Effect of Delayed Photoactivation and Touch-Cure Mechanism on the Polymerization Kinetics of a Universal Resin Cement

To investigate the effect of the touch-cure mechanism of Scotchbond Universal Plus adhesive system and different light-curing delay periods on the polymerization kinetics of RelyX Universal dual-cure resin cement (URC).

The resin cement, alone or combined with the adhesive system, was light cured after 0, 1, 3, 5, 10, 15, or 20 min of delay, or left without light (control). Degree of conversion (DC; n = 3) and maximum polymerization rate (Rp_max; n = 3) were measured and analyzed by two-way ANOVA and Tukey's test (α = 0.05).

With adhesive, DC significantly increased at 10- and 15-min delays, and also in the control, while without adhesive, no difference was observed among delays. The lowest DC occurred in the control of both conditions. Rp_max was significantly reduced at dark cure and at 20 min delay (without adhesive), at dark cure, and at 15- and 20-min delays (with adhesive). The adhesive further reduced Rp_max at 10- and 15-min delays.

Ten and 15-min light-curing delays enhanced DC and Rp_max of URC, particularly with Scotchbond Universal Plus. Even without light, the adhesive-cement interaction promoted effective polymerization.