Dissertations / Theses on the topic 'Fluoride release'

A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry. Objectives: To determine the amount of initial fluoride release from four orthodontic bonding systems over a period of four weeks, and then to subject these materials to an external source of fluoride for recharge in order to measure the amount of fluoride re-release over another four-week interval. Additionally the surface morphology of these materials was analyzed under the scanning electron microscope in order to identify microscopic changes in the materials that may have occurred during the experiment. Methods: Four orthodontic adhesives: Fuji Ortho LC (GC America, Alsip, IL), Transbond XT (3M Unitek, Monrovia, CA), Illuminate Light Cure (Ortho Organizers, Carlsbad, CA), and Opal Seal with Opal Bond MV (Ultradent, South Jordan, UT), n=120 (30/material) were tested for fluoride release at 1 hour, 24 hours, 3 days, 1 week, 2 weeks, 3 weeks and 4 weeks. Samples (10/subgroup/material) were then recharged with an external source of fluoride (toothpaste, foam, or varnish), and retested for fluoride re-release at 1 hour, 24 hours, 3 days, 1 week, 2 weeks, 3 weeks and 4 weeks. The scanning electron microscope was utilized in order to assess each material's surface morphology before testing and after completion of the experiment (n=16). Descriptive statistics, means and standard deviations were calculated for all four materials and their subgroups at each time interval. A mixed model two-way ANOVA was run, using a level of significance of 0.05. Bonferroni multiple comparison tests were conducted using if groups were found to be statistically significantly different. To determine significant differences between fluoride release and re-release for each recharge subgroup within each material group, paired t-tests were performed for the time intervals of 24 hours, 2 weeks, and 4 weeks. For the paired t-tests, the level of significance used was 0.02 to allow for Bonferroni correction. Results: During the initial 24 hours the fluoride measurements (in mg/L or ppm) were as follows: Fuji 9.78±0.65, Illuminate 7.83±1.49, Opal 0.05±0.02, and Transbond 0.01±0.0. At the initial four weeks time point, the readings were as follows: Fuji 6.68±0.79, Illuminate 3.82±1.84, Opal 0.06±0.01, and Transbond 0.01±0.01. The greatest fluoride release came from the varnish subgroups from each of the materials at 2 weeks post re-charge: Fuji 9.16±1.53, Illuminate 7.5±3.1 (tied with foam subgroup 7.5±4.4), Opal 5.3±2.45, and Transbond 3.75±1.67. The greatest fluoride measurement for each material at the final week post-recharge was: Fuji varnish subgroup 8.3±3.58, Illuminate foam subgroup 6.5±3.5, Opal varnish subgroup 2.50±1.1, and Transbond varnish subgroup 1.72±1.82. SEM results showed an observable difference between the materials pre-experiment and post-experiment at a magnification of 50X and 500X. The Fuji foam and paste subgroups displayed surface crackling patterns at both magnifications when compared to the control and varnish samples. The Illuminate control, foam, and paste specimens all had a roughened grainy appearance, while the varnish specimen seemed to be smoothed over by the varnish material. The Transbond samples appeared to have observable differences in surface morphology at 50X, but not at 500X. The Opal paste and foam specimens appeared to have a smoother surface than both the control and the varnish samples. Conclusions: There were significant differences in release and re-release of fluoride among all four adhesives at different time intervals over a period of eight weeks. Significant increase in fluoride re-release was seen for all three of the recharge subgroups for both Opal and Transbond at each time interval. A significant increase in fluoride re-release for the Illuminate group was mainly observed at the end of second and fourth week. Though no significant increase in fluoride re-release was observed, Fuji released highest amount of fluoride during release and re-release, at all different time intervals. Fluoride varnish was the superior recharge material, as it provided the greatest fluoride measurements, followed by foam and toothpaste. There were observable changes in the surface morphology of the materials pre-experiment and post-experiment at a magnification of 50X and 500X, which may have an affect on the fluoride releasing capabilities of the materials.

The development of aesthetically unattractive white spots is a concern for patients undergoing fixed orthodontic treatment. Due to poor oral hygiene during treatment, accumulation of plaque around orthodontic brackets causes bacterial fermentation reactions producing acids that dissolve the mineral enamel. Such dissolution results in white spot formation, an early sign of dental caries. In principal, to inhibit the appearance of these spots during treatment, fluoridated elastomeric o-rings might be employed. Once placed around brackets, these o-rings should release fluoride therapeutically for at least 30 days, after which the orthodontist may replace them. At the present time, such fluoride-releasing o-rings are not available. In this study, model materials for fluoride-releasing elastomeric o-rings were developed. These materials were fluoride-impregnated poly(ethylene-co-vinyl acetate) (PEVA) films. In vitro release studies of these films were conducted, assessing their capacity to deliver fluoride within therapeutic range (1.2 ≤ µg F/ring/day ≤ 51.4) for 30-45 days. Optimal sample and experimental parameters, including (1) fluoride loading in the film (wt% F), (2) overcoat thickness, and (3) temperature that provided therapeutic release, were determined. At 37°C, favorable release was observed for the following: (1) films with overcoat thickness of 0.14 mm and fluoride loadings of 3.9 wt% and 5.7 wt% and (2) films with overcoat thickness of 0.27 mm and fluoride loading of 5.7 wt%. These results are important in providing fundamental guidance for the development of o-rings that combat white spot formation among orthodontic patients.

Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 2017.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 187-197).
The Fluoride Salt-Cooled High-Temperature Reactor (FHR) is an advanced reactor concept, that uses molten-salt coolant and solid-uranium fuel composed of graphite and silicon carbide-encapsulated tri-structural isotropic (TRISO) particles. The primary coolant salt is known as flibe (7Li2BeF4), which was chosen for its desirable thermal-hydraulic and neutronic properties. Under irradiation, coolant salts containing lithium capture neutrons generating tritium in quantities that are several orders of magnitude larger than the amounts generated by existing light water reactors. Adsorption technology is proposed, using chemically compatible carbon materials for the capture and control of tritium in the FHR. Various nanoporous activated carbon, graphene and nuclear graphite materials have been characterized. This includes the determination of BET surface area, total pore volume, average pore size, and pore size distribution by performing low-temperature gas adsorption experiments and applying microscopic thermodynamic theory. In addition, morphological analysis was conducted with scanning electron microscopy. Hydrogen was used as a surrogate. Its chemisorption on these materials have been measured and modeled at the reactor conditions of 700°C and pressures under 4 kPa. Models suggest that the total measured solubility of hydrogen includes a combination of dissociative and molecular adsorption. Carbon materials containing larger volumetric fractions of micropores (width < 2 nm) generally exhibited a higher hydrogen capacity. Further, the presence of micropores was associated with a relatively weak and reversible form of hydrogen chemisorption. At 500 Pa, microporous carbon materials captured 50 times more hydrogen than graphite, which was previously known to be the largest hydrogen sink at reactor conditions. The coupled effects of generation, chemical speciation, adsorption and diffusion of tritium in the FHR system were simulated over 200 full-power days. It was found that an adsorption column using high-performance carbon-based catalyst adsorbed substantial amounts of tritium and reduced the peak release rate from 2400 Ci/day to 40 Ci/day for the 236 MWt FHR. Further, the total tritium inventory in the system decreased by more than 70%, from 68,400 Ci to 19,400 Ci. This demonstrates that adsorption technology can greatly reduce the risk of radiological release during normal operation and reactor transient events.
by Stephen Tsz Tang Lam.
S.M.

