engleski

Comparison of composite curing parameters: effect of light source and curing mode on conversion, temperature rise and polymerization shrinkage

The aim of this study was to analyze degree of conversion, temperature increase, and polymerization shrinkage in two hybrid composite materials polymerized with a halogen lamp using three illumination modes and a photopolymerization device based on blue light emitting diodes. The degree of conversion of Tetric Ceram (TC) (Ivoclar Vivadent, Schaan, Liechtenstein) and Filtek Z 250 (F) (3M/ESPE, St. Paul, MN, USA) was measured by Fourier transformation infrared spectroscopy at the surface and at the 2 mm depth ; temperature rise was measured by digital multimeter, and linear polymerization shrinkage was measured during cure by digital laser interferometry. Composite samples were illuminated by the quartz-tungsten-halogen curing unit (QTH) (Astralis 7, Ivoclar Vivadent, Schaan, Liechtenstein) under the following modes: &laquo ; ; high power&raquo ; ; (HH) 40 s at 750 mW/cm2, &laquo ; ; low power&raquo ; ; (HL) 40 s at 400 mW/cm2, and &laquo ; ; pulse/soft-start&raquo ; ; (HP) increasing from 150 to 400 mW/cm2 during 15 s followed by 25 s pulsating between 400 and 750 mW/cm2 in 2 s intervals and by light emitting diodes (LED) (Lux-o-Max, Akeda Dental, Lystrup, Denmark) with emitted intensity 10 s at 50 mW/cm2, and 30 s at 150 mW/cm2. Significantly higher temperature increase was obtained for both materials using the HH curing mode of halogen light compared to HP and HL modes and LED curing unit after 40 s. Significantly lower temperature values after 10 s illumination were obtained when LED was used compared to all halogen modes. For all curing modes, there was no significant difference in temperature rise between 20 and 40 s of illumination. The results for degree of conversion measurements show that there is significant difference in case of illumination of composite resin samples with LED on the surface and 2 mm depth. For the polymerization shrinkage, lower values after 40 s were obtained using LED compared to QTH.

composite resin; light source; degree of conversion; temperature rise; polymerization shrinkage

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