Influence of light curing time and overlying ceramic thickness on polymerization kinetics of conventional and self-adhesive dual-cure resin cements

Abstract

The purpose of this study was to investigate the influence of light curing time and overlying ceramic thickness on the polymerization of conventional and self-adhesive dual-cure resin cements. Two conventional dual-cure resin cements (Rely-X ARC, Duolink) and two self-adhesive dual-cure resin cements (Rely-X U200, Maxcem Elite) were polymerized under different curing modes (dual-cure or self-cure), curing times (20 and 120 seconds), and different thickness of a ceramic overlay (2 and 4 mm). Polymerization kinetics was measured by FTIR for the initial 10 minutes and after 24 hours. Data were analyzed using one-way ANOVA/Student-Newman-Keuls post hoc test, and paired t-test (α=0.05). When light curing time was set to 20 seconds, the presence of the ceramic block significantly affected degree of conversion (DC) of all resin cements (p<0.05). Especially, the DC of the 4 mm-20 sec group was significantly lower than that of the self-cured groups at 24 hours after polymerization (p<0.05). However when light curing time was set to 120 seconds, a similar DC compared to the positive control group (p>0.05) was achieved in all dual-cure groups except Maxcem Elite, at 24 hours after polymerization. Curing modes (dual-cure or self-cure), curing times (20 and 120 seconds), and ceramic overlay thickness (2 and 4 mm) significantly affected the DC of conventional and self-adhesive dual-cure resin cements. When a ceramic restoration thickness is 4 mm or greater, 20 seconds of light curing time could result in a poor extent of polymerization, even lower than that of self-curing alone. Prolonging light curing time (120 seconds) could be an option to improve polymerization of conventional and self-adhesive dual-cure resin cements.