A remineralização é uma prática antiga que está associada a aplicação de pós de rocha no solo visando a melhoria das propriedades edáficas e por fim o aumento da produtividade, associado também a redução dos custos de produção, uma vez que os remineralizadores possuem menor preço comparado com fertilizantes sintéticos solúveis. Porém ainda existem divergências nos resultados obtidos com o uso de remineralizadores, por vezes associados a dificuldade na descrição e controle dos fatores que podem interferir no processo, como clima, características do solo e do remineralizador empregado. Esta tese tem por objetivo investigar a dissolução de um remineralizador em experimentos em diferentes níveis de complexidade e avaliar as alterações mineralógicas correspondentes, inclusive com ênfase na possibilidade de neoformação de minerais. No experimento in vitro foi possível identificar os efeitos do tamanho das partículas e dos diferentes solventes na dissolução dos minerais do remineralizador. Aumentando o nível de complexidade, no experimento em colunas contendo solo, foi possível identificar principalmente um incremento nos teores de Ca+2, Mg+2, K+ trocáveis no solo, além do Na+, Fe e Si no tratamento com a aplicação do remineralizador. Também houve aumento dos teores de Fe e Al extraídos em solução de ditionito-citrato-bicarbonato e oxalato de amônio e, em concordância com os diagramas de estabilidade termodinâmica dos minerais, foi constatada a precipitação de óxidos de baixa cristalinidade no tratamento com remineralizador. No experimento em vasos, a presença das plantas atuou como um dreno, mas mesmo assim com aumento principalmente dos teores de Ca+2 e Mg+2 trocáveis, mas sem ser constatada a precipitação de óxidos amorfos. Por fim, o experimento de campo reafirma o que foi observado nos dois experimentos anteriores, no qual houve aumento dos teores de Ca+2, Mg+2, Na+ e Si trocáveis. Em todos os níveis de experimentos, de forma geral, foi possível observar a maior contribuição de plagioclásios cálcio-sódicos e clinopiroxênios no fornecimento de Ca+2 e Mg+2, principalmente, além de Na+, ferro e silício. / The remineralization is an ancient practice of application of rock powders into the soil in order to improve the soil properties and increase productivity. It is also associated with the reduction of production costs, since remineralizers are cheaper as compared to soluble synthetic fertilizers. Contradiction among the results obtained from the use of remineralizadores frequently be associated with difficulty to describe and control of the factors that may affect the results, such as climate, soil characteristics and characterization of the remineralizers used. This thesis aims to investigate the dissolution of remineralizers in experiments with increasing levels of complexity and evaluate the mineralogical changes, emphasing the possibility of neoformation minerals. In the in vitro experiment, it was possible to identify the effects of particle size and different solvents in the dissolution of the mineral presents in the remineralizer. The rock powder when applied in columns containing soil allowed to identify an increase in Ca+2, Mg+2, K+ exchangeable, including Na+, Fe and Si. Also increased the levels of Fe and Al extracted solution of sodium dithionite-citrate-bicarbonate, ammonium oxalate and in accordance with the thermodynamic stability diagrams of minerals, the precipitation of low crystallinity oxide in remineralizer treatment. In the pot experiment, the presence of plants acted as a drain, but there was still an increase of Ca+2 and Mg+2 exchangeable, specially, but without was observed precipitation of amorphous oxides. Finally, field experiment confirms what was observed in the two previous experiments in which there was an increase in Ca+ 2, Mg+ 2, Na+ and Si exchangeable. At all experiments, in general, we observed the greatest contribution of plagioclase and clinopyroxenes in providing of Ca+2 and Mg+2 in large amount, as well as Na+, Fe and Si in minor quantity.

