O objetivo do presente estudo é a avaliação do programa de bochechos de solução de fluor realizada pela Divisão de Estudos, Normas e Programas do Departamento de Assistência ao Escolar da Secretaria de Educação do Estado de São Paulo. A análise consistiu em se observar a atuação do ministrador do bochecho, verificando-se conjuntamente o preparo da solução e o tempo de duração do mesmo, a quantidade da solução e a freqüência do bochecho proporcionado aos escolares, além da incidência de cárie ocorrida desde o início até o final das observações, comparando-a através da aplicação do índice CPOS com a incidência ocorrida com escolares nos quais o bochecho foi rigorosamente controlado. A ausência de prevenção verificada torna evidente que o método não está sendo executado corretamente. / The present study comprehends an evaluation of a program of fluoride solution mouthrinsing application worked out by the Branch of study, Norms and Programmes of the Schoolchild Assistance Division of the Sao Paulo State Department of Education, Brazil. The analysis has comprised the observation of the performance of the persons in charge of the mouthrinsing ministration, taking into account lenght of time spent, the quantity and concentration of solution and frequency of mouthrinsing offered to schoolchildren, besides the incidence of caries occurred since the beginning till the end of the observations, comparing this incidence - through the application of the CPOS index - to trat occurred in school children with whom the mouthrinsing was completely controlled. The absence of prevention observed indicates that the method is not being correctly performed.

Polyvinylidene fluoride (PVDF) and its copolymer with trifluoethylene (PVDF-TrFE) have been widely investigated. This is largely attributed to their ferroelectric properties, which are present in a limited number of polymers. In comparison with the more widely used ferroelectric ceramics, the ease of their fabrication makes them attractive in flexible electronic devices. Despite many advances in their application, we are still lacking a complete fundamental understanding of the relationship between their structure and the functional properties. The melt-extrusion of PVDF revealed that the α-phase is predominantly formed in films. The ferroelectric β-phase PVDF was obtained by high temperature drawing of the α-phase of as-extruded films. It was observed that a minimum draw ratio of 3 is required to generate the β-phase. Chain mobility is crucial to the formation of β-phase. Too high chain mobility when drawing at temperatures above 100 °C can only orientate the pre-existing α-crystals without making the chain conformation change to form the β-crystals. Furthermore, the comparison between the produced α- and β-PVDF films is summarized. The α-PVDF films crystallized into spherulites with random orientation, while β-PVDF films displayed fibriliar structure showing preferred orientation of the polymer chains along the drawing direction. The overall crystallinity obtained from DSC data hardly varied, however, the drawn β-PVDF films had a lower melting temperature, which was also confirmed from the dielectric temperature spectra. The drawn β-PVDF films showed higher dielectric constant and larger remnant polarization compared with the as-extruded α-PVDF films, which is mainly ascribed to their higher β-phase content and preferred orientation. Highly aligned PVDF-TrFE films were processed using a melt extrusion processing route. Crystalline structure and orientation were optimized by controlling the melt extrusion conditions. XRD patterns suggested that there was nearly perfect alignment of the c-axis (polymer chain direction) along the extrusion direction in the optimized as-extruded films. SEM analysis confirmed the morphology of the crystalline phase, showing edge-on lamellae stacked perpendicular to the extrusion direction. DSC data indicated high crystallinity and well-ordered ferroelectric structure of the extruded films. FTIR spectroscopy revealed strong intermolecular dipole-dipole interaction in the extruded films. Accordingly, the optimized as-extruded PVDF-TrFE films exhibited a coercive field of 24 kV/mm, half of the commonly reported values for bulk films (~ 50 kV/mm) and a remnant polarization of 0.078 C/m2 which further increased to 0.099 C/m2 after annealing. This value is close to the theoretical limit (0.102 C/m2) assuming perfect in-plane c-axis orientation and 100% crystallinity. The typical limitations of PVDF - low crystallinity and indirect ferroelectric β-phase crystallization - and PVDF-TrFE - higher materials and processing costs and a low Curie point - are tackled by a simple and industrially viable melt blending approach. Despite the immiscible nature of PVDF and PVDF-TrFE, strong interactions exist between the two polymers when co-melt processed, which substantially affect the morphology and texture of the blends as well as their dielectric and ferroelectric properties. Surprisingly, minor amounts of PVDF-TrFE led to a significant increase in the β-phase content and preferred orientation of PVDF, well beyond the rule-of-mixtures. Moreover, the blends exhibited maximum increases in the dielectric constant of 80% and 30%, respectively compared with pure PVDF and PVDF-TrFE. The ferroelectric remnant polarization increased from 0.040 to 0.077 C/m2, while the coercive field decreased from 75 to 32 kV/mm with increasing PVDF-TrFE from 0 to 40 wt. %. The enhancement of properties is explained by the strong interactions at the interfaces between PVDF and PVDF-TrFE, which also suppresses the Curie transition of PVDF-TrFE, providing a potentially increased working temperature range for blended films, which is important in applications like non-volatile energy storage devices, ferroelectric field-effect transistors and touch sensors. Ferroelectric composites, integrating dielectric ceramic fillers with mechanically flexible polymers, are promising materials for flexible electronic applications. Numerous research works have demonstrated enhanced dielectric and ferroelectric properties of composite materials. However, the mechanisms responsible for these enhancements are not completely understood. Herein, PVDF and BaTiO3 (BTO) were used to study the effect of dielectric filler on the crystallization, phase transformation and dielectric properties of PVDF. The crystallization of α-PVDF was not affected by the presence of BTO particles, but small amounts of BTO (< 3 vol. %) made PVDF crystallize into larger spherulites. This is linked to crystallization kinetic studies, which showed that BTO acted as a nucleation agent for large full ring banded spherulites when its content was less than 1 vol. %. Furthermore, solid state drawing in the presence of BTO particles promoted the formation of β-PVDF with more pronounced crystalline orientation at high drawing temperatures (120 °C). The dielectric and ferroelectric properties were enhanced with BTO filling. The 100 °C oriented drawn PVDF tape exhibited a dielectric permittivity of 14 (100 Hz) and remnant polarization of 0.080 C/m2 (10 Hz), which increased to 20 and 0.095 C/m2, respectively, after filling with 5 vol. % BTO; neither resulting in high dielectric loss tangent (~ 0.02) nor obvious current leakage. Moreover, the coercive field decreased from 80 to 50 kV/mm with increasing BTO content from 0 to 5 vol. %.

