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During the curing process of light curing dental composites the mobility of molecules and molecule segments is reduced leading to a significant increase of the viscosity as well as the ion viscosity. Thus, the kinetics of the curing behavior of 6 different composites was derived from dielectric analysis (DEA) using especially redesigned flat sensors with interdigit comb electrodes allowing for irradiation at the top side and measuring the ion viscosity at the bottom side. As the ion viscosities of dental composites change 1-3 orders of magnitude during the curing process, DEA provides a sensitive approach to evaluate their curing behavior, especially in the phase of undisturbed chain growth. In order to determine quantitative kinetic parameters a kinetic model is presented and examined for the evaluation of the ion viscosity curves. From the obtained results it is seen that DEA might be employed in the investigation of the primary curing process, the quality assurance of ingredients as well as the control of processing stability of the light curing dental composites.
OBJECTIVES: The aim of this study is to investigate depth dependent changes of polymerization process and kinetics of visible light-curing (VLC) dental composites in real-time. The measured quantity - "ion viscosity" determined by dielectric analysis (DEA) - provides the depth dependent reaction rate which is correlated to the light intensity available in the corresponding depths derived from light transmission measurements. METHODS: The ion viscosity curves of two composites (VOCO Arabesk Top and Grandio) were determined during irradiation of 40s with a light-curing unit (LCU) in specimen depths of 0.5/0.75/1.0/1.25/1.5/1.75 and 2.0mm using a dielectric cure analyzer (NETZSCH DEA 231 with Mini IDEX sensors). The thickness dependent light transmission was measured by irradiation composite specimens of various thicknesses on top of a radiometer setup. RESULTS: The shape of the ion viscosity curves depends strongly on the specimen thickness above the sensor. All curves exhibit a range of linear time dependency of the ion viscosity after a certain initiation time. The determined initiation times, the slopes of the linear part of the curves, and the ion viscosities at the end of the irradiation differ significantly with depth within the specimen. The slopes of the ion viscosity curves as well as the light intensity values decrease with depth and fit to the Lambert-Beer law. The corresponding attenuation coefficients are determined for Arabesk Top OA2 to 1.39mm(-1) and 1.48mm(-1), respectively, and for Grandio OA2 with 1.17 and 1.39mm(-1), respectively. For thicknesses exceeding 1.5mm a change in polymerization behavior is observed as the ion viscosity increases subsequent to the linear range indicating some kind of reaction acceleration. SIGNIFICANCE: The two VLC composites and different specimen thicknesses discriminate significantly in their ion viscosity evolution allowing for a precise characterization of the curing process even with respect to the polymerization mechanism.
V článku jsou uvedeny stupně, kterými prochází proces medicinalizace, a to identifikace, klasifikace, diagnóza, intervence a prognóza. Tyto stupně jsou stručně vymezeny. Je poukázáno na kladné i záporné stránky tohoto fenoménu, který je významným vedlejším produktem růstu poznatků v oblasti medicíny. Sociologický přístup k medicinalizaci je kritický. Sociologové uvádějí, že kromě aspektů „společenské kontroly“ v lékařské praxi existuje rovněž nepřímý „kontrolní“ účinek medicinalizace, který je daleko mocnější. Zaměřením se výhradně na pacienta individualizuje lékař společenské problémy. Avšak mnoho vážných nemocí má společenské a environmentální rozměry. Mnoho smrtelných nemocí je podmíněno chudobou, špatným bydlením, nepříznivým přírodním prostředím a také rizikovými pracovními podmínkami. Lékařská hegemonie je však i výsledkem skutečného úspěchu v léčbě některých nemocí. Tak jak se lékařská terminologie rozšířila do mnoha lidských aktivit a na řešení řady problémů, objevují se ve stále větší míře demedicinalizační a deprofesionalizační snahy. V současné době jsme svědky demedicinalizačních procesů, kdy se lékaři i pacienti pokusili v řadě případů odstranit některé aspekty lidského chování z dosahu medicíny. Někteří kritikové medicinalizace se snaží redefinovat aspekty života, jakými jsou např. narození, smrt apod., jako soukromé záležitosti, ve kterých by měly být lékařské zásahy limitovány. Ačkoliv tyto snahy jsou jen počátkem odporu proti medicinalizaci společnosti a zdají se být dosud izolovanými výjimkami „medicinalizačního“ trendu, upozorňují i na určité problémy v tomto započatém boji.
