engleski

EPR Registration of Polymerization in Composite Sample

The visible light cured resin composite materials contain camphorquinone (0.17-1.03%) in combination with (0.86-1.39%) N, N-dimethylaminoethyl methacrylate as photosensitizer. Through the influence of blue light occurs the initial photopolymerization step in the complicated process of material setting. Visible light induces cross-linking reactions and generation of radicals which initiate a chain process and ensure the propagation of the growing polymer chain. To check accuratley the polymerization dynamics, some experiments using Electron Paramagnetic Resonance Spectrometer VARIAN 109E (X band ) have been made. An EPR spectrum is a graphical representation of the absorption intensety under the resonance condition due to the magnetic field intensity. Composite materials Valux (3M, USA ) and Tetric (Vivadent, Liechtenstein) and their analogous unfilled resins Schotchbond and Heliobond were tested. Experiments were made with dark and light shades polymerized 10, 20 and 60 s under the temperature controlled conditions (37o C). The correlation between free radicals formation and the degree of conversion has been noticed. Signals obtained after 10 and 20 s. The level of EPR-registrated free radical concetration is directly correlated to the degree of conversion. ( This study was supported by the Ministry of Science and Technology of the Republic of Croatia)

polymerization; composite resins

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