Apesar dos conhecimentos já existentes sobre o xilitol, seu efeito no desenvolvimento da cárie dentária ainda requer maiores esclarecimentos. Assim, este estudo in situ randomizado, duplo-cego e cruzado teve como objetivo determinar o efeito de xilitol em pastilhas na composição do biofilme dental e nos processos de desmineralização e remineralização do esmalte, comparado a um controle com pastilhas contendo sorbitol. Em duas fases de 14 dias, 11 voluntários utilizaram dispositivos palatinos com seis blocos de esmalte humano (três hígidos para avaliação da desmineralização + três previamente desmineralizados para avaliação da remineralização) com dureza de superfície conhecida. Sacarose 20% foi gotejada oito vezes ao dia apenas sobre os blocos hígidos. Cinco minutos após cada gotejamento, os dispositivos eram recolocados na boca e os voluntários chupavam pastilha com xilitol 88,3% ou sorbitol 84,5%. A utilização das pastilhas iniciou-se uma semana antes de cada fase experimental. Foi usado dentifrício sem flúor. Ao final de cada fase, o biofilme formado sobre os blocos foi coletado e dividido para análises microbiológica e bioquímica, e os fragmentos de esmalte foram analisados quanto a variação de dureza de superfície antes e após o experimento. A porcentagem de perda de dureza de superfície dos blocos de esmalte do grupo do xilitol apresentou uma tendência a ser menor do que aquela observada no grupo do sorbitol, embora a diferença não tenha sido significante (p= 0,066; ANOVA). Também não houve diferença estatisticamente significante entre os grupos em relação à porcentagem de ganho de dureza de superfície e à maioria dos parâmetros bioquímicos do biofilme. As médias das concentrações de fósforo inorgânico e de polissacarídeo intracelular no biofilme no experimento de desmineralização foram significantemente menores (p< 0,001 e p= 0,007) no grupo do sorbitol. As porcentagens de estreptococos do grupo mutans (SM) em relação ao total de estreptococos (S) (p= 0,037) no experimento de desmineralização, assim como as contagens de SM (p= 0,035) e lactobacilos (p= 0,048), e as porcentagens de SM em relação ao total de microrganismos (p= 0,035) e em relação a S (p= 0,017) no experimento de remineralização foram significantemente menores no biofilme do grupo do xilitol. Os demais parâmetros microbiológicos não foram influenciados de maneira significante pelos tratamentos. O uso de pastilhas com xilitol por curtos períodos de tempo não apresentou vantagem nem em diminuir a desmineralização nem em favorecer a remineralização do esmalte em comparação ao uso de pastilhas com sorbitol, mas alterou a ecologia bacteriana do biofilme, reduzindo as contagens e as porcentagens de importantes grupos de microrganismos cariogênicos. / In spite of the existing knowledge about xylitol, its effect on the development of dental caries is still a subject that requires further clarifications. Thus, this randomized, double-blind, crossover in situ study aimed at assessing the effect of xylitol mints in the dental biofilm composition and in the processes of enamel demineralization and remineralization, in comparison to a control group using sorbitol mints. During the two phases of 14 days, 11 volunteers wore palatal appliances with six human enamel blocks (three intact ones for evaluation of demineralization and three demineralized ones for the evaluation of remineralization) of known superficial hardness. A solution of 20% sucrose was dripped only on the intact enamel blocks eight times per day. Five minutes after each dripping, the appliances were placed back inside the mouth and the volunteers took either an 88.3% xylitol mint or an 84.5% sorbitol mint. Both types of mints started being used by the volunteers one week before each experimental phase. Non-fluoridated toothpaste was used. At the end of each phase, the biofilm formed over the blocks was collected and divided for microbiological and biochemical analysis and the enamel fragments were evaluated in relation to surface hardness variation before and after the experiment. The percentage of surface hardness loss of the enamel blocks in the xylitol group tended to be lower than in those of the sorbitol group although this difference was not significant (p= 0.066; ANOVA). Moreover, there were no statistically significant differences between the study groups regarding the percentage of surface hardness gain or regarding the biochemical parameters of the biofilm. The average concentrations of inorganic phosphorus and of intracellular polysaccharides in the biofilm for the demineralization experiment were significantly lower (p< 0.001 and p= 0.007) in the sorbitol group. The following results were significantly lower in the xylitol group biofilm: percentages of mutans streptococci (SM) in relation to the total number of streptococci (S) (p= 0.037) in the demineralization experiment; SM (p= 0.035) and lactobacilli (p= 0.048) count; and the percentages of SM in relation to the total number of microorganisms (p= 0.035) and in relation to S (p= 0.017) in the remineralization experiment. Other microbiological parameters were not significantly influenced by the treatments. Taking xylitol mints during short periods of time did not show advantages regarding the decrease of enamel demineralization or the promotion of enamel remineralization when compared to taking sorbitol mints. However, it did expressively alter the bacterial ecology of the biofilm, reducing the percentage and count of important groups of cariogenic microorganisms.

