ESR study on the photo polymerization of dental composites

ESR (Electron Spin Resonance) spectra in X-band and at room temperature, of dental composites containing Bis-GMA type resin were obtained after irradiated wit conventional curing lamp of visible-light and laser light of red, green and blue colors. The blue light is the most suitable to produce methacrylate free radicals needed to its polymerization. However, Vickers hardness number determined in samples cured with conventional light indicated that their hardness number are equivalent to that obtained with blue light even producing less radicals, probably because conventional lamp generates more heat in the sample which helps its polymerization. Examining samples irradiated with green light, which is inadequate for usual practice by its lacking in energy, it has observed that this material has a striking ability to post cure by itself. It has concluded that the observation made by Ottaviani and collaborators, in a previous publication, that the time recommended by composite makers was insufficient, analyzing only ESR measurements, must be revised. (author)