Dental erosion has been defined as a chemical process that involves the dissolution of enamel and dentine by acid(s) not derived from bacteria when the surrounding aqueous phase is under-saturated with tooth mineral. Clinically however, dental erosion hardly ever occurs exclusively from the other modes of tooth wear such as abrasion and attrition. Hence the term erosive wear has been proposed and used to describe erosion-facilitated wear.With the prevalence of erosive wear being reported to be on the rise among children and adolescents in many countries, a plethora of oral health products such as dentifrices and mouth rinses had been put forward with claims of increasing the resistance of the enamel and / or dentine from being demineralised. However, the efficacy of these oral health products is still widely questionable as the studies carried out were mainly in vitro and / or in situ studies and the contradictory results were reported by different groups of researchers.The above mentioned discrepancies are often due to non-standardised in vitro and in situ study designs of erosion studies. Parameters such as type of acid used, concentration of acid used, duration of acid exposure, inclusion or exclusion of abrasion in the study model, ex vivo or in vivo acid challenge, ex vivo or in vivo treatment with oral health product and the nature of pellicle on the specimen are often varied.The availability of an detection tool which could be used to measure demineralisation on natural tooth surface in vivo would exclude many of the inevitable variability in in situ and in vitro study design, such as the simulation of the intra oral conditions in which the erosion challenge and intervention take place and the nature of the pellicle formed on the specimens. Hence with an in vivo detection tool, it is hopeful that the efficacy of any interventions would be evaluated more accurately and its results expounded to a wider context. It would be useful if the tool was sensitive to the very early stages of the erosion process as this would entail shorter and more economical study designs. Arising from the problems discussed above, potential non-invasive assessment methods that could be used clinically to measure demineralisation were explored and it was found that two optical methods, Optical Coherence Tomography (OCT) and Quantitative Light-induced Fluorescence (QLF) were potential methods for the tasks.The studies described in this thesis were divided into three main big sections; the first being the in vitro validation work of the two optical methods (Chapter 5 and 6), the second, validation of these methods in situ (Chapter 7) and finally the assessment of the efficacy of a high fluoride dentifrice on early enamel erosion using these two methods (Chapter 8).In the in vitro validation (Chapter 5), it was demonstrated that both QLF and OCT were able to detect erosion-interval related changes in natural surface samples eroded with orange juice for 60 minutes. However, results of Multiple Linear Regression and Paired t test suggest that QLF was more sensitive than OCT in the detection of demineralisation changes in this particular experimental setting. QLF demonstrated a R2 value of 0.590 while the best of the OCT outcome measure demonstrated a R2 value of 0.319.Further in vitro study (Chapter 6) was performed to explore the use of a moistened-exposed surface as a reference method for both OCT and QLF as it was felt that it would be beneficial if a coated reference area which posts as an additional step for error could be done away with. Results of this study showed that the moistened-exposed surface could be used a reference method for QLF only but not for OCT. Furnished with the findings of the above mentioned in vitro validation studies, an in situ validation of both the optical methods was performed (Chapter 7). It was found that OCT and QLF were able to longitudinally measure in situ demineralisation on polished and natural surfaced enamel which were subjected to 150 minutes of in vivo exposure to orange juice. Similar to the results of the in vitro study, QLF was found to be more sensitive than OCT in the detection of demineralisation changes on natural surfaced enamel. The last in situ study (Chapter 8) was to evaluate whether there was a protective effect of treating human enamel with a high-concentrated fluoride dentifrice during an active erosion phase and whether OCT and QLF were able to detect the protective effect. It was found that treating natural surface enamel with a 5000ppm NaF dentifrice increased its resistance against concurrent in vivo erosive challenge with an orange juice challenge. QLF was able to detect the protective effect of the 5000ppm NaF dentifrice on natural surface enamel against early in vivo erosion with an orange juice challenge regime while OCT did not.

