Continuous and gradual photo-activation methods: influence on degree of conversion and crosslink density of composite resins |
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Authors: | S?X?S?Costa M?R?Galv?o D?P?Jacomassi M?I?B?Bernardi A?C?Hernandes Email author" target="_blank">A?N?de?Souza RastelliEmail author M?F?Andrade |
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Institution: | 1.Department of Restorative Dentistry, Araraquara School of Dentistry,S?o Paulo State University-UNESP,Araraquara,Brazil;2.Laboratório de Biofot?nica, Grupo de óptica, Instituto de Física de S?o Carlos,Universidade de S?o Paulo,S?o Carlos,Brazil;3.Grupo de Crescimento de Cristais e Materiais Ceramicos, Instituto de Física de S?o Carlos,Universidade de S?o Paulo,S?o Carlos,Brazil |
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Abstract: | Thermal properties and degree of conversion (DC%) of two composite resins (microhybrid and nanocomposite) and two photo-activation
methods (continuous and gradual) displayed by the light-emitting diode (LED) light-curing units (LCUs) were investigated in
this study. Differential scanning calorimetry (DSC) thermal analysis technique was used to investigate the glass transition
temperature (T
g) and degradation temperature. The DC% was determined by Fourier transform infrared spectroscopy (FT-IR). The results showed
that the microhybrid composite resin presented the highest T
g and degradation temperature values, i.e., the best thermal stability. Gradual photo-activation methods showed higher or similar
T
g and degradation temperature values when compared to continuous method. The Elipar Freelight 2TM LCU showed the lowest T
g values. With respect to the DC%, the photo-activation method did not influence the final conversion of composite resins.
However, Elipar Freelight 2TM LCU and microhybrid resin showed the lowest DC% values. Thus, the presented results suggest that gradual method photo-activation
with LED LCUs provides adequate degree of conversion without promoting changes in the polymer chain of composite resins. However,
the thermal properties and final conversion of composite resins can be influenced by the kind of composite resin and LCU. |
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Keywords: | |
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