Purpose: This in vitro study evaluated the effectiveness of using a 37% phosphoric acid liquid etchant along with MI Paste Plus™ powered technology compared to using MI Paste Plus™ alone or to an artificially created saliva solution in decreasing the demineralization and enhancing the remineralization of artificial carious lesions created on extracted human teeth. The teeth were analyzed and compared using polarized light microscopy, quantitative light-induced fluorescence, and digital photography. Materials and Methods: One hundred three recently extracted non-carious human third molar teeth without observable white-spot lesions, decalcification, or dental fluorosis were selected for this twelve day study and randomly divided into four treatment groups as follows: Group 1 (Control) - Artificial saliva solution (27 teeth) Group 2 (MIP) - MI Paste Plus™ application for 30 minutes daily for 12 days (26 teeth) Group 3 (15MIP) - 15 second etch every third day and MI Paste Plus™ application for 30 minutes daily for 12 days (25 teeth) Group 4 (1MIP) - 1 minute etch on day one ONLY and application of MI Paste Plus™ for 30 minutes daily for 12 days (25 teeth). Results: Results of one<–>way ANOVA revealed there was a significant effect for the type of treatment on the lesion depth (p = 0.0027). The post-hoc Tukey-Kramer's test indicated there was a statistically significant difference between the two groups (15MIP and 1MIP) that incorporated an acid etch in combination with MI Paste Plus™ and the group with exposure to MI Paste Plus™ alone (MIP). In addition, results of one<–>way ANOVA showed that there was no statistically significant effect for type of treatment on the change in fluorescence (p = 0.1417) or the change in density (p = 0.1934). Conclusions: The results of the present study revealed there was a significant effect for the type of treatment on the lesion depth (p = 0.0027). However, the only significant difference found was between the two groups (15MIP and 1MIP) that incorporated an acid etch in combination with MI Paste Plus™ and the group with exposure to MI Paste Plus™ alone (MIP). Thus, daily applications of MI Paste Plus™, with or without an acid etch, did not produce a statistically significant difference in mean lesion depth when compared to the control (artificial saliva group). In addition, the results of the present study showed that there was no statistically significant effect for type of treatment on the change in fluorescence (p = 0.1417) or the change in density (p = 0.1934). Further research is needed to evaluate MI Paste Plus™ capability in prevention of demineralization and/or enhancement of remineralization by conducting randomized clinical trials.

No description available.

Detection modalities that can evaluate the early stages of dental caries are indispensable. The purpose of this thesis is to evaluate the efficacy of photothermal radiometry and modulated luminescence (PTR-LUM) to non-destructively detect and quantify simulated enamel caries. Two experiments were performed based on the PTR-LUM detection mode: back-propagation or transmission-mode. Artificial demineralized lesions were created in human molars and a subset was further exposed to an artificial remineralizing solution. PTR-LUM frequency scans were performed periodically during de/re-mineralization treatments. PTR data was fitted to a theoretical model based on optical and thermal fluxes in enamel to extract opto-thermophysical parameters. Lesion validation was performed using transverse microradiography (TMR). Optical and thermal properties changed with the development and repair of the caries lesions while theory-derived thicknesses paralleled those determined microradiographically. These trends coupled with the uniqueness-of-fit of the generated parameters illustrate the efficacy of PTR- LUM to non-destructively detect and quantify de/re-mineralized lesions.

