Rozprawy doktorskie na temat „Solubility”
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Whiting, Gary Stephen. "Studies on solubility and solubility-related processes". Thesis, University College London (University of London), 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360561.
Pełny tekst źródłaBouillot, Baptiste. "Approches thermodynamiques pour la prédiction de la solubilité de molécules d'intérêt pharmaceutique". Phd thesis, Toulouse, INPT, 2011. http://oatao.univ-toulouse.fr/6993/1/bouillot.pdf.
Pełny tekst źródłaEvans, Lan Tuyet. "A simple solubility theory combining solubility parameter and Lewis acid-base concepts /". Online version of thesis, 1988. http://hdl.handle.net/1850/10940.
Pełny tekst źródłaCampanell, Frank Christopher. "The Modeling of Solubility". Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1169068854.
Pełny tekst źródłaMorris, Kenneth Robert. "Solubility of aromatic compounds in mixed solvents". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184324.
Pełny tekst źródłaAsatani, Haruki. "Solubility of gases in liquids". Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4643.
Pełny tekst źródłaMontaseri, Hashem. "Taxol, solubility, stability, and bioavailability". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq21604.pdf.
Pełny tekst źródłaBondesson, Laban. "Microscopic Interpretations of Drug Solubility". Doctoral thesis, Stockholm : Skolan för Bioteknologi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4388.
Pełny tekst źródłaBondesson, Laban. "Microscopic views of drug solubility". Licentiate thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3940.
Pełny tekst źródłaPitani, Lavanya. "SOLUBILITY ENHANCEMENT OF MODEL COMPOUNDS". Scholarly Commons, 2017. https://scholarlycommons.pacific.edu/uop_etds/2985.
Pełny tekst źródłaPatel, Suresh Dahyabhai. "Freeze-drying and solubility studies". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184399.
Pełny tekst źródłaKim, In-Young. "Aqueous Solubilities and Water Induced Transformations of Halogenated Benzenes". Thesis, University of North Texas, 1989. https://digital.library.unt.edu/ark:/67531/metadc332705/.
Pełny tekst źródłaAlbahrani, Abdullah Abdulmohsen A. "Modeling gas solubility in glassy polymers". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Znajdź pełny tekst źródłaMoore, Steven Jeremy. "Solubility of Ã-olefins in polyethylenes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0001/MQ59852.pdf.
Pełny tekst źródłaMachatha, Stephen Gitu. "Estimation of Ethanol/Water Solubility Profiles". Diss., Tucson, Arizona : University of Arizona, 2006. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1659%5F1%5Fm.pdf&type=application/pdf.
Pełny tekst źródłaGracin, Sandra. "Solubility and polymorphism of molecular compounds /". Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-267.
Pełny tekst źródłaDu-Cuny, Lei. "Aqueous solubility of drug-like compounds". [S.l.] : [s.n.], 2006. http://www.gbv.de/dms/bs/toc/515726915.pdf.
Pełny tekst źródłaGorshkova, M. Yr, I. V. Volkova, E. S. Grigorian i V. A. Izumrudov. "Polyelectrolyte Nanocomplexes with pH-controlled Solubility". Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35468.
Pełny tekst źródłaOchsner, Allison Becker. "Solubility prediction in nonideal liquid mixtures /". The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487260859494571.
Pełny tekst źródłaYang, Gang. "Aqueous solubility prediction of organic compounds". Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/298795.
Pełny tekst źródłaJain, Parijat. "Prediction of aqueous solubility from SCRATCH". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/193517.
Pełny tekst źródłaHecq, Jérôme. "Development, characterization and evaluation of crystalline nanoparticles for enhancing the solubility, the dissolution rate and the oral bioavailability of poorly water-soluble drugs". Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210816.