The article contains degrees through which the medicinalization process passes, i.e. identification, classification, diagnosis, intervention and prognosis. These degrees are shortly demarcated. Positive and negative sides of this phenomenon are pointed out, which is a significant secondary product of growth of knowledge in the sphere of medicine. Sociological approach to medicinalization is critical. Sociologists state that, in addition to aspects of „social control“, there is also indirect „checking“ effect of medicinalization in medical praxis, which is much more powerful. By focusing exclusively on the patient, the physician individualizes social problems. But a number of serious illnesses have social and environmental dimensions. A lot of fatal diseases are conditioned by poverty, bad housing, unfavourable natural environment and also risk working conditions. But medical hegemony is also result of real success in curing some diseases. As the medical terminology has spread in a lot of human activities and to the solution of a lot of problems, demedicinalization and deprofessionalization efforts emerge more and more. At present we witness demedicinalization processes when physicians and patients have tried to eliminate some aspects of human behaviour out of reach of medicine in a number of cases. Some critics of medicinalization try to redefine aspects of life like e.g. birth, death etc. as private affairs in which medical intervention should be limited. Although these efforts constitute only the beginning of resistance against medicinalization of the society and seem to be isolated exceptions of „medicinalization“ trend so far, they also point out certain problems in this fight initiated.
Typically, polymeric composites containing nanoparticles are realized by incorporating pre-made nanoparticles into a polymer matrix by using blending solvent or by the reduction of metal salt dispersed in the polymeric matrix. Generally, the production of pre-made Au NPs occurs in liquids with two-step processes: producing the gold nanoparticles first and then adding them to the liquid polymer. A reproducible method to synthetize Au nanoparticles (NPs) into polydimethylsiloxane (PDMS) without any external reducing or stabilizing agent is a challenge. In this paper, a single-step method is proposed to synthetize nanoparticles (NPs) and at the same time to realize reproducible porous and bulk composites using laser ablation in liquid. With this single-step process, the gold nanoparticles are therefore produced directly in the liquid polymer. The optical properties of the suspensions of AuNPs in distilled water and in the curing agent have been analyzed by the UV-VIS spectroscopy, employed in the transmission mode, and compared with those of the pure curing agent. The electrical dc conductivity of the porous PDMS/Au NPs nanocomposites has been evaluated by the I-V characteristics. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis have monitored the composition and morphology of the so-obtained composites and the size of the fabricated Au nanoparticles. Atomic force microscopy (AFM) has been used to determine the roughness of the bulk PDMS and its Au NP composites.
Selected biosorbents, brewers draff and grape waste, have been encapsulated in calcium alginate beads and used for the removal of Cr(VI) from aqueous solutions. The effects of encapsulation variables, including the type of waste, the percentage of waste in the beads and the curing time of the beads in CaCl2, on the diameters of the beads and Cr(VI) sorption kinetics have been evaluated. In total, 21 different types of beads were produced. The diameters of the beads increased with increasing amounts of encapsulated biomaterial. Beads that contained grape waste were larger than those containing brewers draff. The most efficient beads for Cr(VI) removal were beads that contained 4% (w/w) of grape waste. No significant differences in the kinetics of Cr(VI) sorption were found with respect to the curing time variable in the case of grape waste calcium alginate beads. Statistical analysis confirmed that the type and percentage of waste are the critical parameters influencing the diameters of the beads and Cr(VI) removal. It was proven that the sorption efficiencies of the beads containing draff and grape waste encapsulated under the optimum conditions were much higher than the efficiencies obtained when using both wastes in their native states.
