Impact of immediate versus delayed dentin sealing on adhesive luting effectiveness

To evaluate the effect of immediate versus delayed dentin sealing (IDS/DDS) on the micro-tensile bond strength (µTBS) of CAD/CAM composite adhesively luted onto dentin.

Upon sandblasting, silanization and adhesive application, CAD/CAM composite slabs were luted (AL) onto dentin using composite following eight protocols: ₁'DDS_LC': C-SE2 light-cured (LC) on dentin prior to AL; ₂'DDS_prov': temporary, saliva storage, C-SE2 LC, AL; ₃'DDS_noLC': C-SE2 (non-LC), AL; ₄'DDS_{pulpless_noLC}': 'DDS_noLC' with the pulp chamber filled with composite (non-vital tooth); ₅'IDS_ctrl': C-SE2 LC, flowable composite, sandblasting, etching, C-SE2 (non-LC), AL; ₆'IDS_sal': 'IDS_ctrl' but saliva storage before AL; ₇'IDS_wat': 'IDS_{non_contaminated}' but water storage before AL; ₈'IDS_prov': 'IDS_ctrl' but IDS covered with temporary, saliva storage before AL. After one-week water immersion, half of the specimens were cut for immediate µTBS testing and the other half submitted to 1,200,000 chewing cycles, cut into µ-specimens and submitted to 10,000 thermal cycles prior to µTBS testing. Linear mixed-effects statistics were applied (α = 0.05).

All four IDS and the two DDS approaches that involved separate adhesive light-curing, resulted in reliable immediate and aging-resistant bonding effectiveness to dentin. Using DDS, all µ-specimens failed prior to testing when the adhesive was not separately light-cured prior to luting onto vital dentin. When luted onto non-vital dentin, significantly higher µTBS was recorded that nevertheless remained significantly below that measured for the four IDS and two DDS approaches.

No difference in adhesive luting effectiveness was recorded between IDS and DDS when the adhesive was separately light-cured at the dentin side prior to luting.