Enamel demineralisation or white spot lesions (WSLs) is a risk for all patients undergoing fixed appliance orthodontic treatment (FAOT) with no consensus with regards to prevalence, risk factors, prevention and treatment. Slow-release fluoride glass devices (SRFGDs) have been shown to clinically prevent caries without relying on patient’s compliance, therefore their effectiveness in preventing WSLs during FAOT was investigated. An in-vitro exploratory study investigated fluoride (F) and phosphate (PO4) release from different types of powder from SRFGDs incorporated into a composite resin bonding material. Samples were stored in artificial saliva and assessed with ion chromatography for up to six months. Three types of powder showed high F release to maximise caries prevention and low PO4 release to minimise degradation of powder. A questionnaire was emailed to orthodontists’ members of the British Orthodontic Society. For majority of responders the key factors to the problems related to WSLs are clinical examination, photographs, F, oral hygiene, diet and duration of FAOT. A double-blind, randomised clinical study with orthodontic patients randomly allocated to SRFGDs or placebo devices threaded onto the orthodontic wire was conducted. Cross-polarised digital photographs of the maxillary permanent central and lateral incisors and canines were taken for 63 subjects at the start and for 40 subjects at the end of the study. One examiner assessed photographs for presence and severity of WSLs. Majority of volunteers and the smallest number of refusals lived in the most deprived areas according to the Multiple Deprivation Index. Use of SRFGDs would decrease severity by preventing 2.88 times more teeth compared to use of 225 ppm F mouth-rinse once daily and 1,450 ppmF tooth-paste twice daily. Duration of FAOT and increased gingival index at the start of FAOT increased significantly the risk of developing WSLs. SRFGDs were effective in preventing teeth with WSLs during the course of FAOT.

Magister Scientiae Dentium - MSc(Dent) (Paediatric Dentistry)
The use of glass ionomer cement (GIC) restorative materials assists in the prevention of dental caries due to its long-term fluoride release. However, poor physical strength is one of the main drawbacks of GIC. A surface coating is recommended to improve the physical strength and is considered necessary during the overlapping stages of setting reactions of GIC restorative materials. The development of resin based coatings has improved the properties of the material but the effect on fluoride release needs investigation.

La presente tesis doctoral titulada ¿Supramolecular and heterosupramolecular chemistry in controlled release and molecular recognition processes¿ está centrada en los dos aspectos principales de la química supramolecular que han experimentado un gran auge en los últimos años: el reconocimiento molecular y los procesos de liberación controlada. En particular la primera parte de la tesis se focaliza en el diseño y síntesis de moléculas orgánicas que pueden ser empleados cómo sensores para especies aniónicas y neutras. El paradigma seleccionado para los procesos de reconocimiento molecular fue la aproximación del dosimetro químico. Esta aproximación presenta ventajas con respecto a los otros dos métodos de determinación de aniones (desplazamiento y unidad coordinanteunidad indicadora), cómo, por ejemplo, la posibilidad de determinar los analitos en disolución acuosa. Así se sintetizaron dos sensores selectivos, uno para el anión fluoruro (F-) y el otro para glutatión (GSH). El sensor selectivo para la determinación de F- está basado en un colorante azoico funcionalizado, en su ¿OH fenólico, cómo silileter. Esta molécula presenta una banda de absroción muy intensa centrada a 350 nm que, después de la adición de F- , sufre un efecto hipocrómico significativo y un desplazamiento batocromico ligero (de ca. 10 nm), mientras aparece una nueva banda a 470 nm, determinando un cambio de incoloro a amarillorojo. Para obtener un sensor selectivo para GSH se sintetizó una sonda químico basado en una sal de 2,6-difenilpirilio. Sucesivamente se preparó una disolución de este compuesto en agua/CTAB, que se caracterizaba por un intenso color azul. En este caso, la adición de GSH produce una disminución significativa de la banda del visible, acompañada por la consecuente decoloración. Además la adicón de GSH induce la aparición de Resumen vi una intensa banda de emisión centrada a 485 nm (después de la irradiación a 350 nm). La segunda parte de esta tesis doctoral se basa en el diseño y síntesis de nuevos sistemas híbridos orgánicos-inorgánicos para procesos de liberación controlada en ambiente celular. Estos materiales híbridos se componen en general, de dos unidades: una matriz inorgánica mesoporosa de base silícea, capaz de almacenar moléculas orgánicas (colorantes, farmacos...) y un compuesto orgánico anclado covalentemente a la superficie externa del soporte inorgánico mesoporoso, que actúa cómo puerta molecular. La aplicación de un estímulo externo puede modificar la conformación de la puerta molecular permitiendo o bien impidiendo la difusión de la carga almacenada en los mesoporos hacía el exterior (disolución o citoplasma). El primer sistema sintetizado y estudiado se compone de una matriz inorgánica mesoporosa (MCM-41), cargada con el colorante Ru(bipy)3 2+ y funcionalizada en la superficie con un oligoetilen glicol mediante un grupo ester. La adición de la enzima esterasa determinaba la hidrólisis del grupo ester y la consecuente reducción del tamaño de la puerta molecular, acompañada por la liberación del colorante previamente cargado. Otro sistema de liberación preparado consiste en el uso de la misma matriz MCM-41 nanoscópica y el mismo colorante Ru(bipy)3 2+, pero se funcionalizó la superficie con una puerta molecular fotolabil. La irradiación en el maximo de absorción de la puerta molecular inducía la fotodegradación de la misma y la consecuente liberación del colorante. Un tercer ejemplo de sistema de liberación consiste en una puerta molecular caracterizada por la presencia de dos grupos funcionales hidrolizables con enzimas diferentes: grupos urea y amida. vii El material final, caracterizado por la presencia del mismo esqueleto inorgánico, y cargado con Ru(bipy)3 2+, era capaz de liberar selectivamente cantidades distintas de colorante, dependiendo del enzima empleado. Así se podían conseguir dos tipos de perfiles de liberación: uno muy rápido y poco intenso y otro más lento pero mucho mas intenso. Finalmente se sintetizó un material híbrido siempre basado en la misma matriz de MCM- 41, cargado con rodamina-B y funcionalizado en la superficie con galactooligosacáridos. Con este material se podía conseguir una liberación controlada del colorante selectivamente en células senescentes, debido a que estas sobreexpresan el enzima ß-galactosidasa que es capaz de hidrolizar los galactooligosacáridos.
Agostini, A. (2013). Supramolecular and heterosupramolecar chemistry in controlled release and molecular recognition processes [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/29397
TESIS

Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains xi, 204 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references (p. 104-111).