Detection modalities that can evaluate the early stages of dental caries are indispensable. The purpose of this thesis is to evaluate the efficacy of photothermal radiometry and modulated luminescence (PTR-LUM) to non-destructively detect and quantify simulated enamel caries. Two experiments were performed based on the PTR-LUM detection mode: back-propagation or transmission-mode. Artificial demineralized lesions were created in human molars and a subset was further exposed to an artificial remineralizing solution. PTR-LUM frequency scans were performed periodically during de/re-mineralization treatments. PTR data was fitted to a theoretical model based on optical and thermal fluxes in enamel to extract opto-thermophysical parameters. Lesion validation was performed using transverse microradiography (TMR). Optical and thermal properties changed with the development and repair of the caries lesions while theory-derived thicknesses paralleled those determined microradiographically. These trends coupled with the uniqueness-of-fit of the generated parameters illustrate the efficacy of PTR- LUM to non-destructively detect and quantify de/re-mineralized lesions.

Characterized by high levels of terrestrial organic carbon inputs, estuaries and coastal marshes are among the most productive ecosystems on earth and significantly impact the global carbon cycle. Unfortunately, rates of natural organic matter (NOM) degradation in these environments are difficult to quantify directly due to the complex interaction between microbial respiration processes and abiotic reactions in these sediments, yet estuaries and marshes are considered both net sources and sinks of carbon. Typically carbon remineralization rates are determined by measuring total (TOU) and diffusive (DOU) oxygen uptake fluxes assuming oxygen is the ultimate oxidant. This assumption, however, requires any reduced metabolites produced during microbial respiration to be reoxidized by oxygen. In this study, voltammetric sensors were used to measure terminal electron acceptors or their reduced by-products. By simultaneously considering oxygen as well as anaerobic respiration accepting processes, this study demonstrates that oxygen does not function as the ultimate oxidant in coastal marine sediments due to precipitation and burial of reduced species. Furthermore, the biogeochemistry of coastal sediments is typically investigated ex situ after collection of sediment cores. However, coastal sediments are subject to complex subsurface hydrological forcing that cannot be accounted for with ex situ measurements. Consequently, in situ approaches are required to better understand the impact of physical processes on sediment biogeochemistry, and two novel in situ voltammetric systems were developed as part of this research. First, a new autonomous benthic lander equipped with a benthic chamber to measure TOU fluxes with a high temporal resolution and a potentiostat and micromanipulator to simultaneously acquire voltammetric depth profiles of the main redox species in pore waters was deployed in a pristine river-fed estuary to characterize the seasonal variability of coastal sediment biogeochemistry and examine the impact of riverine discharge on carbon remineralization processes. Simultaneously, a new electrochemical analyzer equipped with a solar and wind power charging system to ensure continuous monitoring capability and a VHF radio to transmit data was operated remotely via the internet from the Georgia Tech campus to investigate the dynamic coupling between hydrological, chemical, and biological processes in intertidal marsh sediments. Finally, new microelectrodes were deployed in microbial mats to examine the chemical and biological oxidation of sulfide with submillimeter resolution. Typically, only biological processes are considered to oxidize sulfide in these environments. Depth profiles during diel studies were able to demonstrate the formation of thiosulfate as an intermediate oxidation product of sulfide oxidation, suggesting that the chemical oxidation of sulfide is much more prevalent than previously recognized when compared to biological oxidation. Overall, using a novel in situ sampling technique with high temporal resolution, these studies confirm that biogeochemical processes in coastal sediments vary seasonally. More importantly, these studies also reveal that estuarine sediments are significantly influenced by riverine discharge, demonstrate that the biogeochemical response of these sediments to natural perturbations is rapid, and indicate that respiration processes in continental shelf sediments are controlled by a combination of temperature, supply of inorganic and organic substrates, and hydrological processes, which has important implications regarding the effect of climate change on the biogeochemical cycling of carbon in these environments.

