Light-Curing Effects On Universal Adhesive Bonding To Dentine: 1Yr Results

Objectives: To evaluate the immediate vs 1-year bonding ability expressed as microtensile bond strength (mTBS) and nanoleakage (NL) expression of a simplified universal adhesive system used in combination with dual-cure resin cements with/out light activation.
Methods: Fourty-eight composite overlays (Venus Diamond) were luted to deep coronal dentin according to the following bonding procedures: 1) iBond universal adhesive/RelyX Ultimate cement (RXU; Heraeus Kulzer/3M); 2) iBond universal adhesive/Panavia V5 (PAN; Kuraray); 3) iBond universal adhesive/Variolink EstheticDC (VAR; Ivoclar Vivadent). Two subgroups were randomly formed according to the polymerization mode of the resin cements (n=4): self-cure mode (SC; 1h at 37°C) or dual-cure mode (DC; 20s light-cure followed by 15min self-cure at 37°C). Each specimen was cut into microtensile sticks (1mm²) and either immediately stressed to failure under tension or aged in artificial saliva for 1 yr before testing. The fracture pattern was evaluated under SEM. mTBS data were statistically analyzed with two-way ANOVA/Tukey’s test (p=0.05) including premature failures. Additional specimens (n=2) were processed for quantitative interfacial NL expression using ammoniacal silver nitrate.
Results: The factor “SC” statistically influenced the mTBS of the tested materials either at 24h or 1-yr of storage (p<0.05). RXU/DC attained the highest immediate bond strength results (40.8±10.4), while PAN/SC recorded the lower mTBS among the groups at 24h (17.0±8.0). After 1yr, the bond strength of all the tested groups decreased (p<0.05) and no statistically differences were present between the materials when used in the DC mode. NL resulted in higher deposition of AgNO3 granules when the materials were only SC. Nanoleakage increased after aging for the PAN and VAR groups.
Conclusions: Light-cure influences the bonding ability of simplified bonding systems compared to the self-cure modality. Storage time significantly affected the bond strength results and nanoleakage expression of the tested materials.