The physical characteristics of resin composite-calcium silicate interface as part of a layered/laminate adhesive restoration

Objectives. To compare in-vitro micro-shear bond strengths (mu SBS) of resin composite to calcium silicate cement (Biodentine (TM)) vs. glass ionomer cement vs. resin modified glass ionomer cement (RM-GIC) using an adhesive in self-etch (SE)/total etch (TE) mode after aging three substrates and bond and characterizing their failure modes.

Methods. Resin composite was SE/TE bonded to 920 standardized disks of Biodentine (TM), GIC & RM-GIC. Dividing samples into two groups, the first underwent early (t = 0 min, 5 min, 20 min, 24 h) or delayed (t = 2 wk, 1 month, 3 months, 6 months) substrate aging before bonding and mu SBS (t = 24 h) testing. In the second, adhesive was applied after either early (t = 5 min) or delayed (t = 2 wk) substrate aging and then tested after bond aging (t = 2 wk, 1 month, 3 months, 6 months). The failure modes were identified using stereomicroscope. SEM images of selected samples were analyzed.

Results. No significant differences were observed between (SE)/(TE) bonding modes (P = 0.42). With substrate aging, a significant reduction in mu SBS occurred between early and delayed time intervals for Biodentine (TM) (P = 0.001), but none for the GIC/RM-GIC (P = 0.465, P = 0.512 respectively). With bond aging, there was no significant difference between time intervals for all groups, except at 6 months for the GIC (P < 0.05). Modes of failure were primarily cohesive within all the substrates (68.82%) followed by adhesive failure at the resin-substrate interface (21.71%).

Significance. Biodentine (TM) is a weak restorative material in its early setting phase. Placing the overlying resin composite as part of the laminate/layered definitive restoration is best delayed for >2 wk to allow sufficient intrinsic maturation to withstand contraction forces from the resin composite. A total-etch or self-etch adhesive may be used.