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

This study analyzed the degree of conversion, temperature increase and polymerization shrinkage of 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) and Filtek Z 250 (F) (3M/ESPE) was measured by Fourier transformation infrared spectroscopy at the surface and 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 quartz-tungsten-halogen curing unit (QTH) (Astralis 7, Ivoclar Vivadent) under the following modes: "high power" (HH) 40 seconds at 750 mW/cm2, "low power" (HL) 40 seconds at 400 mW/cm2 and "pulse/soft-start" (HP) increasing from 150 to 400 mW/cm2 during 15 seconds followed by 25 seconds pulsating between 400 and 750 mW/cm2 in 2-second intervals and by light emitting diodes (LED) (Lux-o-Max, Akeda Dental) with emitted intensity 10 seconds at 50 mW/cm2 and 30 seconds at 150 mW/cm2.

Measurement of linear polymerization contraction using digital laser interferometry.

Polymerization shrinkage is an unavoidable consequence of resin composite photopolymerization and is one of the most important factors in determining the clinical quality and durability of composite filling. Many different methods of measuring polymerization shrinkage are described in the literature. Digital laser interferometry is a method that enables direct observation of polymerization shrinkage in real time.

Influence of light intensity from different curing units upon composite temperature rise.

The unavoidable consequence of composite resin photopolymerization is temperature rise in tooth tissue. The temperature rise depends not only on the illumination time, but also on light intensity, distance of light guide tip from composite resin surface, composition and shade of composite resin and composite thickness. The most commonly used units for polymerization today are halogen curing units, which emit a large spectrum of wavelengths.

Photopolymerization of composite resins with plasma light.

Everyday improvements in components and characteristics of composite materials have induced faster development of curing units. Besides standard halogen curing units and soft-start photopolymerization light sources, some experiments with argon and pulsed laser light and low intensity blue superbright light emitting diodes have been made. On the other hand, rapid polymerization with strong plasma light is also clinically applicable.

Composite conversion and temperature rise using a conventional, plasma arc, and an experimental blue LED curing unit.

The objective of this study was to evaluate the degree of conversion and temperature rise in three different composite materials when illuminated by an experimental light source [blue superbright light emitting diodes (LEDs)] and compared with plasma light and traditional photopolymerization unit. The degree of conversion and temperature rise were measured using Fourier transform infrared (FTIR) spectroscopy and digital multimeter, respectively. The results revealed significantly higher degree of conversion values in case of conventional curing than with other two light sources whereas temperature rise was significantly lower when blue LEDs and plasma light were used.