- MeSH
- adsorpce MeSH
- algináty chemie MeSH
- chrom chemie izolace a purifikace MeSH
- kinetika MeSH
- kyselina glukuronová chemie MeSH
- kyseliny hexuronové chemie MeSH
- látky znečišťující životní prostředí chemie izolace a purifikace MeSH
- odpadní produkty MeSH
- roztoky MeSH
- tobolky MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- dentální technologie MeSH
- lidé MeSH
- stomatologická protetika MeSH
- vazba zubní metody MeSH
- výsledky a postupy - zhodnocení (zdravotní péče) MeSH
- zubní korunky MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- kazuistiky MeSH
ETHNOPHARMACOLOGICAL RELEVANCE: Scorzonera latifolia (Fisch. & Mey.) DC. (Asteraceae) grows naturally in Eastern Anatolia, northeastern Iran, and Caucasus. Latex of S. latifolia roots is used in Turkish folk medicine for its analgesic effects, externally to cure infertility in women, and internally as an antihelmintic. The milk obtained from the stem of the Scorzonera species is used for wound healing activity. Antinociceptive, anti-inflammatory, wound-healing, antioxidant, and antimicrobial activities have previously been reported for S. latifolia. AIM OF THE STUDY: A methanol extract of the aerial parts of Scorzonera latifolia that had been shown to possess wound-healing activity, was used to elucidate the possible mechanism of the wound-healing activity and to identify the compound(s) responsible for the effect by means of bioassay-guided fractionation. MATERIALS AND METHODS: The wound-healing activity potential of methanol extract of S. latifolia was detected by evaluating the inhibitory activity on the collagenase, hyaluronidase and elastase, which play important roles in the wound-healing process. Succesive fractionation of the methanol extract using petroleum ether, chloroform, ethyl acetate, respectively, and the residual wateryielded four respective fractions. The ethyl acetate part, which was determined as the most active fraction, was selected for further separation using chromatographic techniques. RESULTS: Ethylacetate fraction exhibited significant inhibitory activities on collagenase and elastase. Chromatographic separation of the ethylacetate extract yielded an active subfraction, from which was used to isolate quercetin-3-O-β-apiofuranosyl-(1'''→2'')-β-D-glucopyranoside (1), quercetin-3-O-α-rhamnopyranosyl-(1→6)-β-D-galactopyranoside (2), isoorientin (3), and 7-methylisoorientin (4). Of the compounds tested, 7-methylisoorientin (4) exerted inhibitory activity on collagenase and elastase, while quercetin-3-O-β-apiofuranosyl-(1'''→2'')-β-glucopyranoside (1) inhibited collagenase only. None of the fractions, or isolated compounds showed any inhibitory effect on hyaluronidase. It must be mentioned, that in vitro tests showed that compounds 1-4 inhibit the collagenase and elastase and could help wound-healing process. However, the inhibititory effect of the methanol extract appears to be greater than that of both of the ethylacetate fraction, subfraction G and the isolated compounds, which suggest that a synergistic interaction of several compounds could be responsible for the wound-healing activity of the aerial parts of S. latifolia.
- MeSH
- analgetika chemie MeSH
- antiflogistika chemie MeSH
- hojení ran MeSH
- hyaluronoglukosaminidasa antagonisté a inhibitory MeSH
- inhibitory matrixových metaloproteinas chemie MeSH
- kolagenasy chemie MeSH
- nadzemní části rostlin MeSH
- pankreatická elastasa antagonisté a inhibitory MeSH
- rostlinné extrakty chemie MeSH
- Scorzonera * MeSH
- tradiční lékařství MeSH
- Publikační typ
- časopisecké články MeSH
- Geografické názvy
- Turecko MeSH
- Klíčová slova
- mikronetěsnost, polymerační kontrakce, polymerační smršťování,
- MeSH
- fyzikální jevy MeSH
- lidé středního věku MeSH
- lidé MeSH
- mandibula MeSH
- moláry MeSH
- netěsnost výplní prevence a kontrola MeSH
- obturace kořenového kanálku * MeSH
- polymerizace MeSH
- povrchové napětí MeSH
- povrchové vlastnosti MeSH
- složené pryskyřice terapeutické užití MeSH
- stomatologické polymerizační lampy využití MeSH
- syndrom prasklého zubu * terapie MeSH
- trvalá zubní náhrada metody MeSH
- zubní čepy * využití MeSH
- zuby neživé MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- ženské pohlaví MeSH
- Publikační typ
- kazuistiky MeSH
- MeSH
- dentální adheziva tuhnoucí světlem * metody ošetřování MeSH
- estetika stomatologická MeSH
- kompomery * terapeutické užití MeSH
- leptání zubů kyselinou metody MeSH
- lidé MeSH
- optické jevy MeSH
- řezáky MeSH
- světlo MeSH
- trvalá zubní náhrada * metody MeSH
- zuby-sanace - opotřebování * klasifikace MeSH
- Check Tag
- lidé MeSH