Pełny tekst źródłaOut of the many ways to increase a product’s solubility/dissolution rate characteristics with the aim of enhancing its oral bioavailability, drug formulation as nanoparticles has received much-increased interest over the last decade. The hypothesis behind dissolution rate enhancement, considering drug particle size reduction to nanometer range, lies primarily in a much-increased effective surface area (Noyes-Whitney) presented by the resulting drug nanoparticles. Out of the various technologies available for drug particle size reduction to nanometer range, milling using high pressure homogenization is regarded as one of the simplest and most effective techniques. High pressure homogenization is a solvent-free process and is relatively rapid (time-saving). Furthermore, and most importantly, the scaling up of this technique is already established; processing capacities ranging from 3 l/h (e.g. EmulsiFlex C3®: minimum sample volume - 10 ml) to 1000 l/h (e.g. EmulsiFlex C1000®: minimum sample volume - 2 l).
Four model drugs were studied in this work. Nifedipine (NIF), an extensively studied poorly water-soluble drug in the literature, was used as the main model on which most of the development was done. In parallel to the work carried out on NIF, three UCB S.A. molecules currently under development were also studied as poorly water-soluble drugs: these being ucb-35440-3, UCB-A and UCB-B (salt of UCB-A). These three UCB S.A. model drugs are, contrarily to NIF, predicted highly dosed drugs and are weak bases, and thus present pH-dependent solubility profiles, which allowed us to investigate model drugs with different profiles.
Firstly, investigations regarding appropriate formulation development (stabilizer (surfactant) selection) and appropriate high pressure homogenization operating conditions (pre-milling cycles, influence of the number of high pressure homogenizing cycles, influence of homogenizing pressure, influence of sample temperature) were made. It has been shown, through this development, for the four studied model drugs, that high pressure homogenization is an appropriate technique for reducing drug particle size to nanometer range (NIF &61566; 290 nm, ucb-35440-3 &61566; 180 nm, UCB-A &61566; 350 nm and UCB-B &61566; 250 nm). Investigations regarding water-removal from the nanosuspensions obtained and most importantly regarding the redispersion characteristics of the retrieved powders (i.e. nanoparticles) were then carried out. In that regard, it has been shown that the presence of carriers in the formulation is essential for limiting nanoparticles agglomeration during the water-removal operation.
Drug crystalline state characterizations before and following particle size reduction were then carried out on the three studied model drugs, mainly through DSC and PXRD studies. In fact, one of the advantages of this particle size reduction approach (using high pressure homogenization), versus other frequently studied solubility/dissolution rate enhancement technologies (e.g. such as solid dispersions), is that original crystalline state shall not be altered in such a way that the achieved increased solubility and dissolution rate characteristics do not rely on the presence of the amorphous form of the drug; this furthermore implying a greater time-stability of the developed formulations. Through the data obtained, it has been shown that original drug crystalline state seems to be unaltered following particle size reduction.
In vitro solubility and dissolution characteristics were then evaluated on the formulations developed in order to verify the posed hypothesis regarding effective surface area increase. It has been shown through these studies that drug solubility and most importantly drug dissolution rate can be significantly enhanced for nanoparticulate systems (verified for NIF, ucb-35440-3, UCB-A and UCB-B). For example, solubility was enhanced from 26 µg/ml vs. 19.5 µg/ml for NIF nanoparticles and the dissolution characteristics showed that 100% of the tested dose (equivalent to 10 mg NIF) was already dissolved following 10 min vs. less than 5% for un-milled NIF. Following these very interesting and promising results, and preliminary to the in vivo pharmacokinetic studies carried out, in vitro permeation studies (apical to basolateral transfer studies) across intestinal cell models (Caco-2 and HT29-5M21 cultures and co-cultures) were carried out. This evaluation was only carried out using NIF as a model drug and showed a 6-fold increase in the permeation rate for NIF nanoparticles. The influence of chitosan (permeability enhancer/bioadhesive polymer) in the NIF nanoparticle formulation with regard to in vitro NIF permeation rate was also evaluated.
