Methods: Ten samples of each of the following adhesives were prepared: AdheSE One (Ivoclar Vivadent), Clearfil 3S bond (Kuraray Medical), G bond (GC Corp), Xeno III (Dentsply DeTrey) and Adper Prompt L-Pop (3M ESPE). One drop of adhesive was smeared on a microscopic slide using a disposable applicator. A Mylar strip was placed on top of the adhesive which was then cured using a high intensity LED LCU (Elipar Freelight2, 3M ESPE; 1000 mW/cm2). Micro-Raman spectroscopy was used to determine DC by calculating the ratio of the number of unreacted methacrylate groups pre- and post-curing. The data were statistically analyzed using Kruskal-Wallis non-parametric test at 95% significance level.
Results: For all curing times, there were significant differences in DC values in each group, except for the Cleafil 3S group (p<0.01). At manufacturers’ recommended time of 10 s, the DC of adhesives showed decreasing order: G bond (76.01%±11.65%) > Clearfil 3S bond (73.54% ±7.53%) > AdheSE One (43.52%±8.44%) > Xeno III (40.65%±8.66%) > Adper Prompt L-Pop (27.71%±9.24%).
Conclusions: Curing time in excess of manufacturers’ recommended time showed higher DC values of all adhesives irrespective of their chemical composition. Dimethacrylate-based adhesives associated with milder acidic functional monomers showed the highest DC values.