Úvod: Po testování pevnosti vazby jednotlivých adhezivních materiálů je k dispozici pouze údaj o tom, jakému zatížení jsou tyto materiály schopné odolat Pokud je nutné zjistit, na kterém místě došlo k oddělení zámku, resp. selhání vazby, lze stanovit pro jednotlivé povrchy tzv. ARl - Adhesíve Remnant Index. Jedná se o ukazatel, který pomáhá určit místo, kde došlo k porušení vrstvy adheziva. Podle výsledků potom lze stanovit, zda došlo k porušení vazby na povrchu báze zámku, na povrchu zubu nebo přímo ve vrstvě samotného adheziva. Význam stanoveníARI spočívá ve využití v oblasti výzkumu a v možnosti cíleně zvýšit pevnost vazby ortodontických adhezivních materiálů. Cíl: Stanovit ARl pro různé ortodontické adhezivní materiály na různých površích. Materiál a metodika: Testovány byly adhezivní systémy BrackFix NT, Neobond TM a Transbond TM XT ze skupiny kompozitních materiálů, GC Fuji ORTHO TM, GC Fuji ORTHC TM LC ze skupiny skloionomemích cementů I akrylátová pryskyřice Spofacryl. Testovanými povrchy byly sklovina extrahovaných premolárů, kompozitní fazety, pryskyřičné korunky a keramické plošky metalokeramických korunek. Bylo použito celkem 486 vzorků, u kterých byla měřena pevnost vazby adhezivních materiálů. Všechny povrchy, na kterých byla cestovaná pevnost vazby jednotlivých ortodontických lepidel, tedy báze zámku i povrch skloviny (resp. umělý povrch na který byl zámek lepen), byly fotograficky dokumentovány pomocí zvětšovací lupv. Poté byla přes každý obrázek proložena mřížka, která oblast báze zámku a lepeného povrchu rozdělila na 16 stejných polí ve 4 řadách a 4 sloupcích a přítomnost lepidla v jednotlivých políčkách byla zaznamenána do tabulek. Výsledky byly statisticky vyhodnoceny, a bylo provedeno také statistické srovnání jednotlivých měření pomocí Kruskall-Wallis ANOVA testu. Výsledky: Na všech testovaných površích byly zjištěny statisticky významné rozdíly při hodnocení ARl mezi adhezivními systémy. Největší počet selhání vazby ve vrstvě adheziva jsme sledovali u pryskyřice Spofacryl. Kompozitní materiály zůstávaly na povrchu zubu ve větší míře než skloionomerní cementy, na bázi zámku tomu bylo naopak. Ve většině případu bylo možno pozorovat stejné chování materiálu v rámci jedné materiálové skupiny. v některých případech byla také potvrzena závislost velikosti pevnosti vazby a ARI. Závěr: Jednotlivé adhezivní systémy se od sebe liší v množství zanechaných zbytků lepidla na bázi zámku a testovaném povrchu a existuje závislost mezi velikostí pevnosti vazby a lokalizací zbytků lepidla. Výsledky je možno využít 't v oblasti výzkumu a zjištěné údaje je možno aplikovat v praxi. Práce byla podporována projektem SVC 1M0528.
Introduction: After testing individual adhesives the only one infonmation is available - the amount of load the materials can resist In case we need to determine at which place the bracket debonding occurred, or where the bond failed, we can use the so-called ARl - Adhesive Remnant Index. ARl helps to identify the place wnere the adhesive's layer got damaged. The results help to decide whether the bond was damaged at the bracket base surface, tooth surface, or In the layer of the adhesive itself. ARl thus helps to study and increase the bond strength of orthodontic adhesive materials. Aim: Determine ARl for different orthodontic adhesives on different types of surfaces. Materials and metifiods: We tested adhesive systems BrackFix NT, NeobondTM and TransbondTM XTof composlte materials, GC Fuji ORTHO TM, GC Fuji ORTHO TM LC of glass ionomer cements, and acrylic resin Spofacryl®. The surfaces tested were: enamel of extracted premolars, composite veneers, acrylic resin crowns, and ceramie veneers of metal-ceramic crowns. The strength of adhesive materials bond was measured in 486 samples. All surfaces used for the testing, i.e. bracket base as well as the enamel surface (or an artificial surface to which the bracket was attached) were photographed with the help of a magnifying glass. Then a grid (4 columns and 4 lines) was put over each photograph, and the remnants of an adhesive in individual plots were recorded in tables. The results were statistically processed, and statistical comparison of individual measurements was performed. Results: Statistically significant differences of ARl of individual adhesives were found in all the surfaces tested. The greatest number of bond failures in the adhesive layer was recorded for the Spofacryl resin. Composites remained on the tooth surface more often than glass ionomer cements (in case of the bracket base the situation was just opposite). We observed the same behavior within the same group of materials. The correlation between a bond strength and ARl was observed in some cases. Conclusion: Individual adhesive systems differ in the amount of adhesive remnants on the bracket base and the surface tested; there is the dependence between the bond strength and location of adhesive residuals. The results may be used in further research, and the data obtained are to be applied in practice. The work was supported by the project SVC 7M0825.
