Influence of dentin depth on the bond strength of dual-cure self-etching resin cements

This study evaluated the microshear bond strength (μSBS) and failure modes of dual-cure self-etching resin cements to superficial and deep dentin after storage times of 24 hours or 12 months. Thirty sound human third molars were sectioned to create a total of 60 dentin slices (2.0 mm thick), which were randomly assigned to each resin luting agent (RelyX U200, Panavia F 2.0, or Panavia V5) and storage period (n = 10 per agent per storage period). In each luting agent group, resin cement cylinders (0.8 mm in diameter × 1 mm in height) were bonded to both superficial and deep dentin and tested for μSBS after 24 hours or 12 months of storage. The μSBS data were analyzed using a generalized linear model, and failure mode data were evaluated using Fisher exact test (α = 5%). Panavia V5 exhibited significantly greater bond strength than RelyX U200 at both dentin depths and timepoints (P < 0.05). Panavia V5 also showed greater bond strength than Panavia F 2.0 (P < 0.05), except for in deep dentin at 12 months. RelyX U200 demonstrated significantly more premature failures than the other materials (P < 0.05), with the rate of premature failures reaching as high as 85.0% of specimens in deep dentin at 12 months. In deep dentin at 24 hours and superficial dentin at 12 months, there were significant associations between failure type and cement (P < 0.05), with adhesive failures predominating across all cements. Only Panavia V5 showed cohesive failures within dentin (23.5%) after 12 months in deep dentin. Panavia V5 demonstrated superior bond strength to both superficial and deep dentin, maintaining greater bond durability over time compared with RelyX U200 and Panavia F 2.0.