Magister Chirurgiae Dentium - MChD / To compare the efficacy of two fluoride containing materials, namely, FluorSure and Duraphat, in protecting the enamel around and underneath the orthodontic brackets against decalcification. / South Africa

O objetivo do presente estudo é a avaliação do programa de bochechos de solução de fluor realizada pela Divisão de Estudos, Normas e Programas do Departamento de Assistência ao Escolar da Secretaria de Educação do Estado de São Paulo. A análise consistiu em se observar a atuação do ministrador do bochecho, verificando-se conjuntamente o preparo da solução e o tempo de duração do mesmo, a quantidade da solução e a freqüência do bochecho proporcionado aos escolares, além da incidência de cárie ocorrida desde o início até o final das observações, comparando-a através da aplicação do índice CPOS com a incidência ocorrida com escolares nos quais o bochecho foi rigorosamente controlado. A ausência de prevenção verificada torna evidente que o método não está sendo executado corretamente. / The present study comprehends an evaluation of a program of fluoride solution mouthrinsing application worked out by the Branch of study, Norms and Programmes of the Schoolchild Assistance Division of the Sao Paulo State Department of Education, Brazil. The analysis has comprised the observation of the performance of the persons in charge of the mouthrinsing ministration, taking into account lenght of time spent, the quantity and concentration of solution and frequency of mouthrinsing offered to schoolchildren, besides the incidence of caries occurred since the beginning till the end of the observations, comparing this incidence - through the application of the CPOS index - to trat occurred in school children with whom the mouthrinsing was completely controlled. The absence of prevention observed indicates that the method is not being correctly performed.