In vivo pharmacokinetic studies in rats were conducted using NIF and ucb-35440-3 as model drugs. The very different profiles of these two model drugs allowed us to retrieve interesting information regarding the in vivo behaviour of the developed formulations. As expected from the in vitro (i.e. solubility/dissolution/permeation) studies and results obtained for NIF, an increased extent of exposure could be observed for NIF nanoparticles versus un-milled NIF; the difference being more pronounced when the formulations were orally administered into capsules (2.5-fold increase in extent of exposure and 6-fold increase in Cmax). For ucb-35440-3, a poorly water-soluble weak base with a reported significant food effect considering oral bioavailability, an increased extent of exposure for nanoparticles, versus the un-milled drug, could only be observed in fasted state (4-fold increase in extent of exposure and 2.7-fold increase in Cmax). These different, diet-relative observations allowed us to put forward some limitations and precautions (considering poorly water-soluble weak bases) relative to the possibility of drug reprecipitation following stomach’s exiting, particularly if dissolution in the stomach is quite fast (e.g. nanoparticulate systems).
In parallel to the in vivo pharmacokinetic evaluation of NIF nanoparticles, evaluation of the antihypertensive effect of the systems developed following oral administration, using spontaneously hypertensive rats, was also carried out and compared to un-millled NIF. The results obtained showed a significant drop in systolic blood pressure for NIF nanoparticles (32% reduction of initial SBP following 30 min vs. 1% for un-milled NIF) and nicely complemented the in vitro and in vivo results obtained for NIF nanoparticles.
Finally, a stability study of the optimized NIF nanoparticle formulation was carried out with respect to reported ICH conditions (25°C/60% RH; 30°C/65% RH; 40°C/75% RH). The results showed that the studied NIF nanoparticle formulation retains all its original characteristics (dissolution, crystalline state, redispersion characteristics); this being verified over time (12 months) and for each of the three storage conditions studied.
Doctorat en sciences pharmaceutiques
info:eu-repo/semantics/nonPublished
Pinal-Calvillo, Rodolfo. "Estimation of aqueous solubility of organic compounds". Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184463.
Pełny tekst źródłaBengtsson, Åsa. "Solubility and Surface Complexation Studies of Apatites". Doctoral thesis, Umeå universitet, Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1408.
Pełny tekst źródłaMargerum, Michael Robert. "Solubility measurement in supercritical fluids by chromatography". Thesis, University of Ottawa (Canada), 1985. http://hdl.handle.net/10393/4561.
Pełny tekst źródłaBengtsson, Åsa. "Solubility and surface complexation studies of apatites /". Umeå : Department of Chemistry, Umeå University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1408.
Pełny tekst źródłaBernardo, Carlos Gabriel Pires Morgado. "Solubility of organic liquids in polystyrene matrices". Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419261.
Pełny tekst źródłaPearce, David L. "Solubility of Triglycerides in Supercritical Carbon Dioxide". Thesis, University of Canterbury. Chemical and Process Engineering, 1990. http://hdl.handle.net/10092/5786.
Pełny tekst źródłaPaus, Raphael [Verfasser]. "Solubility and Dissolution of Pharmaceuticals / Raphael Paus". München : Verlag Dr. Hut, 2016. http://d-nb.info/1097817733/34.
Pełny tekst źródłaPytka, Mario Antonio. "Testing nonlinear evolution equations for exact solubility". Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236765.
Pełny tekst źródłaHowson, M. R. "Solubility and crystallization of low Mg-calcites". Thesis, University of Reading, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373757.
Pełny tekst źródłaWu, M. F. "The solubility of solutes in cryogenic liquids". Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373935.
Pełny tekst źródłaCheng, Chin-Hwa 1957. "Solubility of diuron in complex solvent systems". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277194.
Pełny tekst źródłaMishra, Dinesh Shyamdeo. "Solubility of organic compounds in nonaqueous systems". Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184667.
