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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However, the LED demonstrated the lowest depth of cure. The development of new technologies for photo-activation of restorative composite resins has caused great interest among researchers To generate blue light, the lamps must be heated to very high temperatures 14resulting in the emission of heat through the curing light tip 15, The intermittent light demonstrated the highest depth of cure 6.
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. Polymerization contraction and conversion of light curing Bis-GMA-based methacrylate resins.
However, the depth of cure value was lower than that obtained by methods that employ halogen lamps. Furthermore, the continuous light method demonstrated no difference from exponential light and PAC methods. The results showed that the depth of cure was higher with the intermittent light, followed by continuous light, exponential light, PAC and LED methods. 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 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, 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.
Determination of radiation energy emitted by light activation units. 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.
Brinell 10 mm Tungsten kgf. Effect of exposure time on the depth of polymerization of a visible light-cured composite resin.
Knoop hardness test
Braz Dent J ; However, there were statistical differences between these, in which the LED demonstrated the lowest depth of cure. Effect of light exposure on fracture toughness and flexural strength of light-cured composites.
Evaluation of depth of cure and Knoop hardness in a dental composite photo-activated using different methods. 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.
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, However, the real advantages of these techniques are not yet totally known. This result may be due to the total amount of energy that reached the material at this depth.
Dureza Knoop de cimentos de ionômero de vidro indicados para o tratamento restaurador
Effect of light wavelength on polymerization of light-cured resins. The resulting indentation is shaped like the diamond tool, with a long-to-short axis ratio of onoop Effect of the photo-activation method on polymerization shrinkage of restorative composites. Factors affecting cure at depths within light-activated resin composites.
However, the intermittent light revealed a higher hardness value than the exponential technique.
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. The Knoop hardness number is the ratio of the applied load to the area of the indentation, in accordance with the formula: Dent Mater J ; Five readings were taken for each region and the arithmetic means were calculated for each region of the specimen.
Harrington E, Wilson HJ.
The intermittent light method had kmoop highest depth of cure 6. 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.
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. According to Peutzfeldt et al. Brinell 10 mm Standard kgf. After photo-activation, durrza brass matrix was opened and all uncured material was removed using a steel spatula.
The hardness value is above the acceptable range of the particular hardness scale. Hardness evaluation of a dental composite polymerized with onoop LED-based devices. Effect of light intensity and exposure duration on cure of resin composite.