The purpose of this study was to determine the effectiveness of polymerization in the newly introduced blue light emitting diode (LED) (Experimental, SNU, Korea), and plasma arc curing (PAC) (Apollo 95E, Elite, DMD, USA) compared with conventional halogen lamp (Spectrum 800, Dentsply, USA). Various irradiation time with fixed intensity of light-curing units (LCUs) were irradiated to produce the same total light energy. The degree of double bond conversion (DC) of three resin composite (shade A3) was measured with a Fourier-transform infrared (FT-IR) spectrophotometer at various depths from the surface. Immediately after exposure to light, 100 microm thickness of resin composite was sectioned at the 1, 2, 3 and 4 mm from the top surface. The infrared spectrum of uncured resin and each wafer specimen were then obtained. The results were as follows: DC was significantly influenced by three variables of material, depth from the surface, and light source and energy level (P < 0.01). When the same light energy was irradiated, DC by plasma arc and LED was not significantly different from the halogen lamp (P > 0.05). When light energy was increased twice, no significant difference in DC was observed up to 2 mm from the surface (P > 0.05), but DC increased significantly from 3 mm (P < 0.05).
The objectives of this study were (1) to determine in vitro changes in surface roughness and color of dental resin composites after application of three finishing and polishing systems; (2) to evaluate the difference in color stability after immersion in a dye solution after polishing; and (3) to evaluate the effects of surface condition, especially roughness, on measured color depending on the color measuring geometries of specular component excluded (SCE) and specular component included (SCI). Color and surface roughness (R(a)) of resin composites of four brands of A2 shade and one brand of Yellow Enamel shade were measured after polymerization, after polishing with Enhance (Dentsply), Sof-Lex (3M ESPE), or Super-Snap (Shofu) composite finishing and polishing systems. Color was also measured after immersion in 2% methylene blue solution. Color was measured according to the CIELAB color scale. Color changes (DeltaE*(ab)) after polishing/staining and by the measuring geometry were calculated by the equation; DeltaE*(ab) = [(DeltaL*)(2) + (Deltaa*)(2) + (Deltab*)(2)](1/2). Ra value was measured with a surface roughness tester. DeltaE*(ab) and DeltaL* values after polishing and after staining varied among polishing systems when measured with SCE geometry. Composites polished with Super-Snap and Sof-Lex systems showed higher DeltaE*(ab) and DeltaL* values than those polished with Enhance polishing system with SCE geometry. DeltaE*(ab) and DeltaL* values between specimens with different surface conditions measured with SCE geometry were significantly higher than those with SCI (p < 0.01). Changes in R(a) value after polishing was insignificant in most cases.
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