The supply of drinking water in Gokwe District (NW Zimbabwe) is almost entirely based on groundwater drawn from boreholes and open dug wells. In certain areas of the district, the occurrence of dental fluorosis has been linked to excessive fluoride in the water supplies. A high prevalence of dental fluorosis (about 62%) was previously recorded among school children in the district. The aim of this study was to determine relationships between the spatial distribution of fluoride content in drinking water supplies in Gokwe, and lateral and vertical geological variation. A total of 224 water samples were collected from 196 water sources in the study area (a further 18 water sources just outside the study area were also sampled). All the samples were analysed for fluoride in the field using the fluoride ion selective electrode method (FISE). One hundred and fifty nine duplicate samples were analysed for fluoride and common anions and cations using High Performance Ion Chromatography (HPIC) in the laboratory. Two main groups of computer programmes were employed: (1) Geographic Information System (ArcView® GIS) was used to store, analyse and display multiple layers of surface geologic and geographic information, and (2) a three-dimensional visualisation programme (Rockworks) was used to interpret and illustrate site stratigraphy based on borehole information. Results indicated that the fluoride content of drinking water in the study area ranges from 0 to 9.65 mg/L. Forty-seven water sources (24%) yielded water containing fluoride in excess of the World Health Organisation's (WHO) health limit of 1.5 mg/L F. Of the 47 high fluoride water sources, 43 were boreholes (pumped or artesian). The shallower water sources (dug wells, streams and dams) largely yielded low-fluoride water. / The groundwater fluoride contamination is stratigraphically controlled and originates from carbonaceous material (carbonaceous shales, carbonaceous mudstones and coaly material) within the Lower Madumabisa and Middle Wankie Members of the Lower Karoo Group. It has been shown that in general the greater the proportion of carbonaceous material intersected by a borehole, the greater the fluoride concentration of the water. Probable mineral sources of fluoride within the carbonaceous material include fluorapatite, kaolinite and trona. Chemical parameters that appear to influence the concentration of dissolved F in the water supplies include total dissolved solids (TDS), NaCl and pH. In relatively low fluoride waters, F concentrations generally increase with TDS and NaCl concentrations, whereas the highest F concentrations are found in moderately alkaline (pH 7.8-9) waters. Based on ranges of fluoride concentration in drinking water, fluorosis-risk zones were identified and have been illustrated on a fluorosis-risk map. The zones are: No Risk Zone (0-1.5 mg/L F), Moderate Risk Zone (1.5-3.0 mg/L F), High Risk Zone (3.0-6.0 mg/L F) and the Very High Risk Zone (6.0-10.0 mg/L F). The map suggests that groundwater available to people occupying 3650 km z (60.8%) of the study area potentially contains excessive fluoride (F>1.5 mg/L), presaging the occurrence of dental fluorosis, skeletal fluorosis and crippling skeletal fluorosis in the area. Different strategies may be employed to ameliorate the fluoride problem in Gokwe. / These include sinking new boreholes to optimal depths and in appropriate locations, promoting the use of surface water and shallow groundwater, resettlement and defluoridation. However in order to fully understand the problem and to prescribe these or other solutions more comprehensively, multi-disciplinary studies may be required. Such studies may consider isotopic dating of water to investigate any relationships between fluoride concentration and residence time of water, geochemical analyses of rocks and soils, detailed fluorosis epidemiology studies and test-scale defluoridation investigations.

<p>To compare the efficacy of two fluoride containing materials, namely, FluorSure and Duraphat, in protecting the enamel around and underneath the orthodontic brackets against decalcification.</p>

Zugl.: Berlin, Humboldt-Univ., Diss., 2009

Some community water systems using sources containing elevated levels of fluoride, in the United States and worldwide, struggle to treat their drinking water to healthy fluoride concentrations. Many treatment plants in the U.S. currently use aluminum based salts, such as aluminum sulfate and polyaluminium chloride, as coagulants during conventional treatment for removal of particles from drinking water sources. Moreover, enhanced aluminum sulfate, or alum, coagulation requires higher concentrations of aluminum added to the process and has been shown to be effective for removal of disinfectant byproduct precursors, i.e., natural organic matter (NOM). The presence of fluoride may interfere with the formation of aluminum hydroxide precipitates, and interrelationships among NOM, aluminum precipitation and fluoride removal are not well understood. A fundamental understanding of how fluoride alters the properties of aluminum precipitates and how fluoride and NOM molecules compete as ligands interacting with soluble aluminum species is lacking. As a result, the development of guidelines for implementation and optimization of a treatment scheme that uses aluminum in the presence of fluoride requires a multi-faceted approach in which the development of a mechanistic understanding of these interactions is conducted in concert with macroscopic experiments to identify optimum conditions for simultaneous removal of fluoride and NOM. To date, little research has looked at the efficiency of removing both fluoride and organics from the perspective of the precipitation process. To provide a foundation for revising treatment techniques, this research evaluated the effect of co-precipitating aluminum in the presence of fluoride, organics, and in multi-ligand systems to characterize the solid precipitate and removal competition. This research verified the formation of a co-precipitate in the presence of fluoride and certain low molecular weight organics. Co-precipitation from organics and fluoride competes for removal, especially at low alum coagulant doses, complicating treatment for resource limited areas. / text

No description available.

<p>To compare the efficacy of two fluoride containing materials, namely, FluorSure and Duraphat, in protecting the enamel around and underneath the orthodontic brackets against decalcification.</p>