curing
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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.
Cíl: Cílem studie bylo upozornit na důležitý význam hygieny v ordinaci zubního lékaře, a to konkrétně ve vztahu k zubním polymeračním lampám jako možnému zdroji infekčního agens a následného šíření nemocničních nákaz. Materiál a metodika: Do souboru bylo zahrnuto 59 bakteriálních stěrů z povrchu polymeračních lamp. Výsledky: Z kultivačních výsledků převažují grampoziťivní bakterie s dominancí koaguláza negativních stafyokoků (CoNS). V jednom případě byl prokázán Staphylococcus aureus. Pouze v jednom případě byla prokázána gramnegativní bakterie, a to kmen Pseudomonas aeruginosa. Dle bakteriální kultivace byly pouze dvě polymerační lampy kultivačně negativní. Závěr: Epidemiologické šetření ukázalo špatnou konečnou dekontaminaci polymeračních lamp a jejich nevhodné uložení po skončení pracovní doby, kdy jsou vystaveny spadu prachových částic jako možného nosiče infekčního agens.
Aim: The study aims to focus on the importance of hygiene in the dentist offices, specifically in relation to dental light-curing units as a potential source of infectious agent and the resulting spread of hospital infections. Material and methods: The sample included 59 bacterial swabs from polymerization lamps surfaces. Results: Withih cultivation results gram-positive bacteria prevail dominated by coagulase-negative staphylococci (CoNS). In one case Staphylococcus aureus was proved. Only in one sample a gram-negative bacterium was proved, specifically genus Pseudomonas aeruginosa. Bacterial cultivation showed that only two polymerization lamps had negative results. Conclusion: Epidemiological examination proved unsatisfactory final decontamination of polymerization lamps and their inappropriate deposition after office hours - they were exposed to dust particles that are potential carriers of infectious agent.
Cílem práce bylo porovnat účinnost několika typů halogenových a LED polymeračních lamp při vytvrzování různých typů kompozitních materiálů. Sledovány byly halogenové lampy Heliolux DLX1 (Ivoclar Vivadent) a Megalux Fast Cure (Mega Physik), LED lampy zahrnující DioPower (CMS Dental), Translux Power Blue (Heraeus Kulzer), BluePhase C8 (Ivoclar Vivadent) s úzkým emisním spektrem (skupina LED 1) a LED lampy G-Light (GC) a BluePhase G2 (Ivoclar Vivadent) s emisí v širší oblasti světla (skupina LED 2). Hodnocení lamp bylo provedeno měřením tvrdosti horní ozářené a spodní neozářené strany tělísek tloušťky 2 mm, zhotovených z radikálově iniciovaného dimetakrylátového kompozitního materiálu Charisma (Heraeus Kulzer) a epoxidového kompozitu Filtek Silorane (3M ESPE) s kationtovým mechanismem polymerace. U obou materiálů byl pozorován významný vliv polymerační lampy na tvrdost, a tedy i stupeň vytvrzení kompozitního materiálu. Nejvyšší tvrdost pro kompozit Charisma byla nalezena při jeho polymeraci halogenovými lampami a lampou BluePhase G2. V případě epoxidového kompozitu Filtek Silorane bylo nejvyšších hodnot tvrdosti dosaženo s oběma LED 2 lampami a s halogenovými typy lamp. I přes omezený rozsah hodnocených polymeračních lamp se ukázalo, že nejvyšší účinnosti polymerace lze dosáhnout s lampami se širokým emisním spektrem, především výkonnými halogenovými typy a LED lampami s diodami emitujícími světlo i v oblasti kratších vlnových délek.
The objective was to compare efficacy of several types of halogen and LED polymerization lamps in curing restorative composite materials. Halogen lamps Heliolux DLX1 (Ivoclar Vivadent) and Megalux Fast Cure (MegaPhysik) and LED lamps DioPower (CMS Dental), Translux Power Blue (Heraeus Kulzer), BluePhase C8 (Ivoclar Vivadent) of a narrow spectral emission (group LED 1) and G-Light (GC, USA) and BluePhase G2 (Ivoclar Vivadent) of a broad spectral emission (group LED 2) were used. Curing efficacy was evaluated by measuring the composite hardness on the top irradiated and bottom not-irradiated surfaces of 2 mm thick specimens prepared from radically initiated dimethacrylate-based composite material Charisma (Heraeus Kulzer) and epoxy-based cationically polymerized composite material Filtek Silorane (3M ESPE). In curing of both composite materials a significant effect of the polymerization lamp on composite hardness and hence, polymerization degree was observed. The highest hardness of the composite material Charisma was found after polymerization with the halogen lamps and also BluePhase G2 of a broad spectral emission. With the epoxy-based Filtek Silorane the highest surface hardness was reached with both LED 2 and halogen lamps. In spite of limited number of polymerization lamps tested it seems obvious that the highest polymerization degree can be reached with polymerization lamps of broad spectral emission, such as high-power halogen lamps or LED lamps equipped with diodes emitting light in a short wavelength range.
