Abstract
Rapid high-intensity light-curing of dental resin composites is attractive from a clinical standpoint due to the prospect of time-savings. This study compared the effect of high-intensity (3 s with 3,440 mW/cm2) and conventional (10 s with 1,340 mW/cm2) light-curing on micromechanical properties of conventional and bulk-fill resin composites, including two composites specifically designed for high-intensity curing. Composite specimens were prepared in clinically realistic layer thicknesses. Microhardness (MH) was measured on the top and bottom surfaces of composite specimens 24 h after light-curing (initial MH), and after subsequent immersion for 24 h in absolute ethanol (ethanol MH). Bottom/top ratio for initial MH was calculated as a measure of depth-dependent curing effectiveness, whereas ethanol/initial MH ratio was calculated as a measure of crosslinking density. High-intensity light-curing showed a complex material-dependent effect on micromechanical properties. Most of the sculptable composites showed no effect of the curing protocol on initial MH, whereas flowable composites showed 11–48% lower initial MH for high-intensity curing. Ethanol/initial MH ratios were improved by high-intensity curing in flowable composites (up to 30%) but diminished in sculptable composites (up to 15%). Due to its mixed effect on MH and crosslinking density in flowable composites, high-intensity curing should be used with caution in clinical work.
Highlights
Rapid high-intensity light-curing of dental resin composites is attractive from a clinical standpoint due to the prospect of time-savings
In the group of flowable composites, the 3-s curing resulted in 11–35% lower top MH values and 33–48% lower bottom MH values compared to the conventional curing
In the group of sculptable composites, a significant effect of the curing protocol was identified only for the MH values measured on the bottom specimen surface of CER, for which the 3-s curing resulted in 12% lower MH compared to the conventional curing
Summary
Rapid high-intensity light-curing of dental resin composites is attractive from a clinical standpoint due to the prospect of time-savings. Most of the sculptable composites showed no effect of the curing protocol on initial MH, whereas flowable composites showed 11–48% lower initial MH for high-intensity curing. Due to its mixed effect on MH and crosslinking density in flowable composites, high-intensity curing should be used with caution in clinical work. The development of materials and techniques in adhesive dentistry follows a continuous trend toward simplification of restorative procedures, as highlighted by the evolution of bulk-fill resin c omposites[1,2,3], universal adhesives[4], and high-intensity light-curing u nits[5]. During the last two decades, radiant exitances of LED curing units have gradually increased for a whole order of magnitude[14], leading to the corresponding adjustments to the meaning of “high-intensity” in the literature. Bis-GMA, Bis-EMA, UDMA, propoxylated bisphenol A CQ/amine + Ivodimethacrylate, DCP, cerin + Lucirin TPO β-allyl sulfone AFCT agent
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