Ultimate micro-tensile strength of dental adhesives cured at different light source

This study determined the ultimate micro-tensile strength (mu UTS) of three dental adhesives cured with three different light sources; blue light-emittmig diode (LED), violet LED, and quartz-tungsten-halogen (QTH). Three dental adhesives, Clearfil SE Bond (SE), Unifil Bond (UB), and D/E Resin (DE), were examined. 0.7 mm-thick dental adhesive discs were prepared, trimmed into an hourglass shape, and the mu UTS was then measured at a cross-head speed of 1.0 mm/min (N=10). Additionally, the spectrum of each light source and the transmission spectrum of each adhesive were measured using a spectrometer. In SE, QTH showed the highest mu UTS among the different light sources, and no significant difference was found between blue LED and violet LED. While no significant difference was found in mu UTS between QTH and blue LED,violet LED indicated significantly lower mu UTS value in both UB and DE. The spectrometric analysis of blue LED, violet LED and QTH light sources showed,peaks at 471 mn (range: 440-510 mn), 404 nm (390-430 nm), and 492 nm (390-510 nm), respectively. In both UB and DE, transmittance was slightly decreased at the range of 390-510 film, the same peak/range as seen for camphorquinone which is included as a photoinitiator. On the other hand, in SE, a significant reverse peak at 360-420 nm was additionally observed. It was concluded that light wavelength affects the mu UTS of adhesive due to the differences in the photoinitiator.