Pełny tekst źródłaHoye, William L. "Thermodynamics and Solubility Modeling in Hydrofluoroalkane Systems". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/196099.
Pełny tekst źródłaGupta, Bindu 1963. "Solubility of anthracene in complex solvent system". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276989.
Pełny tekst źródłaMiller, Allan Harvey 1968. "Predicting the solubility of hydrogen bonding aromatics". Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/291667.
Pełny tekst źródłaSidigu, Sule. "Simple Descriptors for Modeling the Solubility of Gases, Alcohols, and Halogenated Hydrocarbons in Water". Wright State University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=wright1195010941.
Pełny tekst źródłaRiley, Christine Marie 1964. "The effect of triacetin on solubility of diazepam and phenytoin". Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/277304.
Pełny tekst źródłaMorris, Kenneth Robert 1951. "THE SOLUBILITY OF HYDROPHOBIC POLLUTANTS IN WATER-COSOLVENT MIXTURES". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276659.
Pełny tekst źródłaShoghi, Kalkhoran Elham. "Physico-Chemical Characterization of Drugs: Acidity and Solubility". Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/98463.
Pełny tekst źródłaEl objetivo del presente trabajo ha sido contribuir a establecer metodología robusta y de high throughput de interés en la etapa conocida como "Drug Discovery" que tiene lugar en los laboratorios farmacéuticos al inicio del proceso de desarrollo de nuevos fármacos. Este objetivo ha implicado la exploración de las posibilidades de la metodología potenciométrica establecida y comercializada por Sirius Analytical Ltd. para la determinación de las constantes de acidez y de la solubilidad de compuestos bioactivos y también un estudio sobre la mejora de la biodisponibilidad de un fármaco muy insoluble tomado como modelo mediante el aumento de su velocidad de disolución. En la primera parte de esta Tesis se han determinado potenciométricamente las constantes de disociación ácida y la variación de entalpía asociada de dos bases y dos ácidos tomados como modelo en agua pura y en mezclas de metanol/agua (0-60% w/w) a varias temperaturas (25-55°C). Esto ha implicado la puesta a punto de la estandarización del sistema potenciométrico en las condiciones de trabajo. Los valores de pK(a) determinados son concordantes con los que ofrece la literatura. Se han calculado también las entalpias de disociación en los distintos solventes binarios estudiados mediante la ecuación de Van't Hoff a partir de los valores experimentales de pK(a). La consistencia de los resultados obtenidos con los de la literatura, obtenidos directamente por calorimetría, confirma la robustez de la metodología. En la segunda parte de este trabajo, el estudio se centró sobre la determinación potenciométrica de la solubilidad de ácidos y bases mediante el método conocido como Chasing Equilibrium, como alternativa a los procedimientos clásicos de equilibración. El método es rápido y produce resultados precisos. Se ha realizado un estudio sobre las condiciones experimentales óptimas en términos de peso de la muestra para medir eficazmente la solubilidad. El estudio muestra que, en función de la naturaleza y solubilidad de los compuestos, existe un intervalo limitado de peso de muestra adecuado para obtener resultados fiables. En la tercera parte de la presente memoria, se estudian los perfiles de solubilidad en función del pH de cinco fármacos ionizables de naturaleza diferente, un ácido y una base monopróticos, una base diprótica y dos compuestos anfóteros que muestran una especie zwitteriónica cada uno. Se han determinado los perfiles de solubilidad mediante el método clásico de equilibración (Shake-Flak, S-F) y el potenciómétrico y, en ambos casos, se han utilizado las relaciones apropiadas de Henderson-Hasselbalch (H-H) o derivadas. Los resultados obtenidos de forma independiente por ambos métodos son consistentes. Se ha hecho un estudio crítico acerca de la influencia del electrolito utilizado como agente tampón en el método S-F en los valores de solubilidad obtenidos y se han observado algunas desviaciones de los puntos experimentales con respecto a los perfiles esperados que pueden ser debidas a interacciones específicas entre el electrolito tampón y el fármaco. En otros casos, las desviaciones observadas son independientes de los tampones utilizados y se pueden atribuir a la formación de nuevas especies tales como agregados iónicos del fármaco en estudio o la precipitación de una sal a partir de una especie catiónica del compuesto analizado. En la cuarta parte de esta memoria el objetivo ha sido estudiar la velocidad de disolución de comprimidos preparados a partir de dispersiones sólidas de un fármaco modelo con y sin portador del fármaco y también en presencia y en ausencia de tensioactivo en soluciones acuosas neutras y ácidas. Como fármaco modelo se estudió la Anfotericina B y se utilizaron como portadores manitol e inulina y como tensioactivos se ensayaron el deoxicolato de sodio (SDC) y el laurilsulfato de sodio (SLS). La difracción de rayos X reveló que el fármaco en estudio se hallaba en estado amorfo en todas las dispersiones sólidas estudiadas. Se puede concluir que la velocidad de disolución del fármaco se incrementa significativamente en presencia de portador y tensioactivo.