Thesis (M.S.D.)--Indiana University School of Dentistry, 2009. / Title from PDF t. p. (viewed Feb. 10, 2010) Advisor(s): Masatoshi Ando, Chair of the Research Committee, Carlos Gonzalez-Cabezas, Melvin Lund, Tien-Min Gabriel Chu, Michael Cochran. Curriculum vitae. Includes abstract. Includes bibliographical references (leaves 64-70).

There is an increasing awareness in clinical dentistry of the need to better understand the aetiology and management of tooth wear, as increasing numbers of elderly patients are retaining their natural teeth to a stage when they present with extensive wear. In addition, more younger patients are presenting with wear of both primary and permanent teeth. In order to comply with the philosophy of minimal intervention dentistry, clinical management of tooth wear should focus on early detection and prevention before a restorative approach is considered. Fluoride is a commonly used agent in the management of tooth wear, with previous studies showing that it can protect teeth against erosion (at around pH 2.0 and 3.0) and toothbrush abrasion in an acidic environment (at around pH 3.0). However, it does not reduce attritional wear between opposing tooth specimens. Nightguards are commonly used to prevent attritional wear but there is still a need to improve preventive strategies to manage the risk of erosive tooth wear. Previous in vitro studies have shown that a remineralizing agent in the form of CPP-ACP (casein phosphopeptide – amorphous calcium phosphate) can reduce erosion of both enamel and dentine by white wine. A recent study has also highlighted the potential lubricating and remineralizing properties of a CPP-ACP containing paste (Tooth Mousse®, G C Asia Pty Ltd) in reducing dentine wear in both an acidic environment (pH 3.0) and a near neutral environment (pH 6.1). In this context, it is desirable to investigate the effect of CPP-ACP on enamel wear under conditions simulating various clinical situations and to better understand the nature of third-body components at the wear interface. The aims of the present study were: (i) to determine the effect of CPP-ACP on enamel wear under conditions simulating three clinical situations: heavy attrition with gastric regurgitation (at pH 1.2); toothbrush abrasion after an erosive episode (at pH 3.2); and erosion from gastric regurgitation (at pH 1.2), and (ii) to clarify its mode of action by characterizing the enamel surface treated with CPP-ACP. Electro-mechanical tooth wear machines were used to simulate attrition and toothbrush abrasion in combination with erosion, but no machine was used in experiments investigation erosion alone. The effect of paste containing CPP-ACP in reducing erosive tooth wear was also compared with that without CPP-ACP. Enamel surfaces with and without treatment with CPP-ACP were then characterized by using Time of Flight – Secondary Ion Mass Spectrometry (ToF-SIMS). CPP-ACP was found to reduce enamel wear under conditions simulating heavy attrition combined with gastric regurgitation, and toothbrush abrasion after an erosive episode. However, it did not protect enamel from erosion under conditions simulating gastric regurgitation alone, indicating that its lubricating effect was more pronounced than its remineralizing effect. Silicone and ethyl siloxane were present in trace amounts on the enamel surface treated with Tooth Mousse®, thus they were found to be included in its formulation. These findings imply that CPP-ACP nanocomplexes and silicon can act as third body components to lubricate the wear interface. The findings presented in this thesis have implications for clinical management of tooth wear and may lead to new strategies of tooth wear prevention. Although some caution is needed in extrapolating these findings to the in vivo situation, it should be noted that in vitro studies provide valuable insights into separate components of the tooth wear process that are often difficult to distinguish in clinical situations. Overall, this thesis provides new information about the role of CPP-ACP in reducing erosive enamel wear and provides a basis for future experimental and clinical studies focussing on tooth wear prevention. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1379897 / Thesis (Ph.D.) -- University of Adelaide, School of Dentistry, 2009

Thesis (M.S.)--University of Michigan, 1987.