La réalité d’amélioration de la qualité par le design de procédé (QdB) ainsi que l’apprentissage et le contrôle des variables critiques devient de plus en plus prédominant dans le milieu pharmaceutique. En effet, les risques associés à la mentalité d’analyse traditionnelle sur le produit fini uniquement et l’avènement des techniques d’analyse de procédés (PAT) ouvrent la voie à un contrôle plus complet et en temps réel de la qualité, tel que recommandé par les instances règlementaires. Ceci implique des économies d’échelle pour l’industrie étant donné la réduction des efforts (temps et argent) associés à l’analyse laboratoire par les techniques conventionnelles. Les appareils spectroscopiques constituent une technologie très utile pour l’analyse d’une formulation étant donné qu’ils sont généralement non-invasifs et non-destructifs. Dans le cadre de ce projet de recherche, il sera question de l’évaluation et du développement de la technique light-induced fluorescence spectroscopy (LIFS) afin de déterminer en-ligne la faible concentration d’un ingrédient actif dans une étape de mélange. Pour se faire, il sera tout d’abord nécessaire d’établir des modèles de calibration et d’évaluer l’impact des facteurs environnementaux et physico-chimiques sur les performances de ceux-ci, ainsi que sur le phénomène de photoblanchiment. Suite à une analyse de sensibilité, il sera possible d’élaborer un modèle optimisé et robuste. La méthodologie pour atteindre ces objectifs est la suivante : détermination des longueurs d’onde d’opération (excitation et émission); acquisition de spectres en mode dynamique, mais aussi en mode statique en faisant varier les paramètres de concentration, d’humidité, de taille de particule et de pression appliquée; traitement des données par analyse multivariée; établissement d’un modèle de calibration et validation de celui-ci par des essais à l’échelle pilote. La technologie LIFS, mais surtout son utilisation comme PAT, est très novatrice. De plus, les instruments développés antérieurement n’ont pas donné les résultats escomptés, ce qui renforce la pertinence de continuer les efforts de développement. Plus encore, le phénomène de photoblanchiment est encore mal défini et très peu d’études ont été faites sur des mélanges de poudres. En établissant de façon claire l’impact des différents facteurs sur la justesse, la précision, la répétabilité et la robustesse du modèle et de l’appareil, il sera possible de développer une technologie fiable permettant de quantifier des molécules fluorescentes en faible concentration dans un mélange particulaire.

Les Céramiques Ultra-Haute Température (UHTC) sont des matériaux prometteurs dans le cadre d'applications en conditions extrêmes comme les parties proéminentes de véhicules à rentrée atmosphérique ou les chambres de combustion de moteurs aéronautiques. La compréhension des mécanismes d'oxydation à haute température présente donc un intérêt majeur, car les réactions en milieu oxydant limitent fortement leur durée de vie. Les matériaux ZrB2-SiC, HfB2-SiC et HfB2-SiC-Y2O3 ont été soumis pendant des durées et températures variables (jusqu'à 2400°C) à des environnements contrôlés contenant de la vapeur d'eau. Les microstructures formées ont été décrites, et les mécanismes et cinétiques d'oxydation régissant leur comportement ont été analysés. L'importance de la stabilité et de la nature de la phase vitreuse formée durant l'oxydation a été soulignée. En complément de ces analyses microstructurales, une campagne d'essais utilisant la Fluorescence Induite par Laser (LIF) a permis, via la détection in situ de la molécule BO2, de comprendre plus finement la dynamique de la phase vitreuse lors de l'oxydation. Enfin, une modélisation de la croissance de couches oxydées sur un matériau monophasé a été effectuée. / Ultra-High Temperature Ceramics (UHTC) are promising materials for applications in extreme environments such as prominent parts of atmospheric re-entry vehicles or the combustion chambers of aeronautic engines. The understanding of oxidation mechanisms at high temperature is of great interest, because reactions in oxidizing atmosphere strongly shorten their lifetime. ZrB2-SiC, HfB2-SiC and HfB2-SiC-Y2O3 materials have been subjected to controlled water vapor-containing environments for different durations and temperatures (up to 2400°C). The microstructures developed by the oxidized materials have been described, and oxidation mechanisms and kinetics governing their behavior have been analyzed. The importance of the stability and nature of the vitreous phase formed during the oxidation has been emphasized. In order to complement these microstructural analyses, tests using Light-Induced Fluorescence (LIF) have been performed, allowing us to finely understand the dynamics of the vitreous phase during oxidation thanks to the in situ detection of the BO2 molecule. Finally, a modelling of the growth of oxidized layers on a single-phased material has been performed.

