Influence of viscosity and polymerization mode on bond strength of dual-cure resin luting agent to dentin

Aim: To evaluate the influence of the viscosity and curing mode on the bond strength of two resin cements to dentin.
Methods: Eight experimental groups were formed (n = 7) according to the dual-cure resin cements (Nexus 2 - Kerr Corp. and Variolink II - Ivoclar Vivadent), curing modes (dual-cure or self-cure) and viscosities (low and high). Resin cements were applied to pre-cured composite resin discs (2 mm thick, Sinfony -3M ESPE), which were fixed to bonded dentin surfaces. The restored teeth were either light-activated (XL3000 - 3M ESPE) or allowed to self curing only. After 24 h, the teeth were both mesiodistally and buccolingually sectioned to obtain bonded beam specimens (0.8 mm² cross-sectional area). Each specimen was tested in microtensile strength at a crosshead speed of 0.5 mm/min until failure.
Results: Data (in MPa) were analyzed statistically by three-way ANOVA and Tukey’s post-hoc test (pre-set á = 0.05). No significant difference was observed between resin cements (p=0.26) and viscosities (p=0.13), however, the curing mode affected the BS within the viscosities (p=0.01). Statistically significant difference was observed for low viscosity: Nexus 2: 23.8(10.6) (dual-cure) and 16.0(5.1) (self-cure); Variolink II: 28.7(8.7) (dual-cure) and 11.9(3.0) (self-cure).
Conclusions: Light activation yielded higher bond strength for the low-viscosity versions of the resin cements.