MENEZES, Marco Aurélio de and MUENCH, Antonio. Relative number of free radicals and knoop hardness of composites. Rev Odontol Univ São Paulo [ online]. O objetivo deste trabalho foi avaliar a profundidade de polimerização e a dureza Knoop do compósito restaurador P60 fotoativado por diferentes métodos. cimentados com diferentes materiais; (2) a dureza Knoop de cimentos Palavras-chave: Pino de fibra de vidro, Integridade Marginal, Dureza Knoop, Cimento.
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Effect of light intensity and exposure duration on cure of resin composite. The results showed that the depth of cure was higher with the intermittent light, followed by continuous light, exponential light, PAC and LED methods.
Dureza Knoop de cimentos de ionômero de vidro indicados para o tratamento restaurador
Thus, the aim of this study was to evaluate the depth of cure and Knoop hardness durza different photo-activation methods. The spectral output of gallium nitride blue LED falls conveniently within the absorption spectrum of the camphoroquinone photo-initiator nm presented in most light-activated composite resins, thus no filters are required in LED light curing units 12, At a depth of 4 mm, the intermittent and continuous light methods demonstrated the highest hardness values without differences between them.
This fact may explain the lower hardness observed at 3 mm depth when LED was used. J Oral Rehabil ; Optical microscope resolution may limit the application of the Knoop hardness test due to the resulting shallow indentions. This could explain the lower depth of cure obtained with this durezs when compared to methods that use the halogen lamp. The light exposure time was 3 s. The effect of cure rate on the mechanical properties of dental resins. Determination of radiation energy emitted by light activation units.
Knoop hardness test
As a result, there is NO direct analytic conversion between hardness measures. Marginal adaptation of a restorative resin polymerized at reduced rate.
According to Sakaguchi and Berge 8dueeza light intensity is achieved at 0. Cordless LED curing unit. At this depth, the continuous light method presented an intermediate value with no statistical difference from the other methods.
eFunda: Convert Hardness: Knoop
The polymerized composite cylinder was measured using a digital pachymeter Digital pachymeter, model CDC, Mitutoyo, Japanwhich was positioned in the center of the specimen, determining the depth of cure. This study used the Filtek P60 composite resin 3M, St. After opening the matrix, the uncured material was removed with a steel spatula and the polymerized composite was measured using a pachymeter. The Knoop Hardness Test, using an elongated pyramidal indenter, is a micro-indentation method suitable for thin plastic sheets, thin metal sheets, brittle materialsor materials where the applied load must never exceed 3.
Effect of the photo-activation method on polymerization shrinkage of restorative composites. A higher degree of conversion can be obtained by using a high light intensity 4. The results of this study showed that the depth of cure is strongly affected by photo-activation methods.
Finishing and polishing were then performed with sandpaper of decreasing grits of, and The hardness value is above the acceptable range of the particular hardness scale.
At a depth of 3 mm, the LED demonstrated the lowest hardness value, while the continuous light method revealed an intermediate value with no statistical difference from the other methods. The PAC method employs a different technology in which the light is produced by two electrodes that are placed very close to each other, emitting light when a high voltage is applied rather than by heating a tungsten filament as a halogen lamp This heat transmission to the material may be, in part, responsible for the higher depth of cure values achieved using these methods, because the heat may increase the mobility of the monomers, increasing the probability of the occurrence of conversion.
Eur J Oral Sci ; The composite was then covered with a polyester strip and pressed with a glass slab to accommodate the material into the matrix.
The intermittent, continuous and exponential light methods supply energy for photo-activation via halogen lamps, and the white light must be filtered to emit only the blue spectrum of the visible light. Up to a depth of 2 mm, all methods revealed similar hardness values, but there were differences between them at other depths, at which LED demonstrated the lowest values followed by PAC.
Conversely, the intermittent light method employs 2 s of light exposure followed by 2 s without light, meaning that the maximum light intensity peak is achieved every time that the light is emitted.
Depth of cure and compressive strength of khoop composites cured with blue light emitting diodes LEDs. The development of new technologies for photo-activation of restorative composite resins has caused great interest among researchers This result demonstrates that despite the particular characteristics of each method, the light intensity and the exposure time were enough to adequately polymerize this thickness of composite.
The results of the depth of cure and the Knoop hardness are presented in Tables 2 and 3respectively. The light-activated composite resins, brought into practice in the ‘s, introduced expressive changes that made their satisfactory application in posterior teeth possible.
This result may be due to the reduced photo-activation time used in PAC, representing a lower amount durea energy 8,17 and a short time period durezza the light to reach deeper regions of the material, since part of the light necessary for polymerization is absorbed and scattered by the already polymerized composite 1, Services on Demand Journal. According to Peutzfeldt et al. Five specimens were prepared for dreza photo-activation method.
The Knoop hardness test showed that, up to a depth of 2 mm, all photo-activation methods provided similar values. Despite this scattering and absorbance of light, all other methods supplied higher amounts xureza energy to the composite and, thus, provided higher hardness values at 3 mm depth.
After photo-activation, the brass matrix was opened and all uncured material was removed using a steel spatula.
The intermittent light demonstrated the highest depth of cure 6. Since the polymerization process seems more dependent konop the total energy available for photo-activation than the light intensity property 8, 17this method may provide a higher amount of energy to the material, which may explain the higher depth of cure values achieved using the intermittent method.