Long-term bond between dual-polymerizing cementing agents and human hard dental tissue

Objectives To examine the long-term adhesion of seven dual-polymerizing cementing agents to human dentin in vitro. Methods Two hundred and eighty extracted non-carious human molars were ground flat to expose dentin surfaces. The bond strengths of cementing agents with their respective bonding systems were examined: one compomer cement (PermaCem), five resin cements (RelyX ARC, Panavia F, Variolink II, Nexus 2, Calibra) and one self-adhesive universal resin cement (RelyX Unicem). One subgroup (n = 10) was tested after 150 days of storage in water at 37 °C (time t1), the other subgroup (n = 10) was tested after 150 days of storage plus 37,500 thermal cycles (time t2). All specimens were stressed in shear at a constant crosshead speed of 0.5 mm/min until failure. Statistical analysis was performed by ANOVA, taking effect interactions into account. The Tukey method was used for multiple paired comparisons (α = 0.05). Results The three-way ANOVA (cementing agents, polymerization methods, times of measurements) showed Variolink II to have the highest strength at 9.9 ± 4.5 MPa. Values were slightly higher at t1 (5.9 ± 4.7 MPa) than at t2 (4.9 ± 4.2 MPa) (p = 0.0044). Polymerization with light activation (6.5 ± 5.1 MPa) yielded higher strengths than polymerization without (4.3 ± 3.3 MPa) (p < 0.0001). Separate two-way ANOVAs for t1 and t2 showed that the two main effects (cementing agent, polymerization method) and their interactions differed significantly. Significance Cementing agents/adhesive systems and the polymerization method influence the long-term bond to hard dental tissues.