes de polimerização.21822