Aim: To investigate the use of fluoride glass slow-release devices (FGSRD) for the prevention of dental erosion of human dental enamel in vitro. Methods: Human teeth (permanent and primary) were used for this study. Enamel slabs were randomly allocated to four study groups: Group 1: 24 permanent enamel slabs with FGSRD, Group 2: 24 permanent enamel slabs with placebo non-FGSRD, Group 3: 20 primary enamel slabs with FGSRD, Group 4: 20 primary enamel slabs with placebo non-FGSRD. The glass slow-release devices were randomised into two groups. Test and placebo groups were coded until the end of the study. The enamel slabs were dipped in a citric acid solution for two minutes five times daily for 28 days and brushed twice a day. This was to create the erosive environment for this in vitro study. The slabs were kept in artificial saliva and stored in an incubator at 37°C. The glass slow-release devices (fluoride and non-fluoride) were present in all containers. The surface profile was measured at baseline using surface profilometry and after 14 and 28 days of the cycling regime. Analysis: Simple t-tests were used to compare the permanent and primary teeth groups with 0.05 as the significance level and an ANOVA t-test with a Bonferroni correction to compare: primary and permanent teeth. Daily fluoride release of the FGSRD’s was measured. Results: For enamel of primary teeth, after 14 days 40% less erosion was observed in the F group which decreased to 31% at the end of the study period, i.e., 28 days. This was highly statistically significant (p < 0.001) at both time points. For permanent enamel, no significant differences were observed (p=0.091). Conclusion: FGSRD’s have great potential for protection of primary human enamel against erosive challenge in addition to a number of other uses.

Orientador: Luis Roberto Marcondes Martins
Dissertaçâo (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba
Made available in DSpace on 2018-07-27T13:31:40Z (GMT). No. of bitstreams: 1 Molleri_RobertoRogerio_M.pdf: 1902314 bytes, checksum: baf7ac5c1ec9610da04287a80787fb87 (MD5) Previous issue date: 2000
Resumo: Muitos estudos demonstram a liberação de fluoretos dos cimentos de ionômero de vidro modificados por resina e de resinas compostas modificadas por poliácidos. Os efeitos anticariogênicos dos fluoretos têm levado a sua incorporação em um grande número de materiais dentários. O objetivo deste estudo foi quantificar e comparar in vitro a liberação de fluoretos de três materiais restauradores, duas resinas compostas modificadas por poliácidos, e um cimento de ionômero de vidro modificado por resina, nos períodos de 1,4,7,10,15 e 21 dias. Foram confeccionados cinco corpos-de-prova cilíndricos, com medidas de 3 mm de altura por 6 mm de diâmetro utilizando uma matriz metálica pré-fabricada. Os corpos de prova foram mantidos em recipientes com 20 mL de água destilada e deionizada, na temperatura de 37 graus centígrados. A água foi trocada após cada medição. A análise da água foi realizada por um potenciômetro modelo 720 A, marca Orion (Cambridge, MA, USA), acoplado a um eletrodo seletivo para fluoretos, modelo 9609, marca Orion (Cambridge, MA, USA), que determinou a quantidade de fluoretos em partes por milhão. Os dados foram submetidos à análise de variância e teste de Tukey. O estudo demonstrou o mesmo padrão de liberação de fluoretos para os três materiais, pois todos apresentaram maior liberação nas primeiras 24 horas. Após o décimo dia houve estabilização na liberação para todos os materiais. A liberação de fluoretos nas resinas compostas modificadas por poliácidos se manteve menor e constante, se comparada ao cimento de ionômero de vidro modificado por resina, que apresentou valores médios maiores
Abstract: Many studies have shown the release of fluorides frem resin-modified glass ionomer and polyacid-modified composite resin. The anticariogenic effects ofthe fluoride ions have called for their use in a great number of dental materiais. The aim of this study was to evaluate and compare, in vitro, the fluoride release of three restorative materiais, the polyacid-modified composite resin and a resin-modified glass ionomer, in 1,4, 7, 10, 15, and 21 days. Five cylindrical samples were made, 3 mm high by 6 mm in diameter by using a pre-built metallic matrix. The samples were stored in 20 mL containers in deionized, distilled water, at 37°C. The water was replaced after each measurement. The water analysis was done by an Orion 720 A model potentiometer (Cambridge, MA, USA), attached to an Orion 9609 model selective electrode for fluorides (Cambridge, MA, USA), which determined the amount of fluorides in parts per milion. The study showed the same fluoride release pattern forthe three materiais, as ali ofthem presented a high release in thefirst24 hours. Afterthetenth day, there was a stabilization in the release for ali materials. The fluorides release in the 'polyacid-modified composite resin remained lower and constant, comparing to the resin-modified ionomer glass cement, which showed higher mean values
Mestrado
Mestre em Materiais Dentários

Magister Theologiae - MTh
This study aimed to determine the association between dimensional change and surface roughness (Ra) of Vitremer, Activa and Cention N after immersing them into two different media: acidic and artificial saliva media for the period of a year. Measurements were made at 10 time intervals during the observation period.

