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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Thus, the aim of this study was to evaluate the depth of cure and Knoop hardness using different photo-activation methods.
However, there were statistical differences between these, in which the LED demonstrated the lowest depth of cure. Effect of light wavelength on polymerization of light-cured konop.
However, the intermittent light revealed a higher hardness value than the exponential technique. Effect of exposure time on the depth of polymerization of a visible light-cured composite resin.
Instead, one must correlate test results across the multiple hardness tests.
Knoop hardness test
The results showed that the depth of cure was higher with the intermittent light, followed by continuous light, exponential light, PAC and LED methods. At this depth, the continuous light method presented an intermediate value with no statistical difference from the other methods.
Since the polymerization process seems more dependent on 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. The Knoop hardness number is the ratio of the applied load to the area of the indentation, in accordance with the formula: The effect of cure rate on the mechanical properties of dental resins.
The Knoop hardness test showed that, up to a depth of 2 mm, all photo-activation methods provided similar values.
The light exposure time was 3 s. The accuracy of the conversion depends on the accuracy of the provided data and the resulting curve-fits, and on the valid ranges spanned by the different hardness tests.
Converted hardness values should be used for comparative purposes only. This could explain the lower depth of cure obtained with this method when compared to methods that use the halogen lamp. Thus, this study evaluated the depth of cure and the Knoop hardness of the P60 composite resin, using different photo-activation methods.
Influence knopp light intensity on polymerization shrinkage and integrity of restoration-cavity interface. Temperature transmission of high-output light-curing units through dentin. At 3 mm, the LED method presented the lowest value and the continuous light technique demonstrated an intermediate value and was statistically similar to the other methods.
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Dureza knoop de resinas compostas em função do número relativo de radicais livres
After opening the matrix, the uncured material was removed with a steel spatula and the polymerized composite was measured using a pachymeter. A higher degree of conversion can be obtained by using a high light intensity 4. Am J Dent ;6: This result may be due to the reduced photo-activation time used in PAC, representing a lower amount of energy 8,17 and a short time period for the light kniop reach deeper cureza of the material, since part of the light necessary for polymerization is absorbed and scattered by the already polymerized composite 1, 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.
At this depth, the continuous light method presented an intermediate value and was no different from the intermittent and exponential methods. 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. However, this higher intensity may result in greater polymerization shrinkage and greater marginal leakage 5. However, these innovative techniques require further investigation before they can be effectively applied in dental practice.
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. Furthermore, the continuous light method demonstrated no difference from exponential light and PAC methods.
Dureza Knoop de cimentos de ionômero de vidro indicados para o tratamento restaurador
Whilst all the photo-activation methods provided depth of cure values that fulfilled the requirements of the ISO 19there were differences observed between the methods at depths greater than 2 mm. Again, the probable explication for this occurrence may be the total amount of energy supplied to the camphoroquinone, even at great depth.
The resulting indentation is shaped like the diamond tool, with a long-to-short axis ratio of 7: This energy is calculated as the product of the output of the curing light unit and the time of irradiation and may be termed as energy density. After photo-activation, the brass matrix was opened and all uncured material was removed using a steel spatula.
Braz Dent J ; Polymerization contraction and conversion of light curing Bis-GMA-based methacrylate resins.