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A significant level of research is currently being carried out in the development of driver support systems as they are expected to play a key role in minimizing road vehicle accidents and creating a safe driving environment under harsh weather conditions. However, the performance of some components used by existing driver support systems like LIDAR and visual cameras are affected by extreme weather conditions such as heavy rain fall and snow. Therefore, it is paramount to identify key locations in an automotive vehicle where such systems are least affect by external weather conditions, thereby, improving their overall performance. The field of research that deals with such questions from a simulation perspective is called contamination modeling. At the moment, one of the biggest knowledge gaps in this field is how to consider the effect of different materials on the movement of liquids such as water on different automotive surfaces like glass, plastic, rubber and painted metal. The work presented in this research study has been carried out to investigate and establish the most suitable simulation strategies to match numerical predictions with experimental data for flow of water over different automotive surfaces. Following a comprehensive parametric study of simulation parameters, it was found that the most suitable model that can be tweaked to achieve different flow properties with different surfaces is a dynamic contact angle model. The Blended Kistler model available in STAR-CCM+ required specific values for static, advancing and receding contact angles to optimize a surface for a given material. Therefore, droplet experiments of two droplet sizes were initially carried out for all tested materials at different inclinations and necessary flow parameters were recorded. All experiments were carried out using an approach known as light induced fluorescence imaging where the captured images provided a very convenient method for post processing in computational software. Results from droplet experiments showed that water moved quickest on plastic and slowest on glass. Static contact angle measurements were carried out first on horizontal surfaces. Afterwards, the surface was inclined at 15, 30, 45, 60, and 75 degrees to measure changes in contact angle and velocities. The surfaces for glass and painted metal were directly taken from the door of a Volvo S60 while a separate surface was used for plastic and rubber. These results were then used to create simulation setups for rivulets in STAR-CCM+ with the multiphase modeling approach known as volume of fluid. Rivulet simulations were carried out for all four materials at five different inclinations and the results were compared and validated with experimental data. The results show good correlation between numerical predictions for rivulet movement and experimental data emphasising on the possibility of fine-tuning the surfaces of a simulation setup to represent different material properties.

Indiana University-Purdue University Indianapolis (IUPUI) Indiana University School of Dentistry Master Degree Thesis. / Detection of caries at an early stage is unequivocally essential for early preventive intervention. Longitudinal assessment of caries lesions, especially under the opaque preventive sealant, would be of utmost importance to the dental community. OBJECTIVES: The aim of this two-part in-vitro study is to evaluate the performance of multiple detection methods: The International Caries Detection and Assessment System (ICDAS); two quantitative light-induced fluorescence systems QLF; Inspektor™ Pro and QLF-D Biluminator™2 (Inspektor Research Systems B.V.; Amsterdam, The Netherlands); and photothermal radiometry and modulated luminescence (PTR/LUM) of The Canary System® (Quantum Dental Technologies; Toronto, Canada). All these are to be evaluated on their detection of caries on posterior human permanent teeth for 1) of primary occlusal lesions, and 2) under the sealant of primary occlusal lesions. METHODS: One hundred and twenty (N = 120) human posterior permanent teeth, selected in compliance with IU-IRB “Institutional Review Board” standards, with non-cavitated occlusal lesions ICDAS (scores 0 to 4) were divided into two equal groups. The second group (N = 60) received an opaque resin dental sealant (Delton® Light-Curing Pit and Fissure Sealant Opaque, Dentsply, York, PA). All lesions were assessed with each detection method twice in a random order except for ICDAS, which was not used following the placement of the sealant. Histological validation was used to compare methods in regard to sensitivity, specificity, % correct, and the area under receiver- operating characteristic curve (AUC). Intra-examiner repeatability and inter-examiner agreement were measured using intraclass correlation coefficient (ICC). RESULTS: 1) Of primary occlusal lesions, sensitivity, specificity, and AUC values were respectively: 0.82, 0.86 and 0.87 (ICDAS); 0.89, 0.60 and 0.90 (Inspektor Pro); 0.96, 0.57 and 0.94 (QLF-D Biluminator 2); and 0.85, 0.43 and 0.79 (The Canary System). Intra-examiner repeatability and inter-examiner agreement were respectively: 0.81 to 0.87: 0.72 (ICDAS); 0.49 to 0.97: 0.73 (Inspektor Pro); 0.96 to 0.99: 0.96 (QLF-D Biluminator 2); and 0.33 to 0.63: 0.48 (The Canary System). 2) Of primary occlusal lesions under the opaque dental sealants, sensitivity, specificity, and AUC values were respectively: 0.99, 0.03 and 0.67 (Inspektor Pro); 1.00, 0.00 and 0.70 (QLF-D Biluminator 2); and 0.54, 0.50 and 0.58 (The Canary System). Intra-examiner repeatability and inter-examiner agreement were respectively: 0.24 to 0.37: 0.29 (Inspektor Pro); 0.80 to 0.84: 0.74 (QLF-D Biluminator 2); and 0.22 to 0.47: 0.01 (The Canary System). CONCLUSION: Limited to these in-vitro conditions, 1) ICDAS remains the method of choice for detection of early caries lesion due to its adequately high accuracy and repeatability. QLF systems demonstrate potential in longitudinal monitoring due to an almost perfect repeatability of QLF-D Biluminator 2. The Canary System performance and repeatability were not acceptable as a valid method of early caries detection. 2) None of the methods demonstrated acceptable ability in detecting of occlusal caries under the opaque sealant. However, QLF-D Biluminator 2, with limitation to these in-vitro conditions and Delton opaque sealant, demonstrated a fair accuracy AUC (0.70) in detecting of caries under sealants at an experimental threshold of 12.5% ΔF.