Neste estudo avaliou-se o efeito de diferentes protetores de superfície na liberação de flúor (LF) e na resistência à tração diametral (TD) de dois cimentos de ionômero de vidro (CIV) convencionais restauradores, Chemfil e Chemflex (Dentsply). Manipulou-se os cimentos segundo as recomendações do fabricante, os espécimes confeccionados foram divididos em cinco grupos: grupo1 sem protetor (controle); grupo2 vaselina sólida; grupo3 verniz (Cavitine, S.S.White); grupo4 verniz fluoretado (Duraflur, Denstply); grupo5 adesivo (Magic Bond, Vigodent). Confeccionou-se para o teste de LF 40 espécimes para cada CIV, com dimensões de 4 mm de diâmetro por 6 mm de comprimento, divididos aleatoriamente entre os grupos e estocados individualmente em potes plásticos contendo 5 ml de água deionizada. Registrou-se o nível de fluoreto no período de 04 horas, 24 horas, 03 dias, 07 dias e 14 dias após a confecção, em um analisador Expandable Íon Analyser EA 960, sendo os resultados calculados em μgF/ cm2. Confeccionou-se para o ensaio de TD 120 espécimes para cada CIV, com dimensões de 4 mm de diâmetro por 6 mm de comprimento, divididos aleatoriamente entre os grupos. Realizou-se ensaios mecânicos, com 1 dia e 14 dias após a confecção e estocagem individual dos espécimes em potes plásticos contendo 5 ml de água deionizada, em uma máquina universal de ensaios EMIC DL 500 MF, realizou-se um terceiro teste após 14 dias de ciclos de des-remineralização. Tratou-se estatisticamente os dados obtidos por ANOVA e por Student Newman-Keuls (p<0,05). No teste de LF os resultados demonstraram que o Chemfil liberou uma quantidade significantemente maior de flúor do que o Chemflex. Durante o período do teste a vaselina e o verniz tiveram um comportamento semelhante, mostrando uma menor LF do que o grupo controle nas primeiras 4 horas, com uma maior liberação na análise seguinte (24 horas). Os espécimes protegidos com vaselina e verniz, tiveram uma liberação de flúor semelhante ao grupo controle nos períodos de 3, 7 e 14 dias. O verniz fluoretado mostrou uma forte influência nas primeiras 24 horas. A partir da terceira análise observou-se uma maior liberação de flúor para o Chemfil em comparação com o Chemflex. Em relação ao emprego de um protetor superficial resinoso, encontrou-se tanto para Chemfil quanto para o Chemflex uma redução drástica na liberação de fluoreto, em todos os tempos analisados. No ensaio de TD o Chemfil não mostrou diferença estatisticamente significante quando os resultados de TD do seu grupo controle foram avaliados nos diferentes ensaios (24 horas, 14 dias e des-re), o mesmo acontecendo com o Chemflex. Ao se avaliar a influência dos diferentes protetores de superfície nos CIVs utilizados no presente trabalho observou-se que, para o Chemfil os protetores de superfície tiveram pouca influência no comportamento do material, se comportando na maioria das vezes de forma similar ao grupo controle. Em contrapartida, para o material Chemflex a utilização de um protetor de superfície, como o verniz fluoretado e o adesivo, permitiu maiores valores de resistência à TD. Conclui-se que quando se objetiva o uso do CIV por um curto período o Chemfil sem protetor parece ser o mais indicado, porém se o uso do CIV for por um longo período o Chemflex com a proteção do verniz fluoretado é o mais indicado.
This study evaluated the effect of different protective coatings on the fluoride release (FR) and on the diametral tensile strength (DTS) of two conventional restorative glass ionomer cements (GIC), Chemfil e Chemflex (Dentsply). The cements were manipulated according to the manufacturer's recommendation. The especimens were divided into five groups: group 1 uncoated (control group); group 2 petroleum jelly; group 3 dental varnish (Cavitine, S.S.White); group 4 - fluoride varnish (Duraflur, Denstply); group 5 dentin adhesive (Magic Bond, Vigodent). To the FR test were made 40 especimens to each CIV, with dimensions of 4mm in diameter by 6 mm in length divided randomly into the groups and kept individually in plastic containers with 5 mL of deionized water. The fluoride level was registered within 04 hours, 24 hours, 3 days, 7 days and 14 days after the confection in an Expandable Íon Analyser EA 960, and the results were calculated in μgF/ cm2. To the DTS test 120 especimens were made to each GIC, with dimensions of 4mm in diameter by 6mm in length divided randomly into the groups. Mechanical tests were made within 1 day and 14 days after the confection and saving of specimens individually in plastic containers with 5 mL of deionized water, in an universal tests machine EMIC DL 500 MF, and a third test was made after 14 days of des-remineralization cycles. The data was statistically treated by ANOVA and by Student Newman-Keuls (p<0,05). In the FR test the results showed that the Chemfil released a significant bigger amount of fluoride then the Chemflex. During the tests period, the petroleum jelly and the dental varnish had a similar behavior, presenting lower fluoride release then the control group in the first 4 hours, with a greater release in the second analysis (within 24 hours). The especimens protected by petroleum jelly and dental varnish had a fluoride release similar to the control group on the periods of 3, 7 and 14 days. The fluoride varnish showed a great influence in the first 24 hours. From the third analysis on, each ionomer materials characteristics became prominent, and was noticed a bigger fluoride release on the Chemfil in comparison to the Chemflex. In relation to the coated with dentin adhesive, there was a drastic decrease of fluoride release for Chemfil and Chemflex, in all of the analysis periods. In the DTS test Chemfil didnt show statistically significant difference when the diametral tensile strength of the control group was evaluated in the various periods of time (24 hours, 14 days and de-remineralization), which also happened to Chemflex. When evaluating the influence of different surface protectors on the GIC used at this study, it was noticed that for the Chemfil the surface coating had little influence on the materials behavior, having on most of the time, the same behavior as the control group. However, to the Chemflex material, the use of a surface coating such as the fluoride varnish or the dentin adhesive allowed bigger values of diametral tensile strength. The conclusion is that when the use of GIC is wanted for a short period of time the Chemfil uncoated seems the most indicated. However, if the period of use is longer, the Chemflex with the fluoride varnish protection is the most indicated.

Magister Chirurgiae Dentium (MChD)
Background: This study aimed to determine the association between dimensional change and surface roughness (Ra) of Vitremer, Activa and Cention N after immersing them into two different media: acidic and artificial saliva media for the period of a year. Measurements were made at 10 time intervals during the observation period. Methodology: This was a quantitative and qualitative study. For the quantitative part, a total of 60 specimens were tested, 20 specimens for each material. The 20 specimens were further divided into 10 specimens. Ten were immersed in acidic media and the rest in saliva media. A measurement of the weight, height, and Ra was carried out as follows: day 0, day 1, day 2, day 7, day 21, day 28, day 60, day 90, day 180 and day 365. Scanning electron microscopy (SEM) was used to examine the surface of each material qualitatively pre and post immersion in the two media. For fluoride measurements, an additional five samples from each material were left suspended in the de-ionized water by the use of dental floss. The materials were moved to new specimen jars after the completion of day 1, 2, 3, 4, 5, 6, 7, 14, 21 and 28. All the specimen jars had been kept for the fluoride measurements. Results: Non-parametric tests were used to analyze the data. Linear regression analysis was used to measure the association between weight, height or surface roughness (Ra) and immersion time for a year. The result of this test showed that Vitremer had a significant association between the weight (p = 0.000), height (p = 0.007) and Ra (p = 0.001) when it was immersed in acidic media. On the other hand, when Vitremer was immersed in saliva media, only the weight variable showed a significant association (p = 0.002). For Cention N, significant association was found for only Ra when immersed in acidic media (p = 0.000). Finally, for Activa, all the studied associations; the weight, height and Ra in both media were found to be insignificant. For saliva media, there was a significant weight change between the three materials during all 10 periods of time (p = 0.000). In the first six months, Cention N demonstrated a significant increase in weight changes followed by Vitremer, then Activa. Yet, after a year, the difference between Cention N and Vitremer became insignificant and Activa showed the least weight changes. There was not a significant difference between the materials in terms of height and Ra measurements. The fluoride experiment was not successful due to technical issues during pH measurements of the collected solutions. For comparison of the studied parameters between the three materials, the Kruskal-Wallis test was used. In acidic media, there was a significant difference between the materials in term of weight change in 10 periods of time (p = 0.000). In particular, after a two month period, Cention N had the highest weight, followed by Vitremer and then by Activa. The difference between Vitremer and Activa became insignificant throughout the rest of the experimental time frame. All the height measurements between the three materials were found to be insignificant except for day 365 (p = 0.048), where both Activa and Cention N were found to be significantly higher than Vitremer. For the Ra comparison, in the first two weeks, particularly day 1, 7 and 14, Cention N had significantly the lowest Ra among the other materials. As the three materials aged in the acidic media (day 180), Vitremer had significantly the highest Ra values. Cention N showed higher Ra values than Activa; nonetheless this difference was not significant. The SEM images showed loss of some particles in all post-experimental images of the materials in acidic media. Vitremer showed the widest cracks with the loss of fillers. In saliva media, there was also loss of particles but to a lesser extent than in acidic media. Yet, the post-experimental image of Activa in saliva resembled the pre-experimental one. Conclusion: Within the limitations of the study, the best material to resist Ra from prolonged acidic attack was Activa followed by Cention N and then Vitremer. Except for Vitremer, no significant changes in the Ra of the other materials were detected when the three materials were immersed in saliva media in the long term. In acidic media Vitremer tended to lose weight and height faster than Cention N and Activa over a year. Cention N is the best material to resist dimensional change. However, in artificial saliva Vitremer gained water rapidly. Activa did not absorb a lot of water and did not reject a lot of water; Activa demonstrated good dimensional stability and this property may be beneficial when compared to the other two materials tested. The clinical significance of the study: All the materials studied were subjected to dimensional and Ra changes following long-term exposure to acidic substances, but the newer materials (Cention N and Activa) seemed to be more dimensionally stable and resistant to Ra changes than the older, well-known material (Vitremer). This may influence a clinician’s choice of restorative material for use in pediatric dentistry.

