Effect of Light Wavelength on Polymerization of Light-cured Resins

Abstract

Experimental light-cured composite resins were exposed to a narrow-band light at a constant quantum number using a narrow-band interference filter. The IR spectra of the cured resin specimens were measured before and after extraction of residual monomers. Degree of conversion (DC) and polymerization conversion (PC) were calculated from these IR spectra. The light in 410-550nm could be polymerized. With a brief exposure (5s), DC and PC were affected by the wavelength. The effect of wavelength between 410 and 490nm decreased with increasing duration of exposure. The most efficient wavelength was 470nm and the most adequate wavelength was in the 450-490nm wavelength range. The absorbance of camphorquinone strongly affected polymerization, especially during the initial stage. However, from the relationship between DC or PC and exposure energy, polymerization depended not only on the wavelength of the light, but also on the exposure energy.

Degree of conversion of adhesive systems light-cured by LED and halogen light

“…As a consequence, more free radicals are generated and faster monomer conversion will occur, resulting in higher DC in shorter time (12). Some studies have suggested that halogen light still produce greater curing energy and higher degree of composite monomer conversion than the first generation of LED lights (7,8,13).…”

“…A great amount of unpolymerized monomers from Clearfil SE Bond adhesive were detected by FTIR analysis immediately after LED photo-activation. Regardless of the lower power density emitted by LED (7,8,13), differences in resin adhesive composition and sample preparation might have affected the DC when LED LCU was tested. The mixture of Bond and Primer of Clearfil SE Bond results in a solution with low pH (approximately 2) and high water content, which can impair the polymerization reaction of the adhesive.…”

Effect of the increase of energy density on knoop hardness of dental composites light-cured by conventional QTH, LED and xenon plasma arc

“…The light intensity should be compatible with the absorption wavelength spectrum of the photoinitiator systems. For camphoroquinone, which is the most used photoinitiator system in dental composites, the maximum absorption peak is within the blue spectrum of visible light, about 468 nm (12). When similar energy densities are supplied to the composite resins, similar degrees of conversion and depth of polymerization will be obtained, regardless of the light-curing mode (9,10).…”

Effect of exposure time vs. irradiance on knoop hardness of dental composites

“…CQ is the photoinitiator most commonly used in dental composites. The maximum absorption peak fall within the blue band of visible light, at about 468 nm 18 . When the composite receives similar energy densities, similar degrees of conversion and polymerization depth will be obtained, regardless of the light-curing method.…”