Hagelberg, Erik. "The matrix dependent solubility and speciation of mercury". Thesis, Örebro University, Institutionen för naturvetenskap Department of Natural Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-636.
Pełny tekst źródłaThe Swedish government has decided that waste containing more than 0.1% mercury is to
be placed in a permanent repository in the bedrock1,10. To minimize the risk of spreading
mercury, elemental mercury must first be converted into a practically insoluble
compound. In a PhD investigation of stabilization attempts at SAKAB AB in Kumla
favorable conditions for conversion of mercury to cinnabar (the sparingly soluble sulphide
form of mercury and the naturally occurring mineral) was found. In a long-term study of
diffusion of mercury it was found that water solubility of mercury varied much, from 0.05
to 5 μmolL-1.
To be able to study the water solubility of mercury as detailed as possible a speciation
method was developed and verified. This investigation includes how different parameters,
like matrix properties and Hg0/solution ratios effects the solubility of mercury and how the
different species are distributed in the water phase. The total solubility of mercury is very
dependent of both the matrix properties and the Hg0/solution ratio.
Aqueous elemental mercury (Hg0
aq) is not as matrix dependent as the oxidized species.
However, trends show that a higher Hg0/solution ratio contributes to a higher solubility of
Hg0
aq. Factors like time, pH, ionic strength and degree of stirring, greatly effects the total
solubility of mercury. The concentration of the oxidized mercury species generated from
elemental mercury increases over time and is very dependent on the properties of the
matrix. After 18 hours the solubility of Hg0
aq ranges from 0.2 to 0.7 μmolL-1, depending
on Hg0/solution ratio. The solubility for the oxidized species has a much larger variation,
ranging from 0.1 to 28.6 μmolL-1. Among other things, because the composition and
redox potential of the matrix plays an important role in what mercuric complexes can be
expected to form, and contribute to the solubility.
Det har beslutats av regeringen att senast år 2010 skall kvicksilverhaltigt avfall med en
kvicksilverhalt på mer än 0.1% slutförvaras i en stabiliserad from djupt ner i berggrunden.
I en doktorsavhandling som genomförts på SAKAB AB i Kumla har det konstaterats att
det är möjligt att överföra elementärt kvicksilver till cinnober, den stabila sulfidformen av
kvicksilver som för övrigt är ett naturligt förekommande mineral. Experiment som pågått
under lång tid för att studera det elementära kvicksilvrets diffusion under olika
omständigheter har också utförts. De uppmätta halterna i vattenfasen har varierat mycket,
från 0.05 till 5 μmolL-1. Det är vad som ligger till grund för det här arbetet.