O objetivo deste estudo foi avaliar o cimento de ionômero de vidro modificado por resina de nanopartículas Ketac™N100, por meio de três metodologias diferentes: resposta tecidual em subcutâneo de camundongos isogênicos, liberação de flúor e tensão de contração de polimerização, in vitro. Foram utilizados 90 camundongos isogênicos da linhagem BALB/c, divididos em 9 grupos (n=10), nos quais foram implantados tubos de polietileno contendo o Ketac™ 100, ChemFilR (ionômero de vidro convencional) ou tubo vazio. Nos períodos experimentais de 7, 21 e 63 dias o tubo e o tecido adjacente foram removidos para análise microscópica. Para o ensaio de avaliação da tensão de contração de polimerização, foram utilizados dois bastões de vidro fixados a uma máquina de ensaio universal. Nos bastões foi acoplado um extensômetro para medição da força de contração de polimerização de cinco materiais (Resina Filtek™Z350, CompoglassR F, VitremerMR, Ketac™N100 e ChemFilR), com 10 corpos de prova para cada material. Para o ensaio de liberação de flúor, foram confeccionados 8 corpos de prova de 3 diferentes materiais (Ketac™ 100, Vidrion R e Resina Filtek™ Z250), colocados individualmente em 1 ml de saliva artificial. O corpo de prova foi trocado a cada dia por 15 dias e a solução obtida utilizada para a leitura do íon fluoreto.Os resultados microscópicos evidenciaram que a inflamação presente na abertura dos tubos, aos 7 dias, sofreu uma diminuição em área e espessura até os 63 dias, nos 2 materiais e no grupo controle. Comparando a área da reação inflamatória o Ketac™N100 foi diferente estatisticamente do ChemFilR, nos períodos de 7 e 21 dias (p>0,05), com uma área menor para o Ketac™N100. A espessura da reação inflamatória nos períodos de 7 e 21 dias apresentou valores semelhantes entre o Ketac™N100 e ChemFilR (p>0,05). Aos 63 dias, os valores foram estatisticamente diferentes, com um pequeno aumento de espessura para o Ketac™N100. Os valores de tensão de contração de polimerização obtidos seguiram a seguinte ordem crescente: ChemFilR < VitremerMR < Ketac™N100 < CompoglassR F ~ Filtek™Z350 (p>0,05). Quando comparados dois a dois, o ionômero modificado por resina de nanopartículas Ketac™N100 se aproximou mais dos valores da resina Filtek™ Z350 (p>0,05) do que do ionômero de vidro convencional ChemFilR (p<0,05). A sua liberação de flúor ocorreu mais significativamente nos dois primeiros dias, com valores médios 33% menores em comparação ao Vidrion R. Concluímos que o ionômero resinoso nanoparticulado Ketac™N100 é um material que induz uma resposta inflamatória tecidual satisfatória em subcutâneo de camundongos isogênicos. Sua contração de polimerização foi menor do que de a resina Filtek™ Z350 e a liberação de flúor foi um terço menor do que a dos ionômeros convencionais.
The aim of this study was to evaluate the resin modified nano ionomer Ketac™N100, by three different methodologies: tissue response in of isogenic mice subcutaneous, fluoride release and shrinkage stress of polymerization in vitro. We used 90 isogenic mice (BALB / c), divided into 9 groups (n = 10), which were implanted with polyethylene tubes containing Ketac™ 100, ChemFilR (Ionomer conventional) or empty tube. In the experimental periods of 7, 21 and 63 days the tube and the surrounding tissue were removed for microscopic analysis. To evaluating the stress of contraction of polymerization, we used two glass rods attached to a universal testing machine. In the rods was attached to an extensometer to obtain the measure of the polymerization shrinkage strength of five materials (resin Filtek™Z350, CompoglassR F, VitremerMR F, Ketac™ 100 and ChemFilR), with 10 specimens for each material. In the fluoride release test, 8 specimens of 3 different materials (Ketac™ 100, Vidrion R and Resin Filtek™ Z250) placed individually in 1 ml of artificial saliva. The specimens were changed each day for 15 days and we use this solution used for reading the fluoride ion. The microscopic results showed that the inflammation in the opening of the tubes at 7 days decreased in area and thickness up to 63 days in 2 materials and the control group. Comparing the inflammatory reaction area, Ketac™N100 was statistically different from ChemFilR, in periods of 7 and 21 days (p> 0.05), with a smaller area for Ketac™N100. The inflammatory reaction in the periods of 7 and 21 days showed similar values between the Ketac™N100 and ChemFilR (p> 0.05). At 63 days, the values were statistically different, with a small increase in thickness to Ketac™N100. The values of polymerization shrinkage strength obtained after polymerization followed this ascending order: ChemFilR < VitremerMR F < Ketac™ 100 < CompoglassR F ~ Filtek™Z350 (p> 0.05). When compared two by two, the resin modified nano ionomer Ketac™N100 approached most of the values of resin Filtek™ Z350(p> 0.05) than the conventional glass Ionomer ChemFilR (p <0.05). The fluoride release occurred more significantly in the first two days, with average 33% lower compared with Vidrion R. We conclude that the resin modified nano ionomer Ketac™N100 is a material that induces an satisfactory inflammatory response in subcutaneous tissue of isogenic mice. Its polymerization shrinkage strength was lower than the resin Filtek™ Z350 and fluoride release was a third lower than the conventional glass ionomer.

