To measure in-vitro micro-shear bond strengths (µSBS) of resin composite (N’Durance®) to a tri-calcium silicate cement (Biodentine™) vs. glass ionomer cement (GIC - Fuji IX™) and resin modified glass ionomer cement (RM-GIC, Fuji II LC™) using an adhesive (Scotchbond™ Universal) in self-etch mode (SE) and total etch (TE) mode while aging the 3 substrates and bond at time intervals and characterising the failure modes.
Method:
Resin composite was SE / TE bonded to 920 discs of Biodentine™, GIC & RMGIC. Dividing samples into 2 groups, the first group underwent early substrate aging (t=0 min, 5 min, 20 min, 24 hrs) or delayed (t=2 wks, 1month, 3 months, 6 months) before bonding and the bond strength (t=24 hrs) tested. In the second, the bonding agent was applied after either early (t=5 min) or delayed (t=2 wks) substrate aging, and then the bond tested after aging for time intervals (t=2 wks, 1month, 3 months, 6 months). The failure modes were identified using SEM.
Result:
Significant differences in µSBS occurred between Biodentine™, GIC, & RMGIC (P<0.001). No significant differences were found between (SE) and (TE) bonding modes (P=0.42). With substrate aging, a significant difference in µSBS occurred between early and delayed time intervals for Biodentine™ (P=0.001), but none for the GIC / RM-GIC substrates (P=0.465, P=0.512) respectively. When aging the bond, there was no significant difference between time intervals for all groups, except at 6 mths for the GIC substrate. Modes of failure were mostly cohesive within the substrate (68.82%) followed by adhesive failure at the resin-substrate interface (21.71%).
Conclusion:
Biodentine™ is weak in its early setting phase. Placing the veneer restoration is best delayed for 2 weeks to allow sufficient setting to withstand the contraction forces of the resin composite. A total etch or self-etch adhesive may be used.