Abstract
This study evaluated the effect of blue light emitting diode (LED) and quartz tungsten halogen (QTH) on the degree of conversion (DC) of an etch-and-rinse Single Bond adhesive system (SB) and a mixture composed of primer solution and resin bond from Clearfil SE Bond self-etching adhesive system (CB) using Fourier transform infrared analysis (FTIR). Adhesives were applied to potassium bromide pellet surfaces and FTIR analyses were performed before and after photo-activation for 10 s with either LED (Freelight 1 - 400 mw/cm(2)) or QTH (XL 3000 - 630 mw/cm(2)) light-curing units (n=8). Additional FTIR spectra were obtained from photo-activated samples stored in distilled water for 1 week. The DC was calculated by comparing the spectra obtained from adhesive resins before and after photo-activation. The results were analyzed by two-way split-plot ANOVA and Tukey's test (p<0.05). Both adhesive systems exhibited low DC (%) immediately after photo-activation (SB/QTH: 18.7 +/- 3.9; SB/LED: 13.5 +/- 3.3; CF/QTH: 13.6 +/- 1.9; CF/LED: 6.1 +/- 1.0). The DC of samples light-cured with LED was lower than DC of those light-cured with QTH, immediately after light curing and after 1 week (SB/QTH: 51.3 +/- 6.6; SB/LED: 50.3 +/- 4.8; CF/QTH: 56.5 +/- 2.9; CF/LED: 49.2 +/- 4.9). The LED curing unit used to photo-activate the adhesive resins promoted lower DC than the QTH curing unit both immediately after light curing and 1 week after storage in water.
Highlights
For many years quartz-tungsten-halogen bulbs have been used as the lighting source to photo-activate visible-light cured composite resins
Some factors may compromise the performance of halogen light curing units (LCUs), such as fluctuations in the line voltage, the condition of the bulb and filter, contamination of the light guide, damage to the fiber-optic bundle as well as bulb overheating within the unit
This study evaluated the degree of monomer conversion of two adhesive systems photo-activated with light emitting diode (LED) and halogen LCUs, using Fourier transform infrared (FTIR) analysis
Summary
For many years quartz-tungsten-halogen bulbs have been used as the lighting source to photo-activate visible-light cured composite resins. Some factors may compromise the performance of halogen light curing units (LCUs), such as fluctuations in the line voltage, the condition of the bulb and filter, contamination of the light guide, damage to the fiber-optic bundle as well as bulb overheating within the unit. These factors can contribute to reduce the efficiency and lifetime of halogen lamps, leading to poorly polymerized composite resins with impaired mechanical properties [1]. LED LCUs consume little power in operating and do not require filters to produce blue light. The gallium nitride LEDs produce a narrow wavelength peak around 470 nm, which matches the absorption peak value of camphorquinone, the most common photoabsorbing compound that initiates the polymerization of resin monomers in dental restorative composites [2]
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