Tendo em vista o importante papel desempenhado pelos selantes de fossas e fissuras na prevenção da cárie dental, o objetivo do presente estudo foi avaliar in vitro propriedades mecânicas, químicas e ntimicrobianas do selante isento de bisfenol A Embrace Wetbond™. Para os testes de resistência ao cisalhamento e microinfiltração foram selecionados 135 terceiros molares hígidos, extraídos de humanos, divididos aleatoriamente em 6 grupos: (I) selante Fluroshield® sem contaminação; (II) selante Embrace Wetbond™ sem contaminação; (III) selante Fluroshield® contaminado com saliva; (IV) selante Embrace Wetbond™ contaminado com saliva; (V) selante Fluroshield® contaminado com água; e (VI) selante Embrace Wetbond™ contaminado com água. No estudo de resistência ao cisalhamento os dentes foram seccionados no sentido vestíbulo-lingual, a porção radicular removida e as superfícies mesiais e distais foram embebidas em resina de poliéster. Após o condicionamento do esmalte, foi aplicado o selante com o auxílio de uma matriz de Teflon®. Os espécimes foram termociclados e submetidos ao teste de resistência ao cisalhamento com uma velocidade de 0,5mm/min e célula de carga de 50kgf. Os resultados foram comparados empregando a análise de variância (ANOVA) e pós-teste de Tukey. No estudo de microinfiltração, após o condicionamento do esmalte foi aplicado o selante. Os dentes foram termociclados, selados na região da câmara pulpar com resina composta, isolados, imersos em solução de rodamina B a 0,2%, incluídos em resina acrílica, seccionados, lixados, montados em lâminas, identificados e analisados em microscópio óptico para quantificação da microinfiltração. Os resultados foram comparados empregando o teste de Kruskal-Wallis e o pós-teste de Dunn. No estudo de liberação de fluoreto por meio de água aquecida e saliva artificial foram selecionados dois selantes resinosos contendo fluoreto (Embrace Wetbond™ e Fluroshield®), uma resina composta micro-híbrida (FiltekTM Z-250) e um cimento de ionômero de vidro (Vidrion R). As determinações de fluoreto foram realizadas por potenciometria direta, utilizando o eletrodo seletivo combinado de fluoreto. Para o teste de liberação de fluoreto em saliva artificial foram confeccionados 8 corpos de prova de cada material , os quais foram armazenados em tubos plásticos contendo saliva artificial, substituída diariamente. Após 15 dias, foi avaliada a quantidade de fluoreto liberado nas soluções. Os valores obtidos em mV foram convertidos em ppm (μg/ml). Os resultados foram comparados empregando a análise de variância (ANOVA) e o pós-teste de Tukey. No estudo da atividade antimicrobiana, efetuado por meio do teste de difusão em ágar pelo método do poço, foram selecionados dois selantes resinosos contendo fluoreto (Embrace Wetbond™ e Fluroshield®), um cimento de ionômero de vidro (Vidrion R), solução de digluconato de clorexidina a 1% e soro fisiológico. Foram utilizadas cepas de S. mutans (ATCC 25175 e cepa de campo), na densidade de 1-2 da escala de McFarland. Após o período de incubação, a zona de inibição do crescimento microbiano foi mensurada. Os resultados foram comparados empregando a análise de variância ANOVA e o pós-teste de Bonferroni. O nível de significância em todas as análises estatísticas foi de 5%. No estudo da dosagem de bisfenol A foram selecionados dois selantes resinosos (Embrace Wetbond™ e Fluroshield®), dispensados em recipientes contendo 3ml de metanol. Após homogeneização e filtragem, os extratos foram analisados utilizando um espectrômetro de massas por cromatografia gasosa. Foram realizados testes com as fórmulas moleculares do bisfenol A (C15H16O2) e do Bis-GMA (C29H36O8). Com base nos resultados obtidos pôde-se concluir que o selante Embrace Wetbond™ apresentou resistência ao cisalhamento próxima do mínimo aceitável e alta microinfiltração, quando utilizado de acordo com as indicações do fabricante, em condições de contaminação com umidade. Por outro lado, esse selante apresentou elevada liberação de fluoreto, tanto em água aquecida quanto em saliva artificial, apresentou elevada atividade antimicrobiana e não apresentou liberação de bisfenol A e de Bis- GMA.
Considering the important role of pit-and-fissure sealants on the prevention of dental caries, the purpose of this study was to evaluate in vitro the mechanical, chemical and antimicrobial properties of the bisphenol A-free pit-and-fissure sealant Embrace Wetbond™. For the shear bond strength and microleakage tests, 135 sound human third molars were selected and randomly assigned to 6 groups: (I) Fluroshield® sealant without contamination; (II) sealant Embrace Wetbond™ without contamination; (III) Fluroshield® sealant contaminated with saliva; (IV) Embrace Wetbond™ sealant contaminated with saliva; (V) Fluroshield® sealant contaminated with water; and (VI) Embrace Wetbond™ sealant contaminated with water. For the shear bond strength test, the teeth were sectioned in a buccolingual direction, the root portion was removed and the mesial and distal surfaces were embedded in polyester resin. The sealant was applied to the acid-etched enamel with the aid of Teflon® matrix. The specimens were thermocycled and subjected to a shearing force at a crosshead speed of 0.5mm/min with a 50kgf load cell. Data were analyzed statistically by analysis of variance (ANOVA) and Tukeys post-test. For the microleakage assay, after acid etching of enamel, the teeth were thermocycled, the pulp chamber was sealed with composite resin, and the teeth were rendered waterproof, immersed in 0.2% B rhodamine solution, embedded in acrylic resin, sectioned, ground, mounted on glass slides, identified and analyzed with an optical microscope for quantification of microleakage. The results were compared by the Kruskal-Wallis and Dunns post-test. Two fluoride-containing resin sealants (Embrace Wetbond™ and Fluroshield®), a microhybrid composite resin (FiltekTM Z-250) and a glass ionomer cement (Vidrion R) were selected for the fluoride release test in heated water and artificial saliva. Fluoride measurements were performed with a direct potentiometry using a fluoride ion selective electrode. For the test in saliva artificial, 8 specimens of each material were fabricated and stored in plastic tubes containing artificial saliva, which as daily renewed. The amount of fluoride released in the solutions after 15 days was analyzed, and the the values obtained in mV were converted into PPM (μg/mL). The results were compared by ANOVA and Tukeys post-test. Two fluoride-containing resin sealants (Embrace Wetbond™ and Fluroshield®), a glass ionomer cement (Vidrion R), 1% chlorhexidine digluconate solution and saline were selected for the analysis of the antimicrobial activity using the agar-well diffusion assay. Suspensions of S. mutans strains (ATCC 25175 and field strain) with density equivalent to the 1-2 McFarland scale were used. After incubation, the zones of microbial growth inhibition were measured. The results were compared by ANOVA and Bonferroni post-test. A significance level of 5% was set for all statistical analyses. For the analysis of bisphenol A dosage, two resin sealants (Embrace Wetbond™ and Fluroshield®) were delivered in receptacles containing 3ml of methanol. After homogenization and filtering, the extracts were analyzed under gas chromatography-mass spectroscopy and tests were performed with the molecular formulas of bisphenol A (C15H16O2) and Bis-GMA (C29H36O8). Based on the obtained results, it may be concluded that the sealant Embrace Wetbond™ presented shear bond strength near of the minimum acceptable and great microleakage when used according to the manufacturers instructions under moisture contamination conditions. On the other hand, this sealant presented high fluoride release in both heated water and artificial saliva, showed high activity antimicrobial and did not present release of bisphenol A or Bis-GMA.

