engleski

Degree of conversion of pulsed laser cured composites

Clinical performance of visible-light curing composites is greatly influenced by the quality of photopolymerization. Some drawbacks of currently used photopolymerizhation units necessitate the search for new light sources. In this study, comparison was made between the degree of conversion of two hybrid composites (Tetric, Vivadent, Schaan, Liechtenstein and Pekafill, Byer, Leverkusen, Germany) of light and dark shade, as illuminated by a conventional halogen lamp and by pulsed laser upon the surface and at depths of 1.0, 2.0 and 3.0 mm. In order to compare these two methods the total energy during the illumination time by the pulsed laser was kept equal or somewhat smaller than in case of halogen lamp illumination. Composite resin samples were prepared in the same way for both the standard photopolymerization technique (Heliolux GTE, Vivadent, Schaan, Liechtenstein) and pulsed laser illumination. The degree of conversion of cured samples was measured by Fourier Transform Infrared Spectroscopy (FTIR). Results obtained by the analysis of the pulsed laser.induced polymerization were signigicantly higher for all the materials and all shades observed. All values of the degree of conversion were lower for dark shades of both composites, regardless of the photopolymerization technique used. THese values varied from 79, 2%to 84, 5% for pulsed laser (including all depths) and fron 42.7% to 74.7% for standard polymerization. The measured values of the degree of conversion were analyzed using analysis of variance. Very weak dependence of the degree of conversion, between the surface measurements and those at 3.0 mm were observed in case of pulsed laser polymerization dut to the saturation dffect induced by the high power nanopulses and monochromatic light of appropriate wavelength at 468 nm.

degree of conversion; composite resins

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