För att kvicksilvers löslighet skall kunna studeras fullt ut har en specierings metod
vidareutvecklats och verifierats att den fungerar. Studien innefattar hur lösligheten av
kvicksilver påverkas av olika parametrar, som till exempel; matriser med olika egenskaper
och olika kvicksilver/vatten kvoter, samt hur fördelningen mellan oxiderade species och
det elementära kvicksilvret är i vattenfasen (Hg0
aq). Den totala lösligheten av kvicksilver
beror dels av matrisens egenskaper och mängden kvicksilver i förhållande till mängden
vätska. Lösligheten av Hg0
aq är inte lika beroende av matrisen som de oxiderade species.
Däremot finns trender som visar att högre Hg0/lösning kvot bidrar till en aningen högre
löslighet av Hg0
aq. Tid, konduktivitet, pH och omrörning spelar stor roll för vilken
totalhalt och hur stor andel oxiderade species man får i vattenfasen. Lösligheten av Hg0
aq,
efter 18 timmar, varierar mellan 0.2 till 0.7 μmolL-1, beroende på Hg0/lösning kvoten.
Efter 18 timmar är lösligheten för de oxiderade species mycket mer varierande, från 0.1
till 28.6 μmolL-1. Detta beror bland annat på att matrisens sammansättning och redoxpotential
spelar en viktig roll för vilka komplex som kan bildas med kvicksilverjonerna
och på så sätt bidra till en ökad löslighet.
Jung, Mi-Hee. "Solubility Studies on the NaAlO2-NaNO3-H2O System". MSSTATE, 2005. http://sun.library.msstate.edu/ETD-db/theses/available/etd-08032005-140710/.
Pełny tekst źródłaFahmy, Sherif Medhat. "Solubility of fluorinated polymers in supercritical carbon dioxide". [S.l.] : [s.n.], 2005. http://nbn-resolving.de/urn:nbn:de:hbz:82-opus-13540.
Pełny tekst źródłaGivand, Jeffrey. "The effect of relative solubility on crystal purity". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/10909.
Pełny tekst źródłaVandervorst, Philippe. "Diffusion and Solubility of Additive Mixtures in Polyolefins". Thesis, University of Sussex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506964.
Pełny tekst źródłaOkopi, I. A. "Solubility and migration of stabilizing additives in polyolefins". Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382571.
Pełny tekst źródłaMao, Lingchen. "Lability and solubility of trace metals in soils". Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14058/.
Pełny tekst źródłaMichael, Michael. "Solubility studies on poly(ethylene oxide) and cellulose". Thesis, University of Warwick, 1997. http://wrap.warwick.ac.uk/81925/.
Pełny tekst źródłaLatief, Abduraghman. "Sorption and solubility of a denture base acrylic". Thesis, Cape Peninsula University of Technology, 2012. http://hdl.handle.net/20.500.11838/1533.
Pełny tekst źródłaStatement of problem It is well documented that water sorption and water solubility by auto-polymerizing resins have a negative impact on their physical properties and may lead to harmful tissue reactions. The presence of residual monomer is often identified as the main cause for adverse tissue reactions. To optimize the polymerization reaction, the use of the proper powder/liquid ratio is recommended in the fabrication of a dental appliance. It is also recommended that a dental appliance should be soaked in water for at least 24 hours before delivery to a patient, in order to reduce the possible adverse effect. For auto-polymerizing resins, associated with higher residual monomer levels than heat-cured resins, soaking the appliance at elevated temperatures (65ºC for 60 minutes), would reduce the residual monomer content more efficiently than at room temperature. This requires additional processing conditions from the technician or dentist. Changing the powder/liquid ratios, deliberately or not, may modify the residual monomer content of the final product. A relationship exists between the levels of residual monomer and water sorption. Also, residual monomer leaching into the oral fluids may lead to adverse effects such as, oral tissue irritation or a delayed hypersensitivity reaction. Aim of the study The aim of this study was to evaluate the effect of different powder/liquid ratios and different water temperatures on the levels of sorption and solubility of an auto-polymerizing resin material used for denture bases. The null-hypothesis tested was that there is no difference in sorption and solubility among groups of specimens made from an auto-polymerizing resin material soaked in water at different temperatures and/or fabricated with