碩士
國立臺灣大學
臨床牙醫學研究所
88
With a preventive approach to the control of dental caries comes a need to develop and assess dental materials that can be used not only to restore teeth but also to assist in preventing further damage. Fluoride (F)- releasing restorative materials can inhibit demineralization and promote remineralization because of their F release ability. The purpose of this study was to evaluate four F-containing restorative materials on their F releasing ability before and after F treatment in running de-ionized water within an artificial mouth system. Four F-containing restorative materials (glass-ionomer cement / Fuji IX GP, resin-modified glass-ionomer / Vitremer, polyacid-modified composite resins / Compoglass F, F-containing composite resins / Ariston pHc) were tested and the composite resin (Z100) served as control. After assembling the infusion pump and the solution administration set into an artificial mouth system, one freshly prepared specimen was put into the drip chamber of the solution administration set. The drip chamber containing 2 ml of de-ionized water served as artificial mouth. The infusion pump controlled the flow rates of 20 ml/hour. Samples (40μl) were collected from the drip chamber at 1, 10, 20,30 ,40 ,50 ,60 ,75 ,90, 105 min, 3, 3.5, 4, 4.5, 5, 6, 8, 10, 12 hours, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, and 6 days respectively and fluoride content was analyzed. In addition, sample (40μl) were collected from the tail end of the artificial mouth system at 1, 2, 3, 4,.5, 6, 8, 10, 12 hours, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, and 6 days respectively and fluoride concentration was also analyzed.. At the end of 6th day, the specimen was treated with 10 ml of 0.2﹪sodium fluoride for one min. As above, fluoride analysis from the drip chamber (1, 10, 20, 30, 45 min, 1, 1.5, 2, 3, 4, 6, 9, and 12 hours) and the tail end of the artificial mouth system (1, 2, 3, 4, 6, 9, and 12 hours) were performed. Fluoride concentrations of the collected solution were measured by F electrode. The results revealed that all materials with the exception of Z100 showed the highest F concentrations during the first hour and first 10 min in particular followed by continuously declining. F released from materials of experimental groups lasted to the end of the experiment. During the first 3 hours, the differences of F concentrations within 4 experiment groups were significant. Then all materials of experiment groups, with the exception of Ariston pHc, showed non-significant within group. Ranking of materials of total F released over 6 days from the greatest to the least was as follows: Ariston pHc (312.2± 22.8μg/㎝2 )＞Vitremer (225.3 ± 4.6μg/㎝2 )＞Fuji IX GP (195.8 ± 10.1μg/㎝2 )、Compoglass F (180.4 ± 4.4μg/㎝2). The cumulative F release curve of Ariston pHc tended to increase with time, instead of tending to constant values (Vitremer, Fuji IX GP, Compoglass F). After F treatment, the F concentrations in the artificial mouth dropped to the level of pre-treatment within 2-4 hours. The amount of difference of cumulative F released per hour between before and after F treated follows a trend of Vitremer＞Ariston pHc＞Fuji IX GP and Compoglass F. When selecting material for clinical use, the level of F releasing should not be considered as only criteria. Its clinical needs, biocompatibility, solubility, and other physical properties should be concerned. As to the anti-caries ability of fluoride-containing dental restorative materials, this study provides a basis for further study.

碩士
國立臺灣大學
口腔生物科學研究所
92
The major cariostatic mechanism of fluoride （F） is believed to be that it reduces dental caries through promoting re-mineralization and influencing the morphology of teeth by reducing the solubility of enamel. As a result, fluoride can be used to prevent re-caries. The aim of this study was to evaluate Polymer-Smectic Clay Nano- composite and other F-containing restorative material on their F releasing ability before and after F treatment in de-ionized water system. Five F-containing restorative materials including four polymer- smectic clay nanocomposite（1. Ｋaolinite　2. Ｋ-diamine　3. Ｋ- acetate　4.Ｋ-acrylamide）, and GC Fuji IX（ GC Int. Corp, Tokyo , Japan ）were tested and the composite resin (Z100) was served as control. After curing, the amounts and the profiles of fluoride release from these materials placed in a fresh polypropylene vial with 3 ml of de-ionized water and stored at 37℃ were evaluated in this study. They were taken over a period of 8 weeks at the intervals of 4, 8, and 24, hours, as well as 2, 3, 7, 14, 28, and 56 days. The pattern of fluoride release was similar for all of the examined materials. At the end of 56th day, some specimens were treated with 5 ml of 0.2﹪sodium fluoride stirring for one minute and others specimens were treated with 5 ml of 0.2﹪sodium fluoride stirring for one minute. Any surface damage should be avoided, before being rinsed and sprayed gently. Again, the specimens were treated as above. The solutions were replaced using the same time schedule as before, and the recharged specimens were also assessed at the same time for the amounts of fluoride ions released over another 56 days. The results revealed that ranking of materials of total F released over 56 days from the greatest to the least was as follow: K-acetate> K-diamine＞K-acrylamide＞Kaolinite＞Fuji IX and Z100 did not release fluoride. After fluoride treatment, it was demonstrated that only Kaolinite and Fuji IX could recharge fluoride, and others were not significant within group. Considering the amounts of fluoride release, these four polymer-smectic clay nanocomposites were better than Fuji IX and Z100. As to the anti-caries ability of fluoride-containing dental restorative materials, this study provides a basis for further study.

碩士
國立臺灣大學
臨床牙醫學研究所
99
Objectives The newly-developed pit and fissure sealant, fluoride-containing kaolinite-acrylamide composite resin, has the better fracture toughness, hardness and the less viscosity when compared with ClinproTM. It is also proved that the new material has no biological toxicity. The purpose of the study is to further understand the processes of fluoride release and recharge of the new material and other two pit and fissure sealants (ClinproTM and ClinproTM XT), and make the advanced comparison. Materials and methods Three materials were used in the study— fluoride-containing Kaolinite-acrylamide composite resin, ClinproTM and ClinproTM XT. The last two materials were the control groups. Fluoride was released from the materials into the deionized water, and fluoride in the water was analyzed by the ion chromatography for different purposes. The present study included three parts. Part I was “56 days fluoride elution experiment” and to figure out the equations which were the most representative for the plots of the fluoride cumulative release of the three materials. Part II was ”maturation experiment”. Part III was “different time points for NaF recharge” Results At the Part I, the most representative equation for the plot of the fluoride cumulative release of ClinproTM was [F]c = a*t/(b+t)+c*t/(d+t)+e*t；the equation for K-acrylamide CR was [F]c=([F]I*t/(t1/2+t)) + ([F]I’*t/(t1/2’+t)) + Ns*t; the equation for ClinproTM XT was [F]c=([F]I*t/(t1/2+t)) + ([F]I’*t/(t1/2’+t)). At the Part II, the different maturation time had more effect on the fluoride release amount of ClinproTM XT than on ClinproTM and K-acrylamdie CR. At the Part III, the three materials all had the ability of fluoride recharge and re-release. No matter what time point of the fluoride recharge was, there was no significant change in the fluoride re-release amount of the three materials. The ability of fluoride recharge: ClinproTM XT＞K-acrylamide CR＞ClinproTM。 Conclusion Fluoride-containing kaolinite-acrylamide composite resin as a pit and fissure sealant has better results of fluoride release and recharge than ClinproTM though worse results than ClinproTM XT. However, the new material, resin-based, was more resistant to wear and chemical irritants than ClinproTM XT. When applying to pits and fissures, it was also more convenient to use the new material because of the less viscosity. According to the equations acquired, we could get the advanced information of fluoride release process.

碩士
國立臺北科技大學
材料及資源工程系研究所
100
The use of composite resin material for posterior tooth restorations is increasing. This increase is attributed primarily to demand for improved esthetics. However, poor material properties limited the success of composite restoration in posterior teeth. Microleakage, fractures within the body of the restorations, marginal ditching, protruding, and imperfect wear resistance are reported as being the most common causes of failure in posterior composites. Fluoride release from restorative materials may prevent development of secondary carious lesions at the restoration tooth inter face and can develop remineralization of enamel or decalcified dentin, so long as physical and mechanical properties are not adversely affected. The objuct of this study want to investigate a new composite resin with good mechanical properties and expect could provided fluoride release and recharge property.

OBJECTIVE: To assess the fluoride release and mechanical properties of four restorative glass ionomer cements (GIC) and to determine the correlation between the mechanical properties and fluoride release. MATERIALS AND METHODS: Four restorative glass ionomers were studied: ChemFil ROCK (DENSPLY), Fuji IX (GC), Riva self cure (SDI), and Ketac Nano (3M ESPE). Fluoride release in deionized water from the tested specimens was measured using a fluoride-selective ion electrode for 9 days. The compressive strengths and diametral tensile strengths after storing in distilled water (room temperature, 24) were tested. Glass ionomer surface wear by dental ceramic (Vita Mark II cylinders) was evaluated by a depth micro analyzer. Data were analyzed using ANOVA followed by Tukey’s test or Bonferroni method (p= 0.05). RESULTS: The fluoride release exhibited high concentration, following by a significant drop on the second day. Fuji IX had the highest fluoride release followed by “Ketac”,” Riva”, and “ChemFil”. Compressive strength results ranked that ChemFil as the highest value, followed by Fuji IX, Ketac, and Riva. The diametral tensile strength test ranked ChemFil and Ketac as the highest values. Surface ear against dental ceramic (Vita Mark II cylinders) revealed that Fuji IX had the lowest material loss, followed by Ketac, ChemFil, and Riva. Data showed significant differences between all of them. After coating the glass ionomer, the surface wear loss was reduced significantly in Riva and ChemFil. CONCLUSIONS: The tested restorative glass ionomers showed differences in fluoride release and the differences decreased over time, with Fuji IX releasing the highest amount of fluoride ion. ChemFil Rock showed the highest mechanical properties but the lowest fluoride release. Riva self cure had the highest material loss value in wear test. There was a weak inverse correlation between fluoride release and compressive strength (r = - 0.32); fluoride release and diametral tensile strength (r = - 0.60), and fluoride release and surface wear against dental ceramic (Vita Mark II cylinders) (r = - 0.55).

Indiana University-Purdue University Indianapolis (IUPUI)
The majority of currently marketed fluoride varnishes (FV) have not been evaluated for their effectiveness in preventing dental caries. Fundamental research on FVs and how different formulations affect adherence to teeth, fluoride release into saliva and uptake by teeth is virtually non-existent. The objective of this work was to investigate the anti-caries potential, measured as fluoride release into saliva, change in surface microhardness of early enamel caries lesions, and enamel fluoride uptake, of multiple commercially available FVs. We have found that FVs differed in their release characteristics, rehardening capability, and ability to deliver fluoride to demineralized lesions. In addition to our in vitro work, we have conducted a clinical study that aimed to compare saliva and plaque fluid fluoride concentrations following the application of three commercially available FV treatments at predetermined post application time points. We also investigated the change in fluoride concentration in saliva and plaque fluid fluoride from baseline to each post application predetermined time point. We found that FVs varied in their release of fluoride into saliva and plaque fluid but shared common trends in release characteristics. The outcomes of our in vitro and in vivo investigations demonstrate a great variation in anti-caries potential of FVs. This may be attributed to different compositions and physical properties of the tested FVs.

Cycling of the relative humidity (RH) levels in the reactant streams of polymer electrolyte membrane (PEM) fuel cells has been reported to decay fuel cell performance. This study focuses on the accelerated durability testing to examine different modes of membrane failure via RH cycling. A single PEM fuel cell with an active area of 42.25 cm2 was tested. A Greenlight G50 test station was used to establish baseline cell (Run 1) performance with 840 hours of degradation under high-humidity idle conditions at a constant current density of 10 mA cm-2. Under the same conditions, two other experiments were conducted by varying the RH. For the H2-air RH cycling test (Run 2), anode and cathode inlet gases were provided as dry and humidified gases. Another RH cycling experiment was the H2 RH cycling test (Run 3): the anode inlet gas was cycled whereas keeping the other side constantly at full humidification. These two RH cycling experiments were alternated in dry and 100% humidified conditions every 10 and 40 minutes, respectively. In the experiments, the fuel cells contained a GoreTM 57 catalyst coated membrane (CCM) and 35 BC SGL gas diffusion layers (GDLs). The fuel cell test station had been performed under idle conditions at a constant current density of 10 mA cm-2. Under the idle conditions, operating at very low current density, a low chemical degradation rate and minimal electrical load stress were anticipated. However, the membrane was expected to degrade due to additional stress from the membrane swelling/contraction cycle controlled by the RH. In this work the performance of the 100% RH humidified cell (Run 1) was compared with that of RH cycling cells (Run 2 and Run 3). Chemical and mechanical degradation of the membrane were investigated using in-situ and ex-situ diagnostic methods. The results of each measurement during and after fuel cell operation are consistent. They clearly show that changing in RH lead to an overall PEM fuel cell degradation due to the increase in membrane degradation rate from membrane resistance, fluoride ion release concentration, hydrogen crossover current, membrane thinning, and hot-spot/pin-hole formation.

碩士
淡江大學
化學工程學系
85
Safety has become one of the major concerns in the chemical process industry today. How the chemical company manages safety within the plant directly affects the well-being of the entire community. To help ensure safe plant operations, we must understand and manage the hazards associated with toxic and flammable chemicals. For the protection of plant personnel and the surrounding community, emergency preparedness and response procedures systems are essential. To help analyze the potential effects of accidental release of toxic and flammable chemicals into the atmosphere, we should understand the mathematical models that describe source/evaporation, dispersion, and vapor cloud explosion. The models are complicated but provide a useful means in performing the job. The objective of this study is to illustrate the use of computer to modelchemical hazard scenarios occurred in the plants and the neighboring community. Cyclohexane and hydrogen fluoride are chosen because they are being used in large quantity. Cyclohexane is a flammable chemical while hydrogen fluoride is very toxic. In the study, we will first identify appropriate models to be used in the accident scenarios; then we will observe the physical effects; and finally, we assess the consequences as a result of the accidental release.