different powder/liquid ratios. Material and methods Specimens were made from cold-cure pour-type denture base resin (Type 2, Class 2) using different powder/liquid ratios and soaked at different soaking temperatures. One group of specimens fabricated with the manufacturer’s recommended powder/liquid ratio and soaked in water at 37ºC, served as the control group for both experiments. Custom-made stainless steel moulds were used to fabricate resin disks, with a diameter of 50mm and a thickness of 0.5mm. For the temperature-controlled experiment, identical specimens were prepared and stored in distilled water at 37ºC; 45ºC; 55ºC and 67ºC. For the ratio-controlled experiment, the ratios were increased incrementally for each group, starting with a 10% increase, followed by a 15%; 20% and 25% increase in monomer. Water sorption and solubility were tested in accordance with ISO Standard 1567 (1999). Specimens were weighed before and after water immersion, and desiccation. Water sorption and solubility were calculated using the difference in wet and dry mass and the volume of the specimens. The water sorption and solubility results were analyzed by means of analysis of variance. For multiple comparisons, Bonferroni simultaneous confidence intervals (α=0.05) were applied. Results For the ratio-controlled experiment, water sorption mean values varied from 24.148 μg/mm3 to 25.1333 μg/mm3. Statistically significant differences in mean values were found between the following groups: 0%-10%; 0%-15%; 0%-25%; 10%-20%; 15%-20% and 20%-25% ratio groups (P<.0001). Water solubility mean values varied from 0.616μg/mm3 to 0.932μg/mm3. Statistically significant differences in mean values were found between the following groups: 0%-15%; 0%-20%; 0%-25% and 10%-25% and 20%-25% ratio groups (P<.0001). For the temperature-controlled experiment, water sorption mean values varied from 24.185μg/mm3 to 26.434μg/mm3. Statistically significant differences in mean values were found between the following groups: 37ºC-45ºC; 37ºC-55ºC; 37ºC-67ºC; 45ºC-67ºC and 55ºC-67ºC temperature-controlled experiments (P<.0001). Water solubility mean values, for the same experimental groups, varied from 0.616μg/mm3 to 2.752μg/mm3. Statistically significant differences in mean values were found among all the 6 pairs of groups (P<.0001). Despite statistical differences, the water sorption and water solubility values of the tested resin for both experiments and all groups were within the ISO Standard 1567 (1999) specification limits. Conclusion For the ratio-controlled experiment, there was an inverse relationship between the mean sorption and solubility values with an increase in liquid in the mixture: low water sorption levels are associated with high solubility levels. The lower water sorption and higher solubility results for more fluid mixtures could be related to initial and residual high monomer content characteristic of auto-polymerizing materials. These higher levels of free monomer are consequently released upon immersion in water; hence the higher water solubility levels. For the temperature-controlled experiment, a higher soaking temperature resulted in an increase in water solubility levels. The higher solubility levels could be attributed to the higher soaking temperatures causing higher or faster monomer diffusion from the resin material. Except for the 67ºC group, sorption is also lower with higher temperatures. It may be assumed that an additional polymerization process takes place and a subsequent more inaccessible polymer matrix is produced. For the 67ºC group, thermal expansion may explain the higher sorption level. Clinical Implications In terms of the sorption and solubility results, this auto-polymerizing pour-type resin may be used as a denture base resin. Even though statistical differences were demonstrated, the material satisfies the ISO 1567 (1999) requirements not only for auto-polymerizing but also for heat-polymerizing resins. Therefore, within limits, the mixture may be prepared more fluidly in order to improve flow of the material, without negatively affecting its sorption and solubility properties. Because solubility is higher at higher soaking temperatures, this property can be used to minimize monomer content of the appliance. Therefore, it is recommended that the dental appliance be soaked in warm water, below 67ºC, prior to delivery to the patient.